CN108274988B - Wheelside Electric Drive System with Dynamic Vibration Absorption - Google Patents

Abstract

A wheelside electric drive system comprises: a motor (1); a gearbox (2) transmitting power between the motor (1) and a wheel half shaft (5), and the gearbox (2) has at least a two-stage transmission mechanism , wherein, the motor (1) is fixed on the first box body part of the gearbox (2) carrying the first-stage speed change mechanism; the steering knuckle (15) for steering the wheels; and the elastic shock-absorbing element (20), Its first end is connected to the knuckle (15) at a first connection point and its second end is connected to the first case part at a second connection point so that the motor (1) and at least part of the mass of the first case part It constitutes a dynamic vibration-absorbing mass.

Description

Wheelside Electric Drive System with Dynamic Vibration Absorption

technical field

The present application relates to a wheel-side electric drive system with dynamic vibration absorption function, which can be easily combined with the vehicle's conventional suspension system.

Background technique

Plug-in electric or hybrid vehicles may include a decentralized electric drive system, enabling individual drive to each wheel. Decentralized electric drive systems include drive in-wheel or wheel-side mounted motors. The advantages of the decentralized electric drive system are short power transmission chain, high transmission efficiency, compact structure and so on. Moreover, each electric drive system can be independently controlled, so that each electric drive system can be quickly adjusted for driving force or braking force, thereby improving vehicle dynamic performance. Additionally, split-controlled drive wheels enable torque vectoring for improved cornering stability.

Large-mass motors are usually installed in the driving wheel or on the side of the wheel, so the unsprung mass is significantly increased, which leads to an unbalanced ratio between the sprung mass and the unsprung mass of the vehicle, and the drivability of the vehicle, especially the vertical performance. An effective way to reduce the effective unsprung mass is to add dynamic vibration absorbers to the wheels. The patent document CN102555770A proposes to use the motor as the mass of the dynamic vibration absorber, wherein a two-stage gearbox is used, and a spring-damper of the dynamic vibration absorber is arranged between the two.

Applications in various types of suspensions are not addressed in the above documents. When a wheel mount type drive system having such a dynamic vibration absorber is mounted on an existing conventional suspension, much interference occurs between the wheel mount type drive system and the multi-link type suspension. For example, since the central axis of the motor is radially close to the central axis of the wheel, interference may occur between the steering knuckle and the trailing arm, between the motor and the damper, and between the motor and the lower control arm.

Contents of the invention

The present application aims at avoiding the interference when installing the wheel drive system to the existing conventional vehicle suspension, and at the same time effectively restraining the increase of the unsprung mass of the vehicle.

To this end, according to one aspect of the present application, there is provided a wheel-side electric drive system with a dynamic vibration-absorbing function, which includes: a motor; a two-stage transmission mechanism, wherein the motor is connected to the first-stage transmission mechanism and is fixed on the first case part of the gearbox carrying the first-stage transmission mechanism; a steering knuckle for steering the wheels; and an elastic shock-absorbing element, Its first end is connected to the steering knuckle at a first connection point, and its second end is connected to the first housing part at a second connection point, so that the motor and at least part of the mass of the first housing part constitute a dynamic vibration-absorbing mass.

According to a feasible implementation manner, there are multiple elastic vibration-absorbing elements, and the first connection point and/or the second connection point of each elastic vibration-absorbing element are located at different radial and/or axial positions.

According to a feasible implementation manner, the position of the first connection point of at least one elastic shock-absorbing element is lower than its second connection point, and the position of the first connection point of at least one elastic shock-absorbing element is higher than its second connection point.

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

According to a possible implementation, the intermediate shaft constitutes the output end of the first-stage transmission mechanism and the input end of the second-stage transmission mechanism, and the motor shaft of the motor is arranged on the side of the intermediate shaft away from the half-shaft, so that the motor shaft and the half-shaft The radial distance between the shafts is greater than the radial distance between the intermediate shaft and the semi-shafts.

According to a feasible implementation manner, viewed along the axial direction of the wheel, 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 obtuse or straight angles.

According to a feasible implementation manner, the gearbox has a single case structure, including the first case part and the second case part carrying the second-stage transmission mechanism, and the first and second case parts are integrated ; The motor and the entire gearbox have a degree of freedom to rotate around the half shaft relative to the steering knuckle, and the motor and the entire gearbox are suspended from the steering knuckle through elastic shock-absorbing elements.

According to a feasible implementation manner, the gearbox has a double-case structure, including the first case part and the second case part carrying the second-stage transmission mechanism, and the second case part is fixed together with the steering knuckle The intermediate shaft constitutes the output end of the first-stage transmission mechanism and the input end of the second-stage transmission mechanism, and the motor and the first case part have a degree of freedom to rotate around the intermediate shaft relative to the second case part and the steering knuckle , the motor and the first box part are suspended from the steering knuckle through an elastic shock-absorbing element.

According to a possible implementation manner, the first box part and the second box part are connected through a rotary joint formed by their respective tubular parts, the intermediate shaft passes through the rotary joint, and the first box part Bearings and seals are provided between the corresponding tubular portion and the second housing portion.

According to a feasible implementation manner, an additional elastic shock-absorbing element is provided between the first box part and the second box part.

According to a feasible implementation manner, the first-stage transmission mechanism includes a first gear pair, and the second-stage transmission mechanism includes a second gear pair; the first gear pair and/or the second gear pair are provided for increasing The idler gear for the radial distance between the motor and the half shaft.

According to the present application, the elastic shock-absorbing element is arranged between the steering knuckle and the gearbox case, which provides sufficient space 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 flexibility, so that the wheel-side electric drive system can be arranged in a position that does not interfere with the conventional suspension system. In addition, the entire gearbox or a part of the gearbox and the motor have a degree of freedom to rotate within a limited range, thereby constituting a dynamic shock absorber structure, which effectively suppresses the increase in the unsprung mass of the vehicle and improves the dynamic performance of the vehicle.

Description of 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 diagram of a wheel-side electric drive system according to a possible implementation manner of the present application;

Fig. 2 is a schematic layout diagram of the wheel electric drive system in Fig. 1 along the axial direction;

Fig. 3 is a schematic layout diagram of a wheel-side electric drive system according to another feasible implementation manner of the present application;

Fig. 4 is a schematic layout diagram along the axial direction of the wheel side electric drive system in Fig. 3 .

detailed description

A feasible implementation of the wheel-side electric drive system with dynamic vibration absorption function of the present application will be described below with reference to the accompanying drawings. It should be pointed out that the drawings provided here are only exemplary, and do not constitute any limitation to the scope of the application. In order to highlight certain features, the various parts in the drawings are not drawn to scale, and some structures are schematically shown with dotted lines, and some structures are omitted and not shown.

FIG. 1 schematically shows a wheel-side electric drive system with a dynamic vibration absorption function according to a possible embodiment of the present application. Each drive wheel of the vehicle is equipped with a wheelside electric drive system, in which the output rotational motion and torque of the motor 1 arranged on the side of the wheel close to the drive wheel is transmitted to the wheel through the gearbox 2, thereby driving the wheel rotate. The wheels and their wheel-side electric drives are mounted on the suspension system.

The gearbox 2 is a single-casing gearbox, that is, the gearbox casing has an integrated structure, and there are two-stage speed change (usually all deceleration) mechanisms in it. The motor 1 is fixed on the gearbox casing.

The gearbox housing carries the motor shaft 3, the intermediate shaft 4 and the half shaft 5 of the wheel. The motor shaft 3 defines the central axis of the motor 1 and extends from the motor 1 into the gearbox case for inputting the rotational motion and torque of the motor 1 into the gearbox 2 . The half shaft 5 defines the central axis of the wheel and projects from the gearbox housing. The intermediate shaft 4 is located in the gearbox housing.

The first driving gear 6 is supported on the motor shaft 3 , the first driven gear 7 and the second driving gear 8 are supported on the intermediate shaft 4 , and the second driven gear 9 is supported on the half shaft 5 .

The first driving gear 6 meshes with the first driven gear 7 to form a first-stage transmission mechanism of the gearbox 2 . The second driving gear 8 meshes with the second driven gear 9 to constitute the second-stage transmission mechanism of the gearbox 2 . These gears are located in the transmission case. The first case part of the gearbox case carrying the first-stage transmission mechanism is integrated with the second case part carrying the second-stage transmission mechanism.

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

Relative to the intermediate shaft 4 , the motor shaft 3 is arranged on a side away from the half shaft 5 , so that the radial distance between the motor shaft 3 and the half shaft 5 is greater than the radial distance between the intermediate shaft 4 and the half shaft 5 . As shown in Figure 2, viewed in the axial direction of the wheel, the line between the central axis O1 of the motor shaft 3 and the central axis O2 of the intermediate shaft 4 and the central axis O2 of the intermediate shaft 4 and the central axis O3 of the half shaft 5 The angle α between the connecting lines is an obtuse angle or a flat angle, that is, 90°<α≤180°. This point can be described as an obtuse or flat angle distribution between the two-stage reduction mechanisms. In this way, the radial distance between the motor 1 and the center axis of the wheel can be increased, that is, the motor 1 is arranged radially away from the center axis of the wheel, so as to avoid the motor 1 and the gearbox 2 connected to it from the center axis of the wheel. and suspension system structures (not shown) in the vicinity interfere.

In order to have a sufficient radial distance between the motor 1 and the center axis of the wheel, an idler gear 10 can be provided between the second driving gear 8 and the second driven gear 9 , as shown in the figure. Of course, as an alternative or additional measure, an idler gear can also be provided between the first drive gear 6 and the first driven gear 7 .

The axle shaft 5 is connected to the hub 11 , and the hub 11 supports the rim 12 , for example, the rim 12 is fixed to the hub 11 by bolts 13 . The hub 11 rotates together with the half shaft 5 . In addition, a brake disc 14 is also supported on the hub 11 .

The half shaft 5 rotatably passes through the steering knuckle 15 of the wheel, which is used to steer the wheel. The steering knuckle 15 is sleeved on the shaft sleeve 17 fixed with the half shaft 5 through the bearing 16 . Brake elements 18 , such as brake calipers, are supported on the steering knuckle 15 . The brake element 18 can be fastened to the steering knuckle 15 by means of bolts 19 .

In addition, an elastic vibration-absorbing element 20 is provided between the gearbox 2 and the steering knuckle 15 . In the example shown, the elastic shock-absorbing element 20 is linear and mainly includes springs and dampers; of course, other various forms of elastic shock-absorbing elements used in the art may be used here.

The first end of the elastic shock absorbing element 20 is connected to the steering knuckle 15 , and the second end is connected to the gearbox 2 . In this way, the electric motor 1 and the gearbox 2 are elastically suspended together on the steering knuckle 15, so that part of the mass of the electric motor 1 and the gearbox 2 acts as a vibration-absorbing mass. Thus, the motor 1 , the gearbox 2 and the elastic vibration-absorbing element 20 constitute a dynamic vibration-absorbing system. The motor 1 and the gearbox 2 have a degree of freedom to rotate back and forth slightly around the center axis of the wheel (ie the center axis of the half shaft 5 ).

When the vehicle is running, the wheels are impacted by the uneven road surface and vibrate up and down. During this process, the motor 1 and the gearbox 2 rotate slightly and repeatedly around the central axis of the wheel, so that the elastic vibration-absorbing element 20 absorbs vibration energy. In this way, the dynamic performance of the vehicle can be improved, including ABS, TCS, ESP and torque vector control and so on. In addition, part of the mass of the motor 1 and the gearbox 2 becomes the sprung mass, which helps to adjust the ratio between the sprung mass and the unsprung mass of the vehicle, and suppresses the increase of the unsprung mass of the vehicle, thereby further improving the drivability of the vehicle, Especially vertical performance.

By arranging the elastic shock-absorbing element 20 between the steering knuckle and the case of the gearbox 2, sufficient space is provided to arrange the elastic shock-absorbing element 20 and other components of the wheel-side electric drive system, thereby easily avoiding the existing suspension system Each part makes the wheel 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 motor 1, that is, the gearbox 2 is located on the axial inner side of the wheel, and the motor 1 is located on the axial inner side of the gearbox 2, as shown in FIG. 1 . In the gearbox 2 , the first transmission mechanism associated with the electric motor 1 is located axially inside the second transmission mechanism associated with the half shaft 5 . Like this, motor 1 and gearbox 2 occupy less space near the center axis of the wheel as far as possible, to further avoid motor 1 and the first-stage transmission mechanism connected with it from interfering with the center axis of the wheel and the suspension system structure in the vicinity (not shown) interfere with each other.

It can be understood that the dynamic shock absorbing system may include more than one elastic shock absorbing element 20, the first end of each elastic shock absorbing element 20 may be connected to the steering knuckle 15 at the same connection point A, and the second end of each elastic shock absorbing element 20 is at Different connection points B1, B2... are connected to the gearbox case (as shown in Figure 2). Alternatively, the first ends of each elastic shock-absorbing element 20 may be connected to the steering knuckle 15 at different connection points, while the second ends of each elastic shock-absorbing element 20 are connected to the gearbox case at the same connection point. Alternatively, the first ends of each elastic shock-absorbing element 20 can be connected to the steering knuckle 15 at different connection points, and the second ends of each elastic shock-absorbing element 20 are also connected to the gearbox case at different connection points. The connection positions of the two ends of each elastic shock-absorbing element 20 are designed so that when the wheel moves up and down relative to the vehicle body, each elastic shock-absorbing element 20 functions in coordination with each other. The different connection points mentioned here refer to their different radial and/or axial positions.

For example, according to a feasible implementation manner, the heights of the connection points of the elastic shock-absorbing elements 20 on the gearbox case are smaller than their connection points A on the steering knuckle 15 or components fixed relative to the steering knuckle 15 .

As another example, according to another possible implementation, the height of the connection point B1 of one (or some) elastic shock-absorbing elements 20 on the gearbox case is greater than its connection on the steering knuckle 15 or a component fixed relative to the steering knuckle 15 At point A, the height of the connection point B2 of another (or some) elastic shock-absorbing elements 20 on the gearbox case is smaller than its connection point A on the steering knuckle 15 or the parts fixed relative to the steering knuckle 15, so that when the wheels are opposite When the vehicle body moves up and down, one (or some) elastic shock-absorbing elements 20 are extended, and the other (or some) elastic shock-absorbing elements 20 are shortened.

The number and connection positions of other feasible elastic shock-absorbing elements 20 can also be designed according to specific structures and needs.

FIG. 3 schematically shows an electric wheel drive system with a dynamic vibration absorption function according to another possible embodiment of the present application. The function of this wheel-side electric drive system is similar to that shown in Fig. 1 . The output rotational motion and torque of the motor 1 arranged on the side of the wheel near the driven wheel are transmitted to the wheel through the gearbox 2, thereby driving the wheel to rotate.

The gearbox 2 is a double-casing gearbox, that is, the gearbox casing includes two casing parts, that is, the first casing part 21 and the second casing part 22, which are used to carry two-stage speed change (usually all for speed reduction). )mechanism.

The motor 1 is fixed on the first case part 21 . The first box part 21 and the second box part 22 are connected by a rotary joint 23 formed by their respective tubular parts, so that the first box part 21 can rotate around the rotary joint 23 relative to the second box part 22 . The swivel joint 23 is formed by respective tubular portions of the first case portion 21 and the second case portion 22 and includes a bearing 24 and a seal between the respective tubular portions of the first case portion 21 and the second case portion 22. piece 25. The second housing part 22 is fastened to the steering knuckle 15 , for example by means of bolts 27 .

Between the first box part 21 and the steering knuckle 15, an elastic shock-absorbing element 20 is arranged. In the example shown, the elastic shock-absorbing element 20 is linear and mainly includes springs and dampers; of course, other various forms of elastic shock-absorbing elements used in the art may be used here. The first end of the elastic shock-absorbing element 20 is connected to the steering knuckle 15 , and the second end is connected to the first box part 21 .

By arranging the elastic shock absorbing element 20 between the steering knuckle and the first box part 21, sufficient space is provided to arrange the elastic shock absorbing element 20 and other components of the wheel-side electric drive system, thereby easily avoiding the existing suspension system It is easy to integrate with the existing suspension system.

As an optional feature, an additional elastic shock absorbing element 26 may be arranged between the first box part 21 and the second box part 22 . A first end of the elastic shock absorbing element 26 is connected to the second box part 22 , and a second end is connected to the first box part 21 . The elastic shock-absorbing element 26 can be linear or twisted, and the number of elastic shock-absorbing elements 26 can 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 the rotary joint 23 . The intermediate shaft 4 has the same central axis as the rotary joint 23 .

The first driving gear 6 is supported on the motor shaft 3 , the first driven gear 7 and the second driving gear 8 are supported on the intermediate shaft 4 , and the second driven gear 9 is supported on the half shaft 5 .

The first driving gear 6 located in the first case part 21 meshes with the first driven gear 7 to constitute the first stage transmission mechanism of the gearbox 2 . The second driving gear 8 located in the second case part 22 meshes with the second driven gear 9 to constitute the second-stage transmission mechanism of the gearbox 2 .

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

Relative to the intermediate shaft 4 , the motor shaft 3 is arranged on a side away from the half shaft 5 , so that the radial distance between the motor shaft 3 and the half shaft 5 is greater than the radial distance between the intermediate shaft 4 and the half shaft 5 . As shown in Figure 4, viewed in the axial direction of the wheel, the line between the central axis O1 of the motor shaft 3 and the central axis O2 of the intermediate shaft 4 and the central axis O2 of the intermediate shaft 4 and the central axis O3 of the half shaft 5 The angle α between the connecting lines is an obtuse angle or even a flat angle, thereby increasing the radial distance between the motor 1 and the center axis of the wheel defined by the half shaft 5, that is, the motor 1 is arranged radially away from the center axis of the wheel to avoid motor 1 And the first-stage transmission mechanism connected thereto interferes with the central axis of the wheel and the suspension structure (not shown) in the vicinity.

In order to have a sufficient radial distance between the motor 1 and the center axis of the wheel, an idler gear 10 can be provided between the second driving gear 8 and the second driven gear 9 , as shown in the figure. Of course, as an alternative or additional measure, an idler gear can also be provided between the first drive gear 6 and the first driven gear 7 .

The axle shaft 5 is connected to the hub 11 , and the hub 11 supports the rim 12 , for example, the rim 12 is fixed to the hub 11 by bolts 13 . The hub 11 rotates together with the half shaft 5 . In addition, a brake disc 14 is also supported on the hub 11 .

The half shaft 5 rotatably passes through the steering knuckle 15 . The steering knuckle 15 is sleeved on the shaft sleeve 17 fixed with the half shaft 5 through the bearing 16 . Brake elements 18 , such as brake calipers, are supported on the steering knuckle 15 . The brake element 18 can be fastened to the steering knuckle 15 by means of bolts 19 .

The motor 1 together with the first housing part 21 is elastically suspended on the steering knuckle 15 via the elastic vibration-absorbing element 20, so that part of the mass of the motor 1 and the first housing part 21 acts as a vibration-absorbing mass. Thus, the motor 1 , the first box part 21 and the elastic vibration-absorbing element 20 (and possibly the elastic vibration-absorbing element 26 ) constitute a dynamic vibration-absorbing system. The motor 1 and the first case part 21 have a degree of freedom to rotate back and forth slightly around the central axis of the intermediate shaft 4 . Adding an additional elastic vibration-absorbing element 26 can increase the flexibility of the design of the dynamic vibration-absorbing system.

Likewise, it can be understood that the dynamic vibration-absorbing system may include more than one elastic vibration-absorbing element 20 , and they may be arranged as in the previous embodiments in FIGS. 1 and 2 .

When the vehicle is running, the wheels are impacted by the uneven road surface and vibrate up and down. During this process, the motor 1 and the first case part 21 rotate repeatedly around the central axis of the intermediate shaft 4 in small amplitudes, so that the elastic vibration-absorbing element 20 (and possibly the elastic vibration-absorbing element 26 ) absorbs vibration energy. In this way, the dynamic performance of the vehicle can be improved. In addition, part of the mass of the motor 1 and the first case part 21 and the first-stage transmission mechanism becomes the sprung mass, which helps to adjust the ratio between the sprung mass and the unsprung mass of the vehicle, and suppresses the unsprung mass of the vehicle. increase, thereby further improving vehicle drivability, especially vertical performance.

In the axial direction of the wheel, the gearbox 2 is located between the wheel and the motor 1, that is, the gearbox 2 is located on the axial inner side of the wheel, and the motor 1 is located on the axial inner side of the gearbox 2, as shown in FIG. 3 . In the gearbox 2 , the first case portion 21 fixed with the motor 1 is located axially inside the second case portion 22 fixed with the half shaft 5 . In this way, the motor 1 and the first case part 21 occupy as little space as possible near the central axis of the wheel, to further avoid the motor 1 and the first case part 21 connected thereto with the central axis of the wheel and the suspension in the vicinity. structures (not shown) interfere.

Other aspects of the embodiment shown in Figs. 3 and 4 are similar or identical to those shown in Figs. 1 and 2, and will not be described again.

Although the gearbox 2 in the example described above is a two-stage gearbox, according to specific needs, the gearbox 2 can also be a three-stage or more-stage gearbox.

It can be seen that, according to the present application, the drive motor and the gearbox (or part of the gearbox) of the wheel are given freedom to rotate within a limited range, so that a part of their mass constitutes the mass of the dynamic vibration absorbing system of the wheel, Therefore, the elastic vibration-absorbing element is used to absorb the vibration energy generated by the wheel being acted on by the ground, so that the dynamic performance of the vehicle can be improved. In addition, since part of the mass of the motor and gearbox (or a part of the gearbox) becomes the sprung mass, the ratio between the sprung mass and the unsprung mass of the vehicle can be adjusted, suppressing the increase in the unsprung mass of the vehicle, thereby improving Vehicle drivability, especially vertical performance.

In addition, by arranging the elastic shock-absorbing elements of the dynamic shock-absorbing system between the steering knuckle and the gearbox case (or a part of the case), sufficient space is provided to arrange the elastic shock-absorbing elements and other components of the wheel-side electric drive system, Increases the flexibility of the layout of the electric drive system around the wheel, thereby avoiding conflicts with various parts of the existing suspension system, which makes the installation of the electric drive system around the wheel easier and does not require any modifications to the existing suspension system remodel. For example, the wheel-side electric drive system of the present application is easily used in combination with conventional multi-link or double-wishbone suspensions without causing mutual interference with each other.

In addition, the drive motors of the wheels are arranged as far away from the center axis of the wheels as possible, so that conflicts with various parts of the existing suspension system can be further avoided.

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

Claims (12)

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.

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