CN114696509A

CN114696509A - Liquid-cooled electric motor

Info

Publication number: CN114696509A
Application number: CN202111599765.8A
Authority: CN
Inventors: 上田正嗣
Original assignee: Hitachi Astemo Ltd
Current assignee: Hitachi Astemo Ltd
Priority date: 2020-12-28
Filing date: 2021-12-24
Publication date: 2022-07-01
Also published as: JP7482023B2; JP2022104053A

Abstract

The invention provides a liquid-cooled electric motor. A housing (20) of the motor generator (12) is composed of an inner housing (36) and an outer housing (38). The first bottom wall (46) of the inner housing (36) has an annular rib (60) and a plurality of radial ribs (62). The radial rib (62) extends from one axial side of a bowl-shaped portion (54) provided near the first bearing holding portion (52) to the first flange portion (50). The annular rib (60) is provided radially outward of the bowl (54) and connects the radial ribs (62) in the circumferential direction. O-rings (70a, 70b) are provided on the outer peripheral surface of the inner housing (36). The O-rings (70a, 70b) are in contact with the inner peripheral surface of the outer housing (38).

Description

Liquid-cooled electric motor

Technical Field

The present invention relates to a liquid-cooled electric motor that outputs a rotational driving force from a rotating shaft by rotating a rotor by energization and cools the inside with a coolant.

Background

Conventionally, a liquid-cooled electric motor is known. The liquid-cooled electric motor includes: a stator core housed inside the case; and a rotor rotatably provided inside the stator core and having a rotation shaft connected to the center thereof. The liquid-cooled electric motor obtains output by supplying electric power to a stator core to rotate the rotor. In addition, the liquid-cooled electric motor circulates a cooling liquid in order to suppress a temperature increase due to heat generated inside.

For example, a liquid electric motor disclosed in japanese patent application laid-open No. 8-237904 includes a bottomed cylindrical front case and a cylindrical rear case provided on the outer peripheral side so as to close the opening end of the front case. The rotor is rotatably provided inside the front case, and a bearing for rotatably supporting a shaft coupled to the rotor is provided at the center of the front case and the rear case.

Further, a cylindrical space is provided between the cylindrical portion of the front case and the cylindrical portion of the rear case. The liquid refrigerant circulates in the cylindrical space. An O-ring made of an elastic material is installed between one axial side of the front housing and the rear housing. An O-ring made of an elastic material is also installed between the other axial side of the front housing and the rear housing. The liquid refrigerant in the cylindrical space is prevented from flowing into the stator by the set of O-rings.

Disclosure of Invention

In general, in the liquid-cooled electric motor as described above, when the rotational speed of the rotor is increased in order to increase the output, the shaft coupled to the rotor vibrates, and along with this, the bearings supporting both ends of the shaft vibrate. This may cause the bearing holding portion holding the bearing to flex.

Due to the deformation of the bearing holding portion, a gap between the front housing and the rear housing may vary. When the liquid-cooled electric motor is used for a long period of time with the change in the gap, the O-rings disposed in the gap are repeatedly subjected to a compressive load from the front case and the rear case, and fatigue and looseness easily occur. Further, the O-ring is heated, which promotes fatigue and loosening of the O-ring. This reduces the durability of the O-ring, and shortens the replacement cycle of the O-ring.

In order to solve this problem, in the liquid-cooled electric motor disclosed in japanese patent application laid-open No. 8-237904, 2O-rings are arranged in parallel in the axial direction on the other axial side of the front case, thereby improving durability. However, by providing 2O-rings, the manufacturing cost of the liquid-cooled electric motor and the increase in the number of parts result.

The present invention has been made in view of the above problems, and it is an object of the present invention to provide a liquid-cooled electric motor having a simple structure and improved durability of an elastic sealing member.

The present invention provides a liquid-cooled electric motor including a housing, a stator and a rotor housed in the housing, the housing including an inner casing and an outer casing, the inner casing including a substantially cylindrical inner cooling wall fitted around the stator and a partition wall portion connected to one axial side of the inner cooling wall, the partition wall portion including a first bearing holding portion for holding a bearing for supporting a rotating shaft coupled to the rotor, the outer casing including a cylindrical outer cooling wall and an end wall portion covering the other axial side of the outer cooling wall, the outer cooling wall surrounding the outer side of the inner cooling wall and having a cooling flow path through which a cooling liquid flows between the outer cooling wall and the inner cooling wall, the end wall portion including a second bearing holding portion for holding a bearing for supporting the rotating shaft, an elastic seal member provided between the inner casing and the outer casing,

the partition wall portion includes:

a flange portion joined to one axial side of the outer cooling wall;

an annular wall portion that connects the first bearing holding portion and the flange portion and covers one axial side of the stator;

a bowl-shaped portion formed in a substantially cylindrical shape, opening and protruding from the first bearing holding portion toward one axial side;

a plurality of radial ribs which protrude toward one axial side with respect to the annular wall portion and connect one axial side of the bowl-shaped portion to the flange portion; and

and an annular rib which protrudes from the annular wall portion coaxially with the bowl-shaped portion and connects the radial ribs in the circumferential direction.

According to the present invention, in a liquid-cooled electric motor having a casing including an inner casing and an outer casing, the inner casing externally fitted to a stator includes: a partition wall portion formed on one axial side and having a first bearing holding portion that holds a bearing for supporting a rotating shaft, the partition wall portion including: a flange portion that is joined to one axial side of the outer cooling wall of the outer case; an annular wall portion that connects the first bearing holding portion and the flange portion and covers one axial side of the stator; and a bowl-shaped portion formed in a substantially cylindrical shape, opening and protruding from the first bearing holding portion toward one axial side. The partition wall portion includes a radial rib and an annular rib that protrude toward one axial side with respect to the annular wall portion, one axial side of the bowl-shaped portion is connected to the flange portion by the radial rib, and the plurality of radial ribs are connected in the circumferential direction by the annular rib.

Therefore, even when the rotary shaft rotates at high speed together with the rotor during high load operation of the liquid-cooled electric motor, the annular wall portion of the partition wall portion having the first bearing-retaining portion has increased rigidity due to the radial ribs and the annular ribs, and therefore deformation of the inner housing due to vibration generated when the rotary shaft rotates at high speed can be greatly suppressed.

As a result, the deformation of the inner case that occurs during high-load operation of the liquid-cooled electric motor can be suppressed by a simple structure in which the annular rib and the radial rib are provided on the partition wall portion of the inner case. Accordingly, the repetitive application of the compression load to the elastic seal member provided between the inner case and the outer case is reduced. Therefore, the durability of the elastic sealing member can be improved, and the durability of the liquid-cooled electric motor can be improved by extending the replacement cycle of the elastic sealing member.

The above objects, features and advantages will be readily understood based on the following description of the embodiments, which is described with reference to the accompanying drawings.

Drawings

Fig. 1 is an external perspective view of an electromechanical integrated drive device including a liquid-cooled electric motor according to an embodiment of the present invention.

Fig. 2 is an external perspective view of a motor generator constituting the mechatronic drive device of fig. 1, as viewed from another direction.

Fig. 3 is a front view of the motor generator shown in fig. 2.

Fig. 4 is a sectional view taken along line IV-IV in fig. 3.

Fig. 5 is a side view of the motor generator shown in fig. 2.

Detailed Description

The liquid-cooled electric motor of the present invention is used as the motor generator 12 in the mechatronic drive device 10.

The mechatronic drive device 10 is mounted on, for example, an electric vehicle and used. As shown in fig. 1 to 5, the mechatronic drive device 10 includes: a motor generator (liquid-cooled electric motor) 12 that functions as a drive source that outputs drive force; and a transmission 14 to which power from the motor generator 12 is transmitted. The motor generator 12 and the transmission 14 are integrally provided so as to be adjacent to each other in the width direction (the direction of arrows a1 and a2 in fig. 1) of the mechatronic drive device 10.

As shown in fig. 4, the motor generator 12 is, for example, a 3-phase ac brushless motor. The motor generator 12 includes: a cylindrical stator 16, a rotor 18 inserted into a central portion of the stator 16, and a casing 20 formed in a substantially cylindrical shape in an axial direction (the direction of arrows B1, B2) and accommodating the stator 16 and the rotor 18 therein. A variable reluctance type angle detector 24, for example, is provided at an end portion (the other axial side, in the direction of arrow B2) of the rotary shaft 22 coupled to the rotor 18.

The stator 16 includes, for example, a plurality of steel plates 16a stacked in the axial direction (the direction of arrows B1 and B2) and divided into segments (not shown) in the circumferential direction. The stator 16 is integrally held by being fitted with an inner housing 36 described later by assembling an outer housing 20 on the outer peripheral side thereof in a state where a plurality of divided cores are coupled to each other in the circumferential direction.

The rotor 18 is composed of, for example, a rotor main body 26 formed in a circular cross-sectional shape, and a rotary shaft 22 press-fitted into a central portion of the rotor main body 26. A plurality of magnets 28 are mounted inside the rotor body 26.

The rotary shaft 22 is a hollow shaft body that is long in the axial direction (the direction of arrows B1, B2) and is open on one side. One axial side (the direction of arrow B1) of the rotary shaft 22 is closed. The rotary shaft 22 is open to the other axial side thereof (in the direction of arrow B2). Both ends of the rotary shaft 22 in the longitudinal direction are rotatably supported in the housing 20 via a pair of first and

second bearings

30 and 32, respectively.

One axial side of the rotary shaft 22 is coupled to a reduction gear mechanism (not shown) of the transmission 14, which will be described later. A resolver rotor 34 constituting the angle detector 24 is attached to the other axial side of the rotary shaft 22.

As shown in fig. 1 to 5, the housing 20 is formed of, for example, an aluminum alloy or the like by die casting. The housing 20 includes: an inner housing 36 formed in a bottomed cylindrical shape, an outer housing 38 covering an outer peripheral side of the inner housing 36, and a cover member 40 closing the other axial side of the outer housing 38.

Housing boxes

42a and 42b that can be opened upward and sideways (one side in the width direction, in the direction of arrow a 1) are provided at the upper portion of the outer case 38. Inside the housing box 42a, for example, a power drive unit (power unit) 44 for controlling the driving of the motor generator 12, an ECU, and the like are housed. The housing box 42b houses therein, for example, a voltage converter.

As shown in fig. 2 to 4, the inner case 36 has a first bottom wall (annular wall portion) 46 on one axial side (in the direction of arrow B1). The inner housing 36 is formed in a bottomed cylindrical shape whose other axial side is open.

The inner housing 36 has: a first cylindrical wall (inner cooling wall) 48 extending from the vicinity of the outer edge of the first bottom wall 46 toward the other axial side (in the direction of arrow B2); a first flange portion (flange portion) 50 that is radially outwardly expanded from the first cylindrical wall 48 at an outer edge portion of the first bottom wall 46; and a first bearing holding portion 52 formed in the center of the first bottom wall 46 and holding the first bearing 30.

The first bottom wall 46 is formed in a substantially circular shape in cross section as viewed in the axial direction of the inner housing 36. The first bottom wall 46 extends in the vertical direction so as to be substantially orthogonal to the axis of the inner case 36. A cylindrical first bearing holding portion 52 is provided at the center of the first bottom wall 46. The first bearing retainer 52 extends toward the other axial side (the direction of arrow B2) of the inner housing 36. The first bearing 30 is press-fitted and held coaxially inside the first bearing holding portion 52. The first bearing 30 holds one side in the axial direction of the rotary shaft 22.

Further, a bowl-shaped portion 54 is provided on one axial side of the first bottom wall 46 so as to be spaced radially outward from the first bearing holder 52. The bowl 54 has an annular wall 56 projecting from the first bottom wall 46 to one axial side (in the direction of arrow B1) at a predetermined height. The bowl 54 is formed in a bowl shape that opens to the one axial side (the direction of arrow B1) from the annular wall 56 and the first bottom wall 46.

An open space 58 is provided inside the bowl-shaped portion 54, and the open space 58 communicates with the first bearing holder 52. One axial side of the rotary shaft 22 inserted through the first bottom wall 46 so as to protrude therefrom is exposed to the open space 58. As shown in fig. 4, on one axial side of the bowl-shaped portion 54, a cylindrical portion 100a of an inner case half 100 in the transmission 14, which will be described later, is fitted inside the bowl-shaped portion 54, and one axial side of the bowl-shaped portion 54 is closed.

An annular rib 60 is formed on one axial side of the first bottom wall 46 so as to be spaced radially outward from the bowl 54. The annular ribs 60 are annular and project at a predetermined height toward one axial side (in the direction of arrow B1) so as to be orthogonal to the first bottom wall 46. The annular rib 60 is provided at a predetermined interval radially outward from the annular wall 56 of the bowl 54. The annular rib 60 is formed to have a projection height from the first bottom wall 46 lower than the bowl 54, for example. The annular rib 60 is disposed at a position radially inward of the inner peripheral portion of the first flange portion 50 by a predetermined distance.

Further, a plurality of radial ribs (radial ribs) 62 are formed on one axial side of the first bottom wall 46. The plurality of radial ribs 62 radially extend outward in the radial direction around the first bearing holding portion 52. The radial ribs 62 are arranged at equal angular intervals in the circumferential direction (the direction of arrow C) with respect to the axial center of the inner housing 36. The radial rib 62 includes a first rib portion (second radial rib) 64 provided inside the bowl portion 54 and a second rib portion (radial rib) 66 provided outside the bowl portion 54. Each of the first and

second rib portions

64 and 66 extends in a straight line in the radial direction, thereby forming 1 radial rib 62.

The first rib 64 is provided to rise toward one axial side (arrow B1 direction) so as to be orthogonal to the first bottom wall 46, for example. The first rib 64 is formed to have a triangular cross section so that the protruding height gradually decreases from the inner circumferential surface of the annular wall 56 toward the radially inner side.

The second rib 66 is provided to rise toward one axial side (arrow B1 direction) so as to be orthogonal to the first bottom wall 46, for example. The second rib 66 is formed to be connected to the outer peripheral surface of the annular wall 56 at substantially the same height as the bowl-shaped portion 54, and the protruding height gradually decreases toward the outer side in the radial direction. The second rib portion 66 extends over the annular rib 60 to an inner peripheral portion of the first flange portion 50 and is connected to the first flange portion 50. That is, the second rib 66 is formed in an inclined shape (ridge line shape) inclined from the inner peripheral portion toward the outer peripheral portion toward the first bottom wall 46. The second rib 66 connects the annular wall 56 of the bowl 54 and the annular rib 60 to each other in the radial direction.

The first cylindrical wall 48 is cylindrical and extends to the other axial side (in the direction of arrow B2) at right angles to the first bottom wall 46. The inner circumferential surface of the first cylindrical wall 48 is formed with a substantially constant diameter in the axial direction, and the outer circumferential portion of the stator 16 is fitted to the inner circumferential surface, thereby integrally holding the stator 16. That is, the first cylindrical wall 48 is provided so as to cover the outer peripheral side of the stator 16.

The first cylindrical wall 48 is formed with a pair of seal holding portions 68a, 68B on one axial side (arrow B1 direction) and the other axial side (arrow B2 direction) that are on the first bottom wall 46 side. The

seal holding portions

68a and 68b are formed to be thick with their diameters expanded toward the outer peripheral side. The outer peripheral surfaces of the

seal holding portions

68a, 68b are arranged to face the inner peripheral surface of the outer housing 38. Annular grooves recessed radially inward are formed in the outer peripheral surfaces of the

seal holding portions

68a, 68b, and O-rings (elastic seal members) 70a, 70b are fitted in the annular grooves, respectively. When the outer housing 38 is attached to the outer peripheral side of the inner housing 36, the O-

rings

70a and 70b abut against the inner peripheral surface of the outer housing 38. Sealing between the inner housing 36 and the outer housing 38 is achieved by O-

rings

70a, 70 b.

A cooling flow passage 72 is formed in the outer peripheral surface of the first cylindrical wall 48. With respect to the cooling flow path 72, the cooling liquid circulates between the one seal holding portion 68a and the other seal holding portion 68 b. The cooling passage 72 is formed in an annular shape along the outer peripheral surface of the first cylindrical wall 48, for example. The cooling flow path 72 is formed as a plurality of flow paths arranged at equal intervals in the axial direction (the direction of arrows B1, B2) by a plurality of partition walls 74 protruding radially outward from the outer peripheral surface of the first cylindrical wall 48. Then, a coolant is supplied from a coolant supply source (not shown) to the cooling flow path 72, and circulates through the cooling flow path 72 by a driving action of a pumping device (not shown) such as a pump.

The first flange portion 50 is provided to connect a transmission case 96 (described later) of the transmission 14 to the motor generator 12. The first flange portion 50 has bolt holes 76 (see fig. 2 and 3) through which fastening bolts (not shown) are inserted, and a plurality of bolt holes 76 are formed along the circumferential direction (arrow C direction) of the first flange portion 50. The first flange portion 50 projects radially outward and axially outward (in the direction of arrow B1) by a predetermined length relative to the first bottom wall 46.

The outer case 38 has a second bottom wall (end wall portion) 78 on the other axial side (in the direction of arrow B2). The outer case 38 is a bottomed cylindrical shape having one side in the axial direction open. The outer case 38 has: a second cylindrical wall 80 extending in the axial direction from the vicinity of the outer edge of the second bottom wall 78; a second flange portion 82 that extends radially outward on one axial side of the second cylindrical wall 80; and a second bearing holding portion 84 formed at the center of the second bottom wall 78 and holding the second bearing 32 inserted through the rotary shaft 22. Box-shaped

storage boxes

42a and 42b are integrally provided at the upper portion and the side portion of the second cylindrical wall 80, respectively.

The second bottom wall 78 is formed in a substantially circular shape in cross section as viewed in the axial direction of the outer housing 38. The second bottom wall 78 extends in the vertical direction so as to be substantially orthogonal to the axis of the outer case 38. A cylindrical second bearing holding portion 84 is provided at the center of the second bottom wall 78. The second bearing retainer 84 extends in the axial direction (the direction of arrows B1, B2). The second bearing 32 is coaxially press-fitted and held in the second bearing holding portion 84. The second bearing 32 holds the other axial side of the rotary shaft 22. A resolver 86 constituting the angle detector 24 is provided inside the second bearing holder 84 on the other axial side (in the direction of arrow B2) than the second bearing 32.

The second bearing holding portion 84 projects to the other side (in the direction of arrow B2) in the axial direction with respect to the second bottom wall 78 by a predetermined length, and is covered with the cover member 40.

The second cylindrical wall 80 is formed in a cylindrical shape and extends in the axial direction (in the direction of arrow B1) by a predetermined length perpendicularly to the second bottom wall 78. The second cylindrical wall 80 is arranged to cover the outer peripheral side of the first cylindrical wall 48 in the inner housing 36.

The O-

rings

70a and 70b of the pair attached to the

seal holding portions

68a and 68b of the inner housing 36 abut against the inner peripheral surface of the second cylindrical wall 80. A closed cooling flow path 72 is formed between the outer peripheral surface of the first cylindrical wall 48, the pair of

seal retaining portions

68a, 68b, and the inner peripheral surface of the second cylindrical wall 80. The cooling flow path 72 is closed by the pair of O-

rings

70a and 70b provided in the inner housing 36 abutting against the second cylindrical wall 80 of the outer housing 38. The O-

rings

70a and 70b prevent the coolant circulating inside the cooling channel 72 from leaking to the outside.

As shown in fig. 1 to 5, the second cylindrical wall 80 includes a plurality of outer ribs 90 on the outer circumferential surface thereof, which protrude radially outward. The outer rib 90 includes a circumferential rib 92 formed along the circumferential direction (arrow C direction) of the outer peripheral surface of the second cylindrical wall 80, and an axial rib 94 extending along the axial direction (arrow B1, B2 direction) of the second cylindrical wall 80. The second cylindrical wall 80 is provided so as to be exposed to the outside of the housing 20.

The circumferential rib 92 is annular and protrudes at a predetermined height from the outer circumferential surface of the second cylindrical wall 80. The plurality of circumferential ribs 92 are provided and arranged at equal intervals in the axial direction of the second cylindrical wall 80. The axial rib 94 protrudes at a predetermined height from the outer peripheral surface of the second cylindrical wall 80. The axial rib 94 is formed in a straight line shape in the axial direction. The plurality of axial ribs 94 are provided and arranged at equal intervals in the circumferential direction (the direction of arrow C) of the second cylindrical wall 80. The circumferential rib 92 and the axial rib 94 intersect and are connected to each other in a substantially orthogonal manner.

That is, the outer rib 90 including the circumferential rib 92 and the axial rib 94 is disposed at a position outside the cooling flow path 72 in the second cylindrical wall 80 of the outer case 38, and has a reinforcing function of improving the rigidity of the outer case 38.

The second flange portion 82 is disposed radially outward from one axial side of the second cylindrical wall 80. The second flange portion 82 is formed in the same shape as the first flange portion 50 when viewed in the axial direction of the housing 20. The second flange portion 82 is brought into contact with the first flange portion 50, whereby the second cylindrical wall 80 of the outer housing 38 is positioned relative to the first cylindrical wall 48 of the inner housing 36 in the axial direction (the direction of arrows B1, B2). Fastening bolts (not shown) are inserted through bolt holes (not shown) of the second flange portion 82 and bolt holes 76 of the first flange portion 50, and fastened to a transmission case 96 of the transmission 14, which will be described later. Thereby, the inner case 36 and the outer case 38 are coupled by fastening bolts.

As shown in fig. 1, the transmission 14 includes a transmission case 96 and a reduction gear mechanism (not shown) housed inside the transmission case 96. The reduction gear mechanism includes a pair of output shafts 98 arranged in parallel with the rotary shaft 22 of the motor generator 12, and is linked to one side in the axial direction of the rotary shaft 22.

The transmission case 96 has: an inner case half 100 connected to one axial side (in the direction of arrow B1) of the inner case 36; and an outer case half body 102 that covers an open end of the inner case half body 100 on one axial side (in the direction of arrow B1) of the inner case half body 100. As shown in fig. 4, a part of the inner case half 100 is disposed so as to cover one axial side of the inner case 36. The cylindrical portion 100a of the inner case half 100 is fitted to the inner circumferential side of the annular wall 56 of the bowl 54 via the O-ring 70c, and is fastened to the first flange portion 50 by fastening bolts (not shown).

The inner case half 100 has a protruding portion 104 disposed close to the side of the case 20 (in the direction of arrow a 1). A differential gear mechanism (differential), not shown, is accommodated in the protruding portion 104 so as to be connected to the pair of output shafts 98, in order to distribute the driving force of the motor generator 12 to a pair of left and right driving wheels, not shown, of the vehicle, respectively.

The other of the pair of output shafts 98 is partially exposed to the outside from a projecting end of a projecting portion 104 of the inner case half 100, and is rotatably supported by the transmission case 96. One (not shown) of the pair of output shafts 98 is partially exposed to the outside from the outer case half 102 coaxially with the other of the output shafts 98, and is rotatably supported by the transmission case 96. The pair of output shafts 98 are coupled to a drive shaft (not shown) for transmitting power to a drive wheel side suspended vertically swingably by a suspension device (not shown).

The mechatronic drive device 10 using the liquid-cooled electric motor (motor generator 12) according to the embodiment of the present invention is basically configured as described above, and the operation and operational effects thereof will be described below.

First, power is supplied to the motor generator 12 in accordance with a control signal from an ECU not shown. A current is passed through a conductor (not shown) constituting the stator 16, and the conductor is excited to generate a rotating magnetic field, thereby rotationally driving the rotor 18 to which the magnet 28 serving as a magnetic pole is attached. The rotary shaft 22 rotates together with the rotor 18 in the housing 20 in a state of being supported by the first and

second bearings

30 and 32. Thereby, a rotational driving force is output from the rotary shaft 22.

In addition, the resolver rotor 34 of the angle detector 24 rotates together with the rotary shaft 22. When the resolver rotor 34 rotates, the pitch with respect to the resolver 86 changes, and the rotation angle of the resolver rotor 34, that is, the rotation angle of the rotary shaft 22 is output to an ECU (not shown) as an electric signal. Thereby, the rotation angle (rotation amount) of the rotary shaft 22 and the rotor 18 in the motor generator 12 is detected by the angle detector 24.

In the motor generator 12, when the rotor 18 and the rotary shaft 22 rotate, and the stator 16, the rotor body 26, and the magnet 28 generate heat as the rotor 18 rotates, the temperature of each part including the casing 20 rises. At this time, by supplying and circulating the coolant from a coolant supply source, not shown, to the cooling flow path 72, heat exchange between the air inside and the coolant is performed via the first cylindrical wall 48, and the housing 20 is appropriately cooled, and accordingly, the stator 16, the rotor body 26, and the magnet 28 are cooled.

Finally, the rotational driving force output from the rotating shaft 22 of the motor generator 12 is transmitted to the pair of output shafts 98 via a reduction gear mechanism and a differential gear mechanism, not shown, in the transmission 14. The rotational driving force is transmitted from the output shaft 98 to a drive shaft (not shown) for transmitting power to the drive wheel side of the electric vehicle.

When the motor generator 12 is operated at a high load in accordance with a control signal from an ECU not shown, the rotor 18 and the rotary shaft 22 coupled to the rotor 18 rotate at a high speed while being supported by the first and

second bearings

30 and 32. At this time, the first bottom wall 46 of the inner housing 36 having the first bearing holding portion 52 holding the first bearing 30 has the bowl portion 54, the annular rib 60, and the plurality of radial ribs 62, so that the rigidity is improved. Therefore, the deflection (deformation) of the inner case 36 is suppressed, and the deflection (deformation) of the outer case 38 accompanying the deflection of the inner case 36 is also suppressed.

Therefore, even when the mechatronic drive device 10 including the motor generator 12 described above is used for a long period of time, the deformation of the housing 20 occurring at the time of high-speed operation can be greatly suppressed. Therefore, repeated application of a compression load from the

seal holding portions

68a, 68b to the O-

rings

70a, 70b provided between the inner case 36 and the outer case 38 can be avoided, and fatigue and looseness of the O-

rings

70a, 70b can be suppressed, whereby durability can be improved.

As described above, in the present embodiment, in the motor generator 12 (liquid-cooled electric motor) used in the mechatronic drive device 10, the inner housing 36 accommodating the stator 16 therein includes the first bottom wall 46 formed on one side in the axial direction, and the first bottom wall 46 includes: a first flange portion 50 that is engaged with one axial side of the outer case 38; a first bearing holding portion 52 that holds a first bearing 30 capable of supporting a rotary shaft 22 coupled to the rotor 18; a bowl-shaped portion 54 that protrudes in a bowl shape toward one axial side (the direction of arrow B1) from the first bearing holder 52; a plurality of radial ribs 62 that protrude from the first bottom wall 46 toward one axial side and are connected to the first flange 50 in a spread manner from one axial side of the bowl portion 54 toward the radially outer side; and an annular rib 60 that protrudes coaxially with the bowl 54 from the first bottom wall 46 and connects the radial ribs 62 in the circumferential direction.

Therefore, the rigidity of the first bottom wall 46 of the inner housing 36 having the first bearing holding portion 52 is increased by the bowl-shaped portion 54, the annular rib 60, and the plurality of radial ribs 62, and therefore, even when the rotary shaft 22 coupled to the rotor 18 rotates at high speed in a state of being supported by the first and

second bearings

30 and 32 during high-load operation of the motor generator 12, flexure (deformation) of the inner housing 36 is suppressed. Further, the deflection (deformation) of the outer housing 38 accompanying the deflection of the inner housing 36 is also suppressed.

As a result, the deformation of the inner case 36 occurring during high load operation of the motor generator 12 can be greatly suppressed by the simple configuration of providing the bowl-shaped portion 54, the annular rib 60, and the radial ribs 62 on the first bottom wall 46 of the inner case 36. The repetitive application of compressive loads to the O-

rings

70a, 70b disposed between the inner and

outer housings

36, 38 is reduced. This can improve the durability of the O-

rings

70a, 70b, and can improve the durability of the motor generator 12 by extending the replacement cycle of the O-

rings

70a, 70 b.

Further, a plurality of first ribs 64 (radial ribs 62) connecting the annular wall 56 and the first bottom wall 46 are provided inside the bowl-shaped portion 54. Therefore, the rigidity of the bowl-shaped portion 54 and the rigidity of the vicinity of the first bearing holding portion 52 facing the bowl-shaped portion 54 can be increased by the first rib 64. As a result, the deflection of the inner housing 36 due to the vibration from the rotary shaft 22 supported by the first bearing 30 can be more appropriately suppressed.

Further, the cylindrical portion 100a of the inner case half 100 in the transmission 14 is fitted to the inner peripheral side of the bowl portion 54, whereby the rigidity of the bowl portion 54 can be further improved. Therefore, deformation of the vicinity of the first bearing holding portion 52 during high load operation of the motor generator 12 can be suppressed, and deflection of the inner housing 36 can be suppressed. Further, it is possible to reduce the occurrence of repeated application of a compressive load to the O-ring 70c provided between the cylindrical portion 100a and the bowl-shaped portion 54. As a result, the durability of the O-ring 70c can be improved.

As described above, by increasing the rigidity of the bowl-shaped portion 54 in the inner housing 36, deformation of the inner housing 36 is suppressed, and the durability of the O-

rings

70a, 70b, and 70c provided between the outer housing 38 and the transmission 14 can be improved, and the durability of the motor generator 12 as a liquid-cooled electric motor can be improved.

Further, the outer peripheral surface of the second cylindrical wall 80 of the outer case 38 is provided with a plurality of axial ribs 94 extending in the axial direction from the second flange portion 82. Therefore, even when the motor generator 12 is operated under a high load, the second cylindrical wall 80, whose rigidity is enhanced by the axial ribs 94, can be suppressed from deforming radially outward.

Further,

housing boxes

42a, 42b capable of housing a power drive unit 44 and the like that drive-controls the motor generator 12 are integrally formed in the upper portion and the side portion of the outer case 38. Therefore, the rigidity of the outer case 38 can be further improved by the

housing boxes

42a and 42 b. In other words, the

storage boxes

42a and 42b can be used as reinforcing members for improving the rigidity of the outer case 38.

The liquid-cooled electric motor according to the present invention is not limited to the above-described embodiments, and various configurations can be adopted without departing from the spirit of the present invention.

Claims

1. A liquid-cooled electric motor has a housing, and a stator and a rotor housed in the housing,

the outer case is constituted to include an inner case and an outer case,

the inner housing has a substantially cylindrical inner cooling wall that is externally fitted to the stator, and a partition wall portion that is continuous with one axial side of the inner cooling wall, the partition wall portion including a first bearing holding portion for holding a bearing that supports a rotating shaft coupled to the rotor,

the outer case has a cylindrical outer cooling wall surrounding an outer side of the inner cooling wall and having a cooling flow path through which a cooling liquid flows between the outer cooling wall and the inner cooling wall, and an end wall portion covering the other axial side of the outer cooling wall, and the end wall portion is provided with a second bearing holding portion for holding a bearing that supports the rotating shaft,

an elastic sealing member is provided between the inner case and the outer case, wherein,

the partition wall portion includes:

a flange portion that is joined to one axial side of the outer cooling wall;

a bowl-shaped portion formed in a substantially cylindrical shape, opening and protruding from the first bearing holding portion toward one side in the axial direction;

a plurality of radial ribs that project from the annular wall portion toward one axial side and connect one axial side of the bowl-shaped portion to the flange portion; and

and an annular rib that protrudes from the annular wall portion coaxially with the bowl-shaped portion and connects the radial ribs in a circumferential direction.

2. The liquid-cooled electric motor of claim 1,

the bowl-shaped portion is provided with a second radial rib extending toward the first bearing holder portion on an end surface that is on the side of the annular wall portion.

3. The liquid-cooled electric motor of claim 1,

the outer case includes an outer rib formed on an outer side of the outer cooling wall and extending in an axial direction and a circumferential direction.

4. The liquid-cooled electric motor of claim 1,

the liquid-cooled electric motor has a power unit that controls the operation of the liquid-cooled electric motor, and the power unit is housed in a housing box provided integrally with the outer case and is modularized with the liquid-cooled electric motor.