WO2020098190A1

WO2020098190A1 - Hub motor drive system and motor vehicle

Info

Publication number: WO2020098190A1
Application number: PCT/CN2019/077943
Authority: WO
Inventors: 蔡向阳
Original assignee: 舍弗勒技术股份两合公司; 蔡向阳
Priority date: 2018-11-13
Filing date: 2019-03-13
Publication date: 2020-05-22
Also published as: CN111169274A; DE112019005658T5; WO2020098494A1; CN113226821A

Abstract

A hub motor drive system applied to a motor vehicle. In the hub motor drive system, a first bearing (51a) and a first sealing assembly (51c) are provided between a housing body (1) and a sun gear axle (51). Compared with the prior art that a bearing and a sealing assembly are provided between a housing body and a rotor support, the structure of the rotor support (4) is greatly simplified, and a sealing surface of the sun gear axle (51) used for arranging the sealing assembly can also be conveniently processed to improve the sealing effect. Also provided is a vehicle using the hub motor drive system.

Description

Wheel hub motor drive system and motor vehicle

Technical field

The present invention relates to the field of motor vehicles such as electric vehicles, and particularly to a hub motor drive system for a motor vehicle and a motor vehicle including the hub motor drive system.

Background technique

In the prior art, new energy vehicles such as electric vehicles integrate drive motors, planetary gear reducers, wheel bearings, and brake systems into the wheel space to form a hub motor drive system, where the drive motor can directly drive the wheels There is no need for a transmission and drive shaft.

FIG. 1 shows a partial structural schematic diagram of a prior art hub motor drive system, in which a rotor bracket for supporting a rotor of a drive motor and a sun gear shaft of a planetary gear reducer are shown.

As shown in FIG. 1, the rotor bracket 10 includes a first axial portion 101, a second axial portion 102, and a third axial portion 103 each extending along the axial direction A and an edge for connecting the three portions together Radial portion 104 which extends in the radial direction R. In addition, the rotor bracket 10 further includes a stepped portion 105 provided at an axial side (left side in FIG. 1) end of the second axial portion 102 and fixed to the sun gear shaft 20.

Specifically, among the first axial portion 101, the second axial portion 102, and the third axial portion 103, the first axial portion 101 is located at the radially outermost position, and the second axial portion 102 is located at the radial most In the inner position, the third axial portion 103 is interposed between the first axial portion 101 and the second axial portion 102 in the radial direction R and extends from the substantially central portion of the radial portion 104 toward the axial side. The first axial portion 101 is used to fix the rotor of the drive motor, and a part of the radially outer side of the second axial portion 102 (the portion on the left side in the figure) is formed as a mounting surface 102S for mounting a bearing, and The radially outer side surface of the third axial portion 103 is formed as a sealing surface 103S for contacting with the seal assembly, the above bearing is used to support the rotor bracket 10 to the housing assembly of the in-wheel motor drive system, and the above seal assembly is used for the in-wheel motor The seal between the housing assembly of the drive system and the rotor bracket 10. Further, a wheel bearing for fitting the output shaft is installed in a space inside the second axial portion 102 in the radial direction. The step portion 105 is fixed to the sun gear shaft 20 by welding at the position indicated by the reference symbol P.

In this way, the prior art hub motor drive system has the following defects:

I. The structure of the rotor bracket 10 is complicated, it is difficult to deal with the sealing surface 103S, and it is easy to cause leakage problems;

II. It is difficult to control the deformation of the rotor bracket 10 and the sun gear shaft 20 due to the use of a welded connection, thus causing NVH problems; and

III. The distance between the geometric center of the wheel bearing and the stress point of the wheel is too large, which will reduce the life of the wheel bearing and the output shaft matched with the wheel bearing is prone to large-scale deformation.

Summary of the invention

The present invention has been made based on the above-mentioned defects of the prior art. An object of the present invention is to provide a new type of hub motor drive system, which avoids the problem of easy leakage due to the difficulty in processing the sealing surface in the prior art. The invention also provides a motor vehicle including the in-wheel motor drive system.

In order to achieve the above object of the invention, the present invention adopts the following technical solutions.

The present invention provides a hub motor drive system that includes a housing assembly including a housing body and a housing cover assembled axially opposite each other, An installation space is formed inside the housing assembly; a drive motor is housed in the installation space, and the drive motor includes a stator fixed relative to the housing body and a radial position of the stator An inner rotor that can rotate relative to the stator; a rotor bracket that supports the rotor from the radially inner side and is fixed to the rotor; and a planetary gear reducer, the planetary gear reducer is located at the installation Outside the space, and the planetary gear reducer further includes a sun gear shaft drivingly coupled with the rotor bracket to be able to rotate with the rotor bracket, wherein the rotor bracket includes an axial portion extending in the axial direction and A radial portion extending radially inward from the axial portion, the axial portion fixedly supports the rotor, the radial portion is drivingly coupled with the sun gear shaft, and the hub motor drive system further includes A first bearing and a first seal assembly at a first gap between the housing body and the sun gear shaft and located on an axial side of the radial portion of the rotor bracket.

Preferably, the first gap is formed with a first opening that opens toward the axial side, and the first bearing is located closer to the first opening than the first seal assembly.

Preferably, the radial portion is fixed to the sun gear shaft through an interference fit; or the radial portion is drivingly coupled to the sun gear shaft through a spline connection.

More preferably, an annular protrusion is formed on the radial outer surface of the sun gear shaft, the radial portion and the annular protrusion realize the interference fit, and the radial portion is formed with a radial direction A limit portion protruding inside and abutting the end surface on the other side in the axial direction of the ring-shaped protrusion makes the rotor bracket positioned in the axial direction relative to the sun gear shaft.

Preferably, the in-wheel motor drive system further includes a second bearing disposed at a second gap between the housing cover and the sun gear shaft and located on the other axial side of the radial portion of the rotor bracket And the second seal assembly.

More preferably, the second gap is formed with a second opening that opens toward the other side in the axial direction, and the second seal assembly is located closer to the second opening than the second bearing.

Preferably, the planetary gear reducer further includes a plurality of planetary gears located radially outward of the sun gear shaft, and a portion of the sun gear shaft including one axial end thereof is formed to mesh with the plurality of planet gears External teeth.

More preferably, the first bearing and the first seal assembly are provided at a portion of the sun gear shaft on the axially other side than the external teeth.

More preferably, the external teeth are subjected to gear modification after the heat treatment of the sun gear shaft.

Preferably, the sun wheel shaft has a hollow structure, and the in-wheel motor drive system further includes a wheel bearing, and the wheel bearing is disposed on the sun wheel shaft in such a manner that the distance between the geometric center and the wheel stress point is minimized internal.

More preferably, the geometric center of the wheel bearing and the wheel stress point overlap in the axial direction.

The present invention provides a motor vehicle whose wheels include the in-wheel motor drive system described in any one of the above technical solutions.

By adopting the above technical solution, the present invention provides a new in-wheel motor drive system and a motor vehicle including the in-wheel motor drive system. The in-wheel motor drive system is provided between the housing body and the rotor bracket in the prior art. The bearing and the sealing assembly are arranged between the casing body and the sun gear shaft, which not only can greatly simplify the structure of the rotor bracket compared with the prior art rotor bracket, but also can facilitate the sealing surface of the sun gear shaft for setting the sealing assembly Treatment to improve the sealing effect.

BRIEF DESCRIPTION

1 is a schematic cross-sectional view of a partial structure of a hub motor drive system according to the prior art.

2 is a schematic cross-sectional view of an in-wheel motor drive system according to an embodiment of the present invention.

3a is a schematic cross-sectional view of the partial structure of the hub motor drive system in FIG. 2; FIG. 3b is a schematic cross-sectional view of the rotor bracket of the hub motor drive system in FIG. 2; FIG. 3c is a schematic view of the hub motor drive system in FIG. A schematic cross-sectional view of the sun gear shaft.

DESCRIPTION OF REFERENCE NUMERALS

10 Rotor bracket 101 First axial part 102 Second axial part 102S mounting surface 103 Third axial part 103S sealing surface 104 Radial part 105 Stepped part 20 Sun gear shaft

1 Housing main body 2 Housing cover 3 Drive motor 31 Stator 32 Rotor 4 Rotor bracket 41 Axial part 42 Radial part 43 Limit part 5 Planetary gear reducer 51 Sun gear shaft 51a First bearing 51b Second bearing 51c First seal Assembly 51d second seal assembly 51p annular projection 51g external teeth 52 planetary gears 53 planetary carrier 53a thrust roller bearings 54 ring gear 6 output shaft 61 flange portion 62 shaft portion 62a wheel bearing 62b wheel bearing lock nut 6a output Shaft seal assembly 7 Knuckle sleeve 8 Sensor 9 Braking system 91 Brake drum 92 Brake disc

S installation space A axis R radial direction.

detailed description

Hereinafter, specific embodiments of the present invention will be described in detail with reference to the accompanying drawings of the specification. In this specification, "axial", "radial" and "circumferential" refer to the axial, radial and circumferential directions of the housing assembly (including the housing body and housing cover) of the hub motor drive system, One axial side refers to the left side in FIGS. 2 to 3c, and the other axial side refers to the right side in FIGS. 2 to 3c. In addition, "wheel stress point" refers to the projection of the intersection between the wheel midplane and the center axis of the wheel on the tire ground surface, and "transmission coupling" refers to the drive between the two components through a fixed connection structure or transmission mechanism. Force / torque transmission.

As shown in FIG. 2, the in-wheel motor drive system according to an embodiment of the present invention includes a housing assembly (including a housing body 1 and a housing cover 2) assembled together, a driving motor 3, a rotor bracket 4, and planetary gear reduction器 5 和 output 轴 6。 5 and the output shaft 6.

In this embodiment, the entire housing assembly composed of the housing body 1 and the housing cover 2 has a substantially cylindrical shape. The housing body 1 is located on one side of the housing cover 2 in the axial direction and is formed with an opening toward the other side in the axial direction. The housing cover 2 is opposed to the housing body 1 in the axial direction A and assembled with the housing body 1 in such a manner as to cover the opening of the housing body 1, so that the housing body 1 and the housing cover 2 surround to form an installation space S. The bottom of the housing body 1 opposite to the opening is formed in a bent shape and the housing cover 2 is also formed in a bent shape so that the dimension of the installation space S between the housing body 1 and the housing cover 2 in the axial direction A It decreases from the radially outer side toward the radially inner side. In addition, both the casing body 1 and the casing cover 2 are formed with a through hole at the center for passing through the sun gear shaft 51 and other components described below.

In this embodiment, the entire drive motor 3 is accommodated in the installation space S. The drive motor 3 includes a stator 31 and a rotor 32 each having an annular shape.

Specifically, the stator 31 is located on the radially inner side of the housing body 1 and fixed relative to the housing body 1, and a cooling assembly is preferably provided between the stator 31 and the outer periphery of the housing body 1 to reduce the stator 31 in the drive motor 3 The temperature during work.

The rotor 32 is located radially inward of the stator 31 and is opposed to the stator 31 in the radial direction R. The rotor 32 can rotate relative to the stator 31 so that the rotor 32 can rotate in the magnetic field when the stator 31 generates a magnetic field.

In this embodiment, the rotor holder 4 supports the rotor 32 and has a cylindrical shape as a whole. As further shown in FIGS. 3a and 3b, the rotor bracket 4 includes an axial portion 41, a radial portion 42 and a limiting portion 43.

Specifically, the axial portion 41 extends along the axial direction A, and the axial portion 41 is fixed to the rotor 32 from the radially inner side to support the rotor 32. The length of the axial portion 41 in the axial direction A is substantially equal to the length of the rotor 32 in the axial direction A.

The radial portion 42 extends radially inward from a substantially central portion of the axial portion 41 in the axial direction A and extends from the installation space S to be fixed with the sun gear shaft 51 described below. The radially inner end of the radial portion 42 forms a thickened portion having a larger size in the axial direction A and is used to fix the annular protrusion 51p of the sun gear shaft 51 by interference fit, for example. In this embodiment, the surface on the axial side of the radial portion 42 does not have any convex shape.

The limiting portion 43 extends radially inward from the thickened portion and serves to abut against the annular projection 51p of the sun gear shaft 51 from the other side in the axial direction, thereby defining the rotor holder 4 relative to the sun gear shaft 51 in the axial direction A s position.

In this way, the rotor bracket 4 of the in-wheel motor drive system according to the present invention has a much simplified structure compared to the conventional rotor bracket 10 shown in FIG. 1 and is easier to process.

In the present embodiment, the planetary gear reducer 5 is entirely located outside the installation space S formed by the housing body 1 and the housing cover 2 and the planetary gear reducer 5 is entirely disposed radially inward of the stator 31, and the planetary gear reducer The device 5 is arranged coaxially with the drive motor 3. Further, the planetary gear reducer 5 includes a sun gear shaft 51, a plurality of planet gears 52, a planet gear carrier 53 and a ring gear 54 assembled with each other, wherein a part of the sun gear shaft 51, a plurality of planet gears 52, a planet gear carrier Both the 53 and the ring gear 54 are arranged on the axial side of the rotor 32. In other words, the other structures of the planetary gear reducer 5 except for the other part of the sun gear shaft 51 are arranged on the axial side of the rotor 32. In this way, it can be ensured that the planetary gear reducer 5 can be filled with more oil, so that the lubricating performance and cooling performance are better.

Specifically, the sun gear shaft 51 is a hollow shaft, and the sun gear shaft 51 extends through the central through holes of the housing body 1 and the housing cover 2 along the axial direction A, so that the sun gear shaft 51 and the housing body 1 and the housing cover 2 Both overlap in the axial direction A.

In the radial direction R, a first gap is formed between the sun gear shaft 51 and the housing body 1, and a second gap is formed between the sun gear shaft 51 and the housing cover 2. The first bearing 51a and the first seal assembly 51c arranged in the axial direction A are provided in the first gap, and the second bearing 51b and the second seal assembly 51d are arranged in the axial direction A in the second gap. Both

bearings

51a, 51b are radial bearings and are used to support the rotation of the sun gear shaft 51 relative to the housing body 1 and the housing cover 2 in the radial direction R. Both sealing

assemblies

51c, 51d have an annular shape, the first sealing assembly 51c is preferably fitted to the housing body 1 by an interference fit, and the second sealing assembly 51d is preferably fitted to the housing cover 2 by an interference fit, and The two

seal assemblies

51c, 51d are used to prevent foreign substances (including lubricating media) from entering the installation space S. In the axial direction A, both the first bearing 51 a and the first seal assembly 51 c are separated from the second bearing 51 b and the second seal assembly 51 d by the radial portion 42 of the rotor bracket 4.

In the axial direction A, the first bearing 51a is located on the axial side of the first seal assembly 51c. That is, the first bearing 51a is closer to the opening of the first gap toward the axial side than the first seal assembly 51c. In this way, the lubricating medium flowing into the first gap can provide a lubricating effect to the first bearing 51a. In the axial direction A, the second seal assembly 51d is located on the other axial side of the second bearing 51b. That is, the second seal assembly 51d is closer to the opening of the second gap toward the other side in the axial direction than the second bearing 51b.

Further, a ring-shaped protrusion 51p is formed on the radial outer surface of the sun gear shaft 51. The ring-shaped protrusion 51p and the radial portion 42 of the rotor bracket 4 have an interference fit, thereby fixing the rotor bracket 4 to the sun gear shaft 51. The limiting portion 43 of the rotor holder 4 abuts on the axially opposite end surface of the annular protrusion 51p, so that the rotor holder 4 is positioned in the axial direction A relative to the sun gear shaft 51.

In addition, a portion of the sun gear shaft 51 facing the plurality of planet gears 52 is formed with external teeth 51g that are engaged with the planet gears 52. This solution of directly forming the external teeth 51g on the sun gear shaft 51 is simpler and easier to implement than the prior art solutions in which the sun gear shaft and the sun gear are independently manufactured and assembled together. In addition, in the process of processing the sun gear shaft 51, after the sun gear shaft 51 is heat-treated, it is also possible to easily perform gear tooth modification on the external teeth 51g, so that the NVH problem of the gear teeth can be optimized. In this embodiment, the first bearing 51a and the first seal assembly 51c are provided on the sun shaft 51 on the axially other side than the external teeth 51g. Preferably, the part of the sun gear shaft 51 where the first seal assembly 51c and the second seal assembly 51d are provided can be surface-treated to improve the sealing performance.

A plurality of planet gears 52 are located radially outside of the sun gear shaft 51 and are evenly distributed along the circumferential direction. Each planet gear 52 is formed with teeth meshing with the external teeth 51g of the sun gear shaft 51 so that each planet will rotate as the sun gear shaft 51 rotates The gear 52 is capable of rotating around its respective central axis and revolving around the sun gear shaft 51.

The planetary carrier 53 is located radially outward of the sun gear shaft 51, and the planetary carrier 53 is fixed to the output shaft 6 while mounting a plurality of planet gears 52. As the planetary gear 52 revolves, it can drive the planetary carrier 53 to rotate and then drive the output shaft 6 to rotate.

The ring gear 54 is located radially outward of the plurality of planet gears 52 and is fixed to the housing body 1, and a track for the plurality of planet gears 52 to revolve is formed between the ring gear 54 and the sun gear shaft 51. The ring gear 54 is formed with a plurality of The teeth of the planet gear 52 mesh.

In the present embodiment, the output shaft 6 is a flanged shaft. The output shaft 6 includes a flange portion 61 and a shaft portion 62 that are formed integrally. The output shaft 6 is arranged coaxially with the planetary gear reducer 5.

The flange portion 61 is formed in a disk shape and extends radially outward from the shaft portion 62. The flange portion 61 is fixed to the planetary carrier 53 by a fixing member, so that the entire output shaft 6 can follow the planetary carrier 53 Turns while turning.

The shaft portion 62 protrudes from the center of the flange portion 61 toward the other side in the axial direction and extends into the inside of the hollow sun gear shaft 51 in the axial direction. The wheel bearing 62a is fitted to the shaft portion 62 from the outside in the radial direction, and the wheel bearing 62a is arranged coaxially with the drive motor 3 and the planetary gear reducer 5. In addition, the wheel bearing 62 a is arranged inside the sun gear shaft 51. In this way, the projection of the geometric center of the wheel bearing 62a on the tire ground contact surface can be arranged to substantially coincide with the wheel stress point, which is beneficial to the improvement of stability and avoids the problem of large-scale deformation of the output shaft in the prior art.

In this embodiment, the wheel bearing 62 a can be attached to the shaft portion 62 by the wheel bearing lock nut 62 b cooperating with the flange portion 61. In addition, the wheel bearing 62a is a ball bearing, preferably a double row ball bearing, so that the friction force of the wheel bearing 62a during operation is small, and the efficiency of the drive system is improved.

By adopting the above configuration, on the one hand, the driving force / torque can be sequentially transmitted to the output shaft 6 via the rotor 32, rotor bracket 4, sun gear shaft 51, planet gear 52, and planet gear carrier 53 in the in-wheel motor drive system to drive The hub, which ultimately drives the wheel. In this way, the drive motor 3 directly drives the wheels of the motor vehicle without passing through the conventional transmission and drive shaft outside the wheels, so the transmission path of the driving force / torque is shortened compared to the drive system of the prior art motor vehicle, so that the improvement Drive the efficiency of the system and reduce the energy loss in the transmission process.

On the other hand, the coaxial arrangement of the drive motor 3, planetary gear reducer 5, wheel bearing 62a and output shaft 6 can greatly save the space occupied by the hub motor drive system, and the hub motor drive system is integrated with the wheels This facilitates the layout of the vehicle and reduces the effects of spatial interference when the vehicle is in bumps and turns.

In this embodiment, the in-wheel motor drive system may further include a knuckle sleeve 7, a sensor 8, and a braking system 9.

The knuckle sleeve 7 is located between the sun axle 51 and the wheel bearing 62a to cooperate with other components of the knuckle assembly to achieve steering control of the wheels.

The sensor 8 is provided in the installation space S and is provided in the housing cover 2 and the rotor bracket 4. The sensor 8 is used to monitor parameters such as the rotation speed of the drive motor 3.

The braking system 9 is located on the other side in the axial direction of the sun gear shaft 51 and on the radially inner side of the housing cover 2. The braking system 9 includes a brake drum 91 and a brake that are sleeved on the knuckle sleeve 7 from the radially outer side The disc 92, the brake drum 91 and the brake disc 92 are opposed to each other in the axial direction A and cooperate with each other to be able to brake the in-wheel motor drive system.

The present invention also provides a motor vehicle whose wheel includes a hub motor drive system having the above structure.

The specific embodiment of the in-wheel motor drive system according to the present invention has been described in detail above, but it needs to be supplemented that:

I. The in-wheel motor drive system according to the present invention may further include other necessary components that are not described in the above specific embodiments.

For example, in addition to the above-mentioned

seal assemblies

51c and 51d, other seal assemblies may be provided at necessary locations in the in-wheel motor drive system, for example, between the flange portion 61 of the output shaft 6 and the housing body 1 There is a seal assembly 6a, and a seal assembly 6a may be provided between the flange portion 61 and the sun gear shaft 51. The main function of these seal assemblies 6a is to isolate different spaces in the drive system so that media such as oil will not circulate between the spaces separated by these seal assemblies 6a.

In addition, a thrust roller bearing 53a may be provided in the axial gap between the housing body 1 and the planetary carrier 53 to support the planetary carrier 53 in the axial direction A.

II. Although it has been described in the above specific embodiments that the rotor bracket 4 and the sun gear shaft 51 are fixed together by an interference fit, the present invention is not limited to this. In fact, as long as the rotor bracket 4 and the sun gear shaft 51 achieve transmission coupling so that the sun gear shaft 51 can rotate with the rotor bracket 4, the rotor bracket 4 and the sun gear shaft 51 can be splined to achieve transmission coupling or The same welding technique as in the prior art can also be used.

III. Although the above specific embodiment has explained that the projection of the geometric center of the wheel bearing 62a on the tire ground contact surface is substantially coincident with the wheel stress point, in many cases, the above-mentioned coincidence effect cannot be achieved. Therefore, the technical idea of the present invention is realized as long as the distance between the geometric center of the wheel bearing 62a and the wheel stress point is as small as possible.

Claims

A hub motor drive system. The hub motor drive system includes:

A housing assembly including a housing body and a housing cover assembled together opposite to each other in the axial direction, and an installation space is formed inside the housing assembly;

A drive motor, the drive motor being accommodated in the installation space, the drive motor including a stator fixed relative to the housing body and a rotor located radially inward of the stator and capable of rotating relative to the stator;

A rotor bracket that supports the rotor from the radially inner side and is fixed to the rotor; and

A planetary gear reducer located outside the installation space, and the planetary gear reducer further includes a sun gear shaft drivingly coupled with the rotor bracket to be able to rotate with the rotor bracket,

Wherein, the rotor bracket includes an axial portion extending axially and a radial portion extending radially inward from the axial portion, the axial portion fixedly supports the rotor, and the radial portion is The sun gear shaft drive coupling, the hub motor drive system further includes a first gap disposed between the housing body and the sun gear shaft and located on an axial side of the radial portion of the rotor bracket The first bearing and the first seal assembly.
The in-wheel motor drive system according to claim 1, wherein the first gap is formed with a first opening that opens toward the axial side, and the first bearing is located closer to the first seal assembly The location of the first opening.
The in-wheel motor drive system according to claim 1 or 2, wherein

The radial portion is fixed to the sun gear shaft through an interference fit; or

The radial portion is drivingly coupled with the sun gear shaft through a spline connection.
The in-wheel motor drive system according to claim 3, wherein an annular protrusion is formed on the radial outer surface of the sun gear shaft, and the radial portion and the annular protrusion realize the interference fit ,and

The radial portion is formed with a limiting portion that protrudes toward the radially inner side and abuts against the other end surface of the annular protrusion in the axial direction, so that the rotor bracket is axially oriented with respect to the sun gear shaft Up positioning.
The in-wheel motor drive system according to any one of claims 1 to 4, wherein the in-wheel motor drive system further includes a second gap provided between the housing cover and the sun gear shaft and A second bearing and a second seal assembly located on the other axial side of the radial portion of the rotor bracket.
The in-wheel motor drive system according to claim 5, wherein the second gap is formed with a second opening that is open toward the other side in the axial direction, and the second seal assembly is located more than the second bearing By the position of the second opening.
The in-wheel motor drive system according to any one of claims 1 to 6, wherein the planetary gear reducer further includes a plurality of planetary gears located radially outward of the sun gear shaft, and the sun gear shaft A portion including one axial end thereof is formed with external teeth meshing with the plurality of planet gears.
The in-wheel motor drive system according to claim 7, wherein the first bearing and the first seal assembly are provided at a portion of the sun gear shaft on the axially other side than the external teeth.
The in-wheel motor drive system according to claim 7 or 8, wherein the external teeth are subjected to gear modification after the heat treatment of the sun gear shaft.
The in-wheel motor drive system according to any one of claims 1 to 9, wherein the sun gear shaft has a hollow structure, and the in-wheel motor drive system further includes a wheel bearing, the wheel bearing having a geometric center The distance between the stress points of the wheels is set inside the sun gear shaft so as to be the smallest.
The in-wheel motor drive system according to claim 10, wherein the geometric center of the wheel bearing and the wheel stress point overlap in the axial direction.
A motor vehicle whose wheels include the in-wheel motor drive system according to any one of claims 1 to 11.