Rotating electrical machine unit with a power inverter having a ring-shaped casing

A rotating electrical machine unit includes a rotating electrical machine including a ring-shaped stator and a rotator provided inside of the stator, and a power inverter including a ring-shaped first casing and a power module accommodated in the first casing and integrated with the rotating electrical machine by being stacked in such a manner that a lower surface of the first casing is in contact with an upper surface of the stator. The power inverter has a first coolant path formed to have a ring shape in the first casing. The power module has a heat radiation unit arranged in the first coolant path and exchanging heat with a cooling medium flowing in the first coolant path.

TECHNICAL FIELD

The present invention relates to a rotating electrical machine unit having a rotating electrical machine and a power inverter which are integrally formed.

BACKGROUND ART

A rotating electrical machine, the entire device of which is downsized by integrating a rotating electrical machine and a power inverter, is known. PTL 1 suggests a rotating electrical machine unit having a cooling unit between a rotating electrical machine and a power inverter for cooling both of the rotating electrical machine and the power inverter.

CITATION LIST

Patent Literature

SUMMARY OF INVENTION

Technical Problem

A compact rotating electrical machine unit having a high cooling performance, which can be installed on a vehicle easily, has been desired with the reduction of the size of the rotating electrical machine unit and the increase of the output of the rotating electrical machine unit.

Solution to Problem

According to a first aspect of the present invention, a rotating electrical machine unit includes: a rotating electrical machine including a ring-shaped stator and a rotator provided inside of the stator; and a power inverter including a ring-shaped first casing and a power module accommodated in the first casing, and integrated with the rotating electrical machine by being stacked in such a manner that a lower surface of the first casing is in contact with an upper surface of the stator, wherein the power inverter has a first coolant path formed to have a ring shape in the first casing, and the power module has a heat radiation unit arranged in the first coolant path and exchanging heat with a cooling medium flowing in the first coolant path.

According to a second aspect of the present invention, it is preferable that the first coolant path be formed in such a manner that a first space concavely formed to have a ring shape from the lower surface of the first casing is closed by the upper surface of the stator.

According to a third aspect of the present invention, it is preferable that the rotating electrical machine be an alternating current rotating electrical machine driven by a three-phase alternating current power, and includes an inverter circuit for converting a direct current power into an alternating current power, and the inverter circuit has first to third power modules provided for each phase, the first to third power modules are provided by connecting a pair of transistors of upper and lower arm circuits in series, the heat radiation unit has first and second radiation surfaces radiating heat from the pair of transistors, and the heat radiation unit is configured such that each of the first and second radiation surface is inserted into the first coolant path to face inner and outer peripheries of the first coolant path formed in the ring shape.

According to a fourth aspect of the present invention, it is preferable that, on the first and second radiation surfaces of the heat radiation unit of the first to third power modules, a plurality of heat radiation fins be vertically provided to protrude to the coolant path.

According to a fifth aspect of the present invention, each of the first to third power modules has a metal case having a rectangular parallelepiped shape, and surfaces of two side plates arranged to face each other in the metal case having the rectangular parallelepiped shape are the first and second radiation surfaces, respectively.

According to a sixth aspect of the present invention, it is preferable that the first power module be arranged near an inlet of the coolant path of the power inverter, and the second power module is arranged at an interval of a predetermined angle from the first power module around a center axis in an axial direction of the rotator along flow of the cooling medium introduced from the inlet of the coolant path, and the third power module is arranged at an interval of a predetermined angle from the second power module around a center axis in the axial direction of the rotator along the flow of the cooling medium.

According to a seventh aspect of the present invention, it is preferable that the rotating electrical machine unit include: a bearing that rotatably holds the ring-shaped second casing and the rotator; and a rotator holding unit integrally formed with the rotating electrical machine by being stacked in such a manner that the lower surface of the stator is in contact with the upper surface of the second casing.

According to an eighth aspect of the present invention, it is preferable that the rotator holding unit include a second coolant path formed to have a ring shape in the second casing.

According to a ninth aspect of the present invention, it is preferable that the second coolant path be formed in such a manner that a second space concavely formed to have a ring shape from the upper surface of the second casing is closed by the lower surface of the stator.

According to the tenth aspect of the present invention, it is preferable that the stator include a rib extending to an outer side, and a penetrating hole allowing communication between the first coolant path of the power inverter and the second coolant path of the rotator holding unit is provided as a communication flow channel in the rib.

Advantageous Effects of Invention

According to the invention, a compact rotating electrical machine unit having a high cooling performance, which can be installed on a vehicle easily, can be provided.

DESCRIPTION OF EMBODIMENTS

Hereinafter, an embodiment of a rotating electrical machine unit according to the present invention will be explained with reference to the drawings.

A rotating electrical machine unit according to the present embodiment is a rotating electrical machine unit suitable to be used for travel of a vehicle. Here, a so-called electric vehicle using a rotating electrical machine unit includes a hybrid electric vehicle (HEV) having both of an engine and a rotating electrical machine unit and a pure electric vehicle (EV) which runs only with a rotating electrical machine unit without using any engine. However the rotating electrical machine unit explained below can be used for both of the above-described types, and therefore, the explanation will be made based on the rotating electrical machine unit used for the hybrid electric vehicle which represents both of the types.

First Embodiment

As illustrated inFIG. 1, the rotating electrical machine unit1according to the first embodiment includes a power inverter2having an inverter circuit200and an alternating current rotating electrical machine3driven with three-phase alternating current power. The rotating electrical machine unit1is connected to a battery100on the side close to a vehicle via a relay circuit80.

The engine and rotating electrical machine3of the vehicle (not illustrated) generates torque for travel of the vehicle. The rotating electrical machine3has a function of not only generating the rotating torque but also converting a mechanical energy applied from the outside to the rotating electrical machine3into electric power.

The output torque of the engine is transmitted to the rotating electrical machine3, and the rotating torque generated by the rotating electrical machine3is transmitted to wheels via transmission and differential gears (not illustrated).

On the other hand, during driving with regenerative braking, the rotating electrical machine3is rotated by the rotating torque transmitted from the wheels and alternating current power is generated. As explained later, the generated alternating current power is converted by the power inverter2into direct current power to charge the high voltage battery100. The charged electric power is used as driving energy again.

As illustrated inFIG. 1, the relay circuit80includes a precharge resistor81, a precharge relay82, a positive-side main relay83, a negative-side main relay84, and a fuse85. The relay circuit80has a function of changing the on/off state between the circuits of the battery100and the power inverter2and auxiliary charging (precharging) for preventing inrush current when the inverter is activated.

[Circuit Configuration of Power Inverter]

As illustrated inFIG. 1, the power inverter2includes a three-phase inverter circuit200and a smoothing capacitor28. The inverter circuit200is electrically connected to the battery100via the direct current connectors11,12(21) and the relay circuit80, so that electric power is exchanged between the battery100and the inverter circuit200.

When the rotating electrical machine3is operated as an electric motor, the direct current power provided from the battery100via the direct current connectors11,12(21) is converted by the inverter circuit200into alternating current power, which is provided to the rotating electrical machine3. The rotating electrical machine unit1causes the rotating electrical machine3to operate as an electric motor with the electric power provided from the battery100, so that the vehicle can be driven with only the power of the rotating electrical machine3.

It should be noted that the rotating electrical machine unit1causes the rotating electrical machine3to operate as a power generator with the power provided by the engine or the power provided by the wheel to generate electric power, thereby charging the battery100.

The inverter circuit200has six insulated gate bipolar transistors as a switching semiconductor device. Hereinafter, the insulated gate bipolar transistor will be abbreviated as IGBT.

The inverter circuit200has a series circuit of upper and lower arms structured for each phase of three IGBTs5aand a flywheel diode6aat a positive side (upper arm side) and three IGBTs5band a flywheel diode6bat a negative side (lower arm side).

In the inverter circuit200, first to third power modules27a,27b,27cintegrated with a series circuit of upper and lower arms, which are called “2 in 1”, are provided in association with three phases, i.e., U-phase, V-phase, and W-phase. More specifically, the power inverter2has one power module27per phase, and each power module27is structured by connecting, in series, a pair of transistors of the upper and lower arm circuits.

A smoothing capacitor28is electrically connected in parallel between the direct current positive side and the direct current negative side of the power inverter2. The smoothing capacitor28is an electrolytic capacitor or a film capacitor, and is provided to suppress ripples of voltage/current caused by high-speed switching (on/off) operation of the switching semiconductor device.

Further, the power inverter2includes a control circuit, a driver circuit, and a signal connector (not illustrated). The signal connector receives a command from the control device at the vehicle side, or transmits data indicating the state of the rotating electrical machine unit1to the control device at the vehicle side. The control circuit calculates the amount of control of the rotating electrical machine3on the basis of the command which is input from the signal connector and further calculates as to whether operation is done as the electric motor or as the power generator so as to generate a control pulse on the basis of the calculation result and provide the control pulse to the driver circuit. The driver circuit generates a driving pulse for controlling the inverter circuit200on the basis of the provided control pulse.

[Structure of Rotating Electrical Machine Unit]

The structure of the rotating electrical machine unit1will be explained with reference toFIGS. 2 to 5.FIG. 2is an external perspective view illustrating the rotating electrical machine unit1.FIG. 3is an exploded perspective view illustrating the rotating electrical machine unit1.FIG. 4is a cross-sectional view illustrating a side surface of the rotating electrical machine unit1.FIG. 5is a plan view illustrating the power inverter2when a top cover53is removed. In order to avoid complexity, a rotator, a stator coil, and insulating paper are omitted inFIG. 3. InFIG. 4, the insulating paper is omitted, and the rotator7is illustrated with a two-dot chain line.

As illustrated inFIG. 2, the rotating electrical machine unit1includes a power inverter2, a rotating electrical machine3, and a rotator holding unit4. The peripheries of the power inverter2, the rotating electrical machine3, and the rotator holding unit4have octagonal shapes, and have ribs201,301,401formed with an interval of 90 degrees in the peripheral direction. The power inverter2, the rotating electrical machine3, and the rotator holding unit4are integrated with each other by being configured such that the ribs201,301,401are aligned as a rib group51and are fastened with a through bolt (not illustrated). The power inverter2and the rotator holding unit4are formed in an external shape corresponding to the external shape of the rotating electrical machine3.

[Structure of Rotating Electrical Machine]

As illustrated inFIG. 2, the rotating electrical machine3is sandwiched between the power inverter2and the rotator holding unit4. As illustrated inFIG. 4, the rotating electrical machine3includes a stator8having a ring-shaped stator core30and a stator coil32and a rotator7provided in the ring-shaped stator core30in a rotatable manner.

The stator core30is provided by stacking several hundred silicon steel plates of which thickness is about 0.05 to 1.0 mm. As illustrated inFIG. 3, the stator core30has 72 slots305formed at a regular interval in a peripheral direction in parallel to the direction of the rotation central axis (seeFIG. 4) of the rotator7. Each slot305accommodates the stator coil32.

Although not illustrated, the rotator7has a rotator core and a plurality of permanent magnets. The rotator core is provided with 12 magnet insertion holes at a regular interval in a circumferential direction. A permanent magnet, which is magnetized so that the magnetization direction thereof changes alternately for each adjacent magnetic pole, is attached to each magnet insertion hole.

[Structure Of Power Inverter]

As illustrated inFIGS. 2 to 4, the power inverter2is attached to the side at an end of the rotating electrical machine3in an axial direction. The power inverter2includes a ring-shaped inverter case20. The inverter case20is arranged such that the lower surface of the case is in contact with the upper surface of the stator core30. More specifically, the power inverter2is stacked on the rotating electrical machine3and is integrated with the rotating electrical machine3in such a manner that the upper surface of the stator8is in contact with the lower surface of the inverter case20. The inverter circuit having the first to third power modules27a,27b,27cand the smoothing capacitor28as illustrated inFIG. 1are respectively held in the inverter case20, and the inverter case20is covered with a top cover53. As illustrated inFIGS. 2 to 4, the top cover53is fixed to the inverter case20by a plurality of bolts so as to cover the side opposite to the side where the rotating electrical machine3of the inverter case20is arranged.

Further, as illustrated inFIGS. 4 and 5, a power connector21connected with a direct current circuit of the battery mounted on the vehicle and a signal connector22used to exchange various kinds of signals between the power inverter2and the vehicle side control device (seeFIG. 5) are provided on the periphery of the inverter case20. As illustrated inFIG. 5, in the inverter case20, a control circuit board23is provided over the inverter case20having an octagonal shape in planar view, and input bus bars280,281connect the smoothing capacitor28and the power connector21accommodated within the inverter case20. The inverter case20is provided with output bus bars282,283electrically connecting the smoothing capacitor28and each power module27, a current sensor29, and a resolver35(seeFIG. 4).

The direct current from the battery100is input to the power inverter2via the power connector21, and the ripple component is smoothed by the smoothing capacitor28, so as to be supplied via the output bus bars282,283to a positive-side direct current terminal272and a negative-side direct current terminal273of the power module27.

The three power modules27are switched, whereby the input direct current power is converted into alternating current power so as to be sent from an alternating current terminal271of each of the first to third power modules27a,27b,27cto the rotating electrical machine3via a lead wire33of the stator coil32connected to each alternating current terminal271. The lead wires33extending from the end portion of the stator coil32passes through a penetrating opening291of the current sensor29and is connected to the alternating current terminal271of each of the power modules27a,27b,27cof the power inverter2.

As illustrated inFIGS. 6(a) and 6(b), at the end portion, the power module27includes: the alternating current terminal271, a positive-side direct current terminal272, and a negative-side direct current terminal273for the high-current system; and a control terminal274for the low-current system (control system).

The power module27includes a rectangular parallelepiped shaped module case278made of metal material such as aluminum alloy material. The module case278has an opening at one end. Switching semiconductor devices such as IGBTs and diodes are inserted from the opening, and are sealed with resin.

The power module27is formed with a flange276to enclose the periphery of the opening of the module case278. The flange276is formed with fixing bolt holes277corresponding to attachment holes which are formed at the side close to the inverter case20. The power module27is fixed to a predetermined position by fastening the flange276by bolts.

In the module case278, the surfaces of the two side plates arranged to face each other are referred to as a first radiation surface279aand a second radiation surface279b. On each of the first radiation surface279aand the second radiation surface279b, a plurality of pin fins275are vertically provided outwardly. The first radiation surface279aand the second radiation surface279bon which the pin fins275are vertically provided are arranged within the coolant path explained later.

The duty of the switching of the power module27is calculated by the control unit of the control circuit board23on the basis of commands of a torque and a rotation speed on the side close to the vehicle, which are mainly input from the signal connector22. A switching command according to the duty is output to the control terminal274of the power module27. Signals are exchanged via signal harness, pins, and the like between the signal connector22and the control circuit board23and between the control circuit board23and the control terminal274of the power module27, which are omitted in the figure.

As illustrated inFIG. 4, at the center of the inverter case20, bearings34are provided to hold the end portions of the shaft of the rotator7in a rotatable manner. A resolver35, which is a rotation speed sensor for the rotator7, is incorporated into the upper portion of the bearing34of the inverter case20. The resolver35includes a resolver rotor (not illustrated) attached to the shaft of the rotator7and a resolver stator arranged to face the peripheral side of the resolver rotor with a gap therebetween. The signal from the resolver35is transmitted via a signal harness or signal pins (not illustrated) to the control circuit board23.

As illustrated inFIGS. 2 to 4, the rotator holding unit4is attached to the end portion of the rotating electrical machine3which is opposite, in the axial direction, to the side where the power inverter2is arranged. The rotator holding unit4includes a bearing34that rotatably holds the rotator7and a ring-shaped rear case40that accommodates the bearing34. The rear case40is arranged such that the upper surface thereof is in contact with the lower surface of the stator core30. That is, the rotator holding unit4is stacked on the rotating electrical machine3and integrated with the rotating electrical machine3in such a manner that the upper surface of the rear case40is in contact with the lower surface of the stator8.

As illustrated inFIG. 4, bearings34are provided to hold the end portions of the shaft of the rotator7at the center of the rear case40. A flange50is formed, and the rotating electrical machine unit1is fixed by fastening, using bolts, the flange50to an attachment unit such as a gear case and a transmission of the vehicle.

The coolant path formed in the inverter case20and the rear case40will be explained with reference toFIGS. 3, 4, and7.FIG. 7is a bottom schematic view illustrating flow of a cooling medium in a coolant path25in the power inverter2.

As illustrated inFIGS. 4 and 7, a coolant path25for flowing the cooling medium is formed in the inverter case20. The coolant path25is formed such that the ring-shaped concave space formed from the lower surface of the inverter case20is closed by the upper surface of the stator core30. More specifically, the coolant path25is formed to enclose the periphery of the stator coil32along the end portion of the stator core30(core back). The cross-sectional shape of the coolant path25is a rectangular shape, and is provided by three concave surfaces formed in the inverter case20and a surface251on the upper side of the stator core30. Incidentally, liquid gasket is applied between the surface251of the stator core30and the end surface of the inverter case20which is in contact with the surface251, so that the coolant path25is sealed.

As illustrated inFIG. 7, a cooling medium inlet pipe55for introducing the cooling medium from the cooling system on the side close to the vehicle (not illustrated) is attached to the inverter case20, and the cooling medium inlet pipe55is in communication with the coolant path25. A communication pipe57, which is an outlet of the coolant path25in the inverter case20, is attached to the vicinity of the cooling medium inlet pipe55.

As illustrated inFIGS. 4 and 7, a module case278of the power module27is inserted into the coolant path25, and a first radiation surface279aand a second radiation surface279bare arranged to face the inner and outer periphery of the coolant path25each formed to have a ring shape. Since the first radiation surface279aand the second radiation surface279bare arranged along the flow of the cooling medium introduced into the coolant path25, the pin fins275protrude from the first radiation surface279aand the second radiation surface279btoward the coolant path25in such a manner that the pin fins275are perpendicular to the flow of the cooling medium.

As illustrated inFIG. 7, the first power module27ais arranged in the vicinity of the cooling medium inlet pipe55of the inverter case20. The second power module27bis arranged along the flow of the cooling medium introduced from the cooling medium inlet pipe55at an interval with an angle of 45 degrees from the first power module27aabout the center axis in the axial direction of the rotator7. The third power module27cis arranged along the flow of the cooling medium introduced from the cooling medium inlet pipe55at an interval with an angle of 45 degrees from the second power module27babout the center axis in the axial direction of the rotator7.

Therefore, the cooling medium is introduced from the cooling medium inlet pipe55and flows along the stator8, thereby directly cooling the first to third power modules27a,27b,27cand the stator core30. The other components of the stator coil32and the power inverter2are cooled via the stator core30and the inverter case20which are cooled by the cooling medium. The cooling medium, which has substantially flown around in such a manner as to draw a circle along the stator8when seen in planar view, is discharged from the communication pipe57.

On the other hand, as illustrated inFIGS. 3 and 4, like the inverter case20, the rear case40is also formed with a coolant path45which is a ring-shaped in a concave manner along the stator8and the upper surface of which is open. The coolant path45is formed such that the ring-shaped concave space formed from the upper surface of the rear case40is closed by the lower surface of the stator core30. It should be noted that liquid gasket is applied between the surface451at the lower side of the stator core30and the end surface of the rear case40which is in contact with the surface451, so that the coolant path45is sealed. The other end of the communication pipe57attached to the inverter case20described above is connected to the coolant path45of the rear case40(seeFIG. 2). That is, the coolant path25of the inverter case20is in communication with the coolant path45of the rear case through the communication pipe57. A cooling medium outlet pipe56which is an outlet of the coolant path45of the rear case40is attached to the vicinity of the communication pipe57(seeFIG. 2).

Therefore, the cooling medium, which has passed from the cooling medium inlet pipe55to the coolant path25, passes through the coolant path25of the inverter case20and flows out of the communication pipe57to be introduced into the coolant path45of the rear case40. The cooling medium introduced into the coolant path45of the rear case40flows along the core back of the stator8and directly cools the rear case40of the stator core30. The cooling medium is discharged from the cooling medium outlet pipe56and is collected by a cooling system (not illustrated) on the side close to the vehicle.

According to the present embodiment as explained above, the following advantageous effects can be obtained.

(1) The coolant path25is formed to have a ring shape along the stator8at the end portion of the rotating electrical machine3in the axial direction, and the module case278of the power module27is inserted into the coolant path25. The module case278constitutes a heat radiation unit for radiating heat from the pair of transistors in the upper and lower arm circuits, and the module case278exchange heat with the cooling medium flowing in the coolant path25, and therefore, the power module27can be cooled effectively. Further, the cooling medium also cools the stator core30to cool the stator coil32via the stator core30.

(2) The power inverter2and the rotator holding unit4have an external shape corresponding to the external shape of the rotating electrical machine3, and are attached to both end portions of the rotating electrical machine3in the axial direction to sandwich the rotating electrical machine3. Therefore, the rotating electrical machine unit1which is compact but is easily installed on a vehicle can be provided.

(3) The power inverter2is attached to one side of the rotating electrical machine3, and the rotator holding unit4is attached to the other side of the rotating electrical machine3. Since the coolant paths25,45are provided in both of the power inverter2and the rotator holding unit4, the stator core30is cooled from the both end portions in the axial direction. Therefore, the stator core30and the stator coil32can be cooled effectively.

(4) The coolant path25of the power inverter2is formed such that the ring-shaped concave space formed from the lower surface of the inverter case20is closed by the upper surface of the stator8. The coolant path45of the rotator holding unit4is formed such that the ring-shaped concave space formed from the upper surface of the rear case40is closed by the lower surface of the stator8. With such a configuration, the cooling medium is directly in contact with the upper side and lower surfaces251,451of the stator core30, and therefore, the stator core30can be cooled effectively.

(5) The coolant paths25,45are formed at the end portions of the stator core30in the axial direction, and therefore, the area of the stator core30for radiation can be sufficiently ensured, and the stator core30can be cooled efficiently. Further, since the coolant paths25,45are formed around the stator coil32which is one of heat radiation bodies in the rotating electrical machine3, the stator coil32can be cooled efficiently.

The advantageous effects caused by the coolant paths25,45formed at the end portions of the stator core30in the axial direction will be explained in more detail with reference toFIGS. 8(a) and 8(b).FIG. 8(a)is a schematic view illustrating movement of heat from the stator core30according to the first embodiment, andFIG. 8(b)is a schematic view illustrating movement of heat from the stator core30when the coolant path65is provided at a side of the periphery of the stator core30. In the figures, the flow of heat is schematically illustrated by arrows.

Conventionally, as illustrated inFIG. 8(b), a coolant path65may be formed in a direction along a side surface (outside of the periphery) of the stator core30. As illustrated inFIG. 8(b), the stator core30provided by stacking several hundred of thin silicon steel plates in the axial direction is fixed to a housing60made of metal such as aluminum by shrink fit or press fit. In the housing60, the coolant path65is formed along the periphery of the stator core30.

With such a configuration, the heat of the stator coil32is transmitted to the housing60via the stator core30, and is radiated to the coolant path65. The heat passes the interface63of the housing60and the stator core30, but at this interface63, the external periphery of each stacked thin steel plate is in line contact with the inner periphery of the housing60.

Layers of air are formed between steel plates constituting the stator core30of the interface63to become thermal resistance which prevents cooling. Further, the inner wall64of the housing60interposed between the coolant path65and the stator core30also serves as thermal resistance.

In contrast, as illustrated inFIG. 8(a), in the rotating electrical machine unit1according to the first embodiment, the coolant paths25,45are formed at the end portions of the rotating electrical machine3in the axial direction, and the end surface of the stator core30can be brought into surface contact with the cooling medium. Thus, the area for radiation can be sufficiently ensured. Further, the cooling medium can be brought into direct contact with the stator core30, and the coolant paths25,45can be formed in the vicinity of the stator coil32. Thus, the cooling performance can be improved.

(6) As illustrated inFIG. 7, the cooling medium inlet pipe55is arranged in the vicinity of the power module27, and therefore, the power module27can be cooled using the cooling medium of the lowest temperature. Therefore, the power module27can be cooled efficiently.

(7) The size (product thickness) of the stator core30in the axial direction can be increased or decreased with the pitch of the plate thickness of the silicon steel plate as necessary. That is, such a structure can be easily applied to another application having the same external shape but having a different product thickness by changing only the number of stacked silicon steel plates without requiring modification of the mold of the stator core30.

(8) The ribs201,301,401are arranged at an interval of 90 degrees in the circumferential direction, and therefore, can be produced by rotating and stacking the stator core30with a pitch of 90 degrees. Thus, the rotating electrical machine unit1having the stator core30with a high degree of accuracy of shape can be provided. The term “rotating and stacking” means a method for producing the stator core30by successively arranging the plurality of stacked bodies each made of a predetermined number of thin steel plates at a predetermined angle in the circumferential direction, so as to equalize the deviation of the plate thickness.

(9) The rotating electrical machine3is, for example, a 12-pole motor of which number of slots305is 72, is provided with four ribs301. That is, an integral multiplication of the number of ribs301is the same as the number of poles of the rotating electrical machine3. Thus, the stator shape equally balanced in the rotation direction is provided, and the distribution of magnetic field does not become irregular. It is possible to prevent increase of undesired torque pulsation and noise which may be caused by the irregular distribution.

(10) Since the rotating electrical machine3and the power inverter2are integrated, a cable can be omitted as compared with a rotating electrical machine unit in which the rotating electrical machine and the power inverter are arranged separately. Therefore, the weight of the rotating electrical machine unit1can be reduced, and the noise can be also reduced.

Second Embodiment

A rotating electrical machine unit1according to a second embodiment will be explained with reference toFIG. 9. In the figure, the same or corresponding portions as those of the first embodiment will be denoted with the same reference numerals, and description thereof is omitted.FIG. 9is an external perspective view illustrating the rotating electrical machine unit1according to the second embodiment of the present invention. In the second embodiment, bearings for rotatably holding the rotator are provided in a gear case, a transmission, or the like. In the rotating electrical machine unit1, the rotator holding unit4is omitted. In the second embodiment, instead of the communication pipe57described above, a cooling medium outlet pipe56is attached to the power inverter2.

The cooling medium entered from the cooling medium inlet pipe55circulates the coolant path25of the inverter case20formed in the same manner as the first embodiment, and is discharged from the cooling medium outlet pipe56. That is, the stator core30is cooled by the cooling medium which is directly brought into contact with one of the surfaces.

According to the second embodiment, by omitting the rotator holding unit4explained in the first embodiment, the rotating electrical machine unit1which is smaller can be provided.

Third Embodiment

A rotating electrical machine unit1according to a third embodiment will be explained with reference toFIGS. 10 to 15. In the figure, the same or corresponding portions as those of the first embodiment will be denoted with the same reference numerals, and description thereof is omitted.FIG. 10is an external perspective view illustrating the rotating electrical machine unit1according to the third embodiment.FIG. 11is an exploded perspective view illustrating the rotating electrical machine unit1.FIGS. 12, 13, and 14are perspective views illustrating an inverter case20, a stator core30, and a rear case40.FIG. 15is a bottom schematic view illustrating flow of a cooling medium in a coolant path25of a power inverter2of the rotating electrical machine unit1. In each ofFIGS. 11 to 15, the flow of the cooling medium is schematically illustrated by arrows of broken lines.

As illustrated inFIGS. 11 and 13, in the third embodiment, instead of the communication pipe57explained in the first embodiment, a penetrating hole304serving as a communication flow channel allowing communication between the coolant path25of the power inverter2and the coolant path45of the rotator holding unit4is provided in the rib301of the stator core30.

As illustrated inFIG. 10, in the third embodiment, a wide rib group54is provided as compared with the first and second embodiments. Two bolt holes are provided in the rib group54. As illustrated inFIG. 13, the rib301of the stator core30extends from the stator core30to the outer side in the diameter direction. The penetrating hole304is formed at the center of the rib301, and one bolt hole302is formed at each side of the penetrating hole304(totally two bolt holes302are formed in each rib301).

The rib301of the stator core30is arranged at an interval of 90 degrees in the circumferential direction, and all of the four ribs301have the same structure. At least one of the penetrating holes304functions as the communication flow channel for passing the cooling medium, instead of the communication pipe57of the first embodiment.

Since the penetrating holes304and the bolt holes302are provided in all of the four ribs301, the stator core30can rotated and stacked.

As illustrated inFIG. 13, a flow channel cover38made of rubber, plastic, and the like is fixed to the penetrating hole304passing the cooling medium to prevent the cooling medium from immersion through the gaps between the stacked steel plates. Accordingly, when water and antifreeze liquid are used as the cooling medium, the rust of the stator core30is prevented. It should be noted that the rib group54is fastened by the bolts inserted to the both sides of the penetrating hole304, and accordingly, the sealing of the penetrating hole304passing the cooling medium is ensured.

As illustrated inFIGS. 10 and 11, the rib201of the inverter case20and the rib401of the rear case40are formed in accordance with the shape of the rib301of the stator core30. As illustrated inFIGS. 12 and 15, a dent206corresponding to the penetrating hole304of the rib301of the rotating electrical machine3is formed in the rib201in the vicinity of the end portion of the coolant path25of the inverter case20. The dent206is opened on the side close to the rotating electrical machine3and on the side close to the coolant path25(inner wall), and is in communication with the penetrating hole304of and the stator core30and the coolant path25.

Likewise, as illustrated inFIG. 14, a dent406corresponding to the penetrating hole304of the rib301in the rotating electrical machine3is formed in one of the ribs401of the rear case40. The dent406is opened on the side close to the rotating electrical machine3and on the side close to the dent406facing the coolant path25(inner wall) are open, and is in communication with the penetrating hole304of the stator core30and the coolant path45.

As illustrated inFIG. 11, the dent206of the rib201of the inverter case20(seeFIG. 12) and the dent406of the rib401of the rear case40are arranged to be in parallel with the axial direction of the rotating electrical machine3. As described above, the dent206is in communication with the coolant path25of the inverter case20(seeFIG. 12), and the dent406is in communication with the coolant path45of the rear case40(seeFIG. 14).

As illustrated inFIG. 15, the cooling medium in the rotating electrical machine unit1according to the third embodiment is introduced from the cooling medium inlet pipe55to the coolant path25of the power inverter2to flow along the stator as if it draws a circle when seen in planar view. As illustrated inFIGS. 11, 12, and 15, the cooling medium having almost made the circle flows from the dent206of the rib201into the penetrating hole304.

The cooling medium introduced from the penetrating hole304removes heat from the stator core30, and, as illustrated inFIGS. 11 and 14, the cooling medium flows to the dent406of the rib401of the rear case40to be introduced into the coolant path45. The cooling medium introduced to the coolant path45of the rear case40flows along the stator8and moves around the coolant path45. The cooling medium is then returned back from the cooling medium outlet pipe56to cooling system of the vehicle.

In the rotating electrical machine unit1according to the third embodiment, the penetrating hole304serving as a communication flow channel allowing communication between the coolant path25of the power inverter2and the coolant path45of the rotator holding unit4is provided in the stator core30. The stator8can be cooled not only by the upper surface and the lower surface of the stator core30but also by the cooling medium passing through the penetrating hole304, and therefore, the cooling performance can be improved. When a part of the outer diameter of the stator core30is enlarged, the magnetic resistance is reduced and the electric performance of the rotating electrical machine3is improved.

The following modifications are also within the scope of the present invention, and one or multiple modifications may be combined with the embodiments explained above.

(1) In the embodiments explained above, three power modules27a,27b,27cof 2-in-1 package are employed, but the invention is not limited thereto. As necessary, six power modules of 1-in-1 package may be used, or one power module of 6-in-1 package may be used.

(2) In the embodiments explained above, the IGBTs are employed as the switching semiconductor devices. However, depending on the required frequency and voltage, other semiconductor devices such as metal-oxide-semiconductor field-effect transistors (MOSFETs) may be employed. An IGBT is suitable as the switching semiconductor device when the direct current voltage is relatively high, and a MOSFET is suitable as the switching semiconductor device when the direct current voltage is relatively low.

(3) The numbers of through bolts and ribs for integrating the power inverter2, the rotating electrical machine3, and the rotator holding unit4may be increased or decreased as necessary.

(4) The power inverter2, the rotating electrical machine3, and the rotator holding unit4are fastened by the bolts to be integrated, but the invention is not limited thereto. Alternatively, the power inverter2, the rotating electrical machine3, and the rotator holding unit4may be integrated by methods such as welding and adhesion using adhesive agent.

(5) The lead wire33(seeFIG. 4) is used to extend a part of the stator coil32, but the invention is not limited thereto. Alternatively, a member corresponding to the lead wire33may be connected to the stator coil32.

(6) Control not relying on any resolver (sensor-less control) may be employed. When no resolver is used, the resolver35may be omitted.

(7) Without any harness, the signal connector22may be directly attached to the upper portion of the control circuit board23.

(8) The power module27may be an IPM having a gate driving circuit therein, or a generally-available IGBT may be used to provide a gate driving circuit on a circuit board.

(9) When the rotating electrical machine unit1is attached to the gear case, the transmission, and the like, an area inside of the stator core30(rotator side) may be cooled at the same time using cooling oil of the transmission and the like. In the rotating electrical machine unit1according to the second embodiment, the stator8may be cooled by directly blowing the cooling oil of the transmission from the opening portion at the center of the bearing for holding the rotator arranged in the transmission to the stator core30from the side opposite to the side where the power inverter2is arranged.

(10) The direction of the flow of the cooling medium is not limited to the above embodiments. The direction may be opposite to the direction of the above embodiments.

(11) The surfaces251,451of the stator core30and the contact surface of the inverter case20or the rear case40are sealed with liquid gasket, but the invention is not limited thereto. The coolant paths25,45may be sealed using an O ring or the like.

(12) The pin fins275are provided on both sides of the module case278, but the invention is not limited thereto. As illustrated inFIG. 16(a), the pin fins275may be provided on only one surface of the module case278, or as illustrated inFIG. 16(b), the surface of the module case278may be used as a heat radiation unit without providing the pin fins275. The invention is not limited to the arrangement where both sides of the first and second radiation surfaces279a,279b(seeFIG. 4) are arranged in the coolant path25. Alternatively, a heat radiation fin may be arranged on only one surface, and only one surface may be arranged in the coolant path25.

(13) The invention is not limited to the configuration where the cooling medium is brought into direct contact with the surfaces251,451of the stator core30, i.e., part of the coolant paths25,45is constituted by the surfaces of the stator. Depending on the cooling performance and the temperature of the cooling medium, a metal member with a high degree of thermal conduction may be interposed between the coolant paths25,45and the surface of the stator core30. For example, as illustrated inFIG. 17, the ring-shaped closed space may be formed in the inverter case20to provide a coolant path25, and the ring-shaped closed space may be formed in the rear case40to provide a coolant path45. Accordingly, while ensuring the waterproof property, the surfaces251,451of the stator core30can be cooled.

(14) Instead of the pin fins275provided on the module case278, the fins having various kinds of shapes such as flat plate fins may be provided. The number of fins and the shape of the fin may be determined depending on cooling performance and pressure loss required.

(15) The flange50for attachment to the vehicle may not be provided on the rotator holding unit4, and the rotating electrical machine unit1may be fixed to the vehicle using through bolts for fastening the power inverter2to the rotating electrical machine3.

(16) In the second embodiment, the rear case40is omitted. Alternatively, without omitting the rear case40, only the coolant path45of the rear case40may be omitted. Since the communication pipe57is omitted and the length in the axial direction is reduced as compared with the rotating electrical machine unit1of the first embodiment, the compact rotating electrical machine unit1can be provided.

(17) In the third embodiment, the flow channel cover38may be integrally formed, or may be made with multiple plastic plates.

(18) Instead of the flow channel cover38, a seal material may be applied to the wall surface of the penetrating hole304. The flow channel cover38may be formed of metal plate having a high degree of thermal conduction such as titanium plate.

(19) The relay circuit80may be provided in the inverter case20as part of the power inverter2.

(20) The invention is not limited to the case where the interval between the first power module27aand the second power module27band the interval between the second power module27band the third power module27care 45 degrees. The power modules27may be arranged at an interval of predetermined angles such as 30 degrees and 60 degrees.

(21) The cross-sectional shapes of the coolant paths25,45are not limited to the rectangular shapes.

In the above description, various embodiments and modifications have been explained, but the present invention is not limited thereto. Other modes, which can be derived within the technical concept of the present invention, are also included within the scope of the present invention.

The contents disclosed in the following priority application are incorporated herein by reference.