CN108274988B

CN108274988B - Wheel-side electric driving system with dynamic vibration absorption function

Info

Publication number: CN108274988B
Application number: CN201710009927.5A
Authority: CN
Inventors: 陈辛波; 王威; 孙浩棋; 李坚勤; 朱剑飞; 王叶枫; 重松隆史; 朱福堂; 董婷婷
Original assignee: Robert Bosch GmbH
Current assignee: Robert Bosch GmbH
Priority date: 2017-01-06
Filing date: 2017-01-06
Publication date: 2022-12-06
Anticipated expiration: 2037-01-06
Also published as: CN108274988A

Abstract

An electric wheel rim drive system comprising: a motor (1); a gearbox (2) for transmitting power between the electric machine (1) and a wheel axle shaft (5), said gearbox (2) having at least two gear change mechanisms, wherein the electric machine (1) is fixed to a first housing part of the gearbox (2) carrying the first gear change mechanism; a knuckle (15) for steering the wheel; and an elastic shock-absorbing element (20) which is connected to the knuckle (15) at a first connection point at a first end and to the first housing part at a second connection point at a second end, so that the motor (1) and at least a part of the mass of the first housing part constitute a dynamic shock-absorbing mass.

Description

Wheel-side electric driving system with dynamic vibration absorption function

Technical Field

The present application relates to a wheel-side electric drive system with a dynamic vibration absorbing function, which is easily combined with a conventional suspension system of a vehicle.

Background

Plug-in electric or hybrid vehicles may include a discretely mounted electric drive system to enable individual drive to each wheel. Decentralized electric drive systems include drive wheel in-mount or wheel-side mount motors. The advantages of the decentralized electric drive system are short power transmission chain, high transmission efficiency, compact structure and the like. Also, each electric drive system may be independently controlled such that each electric drive system may be rapidly adjusted in driving force or braking force, so that vehicle dynamic performance may be improved. Further, the drive wheels of the disengagement control can realize torque vectoring control, thereby improving turning stability.

Large mass motors are typically mounted in or near the drive wheel and the unsprung mass is therefore significantly increased, which results in an imbalance in the ratio between the sprung and unsprung masses of the vehicle, and poor drivability, particularly vertical performance, of the vehicle. One effective way to reduce the effective unsprung mass is to add a dynamic vibration absorber to the wheel. Patent document CN102555770A proposes a motor as a mass of a dynamic vibration absorber, wherein a two-stage transmission is used, with a spring-damper of the dynamic vibration absorber disposed therebetween.

There is no focus in the above documents on the application in various types of suspensions. When a wheel-side mount type drive system having such a dynamic vibration absorber is mounted on an existing conventional suspension, much interference occurs between the wheel-side mount type drive system and the multi-link type suspension. For example, since the motor center axis is radially close to the wheel center axis, there is a possibility that interference may occur between the knuckle and the trailing arm, between the motor and the damper, and between the motor and the lower control arm.

Disclosure of Invention

The present application aims to avoid interference when mounting a wheel-side drive system to an existing conventional vehicle suspension, and at the same time effectively suppress an increase in unsprung mass of the vehicle.

To this end, according to one aspect of the present application, there is provided a wheel-rim electric drive system with a dynamic-vibration absorbing function, including: a motor; a transmission for transmitting power between the electric machine and the wheel axle shafts, said transmission having at least two speed change mechanisms, wherein the electric machine is connected to the first speed change mechanism and is secured to a first housing portion of the transmission carrying the first speed change mechanism; a knuckle for steering a wheel; and an elastic vibration-absorbing element having a first end connected to the knuckle at a first connection point and a second end connected to the first housing section at a second connection point, such that the motor and at least a portion of the mass of the first housing section constitute a dynamic vibration-absorbing mass.

According to a possible embodiment, the number of elastic shock-absorbing elements is multiple, the first and/or second connection points of each elastic shock-absorbing element being located at different radial and/or axial positions.

According to one possible embodiment, the first connection point of the at least one elastic shock-absorbing element is located lower than its second connection point, and the first connection point of the at least one elastic shock-absorbing element is located higher than its second connection point.

According to one possible embodiment, the elastic shock-absorbing elements are positioned such that, when the wheel moves up and down relative to the body, one or some of the elastic shock-absorbing elements are extended while the other or some of the elastic shock-absorbing elements are shortened.

According to one possible embodiment, the intermediate shaft forms the output of the first stage of the gear change mechanism and the input of the second stage of the gear change mechanism, and the motor shaft of the electric motor is arranged on that side of the intermediate shaft which is remote from the half shafts, so that the radial distance between the motor shaft and the half shafts is greater than the radial distance between the intermediate shaft and the half shafts.

According to a possible embodiment, the angle between the line between the central axis of the motor shaft and the central axis of the intermediate shaft and the line between the central axis of the intermediate shaft and the central axis of the half shaft, viewed in the axial direction of the wheel, is an obtuse angle or a straight angle.

According to a possible embodiment, the gearbox has a single casing structure comprising said first casing portion and a second casing portion carrying the second-stage transmission mechanism, the first and second casing portions being integral; the motor and the entire gearbox have one degree of freedom of rotation about the half-shafts relative to the knuckle from which they are suspended by the elastic shock-absorbing element.

According to a possible embodiment, the gearbox has a double casing structure comprising the first casing part and a second casing part carrying a second stage gear shifting mechanism, the second casing part being fixed together with the steering knuckle; the intermediate shaft constitutes an output of the first stage transmission and an input of the second stage transmission, the motor and said first housing portion having a degree of freedom of rotation about the intermediate shaft relative to the second housing portion and the knuckle, the motor and said first housing portion being suspended from the knuckle by means of an elastic shock-absorbing element.

According to a possible embodiment, the first and second casing parts are connected by a rotary joint formed by their respective tubular portions, through which an intermediate shaft passes, and bearings and seals are provided between the respective tubular portions of the first and second casing parts.

According to a possible embodiment, an additional elastic shock-absorbing element is provided between the first housing part and the second housing part.

According to a possible embodiment, the first stage transmission mechanism comprises a first gear pair and the second stage transmission mechanism comprises a second gear pair; and the first gear pair and/or the second gear pair are/is provided with idler gears for increasing the radial distance between the motor and the half shaft.

According to the application, the elastic shock absorption element is arranged between the steering knuckle and the gearbox body, sufficient space is provided for arranging the elastic shock absorption element and other parts of the wheel-side electric driving system, and the flexibility of the layout of the wheel-side electric driving system is improved, so that the wheel-side electric driving system can be arranged at a position which does not interfere with a conventional suspension system. In addition, the entire transmission or a portion of the transmission and the motor have a degree of freedom to rotate within a limited range, thereby constituting a dynamic vibration absorber structure that effectively suppresses an increase in the unsprung mass of the vehicle and improves the dynamic performance of the vehicle.

Drawings

The foregoing and other aspects of the present application will be more fully understood from the following detailed description, taken with reference to the accompanying drawings, in which:

FIG. 1 is a schematic layout of a wheel-side electric drive system according to one possible embodiment of the present application;

FIG. 2 is a schematic layout view of the wheel-side electric drive system of FIG. 1 taken in an axial direction;

FIG. 3 is a schematic layout of a wheel-side electric drive system according to another possible embodiment of the present application;

fig. 4 is a schematic layout view of the wheel-side electric drive system of fig. 3 taken along the axial direction.

Detailed Description

A possible embodiment of the wheel-rim electric drive system with dynamic vibration absorbing function of the present application is described below with reference to the accompanying drawings. It is to be noted, however, that the drawings presented herein are for illustration purposes only and are not intended to limit the scope of the present disclosure in any way. In order to highlight certain features, the various parts of the drawing are not to scale and some features are indicated schematically by dash-dot lines, and some are omitted and not shown.

A wheel-rim electric drive system with dynamic shock-absorbing function according to one possible embodiment of the present application is schematically shown in fig. 1. Each drive wheel of the vehicle is equipped with such a wheel-side electric drive system, respectively, in which the output rotational motion and torque of the electric motor 1 arranged on the side of the wheel close to the drive wheel are transmitted to the wheel through the transmission 2, thereby driving the wheel in rotation. The wheel and the wheel-side electric drive system thereof are arranged on the suspension system.

The gearbox 2 is a single-box type gearbox, i.e. the gearbox box is an integrated structure, and two-stage speed change (generally, speed reduction) mechanisms are arranged in the gearbox box. The motor 1 is fixed on the gearbox body.

The gearbox casing carries a motor shaft 3, an intermediate shaft 4 and a half shaft 5 of the wheel. The motor shaft 3 defines a central axis of the motor 1 and extends from the motor 1 into the gearbox housing for inputting the rotational movement and torque of the motor 1 into the gearbox 2. The half-shafts 5 define the central axis of the wheels and project from the gearbox casing. The intermediate shaft 4 is located in the gearbox housing.

A first drive gear 6 is supported on the motor shaft 3, a first driven gear 7 and a second drive gear 8 are supported on the intermediate shaft 4, and a second driven gear 9 is supported on the axle shaft 5.

The first drive gear 6 is meshed with the first driven gear 7 to constitute a first-stage transmission mechanism of the transmission case 2. The second drive gear 8 meshes with the second driven gear 9 to constitute a second-stage transmission mechanism of the transmission 2. These gears are located in the gearbox casing. A first casing section of the transmission casing carrying the first-stage transmission mechanism is integral with a second casing section carrying the second-stage transmission mechanism.

The gear shaft 3 constitutes an input end of the first-stage speed change mechanism, the intermediate shaft 4 constitutes an output end of the first-stage speed change mechanism and an input end of the second-stage speed change mechanism, and the half shaft 5 constitutes an output end of the second-stage speed change mechanism.

The motor shaft 3 is arranged on the side remote from the half-shafts 5 with respect to the intermediate shaft 4, so that the radial distance between the motor shaft 3 and the half-shafts 5 is greater than the radial distance between the intermediate shaft 4 and the half-shafts 5. As shown in fig. 2, an angle α between a line between the center axis O1 of the motor shaft 3 and the center axis O2 of the intermediate shaft 4 and a line between the center axis O2 of the intermediate shaft 4 and the center axis O3 of the half shaft 5 is an obtuse angle or a straight angle, i.e., 90 ° < α ≦ 180 °, as viewed in the axial direction of the wheel. This may be described as an obtuse or straight angular distribution between the two speed reduction mechanisms. In this way, the radial distance between the electric machine 1 and the centre axis of the wheel can be increased, i.e. the electric machine 1 is arranged radially away from the centre axis of the wheel, in order to avoid that the electric machine 1 and the gearbox 2 connected thereto interfere with the centre axis of the wheel and the suspension system structures (not shown) in the vicinity.

In order to provide a sufficient radial distance between the electric motor 1 and the wheel center axis, an idler gear 10 may be provided between the second drive gear 8 and the second driven gear 9, as shown in the drawing. Of course, alternatively or additionally, an idler gear may also be provided between the first drive gear 6 and the first driven gear 7.

The axle shaft 5 is connected to a hub 11, and the hub 11 supports a rim 12, such as by bolts 13 securing the rim 12 to the hub 11. The hub 11 rotates with the axle shaft 5. In addition, a brake disc 14 is supported on the hub 11.

The half-shafts 5 rotatably pass through knuckles 15 of the wheels, and the knuckles 15 are used to steer the wheels. The knuckle 15 is journalled in a sleeve 17 fixed to the axle shaft 5 by means of bearings 16. The knuckle 15 supports a brake element 18, such as a brake caliper. The brake element 18 may be secured to the knuckle 15 by bolts 19.

Further, between the transmission case 2 and the knuckle 15, an elastic shock absorbing element 20 is provided. In the example shown, the elastic shock-absorbing element 20 is of the linear type and mainly comprises a spring and a damper; of course, various other forms of resilient shock-absorbing elements used in the art may be used herein.

The elastic shock-absorbing element 20 is connected to the knuckle 15 at a first end and to the gearbox 2 at a second end. In this way, the motor 1 and the transmission case 2 are elastically suspended together on the knuckle 15, so that a part of the mass of the motor 1 and the transmission case 2 acts as a mass for absorbing vibration. The motor 1 and the gearbox 2 thus form a dynamic vibration absorbing system with the elastic vibration absorbing element 20. The motor 1 and the gearbox 2 have a degree of freedom to rotate a little back and forth around the centre axis of the wheel, i.e. the centre axis of the half-axle 5.

When the vehicle is running, the wheels are impacted by an uneven road surface and vibrate up and down. In this process, the motor 1 and the transmission 2 are repeatedly rotated a little bit around the wheel center axis, thereby absorbing vibration energy by causing the elastic vibration absorbing elements 20. In this way, the dynamic performance of the vehicle, including ABS, TCS, ESP, and torque vectoring, among others, may be improved. Furthermore, a portion of the mass of the motor 1 and the transmission 2 becomes the sprung mass, which helps to adjust the ratio between the sprung and unsprung masses of the vehicle, suppressing an increase in the unsprung mass of the vehicle, and further improving the drivability, particularly the vertical performance, of the vehicle.

By providing the elastic shock-absorbing element 20 between the knuckle and the housing of the gearbox 2, sufficient space is provided for arranging the elastic shock-absorbing element 20 and other components of the wheel-side electric drive system, so that parts of the existing suspension system are easily avoided, making the wheel-side electric drive system easy to integrate with the existing suspension system.

In the axial direction of the wheel, the gearbox 2 is located between the wheel and the electric machine 1, i.e. the gearbox 2 is located axially inside the wheel, and the electric machine 1 is in turn located axially inside the gearbox 2, as shown in fig. 1. In the gearbox 2, a first transmission mechanism associated with the electric machine 1 is located axially inside a second transmission mechanism associated with the half-shafts 5. In this way, the motor 1 and the gearbox 2 occupy as little space as possible in the vicinity of the central axis of the wheel, in order to further avoid the motor 1 and the first-stage transmission connected thereto interfering with the central axis of the wheel and with the suspension system structure (not shown) in the vicinity.

It will be appreciated that the dynamic vibration absorbing system may include more than one elastic vibration absorbing element 20, and that the first end of each elastic vibration absorbing element 20 may be attached to the knuckle 15 at the same attachment point a, while the second end of each elastic vibration absorbing element 20 is attached to the transmission housing at a different attachment point B1, B2 \8230 (as shown in fig. 2). Alternatively, the first end of each elastic shock absorbing element 20 may be connected to the knuckle 15 at a different connection point, while the second end of each elastic shock absorbing element 20 is connected to the gearbox housing at the same connection point. Alternatively, the first ends of the respective elastic shock-absorbing elements 20 may be connected to the knuckle 15 at different connection points, while the second ends of the respective elastic shock-absorbing elements 20 are also connected to the gearbox housing at different connection points, respectively. The connection positions of the two ends of each elastic shock-absorbing element 20 are designed such that the elastic shock-absorbing elements 20 function in coordination with each other when the wheel moves up and down relative to the vehicle body. Different points of attachment, as used herein, are intended to mean different radial and/or axial positions.

For example, according to one possible embodiment, the elastic shock-absorbing elements 20 are each attached to the gearbox housing at a point having a smaller height than their attachment point a to the knuckle 15 or to a part fixed with respect to the knuckle 15.

As another example, according to another possible embodiment, the height of the point B1 of attachment of one (or some) of the elastic shock-absorbing elements 20 to the gearbox housing is greater than its point a of attachment to the knuckle 15 or to a part fixed with respect to the knuckle 15, and the height of the point B2 of attachment of the other (or some) of the elastic shock-absorbing elements 20 to the gearbox housing is less than its point a of attachment to the knuckle 15 or to a part fixed with respect to the knuckle 15, so that when the wheel moves up and down with respect to the body, one (or some) of the elastic shock-absorbing elements 20 elongates and the other (or some) of the elastic shock-absorbing elements 20 shortens.

Other possible numbers and attachment locations of the elastic shock-absorbing elements 20 may be designed according to the specific construction and requirements.

A wheel-rim electric drive system with dynamic-shock-absorbing function according to another possible embodiment of the present application is schematically shown in fig. 3. The function of the wheel-side electric drive system is similar to that shown in fig. 1. The output rotational motion and torque of the motor 1 disposed on the side of the wheel near the driving wheel are transmitted to the wheel through the transmission 2, thereby driving the wheel to rotate.

The gearbox 2 is a double-casing gearbox, i.e. the gearbox casing comprises two casing parts, a first casing part 21 and a second casing part 22, for carrying a two-stage gear change (typically both reduction) mechanism.

The motor 1 is fixed to the first housing part 21. The first housing portion 21 and the second housing portion 22 are connected by a rotary joint 23 formed by their respective tubular portions so that the first housing portion 21 can rotate relative to the second housing portion 22 about the rotary joint 23. The rotary joint 23 is formed by respective tubular portions of the first and

second housing portions

21, 22 and includes a bearing 24 and a seal 25 between the respective tubular portions of the first and

second housing portions

21, 22. The second housing part 22 is fixed to the knuckle 15, for example by means of bolts 27.

Between the first housing part 21 and the knuckle 15, an elastic shock-absorbing element 20 is provided. In the example shown, the elastic shock-absorbing element 20 is of the linear type and mainly comprises a spring and a damper; of course, various other forms of resilient shock-absorbing elements used in the art may be used herein. The elastic shock-absorbing element 20 is connected at a first end to the knuckle 15 and at a second end to the first housing part 21.

By providing the elastic shock-absorbing element 20 between the knuckle and the first housing part 21, sufficient space is provided for arranging the elastic shock-absorbing element 20 and other parts of the wheel-side electric drive system, so that parts of the existing suspension system are easily avoided and integration with the existing suspension system is facilitated.

As an optional feature, an additional elastic shock-absorbing element 26 may be arranged between the first housing part 21 and the second housing part 22. The elastic shock-absorbing element 26 is connected to the second housing part 22 at a first end and to the first housing part 21 at a second end. The elastic shock-absorbing elements 26 may be of the linear type or of the torsional type, and the number of elastic shock-absorbing elements 26 may be one or more.

The first housing part 21 carries the motor shaft 3, the second housing part 22 carries the half-shaft 5, and the intermediate shaft 4 extends between the first housing part 21 and the second housing part 22 through a rotary joint 23. The intermediate shaft 4 has the same central axis as the rotary joint 23.

The first drive gear 6 located in the first housing portion 21 meshes with the first driven gear 7 to constitute a first-stage speed change mechanism of the transmission case 2. A second driving gear 8 located in the second casing section 22 meshes with a second driven gear 9 to constitute a second-stage transmission mechanism of the gearbox 2.

The gear shaft 3 constitutes the input of the first stage transmission, the intermediate shaft 4 constitutes the output of the first stage transmission and the input of the second stage transmission, and the half shaft 5 constitutes the output of the second stage transmission.

The motor shaft 3 is arranged on the side remote from the half shafts 5 with respect to the intermediate shaft 4 such that the radial distance between the motor shaft 3 and the half shafts 5 is greater than the radial distance between the intermediate shaft 4 and the half shafts 5. As shown in fig. 4, an angle α between a line between the center axis O1 of the motor shaft 3 and the center axis O2 of the intermediate shaft 4 and a line between the center axis O2 of the intermediate shaft 4 and the center axis O3 of the half shaft 5 as viewed in the axial direction of the wheel is an obtuse angle or even a flat angle, thereby increasing the radial distance between the motor 1 and the wheel center axis defined by the half shaft 5, i.e., the motor 1 is disposed radially away from the wheel center axis to avoid the motor 1 and the first-stage speed change mechanism connected thereto from interfering with the wheel center axis and a suspension structure (not shown) in the vicinity thereof.

The axle half 5 is connected to a hub 11, the hub 11 supporting a rim 12, the rim 12 being secured to the hub 11, for example by bolts 13. The hub 11 rotates with the axle shaft 5. In addition, a brake disc 14 is supported on the hub 11.

The half shaft 5 rotatably passes through the knuckle 15. The knuckle 15 is mounted by means of bearings 16 on a sleeve 17 fixed to the axle shaft 5. The steering knuckle 15 supports a brake element 18, such as a brake caliper. The brake element 18 may be secured to the knuckle 15 by bolts 19.

The motor 1 together with the first housing part 21 is elastically suspended from the knuckle 15 by means of the elastic shock-absorbing element 20, so that a part of the mass of the motor 1 and the first housing part 21 acts as a shock-absorbing mass. The motor 1 and the first housing part 21 thus form a dynamic-vibration absorbing system with the elastic vibration absorbing element 20 (and possibly the elastic vibration absorbing element 26). The motor 1 and the first housing part 21 have a degree of freedom to rotate a little back and forth around the central axis of the intermediate shaft 4. The addition of the additional resilient shock-absorbing element 26 increases the flexibility of the design of the dynamic shock-absorbing system.

Also, it will be appreciated that the dynamic-vibration absorbing system may include more than one elastic vibration absorbing element 20, which may be arranged as in the previous embodiments of figures 1 and 2.

When the vehicle is running, the wheels are impacted by an uneven road surface and vibrate up and down. In this process, the motor 1 and the first casing section 21 are repeatedly rotated a little bit about the central axis of the intermediate shaft 4, thereby absorbing vibration energy by causing the elastic vibration absorbing element 20 (and possibly the elastic vibration absorbing element 26). In this way, the dynamic performance of the vehicle can be improved. Furthermore, the motor 1 and the first case portion 21 and a part of the mass of the first stage transmission mechanism become sprung masses, which helps to adjust the ratio between the sprung and unsprung masses of the vehicle, suppressing an increase in the unsprung mass of the vehicle, thereby further improving the drivability of the vehicle, particularly the vertical performance.

In the axial direction of the wheel, the gearbox 2 is located between the wheel and the electric machine 1, i.e. the gearbox 2 is located axially inside the wheel, and the electric machine 1 is in turn located axially inside the gearbox 2, as shown in fig. 3. In the transmission case 2, a first case portion 21 fixed with the motor 1 is located axially inside a second case portion 22 fixed with the axle shaft 5. In this way, the electric motor 1 and the first housing part 21 occupy as little space as possible in the vicinity of the central axis of the wheel, in order to further avoid the electric motor 1 and the first housing part 21 connected thereto from interfering with the central axis of the wheel and with the suspension structure (not shown) in the vicinity.

Other aspects of the embodiment shown in fig. 3 and 4 are similar or identical to the embodiment shown in fig. 1 and 2 and will not be repeated.

Although the gearbox 2 in the above described example is a two-stage gearbox, the gearbox 2 may also be a three or more stage gearbox, depending on the specific requirements.

It can be seen that according to the present application, the drive motor of the wheel and the gearbox (or part of the gearbox) are given a degree of freedom to rotate within a limited amplitude, so that part of their mass constitutes the mass of the dynamic-vibration-absorbing system of the wheel, whereby the vibration energy of the wheel, which is generated by the action of the ground, is absorbed by means of the elastic vibration-absorbing element, so that the dynamic behaviour of the vehicle can be improved. Furthermore, since a portion of the mass of the motor and the transmission (or a portion of the transmission) becomes the sprung mass, the ratio between the sprung and unsprung masses of the vehicle can be adjusted, inhibiting the increase in the unsprung mass of the vehicle, and improving vehicle drivability, particularly vertical performance.

Furthermore, by providing the elastic shock-absorbing element of the dynamic shock-absorbing system between the knuckle and the gearbox housing (or a part of the housing), sufficient space is provided for arranging the elastic shock-absorbing element and other components of the wheel-side electric drive system, increasing the flexibility of the layout of the wheel-side electric drive system, thereby avoiding conflicts with parts of the existing suspension system, which makes the installation of the wheel-side electric drive system easier and which does not require a modification of the existing suspension system. For example, the wheel-side electric drive system of the present application is easily used in combination with a conventional multi-link or double wishbone type suspension without causing interference therebetween.

Furthermore, the drive motor of the wheel is disposed as far away from the wheel center axis as possible, so that interference with parts of the existing suspension system can be further avoided.

Although the present application has been described herein with reference to particular embodiments, the scope of the present application is not intended to be limited to the details shown. Various modifications may be made to these details without departing from the underlying principles of the application.

Claims

1. An electric wheel rim drive system comprising:

a motor (1);

a gearbox (2) for transmitting power between the electric machine (1) and the wheel axle shaft (5), the gearbox (2) having at least two gear shifting mechanisms, wherein the electric machine (1) is connected to a first gear shifting mechanism and is fixed to a first housing part of the gearbox (2) carrying the first gear shifting mechanism;

a steering knuckle (15) for steering the wheel; and

an elastic shock-absorbing element (20) which is connected at a first end to the knuckle (15) at a first connection point and at a second end to the first housing part at a second connection point, so that the electric motor (1) and at least the first housing part have a degree of freedom to rotate relative to the knuckle (15) about the wheel axle shaft (5) and the electric motor (1) and at least a part of the mass of the first housing part constitute the dynamic shock-absorbing mass.

2. A wheel-rim electric drive system as claimed in claim 1, wherein the number of elastic shock-absorbing elements (20) is plural, the first and/or second connection points of each elastic shock-absorbing element (20) being located at different radial and/or axial positions.

3. A wheel-rim electric drive system as claimed in claim 2, wherein the first connection point of the at least one elastic shock-absorbing element (20) is located lower than the second connection point thereof, and the first connection point of the at least one elastic shock-absorbing element (20) is located higher than the second connection point thereof.

4. A wheel-rim electric drive system as claimed in claim 2, wherein each elastic shock-absorbing element (20) is positioned such that, when the wheel moves up and down relative to the body, one or some of the elastic shock-absorbing elements (20) is/are extended while the other or some of the elastic shock-absorbing elements (20) is/are shortened.

5. A wheel-side electric drive system as claimed in any one of claims 1 to 4, wherein the intermediate shaft (4) constitutes the output of the first-stage gear change mechanism and the input of the second-stage gear change mechanism, and the motor shaft (3) of the electric motor (1) is arranged on that side of the intermediate shaft (4) which is remote from the half shafts (5), such that the radial distance between the motor shaft (3) and the half shafts (5) is greater than the radial distance between the intermediate shaft (4) and the half shafts (5).

6. A wheel-rim electric drive system as claimed in claim 5, wherein the angle (α) between the line between the centre axis (O1) of the motor shaft (3) and the centre axis (O2) of the intermediate shaft (4) and the line between the centre axis (O2) of the intermediate shaft (4) and the centre axis (O3) of the half-shaft (5) is obtuse or straight, as seen in the axial direction of the wheel.

7. Wheel-side electric drive system according to any one of claims 1 to 4, wherein the gearbox (2) has a single casing structure comprising the first casing part and a second casing part carrying a second-stage gear shift mechanism, the first and second casing parts being integral;

the electric motor (1) and the entire gearbox (2) have a degree of freedom of rotation about the half-shaft (5) relative to the knuckle (15), the electric motor (1) and the entire gearbox (2) being suspended from the knuckle (15) by means of elastic shock-absorbing elements (20).

8. Wheel-rim electric drive system according to any one of claims 1 to 4, wherein the gearbox (2) has a double-housing structure comprising the first housing part (21) and a second housing part (22) carrying a second-stage gear shift mechanism, the second housing part (22) being fixed together with the knuckle (15);

the intermediate shaft (4) forms the output of the first stage transmission and the input of the second stage transmission, the motor (1) and said first housing part (21) having a degree of freedom of rotation about the intermediate shaft (4) relative to the second housing part (22) and the knuckle (15), the motor (1) and said first housing part being suspended from the knuckle (15) by means of elastic shock-absorbing elements (20).

9. A wheel-rim electric drive system as claimed in claim 8, wherein the first housing part (21) and the second housing part (22) are connected to each other by means of a rotary joint (23) formed by their respective tubular portions, the intermediate shaft (4) passing through the rotary joint (23), and a bearing (24) and a seal (25) being provided between the respective tubular portions of the first housing part (21) and the second housing part (22).

10. An electric wheel drive system according to claim 8, wherein an additional elastic shock-absorbing element (26) is provided between the first housing part (21) and the second housing part (22).

11. A wheel-rim electric drive system as claimed in claim 9, wherein an additional elastic shock-absorbing element (26) is provided between the first housing part (21) and the second housing part (22).

12. The wheel-side electric drive system of any one of claims 1 to 4, wherein the first stage transmission mechanism comprises a first gear pair and the second stage transmission mechanism comprises a second gear pair;

and an idle gear (10) used for increasing the radial distance between the motor (1) and the half shaft (5) is arranged in the first gear pair and/or the second gear pair.