CN112537365A

CN112537365A - Steering wheel unit for detecting a steering movement of a steering wheel of an electromechanical steering system

Info

Publication number: CN112537365A
Application number: CN201910893811.1A
Authority: CN
Inventors: M-C·科斯塔凯; M-N·韦莱亚; A·胡苏; M·阿基姆; M·科瓦奇
Original assignee: Schaeffler Technologies AG and Co KG
Current assignee: Schaeffler Technologies AG and Co KG
Priority date: 2019-09-20
Filing date: 2019-09-20
Publication date: 2021-03-23

Abstract

A steering wheel unit for an electromechanical steering system of a motor vehicle has a steering wheel shaft, a housing and a force generating device for applying a mechanical feedback force to the steering wheel in order to feed back the current steering and/or driving state to the driver. The force generating device is disposed inside the housing. The force generating device has an inner connecting element, an elastic coupling element which surrounds the inner connecting element at least partially coaxially and is connected thereto in a force-fitting manner, and an elastic housing coupling element which surrounds the elastic coupling element at least partially coaxially and is connected thereto in a form-fitting manner. The inner connecting element is connected at the end side to the steering wheel shaft. The force generating device exerts a force on the steering wheel shaft such that a feedback force that can be generated on the steering wheel for feeding back to the driver a steering state that is related to the steering angle of the wheels increases as the adjustment of the steering wheel out of straight travel increases.

Description

Steering wheel unit for detecting a steering movement of a steering wheel of an electromechanical steering system

Technical Field

The invention relates to a steering wheel unit for sensorially detecting a steering movement of a steering wheel of an electromechanical steering system of a motor vehicle. The invention further relates to an electromechanical steering system comprising such a steering wheel unit.

Background

The field of application of the invention extends to so-called steer-by-wire systems for motor vehicles, in which no direct mechanical coupling exists between the steering wheel and the steered wheels of the motor vehicle. Instead, the steering angle of the steering wheel and, if necessary, also the rotational speed of the steering wheel and/or the torque applied to the steering wheel are detected by suitable sensor devices and transmitted in the form of electrical control values to an electromechanical steering wheel actuator unit, which converts an electrically predefined steering signal into a mechanical adjustment of the steering angle of the wheels of the steerable axle.

In such electromechanical steering systems, direct mechanical feedback about the actually implemented steering angle of the wheels is therefore eliminated, which in mechanically coupled systems can be felt by the driver, usually in the form of a return torque on the steering wheel, which is dependent on the driving speed, and vibrations superimposed thereon, as well as via the end stop position of the steering wheel.

From US 2017/0320515 a1, an electromechanical steering system for a motor vehicle is known, which is equipped with a special force generating device on the steering wheel unit for applying a mechanical feedback force to the steering wheel in order to inform the driver of the current steering and vehicle state. For this purpose, the steering wheel unit has an electric motor for generating a feedback force by applying a corresponding torque to the steering wheel shaft. By suitable actuation of the electric motor, the actual driving sensation can be transmitted to the driver via the steering wheel, as in a mechanically coupled steering system. The force generating device provided for this purpose furthermore comprises a lockable coupling which is actuated by the electromagnetic actuator and serves to prevent further rotation of the steering wheel shaft when the wheel reaches a predetermined end stop position in the respective direction of rotation. For this purpose, the coupling fixes the steering wheel shaft in accordance with the electronic control device in the above-described situation. In this prior art, the electric motor for applying the mechanical feedback force is an active member, which therefore also requires electronic control means.

Another electromechanical steering system for a motor vehicle is known from US 2002/0189888 a1, which is also equipped with an electric motor for generating a mechanical feedback force on the steering wheel. For this purpose, the electric motor is arranged in an axially parallel manner to the steering wheel shaft and acts on the steering wheel via a belt drive. This solution requires more installation space in the transverse direction with respect to the steering wheel axis than the prior art mentioned above.

Disclosure of Invention

The object of the present invention is therefore to provide a steering wheel for an electromechanical steering system of a motor vehicle, which saves installation space and/or energy and enables mechanical feedback forces to be transmitted to the driver with regard to the current steering state in a simple technical manner.

The object is achieved with a steering wheel unit according to the preamble of the preferred embodiment in combination with the characterizing features thereof. In the case of an electromechanical steering system comprising such a steering wheel unit, reference is made to a preferred embodiment of the electromechanical steering system.

The present invention includes the teaching of providing a steering wheel unit for an electromechanical steering system of a motor vehicle. The steering wheel unit has a force generating device for applying a mechanical feedback force to the steering wheel in order to feedback the current steering and/or driving state to the driver. The force generating device is arranged inside the housing and has an internal connecting element, an elastic coupling element and an elastic housing coupling element. The elastic coupling element at least partially coaxially surrounds the inner connecting element and is connected to the inner connecting element in a force-fitting manner. The elastic housing coupling element at least partially coaxially surrounds the elastic coupling element and is connected to the elastic coupling element in a form-fitting manner. The inner connecting element is connected at the end to the steering wheel shaft or is connected to the steering wheel shaft by means of a flange. The force generating device exerts a force on the steering wheel shaft such that a feedback force that can be generated on the steering wheel for feeding back to the driver a steering state that is related to the steering angle of the wheels increases as the adjustment of the steering wheel out of straight travel increases. In other words, a feedback force is exerted on the steering wheel shaft by means of the elastic deformation of the elastic coupling element and the elastic housing coupling element. The elastic housing coupling element can be connected either directly to the housing or can be selectively braked by an electromechanical brake.

The advantage of the solution according to the invention is in particular that it is achieved using passive components which do not need to be controlled by an electronic control unit. The current requirement of the electromechanical steering system can thereby be reduced. Furthermore, the passive components, in particular the force generating device, can be arranged in a space-saving manner. Furthermore, the weight of the steering wheel unit can be kept small by the proposed solution.

The solution of the invention ensures that a rotation of the steering wheel in one direction or the other causes the elastic housing coupling element and/or the elastic coupling element to deform elastically, thereby establishing mechanical potential energy for generating a mechanical feedback force. In other words, the steering wheel shaft-side end of the elastic housing coupling element rotates and the opposite end of the elastic housing coupling element is fixed. As a result, the elastic housing coupling element is twisted and elastically deformed. This elastic deformation causes the generation of a feedback force. The feedback force increases accordingly as the twist or steering angle increases. It should be noted that the elastic housing coupling element and the degree of elasticity of the elastic coupling element can be adapted to the respective application, so that a feedback force corresponding to a purely mechanical steering system can be generated. For example, the degree of elasticity of the elastic housing coupling element and the elastic coupling element may be the same or different. For transmitting forces or generating feedback forces, the elastic housing coupling element and the elastic coupling element can be connected to one another in a form-fitting manner. Furthermore, various cross-sections can be provided for the connection. It is advantageous here if the surface of the contact surface between the two spring elements is maximized, for example, by a star-shaped cross section. The star-shaped cross-section may have three, four, five or more points, which may depend on the respective application.

According to one embodiment, the steering wheel unit further comprises an electromagnetic brake. The electromagnetic brake is fixedly connected to the housing and is provided for applying a braking force to the elastic housing coupling element. The feedback force generated by the force generating device can thus be supported on the housing of the steering wheel unit and, in addition, the corresponding feedback force can be adjusted according to the current desire, for example, the slip between the electromagnetic brake and the elastic housing coupling element can be adjusted.

The electromagnetic brake may have a spring, a pressure plate, a friction disc, and an electromagnet. The friction disc may be arranged between the pressure plate and the resilient housing coupling element, wherein the spring may apply a force to the pressure plate and thereby press the pressure plate against the friction disc and the pressure plate against the resilient housing coupling element, thereby applying a braking force to the resilient housing coupling element. The electromagnet can be provided for applying a counterforce to the spring and compressing the spring for the targeted reduction of the braking force acting on the elastic housing coupling element. In other words, when the electromagnet is fully energized, the force generating device can rotate freely in the housing, so that the pressure plate does not exert a force on the friction disk and the elastic housing coupling element. In contrast, when the electromagnet is not energized, the spring can press the pressure plate against the friction disk and against the elastic housing coupling element with the full spring force, so that the braking-side end of the elastic housing coupling element does not rotate inside the housing, but rather an elastic deformation (torsion) of the elastic housing coupling element and the elastic coupling element is performed by the rotation of the steering wheel, whereby a feedback force acting on the steering wheel can be simultaneously provided. It should be noted that the electromagnet can be adjusted, energized or regulated in such a way that a targeted braking force can be set and thus also a targeted feedback force can be generated.

Preferably, the feedback force generated according to the invention is used only to feedback the current steering state to the driver. In order to simulate other feedback information (for example the end stop positions of the wheels, which can be sensed by corresponding end stops on the steering wheel, or the surface structure of the roadway, which is fed back by corresponding mechanical vibrations), it is proposed according to a further development that the steering wheel unit further comprises an electric motor connected to the steering wheel shaft for the purpose of simulating, in a motion-superimposed manner, only this further steering and driving state. In this solution of the invention, the torque generated by the electric motor or the additionally generated force is therefore used only to reduce or increase the force generated by the elastic housing coupling element and the elastic coupling element in a targeted manner in order to generate a real driving sensation on the steering wheel. The electric power consumption of the steering wheel unit of the invention is therefore much lower compared to the fully actively controlled steering wheel units of the prior art described at the beginning. Energy, installation space, costs and weight can thereby be saved.

According to a preferred embodiment, it is proposed that the electric motor is connected in a force-fitting manner to the steering wheel shaft by means of a force transmission element and a one-way coupling using a shaft for changing the rotational speed of the motor. Here, the shaft may be connected to the steering wheel shaft through a grooved portion. The electric motor and the force transmission element can be arranged parallel and axially offset outside the housing. This ensures a compact design of the steering wheel unit. The one-way coupling here transmits force only from the electric motor in the direction of the shaft, but not from the shaft in the direction of the electric motor. The force transmission element can be formed, for example, by a belt and a corresponding belt pulley. Alternatively or additionally, the force transmission element can also be a gear pair, a chain with a corresponding gear or a friction wheel pair.

According to one embodiment, it is proposed that the housing is designed in two parts (or two parts). The first housing part and the second housing part are screwably connected, wherein the screwed connection can be fixed by means of a union nut. The first housing part may have bearings for supporting the steering wheel shaft and the elastic housing coupling element, so that it can rotate inside the housing. The second housing part can be connected to the electromagnetic brake such that it can support the generated braking force on the second housing part.

Another aspect of the invention relates to an electromechanical steering system having the steering wheel unit described above and below. The electromechanical steering system also has an electromechanical steering actuator unit for mechanically adjusting the steerable axle and, if necessary, an electronic control unit. The control unit may comprise, for example, a computing unit, such as a processor, and a memory unit, and is provided for outputting control commands to the steering actuator unit. In this case, the electromechanical steering system can obtain a preset value from a steering motion sensor, which is then converted by the electronic control unit into a control command for the steering actuator unit, for example an electric motor. The steering actuator unit in turn influences the wheels of the vehicle in such a way that they rotate according to the preset values of the steering motion sensor. This results in a steerable axle. The steering movement sensor may in particular be arranged to detect the steering wheel attitude.

Drawings

Further refinements of the invention are explained in detail below with reference to the drawing together with the description of preferred embodiments of the invention. Shown in the attached drawings:

FIG. 1 is a schematic diagram of an electromechanical steering system for a motor vehicle;

FIG. 2 is a schematic cross-sectional view of a steering wheel unit of the steering system of FIG. 1;

FIG. 3 is a schematic longitudinal sectional view of a steering wheel unit of the steering system of FIG. 1 or FIG. 2; and

fig. 4 is a vehicle having a steering wheel unit of the steering system in fig. 1 to 3.

Detailed Description

According to fig. 1, an electromechanical steering system for a motor vehicle is essentially formed by a steering wheel unit 1, in whose cylinder housing 2a steering wheel shaft 3 is rotatably mounted. A steering wheel 4 for operation by a driver is mounted on a distal end of the steering wheel shaft 3.

Via an electrical connection 5, the steering wheel unit 1 is connected to a steering actuator unit 7 by means of an electronic control unit 6. The steering actuator unit 7 serves to convert a steering signal, which is electrically predetermined by the steering wheel unit 1 by means of the control device 6, into a mechanical adjustment of the steering angle of the

wheels

8a and 8b of the vehicle axle 9, which can be actuated in this case.

Fig. 2 shows a cross-sectional view of the steering wheel unit 1 along section a-a. The first housing part 2a encloses the force-generating device 10. The force generating device 10 has (from the outside to the inside to the center) a resilient housing coupling element 13, a resilient coupling element 12 and an inner connecting element 11. The elastic housing coupling element 13 coaxially surrounds the elastic coupling element 12 and the elastic coupling element 12 in turn coaxially surrounds the inner connecting element 11. Furthermore, it can be seen in fig. 2 that the inner connecting element 11 and the elastic coupling element 12 are designed in a star shape with three points. It should be noted that other cross-sections of the inner connecting element 11 and the elastic coupling element 12 are also conceivable, for example four, five or more sharp corners. The star-shaped embodiment makes it possible to increase the contact surface, so that better force transmission between the

individual elements

11, 12, 13 is possible and slipping between these

elements

11, 12, 13 is avoided. It should be noted that the elastic coupling element 12 is connected in a non-positive manner to the inner connecting element 11, and the elastic coupling element 12 is connected in a positive manner to the elastic housing coupling element 13. Furthermore, the force generating device 10 is rotatably supported relative to the first housing part 2 a. In other words, the elastic housing coupling element 13, the elastic coupling element 12 and the inner connecting element 11 can rotate within the first housing part 2 a.

The steering wheel shaft of the vehicle can be flanged to the inner connecting element 11. The steering wheel can thus be transferred to the inner connecting element 11 by the driver rotating or swiveling. The elastic housing coupling element 13 can be fixed or braked by means of a brake. The elastic housing coupling element 13 and the elastic coupling element 12 can be elastically deformed (twisted) if the elastic housing coupling element 13 is fixed by a brake and at the same time the steering wheel is rotated or turned by the driver. Due to this deformation (torsion), a reaction force is generated, which increases with elastic deformation or an increase in the steering angle. In other words, as the angle of rotation increases, further rotation of the steering wheel becomes increasingly difficult for the driver. By means of this elastic deformation and the resulting force, a feedback force can be generated for the driver, which feedback force corresponds to the feedback force of a purely mechanical system. Furthermore, the electric motor for generating the additional feedback force can be designed smaller. This saves weight and installation space. Furthermore, energy can be saved by means of smaller electric motors, since smaller electric motors require less energy than larger electric motors and do not have to be operated permanently.

These

elastic elements

12, 13 may be made of synthetic material or rubber, for example, with the same or different degrees of elasticity. Alternatively or additionally, these

elastic elements

12, 13 may have a degree of elasticity that is linear or increases with applied force. It should be noted that these

elastic elements

12, 13 may be described as springs, wherein the degree of elasticity may be considered as a spring coefficient.

As shown in fig. 3, in the steering wheel unit 1, a torque applied to the steering wheel 4 by the driver due to a steering motion is transmitted to the inside of the

housings

2a, 2b through the steering wheel shaft 3. The

housing

2a, 2b has a first housing part 2a and a second housing part 2 b. The two

housing parts

2a, 2b are screwed to one another and locked with a union nut 2 c. The force generating device is rotatably supported in the first housing part 2a by means of bearings 24 b. The second housing part 2b has an electromagnetic brake 19 and a shaft 18.

The force generating device has an internal connecting element 11, an elastic coupling element 12 and an elastic housing coupling element 13. The elastic coupling element 12 at least partially surrounds the inner connecting element 11, and the elastic housing coupling element 13 at least partially surrounds the elastic coupling element 12. The steering wheel shaft 3 is rotatably mounted in a bearing 24a and is fixedly connected to the inner connecting element 11. The rotation or rotation of the steering wheel shaft 3 can thereby be transmitted to the inner connecting element 11. Furthermore, the elastic housing coupling element 13 and the elastic coupling element 12 can be elastically deformed (twisted) under force, as a result of which a counterforce can be generated. This reaction force may be used as a feedback force for the driver of the vehicle. Further, the reaction force rises according to the elastic deformation, so that a feedback force that can be generated on the steering wheel 4 for feeding back the steering state relating to the wheel steering angle to the driver increases as the adjustment of the steering wheel 4 that deviates from straight running increases.

The electromagnetic brake 19 has an electromagnet 20, a spring 21, a pressure plate 22, and a friction plate 23. Here, friction disks 23 may be arranged between the pressure plate 22 and the elastic housing coupling element 13. Furthermore, the spring 21 is provided for exerting a force on the pressure plate 22, so that the pressure plate 22 is pressed against the friction plate 23 and the elastic housing coupling element 13, so that a braking force acting on the elastic housing coupling element 13 can be generated. When the electromagnet 20 is energized accordingly, it can attract the pressure plate 22 and thereby exert a counterforce on the spring 21. As a result, the spring 21 no longer presses the pressure plate 22 against the friction disk 23 and the elastic housing coupling element 13. As a result, the spring 21 no longer presses the pressure plate 22 against the friction disk 23 and the elastic housing coupling element 13. As a result, no braking force is applied to the elastic housing coupling element 13 and the latter can be rotated. It should be noted that the electromagnet 20 can be provided such that, in combination with the spring 21, it exerts a targeted braking force on the elastic housing coupling element 13.

Furthermore, an electric motor 15 can be provided for generating additional superimposed feedback forces for the steering and/or driving state. The electric motor 15 is provided parallel to the steering wheel shaft 3 and offset in the axial direction. Furthermore, the electric motor 15 can transmit its force or its torque to the force transmission element 14, which in turn transmits the force to the shaft 18 via the one-way coupling 16. The shaft 18 is connected to the steering wheel shaft 3 via a groove, so that force transmission is possible. The force-transmitting element 14 can be embodied, for example, as a belt 14 and a belt pulley 17, a chain and a gearwheel, a gearwheel pair or a friction wheel pair. The one-way coupling 16 is provided for transmitting forces from the electric motor 15 to the shaft 18, but not from the shaft 18 to the electric motor 15, whereby forces can be made to "flow" in one direction only. In other words, the electric motor 15 can add or subtract force to or from the force generated by the force generating device in a targeted manner, so that the driver can feel a feedback force corresponding to the wheel position.

Fig. 4 shows a vehicle 25 with an electromechanical steering system comprising the steering wheel unit 1 described above and below. Typically, the electromechanical steering system is arranged in the front region of the vehicle 25 and is provided for turning or steering the front wheels of the vehicle 25 as intended by the driver. Alternatively or additionally, the electromechanical steering system may also act on the rear wheels, for example in the case of active rear wheel steering or a forklift. The steering wheel unit 1 may be arranged, for example, in the region of the driver's seat under the dashboard in the direction of the engine compartment.

The invention is not limited to the preferred embodiments described above. On the contrary, all the variants covered by the scope of protection of the following claims are conceivable. For example, the cross section of the elastic coupling element or the internal connecting element can also have a shape other than a three-pointed star or the elastic housing coupling element is in direct contact with the internal connecting element. Furthermore, the steering actuator unit 7 may also be configured as an electrohydraulic unit or the like.

List of reference numerals

1 steering wheel unit

2(a, b) casing

2c lock nut

3 steering wheel shaft

4 steering wheel

5 electric connection part

6 electronic control device

7-turn actuator unit

8 wheel

9 vehicle bridge

10 force generating device

11 internal connecting element

12 elastic coupling element

13 elastic housing coupling element

14 force transmission element

15 electric motor

16 one-way coupling

17 transfer wheel

18-shaft

19 electromagnetic brake

20 electromagnet

21 spring

22 pressing plate

23 Friction disk

24a, b bearing

25 motor vehicle.

Claims

1. A steering wheel unit (1) for an electromechanical steering system of a motor vehicle (25), having:

a steering wheel shaft (3);

a housing (2a, 2 b); and

a force generating device (10) for applying a mechanical feedback force to the steering wheel (4) for feedback of the current steering and/or driving state to the driver;

it is characterized in that the preparation method is characterized in that,

the force generating device (10) is arranged inside the housing (2a, 2b), wherein the force generating device (10) has an inner connecting element (11), an elastic coupling element (12) and an elastic housing coupling element (13), wherein the elastic coupling element (12) at least partially coaxially surrounds the inner connecting element (11) and is connected to it in a force-fitting manner, wherein the elastic housing coupling element (13) at least partially coaxially surrounds the elastic coupling element (12) and is connected to it in a form-fitting manner, wherein the inner connecting element (11) is connected to the steering wheel shaft (3) at the end, wherein the force generating device (10) applies a force to the steering wheel shaft (3) such that the adjustment increases as the steering wheel (4) deviates from a straight line, a feedback force that can be generated on the steering wheel (4) and that is used for feeding back the steering state related to the steering angle of the wheels to the driver is increased.

2. Steering wheel unit (1) according to claim 1, characterized in that the steering wheel unit (1) further comprises an electromagnetic brake (19), wherein the electromagnetic brake (19) is fixedly connected with the housing (2a, 2b) and is provided for applying a braking force to the elastic housing coupling element (13).

3. Steering wheel unit (1) according to claim 2, characterized in that the electromagnetic brake (19) has a spring (21), a pressure plate (22), a friction disc (23) and an electromagnet (20), the friction disc (23) being arranged between the pressure plate (22) and the elastic housing coupling element (13), wherein the spring (21) is provided for exerting a force on the pressure plate (22) and pressing the pressure plate (22) against the friction disc (23) and the pressure plate against the elastic housing coupling element (13) for exerting a braking force on the elastic housing coupling element (13), wherein the electromagnet (20) is provided for exerting a counter force on the spring (21) for reducing the braking force acting on the elastic housing coupling element (13).

4. Steering wheel unit (1) according to one of the preceding claims, characterized in that the steering wheel unit (1) further has an electric motor (15) connected to the steering wheel shaft (3) for the movement to simulate, superimposed, further steering and/or driving conditions, in particular the end stop positions of the wheels (8a, 8b) and the surface structure of the lane.

5. Steering wheel unit (1) according to claim 4, characterized in that the electric motor (15) is arranged parallel and axially offset with respect to the steering wheel shaft (3) and is connected with the steering wheel shaft (3) by means of a force transmission element (14), a one-way coupling (16) and a shaft (18).

6. Steering wheel unit (1) according to claim 5, characterized in that the force transmitting element (14) is a belt, a gear pair, a friction wheel pair or a chain.

7. Steering wheel unit (1) according to one of the preceding claims, characterized in that the cross section of the inner connecting element (11) and the elastic housing coupling element (13) is star-shaped.

8. Steering wheel unit (1) according to one of the preceding claims, characterized in that the elastic coupling element (12) and the elastic housing coupling element (13) have different elasticity.

9. Steering wheel unit (1) according to one of claims 2 to 8, characterized in that the housing (2a, 2b) is embodied in two parts, a first housing part (2a) being screwably connected to a second housing part (2b), wherein the first housing part (2a) has bearings (24a, 24b) for supporting the steering wheel shaft (3) and the elastic housing coupling element (13), and the second housing part (2b) is connected to the electromagnetic brake (19).

10. An electromechanical steering system for a motor vehicle (25), comprising a steering wheel unit (1) according to any of the preceding claims and an electromechanical steering actuator unit (7) for mechanically adjusting the steering angle of the wheels (8a, 8b) of a steerable axle (9).