ELECTRIC DRIVE RIGID REAR AXLE ASSEMBLY WITH STABILITY CONTROL

Abstract

A vehicle includes a body structure and a rear axle connecting two rear wheels and carried by two leaf spring units, each leaf spring unit being pivotably connected at one end to the body and at another end to a connection arm pivotably connected to the body structure, wherein the rear axle includes two driveshafts connecting the rear wheels. A drive unit is supported by the rear axle to be self-supporting relative to the body. The drive unit includes an electric motor coupled to at least one of the two drive shafts. A controller is configured to control the electric motor in response to lateral acceleration of the vehicle during cornering to deliver increased driving torque to an outer one of the two rear wheels relative to an inner one of the two rear wheels.

Claims

1. A vehicle comprising: a body structure; a rear axle connecting two rear wheels and carried by two leaf spring units, each leaf spring unit being pivotably connected at one end to the body and at another end to a connection arm pivotably connected to the body, wherein the rear axle includes two driveshafts connecting the rear wheels; and a drive unit supported by the rear axle to be self-supporting relative to the body, the drive unit including an electric motor coupled to at least one of the two drive shafts; and a controller configured to control the electric motor in response to lateral acceleration of the vehicle during cornering to deliver increased driving torque to an outer one of the two rear wheels relative to an inner one of the two rear wheels.

2. The vehicle of claim 1 further comprising a drum or disc brake associated with each of the two rear wheels, wherein the controller is further configured to control the drum or disc brake for the outer rear wheel to apply a braking torque during the cornering.

3. The vehicle of claim 1 wherein the electric motor is coupled to the outer one of the two rear wheels, the vehicle further comprising a second electric motor in communication with the controller and coupled to the inner one of the two rear wheels.

4. The vehicle of claim 3 wherein the controller is further configured to control the second electric motor to apply a regenerative braking torque to the inner wheel during the cornering.

5. The vehicle of claim 1 wherein the controller is further configured to calculate the lateral acceleration based on a steering angle and speed of the vehicle during the cornering.

6. The vehicle of claim 1 wherein the drive unit comprises a differential configured to couple the two drive shafts to the electric motor.

7. The vehicle of claim 1 wherein the controller is further configured to apply the increased driving torque to the outer one of the two rear wheels by applying a braking torque to the inner one of the two rear wheels.

8. The vehicle of claim 7 wherein the controller is configured to control the electric motor to apply the braking torque.

9. The vehicle of claim 7 wherein the vehicle comprises a disc or drum brake associated with each of the two rear wheels, wherein the controller is configured to control the disc or drum brake to apply the braking torque.

10. A vehicle having a rear axle connecting rear wheels, and a drive unit having an electric motor coupled to the rear wheels with the rear axle and drive unit carried by leaf spring units, comprising: a controller configured to control the electric motor responsive to lateral acceleration of the vehicle during cornering to deliver increased driving torque to an outer one of the rear wheels relative to an inner one of the rear wheels.

11. The vehicle of claim 10 further comprising a disc or drum brake associated with each of the rear wheels and in communication with the controller, wherein the controller is further configured to control the disc or drum brake of the inner one of the rear wheels during the cornering so that the driving torque of the outer one of the rear wheels exceeds the driving torque of the inner one of the rear wheels.

12. The vehicle of claim 10 wherein the electric motor is coupled to a first one of the rear wheels, the vehicle further comprising a second electric motor in communication with the controller and coupled to a second one of the rear wheels.

13. The vehicle of claim 12 wherein the controller is further configured to control one of the electric motor and the second electric motor to provide regenerative braking torque to the inner one of the rear wheels.

14. The vehicle of claim 12 wherein the controller is further configured to control one of the electric motor and the second electric motor to provide regenerative braking torque to the inner one of the rear wheels, and the other of the electric motor and the second electric motor to provide increased driving torque to the outer one of the rear wheels.

15. A vehicle comprising: a rear axle coupled by leaf spring units to a vehicle structure; a drive unit supported by the rear axle comprising first and second electric motors coupled to respective ones of two rear wheels; and a controller configured to control the electric motors responsive to lateral acceleration of the vehicle to provide more driving torque to a selected one of the two rear wheels than another of the two rear wheels.

16. The vehicle of claim 15 wherein the controller is configured to control one of the motors to provide braking torque to the another of the two rear wheels during cornering.

17. The vehicle of claim 15 wherein the controller calculates lateral acceleration based on a steering angle and speed of the vehicle.

18. The vehicle of claim 15 further comprising a drum or disc brake associated with each of the two rear wheels, wherein the controller is further configured to control the drum or disc brake to provide a braking torque responsive to the lateral acceleration.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0026] FIG. 1 is a schematic side view of a vehicle having an axle assembly according to one or more embodiments;

[0027] FIG. 2 is a schematic view from below of the vehicle of FIG. 1; and

[0028] FIG. 3 is a schematic view from below of a vehicle having an alternative embodiment of an axle assembly.

DETAILED DESCRIPTION

[0029] As required, detailed embodiments are disclosed herein; however, it is to be understood that the disclosed embodiments are merely representative and may be embodied in various and alternative forms. The figures are not necessarily to scale; some features may be exaggerated or minimized to show details of particular components. Therefore, specific structural and functional details disclosed herein are not to be interpreted as limiting, but merely as a representative basis for teaching one skilled in the art to variously employ the claimed subject matter.

[0030] In the different figures, the same parts are denoted by the same reference signs and are therefore generally only described once.

[0031] FIGS. 1 and 2 show various views of a motor vehicle 50, for example a truck or a van, having an axle assembly 1 according to at least one embodiment. The illustration here is highly schematic and simplified. A rear axle 2, which is designed as a rigid axle and extends parallel to the Y axis, is fastened to two leaf springs 3, 4, which extend substantially in the direction of the X axis and via which the vehicle axle 2 is fastened to a vehicle structure 40, for example a vehicle frame, in a sprung manner. The leaf springs 3, 4, which are designed as semi-elliptical springs in the present example, can be manufactured in particular from spring steel or possibly fiber-reinforced plastics material. The leaf springs 3, 4 form leaf spring units here, which could alternatively be designed as packs of a plurality of leaf springs.

[0032] A first wheel 7 and a second wheel 8 are arranged at the ends of the rear axle 2. A wheel brake 9, 10, which can be designed in any manner, for example as a drum brake or disk brake, is associated with each wheel here.

[0033] Each leaf spring 3, 4 is pivotably connected at a front end 3.1, 4.1 to the vehicle structure 40. The respective leaf spring 3, 4 is pivotably connected at a rear end 3.2, 4.2 to a connecting arm 5, 6, which is in turn pivotably connected to the vehicle structure 40. The structure shown here therefore corresponds to a Hotchkiss suspension. All in all, the connecting arms 5, 6 enable a movement of the rear end 3.2, 4.2 within the X-Z plane; more precisely, a rotation about the pivot axis of the connecting arm 5, 6 relative to the vehicle structure 40, whereby the deformation of the leaf springs 3, 4 during the deflection can be compensated.

[0034] The axle assembly 1 moreover has a drive unit 11, via which the two wheels 7, 8 can be driven differently. That is to say that each of the wheels can be acted upon by a different torque. The distribution of the torques to the two wheels 7, 8 here is controlled by a control unit 12, which is connected to the drive unit 11. The control unit 12 can be arranged near to the drive unit 11 here, as illustrated schematically in FIG. 1, or in a further remote part of the vehicle 50. In the illustrated example, the drive unit 11 has an electrically operated drive motor 13, a differential gear (not illustrated) and a torque distribution motor 14, which controls the actual distribution of the torques via the differential gear.

[0035] FIG. 2 shows the vehicle during cornering, during which two front wheels 31, 32 are set at a steering angle . The vehicle 50 is traveling at a speed v, which leads to a lateral acceleration a. This lateral acceleration a in turn leads to a higher load on the wheel 8 on the outside of the curve relative to the wheel 7 on the inside of the curve. With a conventional Hotchkiss suspension, this results in a stronger deflection of the wheel 8 on the outside of the curve, which in turn leads to a stronger rearward excursion of the wheel 8 on the outside of the curve in relation to the wheel 7 on the inside of the curve. Therefore, a rotation of the rear axle 2 about the Z axis is produced, which would lead to oversteer.

[0036] This is at least partly prevented by the intervention of the control unit 12. The control unit 12 receives the steering angle and the speed v and, from this, determines the lateral acceleration a. It goes without saying that alternative methods of determining the lateral acceleration a are also conceivable. Depending on the lateral acceleration a, the control unit 12 determines two torques Mi, M.sub.2 for the two wheels 7, 8. As indicated in FIG. 2, the wheel 4 on the outside of the curve here is acted upon by a higher driving torque M.sub.2 than the wheel 7 on the inside of the curve. This in turn leads to a forwardly-directed force F.sub.2 being produced between the wheel 8 on the outside of the curve and the road, which force is greater than a force F.sub.1 effective between the wheel 7 on the inside of the curve and the road. All in all, therefore, the wheel 8 on the outside of the curve is pulled forward at least in relation to the wheel 7 on the inside of the curve, which at least restricts the oversteer and ideally brings about understeer.

[0037] The effect can be reinforced in that a braking torque M.sub.1, which leads to a rearwardly-directed force F.sub.1, is generated on sides of the wheel 7 on the inside of the curve. This can be generated exclusively by the drive unit 11, for example. Alternatively or additionally, the control unit 12 can also control the wheel brake 9 associated with the wheel 7 on the inside of the curve for this purpose.

[0038] FIG. 3 shows, in a view from below, an alternative embodiment of an axle assembly 1 which, for the most part, is identical to the embodiment illustrated in FIG. 2. However, in this case, the drive unit 11 has two separate drive motors 15, 16, each of which is associated with one of the wheels 7, 8. By controlling the drive motors 15, 16 accordingly, it is also possible in this case for the wheel 8 on the outside of the curve to be acted upon by a driving torque M.sub.2 which is greater than a driving torque M.sub.1 or braking torque M.sub.1 effective on the wheel 7 on the inside of the curve. It goes without saying that the braking torque M.sub.1 here can also be fully or partly generated by the control of the wheel brake 9.

[0039] While representative embodiments are described above, it is not intended that these embodiments describe all possible forms of the claimed subject matter. The words used in the specification are words of description rather than limitation, and it is understood that various changes may be made without departing from the spirit and scope of the disclosure. Additionally, the features of various implementing embodiments may be combined to form further embodiments that are not specifically described or illustrated.