Rotating electric machine

The rotating electric machine includes a stator having a stator winding and a rotor facing the stator in a radial direction. The rotor includes a carrier having a disk-shaped end plate section fixed to a rotating shaft and arranged coaxially with the rotating shaft, and an annular magnet unit arranged coaxially with the rotating shaft. The magnet has a cylindrical magnet holder whose one end in an axial direction is fixed to the end plate section, and a magnet fixed to a peripheral surface on a stator side in the radial direction in the magnet holder and having an alternating polarity in a circumferential direction. The magnet holder is made of a non-magnetic material. In the magnet, an orientation of an axis of easy magnetization on a q-axis is deviated from an orientation parallel to the q-axis.

CROSS REFERENCE TO RELATED APPLICATION

This application is the U.S. bypass application of International Application No. PCT/JP2020/006902 filed on Feb. 20, 2020, which designated the U.S. and claims priority to Japanese Patent Application No. 2019-032182, filed Feb. 25, 2019, the contents of both of these are incorporated herein by reference.

BACKGROUND

Technical Field

The present disclosure in this specification relates to a rotating electric machine including a stator having a stator winding and a rotor facing the stator in a radial direction.

Description of the Related Art

As a conventional rotating electric machine, an outer rotor type rotating electric machine including a cylindrical section, a cylindrical yoke fixed to the inner peripheral surface of the cylindrical section, and an annular magnet fixed to the inner peripheral surface of the yoke is known.

SUMMARY

The present disclosure has been made in view of the above circumstances and provides a rotating electric machine capable of reducing the weight of a rotor.

The disclosed aspects herein employ different technical means. The features, and effects disclosed herein will be made clearer by reference to the subsequent detailed description and accompanying drawings.

First means is a rotating electric machine including a stator having a stator winding, and a rotor facing the stator in a radial direction. The rotor includes a carrier having a disk-shaped end plate section fixed to a rotating shaft and arranged coaxially with the rotating shaft, and an annular magnet unit arranged coaxially with the rotating shaft. The magnet unit includes a cylindrical magnet holder of which one end in an axial direction is fixed to the end plate section, and a magnet fixed to a peripheral surface on a stator side in the radial direction in the magnet holder and having an alternating polarity in a circumferential direction. The magnet holder is made of a non-magnetic material. In the magnet, an orientation of an axis of easy magnetization on a q-axis is deviated from an orientation parallel to the q-axis.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

As seen in Japanese patent literature, JP 2017-195690 A, as the rotating electric machine of this type, an outer rotor type rotating electric machine including a cylindrical section, a cylindrical yoke fixed to the inner peripheral surface of the cylindrical section, and an annular magnet fixed to the inner peripheral surface of the yoke is known.

In the rotating electric machine described in JP 2017-195690 A, the cylindrical section is made of a non-magnetic material such as resin. With this, the weight of the rotor is reduced. Meanwhile, the yoke constituting the rotor is made of a magnetic material such as iron. Magnetic materials generally have a higher specific gravity than non-magnetic materials. Therefore, in the rotating electric machine described in JP 2017-195690 A, there is room for improvement in reducing the weight of the rotor. Moreover, there is room for improvement not only in an outer rotor type rotating electric machine but also in an inner rotor type rotating electric machine in order to reduce the weight of the rotor.

Hereinafter, a plurality of embodiments will be described with reference to the drawings. In the plurality of embodiments, functionally and/or structurally corresponding parts and/or associated parts may be designated with the same reference sign or reference signs that are different in the hundreds or higher position. For corresponding and/or associated parts, the description of other embodiments can be referred to.

The rotating electric machine in this embodiment is used, for example, as a vehicle power source. However, the rotating electric machine can be widely used for industrial use, vehicle use, home appliance use, OA equipment use, game machine use, and the like. Note that, in each of the following embodiments, parts that are the same or equivalent to each other are designated by the same reference signs in the drawings, and the description thereof will be incorporated for the parts having the same reference signs.

First Embodiment

A rotating electric machine10according to the present embodiment is a synchronous multi-phase AC motor and has an outer rotor structure (outer rotating structure). The outline of the rotating electric machine10is illustrated inFIGS.1to5.FIG.1is a vertical cross-sectional perspective view of the rotating electric machine10,FIG.2is a vertical cross-sectional view of the rotating electric machine10in a direction along a rotating shaft11,FIG.3is a cross-sectional view of the rotating electric machine10in a direction orthogonal to the rotating shaft11(cross-sectional view taken along a line ofFIG.2),FIG.4is a cross-sectional view illustrating a part ofFIG.3in an enlarged manner, andFIG.5is an exploded view of the rotating electric machine10. Note that, inFIG.3, for convenience of illustration, hatching indicating a cut surface is omitted except for a rotating shaft11. In the following description, the direction in which the rotating shaft11extends is the axial direction, the direction extending radially from the center of the rotating shaft11is the radial direction, and the direction extending circumferentially around the rotating shaft11is the circumferential direction.

The rotating electric machine10includes, substantially, a bearing unit20, a housing30, a rotor40, a stator50, and an inverter unit60. Each of these members is arranged coaxially with the rotating shaft11and is assembled in the axial direction in a predetermined order to form the rotating electric machine10. The rotating electric machine10of the present embodiment has a configuration having a rotor40as a “field magnet and a stator50as an “armature”, and is embodied as a revolving-field type rotating electric machine.

The bearing unit20includes two bearings21and22arranged apart from each other in the axial direction, and a holding member23that holds the bearings21and22. The bearings21and22are, for example, radial ball bearings, each of which has an outer ring25, an inner ring26, and a plurality of balls27arranged between the outer ring25and the inner ring26. The holding member23has a cylindrical shape, and the bearings21and22are assembled radially thereinside. In addition, the rotating shaft11and the rotor40are rotatably supported radially inside the bearings21and22. The bearings21and22constitute a pair of bearings that rotatably support the rotating shaft11.

In the respective bearings21and22, balls27are held by retainers (not illustrated), and the pitch between the balls is maintained in that state. The bearings21and22has sealing members at the upper and lower portions in the axial direction of the retainer, and the inside of the sealing members is filled with nonconductive grease (for example, nonconductive urea grease). Further, the position of the inner ring26is mechanically held by a spacer, and a constant pressure preload that rises in the up-down direction from the inside is applied.

A housing30has a cylindrical peripheral wall31. The peripheral wall31has a first end and a second end facing each other in the axial direction thereof. The peripheral wall31has an end face32at the first end and an opening33at the second end. The opening33is open throughout the second end. A circular hole34is formed in the center of the end face32, and a bearing unit20is fixed by a fixture such as a screw or a rivet in a state of being inserted through the hole34. Further, a hollow cylindrical rotor40and a hollow cylindrical stator50are housed in the housing30, that is, in the internal space partitioned by the peripheral wall31and the end face32. In the present embodiment, the rotating electric machine10is an outer rotor type, and in the housing30, the stator50is arranged radially inside the cylindrical rotor40. The rotor40is cantilevered and supported by the rotating shaft11on the side of the end face32in the axial direction.

The rotor40has a magnet holder41formed in a hollow tubular shape and an annular magnet unit42provided radially inside the magnet holder41. The magnet holder41has a substantially cup shape and has a function as a magnet holding member. The magnet holder41has a cylindrical section43having a cylindrical shape, a fixing section (attachment)44having a cylindrical shape and a diameter smaller than that of the cylindrical section43, and an intermediate section45serving as a part connecting the cylindrical section43and the fixing section44. The magnet unit42is attached to the inner peripheral surface of the cylindrical section43.

Moreover, the magnet holder41is made of a steel plate cold commercial (SPCC) having sufficient mechanical strength, forging steel, carbon fiber reinforced plastic (CFRP), or the like.

The rotating shaft11is inserted through a through hole44aof the fixing section44. The fixing section44is fixed to the rotating shaft11arranged in the through hole44a. That is, the magnet holder41is fixed to the rotating shaft11by the fixing section44. Moreover, the fixing section44is preferably fixed to the rotating shaft11by spline coupling, key coupling, welding, caulking, or the like using a protrusion and a recess. As a result, the rotor40rotates integrally with the rotating shaft11.

Further, bearings21and22of the bearing unit20are assembled radially inside the fixing section44. Since the bearing unit20is fixed to the end face32of the housing30as described above, the rotating shaft11and the rotor40are rotatably supported by the housing30. As a result, the rotor40is rotatable in the housing30.

The rotor40is provided with the fixing section44only on one of the two ends facing in the axial direction, whereby the rotor40is cantilevered and supported by the rotating shaft11. Here, the fixing section44of the rotor40is rotatably supported by the bearings21and22of the bearing unit20at two positions different in the axial direction. In other words, the rotor40is rotatably supported by the two bearings21and22separated in the axial direction at one of the two ends of the magnet holder41facing in the axial direction. Therefore, even if the rotor40is cantilevered and supported by the rotating shaft11, stable rotation of the rotor40can be achieved. In this case, the rotor40is supported by the bearings21and22at a position displaced to one side with respect to the axial center position of the rotor40.

Further, in the bearing unit20, the bearing22near the center of the rotor40(lower side in the figure) and the bearing21on the opposite side (upper side in the figure) have different gap dimensions between the outer ring25and the inner ring26, and the ball27, and for example, the bearing22near the center of the rotor40has a larger gap dimension than that of the bearing21on the opposite side. In this case, even if shaking of the rotor40or vibration due to imbalance caused by component tolerance acts on the bearing unit20on the side closer to the center of the rotor40, the influence of the shake or vibration is well absorbed. Specifically, by increasing the allowance dimension (gap dimension) by preloading the bearing22near the center of the rotor40(lower side of the figure), the vibration generated in the cantilever structure is absorbed by the allowance portion. The preload may be either a fixed position preload or a constant pressure preload. In the case of fixed position preload, both the outer rings25of the bearing21and the bearing22are joined to the holding member23by a method such as press fitting or adhesion. Further, both the inner rings26of the bearing21and the bearing22are joined to the rotating shaft11by a method such as press fitting or adhesion. Here, the preload can be generated by arranging the outer ring25of the bearing21at a different position in the axial direction with respect to the inner ring26of the bearing21. The preload can also be generated by arranging the outer ring25of the bearing22at a different position in the axial direction with respect to the inner ring26of the bearing22.

Further, in a case where a constant pressure preload is adopted, a preload spring, for example, a waved washer24or the like is arranged in the same region sandwiched between the bearing22and the bearing21in such a manner that preload is generated from the region sandwiched between the bearing22and the bearing21toward the outer ring25of the bearing22in the axial direction. Also in this case, both the inner rings26of the bearing21and the bearing22are joined to the rotating shaft11by a method such as press fitting or adhesion. The bearing21or the outer ring25of the bearing22is arranged with respect to the holding member23via a predetermined clearance. With such a configuration, the spring force of the preload spring acts on the outer ring25of the bearing22in the direction away from the bearing21. Then, when this force is transmitted through the rotating shaft11, a force that presses the inner ring26of the bearing21in the direction of the bearing22acts. As a result, the positions of the outer ring25and the inner ring26in the axial direction of both the bearings21and22are displaced, and the two bearings can be preloaded in the same manner as the aforementioned fixed position preload.

Moreover, when generating the constant pressure preload, it is not always necessary to apply the spring force to the outer ring25of the bearing22as illustrated inFIG.2. For example, the spring force may be applied to the outer ring25of the bearing21. Further, the inner ring26of either of the bearings21and22may be arranged with respect to the rotating shaft11via a predetermined clearance, and the outer ring25of the bearings21and22may be joined to the holding member23by press fitting or adhesion, thereby preloading the two bearings.

Furthermore, in a case where a force is applied in such a manner that the inner ring26of the bearing21is separated from the bearing22, it is better to apply a force in such a manner that the inner ring26of the bearing22is also separated from the bearing21. On the contrary, in a case where a force is applied in such a manner that the inner ring26of the bearing21approaches the bearing22, it is better to apply a force in such a manner that the inner ring26of the bearing22also approaches the bearing21.

Moreover, in a case where the rotating electric machine10is applied to a vehicle for the purpose of a vehicle power source or the like, there is a possibility that vibration having a component in the preload generation direction is applied to a mechanism that generates the preload, and the direction of gravity applied to an object to which the preload is applied may fluctuate. Therefore, in the case where the rotating electric machine10is applied to a vehicle, it is desirable to adopt a fixed position preload.

Further, the intermediate section45has an annular inner shoulder section49aand an annular outer shoulder section49b. The outer shoulder section49bis located outside the inner shoulder section49ain the radial direction of the intermediate section45. The inner shoulder section49aand the outer shoulder section49bare separated from each other in the axial direction of the intermediate section45. As a result, the cylindrical section43and the fixing section44partially overlap in the radial direction of the intermediate section45. That is, the cylindrical section43protrudes outward in the axial direction from the base end portion (back side end portion on the lower side in the figure) of the fixing section44. In this configuration, the rotor40can be supported with respect to the rotating shaft11at a position near the center of gravity of the rotor40, as compared with a case where the intermediate section45is provided in a flat plate shape without a step, and the operational stability of the rotor40can be achieved.

According to the configuration of the intermediate section45described above, in the rotor40, a bearing housing recess46that houses a part of the bearing unit20is formed in an annular shape at a position that surrounds the fixing section44in the radial direction and is inward of the intermediate section45, and a coil housing recess47that houses the coil end54of the stator winding51of the stator50which will be described below is formed at a position that surrounds the bearing housing recess46in the radial direction and is outward of the intermediate section45. In addition, these respective housing recesses46and47are arranged so as to be adjacent to each other inside and outside in the radial direction. That is, a part of the bearing unit20and the coil end54of the stator winding51are arranged so as to overlap inside and outside in the radial direction. This makes it possible to shorten the axial length dimension in the rotating electric machine10.

The intermediate section45is provided so as to project radially outward from the rotating shaft11side. In addition, the intermediate section45is provided with a contact avoiding section that extends in the axial direction and avoids contact of the stator winding51of the stator50with respect to the coil end54. The intermediate section45corresponds to a projecting section.

By bending the coil end54inward or outward in the radial direction, the axial dimension of the coil end54can be reduced, and the axial length of the stator50can be shortened. The bending direction of the coil end54may be in consideration of assembly with the rotor40. Assuming that the stator50is assembled radially inside the rotor40, the coil end54may be preferably bent radially inside on the insertion tip side with respect to the rotor40. The bending direction of the coil end on the side opposite to the coil end54may be arbitrary, but a shape in which the coil end is bent outward with a sufficient space is preferable in manufacturing.

Further, the magnet unit42as a magnet section is composed of a plurality of permanent magnets that are arranged on the radial inside of the cylindrical section43in such a manner that the polarities alternate along the circumferential direction. As a result, the magnet unit42has a plurality of magnetic poles in the circumferential direction. However, the details of the magnet unit42will be described below.

The stator50is provided radially inside the rotor40. The stator50has a stator winding51formed by winding in a substantially tubular shape (annular shape) and a stator core52as a base member arranged radially inside the stator winding51. The stator winding51is arranged so as to face the annular magnet unit42with a predetermined air gap therebetween. The stator winding51is composed of a plurality of phase windings. Each of these phase windings is configured by connecting a plurality of conductors arranged in the circumferential direction to each other at a predetermined pitch. In the present embodiment, a U-phase, V-phase, and W-phase three-phase winding and an X-phase, Y-phase, and Z-phase three-phase winding are used. Two of these three-phase windings are used, and the stator winding51is thereby configured as a six-phase winding.

The stator core52is formed in an annular shape by laminated steel sheets in which electromagnetic steel sheets which are soft magnetic materials are laminated, and is assembled radially inside the stator winding51. The electromagnetic steel sheet is, for example, a silicon steel sheet in which approximately several % (for example, 3%) of silicon is added to iron. The stator winding51corresponds to an armature winding, and the stator core52corresponds to an armature core.

The stator winding51is a portion that overlaps the stator core52in the radial direction, and has a coil side section53that is radially outside the stator core52, and coil ends54and55that respectively project to one end side and to the other end side of the stator core52in the axial direction. The coil side section53faces the stator core52and the magnet unit42of the rotor40in the radial direction, respectively. In a state where the stator50is arranged inside the rotor40, the coil end54on the side of the bearing unit20(upper side in the figure) of the coil ends54and55on both sides in the axial direction is housed in the in the coil housing recess47formed by the magnet holder41of the rotor40. Note that, the details of the stator50will be described below.

The inverter unit60has a unit base61fixed to the housing30by fasteners such as bolts, and a plurality of electric components62assembled to the unit base61. The unit base61is made of, for example, carbon fiber reinforced plastic (CFRP). The unit base61has an end plate63fixed to the edge of the opening33of the housing30, and a casing64integrally provided with the end plate63and extending in the axial direction. The end plate63has a circular opening65at the center thereof, and the casing64is formed so as to stand up from the peripheral edge portion of the opening65.

The stator50is assembled on the outer peripheral surface of the casing64. That is, the outer diameter dimension of the casing64is the same as the inner diameter dimension of the stator core52, or slightly smaller than the inner diameter dimension of the stator core52. By assembling the stator core52to the outside of the casing64, the stator50and the unit base61are integrated. Further, since the unit base61is fixed to the housing30, the stator50is integrated with the housing30in a state where the stator core52is assembled to the casing64.

Moreover, the stator core52is preferably assembled to the unit base61by adhesion, shrink fitting, press fitting, or the like. As a result, the displacement of the stator core52in the circumferential direction or the axial direction with respect to the unit base61side is suppressed.

Further, the radial inside of the casing64is a housing space for housing the electric component62, and the electric component62is arranged in the housing space so as to surround the rotating shaft11. The casing64has a role as a housing space forming section. The electric component62includes a semiconductor module66constituting an inverter circuit, a control board67, and a capacitor module68.

Moreover, the unit base61is provided radially inside the stator50and corresponds to a stator holder (armature holder) that holds the stator50. The housing30and the unit base61constitute the motor housing of the rotating electric machine10. In this motor housing, the holding member23is fixed to the housing30on one side in the axial direction with the rotor40therebetween, and the housing30and the unit base61are coupled to each other on the other side. For example, in a motor vehicle or the like which is an electric car, the rotating electric machine10is mounted to the motor car or the like by attaching a motor housing to the side of the motor car or the like.

Here, the configuration of the inverter unit60will be further described with reference toFIG.6which is an exploded view of the inverter unit60, in addition toFIGS.1to5described above.

In the unit base61, the casing64has a tubular section71and an end face72provided on one (end on the bearing unit20side) of both ends facing each other in the axial direction thereof. Of the both ends of the tubular section71in the axial direction, the side opposite to the end face72is completely opened through the opening65of the end plate63. A circular hole73is formed in the center of the end face72, and the rotating shaft11can be inserted into the hole73. The hole73is provided with a sealing material171that seals the space between the hole73and the outer peripheral surface of the rotating shaft11. The sealing material171is preferably, for example, a sliding seal made of a resin material.

The tubular section71of the casing64is a partition section that partitions between the rotor40and the stator50arranged radially outside and the electric component62arranged radially inside. The rotor40, the stator50, and the electric component62are arranged side by side radially inside and outside with the tubular section71therebetween.

Further, the electric component62is an electric component constituting an inverter circuit, and has a power running function of passing a current through each phase winding of the stator winding51in a predetermined order to rotate the rotor40and a power generation function of inputting a three-phase AC current flowing through the stator winding51with the rotation of the rotating shaft11and outputting same to the outside as generated power. Moreover, the electric component62may have only one of the power running function and the power generation function. The power generation function is, for example, a regenerative function that outputs regenerative power to the outside when the rotating electric machine10is used as a power source for a vehicle.

As a specific configuration of the electric component62, as illustrated inFIG.4, a hollow cylindrical capacitor module68is provided around the rotating shaft11, and a plurality of semiconductor modules66are arranged side by side in the circumferential direction on the outer peripheral surface of the capacitor module68. The capacitor module68includes a plurality of smoothing capacitors68aconnected in parallel to each other. Specifically, the capacitor68ais a laminated film capacitor in which a plurality of film capacitors are laminated, and has a trapezoidal cross section. The capacitor module68is configured by arranging twelve capacitors68aside by side in an annular shape.

Moreover, in the manufacturing process of the capacitor68a, for example, a long film having a predetermined width in which a plurality of films are laminated is used, the film width direction is the trapezoid height direction, and the long film is cut into an isosceles trapezoid shape in such a manner that the upper bottom and the lower bottom of the trapezoid alternate, thereby making a capacitor element. Then, the capacitor68ais manufactured by attaching an electrode or the like to the capacitor element.

The semiconductor module66has a semiconductor switching element such as a MOSFET or an IGBT, and is formed in a substantially plate shape. In the present embodiment, since the rotating electric machine10includes two sets of three-phase windings and an inverter circuit is provided for each of the three-phase windings, a semiconductor module group66A formed by arranging a total of 12 semiconductor modules66in an annular shape is provided in the electric component62.

The semiconductor module66is arranged in a state of being sandwiched between the tubular section71of the casing64and the capacitor module68. The outer peripheral surface of the semiconductor module group66A is in contact with the inner peripheral surface of the tubular section71, and the inner peripheral surface of the semiconductor module group66A is in contact with the outer peripheral surface of the capacitor module68. In this case, the heat generated in the semiconductor module66is transferred to the end plate63via the casing64and released from the end plate63.

The semiconductor module group66A preferably has a spacer69between the semiconductor module66and the tubular section71on the outer peripheral surface side, that is, in the radial direction. In this case, in the capacitor module68, the cross-sectional shape of the cross section orthogonal to the axial direction is a regular dodecagon, whereas the cross-sectional shape of the inner peripheral surface of the tubular section71is circular. Thus, the inner peripheral surface of the spacer69is a flat surface and the outer peripheral surface of the spacer69is a curved surface. The spacer69may be integrally provided so as to be connected in an annular shape on the radial outside of the semiconductor module group66A. The spacer69is a good thermal conductor, and is preferably, for example, a metal such as aluminum, a heat radiating gel sheet, or the like. Moreover, it is also possible to make the cross-sectional shape of the inner peripheral surface of the tubular section71the same dodecagon as that of the capacitor module68. In this case, it is preferable that both the inner peripheral surface and the outer peripheral surface of the spacer69are flat surfaces.

Further, in the present embodiment, a cooling water passage74for flowing cooling water is formed in the tubular section71of the casing64, and the heat generated in the semiconductor module66is also released to the cooling water flowing through the cooling water passage74. That is, the casing64is provided with a water-cooling mechanism. As illustrated inFIGS.3and4, the cooling water passage74is formed in an annular shape so as to surround the electric component62(the semiconductor module66and the capacitor module68). The semiconductor module66is arranged along the inner peripheral surface of the tubular section71, and the cooling water passage74is provided at a position overlapping the semiconductor module66inside and outside in the radial direction.

Since the stator50is arranged on the outside of the tubular section71and the electric component62is arranged on the inside of the tubular section71, the heat of the stator50is transferred to the tubular section71from the outside, and the heat of the electric component62(for example, the heat of the semiconductor module66) is transferred from the inside. In this case, the stator50and the semiconductor module66can be cooled at the same time, and the heat of the heat-generating member in the rotating electric machine10can be efficiently released.

Furthermore, at least a part of the semiconductor module66constituting a part or the whole of the inverter circuit that operates the rotating electric machine by energizing the stator winding51is arranged in a region surrounded by the stator core52arranged radially outside the tubular section71of the casing64. Preferably, the entire one semiconductor module66is arranged in a region surrounded by the stator core52. Furthermore, preferably, the whole of all the semiconductor modules66is arranged in a region surrounded by the stator core52.

Further, at least a part of the semiconductor module66is arranged in a region surrounded by the cooling water passage74. Preferably, the whole of all the semiconductor modules66is arranged in a region surrounded by a yoke141.

Further, the electric component62includes an insulating sheet75provided on one end face of the capacitor module68and a wiring module76provided on the other end face in the axial direction. In this case, the capacitor module68has two end faces facing each other in the axial direction, that is, a first end face and a second end face. The first end face of the capacitor module68near the bearing unit20faces the end face72of the casing64, and is superimposed on the end face72with the insulating sheet75sandwiched therebetween. Further, a wiring module76is assembled on the second end face of the capacitor module68near the opening65.

The wiring module76has a main body section76amade of a synthetic resin material and having a circular plate shape and a plurality of bus bars76b,76cembedded therein, and the bus bars76b,76cform an electrical connection with the semiconductor module66and the capacitor module68. Specifically, the semiconductor module66has a connecting pin66aextending from its axial end face, and the connecting pin66ais connected to the busbar76bon the radial outside of the main body section76a. Further, a busbar76cextends to the side opposite to the capacitor module68on the radial outside of the main body section76a, and is connected to a wiring member79at the tip end portion thereof (seeFIG.2).

As described above, according to the configuration in which the insulating sheet75is provided on the first end face of the capacitor module68facing the axial direction and the wiring module76is provided on the second end face of the capacitor module68, as a heat dissipation path of the capacitor module68, a path from the first end face and the second end face of the capacitor module68to the end face72and the tubular section71is formed. In other words, a path from the first end face to the end face72and a path from the second end face to the tubular section71are formed. As a result, heat can be dissipated from the end face portion of the capacitor module68other than the outer peripheral surface on which the semiconductor module66is provided. That is, not only heat dissipation in the radial direction but also heat dissipation in the axial direction is possible.

Further, since the capacitor module68has a hollow cylindrical shape and the rotating shaft11is arranged on the inner peripheral portion thereof with a predetermined gap interposed therebetween, the heat of the capacitor module68can be released from the hollow portion as well. In this case, the rotation of the rotating shaft11causes an air flow to enhance the cooling effect.

A disk-shaped control board67is attached to the wiring module76. The control board67has a printed circuit board (PCB) on which a predetermined wiring pattern is formed, and a control device77corresponding to a control unit composed of various ICs and a microcomputer is mounted on the board. The control board67is fixed to the wiring module76by a fixture such as a screw. The control board67has, in the central portion thereof, an insertion hole67ain which the rotation shaft11is inserted.

Moreover, the wiring module76has a first surface and a second surface that face each other in the axial direction, that is, face each other in the thickness direction thereof. The first surface faces the capacitor module68. The wiring module76is provided with the control board67on the second surface thereof. The busbar76cof the wiring module76extends from one side of both sides of the control board67to the other side. In such a configuration, the control board67is preferably provided with a notch to avoid interference with the busbar76c. For example, a part of the outer edge portion of the control board67having a circular shape is preferably notched.

As described above, according to the configuration in which the electric component62is housed in the space surrounded by the casing64, and the housing30, the rotor40and the stator50are provided in layers on the outside thereof, the electromagnetic noise generated in the inverter circuit is suitably shielded. In other words, in the inverter circuit, switching control is performed in each semiconductor module66by utilizing PWM control using a predetermined carrier frequency, and it is conceivable that electromagnetic noise is generated by the switching control. However, the noise can be suitably shielded by the housing30, the rotor40, the stator50, and the like on the radially outside the electric component62.

Furthermore, at least a part of the semiconductor module66is arranged in the region surrounded by the stator core52arranged radially outside the tubular section71of the casing64. Thus, compared to a configuration in which the semiconductor module66and the stator winding51are arranged without the stator core52, even if magnetic flux is generated from the semiconductor module66, the stator winding51is less likely to be affected. Further, even if the magnetic flux is generated from the stator winding51, it is unlikely to affect the semiconductor module66. Moreover, it is more effective if the entire semiconductor module66is arranged in a region surrounded by the stator core52arranged radially outside the tubular section71of the casing64. Further, in a case where at least a part of the semiconductor module66is surrounded by the cooling water passage74, it is possible to obtain the effect that the heat generated from the stator winding51and the magnet unit42is suppressed from reaching the semiconductor module66.

In the tubular section71, a through hole78is formed in the vicinity of the end plate63, through which the wiring member79(seeFIG.2) that electrically connects the outer stator50and the inner electric component62is inserted. As illustrated inFIG.2, the wiring member79is connected to the end of the stator winding51and the busbar76cof the wiring module76by crimping, welding, or the like, respectively. The wiring member79is, for example, a busbar, and it is desirable that the joint surface thereof be flattened. The through holes78are preferably provided at one place or a plurality of places, and in the present embodiment, the through holes78are provided at two places. In the configuration in which the through holes78are provided at two places, the winding terminals extending from the two sets of three-phase windings can be easily connected by the wiring members79respectively, which is suitable for performing multi-phase connection.

As described above, as illustrated inFIG.4, the rotor40and the stator50are provided in the housing30in this order from the outside in the radial direction, and an inverter unit60is provided radially inside the stator50. Here, when the radius of the inner peripheral surface of the housing30is d, the rotor40and the stator50are arranged radially outside the distance of d*0.705 from the center of rotation of the rotor40. In this case, when the region of the rotor40and the stator50, that is radially inside from the inner peripheral surface of the stator50that is inside in the radial direction (that is, the inner peripheral surface of the stator core52) is a first region X1, and the region between the inner peripheral surface of the stator50and the housing30is a second region X2, the cross-sectional area of the first region X1is larger than the cross-sectional area of the second region X2. Further, the volume of the first region X1is larger than the volume of the second region X2when viewed in the radial direction in the range where the magnet unit42of the rotor40and the stator winding51overlap.

Moreover, when the rotor40and the stator50are a magnetic circuit component assembly, in the housing30, the first region X1radially inside from the inner peripheral surface of the magnetic circuit component assembly has a larger volume than that of the second region X2between the inner peripheral surface of the magnetic circuit component assembly and the housing30in the radial direction.

Next, the configurations of the rotor40and the stator50will be described in more detail.

Generally, as a structure of a stator in a rotating electric machine, a structure is known in which a stator core made of a laminated steel sheet and forming an annular shape is provided with a plurality of slots in the circumferential direction, and a stator winding is wound in the slots. Specifically, the stator core has a plurality of teeth extending in the radial direction from a yoke at predetermined intervals, and slots are formed between the teeth adjacent to each other in the circumferential direction. In addition, for example, a plurality of layers of conductors are housed in the slots in the radial direction, and the stator winding is composed of the conductors.

However, in the above-mentioned stator structure, when the stator winding is energized, magnetic saturation occurs in the teeth portion of the stator core as the magnetomotive force of the stator winding increases, which may limit the torque density of the rotating electric machine. That is, in the stator core, it is considered that magnetic saturation occurs when the rotating magnetic flux generated by the energization of the stator winding is concentrated on the teeth.

Further, generally, as a configuration of an IPM (Interior Permanent Magnet) rotor in a rotating electric machine, a permanent magnet is arranged on the d-axis in the d-q coordinate system and a rotor core is arranged on the q-axis. In such a case, the stator winding near the d-axis is excited, and thus the exciting magnetic flux flows from the stator to the q-axis of the rotor according to Fleming's law. It is considered that this causes a wide range of magnetic saturation in the q-axis core portion of the rotor.

FIG.7is a torque line diagram illustrating a relation between an ampere-turn [AT] indicating the magnetomotive force of a stator winding and a torque density [Nm/L]. The broken line indicates the characteristics of a general IPM rotor type rotating electric machine. As illustrated inFIG.7, in a general rotating electric machine, by increasing the magnetomotive force in the stator, magnetic saturation occurs in two places, the teeth portion between the slots and the q-axis core portion, which limits the increase in torque. As described above, in the general rotating electric machine, the ampere-turn design value is limited by A1.

Accordingly, in the present embodiment, in order to eliminate the limitation caused by magnetic saturation, the rotating electric machine10is provided with the following configuration. In other words, as a first measure, in order to eliminate the magnetic saturation that occurs in the teeth of the stator core in the stator, a slotless structure is adopted in the stator50, and in order to eliminate the magnetic saturation that occurs in the q-axis core portion of the IPM rotor, an SPM (Surface Permanent Magnet) rotor is adopted. According to the first measure, it is possible to eliminate the above-mentioned two parts where magnetic saturation occurs, but it is considered that the torque in the low current region is reduced (see the alternate long and short dash line inFIG.7). Therefore, as a second measure, in order to recover the torque decrease by increasing the magnetic flux of the SPM rotor, in the magnet unit42of the rotor40, a polar anisotropic structure in which the magnet magnetic path is lengthened to increase the magnetic force is adopted.

Further, as a third measure, in the coil side section53of the stator winding51, a flat conductor structure in which the radial thickness of the stator50of the conductor is reduced is adopted to recover the torque decrease. Here, it is conceivable that a larger eddy current is generated in the stator winding51facing the magnet unit42due to the above-mentioned polar anisotropic structure in which the magnetic force is increased. However, according to the third measure, since the flat conductor structure is thin in the radial direction, it is possible to suppress the generation of eddy current in the radial direction in the stator winding51. As described above, according to each of these first to third configurations, as illustrated by the solid line inFIG.7, by adopting a magnet with a high magnetic force, it is expected that the torque characteristics will be significantly improved, and at the same time, the concern about the generation of a large eddy current that may occur due to the magnet with a high magnetic force also can be improved.

Furthermore, as a fourth measure, a magnet unit having a magnetic flux density distribution close to a sine wave is adopted by utilizing a polar anisotropic structure. According to this, the sine wave matching rate can be increased by pulse control or the like described below to increase the torque, and since the magnetic flux changes more slowly than the radial magnet, the eddy current loss (copper loss due to eddy current: eddy current loss) can also be further suppressed.

Hereinafter, the sine wave matching rate will be described. The sine wave matching rate can be obtained by comparing the measured waveform of the surface magnetic flux density distribution measured by tracing the surface of the magnet with a magnetic flux probe and the sine wave having the same period and peak value. In addition, the ratio of the amplitude of the primary waveform, which is the fundamental wave of the rotating electric machine, to the amplitude of the actually measured waveform, that is, the amplitude of the fundamental wave plus other higher harmonic components, corresponds to the sine wave matching rate. As the sine wave matching rate increases, the waveform of the surface magnetic flux density distribution approaches a sine wave shape. In addition, when a primary sine wave current is supplied from the inverter to a rotating electric machine equipped with a magnet having an improved sine wave matching rate, the waveform of the surface magnetic flux density distribution of the magnet is close to the sine wave shape, and correlatively, can generate a large torque. Moreover, the surface magnetic flux density distribution may be estimated by a method other than an actual measurement, for example, an electromagnetic field analysis using Maxwell's equations.

Further, as a fifth measure, the stator winding51has a wire conductor structure in which a plurality of wires are gathered and bundled. According to this, since the wires are connected in parallel, a large current can flow, and the cross-sectional area of each wire is small, the eddy current generated by the conductors that spread in the circumferential direction of the stator50in the flat conductor structure can be suppressed more effectively than thinning in the radial direction by the third measure. In addition, by forming a structure in which a plurality of wires are twisted together, for the magnetomotive force from the conductor, it is possible to cancel the eddy current with respect to the magnetic flux generated by the right-handed screw rule in the current energizing direction.

In this way, if the fourth and fifth measures are further added, the torque can be increased while adopting the second measure, a magnet with a high magnetic force, while suppressing the eddy current loss caused by the high magnetic force.

Hereinafter, the slotless structure of the stator50described above, the flat conductor structure of the stator winding51, and the polar anisotropic structure of the magnet unit42will be individually described. Here, first, the slotless structure of the stator50and the flat conductor structure of the stator winding51will be described.FIG.8is a cross-sectional view of the rotor40and the stator50, andFIG.9is a view illustrating a part of the rotor40and the stator50illustrated inFIG.8in an enlarged manner.FIG.10is a cross-sectional view illustrating a cross section of the stator50along a line X-X ofFIG.11, andFIG.11is a cross-sectional view illustrating a vertical cross section of the stator50. Further,FIG.12is a perspective view of the stator winding51. Note thatFIGS.8and9illustrate the magnetization direction of the magnet in the magnet unit42with arrows.

As illustrated inFIGS.8to11, the stator core52has a cylindrical shape in which a plurality of electromagnetic steel sheets are laminated in the axial direction and has a predetermined thickness in the radial direction, and the stator winding51is assembled on the radially outside that is the rotor40side. In the stator core52, the outer peripheral surface on the rotor40side is a conductor installation section (conductor area). The outer peripheral surface of the stator core52has a curved surface without unevenness, and a plurality of conductor groups81are arranged at predetermined intervals in the circumferential direction on the outer peripheral surface thereof. The stator core52functions as a back yoke that is a part of a magnetic circuit for rotating the rotor40. In this case, teeth (that is, an iron core) made of a soft magnetic material are not provided between each of the two conductor groups81adjacent to each other in the circumferential direction (that is, a slotless structure). In the present embodiment, the resin material of the sealing member57is inserted into a void56of each of the conductor groups81. That is, in the stator50, the interconductor member provided between the respective conductor groups81in the circumferential direction is configured as the sealing member57which is a non-magnetic material. In a state before sealing of the sealing member57, on the outer side of the stator core52in the radial direction, the conductor groups81are respectively arranged at predetermined intervals in the circumferential direction with the void56, which is an inter-conductor region, interposed therebetween. As a result, the stator50having a slotless structure is constructed. In other words, each conductor group81is composed of two conductors (conductor)82described below, and only a non-magnetic material occupies a region between the two conductor groups81adjacent to each other in the circumferential direction of the stator50. The non-magnetic material includes a non-magnetic gas such as air, a non-magnetic liquid, and the like in addition to the sealing member57. Moreover, in the following, the sealing member57is also referred to as an inter-conductor member (conductor-to-conductor member).

Moreover, a configuration in which the teeth are provided between the conductor groups81arranged in the circumferential direction is considered to be a configuration in which the teeth have a predetermined thickness in the radial direction and a predetermined width in the circumferential direction, and thus a part of a magnetic circuit, that is, a magnet magnetic path is formed between the conductor groups81. In this respect, it can be said that a configuration in which the teeth are not provided between the respective conductor groups81is a configuration in which the above-mentioned magnetic circuit is not formed.

As illustrated inFIG.10, the stator winding (i.e., armature winding)51is formed so as to have a predetermined thickness T2(hereinafter, also referred to as a first dimension) and a width W2(hereinafter, also referred to as a second dimension). The thickness T2is the shortest distance between the outer surface and the inner surface facing each other in the radial direction of the stator winding51. The width W2is the circumferential length of the stator winding51of a part of the stator winding51which functions as one of the polyphase of the stator winding51(in the example, three phases: three phases of U phase, V phase and W phase or three phases of X phase, Y phase and Z phase). Specifically, inFIG.10, in a case where two conductor groups81adjacent to each other in the circumferential direction function as one of the three phases, for example, the U phase, the width W2is from one end to the other of the two conductor groups81in the circumferential direction. In addition, the thickness T2is smaller than the width W2.

Moreover, the thickness T2is preferably smaller than the total width dimension of the two conductor groups81existing in the width W2. Further, if the cross-sectional shape of the stator winding51(more specifically, the conductor wire82) is a perfect circle, an ellipse, or a polygon, in the cross sections of the conductor wire82along the radial direction of the stator50, the maximum length in the radial direction of the stator50may be W12, and the maximum length in the circumferential direction of the stator50may be W11.

As illustrated inFIGS.10and11, the stator winding51is sealed by the sealing member57made of a synthetic resin material as a sealing material (molding material). That is, the stator winding51is molded together with the stator core52by the molding material. The resin can be regarded as a non-magnetic substance or an equivalent of the non-magnetic substance as Bs=0.

Looking at the cross section ofFIG.10, the sealing member57is provided between the respective conductor groups81, that is, the void56is filled with the synthetic resin material, and with this sealing member57, an insulating member is interposed between the respective conductor groups81. That is, the sealing member57functions as an insulating member in the void56. The sealing member57is provided on the radial outside of the stator core52in a range including all of the conductor groups81, that is, in a range in which the radial thickness dimension is larger than the radial thickness dimension of each conductor group81.

Further, when viewed in the vertical cross section ofFIG.11, the sealing member57is provided in a range including a turn section84of the stator winding51. Inside the stator winding51in the radial direction, the sealing member57is provided within a range including at least a part of the end faces of the stator core52facing in the axial direction. In this case, the stator winding51is resin-sealed almost entirely except for the ends of the phase winding of each phase, that is, the connection terminals with the inverter circuit.

In the configuration in which the sealing member57is provided in a range including the end face of the stator core52, the laminated steel sheet of the stator core52can be pressed inward in the axial direction by the sealing member57. As a result, the laminated state of each steel sheet can be maintained with the use of the sealing member57. Moreover, in the present embodiment, the inner peripheral surface of the stator core52is not resin-sealed, but instead, the entire stator core52including the inner peripheral surface of the stator core52may be resin-sealed.

In a case where the rotating electric machine10is used as a vehicle power source, the sealing member57is preferably made of a highly heat-resistant fluororesin, epoxy resin, PPS resin, PEEK resin, LCP resin, silicon resin, PAI resin, PI resin, or the like. Further, considering the linear expansion coefficient from the viewpoint of suppressing cracking due to the expansion difference, it is desirable that the material is the same as that of the outer coating of the conductor of the stator winding51. In other words, a silicon resin having a linear expansion coefficient that is generally more than double that of other resins is preferably excluded. Moreover, for electric products that do not have an engine that utilizes combustion, such as electric vehicles, PPO resin, phenol resin, and FRP resin that have heat resistance of approximately 180° C. are also candidates. This does not apply in the field where the ambient temperature of the rotating electric machine is considered to be below 100° C.

The torque of the rotating electric machine10is proportional to the magnitude of the magnetic flux. Here, in a case where the stator core has teeth, the maximum amount of magnetic flux in the stator is limited depending on the saturation magnetic flux density in the teeth, but in a case where the stator core does not have teeth, the maximum amount of magnetic flux in the stator is not limited. Therefore, the configuration is advantageous in increasing the energization current for the stator winding51to increase the torque of the rotating electric machine10.

In the present embodiment, the inductance of the stator50is reduced by using a structure (slotless structure) in which the stator50has no teeth. Specifically, in the stator of a general rotating electric machine in which a conductor is housed in each slot partitioned by a plurality of teeth, the inductance is, for example, around 1 mH, whereas in the stator50of the present embodiment, the inductance is reduced to approximately 5 to 60 μH. In the present embodiment, it is possible to reduce a mechanical time constant Tm by reducing the inductance of the stator50while using the rotating electric machine10having an outer rotor structure. That is, it is possible to reduce the mechanical time constant Tm while increasing the torque. Moreover, when the inertia is J, the inductance is L, the torque constant is Kt, and the counter electromotive force constant is Ke, the mechanical time constant Tm is calculated by the following formula.
Tm=(J*L)/(Kt*Ke)
In this case, it can be confirmed that the mechanical time constant Tm is reduced by reducing the inductance L.

Each conductor group81on the radially outside the stator core52is configured by arranging a plurality of conductor wires82having a flat rectangular cross section side by side in the radial direction of the stator core52. Each conductor wire82is arranged in a direction in such a manner that “radial dimension<circumferential dimension” in the cross section. As a result, the thickness of each conductor group81is reduced in the radial direction. Further, the thickness in the radial direction is reduced, and the conductor region extends flatly to the region where the teeth have been conventionally, forming a flat conductor region structure. As a result, the increase in the amount of heat generated of the conductor, which is a concern because the cross-sectional area becomes smaller due to the thinning, is suppressed by flattening in the circumferential direction and increasing the cross-sectional area of the conductor. Moreover, even if a plurality of conductors are arranged in the circumferential direction and connected in parallel, the conductor cross-sectional area of the conductor coating is reduced, but the effect by the same reason can be obtained. Moreover, in the following, each conductor group81and each conductor wire82will also be referred to as a conductive member.

Since there is no slot, in the stator winding51in the present embodiment, the conductor region occupied by the stator winding51in one circumference in the circumferential direction can be designed to be larger than the conductor non-occupied region which the stator winding51does not occupy. Moreover, in a conventional rotating electric machine for vehicles, it is natural that the conductor region/conductor non-occupied region in one circumference in the circumferential direction of the stator winding is one or less. On the other hand, in the present embodiment, each conductor group81is provided in such a manner that the conductor region is equal to the conductor non-occupied region or the conductor region is larger than the conductor non-occupied region. Here, as illustrated inFIG.10, when the conductor region in which the conductor wire82(that is, a straight section83described below) is arranged in the circumferential direction is WA and the region between the adjacent conductor wires82is WB, the region WA is larger than the interconductor region WB in the circumferential direction.

As a configuration of the conductor group81in the stator winding51, the radial thickness dimension of the conductor group81is smaller than the circumferential width dimension for one phase in one magnetic pole. In other words, a configuration in which the conductor group81is composed of two layers of conductor wires82in the radial direction and two conductor groups81are provided in the circumferential direction for one phase in one magnetic pole fulfills “Tc*2<Wc*2” when the radial thickness dimension of each conductor wire82is Tc, and the circumferential width dimension of each conductor wire82is Wc. Moreover, as another configuration, a configuration in which the conductor group81is composed of two layers of conductor wires82and one conductor group81is provided in the circumferential direction for one phase in one magnetic pole preferably fulfills a relation “Tc*2<Wc”. In short, the conductor section (conductor group81) arranged at predetermined intervals in the circumferential direction in the stator winding51has a radial thickness dimension that is smaller than the circumferential width dimension for one phase in one magnetic pole.

In other words, it is preferable that the radial thickness dimension Tc of each conductor wire82is smaller than the circumferential width dimension Wc. Furthermore, a radial thickness dimension (2Tc) in the radial direction of the conductor group81composed of two layers of conductors82, that is, a radial thickness dimension (2Tc) in the circumferential direction of the conductor group81is preferably smaller than the width dimension Wc.

The torque of the rotating electric machine10is substantially inversely proportional to the radial thickness of the stator core52of the conductor group81. In this regard, the thickness of the conductor group81is reduced on the radial outside of the stator core52, which is advantageous in increasing the torque of the rotating electric machine10. The reason is that the magnetic resistance can be lowered by reducing the distance from the magnet unit42of the rotor40to the stator core52(that is, the distance of the iron-free portion). According to this, the interlinkage magnetic flux of the stator core52by the permanent magnet can be increased, and the torque can be increased.

Further, by reducing the thickness of the conductor group81, even if the magnetic flux leaks from the conductor group81, it is easily collected by the stator core52, and the magnetic flux can be prevented from not being effectively used for improving torque and leaking to the outside. That is, it is possible to suppress a decrease in magnetic force due to magnetic flux leakage, and it is possible to increase the interlinkage magnetic flux of the stator core52by the permanent magnet to increase the torque.

The conductor wire (conductor)82is composed of a coated conductor in which the surface of the conductor (conductor body)82ais coated with an insulating coating82b, and insulation is ensured between the conductor wires82that overlap each other in the radial direction and between the conductor wires82and the stator core52, respectively. This insulating coating82bis composed of a coating if a wire86described below is a self-fusion coated wire, or an insulating member laminated separately from the coating of the wire86. Moreover, each phase winding composed of the conductor wire82retains the insulating property by the insulating coating82bexcept for the exposed portion for connection. The exposed portion is, for example, an input/output terminal portion or a neutral point portion in the case of a star-shaped connection. In the conductor group81, the conductor wires82adjacent to each other in the radial direction are fixed to each other with the use of resin fixing or a self-fusion coated wire. As a result, dielectric breakdown, vibration, and sound due to the friction of the conductor wires82against each other are suppressed.

In the present embodiment, the conductor82ais configured as an aggregate of a plurality of wires (wire)86. Specifically, as illustrated inFIG.13, the conductor82ais formed in a twisted state by twisting a plurality of wires86. Further, as illustrated inFIG.14, the wires86are configured as a composite in which thin fibrous conductive materials87are bundled. For example, the wire86is a composite of CNT (carbon nanotube) fibers, and as the CNT fiber, a fiber containing boron-containing fine fibers in which at least a part of carbon is replaced with boron is used. As the carbon-based fine fiber, a vapor-grown carbon fiber (VGCF) or the like can be used in addition to the CNT fiber, but it is preferable to use the CNT fiber. Moreover, the surface of the wire86is covered with a polymer insulating layer such as enamel. Further, it is preferable that the surface of the wire86is covered with a so-called enamel coating made of a polyimide film or an amide-imide film.

The conductor wire82constitutes an n-phase winding in the stator winding51. In addition, the respective wires86of the conductor wire82(that is, the conductor82a) are adjacent to each other in contact with each other. In the conductor wire82, the winding conductor has a portion formed by twisting the plurality of wires86at one or more places in a phase, and the resistance value among the twisted wires86is larger than the resistance value of each wire86per se. In other words, if each of the two adjacent wires86has a first electrical resistivity in its adjacent direction and each of the wires86has a second electrical resistivity in its length direction, then the first electrical resistivity is larger than the second electrical resistivity. Moreover, the conductor wire82may be formed of the plurality of wires86, and may be an aggregate of wires covering the plurality of wires86by an insulating member having an extremely high first electrical resistivity. Further, the conductor82aof the conductor wire82is composed of a plurality of twisted wires86.

Since the conductor82ais configured by twisting the plurality of wires86, it is possible to suppress the generation of the eddy current in the respective wires86and reduce the eddy current in the conductor82a. Further, since each wire86is twisted, portions where the magnetic field application directions are opposite to each other are generated in one wire86, and the counter electromotive voltage is canceled out. Therefore, the eddy current can also be reduced. In particular, by forming the wire86with the fibrous conductive material87, it is possible to make the wire thinner and to significantly increase the number of twists, and it is possible to more preferably reduce the eddy current.

Moreover, the method for insulating the wires86from each other here is not limited to the above-mentioned polymer insulating film, and may be a method for making it difficult for current to flow between the twisted wires86by utilizing contact resistance. That is, if the resistance value between the twisted wires86is larger than the resistance value of the wire86per se, the above effect can be obtained by the potential difference generated due to the difference in the resistance values. For example, by using the manufacturing equipment for creating the wire86and the manufacturing equipment for making the stator50(armature) of the rotating electric machine10as separate non-continuous equipment, the wire86can be oxidized due to the movement time, work interval, and the like, and the contact resistance can be increased, which is suitable.

As described above, the conductor wires82have a flat rectangular cross section and are arranged side by side in the radial direction, and for example, a plurality of wires86covered with a self-fusion coated wire having a fusion layer and an insulating layer is assembled in a twisted state, and the fusion layers are fused to maintain the shape of the conductor wires82. Moreover, the wires having no fusion layer or the wires with the self-fusion coated wire may be twisted and solidified and molded into a desired shape with a synthetic resin or the like. When the thickness of the insulating coating82bin the conductor wire82is set to, for example, 80 μm to 100 μm and is set to be thicker than the film thickness (5 to 40 μm) of a commonly used conductor, even if an insulating paper or the like is not interposed between the conductor wire82and the stator core52, the insulating property between the two can be ensured.

Further, it is desirable that the insulating coating82bhas higher insulating performance than that of the insulating layer of the wire86and is configured to be able to insulate between phases. For example, when the thickness of the polymer insulating layer of the wire86is set to, for example, approximately 5 μm, it is desirable that the thickness of the insulating coating82bof the conductor wire82is set to approximately 80 μm to 100 μm, and thus insulation between phases can be preferably performed.

Further, the conductor wire82may have a configuration in which a plurality of wires86are bundled without being twisted. That is, the conductor wire82may have any of a configuration in which a plurality of wires86are twisted in the total length, a configuration in which a plurality of wires86are twisted in a part of the total length, and a configuration in which a plurality of wires86are bundled without being twisted anywhere in the total length. In summary, each conductor wire82constituting the conductor section is a wire aggregate in which a plurality of wires86are bundled and the resistance value between the bundled wires is larger than the resistance value of the wire86per se.

Each conductor wire82is bent and formed so as to be arranged in a predetermined arrangement pattern in the circumferential direction of the stator winding51, and as a result, a phase winding for each phase is formed as the stator winding51. As illustrated inFIG.12, in the stator winding51, the coil side section53is formed by the straight section83of each conductor wire82extending linearly in the axial direction, and the coil ends54and55are formed by the turn section84protruding to both outsides from the coil side section53in the axial direction. Each conductor wire82is configured as a series of wave winding-shaped conductors by alternately repeating the straight section83and the turn section84. The straight sections83are arranged at positions facing the magnet unit42in the radial direction, and in-phase straight sections83arranged at positions on the axially outer side of the magnet unit42at predetermined intervals are connected to each other by the turn section84. Note that the straight section83corresponds to a “magnet facing section”.

In the present embodiment, the stator winding51is wound in an annular shape by distributed winding. In this case, in the coil side section53, straight sections83are arranged in the circumferential direction at intervals corresponding to one pole pair of the magnet unit42for each phase, and in the coil ends54and55, the respective straight sections83for each phase are connected to each other by the turn section84formed in a substantially V shape. The directions of the currents of the straight section83that are paired corresponding to one-pole pair are opposite to each other. Further, the combination of the pair of straight sections83connected by the turn section84is different between one coil end54and the other coil end55, and the connections at the coil ends54and55are repeated in the circumferential direction, and thus the stator winding51is formed in a substantially cylindrical shape.

More specifically, the stator winding51constitutes a winding for each phase with the use of two pairs of conductor wires82for each phase, and one three-phase winding (U-phase, V-phase, W-phase) and the other three-phase winding (X-phase, Y-phase, Z-phase) of the stator winding51are provided in two layers inside and outside in the radial direction. In this case, if the number of phases of the stator winding51is S (6 in the case of the example) and the number of conductor wires82per phase is m, then 2*S*m=2Sm conductor wires82will be formed for each pole pair. In the present embodiment, since the number of phases S is 6, the number of m is 4, and an 8-pole pair (16 poles) rotating electric machine is used, 6*4*8=192 conductor wires82are arranged in the circumferential direction of the stator core52.

In the stator winding51illustrated inFIG.12, in the coil side section53, the straight sections83are arranged so as to overlap in two layers adjacent in the radial direction, and in the coil ends54and55, the turn sections84extend in directions opposite to each other in the circumferential direction, from each of the straight sections83overlapping in the radial direction. That is, in the respective conductor wires82adjacent to each other in the radial direction, the directions of the turn sections84are opposite to each other except for the ends of the stator winding51.

Here, the winding structure of the conductor wire82in the stator winding51will be specifically described. In the present embodiment, a plurality of conductor wires82formed by wave winding are provided so as to be stacked in a plurality of layers (for example, two layers) adjacent to each other in the radial direction.FIGS.15(a) and15(b)are diagrams illustrating a form of each conductor wire82in an nth layer,FIG.15(a)illustrates a shape of the conductor wire82seen from the side of the stator winding51, andFIG.15(b)illustrates a shape of the conductor wire82seen from one side in the axial direction of the stator winding51. Moreover, inFIG.15(a)andFIG.15(b), the positions where the conductor group81is arranged are illustrated as D1, D2, D3, . . . , respectively. Further, for convenience of explanation, only three conductor wires82are illustrated, which are referred to as a first conductor82_A, a second conductor82_B, and a third conductor82_C.

In each of the conductors82_A to82_C, the straight sections83are all arranged at the nth layer position, that is, at the same position in the radial direction, and the straight sections83separated from each other by 6 positions (3*m pairs) in the circumferential direction are connected to each other by the turn section84. In other words, in each of the conductors82_A to82_C, on the same circle centered on the shaft center of the rotor40, both ends of the seven straight sections83arranged adjacent to each other in the circumferential direction of the stator winding51are connected to each other by one turn section84. For example, in the first conductor82_A, a pair of straight sections83are arranged at D1and D7, respectively, and the pair of straight sections83are connected to each other by an inverted V-shaped turn section84. Further, the other conductors82_B and82_C are arranged in the same nth layer with their circumferential positions shifted by one. In this case, since the conductors82_A to82_C are all arranged in the same layer, it is conceivable that the turn sections84might interfere with each other. Therefore, in the present embodiment, an interference avoidance section is formed in the turn section84of each of the conductors82_A to82_C with a part thereof offset in the radial direction.

Specifically, the turn section84of each of the conductors82_A to82_C has one tilted portion84awhich is a portion extending in the circumferential direction on the same circle (first circle), a top portion84bthat shifts from the tilted portion84aradially inward (upper side inFIG.15(b)) of the same circle and reaches another circle (second circle), an tilted portion84cthat extends in the circumferential direction on the second circle, and a return portion84dthat returns from the first circle to the second circle. The top portion84b, tilted portion84c, and return portion84dcorrespond to the interference avoidance section. Moreover, the tilted portion84cmay be configured to shift outward in the radial direction with respect to the tilted portion84a.

That is, the turn sections84of the conductors82_A to82_C have a tilted portion84aon one side and a tilted portion84con the other side on both sides of the top portion84bwhich is a central position in the circumferential direction. The radial positions of the tilted portions84aand84c(the position in the front-rear direction of the plane ofFIG.15(a)and the position in the up-down direction inFIG.15(b)) are different from each other. For example, the turn section84of the first conductor82_A extends along the circumferential direction with a D1position of the nth layer as the start point position, bends in the radial direction (for example, inward in the radial direction) at the top portion84bwhich is the central position in the circumferential direction, and then bends again in the circumferential direction, thereby extending along the circumferential direction again, and further bends in the radial direction (for example, outside in the radial direction) again at the return portion84d, thereby reaching a D7position of the nth layer, which is the end point position.

According to the above configuration, in the conductors82_A to82_C, each tilted portion84aon one side is arranged vertically in the order of the first conductor82_A, the second conductor82_B, and the third conductor82_C from the top, and at the top portion84b, the top and bottom of each conductor82_A to82_C are interchanged, and each tilted portion84con the other side is arranged vertically in the order of the third conductor82_C, the second conductor82_B, and the first conductor82_A from the top. Therefore, the respective conductors82_A to82_C can be arranged in the circumferential direction without interfering with each other.

Here, in a configuration in which a plurality of conductor wires82are stacked in the radial direction to form a conductor group81, it is preferable that the turn section84connected to the straight section83on the radially inside and the turn section84connected to the straight section83on the radial outside of the respective straight sections83of the plurality of layers are arranged so as to be radially separated from each of the straight sections83. Further, when the conductor wires82of a plurality of layers are bent to the same side in the radial direction near the end of the turn section84, that is, the boundary portion with the straight section83, it is preferable that the insulating property is not impaired due to the interference between the conductor wires82of the adjacent layers.

For example, in D7to D9ofFIG.15(a)andFIG.15(b), the respective conductor wires82overlapping in the radial direction are respectively bent in the radial direction at the return portion84dof the turn section84. In this case, as illustrated inFIG.16, it is preferable that the radius of curvature of the bent portion is different between the conductor wire82of the nth layer and the conductor wire82of the n+1 layer. Specifically, a radius of curvature R1of the conductor wire82on the radially inside (nth layer) is made smaller than a radius of curvature R2of the conductor wire82on the radially outside (n+1th layer).

Further, it is preferable that the radial shift amount is different between the nth layer conductor wire82and the n+1th layer conductor wire82. Specifically, a shift amount S1of the conductor wire82on the radially inside (nth layer) is made larger than a shift amount S2of the conductor wire82on the radially outside (n+1th layer).

With the above configuration, mutual interference of the respective conductor wires82can be suitably avoided even when the respective conductor wires82overlapping in the radial direction are bent in the same direction. As a result, good insulating properties can be obtained.

Next, the structure of the magnet unit42in the rotor40will be described. In the present embodiment, it is assumed that the magnet unit42is made of a permanent magnet, has a residual magnetic flux density Br=1.0 [T], and has an intrinsic coercive force Hcj=400 [kA/m] or more. In short, the permanent magnet used in this embodiment is a sintered magnet obtained by sintering and solidifying a granular magnetic material, and the intrinsic coercive force Hcj on the J-H curve is 400 [kA/m] or more, and the residual magnetic flux density Br is 1.0 [T] or more. When 5000 to 10000 [AT] is applied by interphase excitation, if a permanent magnet with a length of 25 [mm] is used in the magnetic length of one pole pair, that is, the N pole and the S pole, in other words, the path of the magnetic flux flowing between the N pole and the S pole, then Hcj=10000 [A], indicating that demagnetization is not performed.

In other words, the magnet unit42has a saturation magnetic flux density Js of 1.2 [T] or more, a crystal particle size of 10 [μm] or less, and Js*α of 1.0 [T] or higher when the orientation ratio is α.

The magnet unit42will be supplemented below. The magnet unit42(magnet) is characterized in that 2.15 [T]≥Js≥1.2 [T]. In other words, examples of the magnet used in the magnet unit42include NdFe11TiN, Nd2Fe14B, Sm2Fe17N3, and FeNi magnets having L10 type crystals. Moreover, configurations such as SmCo5 which is usually called samarium-cobalt, FePt, Dy2Fe14B, and CoPt cannot be used. Note that, like the same type of compounds such as Dy2Fe14B and Nd2Fe14B, in some cases, even a magnet that generally uses dysprosium which is a heavy rare earth to have a high coercive force of Dy while slightly losing the high Js characteristics of neodymium fulfills 2.15 [T]≥Js≥1.2 [T], the magnet can be employed in this case as well. In such a case, the magnet is referred to as ([Nd1−xDyx]2Fe14B), for example. Furthermore, the magnet can be achieved by two or more types of magnets having different compositions, for example, magnets made of two or more types of materials such as FeNi plus Sm2Fe17N3, and for example, the magnet can also be achieved by a mixed magnet in which a small amount of Js<1 [T], for example, Dy2Fe14B is mixed with a magnet of Nd2Fe14B having sufficient value of Js, i.e. Js=1.6 [T], and the coercive force is increased.

Further, for rotating electric machines that operate at temperatures outside the range of human activity, for example, 60° C. or higher, which exceeds the temperature of a desert, for example, in vehicle motor applications where the temperature inside the vehicle is close to 80° C. in summer, it is desirable to contain the components of FeNi and Sm2Fe17N3, which have a particularly small temperature dependence coefficient. This is because the motor characteristics differ greatly depending on the temperature dependence coefficient in the motor operation from a temperature state close to −40° C. in Northern Europe, which is within the range of human activity, to 60° C. or higher, which exceeds the desert temperature mentioned above, or to a heat resistant temperature of coil enamel coating approximately 180-240° C., and thus it becomes difficult to perform optimum control with the same motor driver. If the aforementioned FeNi having L10 type crystals, Sm2Fe17N3, or the like is used, the burden on the motor driver can be suitably reduced due to its characteristic of having a temperature dependence coefficient of less than half that of Nd2Fe14B.

Additionally, the magnet unit42is characterized in that the size of the particle diameter in the fine powder state before orientation is 10 μm or less and the single magnetic domain particle diameter or more by using the aforementioned magnet blending. In magnets, the coercive force is increased by miniaturizing the powder particles to the order of several hundred nm. Therefore, in recent years, powder as fine as possible has been used. However, if they are made too fine, the BH product of the magnet will drop due to oxidation or the like, and thus a single magnetic domain particle diameter or larger is preferable. It is known that the coercive force increases by the miniaturization when the particle diameter is up to the single magnetic domain particle diameter. Moreover, the size of the particle diameter that has been described here is the size of the particle diameter in the fine powder state at the time of the orientation process in the magnet manufacturing process.

Furthermore, each of the first magnet91and the second magnet92of the magnet unit42is a sintered magnet formed by so-called sintering, in which magnetic powder is baked and hardened at a high temperature. In this sintering, when the saturation magnetization Js of the magnet unit42is 1.2 T or more, the crystal grain diameter of the first magnet91and the second magnet92is 10 μm or less, and the orientation ratio is α, sintering is performed in such a manner that Js*α fulfills a condition of 1.0 T (tesla) or more. Further, each of the first magnet91and the second magnet92is sintered so as to fulfill the following conditions. In addition, the orientation is performed in the orientation process in the manufacturing process, the orientation ratio is different from the definition of the magnetic force direction by the magnetizing process of the isotropic magnet. With the saturation magnetization Js of the magnet unit42of the present embodiment is 1.2 T or more, a high orientation ratio is set in such a manner that the orientation ratio α of the first magnet91and the second magnet92is Jr≥Js*α≥1.0 [T]. Moreover, the orientation ratio α referred to here is that, in a case where in each of the first magnet91and the second magnet92, for example, there are six axes of easy magnetization, if five of the axes face a direction A10in the same direction and the remaining one faces a direction B10tilted 90 degrees with respect to the direction A10, α=⅚, and if the remaining one faces the direction B10tilted 45 degrees with respect to the direction A10, the component for the remaining one facing the direction A10is cos 45°=0.707, and thus α=(5+0.707)/6. In this example, the first magnet91and the second magnet92are formed by sintering, but if the above conditions are fulfilled, the first magnet91and the second magnet92may be molded by another method. For example, a method for forming an MQ3 magnet or the like can be employed.

In this embodiment, since a permanent magnet whose axis of easy magnetization is controlled by orientation is used, the magnetic circuit length inside the magnet can be made longer than the magnetic circuit length of a linearly oriented magnet that conventionally produces 1.0 [T] or more. That is, the magnetic circuit length per pole pair can be achieved with a small amount of magnets, and the reversible demagnetization range can be maintained even when exposed to harsh high thermal conditions compared to the conventional design using linearly oriented magnets. Further, the discloser of the present application has found a configuration in which characteristics similar to those of a polar anisotropic magnet can be obtained even with the use of a magnet of the prior art.

Note that, the axis of easy magnetization refers to a crystal orientation that is easily magnetized in a magnet. The direction of the axis of easy magnetization in the magnet is a direction in which the orientation ratio indicating the degree to which the directions of the axes of easy magnetization are aligned is 50% or more, or a direction in which the orientation of the magnet is average.

As illustrated inFIGS.8and9, the magnet unit42has an annular shape and is provided inside the magnet holder41(specifically, radially inside the cylindrical section43). The magnet unit42has a first magnet91and a second magnet92, which are respectively polar anisotropic magnets and have different polarities from each other. The first magnet91and the second magnet92are arranged alternately in the circumferential direction. The first magnet91is a magnet that forms an N pole in a portion close to the stator winding51, and the second magnet92is a magnet that forms an S pole in a portion close to the stator winding51. The first magnet91and the second magnet92are permanent magnets made of rare earth magnets such as neodymium magnets.

In each of the magnets91and92, as illustrated inFIG.9, in the known d-q coordinate system, the magnetization direction extends in an arc shape between the d-axis (direct-axis) which is the center of the magnetic pole and the q-axis (quadrature-axis) which is the magnetic pole boundary between the N pole and the S pole (in other words, the magnetic flux density is 0 tesla). In each of the magnets91and92, the magnetization direction is the radial direction of the annular magnet unit42on the d-axis side, and the magnetization direction of the annular magnet unit42is the circumferential direction on the q-axis side. Hereinafter, it will be described in more detail. As illustrated inFIG.9, each of the magnets91and92has a first portion250and two second portions260located on both sides of the first portion250in the circumferential direction of the magnet unit42. In other words, the first portion250is closer to the d-axis than the second portion260is, and the second portion260is closer to the q-axis than the first portion250is. In addition, the magnet unit42is configured in such a manner that the direction of an axis of easy magnetization300of the first portion250is more parallel to the d-axis than the direction of an axis of easy magnetization310of the second portion260. In other words, the magnet unit42is configured in such a manner that an angle θ11 formed by the axis of easy magnetization300of the first portion250and the d-axis is smaller than an angle θ12 formed by the axis of easy magnetization310of the second portion260and the q-axis.

More specifically, the angle θ11 is an angle formed by the d-axis and the axis of easy magnetization300when the direction from the stator50(armature) to the magnet unit42is positive on the d-axis. The angle θ12 is an angle formed by the q-axis and the axis of easy magnetization310when the direction from the stator50(armature) to the magnet unit42is positive on the q-axis. Both the angle θ11 and the angle θ12 are 90° or less in this embodiment. Each of the axes of easy magnetization300and310referred to here is defined by the following. If one axis of easy magnetization faces a direction A11and the other axis of easy magnetization faces a direction B11in each of the magnets91and92, the absolute value (|cos θ|) of the cosine of the angle θ formed by the direction A11and the direction B11is the axis of easy magnetization300or the axis of easy magnetization310.

That is, each of the magnets91and92has a different direction of the axis of easy magnetization on the d-axis side (the portion near the d-axis) and the q-axis side (the portion near the q-axis), and on the d-axis side, the direction of the axis of easy magnetization is close to the direction parallel to the d-axis, and on the q-axis side, the direction of the easy magnetization axis is close to the direction orthogonal to the q-axis. In addition, an arc-shaped magnet magnetic path is formed in accordance with the direction of the axis of easy magnetization. Moreover, in each of the magnets91and92, the axis of easy magnetization may be oriented parallel to the d-axis on the d-axis side, and the axis of easy magnetization may be oriented orthogonal to the q-axis on the q-axis side.

Further, in the magnets91and92, of the peripheral surfaces of the magnets91and92, the outer surface on the stator side on the stator50side (lower side inFIG.9) and the end face on the q-axis side in the circumferential direction are magnetic flux acting surfaces which are inflow and outflow surfaces of magnetic flux, and a magnet magnetic path is formed so as to connect these magnetic flux acting surfaces (the outer surface on the stator side and the end face on the q-axis side).

In the magnet unit42, magnetic flux flows in an arc shape between adjacent N and S poles due to the magnets91and92, and thus the magnet magnetic path is longer than that of, for example, a radial anisotropic magnet. Therefore, as illustrated inFIG.17, the magnetic flux density distribution is close to a sine wave. As a result, unlike the magnetic flux density distribution of the radial anisotropic magnet illustrated as a comparative example inFIG.18, the magnetic flux can be concentrated on the center side of the magnetic poles, and the torque of the rotating electric machine10can be increased. Further, it can be confirmed that the magnet unit42of the present embodiment has a difference in the magnetic flux density distribution as compared with a conventional Halbach array magnet. Moreover, inFIGS.17and18, the horizontal axis represents an electrical angle and the vertical axis represents a magnetic flux density. Further, inFIGS.17and18, 90° on the horizontal axis indicates the d-axis (that is, the center of the magnetic pole), and 0° and 180° on the horizontal axis indicate the q-axis.

That is, according to the magnets91and92having the above configuration, the magnet magnetic flux on the d-axis is strengthened and the change in magnetic flux near the q-axis is suppressed. As a result, magnets91and92in which the change in surface magnetic flux from the q-axis to the d-axis at each magnetic pole is gentle can be preferably achieved.

The sine wave matching rate of the magnetic flux density distribution should be, for example, a value of 40% or more. By doing so, it is possible to reliably improve the amount of magnetic flux in the central portion of the waveform as compared with the case of using a radially oriented magnet or a parallel oriented magnet having a sine wave matching rate of approximately 30%. Further, if the sine wave matching rate is 60% or more, the amount of magnetic flux in the central portion of the waveform can be reliably improved as compared with the magnetic flux concentrated array such as the Halbach array.

In the radial anisotropic magnet illustrated inFIG.18, the magnetic flux density changes steeply in the vicinity of the q-axis. The steeper the change in magnetic flux density, the greater the eddy current generated in the stator winding51. Further, the change in magnetic flux on the stator winding51side is also steep. On the other hand, in the present embodiment, the magnetic flux density distribution is a magnetic flux waveform close to a sine wave. Therefore, the change in the magnetic flux density in the vicinity of the q-axis is smaller than the change in the magnetic flux density of the radial anisotropic magnet. As a result, the generation of eddy current can be suppressed.

In the magnet unit42, a magnetic flux is generated in the vicinity of the d-axis (that is, the center of the magnetic pole) of each of the magnets91and92in a direction orthogonal to a magnetic flux acting surface280on the stator50side, and the farther away from the magnetic flux acting surface280on the stator50side, the magnetic flux forms an arc shape farther away from the d-axis. Further, the magnetic flux more orthogonal to the magnetic flux acting surface becomes stronger. In this respect, in the rotating electric machine10of the present embodiment, since each conductor group81is thinned in the radial direction as described above, the radial center position of the conductor group81approaches the magnetic flux acting surface of the magnet unit42, and the stator50can receive a strong magnet magnetic flux from the rotor40.

Further, the stator50is provided with a cylindrical stator core52on the radial inside of the stator winding51, that is, on the side opposite to the rotor40with the stator winding51therebetween. Therefore, the magnetic flux extending from the magnetic flux acting surface of each of the magnets91and92is attracted to the stator core52and orbits while using the stator core52as a part of the magnetic path. In this case, the direction and path of the magnet magnetic flux can be optimized.

The procedure for assembling the bearing unit20, the housing30, the rotor40, the stator50, and the inverter unit60illustrated inFIG.5will be described below as a method for manufacturing the rotating electric machine10. Moreover, as illustrated inFIG.6, the inverter unit60has a unit base61and an electric component62, and each work process including the assembling process of the unit base61and the electric component62will be described. In the following description, the assembly including the stator50and the inverter unit60is referred to as a first unit, and the assembly including the bearing unit20, the housing30and the rotor40is referred to as a second unit.

This manufacturing process hasa first process for mounting the electric component62radially inside the unit base61,a second process for mounting the unit base61radially inside the stator50to manufacture the first unit,a third process for inserting the fixing section44of the rotor40into the bearing unit20assembled to the housing30to manufacture the second unit,a fourth process for mounting the first unit radially inside the second unit, anda fifth process for fastening and fixing the housing30and the unit base61.

The execution order of each of these processes is the first process, second process, third process, fourth process, and fifth process.

According to the above manufacturing method, the bearing unit20, housing30, rotor40, stator50, and inverter unit60are assembled as a plurality of assemblies (subassemblies), and then the assemblies are assembled to each other. Therefore, ease of handling and completion of inspection for each unit can be achieved, and a rational assembly line can be constructed. Consequently, it is possible to easily cope with multi-product production.

In the first process, a good thermal conductor having good thermal conductivity is attached to at least one of the radial inside of the unit base61and the radial outside of the electric component62by coating, adhesion, or the like, and in that state, the electric component62is preferably attached to the unit base61. This makes it possible to effectively transmit the heat generated by the semiconductor module66to the unit base61.

In the third process, the rotor40is preferably inserted while maintaining the coaxiality between the housing30and the rotor40. Specifically, for example, using a jig for determining the position of the outer peripheral surface of the rotor40(outer peripheral surface of the magnet holder41) or the inner peripheral surface of the rotor40(inner peripheral surface of the magnet unit42) with reference to the inner peripheral surface of the housing30, the housing30and the rotor40are assembled while sliding either the housing30or the rotor40along the jig. As a result, heavy parts can be assembled without applying an unbalanced load to the bearing unit20, and the reliability of the bearing unit20is improved.

In the fourth process, it is preferable to assemble the first unit and the second unit while maintaining the coaxiality between both units. Specifically, for example, using a jig for determining the position of the inner peripheral surface of the unit base61with reference to the inner peripheral surface of the fixing section44of the rotor40, each of the first unit and the second unit is assembled while sliding either one of them along the jig. As a result, it is possible to assemble the rotor40and the stator50while preventing mutual interference with each other between the minimum gaps, and therefore it is possible to eliminate defective products caused by assembly, such as damage to the stator winding51and chipping of permanent magnets.

The order of each of the above processes may also be the second process, third process, fourth process, fifth process, and first process. In this case, the delicate electric component62is assembled last, and the stress on the electric component62in the assembling process can be minimized.

Next, the configuration of the control system that controls the rotating electric machine10will be described.FIG.19is an electrical circuit diagram of the control system of the rotating electric machine10, andFIG.20is a functional block diagram illustrating control processing by a control device110.

InFIG.19, two sets of three-phase windings51aand51bare illustrated as the stator winding51. The three-phase winding51aincludes a U-phase winding, a V-phase winding, and a W-phase winding, and the three-phase winding51bincludes an X-phase winding, a Y-phase winding, and a Z-phase winding. A first inverter101and a second inverter102, which correspond to power converters, are provided for each of the three-phase windings51aand51b, respectively. The inverters101and102are composed of a full bridge circuit having the same number of upper and lower arms as the number of phases of the phase windings, and the energization current is adjusted in each phase winding of the stator winding51by turning on/off a switch (semiconductor switching element) provided on each arm.

A DC power supply103and a smoothing capacitor104are connected in parallel to each of the inverters101and102. The DC power supply103is composed of, for example, an assembled battery in which a plurality of single batteries are connected in series. Moreover, each switch of the inverters101and102corresponds to the semiconductor module66illustrated inFIG.1and the like, and the capacitor104corresponds to the capacitor module68illustrated inFIG.1and the like.

The control device110includes a microcomputer composed of a CPU and various memories, and performs energization control by turning on/off each switch in the inverters101and102on the basis of various detected information in the rotating electric machine10and requests for power running and power generation. The control device110corresponds to the control device77illustrated inFIG.6. The detected information of the rotating electric machine10includes, for example, a rotation angle (electrical angle information) of the rotor40detected by an angle detector such as a resolver, a power supply voltage (inverter input voltage) detected by a voltage sensor, and an energization current of each phase detected by a current sensor. The control device110generates and outputs an operation signal for operating each switch of the inverters101and102. Moreover, the request for power generation is, for example, a request for regenerative driving when the rotating electric machine10is used as a power source for a vehicle.

The first inverter101includes a series connection body of an upper arm switch Sp and a lower arm switch Sn in three phases composed of the U phase, V phase, and W phase. The high potential side terminal of the upper arm switch Sp of each phase is connected to the positive electrode terminal of the DC power supply103, and the low potential side terminal of the lower arm switch Sn of each phase is connected to the negative electrode terminal (ground) of the DC power supply103. One ends of the U-phase winding, V-phase winding, and W-phase winding are connected to the intermediate connection points between the upper arm switch Sp and the lower arm switch Sn of each phase, respectively. These respective phase windings are connected in a star-shape (Y-connected), and the other ends of the respective phase windings are connected to each other at a neutral point.

The second inverter102has the same configuration as that of the first inverter101, and includes a series connection body of the upper arm switch Sp and the lower arm switch Sn in three phases composed of the U phase, V phase, and W phase. The high potential side terminal of the upper arm switch Sp of each phase is connected to the positive electrode terminal of the DC power supply103, and the low potential side terminal of the lower arm switch Sn of each phase is connected to the negative electrode terminal (ground) of the DC power supply103. One ends of the X-phase winding, Y-phase winding, and Z-phase winding are connected to the intermediate connection points between the upper arm switch Sp and the lower arm switch Sn of each phase, respectively. These respective phase windings are connected in a star-shape (Y-connected), and the other ends of the respective phase windings are connected to each other at a neutral point.

FIG.20illustrates current feedback control processing for controlling each phase current of the U, V, and W phases, and current feedback control processing for controlling each phase current of the X, Y, and Z phases. Here, first, the control processing on the U, V, and W phase side will be described.

InFIG.20, a current command value setting unit111uses a torque-dq map and sets a d-axis current command value and a q-axis current command value on the basis of the power running torque command value or the power generation torque command value for the rotating electric machine10and an electric angular velocity ω obtained by time-differentiating an electrical angle θ. Moreover, the current command value setting unit111is commonly provided on the U, V, and W phase side and the X, Y, and Z phase side. Note that the power generation torque command value is, for example, a regenerative torque command value when the rotating electric machine10is used as a power source for a vehicle.

A dq conversion unit112converts, the current detected values (three phase currents) by the current sensors provided for each phase, into a d-axis current and a q-axis current which are components of an orthogonal two-dimensional rotation coordinate system with the field magnet direction (direction of an axis of a magnetic field or field direction) as the d-axis.

A d-axis current feedback control unit113calculates a d-axis command voltage as an operation amount for feedback-controlling the d-axis current to the d-axis current command value. Further, a q-axis current feedback control unit114calculates a q-axis command voltage as an operation amount for feedback-controlling the q-axis current to the q-axis current command value. In each of these feedback control units113and114, the command voltage is calculated with the use of the PI feedback method on the basis of the deviation with respect to the current command values of the d-axis current and the q-axis current.

A three-phase conversion unit115converts the d-axis and q-axis command voltages into U-phase, V-phase, and W-phase command voltages. Moreover, each of the above units111to115is a feedback control unit that performs feedback control of the fundamental wave current according to the dq conversion theory, and the U-phase, V-phase, and W-phase command voltages are feedback control values.

In addition, an operation signal generation unit116uses a well-known triangular wave carrier comparison method to generate an operation signal of the first inverter101on the basis of the command voltages of the three phases. Specifically, the operation signal generation unit116generates a switch operation signal (duty signal) of the upper and lower arms in each phase by PWM control based on the magnitude comparison between the signal obtained by standardizing the command voltage of the three phases with the power supply voltage and the carrier signal such as a triangular wave signal.

Further, the X, Y, and Z phase side also has the same configuration, and a dq conversion unit122converts the current detected values (three phase currents) by the current sensor provided for each phase into the d-axis current and q-axis current, which are components of an orthogonal two-dimensional rotation coordinate system with the field direction as the d-axis.

A d-axis current feedback control unit123calculates a d-axis command voltage, and a q-axis current feedback control unit124calculates a q-axis command voltage. A three-phase conversion unit125converts the d-axis and q-axis command voltages into X-phase, Y-phase, and Z-phase command voltages. In addition, an operation signal generation unit126generates an operation signal of the second inverter102on the basis of the command voltages of the three phases. Specifically, the operation signal generation unit126generates a switch operation signal (duty signal) of the upper and lower arms in each phase by PWM control based on the magnitude comparison between the signal obtained by standardizing the command voltage of the three phases with the power supply voltage and the carrier signal such as a triangular wave signal.

A driver117turns on/off the switches Sp and Sn of each of the three phases in the inverters101and102on the basis of the switch operation signals generated by the operation signal generation units116and126.

Subsequently, the torque feedback control processing will be described. This process is mainly used for the purpose of increasing the output of the rotating electric machine10and reducing the loss under operating conditions in which the output voltage of each of the inverters101and102becomes large, such as in a high rotation region and a high output region. The control device110selects and executes either the torque feedback control processing or the current feedback control processing on the basis of the operating conditions of the rotating electric machine10.

FIG.21illustrates torque feedback control processing corresponding to the U, V, and W phases and torque feedback control processing corresponding to the X, Y, and Z phases. Moreover, inFIG.21, the same configurations as those inFIG.20are designated by the same reference signs and the description thereof will be omitted. Here, first, the control processing on the U, V, and W phase side will be described.

A voltage amplitude calculation unit127calculates a voltage amplitude command which is a command value of the magnitude of the voltage vector, on the basis of the power running torque command value or the power generation torque command value for the rotating electric machine10and the electric angular velocity ω obtained by time-differentiating the electrical angle θ.

A torque estimation unit128acalculates a torque estimated value corresponding to the U, V, and W phases on the basis of the d-axis current and the q-axis current converted by the dq conversion unit112. Moreover, the torque estimation unit128amay calculate the voltage amplitude command on the basis of the map information in which the d-axis current, the q-axis current, and the voltage amplitude command are associated.

A torque feedback control unit129acalculates a voltage phase command which is a command value of the phase of the voltage vector, as an operation amount for feedback-controlling the torque estimated value to the power running torque command value or the power generation torque command value. The torque feedback control unit129acalculates the voltage phase command with the use of the PI feedback method on the basis of the deviation of the torque estimated value with respect to the power running torque command value or the power generation torque command value.

The operation signal generation unit130agenerates an operation signal of the first inverter101on the basis of the voltage amplitude command, the voltage phase command, and the electrical angle θ. Specifically, the operation signal generation unit130acalculates command voltages of three phases on the basis of the voltage amplitude command, the voltage phase command, and the electrical angle θ, and generates the switch operation signal of the upper and lower arms in each phase by PWM control based on the magnitude comparison between the signal obtained by standardizing the calculated command voltages of three phases with the power supply voltage and the carrier signal such as a triangular wave signal.

By the way, the operation signal generation unit130amay generate the switch operation signal on the basis of the pulse pattern information which is map information in which the voltage amplitude command, the voltage phase command, the electrical angle θ, and the switch operation signal are associated, the voltage amplitude command, the voltage phase command, and the electrical angle θ.

Further, the X, Y, and Z phase side also has the same configuration, and the torque estimation unit128bcalculates a torque estimated value corresponding to the X, Y, and Z phases on the basis of the d-axis current and the q-axis current converted by the dq conversion unit122.

The torque feedback control unit129bcalculates a voltage phase command as an operation amount for feedback-controlling the torque estimated value to the power running torque command value or the power generation torque command value. The torque feedback control unit129bcalculates the voltage phase command with the use of the PI feedback method on the basis of the deviation of the torque estimated value with respect to the power running torque command value or the power generation torque command value.

The operation signal generation unit130bgenerates an operation signal of the first inverter102on the basis of the voltage amplitude command, the voltage phase command, and the electrical angle θ. Specifically, the operation signal generation unit130bcalculates command voltages of three phases on the basis of the voltage amplitude command, the voltage phase command, and the electrical angle θ, and generates the switch operation signal of the upper and lower arms in each phase by PWM control based on the magnitude comparison between the signal obtained by standardizing the calculated command voltages of three phases with the power supply voltage and the carrier signal such as a triangular wave signal. The driver117turns on/off the switches Sp and Sn of each of the three phases in the inverters101and102on the basis of the switch operation signals generated by the operation signal generation units130aand130b.

Incidentally, the operation signal generation unit130bmay generate switch operation signals on the basis of the pulse pattern information which is map information in which the voltage amplitude command, the voltage phase command, the electrical angle θ, and the switch operation signal are associated, the voltage amplitude command, the voltage phase command, and the electrical angle θ.

By the way, in the rotating electric machine10, there is a concern that electrolytic corrosion of the bearings21and22may occur due to the generation of a shaft current. For example, there is a concern that, when the energization of the stator winding51is switched by switching, magnetic flux distortion occurs due to a slight deviation in switching timing (switching imbalance), which causes electrolytic corrosion in the bearings21and22that support the rotating shaft11. The distortion of the magnetic flux occurs in accordance with the inductance of the stator50, and the electromotive voltage in the axial direction generated by the distortion of the magnetic flux causes dielectric breakdown in the bearings21and22, and electrolytic corrosion proceeds.

In this regard, in the present embodiment, the following three countermeasures are taken as countermeasures against electrolytic corrosion. A first electrolytic corrosion countermeasure is an electrolytic corrosion suppression countermeasure by reducing the inductance due to the coreless stator50and by smoothing the magnet magnetic flux of the magnet unit42. A second electrolytic corrosion countermeasure is an electrolytic corrosion suppression countermeasure by adopting a cantilever structure with the bearings21and22for the rotating shaft. A third electrolytic corrosion countermeasure is an electrolytic corrosion suppression countermeasure by molding the annular stator winding51together with the stator core52with a molding material. The details of each of these countermeasures will be described below individually.

First, in the first electrolytic corrosion countermeasure, in the stator50, the spaces between each conductor group81in the circumferential direction are made teethless, and a sealing member57made of a non-magnetic material instead of the teeth (iron core) is provided between each conductor group81(seeFIG.10). This makes it possible to reduce the inductance of the stator50. By reducing the inductance of the stator50, even if the switching timing shift occurs when the stator winding51is energized, the occurrence of magnetic flux distortion due to the switching timing shift can be suppressed, and thus it is possible to suppress the electrolytic corrosion of the bearings21and22. Moreover, it is preferable that the inductance of the d-axis is equal to or less than the inductance of the q-axis.

Further, the magnets91and92are oriented in such a manner that the direction of the axis of easy magnetization is more parallel to the d-axis on the d-axis side as compared with the q-axis side (seeFIG.9). As a result, the magnet magnetic flux on the d-axis is strengthened, and the change in surface magnetic flux (increase/decrease in magnetic flux) from the q-axis to the d-axis becomes gentle at each magnetic pole. Therefore, the sudden voltage change caused by the switching imbalance is suppressed, and thus a configuration that can contribute to the suppression of electrolytic corrosion is implemented.

In the second electrolytic corrosion countermeasure, in the rotating electric machine10, the respective bearings21and22are arranged unevenly on either side in the axial direction with respect to the axial center of the rotor40(seeFIG.2). As a result, the influence of electrolytic corrosion can be reduced as compared with a configuration in which a plurality of bearings are provided on both sides of the rotor in the axial direction. That is, in a configuration in which the rotor is supported from both sides by a plurality of bearings, a closed circuit that passes through the rotor, the stator, and each bearing (that is, each bearing on both sides in the axial direction with the rotor therebetween) is formed as a high frequency magnetic flux is generated, and there is a concern about electrolytic corrosion of the bearing due to the shaft current. On the other hand, in the configuration in which the rotor40is cantilevered and supported by a plurality of bearings21and22, the closed circuit is not formed and the electrolytic corrosion of the bearings is suppressed.

Further, the rotating electric machine10has the following configuration in connection with the configuration for arranging the bearings21and22on one side. In the magnet holder41, the contact avoiding section that extends in the axial direction and avoids contact with the stator50is provided at the intermediate section45that projects in the radial direction of the rotor40(seeFIG.2). In this case, when a closed circuit of the shaft current is formed via the magnet holder41, the closed circuit length can be lengthened to increase the circuit resistance. As a result, the electrolytic corrosion of the bearings21and22can be suppressed.

The holding member23of the bearing unit20is fixed to the housing30on one side in the axial direction with the rotor40therebetween, and the housing30and the unit base61(stator holder) are coupled to each other on the other side (seeFIG.2). According to this configuration, it is possible to preferably implement a configuration in which the respective bearings21and22are unevenly arranged on one side of the rotating shaft11in the axial direction. In addition, in this configuration, since the unit base61is connected to the rotating shaft11via the housing30, the unit base61can be arranged at a position electrically separated from the rotating shaft11. Moreover, if an insulating member such as resin is interposed between the unit base61and the housing30, the unit base61and the rotating shaft11are electrically further separated from each other. As a result, the electrolytic corrosion of the bearings21and22can be appropriately suppressed.

In the rotating electric machine10of the present embodiment, the shaft voltage acting on the bearings21and22is reduced by arranging the respective bearings21and22on one side, and the like. Further, the potential difference between the rotor40and the stator50is reduced. Therefore, it is possible to reduce the potential difference acting on the bearings21and22without using conductive grease in the bearings21and22. Since the conductive grease generally contains fine particles such as carbon, it is considered that noise is generated. In this regard, in the present embodiment, non-conductive grease is used in the bearings21and22. Therefore, it is possible to suppress the inconvenience of noise in the bearings21and22. For example, in the application to an electric vehicle such as an electric vehicle, it is considered that a countermeasure against the noise of the rotating electric machine10is required, and it is possible to preferably implement the countermeasure against the noise.

In the third electrolytic corrosion countermeasure, the stator winding51is molded together with the stator core52with a molding material to suppress the displacement of the stator winding51in the stator50(seeFIG.11). In particular, since the rotating electric machine10of the present embodiment does not have an interconductor member (teeth) between each conductor group81in the circumferential direction of the stator winding51, there is a concern that the stator winding51may be displaced, but by molding the stator winding51together with the stator core52, the displacement of the conductor position of the stator winding51is suppressed. Consequently, it is possible to suppress the distortion of the magnetic flux due to the displacement of the stator winding51and the occurrence of electrolytic corrosion of the bearings21and22due to the distortion.

Moreover, since the unit base61as a housing member that fixes the stator core52is made of carbon fiber reinforced plastic (CFRP), the electric discharge to the unit base61is suppressed as compared with the case where it is made of, for example, aluminum. Thus, a suitable countermeasure against electrolytic corrosion is possible.

In addition to that, as a countermeasure against electrolytic corrosion of the bearings21and22, it is also possible to use a configuration in which at least one of the outer ring25and the inner ring26is made of a ceramic material, or in which an insulating sleeve is provided on the outside of the outer ring25.

Hereinafter, other embodiments will be described with a focus on differences from the first embodiment.

Second Embodiment

In the present embodiment, the polar anisotropic structure of the magnet unit42in the rotor40is changed, which will be described in detail below.

As illustrated inFIGS.22and23, the magnet unit42is composed with the use of a magnet array called a Halbach array. That is, the magnet unit42has a first magnet131in which the magnetization direction (direction of the magnetization vector) is the radial direction and a second magnet132in which the magnetization direction (direction of the magnetization vector) is the circumferential direction. The first magnets131are arranged at predetermined intervals in the circumferential direction, and the second magnets132are arranged at a position between the adjacent first magnets131in the circumferential direction. The first magnet131and the second magnet132are permanent magnets made of rare earth magnets such as neodymium magnets.

The first magnets131are arranged so as to be apart from each other in the circumferential direction in such a manner that the poles on the side facing the stator50(inside in the radial direction) are alternately N poles and S poles. Further, the second magnets132are arranged next to each first magnet131in such a manner that the polarities alternate in the circumferential direction. The cylindrical section43provided so as to surround each of the magnets131and132is preferably a soft magnetic substance core made of a soft magnetic material, and functions as a back core. Moreover, the magnet unit42of the second embodiment also has the same relation of the axis of easy magnetization with respect to the d-axis and the q-axis in the d-q coordinate system as in the first embodiment.

Further, a magnetic substance133made of a soft magnetic substance is arranged on radially outside the first magnet131, that is, on the side of the cylindrical section43of the magnet holder41. For example, the magnetic substance133is preferably made of an electromagnetic steel sheet, soft iron, or a dust core material. In this case, the circumferential length of the magnetic substance133is the same as the circumferential length of the first magnet131(particularly, the circumferential length of the outer peripheral portion of the first magnet131). Further, in a state where the first magnet131and the magnetic substance133are integrated, the radial thickness of the integrated object is the same as the radial thickness of the second magnet132. In other words, the radial thickness of the first magnet131is thinner than that of the second magnet132by the amount of the magnetic substance133. Each of the magnets131and132and the magnetic substance133are fixed to each other by, for example, an adhesive. In the magnet unit42, the radial outside of the first magnet131is the opposite side to the stator50, and the magnetic substance133is provided on the side opposite to the stator50(opposite-to-stator side) in both sides of the first magnet131in the radial direction.

A key134is formed on the outer peripheral portion of the magnetic substance133as a protrusion that protrudes outward in the radial direction, that is, toward the side of the cylindrical section43of the magnet holder41. Further, a key groove135is formed on the inner peripheral surface of the cylindrical section43as a recess for housing the key134of the magnetic substance133. The protruding shape of the key134and the groove shape of the key groove135are the same, and the same number of key grooves135as the key134are formed corresponding to the key134formed on each magnetic substance133. By engaging the key134and the key groove135, the displacement of the first magnet131and the second magnet132and the magnet holder41in the circumferential direction (rotation direction) is suppressed. Moreover, it is optional whether the key134and the key groove135(protrusion and recess) are provided in either of the cylindrical section43or the magnetic substance133of the magnet holder41, and contrary to the above, it is also possible to provide the key groove135on the outer peripheral portion of the magnetic substance133and to provide the key134on the inner peripheral portion of the cylindrical section43of the magnet holder41.

Here, in the magnet unit42, the magnetic flux density in the first magnet131can be increased by alternately arranging the first magnet131and the second magnet132. Therefore, in the magnet unit42, the magnetic flux can be concentrated on one side, and the magnetic flux can be strengthened on the side closer to the stator50.

Further, by arranging the magnetic substance133radially outside the first magnet131, that is, on the opposite-to-stator side, it is possible to suppress partial magnetic saturation on the radial outside of the first magnet131, and thus demagnetization of the first magnet131caused by the magnetic saturation can be suppressed. As a result, it is accordingly possible to increase the magnetic force of the magnet unit42. The magnet unit42of the present embodiment has, so to speak, a configuration in which a portion of the first magnet131in which demagnetization is likely to occur is replaced with the magnetic substance133.

FIGS.24(a) and24(b)are diagrams specifically illustrating the flow of magnetic flux in the magnet unit42,FIG.24(a)illustrates a case where a conventional configuration is used in which the magnet unit42does not have the magnetic substance133, andFIG.24(b)illustrates a case where the configuration of the present embodiment having the magnetic substance133in the magnet unit42is used. Moreover, inFIGS.24(a) and24(b), the cylindrical section43of the magnet holder41and the magnet unit42are illustrated in a linearly developed manner, with the lower side of the figure being the stator side and the upper side being the opposite-to-stator side.

In the configuration ofFIG.24(a), the magnetic flux acting surface of the first magnet131and the side surface of the second magnet132are in contact with the inner peripheral surface of the cylindrical section43, respectively. Further, the magnetic flux acting surface of the second magnet132is in contact with the side surface of the first magnet131. In this case, in the cylindrical section43, the combined magnetic flux of a magnetic flux F1that enters the contact surface with the first magnet131through the outer path of the second magnet132and the magnetic flux that is substantially parallel to the cylindrical section43and attracts a magnetic flux F2of the second magnet132is generated. Therefore, there is a concern that magnetic saturation may partially occur in the vicinity of the contact surface between the first magnet131and the second magnet132in the cylindrical section43.

On the other hand, in the configuration ofFIG.24(b), the magnetic substance133is formed between the magnetic flux acting surface of the first magnet131and the inner peripheral surface of the cylindrical section43on the side opposite to the stator50of the first magnet131, and therefore the magnetic substance133allows the passage of magnetic flux. Consequently, magnetic saturation in the cylindrical section43can be suppressed, and the proof stress against demagnetization is improved.

Further, in the configuration ofFIG.24(b), unlikeFIG.24(a), the flux F2that promotes magnetic saturation can be cancelled As a result, the permeance of the entire magnetic circuit can be effectively improved. With such a configuration, the magnetic circuit characteristics can be maintained even under severe high heat conditions.

Further, the magnet magnetic path passing through the inside of the magnet becomes longer than that of a radial magnet in a conventional SPM rotor. Therefore, the magnet permeance can rise, the magnetic force can be enhanced, and the torque can be increased. Furthermore, the magnetic flux is concentrated in the center of the d-axis, and thus the sine wave matching rate can be increased. In particular, if the current waveform is made into a sine wave or a trapezoidal wave by PWM control, or if a switching IC energized at 120 degrees is used, the torque can be increased more effectively.

Moreover, in a case where the stator core52is made of an electromagnetic steel sheet, the radial thickness of the stator core52is preferably ½ or more than ½ of the radial thickness of the magnet unit42. For example, the radial thickness of the stator core52is preferably ½ or more of the radial thickness of the first magnet131provided at the center of the magnetic pole in the magnet unit42. Further, the radial thickness of the stator core52is preferably smaller than the radial thickness of the magnet unit42. In this case, the magnet magnetic flux is approximately 1 [T], and the saturation magnetic flux density of the stator core52is 2 [T]. Therefore, by setting the radial thickness of the stator core52to ½ or more of the radial thickness of the magnet unit42, it is possible to prevent magnetic flux leakage to the inner peripheral side of the stator core52.

In a magnet having a Halbach structure or a polar anisotropic structure, since the magnetic path has a pseudo arc shape, the magnetic flux can be increased in proportion to the thickness of the magnet that handles the magnetic flux in the circumferential direction. In such a configuration, it is considered that the magnetic flux flowing through the stator core52does not exceed the magnetic flux in the circumferential direction. That is, in a case where an iron-based metal having a saturation magnetic flux density of 2 [T] is used with respect to a magnetic flux of the magnet 1 [T], if the thickness of the stator core52is set to half or more of the magnet thickness, it is possible to provide a rotating electric machine that is not magnetically saturated and is suitably small and lightweight. Here, since the diamagnetic field from the stator50acts on the magnet magnetic flux, the magnet magnetic flux is generally 0.9 [T] or less. Therefore, if the stator core has half the thickness of the magnet, its magnetic permeability can be kept suitably high.

Hereinafter, a modification in which a part of the above-described configuration is modified will be described.

First Modification

In the above embodiment, the outer peripheral surface of the stator core52has a curved surface without unevenness, and a plurality of conductor groups81are arranged side by side at predetermined intervals on the outer peripheral surface, but this may be changed. For example, as illustrated inFIG.25, the stator core52has an annular yoke141provided on the side opposite to the rotor40(lower side in the figure) on both sides of the stator winding51in the radial direction and protruding sections142extending from the yoke141so as to protrude between the straight sections83adjacent to each other in the circumferential direction. The protruding sections142are provided at predetermined intervals on the radially outside the yoke141, that is, on the rotor40side. The respective conductor groups81of the stator winding51are engaged with the protruding sections142in the circumferential direction, and are arranged side by side in the circumferential direction while using the protruding section142as a positioning section of the conductor group81. Moreover, the protruding section142corresponds to the “interconductor member”.

In the protruding section142, the radial thickness dimension from the yoke141, in other words, as illustrated inFIG.25, in the radial direction of the yoke141, a distance W from the inner side surface320adjacent to the yoke141of the straight section83to the apex of the protruding section142is smaller than ½ of the radial thickness dimension of the straight section83radially adjacent to the yoke141among the plurality of straight sections38inside and outside the radial direction (H1in the figure). In other words, the non-magnetic member (sealing member57) should occupy a range of three-quarters of a dimension (thickness) T1of the conductor group81(conducting member) in the radial direction of the stator winding51(stator core52) (twice the thickness of the conductor wire82, in other words, the shortest distance between the surface320in contact with the stator core52of the conductor group81and a surface330facing the rotor40of the conductor group81). Due to the thickness limitation of the protruding section142, the protruding section142does not function as teeth between the conductor groups81(that is, the straight section83) adjacent to each other in the circumferential direction, and the magnetic path is not formed by the teeth. Not all of the protruding sections142may not be provided between the conductor groups81arranged in the circumferential direction, but should be provided between at least one set of the conductor groups81adjacent to each other in the circumferential direction. For example, the protruding sections142are preferably provided at equal intervals for each predetermined number of the conductor groups81in the circumferential direction. The shape of the protruding section142may be any shape such as a rectangular shape or an arc shape.

Further, the straight section83may be provided as a single layer on the outer peripheral surface of the stator core52. Consequently, in a broad sense, the radial thickness dimension of the protruding section142from the yoke141may be smaller than ½ of the radial thickness dimension of the straight section83.

Moreover, assuming a virtual circle centered on the shaft center of the rotating shaft11and passing through the radial center position of the straight section83radially adjacent to the yoke141, the protruding section142preferably has a shape that protrudes from the yoke141within the range of the virtual circle, in other words, a shape that does not protrude radially outward of the virtual circle (that is, on the rotor40side).

According to the above configuration, the protruding section142has a limited radial thickness dimension and does not function as the teeth between the straight sections83adjacent to each other in the circumferential direction. Therefore, it is possible to bring the respective adjacent straight sections83closer to each other as compared with the case where the teeth are provided between the respective straight sections83. As a result, the cross-sectional area of the conductor82acan be increased, and the heat generated by the energization of the stator winding51can be reduced. In such a configuration, the absence of teeth makes it possible to eliminate magnetic saturation and increase the energization current to the stator winding51. In this case, it is possible to preferably cope with the increase in the amount of heat generated as the energization current increases. Further, in the stator winding51, since the turn section84is shifted in the radial direction and has an interference avoidance section for avoiding interference with other turn sections84, the different turn sections84can be separated from each other in the radial direction. As a result, heat dissipation can be improved even in the turn section84. As described above, it is possible to optimize the heat dissipation performance of the stator50.

Further, if the yoke141of the stator core52and the magnet unit42of the rotor40(that is, the magnets91and92) are separated by a predetermined distance or more, the radial thickness dimension of the protruding section142is not limited to H1inFIG.25Specifically, if the yoke141and the magnet unit42are separated by 2 mm or more, the radial thickness dimension of the protruding section142may be H1or more inFIG.25. For example, in a case where the radial thickness dimension of the straight section83exceeds 2 mm and the conductor group81is composed of two layers of conductor wires82inside and outside the radial direction, the protruding section142may be provided in the straight section83not adjacent to the yoke141, that is, in the range from the yoke141to the half position of the second conductor wire82. In this case, if the radial thickness dimension of the protruding section142is up to “H1× 3/2”, the effect can be obtained not a little by increasing the conductor cross-sectional area in the conductor group81.

Further, the stator core52may have the configuration illustrated inFIG.26. Moreover, although the sealing member57is omitted inFIG.26, the sealing member57may be provided. InFIG.26, for convenience, the magnet unit42and the stator core52are illustrated in a linearly developed manner.

In the configuration ofFIG.26, the stator50has the protruding section142as an interconductor member between the conductor wires82(that is, the straight section83) adjacent to each other in the circumferential direction. When the stator winding51is energized, the stator50magnetically functions together with one of the magnetic poles (N pole or S pole) of the magnet unit42, and has a part350extending in the circumferential direction of the stator50. When the circumferential length of the stator50of this part350is Wn, the total width of the protruding sections142existing in this length range Wn (that is, the total dimension of the stator50in the circumferential direction) is Wt, the saturation magnetic flux density of the protruding section142is Bs, the width dimension for one pole of the magnet unit42in the circumferential direction is Wm, and the residual magnetic flux density of the magnet unit42is Br, the protruding section142is made of a magnetic material of a formula (1).
Wt*Bs≤Wm*Br(1)

Moreover, the range Wn is set so as to include a plurality of conductor groups81adjacent to each other in the circumferential direction and include a plurality of conductor groups81having overlapping excitation times. In doing so, it is preferable to set the center of the void56of the conductor group81as a reference (boundary) when setting the range Wn. For example, in the case of the configuration illustrated inFIG.26, the conductor groups81up to the fourth in order from the one with the shortest distance from the center of the magnetic pole of the N pole in the circumferential direction correspond to the aforementioned plurality of conductor groups81. In addition, the range Wn is set so as to include the four conductor groups81. In doing so, the ends (starting point and ending point) of the range Wn are set as the center of the void56.

InFIG.26, since halves of the protruding sections142are included at both ends of the range Wn, the range Wn includes a total of four protruding sections142. Consequently, when the width of the protruding section142(that is, the dimension of the protruding section142in the circumferential direction of the stator50, in other words, the interval between the adjacent conductor groups81) is A, the total width of the protruding sections142included in the range Wn is Wt=½A+A+A+A+½A=4A.

Specifically, in the present embodiment, the three-phase winding of the stator winding51is a distributed winding, and in the stator winding51, the number of protruding sections142with respect to one pole of the magnet unit42, that is, the number of voids56between the respective conductor groups81is a “number of phases*Q”. Here, Q is the number of the one-phase conductor wires82that are in contact with the stator core52. Moreover, in a case where the conductor wires82are the conductor group81stacked in the radial direction of the rotor40, it can also be considered to be the number of the conductor wires82on the inner peripheral side of the one-phase conductor group81. In this case, when the three-phase winding of the stator winding51is energized in a predetermined order for each phase, the protruding sections142for two phases are excited in one pole. Consequently, the total circumferential width dimension Wt of the protruding section142excited by the energization of the stator winding51in the range for one pole of the magnet unit42is “the number of excited phases *Q*A=2*2*A” when the circumferential width dimension of the protruding section142(that is, the void56) is A.

In addition, after the total width dimension Wt is defined in this way, in the stator core52, the protruding section142is configured as a magnetic material fulfilling the relation (1) above. Moreover, the total width dimension Wt is also the circumferential dimension of the portion where the relative magnetic permeability can be larger than 1 in one pole. Further, in consideration of a margin, the total width dimension Wt may be set as the circumferential width dimension of the protruding section142in one magnetic pole. Specifically, since the number of protruding sections142with respect to one pole of the magnet unit42is “number of phases *Q”, the circumferential width dimension (total width dimension Wt) of the protruding sections142in one magnetic pole may be set to “the number of phases *Q*A=3*2*A=6A”.

Moreover, the distributed winding referred to here is a one-pole pair period (N-pole and S-pole) of the magnetic pole, and has a one-pole pair of the stator winding51. The one-pole pair of the stator winding51referred to here is composed of two straight sections83and a turn section84in which currents flow in opposite directions and which are electrically connected at the turn section84. If the above conditions are met, even a Short Pitch Winding is regarded as an equivalent of a distributed winding of a Full Pitch Winding.

Next, an example in the case of concentrated winding is indicated. The concentrated winding referred to here is that the width of the one-pole pair of magnetic poles and the width of the one-pole pair of the stator winding51are different. Example of concentrated winding include a concentrated winding that has relation such as three conductor groups81for one magnetic pole pair, three conductor groups81for two magnetic pole pairs, nine conductor groups81for four magnetic pole pairs, and nine conductor groups81for five magnetic pole pairs.

Here, in a case where the stator winding51is a concentrated winding, when the three-phase windings of the stator winding51are energized in a predetermined order, the stator windings51for two phases are excited. As a result, the protruding sections142for two phases are excited. Consequently, the circumferential width dimension Wt of the protruding section142excited by the energization of the stator winding51in the range for one pole of the magnet unit42is “A*2”. In addition, after the total width dimension Wt is defined in this way, the protruding section142is configured as a magnetic material fulfilling the relation (1) above. Moreover, in the case of the concentrated winding indicated above, the total circumferential width of the protruding sections142of the stator50in the region surrounded by the conductor groups81of the same phase is defined as A. Further, Wm in the concentrated winding corresponds to “the entire circumference of the surface facing the air gap of the magnet unit42”*“the number of phases”/“the number of dispersions of the conductor group81”.

Incidentally, for magnets with a BH product of 20 [MGOe (kJ/m{circumflex over ( )}3)] or more, such as neodymium magnets, samarium-cobalt magnets, and ferrite magnets, Bd=over 1.0 [T], and for iron, Br=over 2.0 [T]. Therefore, as the high output motor, in the stator core52, the protruding section142may be a magnetic material fulfilling the relation of Wt<½*Wm.

Further, in a case where the conductor wire82includes an outer layer coating182as described below, the conductor wire82may be arranged in the circumferential direction of the stator core52in such a manner that the outer layer coatings182of the conductor wires82come into contact with each other. In this case, Wt can be regarded as 0 or the thickness of the outer layer coating182of both conductor wires82in contact with each other.

In the configurations ofFIGS.25and26, an interconductor member (protruding section142) that is disproportionately small with respect to the magnet magnetic flux on the rotor40side is provided. Moreover, the rotor40is a flat surface magnet type rotor having a low inductance and does not have saliency in terms of magnetic resistance. In such a configuration, the inductance of the stator50can be reduced, the generation of magnetic flux distortion due to the deviation of the switching timing of the stator winding51is suppressed, and thus the electrolytic corrosion of the bearings21and22is suppressed.

Second Modification

The following configuration can also be adopted as the stator50using the interconductor member fulfilling the relation of the above formula (1). InFIG.27, a tooth-shaped section143is provided as an interconductor member on the outer peripheral surface side of the stator core52(upper surface side in the figure). The tooth-shaped section143is provided at predetermined intervals in the circumferential direction so as to protrude from the yoke141, and have the same thickness dimension as that of the conductor group81in the radial direction. The side surface of the tooth-shaped section143is in contact with each conductor wire82of the conductor group81. However, there may be a gap between the tooth-shaped section143and each conductor wire82.

The tooth-shaped section143is provided with a limitation on the width dimension in the circumferential direction, and is provided with polar teeth (stator teeth) that are disproportionately thin with respect to the amount of magnets. With such a configuration, the tooth-shaped section143is surely saturated by the magnetic flux of the magnet at 1.8 T or more, and the inductance can be lowered by lowering the permeance.

Here, in the magnet unit42, when the surface area per pole of the magnetic flux acting surface on the stator side is Sm and the residual magnetic flux density of the magnet unit42is Br, the magnetic flux on the magnet unit side is, for example, “Sm*Br”. Further, when the surface area on the rotor side in each tooth-shaped section143is St, the number per phase of the conductor wire82is m, and the tooth-shaped sections143for two phases are excited in one pole by energization of the stator winding51, the magnetic flux on the stator side is, for example, “St*m*2*Bs”. In this case, the inductance is reduced by limiting the dimension of the tooth-shaped section143in such a manner that a relation (2) is established.
St*m*2*Bs<Sm*Br(2)

Moreover, in a case where the magnet unit42and the tooth-shaped section143have the same axial dimension, when the circumferential width dimension for one pole of the magnet unit42is Wm, and the circumferential width dimension of the tooth-shaped section143is Wst, then the above formula (2) is replaced as in a formula (3).
Wst*m*2*Bs<Wm*Br(3)

More specifically, assuming that, for example, Bs=2T, Br=1T, and m=2, the above formula (3) has a relation of “Wst<Wm/8”. In this case, the inductance is reduced by making the width dimension Wst of the tooth-shaped section143smaller than ⅛ of the width dimension Wm for one pole of the magnet unit42. Moreover, if the number m is 1, the width dimension Wst of the tooth-shaped section143is preferably made to be smaller than ¼ of the width dimension Wm for one pole of the magnet unit42.

Moreover, in the above formula (3), “Wst*m*2” corresponds to the circumferential width dimension of the tooth-shaped section143excited by energization of the stator winding51in the range for one pole of the magnet unit42.

In the configuration ofFIG.27, similarly to the configurations ofFIGS.25and26described above, the interconductor member (tooth-shaped section143) which is disproportionately small with respect to the magnet magnetic flux on the rotor40side is provided. In such a configuration, the inductance of the stator50can be reduced, the generation of magnetic flux distortion due to the deviation of the switching timing of the stator winding51is suppressed, and thus the electrolytic corrosion of the bearings21and22is suppressed.

Third Modification

In the above embodiment, the sealing member57covering the stator winding51is provided radially outside the stator core52in the range including all the conductor groups81, that is, in the range in which the radial thickness dimension is larger than the radial thickness dimension of each conductor group81, but this may be changed. For example, as illustrated inFIG.28, the sealing member57is provided in such a manner that a part of the conductor wire82protrudes. More specifically, the sealing member57is provided in a state where a part of the conductor wire82which is the outermost in the radial direction in the conductor group81is exposed on the radial outside, that is, on the stator50side. In this case, the radial thickness dimension of the sealing member57may be the same as or smaller than the radial thickness dimension of each conductor group81.

Fourth Modification

As illustrated inFIG.29, in the stator50, each conductor group81may not be sealed by the sealing member57. That is, the sealing member57that covers the stator winding51is not used. In this case, no interconductor member is provided between the conductor groups81arranged in the circumferential direction, and an airspace is formed. In short, the interconductor member is not provided between the conductor groups81arranged in the circumferential direction. Moreover, air may be regarded as a non-magnetic substance or an equivalent of a non-magnetic substance as Bs=0, and air may be arranged in this airspace.

Fifth Modification

In a case where the interconductor member in the stator50is made of a non-magnetic material, it is possible to use a material other than resin as the non-magnetic material. For example, a metal-based non-magnetic material may be used, such as using SUS304 which is an austenitic stainless steel.

Sixth Modification

The stator50may be configured not to include the stator core52. In this case, the stator50is composed of the stator winding51illustrated inFIG.12. Moreover, in the stator50that does not include the stator core52, the stator winding51may be sealed with a sealing material. Alternatively, the stator50may be configured to include an annular winding holding section made of a non-magnetic material such as synthetic resin as an alternative to the stator core52made of a soft magnetic material.

Seventh Modification

In the above first embodiment, the plurality of magnets91and92arranged in the circumferential direction are used as the magnet unit42of the rotor40, but this may be changed, and an annular magnet which is an annular permanent magnet may be used as the magnet unit42. Specifically, as illustrated inFIG.30, an annular magnet95is fixed radially inside the cylindrical section43of the magnet holder41. The annular magnet95is provided with a plurality of magnetic poles having alternating polarities in the circumferential direction, and the magnet is integrally formed on both the d-axis and the q-axis. The annular magnet95is formed with an arc shaped magnet magnetic path such that the direction of orientation is the radial direction on the d-axis of each magnetic pole and the direction of orientation is the circumferential direction on the q-axis between the respective magnetic poles.

Moreover, in the annular magnet95, the orientation should be made in such a manner that an arc-shaped magnet magnetic path is formed, in which the axis of easy magnetization is parallel to the d-axis or close to parallel to the d-axis in the portion near the d-axis, and the axis of easy magnetization is orthogonal to the q-axis or close to parallel to the q-axis in the portion near the q-axis.

Eighth Modification

In this modification, a part of the control method of the control device110is changed. In this modification, the difference from the configuration described in the first embodiment will be mainly described.

First, with reference toFIG.31, the processing in the operation signal generation units116and126illustrated inFIG.20and the operation signal generation units130aand130billustrated inFIG.21will be described. Moreover, the processing in each operation signal generation unit116,126,130a, and130bis basically the same. Therefore, in the following, the processing of the operation signal generation unit116will be described as an example.

The operation signal generation unit116includes a carrier generation unit116aand U, V, W phase comparators116bU,116bV, and116bW. In the present embodiment, the carrier generation unit116agenerates and outputs a triangular wave signal as a carrier signal SigC.

The carrier signal SigC generated by the carrier generation unit116aand the U, V, W phase command voltages calculated by the three-phase conversion unit115are input to the U, V, W phase comparators116bU,116bV, and116bW. The U, V, W phase command voltages are, for example, sinusoidal waveforms, and the phases are shifted by 120° depending on the electrical angle.

The U, V, W phase comparators116bU,116bV, and116bW generate the operation signals of the respective switches Sp and Sn of the upper arm and the lower arm of the U, V, W phases in the first inverter101, by PWM (pulse width modulation) control based on the magnitude comparison between the U, V, W phase command voltages and the carrier signal SigC. Specifically, the operation signal generation unit116generates the operation signals of the respective switches Sp and Sn of the U, V, W phases by PWM control based on the magnitude comparison between the signal obtained by standardizing the U, V, W command voltages with the power supply voltage and the carrier signal. The driver117turns on/off each of the switches Sp and Sn of the U, V, W phases in the inverter101on the basis of the operation signals generated by the operation signal generation unit116.

The control device110performs processing that changes the carrier frequency fc of the carrier signal SignC, that is, the switching frequency of each of the switches Sp and Sn. The carrier frequency fc is set high in the low torque region or high rotation region of the rotating electric machine10and low in the high torque region of the rotating electric machine10. This setting is made in order to suppress a decrease in controllability of the current flowing through each phase winding.

That is, as the stator50becomes coreless, the inductance of the stator50can be reduced. Here, when the inductance becomes low, the electrical time constant of the rotating electric machine10becomes small. As a result, there is a concern that the ripple of the current flowing through each phase winding increases, the controllability of the current flowing through the winding decreases, and the current control diverges. The effect of this decrease in controllability can be more pronounced when the current flowing through the winding (for example, the effective value of the current) is included in the low current region than in the high current region. In order to deal with this problem, in this modification, the control device110changes the carrier frequency fc.

The processing that changes the carrier frequency fc will be described with reference toFIG.32. This processing is repeatedly executed by the control device110, for example, at a predetermined control cycle as the processing of the operation signal generation unit116.

In step S10, it is determined whether the current flowing through a winding51aof each phase is in the low current region. This processing is processing for determining that the current torque of the rotating electric machine10is in the low torque region. Examples of the method for determining whether the current is included in the low current region include the following first and second methods.

First Method

The torque estimated value of the rotating electric machine10is calculated on the basis of the d-axis current and the q-axis current converted by the dq conversion unit112. Then, when it is determined that the calculated torque estimated value is less than the torque threshold value, it is determined that the current flowing through the winding51ais included in the low current region, and when it is determined that the torque estimated value is equal to or more than the torque threshold value, it is determined that the current flowing through the winding51ais included in the high current region. Here, the torque threshold value should be set to, for example, ½ of the starting torque (also referred to as restraint torque) of the rotating electric machine10.

Second Method

When it is determined that the rotation angle of the rotor40detected by the angle detector is equal to or greater than a speed threshold value, it is determined that the current flowing through the winding51ais included in the low current region, that is, in the high rotation region. Here, the speed threshold value should be set to, for example, the rotation speed when the maximum torque of the rotating electric machine10becomes the torque threshold value.

If a negative determination is made in step S10, it is determined to be a high current region, and the processing proceeds to step S11. In step S11, the carrier frequency fc is set to a first frequency fL.

If an affirmative determination is made in step S10, the processing proceeds to step S12, and the carrier frequency fc is set to a second frequency fH which is higher than the first frequency fL.

According to this modification described above, the carrier frequency fc is set higher when the current flowing through each phase winding is included in the low current region than when it is included in the high current region. Therefore, in the low current region, the switching frequencies of the switches Sp and Sn can be increased, and the increase in current ripple can be suppressed. As a result, it is possible to suppress a decrease in current controllability.

On the other hand, when the current flowing through each phase winding is included in the high current region, the carrier frequency fc is set lower than when it is included in the low current region. In the high current region, the amplitude of the current flowing through the winding is larger than in the low current region, and therefore the increase in current ripple due to the low inductance has a small effect on the current controllability. Therefore, in the high current region, the carrier frequency fc can be set lower than in the low current region, and the switching loss of the respective inverters101and102can be reduced.

In this modification, the following embodiments can be implemented.In a case where the carrier frequency fc is set to the first frequency fL, when an affirmative determination is made in step S10ofFIG.32, the carrier frequency fc may be gradually changed from the first frequency fL to the second frequency fH.

Further, in a case where the carrier frequency fc is set to the second frequency fH, when a negative determination is made in step S10, the carrier frequency fc may be gradually changed from the second frequency fH to the first frequency fL.A switch operation signal may be generated by space vector modulation (SVM) control instead of PWM control. Even in this case, the above-mentioned change in switching frequency can be applied.

Ninth Modification

In each of the above embodiments, two pairs of conductors of each phase constituting the conductor group81are connected in parallel as illustrated inFIG.33(a).FIG.33(a)is a diagram illustrating the electrical connection of first and second conductors88aand88b, which are two pairs of conductors. Here, as an alternative to the configuration illustrated inFIG.33(a), as illustrated inFIG.33(b), the first and second conductors88aand88bmay be connected in series.

Further, three or more pairs of multilayer conductors may be laminated and arranged in the radial direction.FIG.34illustrates a configuration in which first to fourth conductors88ato88d, which are four pairs of conductors, are laminated and arranged. The first to fourth conductors88ato88dare arranged in the radial direction in the order of the first, second, third, and fourth conductors88a,88b,88c, and88dfrom the side closer to the stator core52.

Here, as illustrated inFIG.33(c), the third and fourth conductors88cand88dare connected in parallel, the first conductor88amay be connected to one end of the parallel connection body, and the second conductor88bmay be connected to the other end. When connected in parallel, the current density of the conductors connected in parallel can be reduced, and heat generation during energization can be suppressed. Therefore, in the configuration in which the tubular stator winding is assembled to the housing (unit base61) in which the cooling water passage74is formed, the first and second conductors88aand88bthat are not connected in parallel are arranged on the stator core52side that abuts on the unit base61, and the third and fourth conductors88cand88dthat are connected in parallel are arranged on the opposite-to-stator core side. As a result, the cooling performance of each of the conductors88ato88din the multilayer conductor structure can be equalized.

Moreover, the radial thickness dimension of the conductor group81composed of the first to fourth conductors88ato88dshould be smaller than the circumferential width dimension for one phase in one magnetic pole.

Tenth Modification

The rotating electric machine10may have an inner rotor structure (adduction structure). In this case, for example, in the housing30, it is preferable that the stator50is provided on the radially outside and the rotor40is provided on the radially inside. Further, it is preferable that the inverter unit60is provided on one side or both sides of both ends of the stator50and the rotor40in the axial direction.FIG.35is a cross-sectional view of the rotor40and the stator50, andFIG.36is a view illustrating a part of the rotor40and the stator50illustrated inFIG.35in an enlarged manner.

The configurations ofFIGS.35and36, which are premised on an inner rotor structure, have the same configurations as those ofFIGS.8and9except that the rotor40and stator50are reversed in and out of the radial direction. Briefly, the stator50has a stator winding51having a flat conductor structure and a stator core52having no teeth. The stator winding51is assembled radially inside the stator core52. The stator core52has one of the following configurations, as in the case of the outer rotor structure.

(A) In the stator50, an interconductor member is provided between each conductor section in the circumferential direction, and as the interconductor member, a magnetic material having a relation of Wt*Bs≤Wm*Br is used when the circumferential width dimension of the interconductor member at one magnetic pole is Wt, the saturation magnetic flux density of the interconductor member is Bs, the circumferential width dimension of the magnet unit at one magnetic pole is Wm, and the residual magnetic flux density of the magnet unit is Br.

(B) In the stator50, an interconductor member is provided between each conductor section in the circumferential direction, and a non-magnetic material is used as the interconductor member.

(C) The stator50has a configuration in which no interconductor member is provided between each conductor section in the circumferential direction.

Further, the same applies to the magnets91and92of the magnet unit42. That is, the magnet unit42is composed with the use of the magnets91and92in which, the orientation was made in such a manner that, on the side of the d-axis, which is the center of the magnetic pole, the direction of the axis of easy magnetization is parallel to the d-axis as compared with the side of the q-axis, which is the magnetic pole boundary. Details such as the magnetization directions of the magnets91and92are as described above. It is also possible to use the annular magnet95(seeFIG.30) in the magnet unit42.

FIG.37is a vertical cross-sectional view of the rotating electric machine10in the case of an inner rotor type, which is a figure corresponding toFIG.2described above. Differences from the configuration ofFIG.2will be briefly described. InFIG.37, an annular stator50is fixed to the inside of the housing30, and a rotor40is rotatably provided inside the stator50with a predetermined air gap therebetween. Similarly toFIG.2, the respective bearings21and22are arranged unevenly on either side in the axial direction with respect to the axial center of the rotor40, whereby the rotor40is cantilevered and supported. Further, the inverter unit60is provided inside the magnet holder41of the rotor40.

FIG.38illustrates another configuration of the rotating electric machine10having an inner rotor structure. InFIG.38, the rotating shaft11is rotatably supported by the bearings21and22in the housing30, and the rotor40is fixed to the rotating shaft11. Similarly to the configuration illustrated inFIG.2or the like, the respective bearings21and22are arranged unevenly on either side in the axial direction with respect to the axial center of the rotor40. The rotor40has the magnet holder41and the magnet unit42.

The rotating electric machine10ofFIG.38is different from the rotating electric machine10ofFIG.37in that the inverter unit60is not provided radially inside the rotor40. The magnet holder41is connected to the rotating shaft11at a position radially inside the magnet unit42. Further, the stator50has the stator winding51and the stator core52, and is attached to the housing30.

Eleventh Modification

Another configuration as a rotating electric machine having an inner rotor structure will be described below.FIG.39is an exploded perspective view of a rotating electric machine200, andFIG.40is a side sectional view of the rotating electric machine200. Here, the up-down direction is illustrated with reference to the states ofFIGS.39and40.

As illustrated inFIGS.39and40, the rotating electric machine200includes a stator203having an annular stator core201and a multi-phase stator winding202, and a rotor204rotatably arranged inside the stator core201. The stator203corresponds to an armature and the rotor204corresponds to a field magnet. The stator core201is composed by laminating a large number of silicon steel plates, and a stator winding202is attached to the stator core201. Although not illustrated, the rotor204has a rotor core and a plurality of permanent magnets as a magnet unit. The rotor core is provided with a plurality of magnet insertion holes at equal intervals in the circumferential direction. Each of the magnet insertion holes is equipped with a permanent magnet magnetized in such a manner that the magnetization direction changes alternately for each adjacent magnetic pole. Moreover, the permanent magnet of the magnet unit may have a Halbach array as described with reference toFIG.23or a similar configuration. Alternatively, it is preferable that the permanent magnet of the magnet unit has polar anisotropy characteristics such as that described with reference toFIG.9andFIG.30, in which the orientation direction (magnetization direction) extends in an arc shape between the d-axis which is the center of the magnetic pole and the q-axis which is the magnetic pole boundary.

Here, the stator203preferably has any of the following configurations.

(A) In the stator203, an interconductor member is provided between each conductor section in the circumferential direction, and as the interconductor member, a magnetic material having a relation of Wt*Bs≤Wm*Br is used when the width dimension of the interconductor member in the circumferential direction at one magnetic pole is Wt, the saturation magnetic flux density of the interconductor member is Bs, the width dimension in the circumferential direction of the magnet unit at one magnetic pole is Wm, and the residual magnetic flux density of the magnet unit is Br.

(B) In the stator203, an interconductor member is provided between each conductor section in the circumferential direction, and a non-magnetic material is used as the interconductor member.

(C) The stator203has a configuration in which no interconductor member is provided between each conductor section in the circumferential direction.

Further, in the rotor204, the magnet unit is composed with the use of a plurality of magnets in which, the orientation was made in such a manner that, on the side of the d-axis, which is the center of the magnetic pole, the direction of the axis of easy magnetization is parallel to the d-axis as compared with the side of the q-axis, which is the magnetic pole boundary.

An annular inverter case211is provided on one end side of the rotating electric machine200in the axial direction. The inverter case211is arranged in such a manner that the lower surface of the case is in contact with the upper surface of the stator core201. Inside the inverter case211, a plurality of power modules212constituting the inverter circuit, a smoothing capacitor213that suppresses voltage/current pulsation (ripple) generated by the switching operation of the semiconductor switching element, a control board214having a control unit, a current sensor215that detects a phase current, and a resolver stator216that is a rotation speed sensor of the rotor204are provided. The power module212has an IGBT and a diode which are semiconductor switching elements.

On the periphery of the inverter case211, a power connector217connected to the DC circuit of the battery mounted on a vehicle, and a signal connector218used for transferring various signals between the rotating electric machine200side and the vehicle side control device are provided. The inverter case211is covered with a top cover219. The direct current power from a vehicle-mounted battery is input via the power connector217, converted into alternate current by switching of the power module212, and sent to the stator winding202of each phase.

On both sides of the stator core201in the axial direction, on the side opposite to the inverter case211, a bearing unit221that rotatably holds the rotating shaft of the rotor204and an annular rear case222that houses the bearing unit221are provided. The bearing unit221has, for example, a pair of bearings and is arranged unevenly on either side in the axial direction with respect to the axial center of the rotor204. However, a plurality of bearings in the bearing unit221may be provided in a dispersed manner on both sides of the stator core201in the axial direction, and the rotating shafts may be supported from both sides by those respective bearings. The rotating electric machine200can be mounted on the vehicle side by bolting and fixing the rear case222to a mounting section such as a gear case or a transmission of the vehicle.

A cooling flow path211afor flowing a refrigerant is formed in the inverter case211. The cooling flow path211ais formed by closing a space recessed in an annular shape from the lower surface of the inverter case211with the upper surface of the stator core201. The cooling flow path211ais formed so as to surround the coil end of the stator winding202. A module case212aof the power module212is inserted in the cooling flow path211a. Also in the rear case222, a cooling flow path222ais formed so as to surround the coil end of the stator winding202. The cooling flow path222ais formed by closing a space recessed in an annular shape from the upper surface of the rear case222with the lower surface of the stator core201.

Twelfth Modification

So far, the configuration embodied in the revolving-field type rotating electric machine has been described, but it is also possible to change this and embody it in the rotating armature type rotating electric machine.FIG.41illustrates the configuration of a rotating armature type rotating electric machine230.

In the rotating electric machine230ofFIG.41, bearings232are fixed to housings231aand231b, respectively, and a rotating shaft233is rotatably supported by the bearings232. The bearing232is, for example, an oil-impregnated bearing made by impregnating a porous metal with oil. A rotor234as an armature is fixed to the rotating shaft233. The rotor234has a rotor core235and a multi-phase rotor winding236fixed to the outer peripheral portion of the rotor core235. In the rotor234, the rotor core235has a slotless structure, and the rotor winding236has a flat conductor structure. That is, the rotor winding236has a flat structure in which the region for each phase is longer in the circumferential direction than in the radial direction.

Further, a stator237as a field magnet is provided radially outside the rotor234. The stator237has a stator core238fixed to the housing231aand a magnet unit239fixed to the inner peripheral side of the stator core238. The magnet unit239has a configuration including a plurality of magnetic poles having alternating polarities in the circumferential direction, and is configured similarly to the magnet unit42or the like described above, in which, the orientation was made in such a manner that the direction of the axis of easy magnetization is parallel to the d-axis on the d-axis side which is the center of the magnetic pole as compared with the q-axis side which is the magnetic pole boundary. The magnet unit239has an oriented sintered neodymium magnet, the intrinsic coercive force thereof is 400 [kA/m] or more, and the residual magnetic flux density is 1.0 [T] or more.

The rotating electric machine230of this modification is a 2-pole 3-coil brushed coreless motor, the rotor winding236is divided into three, and the magnet unit239has two poles. The number of poles and the number of coils of the brushed motor varies depending on the application, such as 2:3, 4:10, 4:21.

A commutator241is fixed to the rotating shaft233, and a plurality of brushes242are arranged on the radially outside thereof. The commutator241is electrically connected to the rotor winding236via a conductor243embedded in the rotating shaft233. A direct current flows in and out of the rotor winding236through these commutator241, brush242, and conductor243. The commutator241is appropriately divided in the circumferential direction in accordance with the number of phases of the rotor winding236. The brush242may be directly connected to a DC power source such as a storage battery via an electrical wiring, or may be connected to a DC power source via a terminal block or the like.

The rotating shaft233is provided with a resin washer244as a sealing material between the bearing232and the commutator241. The resin washer244suppresses the oil seeping out from the bearing232, which is an oil-impregnated bearing, from flowing out to the commutator241side.

Thirteenth Modification

In the stator winding51of the rotating electric machine10, each conductor wire82may have a plurality of insulating coatings inside and outside. For example, it is preferable to bundle a plurality of conductors (wires) with an insulating coating into one and cover the conductors with an outer layer coating to form the conductor wire82. In this case, the insulating coating of the wire constitutes the inner insulating coating, and the outer layer coating constitutes the outer insulating coating. Further, in particular, it is preferable that the insulating capability of the outer insulating coating among the plurality of insulating coatings on the conductor wire82is higher than the insulating capability of the inner insulating coating. Specifically, the thickness of the outer insulating coating is made thicker than the thickness of the inner insulating coating. For example, the thickness of the outer insulating coating is 100 μm, and the thickness of the inner insulating coating is 40 μm. Alternatively, a material having a lower dielectric constant than that of the inner insulating coating may be used as the outer insulating coating. At least one of these should be applied. Moreover, it is preferable that the wire is configured as an aggregate of a plurality of conductive materials.

By strengthening the insulation of the outermost layer of the conductor wire82as described above, it becomes suitable for use in a high voltage vehicle system. Further, the rotating electric machine10can be properly driven even in highlands where the atmospheric pressure is low.

Fourteenth Modification

In the conductor wire82having a plurality of insulating coatings inside and outside, at least one of the linear expansivity (linear expansion coefficient) and the adhesive strength may be different between the outer insulating coating and the inner insulating coating. The configuration of the conductor wire82in this modification is illustrated inFIG.42.

InFIG.42, the conductor wire82includes a plurality of (four in the figure) wires181, an outer layer coating182made of, for example, a resin (outer insulating coating), that surrounds the plurality of wires181, and an intermediate layer183(intermediate insulating coating) filled around each wire181in the outer layer coating182. The wire181has a conductive part181amade of a copper material and a conductor coating181b(inner insulating coating) made of an insulating material. When viewed as a stator winding, the outer layer coating182insulates the phases. Moreover, it is preferable that the wire181is configured as an aggregate of a plurality of conductive materials.

The intermediate layer183has a linear expansion coefficient higher than that of the conductor coating181bof the wire181and a linear expansion coefficient lower than that of the outer layer coating182. That is, in the conductor wire82, the linear expansion coefficient is higher toward the outside. Generally, the outer layer coating182has a linear expansion coefficient higher than that of the conductor coating181b, but by providing the intermediate layer183having an intermediate linear expansion coefficient between them, the intermediate layer183functions as a cushioning material, and simultaneous cracking on the outer layer side and the inner layer side can be prevented.

Further, in the conductor wire82, the conductive part181aand the conductor coating181bare adhered to each other in the wire181, and the conductor coating181band the intermediate layer183and the intermediate layer183and the outer layer coating182are adhered to each other, respectively, and the adhesive strength becomes weaker toward the outside of the conductor wire82in each of these adhered portions. That is, the adhesive strength of the conductive part181aand the conductor coating181bis weaker than the adhesive strength of the conductor coating181band the intermediate layer183and the adhesive strength of the intermediate layer183and the outer layer coating182. Further, comparing the adhesive strength of the conductor coating181band the intermediate layer183with the adhesive strength of the intermediate layer183and the outer layer coating182, it is preferable that the latter (outer side) is weaker or equivalent. Moreover, the magnitude of the adhesive strength between the coatings can be grasped from, for example, the tensile strength required when peeling off the two layers of coatings. By setting the adhesive strength of the conductor wire82as described above, it is possible to suppress cracking (co-cracking) on both the inner layer side and the outer layer side even if an internal/external temperature difference occurs due to heat generation or cooling.

Here, the heat generation and temperature change of the rotating electric machine mainly occur as copper loss produced from the conductive part181aof the wire181and iron loss generated from the inside of the iron core, and these two types of losses are transmitted from the conductive part181ain the conductor wire82or the outside of the conductor wire82, and the intermediate layer183does not have a heat source. In this case, the intermediate layer183has an adhesive force that can serve as a cushion for both of them, and thus simultaneous cracking can be prevented. Consequently, suitable use is possible even when used in fields with high withstand pressure or large temperature changes such as vehicle applications.

This is supplemented below. The wire181may be, for example, an enamel wire, and in such a case, it has a resin coating layer (conductor coating181b) such as PA, PI, and PAI. Further, it is desirable that the outer layer coating182outside the wire181is made of the same PA, PI, PAI, or the like, and has a large thickness. As a result, damage to the coating due to a difference in linear expansion coefficient is suppressed. Moreover, as the outer layer coating182, it is desirable to also use one with a dielectric constant smaller than PI and PAI, such as PPS, PEEK, fluorine, polycarbonate, silicon, epoxy, polyethylene naphthalate, and LCP, in addition to one made by thickening the aforementioned materials such as PA, PI, and PAI. With these resins, even if they are thinner than the PI and PAI coatings equivalent to the conductor coating181bor the thickness equivalent to the conductor coating181b, their insulating capability can be enhanced, and it is thereby possible to increase the occupancy ratio of the conductive part. In general, the resin has better insulation than the insulating coating of an enamel wire in terms of dielectric constant. As a matter of course, there are cases where the dielectric constant is deteriorated depending on the molding state and the mixture. Among them, PPS and PEEK are suitable as the outer layer coating of the second layer because their linear expansion coefficient is generally larger than that of the enamel coating but smaller than that of other resins.

Further, it is desirable that the adhesive strength between the two types of coatings (intermediate insulating coating and outer insulating coating) on the outside of the wire181and the enamel coating on the wire181is weaker than the adhesive strength between the copper wire and the enamel coating on the wire181. As a result, the phenomenon that the enamel coating and the aforementioned two types of coatings are destroyed at once is suppressed.

In a case where a water-cooled structure, a liquid-cooled structure, or an air-cooled structure is added to the stator, it is considered that thermal stress or impact stress is basically applied to the outer layer coating182first. However, even when the insulating layer of the wire181and the resin of the two types of coatings are different, thermal stress and impact stress can be reduced by providing a portion where the coatings are not adhered. That is, the aforementioned insulated structure is formed by providing a wire (enamel wire) and an space and arranging fluorine, polycarbonate, silicon, epoxy, polyethylene naphthalate, and LCP. In this case, it is desirable to adhere the outer layer coating and the inner layer coating with the use of an adhesive material made of epoxy or the like having a low dielectric constant and having a low linear expansion coefficient. By doing so, it is possible to suppress not only the mechanical strength but also the destruction of the coating due to friction caused by the vibration of the conductive part or the destruction of the outer layer coating due to a difference in the linear expansion coefficient.

As the outermost layer fixing which is generally the final process around the stator winding, which is responsible for mechanical strength, fixing, and the like for the conductor wire82having the above configuration, resins such as epoxy, PPS, PEEK, and LCP, which have good moldability and have properties such as dielectric constant and linear expansion coefficient similar to those of an enamel coating, are preferable.

Generally, resin potting with urethane or silicon is usually performed, but the linear expansion coefficient of the aforementioned resin is almost double that of other resins, and thermal stress capable of shearing the resin is generated. Therefore, it is not suitable for applications of 60V or higher where strict insulation regulations are used internationally. In this regard, according to the final insulation process for easily making by injection molding or the like using epoxy, PPS, PEEK, LCP or the like, each of the above requirements can be achieved.

Modifications other than the above are listed below.A distance DM between the surface of the magnet unit42on the armature side in the radial direction and the axial center of the rotor in the radial direction may be 50 mm or more. Specifically, a distance DM between, for example, the surface radially inside the magnet unit42(specifically, the first and second magnets91and92) illustrated inFIG.4and the axial center of the rotor40in the radial direction may be 50 mm or more.

As a rotating electric machine having a slotless structure, a small-scale one whose output is used for a model of several tens of watts to several hundreds of watts is known. In addition, the discloser of the present application does not grasp a case where the slotless structure is adopted in a large industrial rotating electric machine which generally exceeds 10 kW. The discloser of the present application examined the reason.

In recent years, mainstream rotating electric machines are roughly classified into the following four types. These rotating electric machines are a brushed motor, a basket type induction motor, a permanent magnet type synchronous motor, and a reluctance motor.

An exciting current is supplied to the brushed motor via the brush. Therefore, in the case of a brushed motor of a large machine, the brush becomes large and the maintenance becomes complicated. As a result, with the remarkable development of semiconductor technology, it has been replaced by brushless motors such as induction motors. Meanwhile, in the world of small motors, coreless motors are also supplied to the world because of their low inertia and economic advantages.

In the basket type induction motor, the principle is that torque is generated by receiving the magnetic field generated by the stator winding on the primary side by the iron core of the rotor on the secondary side and intensively passing an induced current through the basket type conductor to form a reaction magnetic field. Therefore, from the viewpoint of small size and high efficiency of equipment, it is not always a good idea to eliminate the iron core on both the stator side and the rotor side.

The reluctance motor is a motor that literally utilizes the reluctance change of the iron core, and it is not desirable to eliminate the iron core in principle.

In recent years, IPMs (that is, embedded magnet type rotors) have become the mainstream of permanent magnet type synchronous motors, and in large machines in particular, IPMs are often used unless there are special circumstances.

The IPM has a characteristic of having both magnet torque and reluctance torque, and is operated while the ratio of these torques is adjusted in a timely manner by inverter control. Therefore, the IPM is a small motor with excellent controllability.

According to the analysis of the discloser of the present application, the torque on the rotor surface that generates magnet torque and reluctance torque is drawn with the horizontal axis of the distance DM in the radial direction between the surface of the magnet unit on the armature side in the radial direction and the axial center of the rotor, that is, the radius of the stator core of a general inner rotor, as illustrated inFIG.43.

The potential of the magnet torque is determined by the magnetic field strength generated by the permanent magnet as indicated in the following equation (eq1), whereas the potential of the reluctance torque is determined by the inductance, especially, the magnitude of the q-axis inductance as indicated in the following equation (eq2).
Magnet torque=k·ψ·Iq(eq1)
Reluctance torque=k·(Lq−Ld)·Iq·Id(eq2)

Here, the magnetic field strength of the permanent magnet and the magnitude of the inductance of the winding were compared by the DM. The magnetic field strength generated by the permanent magnet, that is, the amount of magnetic flux ψ, is proportional to the total area of the permanent magnet on the surface facing the stator. If a cylindrical rotor is used, it will be the surface area of the cylinder. Strictly speaking, since there are N pole and S pole, it is proportional to the occupied area of half of the cylindrical surface. The surface area of a cylinder is proportional to the radius of the cylinder and the length of the cylinder. That is, if the cylinder length is constant, it is proportional to the radius of the cylinder.

On the other hand, an inductance Lq of the winding depends on the shape of the iron core but has low sensitivity, and is rather proportional to the square of the number of turns of the stator winding, and therefore the number of turns is highly dependent. Moreover, when μ is the magnetic permeability of the magnetic circuit, N is the number of turns, S is the cross-sectional area of the magnetic circuit, and δ is the effective length of the magnetic circuit, the inductance L=μ·N{circumflex over ( )}2*S/δ. Since the number of turns of the winding depends on the size of the winding space, in the case of a cylindrical motor, it depends on the winding space of the stator, that is, the slot area. As illustrated inFIG.44, since the slot shape is substantially quadrangular, the slot area is proportional to the product a*b of a length dimension a in the circumferential direction and a length dimension b in the radial direction.

The circumferential length dimension of the slot is proportional to the diameter of the cylinder because it increases as the diameter of the cylinder increases. The radial length dimension of the slot is exactly proportional to the diameter of the cylinder. That is, the slot area is proportional to the square of the diameter of the cylinder. Further, as can be seen from the above equation (eq2), since the reluctance torque is proportional to the square of the stator current, the performance of the rotating electric machine is determined by how large the current can flow, and that performance depends on the slot area of the stator. From the above, if the length of the cylinder is constant, the reluctance torque is proportional to the square of the diameter of the cylinder. Based on this,FIG.43is a diagram plotting the relation between the magnet torque and the reluctance torque and DM.

As illustrated inFIG.43, the magnet torque increases linearly with respect to the DM, and the reluctance torque increases quadratically with respect to the DM. It can be seen that the magnet torque is dominant when the DM is relatively small, and the reluctance torque is dominant as the stator core radius increases. The discloser of the present application has concluded that the intersection of the magnet torque and the reluctance torque inFIG.43is approximately in the vicinity of the stator core radius=50 mm under a predetermined condition. That is, it is difficult to eliminate the iron core in a 10 kW class motor whose stator core radius sufficiently exceeds 50 mm because it is the current mainstream to utilize reluctance torque, and it is presumed that this is one of the reasons why the slotless structure is not adopted in the field of large machines.

In the case of a rotating electric machine in which an iron core is used as a stator, magnetic saturation of the iron core is always an issue. In particular, in a radial gap type rotating electric machine, the vertical cross-sectional shape of the rotating shaft is a fan shape per magnetic pole, the magnetic path width becomes narrower toward the inner peripheral side of the equipment, and the inner circumference side dimension of the teeth portion forming the slot determines the performance limit of the rotating electric machine. No matter how high-performance permanent magnets are used, if magnetic saturation occurs in this portion, the performance of the permanent magnets cannot be fully brought out. In order not to generate magnetic saturation in this portion, the inner circumference must be designed to be large, resulting in an increase in the size of the equipment.

For example, in a distributed winding rotating electric machine, in the case of a three-phase winding, the magnetic flux is shared by three to six teeth per magnetic pole, but the magnetic flux tends to concentrate on the teeth in the front in the circumferential direction, and thus the magnetic flux does not flow evenly to the three to six teeth. In this case, while the magnetic flux flows intensively through some (for example, one or two) teeth, the teeth that are magnetically saturated with the rotation of the rotor also move in the circumferential direction. This also causes slot ripple.

From the above, in a rotating electric machine having a slotless structure in which the DM is 50 mm or more, it is desired to abolish the teeth in order to eliminate magnetic saturation. However, when the teeth are removed, the magnetic resistance of the magnetic circuit in the rotor and the stator increases, and the torque of the rotating electric machine decreases. The reason for the increase in magnetic resistance is, for example, that the air gap between the rotor and the stator becomes large. Therefore, in the above-mentioned rotating electric machine having a slotless structure in which the DM is 50 mm or more, there is room for improvement in increasing the torque. Consequently, there is a great merit of applying the above-mentioned configuration capable of increasing the torque to the above-mentioned rotating electric machine having a slotless structure in which the DM is 50 mm or more.

Moreover, with regard to not only the rotating electric machine having an outer rotor structure but also the rotating electric machine having an inner rotor structure may have a distance DM of 50 mm or more in the radial direction between the surface of the magnet unit on the armature side in the radial direction and the axial center of the rotor.In the stator winding51of the rotating electric machine10, the straight section83of the conductor wire82may be provided in a single layer in the radial direction. Further, when the straight section83is arranged in a plurality of layers inside and outside the radial direction, the number of layers may be arbitrary, and may be provided in three layers, four layers, five layers, six layers, and the like.For example, in the configuration ofFIG.2, the rotating shaft11is provided so as to protrude to both one end side and the other end side of the rotating electric machine10in the axial direction, but this may be changed, and the rotating shaft11may be configured to protrude only to one end side. In this case, the rotating shaft11may be provided so as to extend outward in the axial direction, with a portion that is cantilevered and supported by the bearing unit20as an end. In this configuration, since the rotating shaft11does not protrude inside the inverter unit60, the internal space of the inverter unit60, specifically the internal space of the tubular section71, can be used more widely.In the rotating electric machine10having the above configuration, in the bearings21and22, non-conductive grease is used, but this may be changed, and conductive grease may be used in the bearings21and22. For example, conductive grease containing metal particles, carbon particles, or the like is used.As a configuration for rotatably supporting the rotating shaft11, bearings may be provided at two locations on one end side and the other end side in the axial direction of the rotor40. In this case, in the configuration ofFIG.1, it is preferable that bearings are provided at two locations on one end side and the other end side with the inverter unit60therebetween.In the rotating electric machine10having the above configuration, in the rotor40, the intermediate section45of the magnet holder41has the inner shoulder section49aand the annular outer shoulder section49b. However, these shoulder sections49aand49bmay be eliminated to have a flat surface.In the rotating electric machine10having the above configuration, the conductor82ais configured as an aggregate of a plurality of wires86in the conductor wire82of the stator winding51, but this may be changed, and a square conductor having a rectangular cross section may be used as the conductor wire82. Further, as the conductor wire82, a round conductor having a circular cross section or an elliptical cross section may be used.In the rotating electric machine10having the above configuration, the inverter unit60is provided radially inside the stator50, but instead of this, the inverter unit60may not be provided radially inside the stator50. In this case, it is possible to set an internal region inside the stator50in the radial direction as a space. Further, it is possible to arrange parts different from the inverter unit60in the internal region.The rotating electric machine10having the above configuration may not include the housing30. In this case, for example, the rotor40, the stator50, and the like may be held in a part of the wheel or other vehicle parts.

Embodiment as an In-Wheel Motor for a Vehicle

Next, an embodiment in which the rotating electric machine is provided integrally with the wheels of a vehicle as an in-wheel motor will be described.FIG.45is a perspective view illustrating a wheel400having an in-wheel motor structure and its peripheral structure,FIG.46is a vertical cross-sectional view of the wheel400and its peripheral structure, andFIG.47is an exploded perspective view of the wheel400. Each of these figures is a perspective view of the wheel400as viewed from the inside of the vehicle. Moreover, in the vehicle, the in-wheel motor structure of the present embodiment can be applied in various forms. For example, in a vehicle having two wheels in front of and behind the vehicle, it is possible to apply the in-wheel motor structure of the present embodiment to the two wheels on the front side of the vehicle, the two wheels on the rear side of the vehicle, or the four wheels on the front and rear of the vehicle. However, it can also be applied to a vehicle in which at least one of the front and rear of the vehicle has one wheel. Moreover, the in-wheel motor is an application example as a vehicle drive unit.

As illustrated inFIGS.45to47, the wheel400includes, for example, a tire401which is a well-known pneumatic tire, a wheel402fixed to the inner peripheral side of the tire401, and a rotating electric machine500fixed to the inner peripheral side of the wheel402. The rotating electric machine500has a fixing section which is a section including a stator and a rotation section which is a section including a rotor. The fixing section is fixed to the vehicle body side, and the rotation section is fixed to the wheel402. The rotation of the rotation section causes the tire401and the wheel402to rotate. Moreover, the detailed configuration of the rotating electric machine500including the fixing section and the rotation section will be described below.

Further, as peripheral devices, a suspension device that holds the wheel400with respect to a vehicle body (not illustrated), a steering device that changes the direction of the wheels400, and a braking device that brakes the wheel400are attached to the wheel400.

The suspension device is an independent suspension type suspension, and any type such as a trailing arm type, a strut type, a wishbone type, and a multi-link type can be applied. In the present embodiment, as the suspension device, a lower arm411is provided so as to extend toward the center side of the vehicle body, and a suspension arm412and a spring413are provided so as to extend in the up-down direction. The suspension arm412may be configured as, for example, a shock absorber. However, detailed illustration is omitted. The lower arm411and the suspension arm412are respectively connected to the vehicle body side and to a disk-shaped base plate405fixed to the fixing section of the rotating electric machine500. As illustrated inFIG.46, the lower arm411and the suspension arm412are supported on the rotating electric machine500side (base plate405side) by support shafts414and415in a coaxial state with each other.

Further, as the steering device, for example, a rack & pinion type structure, a ball & nut type structure, a hydraulic power steering system, and an electric power steering system can be applied. In the present embodiment, a rack device421and a tie rod422are provided as steering devices, and the rack device421is connected to the base plate405on the rotating electric machine500side via the tie rod422. In this case, when the rack device421operates with the rotation of a steering shaft (not illustrated), the tie rod422moves in the right-left direction of the vehicle. As a result, the wheel400rotates about the support shafts414and415of the lower arm411and the suspension arm412, and the wheel direction is changed.

As the braking device, it is preferable to apply a disc brake or a drum brake. In the present embodiment, as the braking device, a disc rotor431fixed to a rotating shaft501of the rotating electric machine500and a brake caliper432fixed to the base plate405on the rotating electric machine500side are provided. In the brake caliper432, brake pads are operated by oil pressure or the like, and when the brake pads are pressed against the disc rotor431, a braking force due to friction is generated and the rotation of the wheel400is stopped.

Further, the wheel400is attached with a housing duct440that houses an electric wiring H1extending from the rotating electric machine500and a cooling pipe H2. The housing duct440extends from the end of the rotating electric machine500on the fixing section side along the end face of the rotating electric machine500and is provided so as to avoid the suspension arm412, and is fixed to the suspension arm412in that state. As a result, the connection portion of the housing duct440in the suspension arm412has a fixed positional relation with the base plate405. Therefore, it is possible to suppress the stress caused by the vibration of the vehicle in the electric wiring H1and the cooling pipe H2. Moreover, the electrical wiring H1is connected to an in-vehicle power supply unit and an in-vehicle ECU (not illustrated), and the cooling pipe H2is connected to a radiator (not illustrated).

Next, the configuration of the rotating electric machine500used as an in-wheel motor will be described in detail. In the present embodiment, an example in which the rotating electric machine500is applied to an in-wheel motor is indicated. The rotating electric machine500has excellent operating efficiency and output as compared with the motor of a vehicle drive unit having a speed reducer as in the prior art. That is, if the rotating electric machine500is adopted in an application in which a practical price can be achieved by reducing the cost as compared with the prior art, it may be used as a motor for applications other than the vehicle drive unit. Even in such a case, it exhibits excellent performance as when applied to an in-wheel motor. Moreover, the operating efficiency refers to an index used during a test in a driving mode that derives the fuel efficiency of a vehicle.

The outline of the rotating electric machine500is illustrated inFIGS.48to51.FIG.48is a side view of the rotating electric machine500as viewed from the protruding side (inside the vehicle) of the rotating shaft501,FIG.49is a vertical cross-sectional view of the rotating electric machine500(cross-sectional view taken along a line49-49ofFIG.48),FIG.50is a cross-sectional view of the rotating electric machine500(a cross-sectional view taken along a line50-50ofFIG.49), andFIG.51is an exploded cross-sectional view of the components of the rotating electric machine500. In the following description, inFIG.51, the direction in which the rotating shaft501extends outward of the vehicle body is the axial direction, the direction extending radially from the rotating shaft501is the radial direction, and inFIG.48, both of the two directions extending in a circumferential shape from any point other than the center of rotation of the rotating portion on the center line drawn to form a cross section49passing through the center of the rotating shaft501, in other words, the center of rotation of the rotating portion are defined as the circumferential directions. In other words, the circumferential direction may be either a clockwise direction starting from an arbitrary point on the cross section49or a counterclockwise direction. Further, in the vehicle-mounted state, the right side is the outside of the vehicle and the left side is the inside of the vehicle inFIG.49. In other words, in the vehicle-mounted state, a rotor510which will be described below is arranged outward of the vehicle body with respect to a rotor cover670.

The rotating electric machine500according to the present embodiment is an outer rotor type surface magnet type rotating electric machine. The rotating electric machine500includes, roughly, a rotor510, a stator520, an inverter unit530, a bearing560, and the rotor cover670. Each of these members is arranged coaxially with the rotating shaft501integrally provided on the rotor510and is assembled in the axial direction in a predetermined order to form the rotating electric machine500.

In the rotating electric machine500, the rotor510and the stator520each have a cylindrical shape, and are arranged so as to face each other with an air gap therebetween. As the rotor510rotates integrally with the rotating shaft501, the rotor510rotates on the radial outside of the stator520. The rotor510corresponds to a “field magnet and the stator520corresponds to an “armature”.

The rotor510has a substantially cylindrical rotor carrier511and an annular magnet unit512fixed to the rotor carrier511. The rotating shaft501is fixed to the rotor carrier511.

The rotor carrier511has a cylindrical section513. A magnet unit512is attached to the inner peripheral surface of the cylindrical section513. That is, the magnet unit512is provided in a state of being surrounded by the cylindrical section513of the rotor carrier511from the outside in the radial direction. Further, the cylindrical section513has a first end and a second end facing each other in the axial direction thereof. The first end is located in the direction outside the vehicle body, and the second end is located in the direction in which the base plate405is present. In the rotor carrier511, an end plate514is continuously provided at the first end of the cylindrical section513. That is, the cylindrical section513and the end plate514have an integral structure. The second end of the cylindrical section513is open. The rotor carrier511is formed of, for example, a steel plate cold commercial having sufficient mechanical strength (SPCC or SPHC thicker than SPCC), forging steel, carbon fiber reinforced plastic (CFRP), or the like.

The axial length of the rotating shaft501is longer than the axial dimension of the rotor carrier511. In other words, the rotating shaft501protrudes toward the open end side (inward direction of the vehicle) of the rotor carrier511, and the above-mentioned brake device or the like is attached to the protruding side end.

A through hole514ais formed in the central portion of the end plate514of the rotor carrier511. The rotating shaft501is fixed to the rotor carrier511in a state of being inserted into the through hole514aof the end plate514. The rotating shaft501has a flange502extending in a direction intersecting with (orthogonal to) the axial direction at a portion where the rotor carrier511is fixed, and in a state where the flange and the surface of the end plate514outside the vehicle are surface-joined, the rotating shaft501is fixed to the rotor carrier511. Moreover, in the wheel400, the wheel402is fixed with the use of a fastener such as a bolt erected from the flange502of the rotating shaft501toward the outside of the vehicle.

Further, the magnet unit512is composed of a plurality of permanent magnets arranged in such a manner that the polarities alternate along the circumferential direction of the rotor510. As a result, the magnet unit512has a plurality of magnetic poles in the circumferential direction. The permanent magnet is fixed to the rotor carrier511by, for example, adhesion. The magnet unit512has the configuration described as the magnet unit42with reference toFIGS.8and9of the first embodiment, and as a permanent magnet, has an intrinsic coercive force of 400 [kA/m] or more and is composed with a sintered neodymium magnet having a residual magnetic flux Br of 1.0 [T] or more.

Similarly to the magnet unit42inFIG.9or the like, the magnet unit512has a first magnet91and a second magnet92, which are respectively polar anisotropic magnets and have different polarities from each other. As described with reference toFIGS.8and9, each of the magnets91and92has a different direction of the axis of easy magnetization on the d-axis side (the portion located near the d-axis) and the q-axis side (the portion located near the q-axis), and on the d-axis side, the direction of the axis of easy magnetization is close to the direction parallel to the d-axis, and on the q-axis side, the direction of the easy magnetization axis is close to the direction orthogonal to the q-axis. In addition, an arc-shaped magnet magnetic path is formed by the orientation according to the direction of the axis of easy magnetization. Moreover, in each of the magnets91and92, the axis of easy magnetization may be oriented parallel to the d-axis on the d-axis side, and the axis of easy magnetization may be oriented orthogonal to the q-axis on the q-axis side. In short, the magnet unit512is configured, in which the orientation was made in such a manner that the direction of the axis of easy magnetization is parallel to the d-axis on the d-axis side which is the center of the magnetic pole as compared with the q-axis side which is the magnetic pole boundary.

According to the magnets91and92, the magnet magnetic flux on the d-axis is strengthened and the change in magnetic flux near the q-axis is suppressed. As a result, the magnets91and92in which the change in surface magnetic flux from the q-axis to the d-axis at each magnetic pole is gentle can be preferably achieved. As the magnet unit512, the configurations of the magnet unit42illustrated inFIGS.22and23and the configuration of the magnet unit42illustrated inFIG.30can also be used.

Moreover, the magnet unit512may have a rotor core (back yoke) formed by laminating a plurality of electromagnetic steel sheets in the axial direction on the side of the cylindrical section513of the rotor carrier511, that is, on the outer peripheral surface side. That is, it is also possible to provide a rotor core on the radial inside of the cylindrical section513of the rotor carrier511and to provide the permanent magnets (magnets91and92) on the radial inside of the rotor core.

As illustrated inFIG.47, the cylindrical section513of the rotor carrier511is formed with a recess513ain a direction extending in the axial direction at predetermined intervals in the circumferential direction. The recess513ais formed by, for example, press working, and as illustrated inFIG.52, a protrusion513bis formed on the inner peripheral surface side of the cylindrical section513at a position on the back side of the recess513a. On the other hand, on the outer peripheral surface side of the magnet unit512, a recess512ais formed in accordance with the protrusion513bof the cylindrical section513, and the protrusion513bof the cylindrical section513enters the recess512a, whereby the displacement in the circumferential direction of the magnet unit512is suppressed. That is, the protrusion513bon the rotor carrier511side functions as the rotation stop section of the magnet unit512. Moreover, the method for forming the protrusion513bmay be any method other than press working.

InFIG.52, the direction of the magnet magnetic path in the magnet unit512is indicated by an arrow. The magnet magnetic path extends in an arc shape so as to straddle the q-axis which is the magnetic pole boundary, and is in a direction parallel to or close to parallel to the d-axis on the d-axis which is the center of the magnetic pole. The magnet unit512is formed with a recess512bat positions corresponding to the q-axis on the inner peripheral surface side thereof. In this case, in the magnet unit512, the magnet magnetic path length differs between the side closer to the stator520(lower side in the figure) and the side farther from the stator520(upper side in the figure), the magnet magnetic path length is shorter on the side closer to the stator520, and the recess512bis formed at a position where the magnet magnetic path length is the shortest. That is, in consideration of the fact that it is difficult for the magnet unit512to generate a sufficient magnet magnetic flux in a place where the magnet magnetic path length is short, the magnet is omitted in a place where the magnet magnetic flux is weak.

Here, an effective magnetic flux density Bd of the magnet becomes higher as the length of the magnetic circuit passing through the inside of the magnet becomes longer. Further, a permeance coefficient Pc and the effective magnetic flux density Bd of the magnet are in a relation that the higher one is, the higher the other is. According to the configuration ofFIG.52, the amount of magnets can be reduced while suppressing a decrease in the permeance coefficient Pc which is an index of the height of the effective magnetic flux density Bd of the magnet. Moreover, in a B-H coordinates, the intersection of the permeance straight line and the demagnetization curve according to the shape of the magnet is the operating point, and the magnetic flux density at the operating point is the effective magnetic flux density Bd of the magnet. The rotating electric machine500of the present embodiment has a configuration in which the amount of iron in the stator520is reduced, and in such a configuration, a method for setting a magnetic circuit straddling the q-axis is extremely effective.

Further, the recess512bof the magnet unit512can be used as an air passage extending in the axial direction. Therefore, it is also possible to improve the air cooling performance.

Next, the configuration of the stator520will be described. The stator520has a stator winding521and a stator core522.FIG.53is a perspective view illustrating the stator winding521and the stator core522in an exploded manner.

The stator winding521is composed of a plurality of phase windings formed by winding in a substantially tubular shape (annular shape), and the stator core522as a base member is assembled radially inside the stator winding521. In the present embodiment, a U-phase, V-phase, and W-phase windings are used, and the stator winding521is thereby configured as a three-phase winding. Each phase winding is composed of two inner and outer layers of conductors523in the radial direction. Similarly to the stator50described above, the stator520is characterized by having a slotless structure and a flat conductor structure of the stator winding521, and has the same configuration as or a configuration similar to that of the stator50illustrated inFIGS.8to16.

The configuration of the stator core522will be described. Similarly to the stator core52described above, the stator core522has a cylindrical shape in which a plurality of electromagnetic steel sheets are laminated in the axial direction and has a predetermined thickness in the radial direction, and the stator winding521is assembled on the radially outside that is the rotor510side in the stator core522. The outer peripheral surface of the stator core522has a curved shape without unevenness, and in a state where the stator winding521is assembled, the conductor523constituting the stator winding521are arranged side by side in the circumferential direction on the outer peripheral surface of the stator core522. The stator core522functions as a back core.

The stator520may use any of the following (A) to (C).

(A) In the stator520, an interconductor member is provided between each conductor523in the circumferential direction, and as the interconductor member, a magnetic material having a relation of Wt*Bs≤Wm*Br is used when the width dimension of the interconductor member in the circumferential direction at one magnetic pole is Wt, the saturation magnetic flux density of the interconductor member is Bs, the width dimension in the circumferential direction of the magnet unit512at one magnetic pole is Wm, and the residual magnetic flux density of the magnet unit512is Br.

(B) In the stator520, an interconductor member is provided between each conductor523in the circumferential direction, and a non-magnetic material is used as the interconductor member.

(C) The stator520has a configuration in which no interconductor member is provided between each conductor523in the circumferential direction.

According to such configuration of the stator520, the inductance can be reduced as compared with a rotating electric machine having a general teeth structure in which teeth (iron core) for establishing a magnetic path is provided between respective conductor sections as a stator winding. Specifically, the inductance can be reduced to 1/10 or less. In this case, since the impedance decreases as the inductance decreases, the output power with respect to the input power of the rotating electric machine500can be increased, which thus can contribute to the increase in torque. Further, it is possible to provide a rotating electric machine with a higher output than a rotating electric machine using an embedded magnet type rotor that outputs torque utilizing the voltage of the impedance component (in other words, utilizing reluctance torque).

In the present embodiment, the stator winding521is integrally molded together with the stator core522by a molding material (insulating member) made of resin or the like, and the molding material is interposed between the respective conductors523arranged in the circumferential direction. According to such a configuration, the stator520of the present embodiment corresponds to the configuration of (B) among the above (A) to (C). Further, the respective conductors523adjacent to each other in the circumferential direction are arranged in such a manner that the end faces in the circumferential direction are in contact with each other or are arranged close to each other at a minute interval, and the configuration of the above (C) may be adopted in view of this configuration. Moreover, in a case where the configuration (A) is adopted, it is preferable that a protrusion is provided on the outer peripheral surface of the stator core522, in accordance with the direction of the conductor523in the axial direction, that is, in accordance with the skew angle of the stator winding521having a skew structure, for example.

Next, the configuration of the stator winding521will be described with reference toFIG.54.FIG.54is a front view illustrating the stator winding521developed in a plane,FIG.54(a)illustrates each conductor523located in the outer layer in the radial direction, andFIG.54(b)illustrates each conductor523located in the inner layer in the radial direction.

The stator winding521is formed being wound in an annular shape by distributed winding. In the stator winding521, the conductor material is wound around the inner and outer two layers in the radial direction, and the respective conductors523on the inner layer side and the outer layer side are skewed in different directions (SeeFIGS.54(a) and54(b)). The respective conductors523are insulated from each other. It is preferable that the conductor523is configured as an aggregate of a plurality of wires86(seeFIG.13). Further, for example, two conductors523having the same phase and the same energizing direction are provided side by side in the circumferential direction. In the stator winding521, one conductor section having the same phase is composed of each conductor523having two layers in the radial direction and two conductors in the circumferential direction (that is, a total of four conductors), and the conductor section is provided one per magnetic pole.

It is desirable that the radial thickness dimension of the conductor section be smaller than the circumferential width dimension for one phase in one magnetic pole, whereby the stator winding521has a flat conductor structure. Specifically, for example, in the stator winding521, one conductor section having the same phase is preferably composed of each conductor523having two layers in the radial direction and four conductors in the circumferential direction (that is, a total of eight conductors). Alternatively, in the conductor cross section of the stator winding521illustrated inFIG.50, the circumferential width dimension is preferably larger than the radial thickness dimension. As the stator winding521, the stator winding51illustrated inFIG.12can also be used. However, in this case, it is necessary to secure a space in the rotor carrier511for housing the coil end of the stator winding.

In the stator winding521, the conductors523are arranged side by side in the circumferential direction, being tilted at a predetermined angle on a coil side525that overlaps the stator core522inside and outside the radial direction, and coil ends526on both sides, which are axially outer than the stator core522, are inverted (folded back) inward in the axial direction to form a continuous connection.FIG.54(a)illustrates a range of the coil side525and a range of the coil end526, respectively. The inner layer side conductor523and the outer layer side conductor523are connected to each other at the coil end526, and as a result, each time the conductor523is inverted in the axial direction at the coil end526(each time it is folded back), the conductor523is switched alternately between the inner layer side and the outer layer side. In short, the stator winding521has a configuration in which the inner and outer layers are switched in accordance with the reversal of the direction of the current in the respective conductors523that are continuous in the circumferential direction.

Further, in the stator winding521, two types of skews are applied in which the skew angles are different between the end regions that are both ends in the axial direction and the central region sandwiched between the end regions. That is, as illustrated inFIG.55, in the conductor523, a skew angle θs1 in the central region and a skew angle θs2 in the end region are different, and the skew angle θs1 is smaller than the skew angle θs2. In the axial direction, the end region is defined to include the coil side525. The skew angle θs1 and the skew angle θs2 are tilt angles at which each conductor523is tilted with respect to the axial direction. The skew angle θs1 in the central region may be set in an angle range appropriate for reducing the harmonic component of the magnetic flux generated by the energization of the stator winding521.

The skew angle of each conductor523in the stator winding521is made different between the central region and the end region, and the skew angle θs1 in the central region is made smaller than the skew angle θs2 in the end region, whereby the winding coefficient of the stator winding521can be increased while reducing the coil end526. In other words, the length of the coil end526, that is, the conductor length of the portion protruding in the axial direction from the stator core522, can be shortened while ensuring a desired winding coefficient. As a result, it is possible to improve the torque while downsizing the rotating electric machine500.

Here, an appropriate range as the skew angle θs1 in the central region will be described. When X conductors523are arranged in one magnetic pole in the stator winding521, it is conceivable that the Xth order harmonic component is generated by energization of the stator winding521. When the number of phases is S and the logarithm is m, X=2*S*m. The discloser of the present application focused on the fact that the Xth order harmonic component is a component that constitutes a composite wave of the X−1th order harmonic component and the X+1th order harmonic component, and therefore at least one of the X−1th order harmonic component or the X+1th order harmonic component is reduced, whereby the Xth order harmonic component can be reduced. Based on this focus, the discloser of the present application found that the skew angle θs1 is set within the angle range of “360°/(X+1) to 360°/(X−1)” in terms of the electrical angle, whereby the Xth harmonic component can be reduced.

For example, when S=3 and m=2, the skew angle θs1 is set within the angle range of “360°/13 to 360°/11” in order to reduce the harmonic component of the X=12th order. That is, the skew angle θs1 is preferably set at an angle within the range of 27.7° to 32.7°.

By setting the skew angle θs1 in the central region as described above, the magnet magnetic fluxes alternated at N and S poles can be positively interlinked in the central region, and the winding coefficient of the stator winding521can be increased.

The skew angle θs2 in the end region is larger than the skew angle θs1 in the central region described above. In this case, the angle range of the skew angle θs2 is “θs1<θs2<90°”.

Further, in the stator winding521, the inner layer side conductor523and the outer layer side conductor523are preferably connected by welding or adhesion between the ends of the respective conductors523, or are preferably connected by bending. In the stator winding521, the end of each phase winding is electrically connected to a power converter (inverter) via a bus bar or the like on one side (that is, one end side in the axial direction) of each coil end526on both sides in the axial direction. Therefore, here, the configuration in which the respective conductors are connected to each other at the coil end526will be described while distinguishing between the coil end526on the bus bar connection side and the coil end526on the opposite side.

The first configuration is such that each conductor523is connected at the coil end526on the bus bar connection side by welding, and each conductor523is connected at the coil end526on the opposite side by means other than welding. As the means other than welding, for example, a connection by bending a conductor material is conceivable. At the coil end526on the bus bar connection side, it is assumed that the bus bar is connected to the end of each phase winding by welding. Therefore, by connecting each conductor523at the same coil end526by welding, each welded portion can be handled in a series of processes, and work efficiency can be improved.

The second configuration is such that each conductor523is connected at the coil end526on the bus bar connection side by means other than welding, and each conductor523is connected at the coil end526on the opposite side by welding. In this case, if each conductor523is connected at the coil end526on the bus bar connection side by welding, the separation distance between the bus bar and the coil end526needs to be sufficient to avoid contact between the welded portion and the bus bar. However, with this configuration, the separation distance between the bus bar and the coil end526can be reduced. As a result, the regulation regarding the length of the stator winding521in the axial direction or the bus bar can be relaxed.

As the third configuration, each conductor523is connected at the coil ends526on both sides in the axial direction by welding. In this case, all of the conductor materials prepared before welding may have a short wire length, and the work efficiency can be improved by reducing the bending process.

As the fourth configuration, each conductor523is connected at the coil ends526on both sides in the axial direction by means other than welding. In this case, the portion of the stator winding521to be welded can be reduced as much as possible, and the concern that insulation peeling may occur in the welding process can be reduced.

Further, in the process of manufacturing the annular stator winding521, it is preferable to manufacture the strip-shaped windings arranged in a plane shape, and then to form the strip-shaped windings in an annular shape. In this case, it is preferable to weld the conductors at the coil end526in a state where the winding is a flat strip. When forming a flat strip-shaped winding in an annular shape, it is preferable to use a cylindrical jig having the same diameter as that of the stator core522and wind the strip-shaped winding around the cylindrical jig to form the strip-shaped winding in an annular shape. Alternatively, the strip-shaped winding may be wound directly around the stator core522.

Moreover, the configuration of the stator winding521can also be changed as follows.

For example, in the stator winding521illustrated inFIGS.54(a) and54(b), the skew angles of the central region and the end region may be the same.

Further, in the stator windings521illustrated inFIGS.54(a) and54(b), the ends of the in-phase conductors523adjacent to each other in the circumferential direction may be connected by a crossover section extending in a direction orthogonal to the axial direction.

The number of layers of the stator winding521may be 2*n layers (n is a natural number), and the stator winding521may have 4 layers, 6 layers, or the like in addition to the 2 layers.

Next, the inverter unit530, which is a power conversion unit, will be described. Here, the configuration of the inverter unit530will be described with reference toFIGS.56and57, which are exploded cross-sectional views of the inverter unit530. Moreover, inFIG.57, each member illustrated inFIG.56is illustrated as two subassemblies.

The inverter unit530includes an inverter housing531, a plurality of electric modules532assembled to the inverter housing531, and a bus bar module533that electrically connects each of the electric modules532.

The inverter housing531has a cylindrical outer wall member541, an inner wall member542having a cylindrical outer peripheral diameter smaller than that of the outer wall member541and arranged radially inside the outer wall member541, and a boss forming member543fixed to one end side in the axial direction of the inner wall member542. Each of these members541to543is preferably made of a conductive material, for example, made of carbon fiber reinforced plastic (CFRP). The inverter housing531is configured by combining the outer wall member541and the inner wall member542inside and outside the radial direction, and assembling the boss forming member543on one end side in the axial direction of the inner wall member542. The assembled state is the state illustrated inFIG.57.

The stator core522is fixed to the radial outside of the outer wall member541of the inverter housing531. As a result, the stator520and the inverter unit530are integrated.

As illustrated inFIG.56, the outer wall member541is formed with a plurality of recesses541a,541b, and541con the inner peripheral surface thereof, and the inner wall member542is formed with a plurality of recesses542a,542b, and542con the outer peripheral surface thereof. In addition, by the outer wall member541and the inner wall member542being assembled to each other, three hollow portions544a,544b, and544care formed between them (seeFIG.57). Of these, the central hollow portion544bis used as a cooling water passage545through which cooling water as a refrigerant flows. Further, a sealing material546is housed in the hollow portions544aand544con both sides of the hollow portion544b(cooling water passage545). The hollow portion544b(cooling water passage545) is sealed by the sealing material546. The cooling water passage545will be described in detail below.

Further, the boss forming member543is provided with a disc ring-shaped end plate547and a boss section548protruding from the end plate547toward the inside of the housing. The boss section548is provided in a hollow tubular shape. For example, as illustrated inFIG.51, the boss forming member543is fixed to the second end, of the first end of the inner wall member542in the axial direction and the second end on the protruding side (that is, inside the vehicle) of the rotating shaft501facing the first end. Moreover, in the wheels400illustrated inFIGS.45to47, the base plate405is fixed to the inverter housing531(more specifically, the end plate547of the boss forming member543).

The inverter housing531has a configuration having a double peripheral wall in the radial direction about the shaft center, and the outer peripheral wall of the double peripheral wall is formed by the outer wall member541and the inner wall member542, and the inner peripheral wall is formed by the boss section548. Moreover, in the following description, the outer peripheral wall formed by the outer wall member541and the inner wall member542is also referred to as an “outer peripheral wall WA1”, and the inner peripheral wall formed by the boss section548is also referred to as an “inner peripheral wall WA2”.

An annular space is formed in the inverter housing531between the outer peripheral wall WA1and the inner peripheral wall WA2, and a plurality of electric modules532are arranged side by side in the circumferential direction in the annular space. The electric module532is fixed to the inner peripheral surface of the inner wall member542by adhesion, screw tightening, or the like. In the present embodiment, the inverter housing531corresponds to a “housing member” and the electric module532corresponds to an “electric component”.

A bearing560is housed inside the inner peripheral wall WA2(boss section548), and the rotating shaft501is rotatably supported by the bearing560. The bearing560is a hub bearing that rotatably supports the wheel400at the center of the wheel. The bearing560is provided at a position overlapping with the rotor510, the stator520, and the inverter unit530in the axial direction. In the rotating electric machine500of the present embodiment, the magnet unit512can be made thinner in accordance with the orientation of the rotor510, and a slotless structure or a flat conductor structure is adopted in the stator520. Thus, it is possible to expand the hollow space radially inside the magnetic circuit section by reducing the radial thickness dimension of the magnetic circuit section. This makes it possible to arrange the magnetic circuit section, the inverter unit530, and the bearing560in a state of being stacked in the radial direction. The boss section548is a bearing holding section that holds the bearing560thereinside.

The bearing560is, for example, a radial ball bearing, and has a tubular inner ring561, an outer ring562having a diameter larger than that of the inner ring561and arranged radially outside the inner ring561, and a plurality of balls563arranged between the inner ring561and the outer ring562. The bearing560is fixed to the inverter housing531by assembling the outer ring562to the boss forming member543, and the inner ring561is fixed to the rotating shaft501. The inner ring561, outer ring562, and ball563are all made of a metallic material such as carbon steel.

Further, the inner ring561of the bearing560has a tubular section561athat houses the rotating shaft501and a flange561bthat extends in a direction intersecting with (orthogonal to) the axis direction from one end in the axial direction of the tubular section561a. The flange561bis a portion that comes into contact with the end plate514of the rotor carrier511from the inside, and in a state where the bearing560is assembled to the rotating shaft501, the rotor carrier511is held in a state of being sandwiched between the flange502of the rotating shaft501and the flange561bof the inner ring561. In this case, the flange502of the rotating shaft501and the flange561bof the inner ring561have the same angle of intersection with respect to the axial direction (both are right angles in the present embodiment), and the rotor carrier511is held in a state of being sandwiched between these respective flanges502and561b.

According to the configuration in which the rotor carrier511is supported from the inside by the inner ring561of the bearing560, the angle of the rotor carrier511with respect to the rotating shaft501can be maintained at an appropriate angle, and thus the parallelism of the magnet unit512with respect to the rotating shaft501can be kept good. As a result, even if the rotor carrier511is expanded in the radial direction, the resistance to vibration and the like can be enhanced.

Next, the electric module532housed in the inverter housing531will be described.

The plurality of electric modules532are obtained by dividing electric components such as semiconductor switching elements and smoothing capacitors constituting a power converter into a plurality of individual modules. The electric module532includes a switch module532A having a semiconductor switching element that is a power element and a capacitor module532B having a smoothing capacitor.

As illustrated inFIGS.49and50, a plurality of spacers549having a flat surface for attaching the electric module532are fixed to the inner peripheral surface of the inner wall member542, and the electric module532is attached to the spacer549. That is, the inner peripheral surface of the inner wall member542is a curved surface, whereas the mounting surface of the electric module532is a flat surface, and thus the spacer549forms a flat surface on the inner peripheral surface side of the inner wall member542, and the electric module532is fixed to the flat surface.

Note that the configuration in which the spacer549is interposed between the inner wall member542and the electric module532is not essential, and it is also possible to attach the electric module532directly to the inner wall member542by flattening the inner peripheral surface of the inner wall member542or by making the mounting surface of the electric module532curved. Further, it is also possible to fix the electric module532to the inverter housing531in a state of non-contact with the inner peripheral surface of the inner wall member542. For example, the electric module532is fixed to the end plate547of the boss forming member543. It is also possible to fix the switch module532A to the inner peripheral surface of the inner wall member542in a contact state, and to fix the capacitor module532B to the inner peripheral surface of the inner wall member542in a non-contact state.

Moreover, in a case where the spacer549is provided on the inner peripheral surface of the inner wall member542, the outer peripheral wall WA1and the spacer549correspond to the “tubular section”. Further, in a case where the spacer549is not used, the outer peripheral wall WA1corresponds to the “tubular section”.

As described above, the outer peripheral wall WA1of the inverter housing531is formed with the cooling water passage545through which cooling water as a refrigerant flows, and each electric module532is cooled by the cooling water flowing through the cooling water passage545. Moreover, it is also possible to use cooling oil as the refrigerant as an alternative to the cooling water. The cooling water passage545is provided in an annular shape along the outer peripheral wall WA1, and the cooling water flowing in the cooling water passage545flows from the upstream side to the downstream side while passing through each electric module532. In the present embodiment, the cooling water passage545is provided in an annular shape so as to overlap each electric module532inside and outside the radial direction and to surround these respective electric modules532.

The inner wall member542is provided with an inlet passage571for flowing the cooling water into the cooling water passage545and an outlet passage572for discharging the cooling water from the cooling water passage545. As described above, the plurality of electric modules532are fixed to the inner peripheral surface of the inner wall member542, and in such a configuration, the interval between the electric modules adjacent to each other in the circumferential direction is expanded in only one place, and a part of the inner wall member542is protruded inward in the radial direction to form a protruding section573in the expanded portion. In addition, the protruding section573is provided with the inlet passage571and the outlet passage572in a side-by-side manner along the radial direction.

FIG.58illustrates a state of arrangement of each electric module532in the inverter housing531. Note thatFIG.58is the same vertical cross-sectional view asFIG.50.

As illustrated inFIG.58, the respective electric modules532are arranged side by side in the circumferential direction with the interval between the electric modules in the circumferential direction as a first interval INT1or a second interval INT2. The second interval INT2is a wider interval than the first interval INT1. The respective intervals INT1and INT2are, for example, the distance between the center positions of two electric modules532adjacent to each other in the circumferential direction. In this case, the interval between the electric modules adjacent to each other in the circumferential direction without sandwiching the protruding section573is the first interval INT1, and the interval between the electric modules adjacent to each other in the circumferential direction sandwiching the protruding section573is the second interval INT2. That is, the interval between the electric modules adjacent to each other in the circumferential direction is partially widened, and the protruding section573is provided at, for example, the central portion of the widened interval (second interval INT2).

The respective intervals INT1and INT2may be, for example, the distance of an arc between the center positions of two electric modules532adjacent to each other in the circumferential direction, on the same circle centered on the rotating shaft501. Alternatively, the interval between the electric modules in the circumferential direction may be defined by angular distances θi1 and θi2 centered on the rotating shaft501(θi1<θi2).

Moreover, in the configuration illustrated inFIG.58, the respective electric modules532arranged at the first interval INT1are arranged in a state of being separated from each other in the circumferential direction (non-contact state), but instead of this configuration, the respective electric modules532may be arranged in the circumferential direction in a state of being in contact with each other.

As illustrated inFIG.48, the end plate547of the boss forming member543is provided with a water channel port574in which the passage ends of the inlet passage571and the outlet passage572are formed. A circulation path575for circulating cooling water is connected to the inlet passage571and the outlet passage572. The circulation path575is compose of a cooling water pipe. A pump576and a heat radiating device577are provided in the circulation path575, and the cooling water circulates through the cooling water passage545and the circulation path575as the pump576is driven. The pump576is an electric pump. The heat radiating device577is, for example, a radiator that releases the heat of the cooling water to the atmosphere.

As illustrated inFIG.50, since the stator520is arranged on the outside of the outer peripheral wall WA1and the electric module532is arranged on the inside of the outer peripheral wall WA1, the heat of the stator520is transferred to the outer peripheral wall WA1from the outside, and the heat of the electric module532is transferred from the inside. In this case, the stator520and the electric module532can be cooled at the same time by the cooling water flowing the cooling water passage545, and the heat of the heat-generating component in the rotating electric machine500can be efficiently released.

Here, the electrical configuration of the power converter will be described with reference toFIG.59.

As illustrated inFIG.59, the stator winding521is composed of a U-phase winding, a V-phase winding, and a W-phase winding, and an inverter600is connected to the stator winding521. The inverter600is composed of a full bridge circuit having the same number of upper and lower arms as the number of phases, and a series connection body composed of an upper arm switch601and a lower arm switch602is provided for each phase. These respective switches601and602are turned on/off by the drive circuit603, and the winding of each phase is energized by the on/off. The respective switches601and602are composed of a semiconductor switching element such as a MOSFET or an IGBT. Further, in the upper and lower arms of each phase, a charge supply capacitor604that supplies the charge required for switching to the respective switches601and602is connected in parallel to the series connection body of the switches601and602.

A control device607includes a microcomputer composed of a CPU and various memories, and performs energization control by turning on/off the respective switches601and602on the basis of various detected information in the rotating electric machine500and requests for power running and power generation. The control device607performs on/off control of the respective switches601and602by, for example, PWM control at a predetermined switching frequency (carrier frequency) and rectangular wave control. The control device607may be a built-in control device built in the rotating electric machine500, or an external control device provided outside the rotating electric machine500.

Incidentally, in the rotating electric machine500of the present embodiment, the electric time constant is small because the inductance of the stator520is reduced, and in a situation where the electrical time constant is small, it is desirable to increase the switching frequency (carrier frequency) and increase the switching speed. In this respect, the charge supply capacitor604is connected in parallel to the series connection body of the switches601and602of each phase, and thus the wiring inductance becomes low, and appropriate surge countermeasures are possible even with a configuration in which the switching speed is increased.

The high potential side terminal of the inverter600is connected to the positive electrode terminal of a DC power supply605, and the low potential side terminal is connected to the negative electrode terminal (ground) of the DC power supply605. Further, a smoothing capacitor606is connected to the high potential side terminal and the low potential side terminal of the inverter600, in parallel to the DC power supply605.

The switch module532A has the respective switches601and602(semiconductor switching elements), the drive circuit603(specifically, an electric element constituting the drive circuit603), and the charge supply capacitor604, as heat-generating components. Further, the capacitor module532B has the smoothing capacitor606as a heat-generating component. A specific configuration example of the switch module532A is illustrated inFIG.60.

As illustrated inFIG.60, the switch module532A has a module case611as a housing case, and the switches601and602for one phase housed in the module case611, the drive circuit603, and the charge supply capacitor604. The drive circuit603is configured as a dedicated IC or a circuit board and is provided in the switch module532A.

The module case611is made of an insulating material such as resin, and is fixed to the outer peripheral wall WA1with its side surface in contact with the inner peripheral surface of the inner wall member542of the inverter unit530. The module case611is filled with a molding material such as resin. In the module case611, the switches601and602and the drive circuit603, and the switches601and602and the capacitor604are electrically connected by a wiring612, respectively. More specifically, the switch module532A is attached to the outer peripheral wall WA1via the spacer549, but the spacer549is not illustrated.

In a state where the switch module532A is fixed to the outer peripheral wall WA1, the side of the switch module532A closer to the outer peripheral wall WA1, that is, the side closer to the cooling water passage545has higher cooling performance. Therefore, the order of the arrangement of the switches601and602, the drive circuit603, and the capacitor604is determined in accordance with the cooling performance. Specifically, when comparing the amount of heat generated, the switches601and602, the capacitor604, and the drive circuit603are in the order from the largest, and therefore the switches601and602, the capacitor604, and the drive circuit603are arranged in this order from the side closer to the outer peripheral wall WA1in accordance with the magnitude order of the amount of heat generated. Moreover, the contact surface of the switch module532A is preferably smaller than the contactable surface on the inner peripheral surface of the inner wall member542.

Furthermore, although detailed illustration of the capacitor module532B is omitted, the capacitor module532B is configured such that the capacitor606is housed in a module case having the same shape and size as that of the switch module532A. Similarly to the switch module532A, the capacitor module532B is fixed to the outer peripheral wall WA1in a state where the side surface of the module case611is in contact with the inner peripheral surface of the inner wall member542of the inverter housing531.

The switch module532A and the capacitor module532B do not necessarily have to be arranged concentrically on the radial inside of the outer peripheral wall WA1of the inverter housing531. For example, the switch module532A may be arranged radially inside the capacitor module532B, or vice versa.

When the rotating electric machine500is driven, heat exchange is performed between the switch module532A and the capacitor module532B and the cooling water passage545via the inner wall member542of the outer peripheral wall WA1. As a result, the switch module532A and the capacitor module532B are cooled.

Each electric module532may have a configuration in which cooling water is drawn into the module and the cooling water is used to cool the inside of the module. Here, the water-cooled structure of the switch module532A will be described with reference toFIGS.61(a) and61(b).FIG.61(a)is a vertical cross-sectional view illustrating a cross-sectional structure of the switch module532A in a direction crossing the outer peripheral wall WA1, andFIG.61(b)is a cross-sectional view taken along a line61B-61B ofFIG.61(a).

As illustrated inFIGS.61(a) and61(b), as is the case withFIG.60, the switch module532A has the module case611, the switches601and602for one phase, the drive circuit603, and the capacitor604, as inFIG.60. In addition, the switch module532A has a cooling device composed of a pair of piping sections621and622and a cooler623. In the cooling device, the pair of piping sections621and622are composed of an inflow side piping section621that allows cooling water to flow in from the cooling water passage545of the outer peripheral wall WA1to the cooler623and an outflow side piping section622that allows cooling water to flow out from the cooler623to the cooling water passage545. The cooler623is provided in accordance with an object to be cooled, and a one-stage or multiple-stage cooler623is used in the cooling device. In the configurations ofFIGS.61(a) and61(b), two-stage coolers623are provided in a direction away from the cooling water passage545, that is, in the radial direction of the inverter unit530, in a state of being separated from each other, and cooling water is supplied to those respective coolers623via the pair of piping sections621and622. The cooler623has, for example, a hollow inside. However, an inner fin may be provided inside the cooler623.

In the configuration including the two-stage coolers623, (1) the outer peripheral wall WA1side of the first-stage cooler623, (2) between the first-stage and second-stage coolers623, and (3) the opposite-to-outer peripheral wall side of the second stage cooler623is the place where the electric components to be cooled are placed, and each of these places is (2), (1), and (3) in order from the one with the highest cooling performance. That is, the place sandwiched between the two coolers623has the highest cooling performance, and in the place adjacent to any one of the coolers623, the place closer to the outer peripheral wall WA1(cooling water passage545) has higher cooling performance. Taking this into consideration, in the configurations illustrated inFIGS.61(a) and61(b), the switches601and602are arranged (2) between the first-stage and second-stage coolers623, the condenser604is arranged on (1) the outer peripheral wall WA1side of the first-stage cooler623, and the drive circuit603is arranged on (3) the opposite-to-outer peripheral wall side of the second-stage cooler623. Moreover, although not illustrated, the drive circuit603and the capacitor604may be arranged in reverse.

In either case, in the module case611, the switches601and602and the drive circuit603, and the switches601and602and the capacitor604are electrically connected by a wiring612, respectively. Further, since the switches601and602are located between the drive circuit603and the capacitor604, the wiring612extending from the switches601and602toward the drive circuit603and the wiring612extending from the switches601and602toward the capacitor604are in a relation in which they extend in opposite directions.

As illustrated inFIG.61(b), the pair of piping sections621and622are arranged side by side in the circumferential direction, that is, on the upstream side and the downstream side of the cooling water passage545, and cooling water flows into the cooler623from the inflow side piping section621located on the upstream side, and then the cooling water flows out from the outflow side piping section622located on the downstream side. Moreover, in order to promote the inflow of the cooling water into the cooling device, the cooling water passage545is preferably provided with a regulating section624that regulates the flow of cooling water, at a position between the inflow side piping section621and the outflow side piping section621when viewed in the circumferential direction. The regulating section624may be a blocking section that blocks the cooling water passage545, or a throttle section that reduces the passage area of the cooling water passage545.

FIG.62illustrates another cooling structure of the switch module532A.FIG.62(a)is a vertical cross-sectional view illustrating a cross-sectional structure of the switch module532A in a direction crossing the outer peripheral wall WA1, andFIG.62(b)is a cross-sectional view taken along a line62B-62B ofFIG.62(a).

The configurations ofFIGS.62(a) and62(b)differ from the configurations ofFIGS.61(a) and61(b)described above in that the pair of piping sections621and622in the cooling device are arranged differently, and a pair of piping sections621and622are arranged side by side in the axial direction. Further, as illustrated inFIG.62(c), in the cooling water passage545, the passage portion communicating with the inflow side piping section621and the passage portion communicating with the outflow side piping section622are separated in the axial direction. Each of these passage portions is communicated with each other through the respective piping sections621and622and each cooler623.

In addition, the following configuration can be used as the switch module532A.

In the configuration illustrated inFIG.63(a), the cooler623is changed from two stages to one stage as compared with the configuration illustrated inFIG.61(a). In this case, the place where the cooling performance is highest in the module case611is different from that inFIG.61(a), and the cooling performance is highest in the place on the outer peripheral wall WA1side of both sides in the radial direction (both sides in the right-left direction in the figure) of the cooler623, and then the cooling performance is lowered in the order of the place on the opposite-to-outer peripheral wall side of the cooler623and the place away from the cooler623. Taking this into consideration, in the configuration illustrated inFIG.63(a), the switches601and602are arranged on the outer peripheral wall WA1side of both sides in the radial direction (both sides in the right-left direction in the figure) of the cooler623, the capacitor604is arranged on the opposite-to-outer peripheral wall side of the cooler623, and the drive circuit603is arranged in the place away from the cooler623.

Further, in the switch module532A, it is possible to change the configuration in which the switches601and602for one phase, the drive circuit603, and the capacitor604are housed in the module case611. For example, the module case611may house either one of the switches601and602for one phase and the drive circuit603and the capacitor604.

InFIG.63(b), the pair of piping sections621and622and the two-stage coolers623are provided in the module case611, the switches601and602are arranged between the first-stage and second-stage coolers623, and the capacitor604or the drive circuit603is arranged on the outer peripheral wall WA1side of the first stage cooler623. Further, it is also possible to integrate the switches601and602and the drive circuit603into a semiconductor module, and to house the semiconductor module and the capacitor604in the module case611.

Moreover, inFIG.63(b), in the switch module532A, a capacitor is preferably arranged on the side opposite to the switches601and602in at least one of the coolers623arranged on both sides with the switches601and602therebetween. That is, there may be a configuration in which the capacitor604is arranged only on one of the outer peripheral wall WA1side of the first-stage cooler623and the opposite-to-peripheral wall side of the second-stage cooler623, or a configuration in which the capacitor604is arranged on the both sides.

In the present embodiment, of the switch module532A and the capacitor module532B, only the switch module532A is configured to draw cooling water from the cooling water passage545into the module. However, the configuration may be changed in such a manner that cooling water is drawn into both modules532A and532B from the cooling water passage545.

Further, it is also possible to cool each electric module532by directly applying cooling water to the outer surface of each electric module532. For example, as illustrated inFIG.64, by embedding the electric module532in the outer peripheral wall WA1, the cooling water is applied to the outer surface of the electric module532. In this case, it is conceivable to immerse a part of the electric module532in the cooling water passage545, or to expand the cooling water passage545further in the radial direction than in the configuration illustrated inFIG.58or the like to immerse all the electric modules532in the cooling water passage545. In the case where the electric module532is immersed in the cooling water passage545, the cooling performance can be further improved by providing a fin in the module case611(the immersed portion of the module case611) to be immersed.

Further, the electric module532includes a switch module532A and a capacitor module532B, and there is a difference in the amount of heat generated when both of them are compared. In consideration of this point, it is also possible to devise the arrangement of each electric module532in the inverter housing531.

For example, as illustrated inFIG.65, a plurality of switch modules532A are arranged in the circumferential direction without being dispersed, and arranged on the upstream side of the cooling water passage545, that is, on the side close to the inlet passage571. In this case, the cooling water flowing in from the inlet passage571is first used for cooling the three switch modules532A, and then used for cooling each capacitor module532B. Moreover, inFIG.65, the pair of piping sections621and622are arranged side by side in the axial direction as in the precedingFIGS.62(a) and62(b), but the present invention is not limited to this, and the pair of piping sections621and622may be arranged side by side in the circumferential direction as in the precedingFIGS.61(a) and61(b).

Next, the configuration related to the electrical connection in each electric module532and the bus bar module533will be described.FIG.66is a cross-sectional view taken along a line66-66ofFIG.49, andFIG.67is a cross-sectional view taken along a line67-67ofFIG.49.FIG.68is a perspective view illustrating the busbar module533alone. Here, the configuration related to the electrical connection in each electric module532and the bus bar module533will be described with reference to each of these figures.

As illustrated inFIG.66, in the inverter housing531, at positions adjacent to each other in the circumferential direction of the protruding section573provided on the inner wall member542(that is, the protruding section573provided with the inlet passage571and the outlet passage572communicating with the cooling water passage545), three switch modules532A are arranged side by side in the circumferential direction, and next to them, six capacitor modules532B are arranged side by side in the circumferential direction. As the outline, in the inverter housing531, the inside of the outer peripheral wall WA1is equally divided into 10 regions (that is, the number of modules+1) in the circumferential direction, and one electric module532is arranged in each of the nine regions, and the protruding section573is provided in the remaining one region. The three switch modules532A are a U-phase module, a V-phase module, and a W-phase module.

As illustrated inFIG.66and the above-mentionedFIGS.56and57, each electric module532(switch module532A and capacitor module532B) has a plurality of module terminals615extending from the module case611. The module terminal615is a module input/output terminal for performing electrical input/output in each electric module532. The module terminal615is provided so as to extend in the axial direction, and more specifically, the module terminal615is provided so as to extend from the module case611toward the back side of the rotor carrier511(outside the vehicle) (seeFIG.51).

The module terminals615of each electric module532are connected to the bus bar module533, respectively. The number of module terminals615differs between the switch module532A and the capacitor module532B. The switch module532A is provided with four module terminals615, and the capacitor module532B is provided with two module terminals615.

Further, as illustrated inFIG.68, the bus bar module533has an annular section631forming an annular shape, three external connection terminals632extending from the annular section631and enabling connection with external devices such as a power supply device and an ECU (electronic control unit), and a winding connection terminal633connected to the winding end of each phase in the stator winding521. The bus bar module533corresponds to a “terminal module”.

The annular section631is arranged in the inverter housing531at a position on the radial inside of the outer peripheral wall WA1and on one side in the axial direction of each electric module532. The annular section631has an annular main body formed of, for example, an insulating member such as resin, and a plurality of bus bars embedded therein. The plurality of bus bars are connected to the module terminal615of each electric module532, each external connection terminal632, and each phase winding of the stator winding521. The details will be described below.

The external connection terminal632is composed of a high potential side power terminal632A and a low potential side power terminal632B connected to the power supply device, and one signal terminal632C connected to an external ECU. Each of these external connection terminals632(632A to632C) is provided so as to be arranged in a line in the circumferential direction and to extend in the axial direction on the radial inside of the annular section631. As illustrated inFIG.51, in a state where the bus bar module533is assembled to the inverter housing531together with each electric module532, one end of the external connection terminal632is configured to protrude from the end plate547of the boss forming member543. Specifically, as illustrated inFIGS.56and57, the end plate547of the boss forming member543is provided with an insertion hole547a, a cylindrical grommet635is attached to the insertion hole547a, and the external connection terminal632is provided with the grommet635inserted. The grommet635also functions as a sealed connector.

The winding connection terminal633is a terminal connected to the winding end of each phase of the stator winding521, and is provided so as to extend radially outward from the annular section631. The winding connection terminal633has a winding connection terminal633U connected to the end of the U-phase winding in the stator winding521, a winding connection terminal633V connected to the end of the V-phase winding, and a winding connection terminal633W connected to each connection at the end of the W-phase winding. It is preferable to provide a current sensor634that detects the current (U-phase current, V-phase current, W-phase current) flowing through each of these winding connection terminals633and each phase winding (seeFIG.70).

Moreover, the current sensor634may be arranged outside the electric module532and around each winding connection terminal633, or may be arranged inside the electric module532.

Here, the connection between each electric module532and the bus bar module533will be described more specifically with reference toFIGS.69and70.FIG.69is a diagram illustrating each electric module532developed in a plane and schematically illustrating an electrical connection state between each electric module532and the bus bar module533.FIG.70is a diagram schematically illustrating the connection between each electric module532and the bus bar module533in a state where each electric module532is arranged in an annular shape. Moreover, inFIG.69, the path for power transmission is illustrated by a solid line, and the path of the signal transmission system is illustrated by a dashed line.FIG.70illustrates only the path for power transmission.

The bus bar module533has a first bus bar641, a second bus bar642, and a third bus bar643as bus bars for power transmission. Of these, the first bus bar641is connected to the high potential side power terminal632A, and the second bus bar642is connected to the low potential side power terminal632B. Further, three third bus bars643are connected to the U-phase winding connection terminal633U, the V-phase winding connection terminal633V, and the W-phase winding connection terminal633W, respectively.

Further, the winding connection terminal633and the third bus bar643are portions that easily generate heat due to the operation of the rotating electric machine10. Therefore, a terminal block (not illustrated) may be interposed between the winding connection terminal633and the third bus bar643, and the terminal block may be brought into contact with the inverter housing531having the cooling water passage545. Alternatively, the winding connection terminal633or the third bus bar643may be bent into a crank shape to bring the winding connection terminal633or the third bus bar643into contact with the inverter housing531having the cooling water passage545.

With such a configuration, the heat generated at the winding connection terminal633and the third bus bar643can be dissipated to the cooling water in the cooling water passage545.

Moreover, inFIG.70, the first bus bar641and the second bus bar642are illustrated as bus bars having an annular shape, but each of these bus bars641and642does not necessarily have to be connected in an annular shape and may have a substantially C-shape with a part discontinuous in the circumferential direction. Further, each winding connection terminal633U,633V, and633W may be individually connected to the switch module532A corresponding to each phase, and therefore may be directly connected to each switch module532A (actually, the module terminal615) without going through the bus bar module533.

Meanwhile, each switch module532A has four module terminals615composed of a positive electrode side terminal, a negative electrode side terminal, a winding terminal, and a signal terminal. Of these, the positive electrode side terminal is connected to the first bus bar641, the negative electrode side terminal is connected to the second bus bar642, and the winding terminal is connected to the third bus bar643.

Further, the bus bar module533has a fourth bus bar644as a bus bar of the signal transmission system. The signal terminal of each switch module532A is connected to the fourth bus bar644, and the fourth bus bar644is connected to the signal terminal632C.

In the present embodiment, the control signal for each switch module532A is input from the external ECU via the signal terminal632C. That is, the respective switches601and602in each switch module532A are turned on/off by a control signal input via the signal terminal632C. Therefore, each switch module532A is connected to the signal terminal632C without going through a control device disposed in the rotating electric machine on the way. However, it is also possible to change this configuration in such a manner that a rotating electric machine has a built-in control device and the control signal from the control device is input to each switch module532A. Such a configuration is illustrated inFIG.71.

In the configuration ofFIG.71, a control board651on which a control device652is mounted is provided, and the control device652is connected to each switch module532A. Further, the signal terminal632C is connected to the control device652. In this case, the control device652inputs a command signal related to power running or power generation from, for example, an external ECU which is a higher-level control device, and appropriately turns on/off the switches601and602of each switch module532A on the basis of the command signal.

In the inverter unit530, the control board651is preferably arranged on the further outside of the vehicle than the bus bar module533(back side of the rotor carrier511). Alternatively, the control board651may be arranged between each electric module532and the end plate547of the boss forming member543. The control board651is preferably arranged in such a manner that at least a part thereof overlaps with each electric module532in the axial direction.

Further, each capacitor module532B has two module terminals615composed of a positive electrode side terminal and a negative electrode side terminal, the positive electrode side terminal is connected to the first bus bar641, and the negative electrode side terminal is connected to the second bus bar642.

As illustrated inFIGS.49and50, the protruding section573having the inlet passage571and the outlet passage572for cooling water is provided in the inverter housing531at a position aligned with each electric module532in the circumferential direction, and the external connection terminals632is provided so as to be adjacent to the protruding section573in the radial direction. In other words, the protruding section573and the external connection terminal632are provided at the same angular position in the circumferential direction. In the present embodiment, the external connection terminal632is provided at a position on the radial inside of the protruding section573. Further, when viewed from the inside of the vehicle of the inverter housing531, the end plate547of the boss forming member543is provided with the water channel port574and the external connection terminal632arranged side by side in the radial direction (seeFIG.48).

In this case, by arranging the protruding section573and the external connection terminal632side by side in the circumferential direction together with the plurality of electric modules532, the inverter unit530can be downsized, and thus the rotating electric machine500can be downsized.

Referring toFIGS.45and47illustrating the structure of the wheel400, the cooling pipe H2is connected to the water channel port574, the electric wiring H1is connected to the external connection terminal632, and in that state, the electric wiring H1and the cooling pipe H2are housed in the housing duct440.

Moreover, in the above configuration, the three switch modules532A are arranged side by side in the circumferential direction next to the external connection terminal632in the inverter housing531, and next to them, the six capacitor modules532B are arranged side by side in the circumferential direction. However, this may be changed. For example, the three switch modules532A may be arranged side by side at a position farthest from the external connection terminal632, that is, a position opposite to the external connection terminal632with the rotating shaft501therebetween. Further, it is also possible to disperse each switch module532A in such a manner that the capacitor modules532B are arranged on both sides of each switch module532A.

If each switch module532A is arranged at the position farthest from the external connection terminal632, that is, a position opposite to the external connection terminal632with the rotating shaft501therebetween, a malfunction or the like caused by mutual inductance between the external connection terminal632and each switch module532A can be suppressed.

Next, the configuration of a resolver660provided as a rotation angle sensor will be described.

As illustrated inFIGS.49to51, the inverter housing531is provided with a resolver660that detects the electrical angle θ of the rotating electric machine500. The resolver660is an electromagnetic induction type sensor, and includes a resolver rotor661fixed to the rotating shaft501and a resolver stator662arranged so as to face the radial outside of the resolver rotor661. The resolver rotor661has a disc ring shape, and is provided coaxially with the rotating shaft501with the rotating shaft501inserted. The resolver stator662includes an annular stator core663and a stator coil664wound around a plurality of teeth formed on the stator core663. The stator coil664includes a one-phase excitation coil and a two-phase output coil.

The exciting coil of the stator coil664is excited by a sinusoidal excitation signal, and the magnetic flux generated in the exciting coil by the excitation signal interlinks a pair of output coils. In doing so, since the relative arrangement relation between the exciting coil and the pair of output coils changes periodically in accordance with the rotation angle of the resolver rotor661(that is, the rotation angle of the rotation shaft501), the amount of magnetic flux interlinking the pair of output coils changes periodically. In the present embodiment, the pair of output coils and the exciting coil are arranged in such a manner that the phases of the voltages generated in the pair of output coils are shifted by π/2 from each other. As a result, the output voltage of each of the pair of output coils becomes a modulated wave in which the excitation signal is modulated by the modulated waves sin θ, and cos θ, respectively. More specifically, when the excitation signal is “sin Ωt”, the modulated waves are “sin θ*sin Ωt” and “cos θ*sin Ωt”, respectively.

The resolver660has a resolver digital converter. The resolver digital converter calculates the electrical angle θ by detection based on the generated modulated wave and the excitation signal. For example, the resolver660is connected to the signal terminal632C, and the calculation result of the resolver digital converter is output to an external device via the signal terminal632C. Further, in a case where the rotating electric machine500has a built-in control device, the calculation result of the resolver digital converter is input to the control device.

Here, the assembly structure of the resolver660in the inverter housing531will be described.

As illustrated inFIGS.49and51, the boss section548of the boss forming member543constituting the inverter housing531has a hollow tubular shape, and on the inner peripheral side of the boss section548, a protruding portion548aextending in a direction orthogonal to the axial direction is formed. Then, the resolver stator662is fixed by a screw or the like in a state of being in contact with the protruding section548ain the axial direction. In the boss section548, the bearing560is provided on one side in the axial direction with the protruding section548atherebetween, and the resolver660is coaxially provided on the other side.

Further, in the hollow portion of the boss section548, a protruding section548ais provided on one side of the resolver660in the axial direction, and a disc ring-shaped housing cover666that closes the housing space of the resolver660is attached on the other side. The housing cover666is made of a conductive material such as carbon fiber reinforced plastic (CFRP). A hole666athrough which the rotating shaft501is inserted is formed in the central portion of the housing cover666. In the hole666a, a sealing material667that seals the airspace therebetween with the outer peripheral surface of the rotating shaft501. The resolver housing space is sealed by the sealing material667. The sealing material667is preferably, for example, a sliding seal made of a resin material.

The space in which the resolver660is housed is a space surrounded by the boss section548forming an annular shape in the boss forming member543and sandwiched between the bearing560and the housing cover666in the axial direction, and the circumference of the resolver660is surrounded by a conductive material. This makes it possible to suppress the influence of electromagnetic noise on the resolver660.

Further, as described above, the inverter housing531has the outer peripheral wall WA1and the inner peripheral wall WA2that together form a double wall (seeFIG.57), the stator520is arranged on the outside of the double peripheral walls (outside the outer peripheral wall WA1), the electric module532is arranged between the double peripheral walls (between WA1and WA2), and the resolver660is arranged inside the double peripheral walls (inside the inner peripheral wall WA2). Since the inverter housing531is a conductive member, the stator520and the resolver660are arranged so as to be separated from each other by a conductive partition wall (particularly a double conductive partition wall in the present embodiment), and the occurrence of mutual magnetic interference between the stator520side (magnetic circuit side) and the resolver660can be suitably suppressed.

Next, the rotor cover670provided on the open end side of the rotor carrier511will be described.

As illustrated inFIGS.49and51, one side of the rotor carrier511in the axial direction is open, and the substantially disc ring-shaped rotor cover670is attached to the open end. The rotor cover670is preferably fixed to the rotor carrier511by any joining method such as welding, adhesion, or screwing. It is more preferable that the rotor cover670has a portion whose dimension is set smaller than the inner circumference of the rotor carrier511in such a manner that the movement of the magnet unit512in the axial direction can be suppressed. The outer diameter dimension of the rotor cover670matches the outer diameter dimension of the rotor carrier511, and the inner diameter dimension of the rotor cover670is slightly larger than the outer diameter dimension of the inverter housing531. The outer diameter dimension of the inverter housing531and the inner diameter dimension of the stator520are the same.

As described above, the stator520is fixed to the radial outside of the inverter housing531. At the joint portion where the stator520and the inverter housing531are joined to each other, the inverter housing531protrudes axially with respect to the stator520. In addition, the rotor cover670is attached so as to surround the protruding portion of the inverter housing531. In this case, a sealing material671that seals the gap between the end face of the rotor cover670on the inner peripheral side and the outer peripheral surface of the inverter housing531is provided. The housing space of the magnet unit512and the stator520is sealed by the sealing material671. The sealing material671is preferably, for example, a sliding seal made of a resin material.

According to the present embodiment described in detail above, the following excellent effects can be obtained.

In the rotating electric machine500, the outer peripheral wall WA1of the inverter housing531is arranged radially inside the magnetic circuit section composed of the magnet unit512and the stator winding521, and the cooling water passage545is formed on the outer peripheral wall WA1. Further, a plurality of electric modules532are arranged in the circumferential direction along the outer peripheral wall WA1, on the radial inside of the outer peripheral wall WA1. As a result, the magnetic circuit section, the cooling water passage545, and the power converter can be arranged so as to be stacked in the radial direction of the rotating electric machine500, and an efficient component arrangement is possible while reducing the dimensions in the axial direction. Further, the plurality of electric modules532constituting the power converter can be efficiently cooled. As a result, the high efficiency and downsizing of the rotating electric machine500can be achieved.

The electric module532(switch module532A, capacitor module532B) having heat-generating components such as a semiconductor switching element and a capacitor is provided in contact with the inner peripheral surface of the outer peripheral wall WA1. As a result, the heat in each electric module532is transferred to the outer peripheral wall WA1, and the electric module532is suitably cooled by the heat exchange in the outer peripheral wall WA1.

In the switch module532A, the coolers623are arranged on both sides of the switches601and602, respectively, and in at least one of the coolers623on both sides of the switches601and602, the capacitor604is arranged on the side opposite to the switches601and602. As a result, the cooling performance for the switches601and602can be improved, and the cooling performance of the capacitor604can also be improved.

In the switch module532A, the coolers623are arranged on both sides of the switches601and602, respectively, and in one of the coolers623on both sides of the switches601and602, the drive circuit603is arranged on the side opposite to the switches601and602, and in the other of the coolers623, the capacitor604is arranged on the side opposite to the switches601and602. As a result, the cooling performance for the switches601and602can be improved, and the cooling performance of the drive circuit603and the capacitor604can also be improved.

For example, in the switch module532A, cooling water flows into the module from the cooling water passage545, and the semiconductor switching element or the like is cooled by the cooling water. In this case, the switch module532A is cooled by heat exchange by the cooling water inside the module in addition to heat exchange by the cooling water on the outer peripheral wall WA1. As a result, the cooling effect of the switch module532A can be enhanced.

In the cooling system in which the cooling water flows into the cooling water passage545from the external circulation path575, the switch module532A is arranged on the upstream side near the inlet passage571of the cooling water passage545, and the capacitor module532B is arranged on the downstream side of the switch module532A. In this case, assuming that the cooling water flowing through the cooling water passage545is lower in temperature toward the upstream side, it is possible to implement a configuration in which the switch module532A is preferentially cooled.

The interval between the electric modules adjacent to each other in the circumferential direction is partially widened, and the protruding section573having the inlet passage571and the outlet passage572is provided in the portion where the interval is widened (second interval INT2). As a result, the inlet passage571and the outlet passage572of the cooling water passage545can be suitably formed in the portion that is radially inside of the outer peripheral wall WA1. That is, in order to improve the cooling performance, it is necessary to secure the flow amount of the refrigerant, and for that purpose, it is conceivable to increase the opening areas of the inlet passage571and the outlet passage572. In this regard, as described above, by partially widening the interval between the electric modules and providing the protruding section573, the inlet passage571and the outlet passage572having a desired size can be suitably formed.

The external connection terminal632of the bus bar module533is arranged at a position radially aligned with the protruding section573on the radial inside of the outer peripheral wall WA1. That is, the external connection terminal632is arranged together with the protruding section573in the portion where the interval between the electric modules adjacent to each other in the circumferential direction is widened (the portion corresponding to the second interval INT2). As a result, the external connection terminal632can be suitably arranged while avoiding interference with each electric module532.

In the outer rotor type rotating electric machine500, the stator520is fixed to the radial outside of the outer peripheral wall WA1, and a plurality of electric modules532are arranged on the radial inside. As a result, the heat of the stator520is transferred to the outer peripheral wall WA1from the radial outside, and the heat of the electric module532is transferred from the radial inside. In this case, the stator520and the electric module532can be cooled at the same time by the cooling water flowing the cooling water passage545, and the heat of the heat-generating member in the rotating electric machine500can be efficiently released.

The electric module532on the radial inside and the stator winding521on the radial outside are electrically connected by the winding connection terminal633of the bus bar module533with the outer peripheral wall WA1therebetween. Further, in this case, the winding connection terminal633is provided at a position axially separated from the cooling water passage545. As a result, even in a configuration in which the cooling water passage545is formed in an annular shape on the outer peripheral wall WA1, that is, the inside and outside of the outer peripheral wall WA1are separated by the cooling water passage545, the electric module532and the stator winding521can be suitably connected.

In the rotating electric machine500of the present embodiment, by reducing or eliminating the teeth (iron core) between the respective conductors523arranged in the circumferential direction in the stator520, the torque limitation caused by the magnetic saturation between the respective conductors523is suppressed, and the torque decrease is suppressed by making the conductor523flat and thin. In this case, even if the outer diameter dimension of the rotating electric machine500is the same, the region on the radial inside of the magnetic circuit section can be expanded by reducing the thickness of the stator520, and with the use of the inner region, the outer peripheral wall WA1having the cooling water passage545and the plurality of electric modules532provided radially inside the outer peripheral wall WA1can be suitably arranged.

In the rotating electric machine500of the present embodiment, the magnet magnetic flux in the magnet unit512is collected on the d-axis side, and thus the magnet magnetic flux on the d-axis is strengthened, and the torque can be increased accordingly. In this case, as the radial thickness dimension can be reduced (thinned) in the magnet unit512, the region on the radial inside of the magnetic circuit section can be expanded by reducing the thickness of the stator520, and with the use of the inner region, the outer peripheral wall WA1having the cooling water passage545and the plurality of electric modules532provided radially inside the outer peripheral wall WA1can be suitably arranged.

Further, not only the magnetic circuit section, the outer peripheral wall WA1, and the plurality of electric modules532, but also the bearing560and the resolver660can be suitably arranged in the radial direction in the same manner.

The wheel400using the rotating electric machine500as an in-wheel motor is mounted on a vehicle body via the base plate405fixed to the inverter housing531and a mounting mechanism such as a suspension device. Here, since the rotating electric machine500has been downsized, it is possible to save space even if it is assumed to be assembled to a vehicle body. Therefore, it is possible to implement an advantageous configuration in expanding the installation region of the power supply device such as a battery in the vehicle and expanding the vehicle interior space.

A modification on an in-wheel motor will be described below.

First Modification in an In-Wheel Motor

In the rotating electric machine500, the electric module532and the bus bar module533are arranged radially inside the outer peripheral wall WA1of the inverter unit530, and the electric module532and the bus bar module533and the stator520are arranged radially inside and outside so as to be separated from each other by the outer peripheral wall WA1, respectively. In such a configuration, the position of the bus bar module533with respect to the electric module532can be arbitrarily set. Further, when connecting each phase winding of the stator winding521and the bus bar module533across the outer peripheral wall WA1in the radial direction, a winding connection wire (for example, the winding connection terminal633) used for the connection can be arbitrarily set.

That is, as the position of the bus bar module533with respect to the electric module532, a configuration (α1) in which the bus bar module533is located further outside of the vehicle in the axial direction than the electric module532, that is, on the back side in the rotor carrier511side and a configuration (α2) in which the bus bar module533is located further inside of the vehicle in the axial direction than the electric module532, that is, on the front side in the rotor carrier511side are conceivable.

Further, as a position to guide the winding connection winding connection wire, a configuration (β1) in which the winding connection wire is guided in the axial direction on the outside of the vehicle, that is, on the back side in the rotor carrier511side and a configuration (β2) in which the winding connection wire is guided in the axial direction on the inside of the vehicle, that is, on the front side in the rotor carrier511side are conceivable.

Hereinafter, four configuration examples relating to the arrangement of the electric module532, the bus bar module533, and the winding connection wire will be described with reference toFIGS.72(a) to72(d).FIGS.72(a) to72(d)are vertical cross-sectional views illustrating a simplified configuration of the rotating electric machine500, in which the same reference signs are given to the configurations already described. The winding connection wire637is an electric wiring that connects each phase winding of the stator winding521and the bus bar module533, and for example, the winding connection terminal633described above corresponds to this.

In the configuration ofFIG.72(a), the above (α1) is adopted as the position of the bus bar module533with respect to the electric module532, and the above (β1) is adopted as the position for guiding the winding connection wire637. That is, the electric module532, the bus bar module533, the stator winding521, and the bus bar module533are all connected on the outside of the vehicle (the back side of the rotor carrier511). This corresponds to the configuration illustrated inFIG.49.

According to this configuration, the cooling water passage545can be provided on the outer peripheral wall WA1without fear of interference with the winding connection wire637. Further, the winding connection wire637that connects the stator winding521and the bus bar module533can be easily achieved.

In the configuration ofFIG.72(b), the above (α1) is adopted as the position of the bus bar module533with respect to the electric module532, and the above (β2) is adopted as the position for guiding the winding connection wire637. That is, the electric module532and the bus bar module533are connected on the outside of the vehicle (the back side of the rotor carrier511), and the stator winding521and the bus bar module533are connected on the inside of the vehicle (the front side of the rotor carrier511).

According to this configuration, the cooling water passage545can be provided on the outer peripheral wall WA1without fear of interference with the winding connection wire637.

In the configuration ofFIG.72(c), the above (α2) is adopted as the position of the bus bar module533with respect to the electric module532, and the above (β1) is adopted as the position for guiding the winding connection wire637. That is, the electric module532and the bus bar module533are connected on the inside of the vehicle (the front side of the rotor carrier511), and the stator winding521and the bus bar module533are connected on the outside of the vehicle (the back side of the rotor carrier511).

In the configuration ofFIG.72(d), the above (α2) is adopted as the position of the bus bar module533with respect to the electric module532, and the above (β2) is adopted as the position for guiding the winding connection wire637. That is, the electric module532, the bus bar module533, the stator winding521, and the bus bar module533are all connected on the inside of the vehicle (the front side of the rotor carrier511).

According to the configurations ofFIGS.72(c) and72(d), the bus bar module533is arranged inside the vehicle (on the front side of the rotor carrier511), and thus it is considered the wiring becomes easy when adding an electric component such as a fan motor. Further, it is possible that the bus bar module533can be brought closer to the resolver660arranged further inside the vehicle than the bearing, and it is considered that wiring to the resolver660becomes easier

Second Modification in an In-Wheel Motor

A modification of the mounting structure of the resolver rotor661will be described below. That is, the rotating shaft501, the rotor carrier511, and the inner ring561of the bearing560are a rotating body that rotates integrally, and a modification of the mounting structure of the resolver rotor661with respect to the rotating body will be described below.

FIGS.73(a) to73(c)are block diagrams illustrating an example of a mounting structure of the resolver rotor661to the rotating body. In any of the configurations, the resolver660is provided in a closed space surrounded by the rotor carrier511, the inverter housing531and the like, and protected from external water, mud, and the like. OfFIGS.73(a) to73(c), inFIG.73(a), the bearing560has the same configuration as that inFIG.49. Further, inFIGS.73(b) and73(c), the bearing560has a configuration different from that ofFIG.49, and is arranged at a position away from the end plate514of the rotor carrier511. In each of these figures, two locations are illustrated as mounting locations for the resolver rotor661. Moreover, although the resolver stator662is not illustrated, for example, the boss section548of the boss forming member543should be extended to the outer peripheral side of the resolver rotor661or its vicinity, and the resolver stator662should be fixed to the boss section548.

In the configuration ofFIG.73(a), the resolver rotor661is attached to the inner ring561of the bearing560. Specifically, the resolver rotor661is provided on the axial end face of the flange561bof the inner ring561, or is provided on the axial end face of the tubular section561aof the inner ring561.

In the configuration ofFIG.73(b), the resolver rotor661is attached to the rotor carrier511. Specifically, the resolver rotor661is provided on the inner surface of the end plate514in the rotor carrier511. Alternatively, in a configuration in which the rotor carrier511has a tubular section515extending from the inner peripheral edge portion of the end plate514along the rotating shaft501, the resolver rotor661is provided on the outer peripheral surface of the tubular section515of the rotor carrier511. In the latter case, the resolver rotor661is arranged between the end plate514of the rotor carrier511and the bearing560.

In the configuration ofFIG.73(c), the resolver rotor661is attached to the rotating shaft501. Specifically, on the rotating shaft501, the resolver rotor661is provided between the end plate514of the rotor carrier511and the bearing560. Alternatively, on the rotating shaft501, the resolver rotor661is arranged on the side opposite to the rotor carrier511with the bearing560therebetween.

Third Modification in an In-Wheel Motor

A modification of the inverter housing531and the rotor cover670will be described below with reference toFIG.74.FIGS.74(a) and74(b)are vertical cross-sectional views illustrating a simplified configuration of the rotating electric machine500, in which the same reference signs are given to the configurations already described. Moreover, the configuration illustrated inFIG.74(a)substantially corresponds to the configuration described with reference toFIG.49and the like, and the configuration illustrated inFIG.74(b)corresponds to the configuration in which a part of the configuration ofFIG.74(a)is modified.

In the configuration illustrated inFIG.74(a), the rotor cover670fixed to the open end of the rotor carrier511is provided so as to surround the outer peripheral wall WA1of the inverter housing531. That is, the end face on the inner diameter side of the rotor cover670faces the outer peripheral surface of the outer peripheral wall WA1, and the sealing material671is provided between them. Further, the housing cover666is attached to the hollow portion of the boss section548of the inverter housing531, and the sealing material667is provided between the housing cover666and the rotating shaft501. The external connection terminal632constituting the bus bar module533penetrates the inverter housing531and extends to the inside of the vehicle (lower side in the figure).

Further, in the inverter housing531, the inlet passage571and the outlet passage572communicating with the cooling water passage545are formed, and the water channel port574including the passage ends of the inlet passage571and the outlet passage572is formed.

On the other hand, in the configuration illustrated inFIG.74(b), the inverter housing531(specifically, the boss forming member543) is formed with an annular protrusion681extending toward the protruding side (inside the vehicle) of the rotating shaft501. The rotor cover670is provided so as to surround the protrusion681of the inverter housing531. That is, the end face on the inner diameter side of the rotor cover670faces the outer peripheral surface of the protrusion681, and the sealing material671is provided between them. Further, the external connection terminal632constituting the bus bar module533penetrates the boss section548of the inverter housing531and extends into the hollow region of the boss section548, and also penetrates the housing cover666and extends to the inside of the vehicle (lower side of the figure).

Further, the inverter housing531is formed with the inlet passage571and the outlet passage572communicating with the cooling water passage545, those inlet passage571and outlet passage572extend into the hollow region of the boss section548and extend to the further inside of the vehicle (lower side of the figure) than the housing cover666via a relay pipe682. In this configuration, the piping portion extending from the housing cover666to the inside of the vehicle is the water channel port574.

According to the configurations ofFIGS.74(a) and74(b), the rotor carrier511and the rotor cover670can be suitably rotated with respect to the housing531while maintaining airtightness of the internal space of the rotor carrier511and the rotor cover670.

Moreover, in particular, according to the configuration ofFIG.74(b), the inner diameter of the rotor cover670is smaller than that of the configuration ofFIG.74(a). Therefore, the inverter housing531and the rotor cover670can be provided double in the axial direction at a position further inside the vehicle than the electric module532, and the inconvenience caused by electromagnetic noise, which is a concern in the electric module532, is suppressed. Further, by reducing the inner diameter of the rotor cover670, the sliding diameter of the sealing material671can be reduced, and mechanical loss in the rotating sliding portion can be suppressed.

Fourth Modification in an In-Wheel Motor

A modification of the stator winding521will be described below.FIG.75illustrates a modification on the stator winding521.

As illustrated inFIG.75, in the stator winding521, a conductor material having a rectangular cross section is used, and is wound by a wave winding with the long side of the conductor material extending in the circumferential direction. In this case, the conductors523of each phase on the coil side of the stator winding521are arranged at predetermined pitch intervals for each phase and are connected to each other at the coil ends. The conductors523adjacent to each other in the circumferential direction on the coil side are in contact with each other at the end faces in the circumferential direction, or are arranged close to each other at a minute interval.

Further, in the stator winding521, the conductor material is bent in the radial direction for each phase at the coil end. More specifically, the stator winding521(conductor material) is bent inward in the radial direction at a different position for each phase in the axial direction, whereby interference with each other in the respective U-phase, V-phase, and W-phase windings is avoided. In the illustrated configuration, the conductors are bent at a right angle inward in the radial direction for each phase, with each phase winding being different by the thickness of the conductor material. In each of the conductors523arranged in the circumferential direction, the length dimension between both ends in the axial direction is preferably the same for each of the conductors523.

Moreover, in a case where the stator core522is assembled to the stator winding521to manufacture the stator520, a part of the annular shape of the stator winding521is preferably opened as a non-connection part (that is, the stator winding521is preferably made to be substantially C-shaped), and after assembling the stator core522on the inner peripheral side of the stator winding521, the disconnecting portions are preferably connected to each other to form the stator winding521in an annular shape.

In addition to the above, it is also possible to divide the stator core522into a plurality of parts (for example, three or more) in the circumferential direction, and assemble the core pieces divided into a plurality of pieces onto the inner peripheral side of the stator winding521formed in an annular shape.

Fifteenth Modification

Next, a rotating electric machine700in this modification will be described. The rotating electric machine700is used as a vehicle driving unit. The outline of the rotating electric machine700is illustrated inFIGS.76to78.FIG.76is a perspective view illustrating the entire rotating electric machine700,FIG.77is a vertical cross-sectional view of the rotating electric machine700, andFIG.78is an exploded cross-sectional view of components of the rotating electric machine700.

The rotating electric machine700is an outer rotor type surface magnet type rotating electric machine. The rotating electric machine700includes, roughly, a rotating electric machine main body having a rotor710, a stator730, an inner unit770, and a bus bar module810, and a housing831and a cover832provided so as to surround the rotating electric machine main body. Each of these members is arranged coaxially with the rotating shaft701integrally provided on the rotor710and is assembled in the axial direction in a predetermined order to form the rotating electric machine700. The rotor710is cantilevered and supported by a pair of bearings791and792provided radially inside the inner unit770, and can rotate in that state. The rotating shaft701is integrally provided with a connecting shaft705fixed to the axle, wheels, or the like of the vehicle.

In the rotating electric machine700, the rotor710and the stator730each have a cylindrical shape, and are arranged so as to face each other with an air gap therebetween. As the rotor710rotates integrally with the rotating shaft701, the rotor710rotates on the radial outside of the stator730.

As illustrated inFIG.79, the rotor710has a substantially cylindrical rotor carrier711and an annular magnet unit712fixed to the rotor carrier711. The rotor carrier711has an end plate section713and a tubular section714extending axially from the outer peripheral portion of the end plate section713. A through hole713ais formed in the end plate section713, and the rotating shaft701is fixed to the end plate section713by a fastener715such as a bolt in a state of being inserted through the through hole713a. The rotating shaft701has a flange702extending in a direction intersecting with (orthogonal to) the axial direction at a portion where the rotor carrier711is fixed, and in a state where the flange702and the surface of the end plate section713are surface-joined, the rotor carrier711is fixed to the rotating shaft701.

The magnet unit712has a cylindrical magnet holder721, a magnet722fixed to the inner peripheral surface of the magnet holder721, and an annular end plate723fixed on the side opposite to the rotor carrier711on both sides of the magnet722in the axial direction. The magnet holder721has the same length dimension as that of the magnet722in the axial direction. The magnet722is provided in the magnet holder721in a state of being surrounded from the outside in the radial direction. Further, the magnet holder721and the magnet722are fixed in a state where one end side of both ends in the axial direction is in contact with the rotor carrier711, and the other end side is in contact with the end plate723.

The rotor carrier711, the magnet holder721, and the end plate723are all made of aluminum or non-magnetic stainless steel (for example, SUS304), which is a non-magnetic substance having a specific gravity smaller than that of iron. Each of these members is preferably made of a light metal such as aluminum, but can be made of a synthetic resin instead. Each of these members is preferably joined by adhesion or welding. Moreover, for example, the magnet holder721may be composed by laminating a plurality of core sheets of non-magnetic substances in the axial direction. The core sheet is formed in, for example, an annular plate shape by punching. Further, for example, the magnet holder721may have a helical core structure. In the magnet holder721having a helical core structure, a strip-shaped core sheet is used, and the core sheet is wound in an annular shape and laminated in the axial direction to thereby form a cylindrical magnet holder721as a whole.

The end plate723is made of a non-magnetic material having a specific gravity greater than that of the magnet holder721. As a result, the amount of scraping of the end plate723can be reduced in a case where the rotor710is balanced about the shaft center of the rotating shaft701by scraping the end plate723in the manufacturing process of the rotating electric machine700. Therefore, the balancing work can be facilitated.

FIG.80is a partial cross-sectional view illustrating a cross-sectional structure of the magnet unit712in an enlarged manner. InFIG.80, the axis of easy magnetization of the magnet722is indicated by an arrow.

In the magnet unit712, the magnets722are arranged side by side in such a manner that the polarities alternate along the circumferential direction of the rotor710. As a result, the magnet722has a plurality of magnetic poles in the circumferential direction. The magnet722is a polar anisotropic permanent magnet, and is composed with the use of a sintered neodymium magnet having an intrinsic coercive force of 400 [kA/m] or more and a residual magnetic flux density Br of 1.0 [T] or more. The magnet722is fixed to the inner peripheral surface of the magnet holder721by, for example, adhesion.

The magnet722is provided as one magnet between the d-axes, which is the center of each of the two magnetic poles adjacent to each other in the circumferential direction. That is, in the magnet722, one magnet is for one magnetic pole, and the center in the circumferential direction thereof is the q-axis. The peripheral surface on the radial inside of the magnet722is a magnetic flux transfer surface724on which magnetic flux is transferred. The magnet722has a different direction of the axis of easy magnetization on the d-axis side (the portion near the d-axis) and the q-axis side (the portion near the q-axis), and on the d-axis side, the direction of the axis of easy magnetization is the direction parallel to the d-axis, and on the q-axis side, the direction of the easy magnetization axis is the direction orthogonal to the q-axis. In this case, an arc-shaped magnet magnetic path is formed along the direction of the axis of easy magnetization. In short, the magnet722is configured, in which the orientation was made in such a manner that the direction of the axis of easy magnetization is parallel to the d-axis on the d-axis side which is the center of the magnetic pole as compared with the q-axis side which is the magnetic pole boundary.

According to each magnet722arranged in the circumferential direction, the magnet magnetic flux on the d-axis is strengthened and the change in magnetic flux near the q-axis is suppressed. As a result, the magnet722in which the change in surface magnetic flux from the q-axis to the d-axis at each magnetic pole is gentle can be suitably achieved. The magnet722may have a configuration in which the center in the circumferential direction is the d-axis as an alternative to the configuration in which the center in the circumferential direction is the q-axis. Further, a magnet connected in an annular shape may be used as the magnet722, instead of using the same number of magnets as the number of magnetic poles.

It is desirable that the magnet722has the following configuration. In the magnet722, a thickness dimension TA in the radial direction is equal to or less than an arc length TB of the magnetic flux transfer surface724between the d-q axes, and specifically, is smaller than the arc length TB. As a result, the thickness of the magnet722can be reduced, and the amount of the magnet722used can be reduced.

Further, as illustrated inFIG.81, in the magnet722, when an intersection of the q-axis and the magnetic flux transfer surface724is a center point CP and a circle whose radius is a radial thickness dimension of the magnet722is an orientation circle X that defines the axis of easy magnetization of the magnet722, the magnet722covers a quarter circle of the orientation circle X. That is, the magnet722is provided with arc-shaped axes of easy magnetization that cross the q-axis. Of the axes of easy magnetization, the strongest magnet magnetic flux is generated by the axis of easy magnetization passing through the intersection of the peripheral surface opposite to the magnetic flux transfer surface724and the q-axis in the radial direction, that is, the axis of easy magnetization passing through the orientation circle X. In this case, the magnet722includes a quarter circle of the orientation circle X, whereby it is possible to secure the length of the magnet magnetic path passing through the d-axis as the length defined by the orientation circle X, and then generate the magnet magnetic flux.

Here, in the magnet722, when the thickness dimension TA in the radial direction is smaller than the arc length TB of the magnetic flux transfer surface724between the d-q axes, there is a concern about magnetic flux leakage to radially outside the magnet722, that is, the opposite-to-stator side. However, in the present embodiment, since the magnet holder721is made of a non-magnetic material, the influence of magnetic flux leakage can be reduced.

Further, the magnet722is formed with a recess725in a predetermined range including the d-axis on the outer peripheral surface on the radial outside, and a recess726is formed in a predetermined range including the q-axis on the inner peripheral surface on the radial inside. In this case, according to the direction of the axis of easy magnetization of the magnet722, the magnet magnetic path is shortened near the d-axis on the outer peripheral surface of the magnet722, and the magnet magnetic path is shortened near the q-axis on the inner peripheral surface of the magnet722. Accordingly, in consideration of the fact that it is difficult for the magnet722to generate a sufficient magnet magnetic flux in a place where the magnet magnetic path length is short, the magnet is omitted in a place where the magnet magnetic flux is weak.

The magnet holder721is provided on the radial outside of the respective magnets722arranged in the circumferential direction. Further, the magnet holder721may be provided in a range including between the respective magnets722in the circumferential direction and the radial inside of the respective magnets722. That is, the magnet holder721may be provided so as to surround the respective magnets722. In a case where the magnet holder721has a radial outer portion and a radial inner portion of each magnet722, it is preferable that the radial outer portion has a higher strength than the radial inner portion.

The magnet holder721has a protrusion727that enters the recess725of the magnet722. In this case, the displacement of the magnet722in the circumferential direction is suppressed by the engagement between the recess725of the magnet722and the protrusion727of the magnet holder721. That is, the protrusion727of the magnet holder721functions as a rotation stop section of the magnet722. Further, in a case where the magnet holder721has a portion that is radially inside (the stator730side) of the magnet722, the portion may be provided with a protrusion that enters the recess726of the magnet722.

Moreover, as illustrated inFIGS.80and82, the rotor carrier711, magnet holder721, and end plate723should be integrated by welding both sides in the axial direction of a rod716inserted into the respective holes of the rotor carrier711, magnet holder721, and end plate723.

Furthermore, inFIG.80, the magnet holder721is provided between the magnets722adjacent to each other in the circumferential direction, but the present invention is not limited to this, and the magnet holder721may not be provided. In this case, the magnets722adjacent to each other in the circumferential direction come into contact with each other.

Next, the configuration of the stator730will be described.

The stator730has a stator winding731and a stator core732. The stator core732has a cylindrical shape in which a plurality of core sheets composed of an electromagnetic steel sheet that is a magnetic substance are laminated in the axial direction and has a predetermined thickness in the radial direction, and the stator winding731is assembled on the radially outside that is the rotor710side in the stator core732. The outer peripheral surface of the stator core732has a curved surface without unevenness. The stator core732functions as a back yoke. The stator core732is composed by, for example, a plurality of core sheets punched out in an annular plate shape and laminated in the axial direction. However, it may have a helical core structure. In the stator core732having a helical core structure, a strip-shaped core sheet is used, and the core sheet is wound in an annular shape and laminated in the axial direction to thereby form a cylindrical stator core732as a whole.

The stator730has, in the axial direction, a portion corresponding to the coil side of the rotor710that faces the magnet722in the radial direction and a portion corresponding to the coil end which is the axially outer side of the coil side. In this case, the stator core732is provided in a range corresponding to the coil side in the axial direction.

The stator winding731has a plurality of phase windings, and the phase winding of each phase is arranged in a predetermined order in the circumferential direction to form a cylindrical shape (annular shape). The stator core732is assembled radially inside the stator winding731. In the present embodiment, a U-phase, V-phase, and W-phase windings are used, and the stator winding731is thereby configured as a three-phase winding.

Next, the inner unit770will be described.

FIGS.83and84are a vertical cross-sectional view of the inner unit770. Note thatFIG.84illustrates a state where the bearings791and792that support the rotating shaft701are assembled to the inner unit770. For convenience, in the following description, the bearing791will also be referred to as a first bearing791, and the bearing792will also be referred to as a second bearing792. The first bearing791is a bearing provided on the base end side in the axial direction of the rotating shaft701, that is, on the connecting shaft705side, and the second bearing792is a bearing provided on the tip side of the rotating shaft701.

The inner unit770has an inner housing771. The inner housing771has a cylindrical outer cylinder member772, an inner cylinder member773having a cylindrical outer peripheral diameter smaller than that of the outer cylinder member772and arranged inside the outer cylinder member772in the radial direction, and a substantially disk-shaped end plate774fixed to one end side in the axial direction of the outer cylinder member772and the inner cylinder member773. Each of these members772to774is preferably made of a conductive material, for example, made of carbon fiber reinforced plastic (CFRP). The outer cylinder member772and the end plate774have the same outer dimensions, and the inner cylinder member773is provided in the space formed by the outer cylinder member772and the end plate774. The inner cylinder member773is fixed to the outer cylinder member772and the end plate774by fasteners775such as bolts, respectively.

The stator core732is fixed to the radial outside of the outer cylinder member772of the inner housing771. As a result, the stator730and the inner unit770are integrated.

A refrigerant passage777through which a refrigerant such as cooling water flows is formed between the outer cylinder member772and the inner cylinder member773. The refrigerant passage777is provided in an annular shape in the circumferential direction of the inner housing771. Although not illustrated, a refrigerant pipe is connected to the refrigerant passage777, and the refrigerant flowing from the refrigerant pipe exchanges heat in the refrigerant passage777and then flows out to the refrigerant pipe again.

An annular space is formed radially inside the inner cylinder member773, and it is preferable that an electric component constituting an inverter as, for example, a power converter is arranged in the annular space. The electric component is, for example, an electric module in which a semiconductor switching element or a capacitor is packaged. By arranging the electric module in contact with the inner cylinder member773, the electric module is cooled by the refrigerant flowing through the refrigerant passage777.

The outer cylinder member772has a cylindrical boss section780radially inside the inner cylinder member773. The boss section780is provided in a hollow tubular shape, and the rotating shaft701is inserted through the hollow portion. The boss section780is a bearing holding section that holds the bearings791and792, and the bearings791and792are fixed in the hollow portion. The bearings791and792are, for example, radial ball bearings having a tubular inner ring, a tubular outer ring arranged radially outside the inner ring, and a plurality of balls arranged between the inner ring and the outer ring, and are assembled to the inner unit770by the outer ring fixed to the boss section780.

The hollow portion of the boss section780is provided with a first fixing section781that fixes the first bearing791and a second fixing section782that fixes the second bearing792. The first bearing791and the second bearing792have different sizes depending on the support position on the rotating shaft701in consideration of the vibration and the centrifugal load of the rotor710, and the first bearing791that supports the base end side of the rotating shaft701is a bearing having a larger size, that is, a bearing having a larger supporting load. Therefore, the first fixing section781is formed to have a larger diameter than that of the second fixing section782.

Further, comparing the first bearing791and the second bearing792, the first bearing791has a larger radial internal gap, that is, a radial gap larger than that of the second bearing792. Moreover, the radial gap is the amount of end play between the inner ring, the outer ring, and the ball of the bearing. Here, the first bearing791is a bearing that is more susceptible to vibration and centrifugal load of the rotor710than the second bearing792, and by increasing the radial gap of the first bearing791, the effect of load absorption can be enhanced. As a result, the load acting on the boss section780on the base end side of the rotating shaft701is reduced, and the shake on the tip side of the rotating shaft701is suppressed.

The first fixing section781is formed by a parallel surface781aparallel to the axial direction and an orthogonal surface781borthogonal to the axial direction in the boss section780, and the first bearing791is fixed in a state of being in contact with each of these surfaces. Further, the second fixing section782is formed by a parallel surface782aparallel to the axial direction and an orthogonal surface782borthogonal to the axial direction in the boss section780, and the second bearing792is fixed in a state of being in contact with each of these surfaces. Moreover, a spring (not illustrated) that applies a preload to the second bearing792may be provided between the step between the second fixing section782and a third fixing section783and the second bearing792.

Furthermore, in the hollow portion of the boss section780, the third fixing section783that fixes a resolver800as a rotation sensor is provided on the side of the second fixing section782, of the first fixing section781and the second fixing section782. The third fixing section783is formed by expanding the diameter of the second fixing section782in a stepped shape.

As illustrated inFIG.77, the resolver800includes a resolver rotor801fixed to the rotating shaft701and a resolver stator802arranged so as to face the radial outside of the resolver rotor801. The resolver rotor801has a disc ring shape, and is provided coaxially with the rotating shaft701with the rotating shaft701inserted. The resolver stator802has a stator core and a stator coil (not illustrated), and is fixed to the third fixing section783of the boss section780.

As illustrated inFIG.83, the hollow portion of the boss section780is provided with reduced diameter sections784and785with a diameter smaller than that of each of these fixing sections781and782, at a position between the first fixing section781and the second fixing section782in the axial direction. The reduced diameter section784is a hole having a smaller diameter than that of the first fixing section781, and the reduced diameter section785is a hole having a smaller diameter than that of the second fixing section782. Further, the third fixing section783that fixes the resolver800is provided as a portion having a diameter larger than that of the second fixing section782, at a position that is axially outside the second fixing section782, in other words, at a position that is on the tip side of the rotating shaft701. The second fixing section782and the third fixing section783are provided at positions adjacent to each other in the axial direction.

In this case, when the outer cylinder member772is bored by boring or the like, the second fixing section782and the third fixing section783can be continuously machined coaxially from the same direction. Therefore, the coaxiality between the second bearing792fixed to the second fixing section782and the resolver stator802fixed to the third fixing section783is increased, and thus the coaxiality between the resolver rotor801and the resolver stator802is increased. In this case, shaking of the resolver stator802with respect to the resolver rotor801is reduced, and thus the angle detection error in the resolver800is reduced.

Next, the bus bar module810will be described. The bus bar module810is a winding connecting member that electrically connects the stator winding731of each phase. The bus bar module810has an annular shape.

According to the present embodiment described above, the following effects can be obtained.

The magnet holder721is made of a non-magnetic material having a specific gravity smaller than that of iron, which is suitable for reducing the weight of the rotor710. Further, the magnet722is oriented as illustrated inFIGS.80and81. According to this orientation, the direction of the axis of easy magnetization on the q-axis is orthogonal to the q-axis. According to the configuration described above, it is possible to suppress magnetic flux leakage from the magnet722to the magnet holder721and suppress a decrease in torque of the rotating electric machine700as compared with a configuration including a radially oriented magnet. As described above, according to the present embodiment, it is possible to reduce the weight of the rotor710while suppressing the decrease in the torque of the rotating electric machine700.

In particular, the rotor carrier711and the end plate723are made of a non-magnetic material, which further enhances the effect of suppressing magnetic flux leakage.

In the magnet722, the intersection of the q-axis and the magnetic flux transfer surface724is defined as the center point CP, and the circle whose radius is the radial thickness dimension of the magnet722is defined as the orientation circle X. In this case, the magnet722is configured to include a quarter circle of the orientation circle X. According to this configuration, in the magnet722, the strongest magnet magnetic flux is generated by the axis of easy magnetization passing through the orientation circle X. It is possible to avoid forming the magnetic path of the strongest magnet magnetic flux on the magnet holder721side and enhance the effect of suppressing magnetic flux leakage from the magnet722to the magnet holder721.

Sixteenth Modification

Hereinafter, a sixteenth modification will be described focusing on the differences from the fifteenth modification. As illustrated inFIG.85, the rotor carrier711, the magnet holder721, and the end plate723may be integrally molded. InFIG.85, the same configurations as those illustrated in the precedingFIG.79or the corresponding configurations are designated by the same reference signs for convenience.

According to the configuration illustrated inFIG.85, the number of components of the rotor710can be reduced. Moreover, in the configuration illustrated inFIG.85, it is not necessary to provide the rod716illustrated in the precedingFIG.82or the like.

Seventeenth Modification

Hereinafter, a seventeenth modification will be described focusing on the differences from the fifteenth modification.FIG.86illustrates a vertical cross-sectional view of the rotor710and the stator730. InFIG.86, the same configurations as those illustrated in the precedingFIG.79and the like or the corresponding configurations are designated by the same reference signs for convenience.

As illustrated inFIG.86, the rotor carrier711does not include the tubular section714. The end plate section713constituting the rotor carrier711is made of a magnetic material such as iron. The magnet holder721is fixed to the outer peripheral portion of the end plate section713in the radial direction. The magnet holder721is longer than the magnet722in the axial direction. As a result, the end plate section713and the magnet722are separated by a first distance LA in the axial direction. In addition, a second distance LB in the radial direction between the outer peripheral surface of the stator core732and the inner peripheral surface of the magnet722is smaller than the first distance LA.

According to the present embodiment described above, the magnet magnetic flux leaking from the magnet722to the stator core732via the end plate section713can be suitably suppressed without going through the magnet holder721.

Eighteenth Modification

Hereinafter, an eighteenth modification will be described focusing on the differences from the fifteenth modification. As illustrated inFIG.87, the magnet unit712has a cylindrical outer holder728fixed to the outer peripheral surface of the magnet holder721. InFIG.87, the same configurations as those illustrated in the precedingFIG.80and the like or the corresponding configurations are designated by the same reference signs for convenience.

The curvature of the outer peripheral surface of the magnet holder721is equal to the curvature of the inner peripheral surface of the outer holder728. Further, the strength of the outer holder728is higher than the strength of the magnet holder721. Moreover, the strength of each holder may be increased or decreased by, for example, different synthetic resin materials, different filler contents, or inserting a rigid mesh.

According to the present embodiment described above, the reliability of the magnet unit712for centrifugal force can be improved.

Nineteenth Modification

Hereinafter, a nineteenth modification will be described focusing on the differences from the fifteenth modification.FIG.88is a partial cross-sectional view illustrating a cross-sectional structure of the magnet unit712in an enlarged manner. InFIG.88, the axis of easy magnetization of a magnet729is indicated by an arrow. InFIG.88, the same configurations as those illustrated in the precedingFIG.80and the like or the corresponding configurations are designated by the same reference signs for convenience.

As illustrated inFIG.88, the magnet729is oriented so as to be a linear axis of easy magnetization tilted with respect to the d-axis. In the magnet729, the intersection of the d-axis and the magnetic flux transfer surface724is defined as a reference point CB, and the angle between the straight line passing through the reference point CB and the d-axis is α. According to a simulation, with respect to the orientation method illustrated inFIG.80, a torque decrease of 3% was confirmed when α=45°, and a torque decrease of 17% was confirmed when α=0°.

According to the present embodiment described above, the orientation work of the magnet729can be simplified, and the cost of the magnet729can be reduced.

Other Modifications

The configurations of the fifteenth to seventeenth modifications and the nineteenth modification may be applied to an inner rotor type rotating electric machine as an alternative to an outer rotor type rotating electric machine.For example, as illustrated inFIG.50, in the rotating electric machine500, the inlet passage571and the outlet passage572of the cooling water passage545are provided together in one place. However, this configuration may be changed, and the inlet passage571and the outlet passage572may be respectively provided at different positions in the circumferential direction. For example, the inlet passage571and the outlet passage572may be provided at positions different from each other by 180 degrees in the circumferential direction, or at least one of the inlet passage571and the outlet passage572may be provided at a plurality of positions.In the wheel400of the above embodiment, the rotating shaft501protrudes on one side in the axial direction of the rotating electric machine500, but this may be changed, and the rotating shaft501may protrude in both axial directions. As a result, for example, a suitable configuration can be implemented in a vehicle in which at least one of the front and rear of the vehicle has one wheel.It is also possible to use an inner rotor type rotating electric machine as the rotating electric machine500used for the wheel400, in the embodiment as an in-wheel motor for a vehicle and the first to fourth modifications in an in-wheel motor.The rotating electric machine is not limited to one with a star-shaped connection, but may be one with a Δ connection.

The disclosure herein is not limited to the illustrated embodiments. The disclosure includes exemplary embodiments and modifications by persons skilled in the art based on the exemplary embodiments. For example, the disclosure is not limited to the parts and/or element combinations indicated in the embodiments. The disclosure can be carried out in various combinations. The disclosure can have additional parts that can be added to the embodiments. The disclosure includes those in which the parts and/or elements of the embodiments are omitted. The disclosure includes the replacement or combination of parts and/or elements between one embodiment and another. The technical scope disclosed is not limited to the description of the embodiments. Some technical scopes disclosed are indicated by the statement of the claims and should be understood to include all modifications within the meaning and scope equivalent to the claims statement.

While the present disclosure has been described in accordance with the examples, the present disclosure is understood that the present disclosure is not limited to the examples and structures. The present disclosure also includes various modifications and modifications within an equivalent range. Additionally, various combinations and forms, as well as other combinations and forms further including only one element, more, or less, also fall within the category and scope of the present disclosure.

CONCLUSION

The present disclosure has been made in view of the above circumstances, and provides a rotating electric machine capable of reducing the weight of a rotor.

The disclosed aspects herein employ different technical means. The features and effects disclosed are made clearer by reference to the detailed description and accompanying drawings.

First means is a rotating electric machine including a stator having a stator winding, and a rotor facing the stator in a radial direction. The rotor includes a carrier having a disk-shaped end plate section fixed to a rotating shaft and arranged coaxially with the rotating shaft, and an annular magnet unit arranged coaxially with the rotating shaft. The magnet unit includes a cylindrical magnet holder of which one end in an axial direction is fixed to the end plate section, and a magnet fixed to a peripheral surface on a stator side in the radial direction in the magnet holder and having an alternating polarity in a circumferential direction. The magnet holder is made of a non-magnetic material. In the magnet, an orientation of an axis of easy magnetization on a q-axis is deviated from an orientation parallel to the q-axis.

In first means, the magnet holder is made of a non-magnetic material. Therefore, the weight of the rotor can be reduced. Here, in first means, in the magnet, an orientation of an axis of easy magnetization on a q-axis is deviated from an orientation parallel to the q-axis. According to this configuration, it is possible to suppress magnetic flux leakage from the magnet to the magnet holder and suppress a decrease in torque of the rotating electric machine as compared with a configuration including a radially oriented magnet. As described above, according to first means, it is possible to reduce the weight of the rotor while suppressing the decrease in the torque of the rotating electric machine.

Here, as the non-magnetic material constituting the magnet holder, a material having a specific gravity smaller than that of iron can be used, as in, for example, second means.

In third means, the carrier is made of a non-magnetic material in first means or second means.

According to third means, it is possible to suppress the magnetic flux leakage of the magnet through the carrier, and it is possible to enhance the effect of suppressing the torque decrease of the rotating electric machine.

In fourth means, the carrier is made of a magnetic material in first means or second means. The end plate section and the magnet are separated by a first distance in the axial direction. The stator has a cylindrical stator core assembled on an opposite-to-rotor side in the radial direction in the stator winding. A second distance in the radial direction between the peripheral surface of the stator core on a side facing the rotor and the peripheral surface of the magnet on a side facing the stator is smaller than the first distance.

According to forth means, the magnet magnetic flux leaking from the magnet to the carrier can be suitably suppressed without going through the magnet holder.

In fifth means, in any one of first means to fourth means, the magnet unit has an end plate fixed on both sides of the holder in the axial direction opposite to the carrier. The end plate is made of a non-magnetic material.

According to fifth means, it is possible to suppress the magnetic flux leakage of the magnet through the end plate, and it is possible to enhance the effect of suppressing the torque decrease of the rotating electric machine.

In sixth means, in fifth means, the end plate is made of a non-magnetic material having a specific gravity greater than a specific gravity of the holder.

According to sixth means, the amount of scraping of the end plate can be reduced in a case where the rotor is balanced about the shaft center of the rotating shaft by scraping the end plate in the manufacturing process of the rotating electric machine. Therefore, the balancing work can be facilitated.

In seventh means, in any one of first means to sixth means, the rotor is arranged outside the stator in the radial direction. The magnet unit has a cylindrical outer holder fixed to an outer peripheral surface of the magnet holder. The strength of the outer holder is higher than the strength of the magnet holder.

According to seventh means, the reliability of the magnet unit for centrifugal force can be improved.

In eighth means, in any one of first means to seventh means, a thickness dimension in the radial direction of the magnet is equal to or less than an arc length of a magnetic flux transfer surface between d-q axes.

According to eight means, the thickness of a magnet can be reduced, and the amount of the magnet used can be reduced.

In ninth means, in eighth means, in the magnet, when an intersection of the q-axis and the magnetic flux transfer surface is a center point and a circle whose radius is a radial thickness dimension of the magnet is an orientation circle that defines the axis of easy magnetization of the magnet, the magnet covers a quarter of the orientation circle.

In ninth means, in the magnet, arc-shaped axes of easy magnetization are provided so as to cross the q-axis. Of the axes of easy magnetization, the strongest magnet magnetic flux is generated by the axis of easy magnetization passing through the intersection of the peripheral surface opposite to the magnetic flux transfer surface and the q-axis in the radial direction, that is, the axis of easy magnetization passing through the orientation circle X. According to means9, it is possible to avoid forming the magnetic path of the strongest magnet magnetic flux on the magnet holder side and enhance the effect of suppressing magnetic flux leakage from the magnet to the magnet holder.

In tenth means, in any one of first means to eighth means, the magnet is oriented so as to have a linear axis of easy magnetization tilted with respect to a d-axis.

According to tenth means, orientation work can be simplified, and the cost of the magnet can be reduced.