Stator for rotating electrical machine and rotating electrical machine

To improve the insulating reliability of a stator for a rotating electrical machine and the rotating electrical machine, the stator is provided with a winding having a molten metal junction, and covering material which covers the winding. The covering material has a bending part which bends to be partially in contact with the winding.

BACKGROUND OF THE INVENTION

Field of the Invention

The present invention relates to a stator for a rotating electrical machine and a rotating electrical machine, and more particularly, to a rotating electrical machine to generate a torque for automobile traveling, or to generate electric power upon braking.

Description of the Related Art

In a rotating electrical machine, a rotating magnetic field is generated by supplying alternating current (AC) power to a stator winding, then a rotor is rotated with the rotating magnetic field. Further, the mechanical energy applied to the rotor may be converted to electrical energy, to output the AC power from a coil. In this manner, the rotating electrical machine operates as an electric motor or a generator.

As a stator for this type of rotating electrical machine, a structure formed by weld-connecting segment coil terminals is known (e.g., Japanese Patent Application Laid-Open No. 2011-151975). When this type of rotating electrical machine is mounted in an automobile, it is attached in a narrow limited space. Accordingly, downsizing is required. It is necessary to realize low coil end in accordance with downsizing. Therefore it is necessary to reduce the height of the end coil and ensure an insulating distance within the narrow limited space. The problem is how to ensure a stable insulating distance in the segment coil.

SUMMARY OF THE INVENTION

The object of the present invention is to improve insulating reliability of a stator for a rotating electrical machine and the rotating electrical machine.

A stator for a rotating electrical machine according to the present invention including: a winding having a molten metal junction; and a covering material that covers the winding, wherein the covering material has a bending part that bends to be in partially contact with the winding.

The rotating electrical machine according to the present invention including: a stator having a stator core with a plurality of slots arrayed in a circumferential direction and a stator coil with an insulting film inserted in the slot; and a rotor rotatably provided with a predetermined gap with respect to the stator core, wherein in the stator coil, a plurality of segment coils having an approximate U-shaped conductor are connected, and the plurality of segment coils include a first segment coil and a second segment coil connected to the first segment coil via a weld, and wherein in the first segment coil or the second segment coil, a bellows with a coil width of the first segment coil or a coil width of the second segment coil is formed in enamel coat on the axial direction side of the weld.

According to one aspect of the present invention, it is possible to improve insulating reliability of a stator for a rotating electrical machine and the rotating electrical machine.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Hereinbelow, an embodiment of the present invention will be described with reference to the drawings.

A rotating electrical machine according to the present embodiment is a rotating electrical machine preferably available for automobile traveling. Note that so-called electric vehicles using a rotating electrical machine include a hybrid type electric vehicle (HEV) provided with both of an engine and the rotating electrical machine and a pure electric vehicle (EV) which travels only with the rotating electrical machine without engine. The rotating electrical machine described below is available for the both types of vehicles. Here a rotating electrical machine used in the hybrid type electric vehicle on behalf of the both types of vehicles will be described.

Further, in the following description, an “axial direction” means a direction along a rotary shaft of the rotating electrical machine. A “circumferential direction” means a direction along a rotational direction of the rotating electrical machine. A “radial direction” means a radial direction upon rotation about the rotary shaft of the rotating electrical machine as a center. An “inner circumferential side” means the inner side in the radial direction (inner diameter side) and an “outer peripheral side”, an opposite direction, i.e., the outer side in the radial direction (outer diameter side).

(Schematic Configuration of Vehicle)

First, a schematic configuration of a vehicle in which the rotating electrical machine is mounted will be described with reference toFIG. 14.FIG. 14is a block diagram showing a schematic configuration of a power train of a four-wheel drive hybrid vehicle. The vehicle is provided with, as a main power on the front wheel side, an engine ENG and a rotating electrical machine10. The motive power generated with the engine ENG and the rotating electrical machine10is subjected to transmission with a transmission TR, and the motive power is transmitted to a front wheel side drive wheel FW. Further, in rear wheel driving, the rotating electrical machine10provided on the rear wheel side and a rear wheel side drive wheel RW are mechanically connected to each other, and the motive power is transmitted. The rotating electrical machine10as a power source of the front wheel side is provided between the engine ENG and the transmission TR.

The rotating electrical machine10performs engine start, and selects generation of driving force, or generation of power-generating capacity to collect energy upon vehicle deceleration as electrical energy, in correspondence with vehicle traveling status. The driving and power generating operation of the rotating electrical machine10are controlled with a power conversion device INV so as to optimize torque and the number of revolutions in accordance with vehicle driving status. The electric power necessary for driving of the rotating electrical machine10is supplied from a battery BAT via the power conversion device INV. Further, when the rotating electrical machine10performs power-generating operation, the battery BAT is charged with electrical energy via the power conversion device INV.

The rotating electrical machine10is a permanent magnet built-in type three-phase synchronous motor. The rotating electrical machine10operates as an electric motor to rotate a rotor when a stator coil is supplied with three-phase alternating current. Further, when the rotating electrical machine10is driven with the engine, it operates as a generator, and outputs three-phase alternating current as generated electric power. That is, the rotating electrical machine10has a function as an electric motor to generate a rotation torque based on electrical energy and a function as a generator to perform power generation based on mechanical energy. It is possible to selectively use the functions in accordance with vehicle traveling status.

FIG. 1as a cross-sectional diagram of the rotating electrical machine10according to the present embodiment.FIG. 2is a perspective diagram of a stator20.FIG. 3is a perspective diagram of a stator core132. The rotating electrical machine10is provided inside a liquid cooling jacket130. The liquid cooling jacket130is configured with an engine case and a transmission case. The rotating electrical machine10has the stator20, a housing50to hold the stator20and a rotor11.

The liquid cooling jacket130is fixed to the outer peripheral side of the housing50. A refrigerant passage153through which a liquid refrigerant RF such as oil flows is formed with the inner circumferential wall of the liquid cooling jacket130and the outer peripheral wall of the housing50. A shaft13rotatably supported with bearings144and145provided in the liquid cooling jacket130. Accordingly, the liquid cooling jacket130also functions as a bearing bracket.

Note that in the case of direct liquid cooling, as the refrigerant RF, liquid gathered in a refrigerant (oil) storage space150flows through the refrigerant passage153, and flows from refrigerant passages154and155toward the stator20, to cool the stator20.

The stator20is fixed to the inner circumferential side of the housing50. The rotor11is rotatably supported on the inner circumferential side of the stator20. The housing50is formed in a cylindrical shape by cutting of iron material such as carbon steel, or by casting of cast steel or aluminum alloy, or by press processing, as a casing of the rotating electrical machine10. The housing50is also referred to as a frame body or a frame.

The housing50is formed in a cylindrical shape by drawing of steel plate having a thickness of about 2 to 5 mm (high tension steel plate or the like). The housing50is provided with plural flanges (unshown) attached to the liquid cooling jacket130. The plural flanges are projected outward in the radial direction at the peripheral edge of an end surface of the cylindrical housing50. Note that the flange is formed by cutting other part than the flange part at an end formed upon drawing, integrally with the housing50. Note that it may be configured such that the housing50is not provided but the stator20is directly fixed to the liquid cooling jacket130as a case.

As shown inFIG. 2, the stator20has a stator core132and a stator coil60. The stator core132shown inFIG. 3is formed by laminating silicon steel thin sheets in the axial direction. The stator coil60is wound around a large number of slots420provided in an inner circumferential part of the stator core132. Heat generation from the stator coil60is transmitted via the stator core132to the liquid cooling jacket130, and is radiated with the refrigerant RF flowing through the liquid cooling jacket130.

As shown inFIG. 1, the rotor11has a rotor core12and a shaft13.FIG. 4illustrates the cross-section of the rotor11and the stator core132. Note that inFIG. 4, the shaft13is omitted. The rotor core12is formed by laminating silicon steel thin sheets in the axial direction. As shown inFIG. 1, the shaft13is rotatably held with the bearings144and145attached to the liquid cooling jacket130, and rotates in a position opposite to the stator20in a predetermined position in the stator20. Further, although omitted inFIG. 4, the rotor11is provided with an end ring.

As shown inFIG. 4, in the stator core132, the plural slots420parallel to the axial direction of the stator core132are formed at equal intervals in the circumferential direction. The number of slots420is e.g. 72 in the present embodiment. The above-described stator coil60is accommodated in the slots420. As shown inFIG. 3, the inner circumferential side of the respective slots420are opened, and the width of the opening in the circumferential direction is approximately equal to a coil attachment part of the respective slots420to which the stator coil60is attached or slightly smaller than the coil attachment part.

As shown inFIG. 3andFIG. 4, teeth430are formed between the slots420. The respective teeth430are integrated with a ring-shape core back440. That the stator core132is an integral type core where the respective teeth430and the core back440are integrally formed. The teeth430guide rotating magnetic field generated with the stator coil60to the rotor11, and cause the rotor11to cause a rotation torque.

The stator core132is formed by punching magnetic steel sheets having a thickness of about 0.05 to 1.0 mm and laminating the formed ring-shaped magnetic steel sheets. As shown inFIG. 3, the weld200is provided in parallel to the axial direction of the stator core132at an outer peripheral part of the ring-shaped stator core132, by TIG welding or laser welding. Note that it may be configured such that the weld200is not provided but the stator core is fixed by caulking, and the stator core132is directly inserted and fixed in a case.

As shown inFIG. 4, a magnet insertion hole810in which a rectangular magnet is inserted is formed at equal intervals in the rotor core12. A permanent magnet18is inserted in the respective magnet insertion holes810and is fixed with adhesive, powder resin, or mold. The width of the magnet insertion hole810in the circumferential direction is set to be greater than that of the permanent magnet18in the circumferential direction. A magnetic gap156is formed on the both sides of the permanent magnet18. The magnetic gap156may be filled with adhesive or integrally fixed with the permanent magnet18by resin molding. The permanent magnet18forms a field pole of the rotor11.

The magnetization direction of the permanent magnet18is toward the radial direction, and the magnetization direction is reversed by field pole. That is, assuming that in one permanent magnet18forming a magnetic pole, the stator side surface is magnetized to N-pole while the axis side surface, to S-pole, in the adjacent permanent magnet18forming the adjacent magnetic pole, the stator side surface is magnetized to S-pole while the axis side surface, to N-pole. These permanent magnets18, magnetized such that the magnetization direction changes alternately by magnet pole, are provided in the circumferential direction. In the present embodiment, twelve permanent magnets18are provided at equal intervals, and twelve magnetic poles are formed in the rotor11.

Note that as the permanent magnet18, a neodymium or samarium sintered magnet, a ferrite magnet, a neodymium bond magnet or the like may be used. In the present embodiment, an auxiliary magnetic pole160is formed between the respective permanent magnets18forming the magnetic poles. The auxiliary magnetic pole160acts so as to reduce the magnetic resistance of a q-axis magnetic flux which the stator coil60generates. With the auxiliary magnetic pole160, as the magnetic resistance of the q-axis magnetic flux is very small in comparison with that of a d-axis magnetic flux, large reluctance torque occurs.

FIG. 5is a perspective diagram of the stator coil60,FIG. 6illustrates star connection as an aspect of connection of the stator coil60. In the present embodiment, a stator coil having a 2-star structure where two star connections are connected in parallel, as shown inFIG. 6, is employed as the stator coil60. That is, the stator coil60has a star connection including a U1-phase coil60U1, a V1-phase coil60V1, and a tall-phase coil60W1, and a star connection including U2-phase coil60U2, a V2-phase coil60V2, and a W2-phase coil60W2. Reference numerals N1and N2denote neutral points of the respective star connections.

The stator coil60may have a round or rectangular cross section. Note that since there is a tendency that a structure utilizing the internal cross section of the slot420as much as possible to reduce space in the slot improves efficiency, it is desirable to use the rectangular cross section. Note that regarding the length of respective sides of the rectangular cross section, the sides in the radial direction of the stator core132may be longer, or the sides in the circumferential direction may be longer.

In the stator coil60according to the present embodiment, a flat wire having a rectangular cross section is used. The longer sides of the rectangular cross section are arrayed in the circumferential direction of the stator core132in the slot420. The shorter sides are arrayed in the radial direction of the stator core132. The flat wire is coated with an insulating film on the outer periphery. As the stator coil60, oxygen-free copper or oxygen-containing copper is used. For example, in the case of oxygen-containing copper, the oxygen content is about 10 ppm to 1000 ppm.

FIG. 7Ais an explanatory diagram of a segment conductor28.FIG. 7Bis an explanatory diagram of the segment conductor28inserted in the stator core132. The U1-phase coil60U1, the V1-phase coil60V1, the W1-phase coil60W1, the U2-phase coil60U2, the V2-phase coil60V2and the W2-phase coil60W2are wave winding coils formed by connecting plural segment conductors28as shown inFIG. 7A.FIG. 7Ashows a shape of the segment conductor28before it is attached to the stator core132. The segment conductor28is formed with a flat wire, in an approximate U-shape having a pair of legs28B and a head end28C connecting them.

When the respective phase coils are formed by connecting the segment conductors28, as shown inFIG. 7B, the pair of legs28B of the segment conductor28are respectively inserted into different slots420from one side of the stator core132in the axial direction. Thereafter, the legs28B sticking out to the other side of the stator core132in the axial direction are folded in the direction where the segment conductor28to be connected is provided, and an end28E of the leg28B is welded to the end28E of the other segment conductor28.

As shown inFIG. 5, the set of the head ends28C sticking out to the one side of the stator core132forms a coil end61on one side of the stator coil60. The set of the ends28E sticking out to the other side of the stator core132forms a coil end62on the other side of the stator coil60. In the following description, the coil end62will be referred to as a welding side coil end62, and the coil end61, a counter-welding side coil end61.

On the side of the counter-welding side coil end61, a lead wire41U1connected to an end of the U1-phase coil60U1and a lead wire41U2connected to an end of the U2-phase coil60U2are pulled out. The lead wire41U1and the lead wire41U2are gathered in a bunch with an alternating terminal42U. Similarly, on the side of the counter-welding side coil end61, lead wires41V1and41V2connected to ends of the V1-phase coil60V1and the V2-phase coil60V2are gathered in a bunch with an alternating terminal42V. Lead wires41W1and41W2connected to ends of the W1-phase coil60W1and the W2-phase coil60W2are gathered in a bunch with an alternating terminal42W.

Further, on the side of the counter-welding side coil end61, neutral point connection conductors40N1and40N2are provided. The neutral point connection conductor40N1relates to the neutral point N1(seeFIG. 6) in one star connection, and the neutral point connection conductor40N2, to the neutral point N2in the other star connection.

The stator coil60is wound by distributed winding. In the distributed winding, the phase coils are wound around the stator core132such that the phase coils are accommodated in two slots420with plural slots420between the two slots (seeFIG. 3). In the present embodiment, as the distributed winding is employed as winding, the formed magnetic flux distribution is nearer to a sine wave in comparison with that formed in concentrated winding, and a reluctance torque is easily caused. Accordingly, in the rotating electrical machine10, the controllability to utilize weak field control and reluctance torque is improved. It is possible to utilize the rotating electrical machine10in a wide rotational speed range from a low rotational speed to a high rotational speed, and to obtain an excellent motor characteristics appropriate to electric vehicles.

FIG. 8illustrates the U-phase coil60U for one phase of the stator coil60shown inFIG. 5. As shown inFIG. 6, the U-phase coil60U is configured with the U1-phase coil60U1for one star connection and the U2-phase coil60U2for the other star connection.FIG. 9illustrates the U1-phase coil60U1, andFIG. 10illustrates the U2-phase coil60U2. As shown inFIG. 9andFIG. 10, the neutral point connection conductor40N1is connected to the other end of the U1-phase coil60U1. The neutral point connection conductor40N2is connected to the other end of the U2-phase coil60U2.

Next, the technique of production of the stator20according to the present embodiment will be described. As described above, the segment conductor28in the status shown inFIG. 7Ais inserted into the slot of the stator core132. Then, as shown inFIG. 7B, the legs28B are bent toward the direction of the other segment conductor28to be connected.

FIG. 11illustrates the arrangement of the ends28E1to28E4in the welding side coil end62after the bending.FIG. 11is a perspective diagram of the welding side coil end62, andFIG. 12is a plane view of the welding side coil end62viewed from the axial direction.

Four columns of segment conductors28are inserted in the slots420in the radial direction, and the legs28B inserted in the slots420are provided with a slot liner310. With the slot liner310, it is possible to improve the withstand voltage between the segment conductors28and between the segment conductor28and the inner surface of the slot420. Note that in the ends28E1to28E4where connection performed, the insulating film is removed and the conductor is exposed. The bent part of the insulating film is provided with a bending part400. The bending part400is provided closer to the end to be connected than the bending part of the covering material. In this manner, since a bellows is formed in the enamel coat on the axial direction side, the bending part400mitigates burning of the enamel coat after welding. Further, as the part is immersed in varnish after the welding, the insulation is improved. The bending part400forms bending before welding. The bending part is formed by molding with an R 0.1 to 0.5 jig, and molding the bending part400using enamel coat having small spread with respect to the conductor. Note that the non-bending part means a part of the insulating film having a contact, area wider than that with respect to the segment conductor28in the bending part400.

Further, in the welding side coil end62, insulating paper300is provided between the four columns of segment conductors28arrayed in the radial direction. The insulating paper300is provided, to improve inter-phase insulation and inter-conductor insulation in the welding side coil end62, between the segment conductor28, in a ring shape along the circumferential direction. Note that insulating paper300also functions as a holding member to prevent dripping of resin material (e.g. polyester or epoxy liquid varnish) when dropped on the entire or part of the stator coil60.

To this manner, since the insulating paper300and the slot liner310are provided inside the slot and at the coil end, even when the insulating film of the segment conductor28is damaged or degraded, it is possible to maintain necessary withstand voltage. Note that the insulating paper300is an insulating sheet of e.g. heat-resistant polyamide paper having a thickness of about 0.1 to 0.5 mm.

The respective legs28B pulled out from the respective slots420are bent in the direction of the segment conductor28to be connected while the four column arrangement is maintained. For example, the leg28B1, inserted in the first column on the inner circumferential side in the slot420, is bent to the left side in the circumferential direction. Meanwhile, the leg28B2having the end28E2connected to the end28E1of the leg28B1is, although not shown, inserted in the second column of the slot420on the left side from the end28E2in the figure, and is bent to the right side in the circumferential direction from the slot420. The ends28E1and28E2are provided to be adjacent o each other in the radial direction. Further, the end28E3and the end28E4, connected to each other, are provided sequentially in the radial direction on the outer peripheral side of the end28E2.

Next, to align the heights of the end28E1to the end28E4and suppress the coil end height, cutting process is performed on the end28E1to the end28E4.FIG. 12illustrates the end28E1to the end28E4viewed from the direction of the tip.FIG. 13is a partial perspective diagram of the welding side coil end62. The bending part400is formed in the enamel coat on the axial-direction side.

Next, as shown inFIG. 13, the end28E1and the end28E2are connected to each other and the end28E3and the end28E4are connected to each other, by welding the end tips. A base material is melt and set, and formed as a weld800, in the end28E1and the end28E2, and in the end28E3and the end28E4. As welding, the base material of the segment conductor28is melted by TIG welding of arch welding or plasma welding for connection. As shield gas, argon gas or helium gas, further, gaseous mixture of argon gas and helium gas, or the like, is used. With the bending part400, it is possible to prevent burning of the enamel coat upon welding. Further, as the enamel coat has a bellows structure, the insulating distance is ensured with respect to the coil. It is possible to improve the insulation. Further, as the immersion of the varnish from the entrance of the bellows structure improves the insulation.

According to the above-described embodiment, the following advantages are obtained.(1) As described above, in the production technique of the stator20for a rotating electrical machine, having the stator core132where the plural slots420are formed, and the stator coil60formed by connecting the plural segment conductors28having a rectangular cross section inserted in the slots420, the tips of the ends28E1to28E4of a pair of mutually connected segment conductors28have a molten metal junction, and the insulating film has a bending part to bend to be in partially contact with the stator coil.

In this manner, by providing the bending part400to bend before welding, as shown inFIG. 11, an insulating distance to the coil is ensured by preparing the enamel coat having the bellows structure, and the insulation is improved. Further, as immersion of varnish from the entrance of the bellows structure improves the insulation.(2) For example, as shown inFIG. 11, the bending part may be formed in the enamel coat on the axial direction side. Otherwise, it is possible to improve the insulation by forming the bending part on the both sides in the axial direction.

The rotating electrical machine10as a motive power source on the front wheel side shown inFIG. 14is provided between the engine ENG and the transmission TR. It has a configuration described withFIG. 1toFIG. 13. As the rotating electrical machine10as a driving force source for the rear wheel side, similar machine may be used, or other rotating electrical machines having a general configuration may be used. Note that it goes without saying that the invention is applicable to hybrid electric vehicles other than the four wheel drive electric vehicles.

As described above, according to the present invention, it is possible to provide a stator for a rotating electrical machine which is a small and high output stator and which has excellent insulation.

In the above description, the embodiment has been explained, however, the present invention is not limited to these contents. Other aspects considered within the scope of the technical idea of the present invention are included in the scope of the present invention.