Torque feedback unit, steer-by-wire system, and vehicle

Abstract

A torque feedback unit (2) for a steer-by-wire system of a vehicle, comprising: a rotary damper (21), a feedback motor (22), and a torque-increasing device (23), wherein the rotary damper (21) has a first input end (211) and a first output end (216), the torque-increasing device (23) has a second input end (231) and a second output end (232), the first input end (211) is connected in a torsionally fixed manner to a steering wheel (1) of the steer-by-wire system, the first output end (216) is connected in a torsionally fixed manner to the second input end (231).

Description

[0001] Description

[0002] Torque Feedback Unit, Steer-by-Wire System, and Vehicle

[0003] Technical Field

[0004] The present invention relates to the field of vehicle steer-by-wire, and in particular to a torque feedback unit for a vehicle and a steer-by-wire system having such a torque feedback unit.

[0005] Background Art

[0006] Conventional vehicle steering systems require a mechanical connection between a steering wheel and steered wheels. In steer-by-wire systems, the mechanical connection is eliminated. In order to simulate a typical driver’s driving experience, namely to simulate road feel, a torque feedback unit is required to provide realistic steering feedback by simulating the steering resistance of a mechanical transmission connection.

[0007] From DE 102018101528 B4 a torque feedback unit is known, which has a worm-gear- drive motor arranged at the end of the steering column remote from the steering wheel. A worm gear can achieve a high reduction ratio and thus a high torque, but the gear structure requires a large amount of space.

[0008] From CN 111741886 B a steer-by-wire system is known having a feedback actuator. This feedback actuator has an electric motor, and the electric motor drives a steering shaft via a drive member, the drive member being connected to the steering shaft for transmitting torque.

[0009] From CN 116902066 A a resistance-feedback steering execution device is known, having an electric device module for simulating road feel, including a motor power assembly, a reduction mechanism, and a torque-angle sensor, wherein the reduction mechanism is a worm gear mechanism, and the overall structure occupies a large system space.

[0010] It can thus be seen that, in torque feedback units known from the prior art, more space is required in the axial or radial direction, which is evidently unfavorable for arranging a steer-by-wire system. Alternatively, a steer-by-wire system may provide feedback torque only by means of a high-power motor, which makes the system package larger and is unfavorable to flexible arrangement of the steering wheel.

[0011] Summary of the Invention The technical problem to be solved by the present invention is to provide an improved torque feedback unit, which is of compact structure and especially saves axial space, thereby enabling more flexible arrangement of the steering wheel.

[0012] The above technical problem is solved by a torque feedback unit for a steer-by-wire system of a vehicle designed according to the present invention. The torque feedback unit comprises: a rotary damper, a feedback motor, and a torque-increasing device. The rotary damper has a first input end and a first output end, the first input end being connected in a torsionally fixed manner to a steering wheel of the steer-by-wire system, and the first output end being connected in a torsionally fixed manner to a second input end of the torque-increasing device. A second output end of the torqueincreasing device is connected in a torsionally fixed manner to a motor rotor of the feedback motor. The feedback motor is an outer-rotor motor, the torque-increasing device is arranged coaxially with the feedback motor, and the torque-increasing device is arranged radially inside a motor stator of the feedback motor. According to the design scheme of the present invention, the road-feel torque of the torque feedback unit is mainly provided by the rotary damper, and only under certain special operating conditions, for example when a driver holds the steering wheel while getting in or out of the vehicle, is the feedback motor required to provide supplemental resisting torque, thereby avoiding the use of a high-power motor. By configuring the feedback motor as an outer-rotor motor and disposing the torque-increasing device radially inside the motor stator, the axial space is shortened and the overall system space occupation is reduced, enabling more flexible arrangement manner and position of the steering wheel.

[0013] In preferred embodiments of the invention, the rotary damper is a magnetorheological damper. The rotary damper may be a hydraulic rotary damper, a pneumatic rotary damper, a magnetorheological rotary damper, an electromagnetic rotary damper, a friction rotary damper, and the like. According to the design scheme of the present invention, a magnetorheological damper is particularly preferred. It uses a magnetorheological liquid, whose viscosity can be changed under the action of a magnetic field, thereby providing adjustable damping force. The main features of a magnetorhe- ological damper include high response speed, controllable damping force, and compact structure, suitable for applications requiring precise control and rapid response, particularly suitable for road-feel simulation in a steer-by-wire system. Further preferably, the magnetorheological damper has a damper stator, a damper coil, and a damper rotor, and a magnetorheological fluid is filled between the damper rotor and the damper coil. By utilizing the characteristics of the magnetorheological fluid and filling it between the rotor and the coil, precise damping adjustment can be achieved, improving sensitivity of the steering system. Further preferably, a ferromagnetic fluid is used as the magnetorheological fluid. A ferromagnetic fluid is formed by suspending micron-scale ferromagnetic particles in a liquid carrier. Compared with other magnetorheological fluids, ferromagnetic fluid has a faster response, higher stability, better magnetic permeability, and better lubricity, and is therefore more suitable for being filled between the coil and the rotor. In addition, it may be considered to arrange a double-row rolling bearing between the first input end of the magnetorheological damper and the damper stator. The first input end is connected in a torsionally fixed manner to the steering wheel and rotates at a relatively high frequency; using a double-row rolling bearing can improve system stability, thereby improving durability and service life of the system.

[0014] In preferred embodiments of the invention, the torque-increasing device is a planetary gear mechanism. The torque-increasing device is particularly a gear mechanism. The planetary gear mechanism is preferably selected because it is compact, small in size, light in weight, high in transmission efficiency, and high in load-carrying capacity. Further preferably, the planetary gear mechanism has a sun gear and a planet carrier, the sun gear serving as the second input end is connected in a torsionally fixed manner to the first output end of the rotary damper, and the planet carrier serving as the second output end is connected in a torsionally fixed manner to a rotor carrier of the motor. This embodiment can improve torque transmission efficiency of the system through the transmission characteristics of the planetary gear.

[0015] In preferred embodiments of the invention, the torque feedback unit has a control device in signal communication with the rotary damper and the feedback motor. The control device can adjust torque outputs of the rotary damper and the feedback motor according to different operating conditions. The torque feedback unit according to the in- vention has two torque output units, namely the rotary damper and the feedback motor. During normal vehicle driving, the control device transmits signals to the rotary damper according to the road condition, thereby outputting road-feel torque to the steering wheel to let the driver obtain road-feel feedback. In this case, the feedback motor does not output a torque opposing rotation of the steering wheel. In certain special cases requiring a relatively large opposing torque, for example when the driver holds the steering wheel while getting in or out of the vehicle and the steering wheel should remain stationary, the feedback motor is activated to output opposing torque, which is superposed with the opposing torque provided by the rotary damper to keep the steering wheel relatively stationary.

[0016] Furthermore, the technical problem to be solved by the present invention can also be solved by a steer-by-wire system. The system has a torque feedback unit including the above features. The system can realize high-precision steering control with small space occupation, thereby improving vehicle handling performance. In addition, the technical problem to be solved by the present invention can also be solved by a vehicle. The vehicle has a steer-by-wire system including the above features. The vehicle can improve overall performance and driving experience through the advanced steer- by-wire system.

[0017] Brief Description of the Drawings

[0018] The features, advantages, and technical effects of exemplary embodiments of the invention will be described below with reference to the drawings. FIG. 1 shows a steer- by-wire system of a vehicle. FIG. 2 shows a sectional view of a torque feedback device designed according to the present invention. FIG. 3 shows a sectional view of a magnetorheological damper. FIG. 4 shows a sectional view of a motor and a torque increaser.

[0019] In the following, specific embodiments of the present application are described with reference to the drawings. In the drawings, the same or similar reference numerals denote the same or similar parts, and repeated descriptions thereof are omitted for simplicity. Detailed Description of the Embodiments FIG. 1 shows a steer-by-wire system of a vehicle, in particular a steer-by-wire system of a new-energy vehicle. The steer-by- wire system according to the present invention comprises a steering wheel 1 , a torque feedback device 2, a Hall sensor 3, a CAN bus 4, an external controller 5, a steering motor 6, a steering actuator 7, and steered wheels 8. The torque feedback device 2 has a magnetorheological damper 21 and an outer-rotor motor 22. The Hall sensor 3 is integrated in the outer-rotor motor 22 for calculating an angular position of the steering wheel 1 . When the driver operates the steering wheel, the control system can calculate, based on data input from the external controller 5 via the CAN bus 4, a current of the outer-rotor motor 22 as an input signal transmitted to the steering motor 6. The steering motor 6 operates the steering actuator 7 to drive the steered wheels 8 to perform a vehicle steering operation.

[0020] FIG. 2 shows a sectional view of the torque feedback device 2 designed according to the present invention. The torque feedback device 2 includes the magnetorheological damper 21 , the outer-rotor motor 22, and a torque-increasing device 23 coaxially arranged with the outer-rotor motor 22. In order to save axial structural space, in the embodiment of the present invention an outer-rotor motor 22 is used. In addition to being able to output a high torque, it can also provide axial internal installation space for the torque-increasing device 23, thereby compressing axial structural space. In the present embodiment, the torque-increasing device 23 is designed as a planetary gear mechanism. Of course, other mechanical structures may also be considered as the torque-increasing device 23.

[0021] FIG. 3 shows a sectional view of the magnetorheological damper 21 . The magnetorheological damper 21 includes a rotating shaft (serving as an input end 211 and an output end 216), a damper stator 212, a damper coil 213, a damper rotor 215, and a magnetorheological fluid 214 between the damper coil 213 and the damper rotor 215. For clarity in FIG. 3, a cover 218 for closing the magnetorheological damper 21 (as shown in FIG. 2) is omitted. The control system controls a current in the magnetorheological damper 21 so that a magnetic field is generated or not generated in the magnetorheological damper 21 , thereby adjusting an output torque at the first output end 216. When a magnetic field is generated by the damper coil 213, the magnetorheological fluid 214 in the magnetorheological damper 21 gradually changes into a solid-like state having viscosity and elasticity upon passing through the magnetic field, so that a damping force is generated in the magnetorheological damper 21 and torque is output to the rotating shaft; when no magnetic field is generated, the magnetorheological fluid returns to a fluid state, and at this time the damping force in the magnetorheological damper 21 is reduced or not generated, thereby not outputting torque to the rotating shaft. In this embodiment, by controlling the magnitude of the current introduced into the magnetorheological damper 21 , the magnitude of the magnetic field generated in the magnetorheological damper 21 can be adjusted, thereby controlling the state of the magnetorheological fluid 214 in the magnetorheological damper 21 , precisely controlling the magnitude of the damping force generated by the magnetorheological damper 21 , and thus precisely controlling the magnitude of the torque output by the magnetorheological damper 21 to the rotating shaft, so as to achieve precise regulation of the output torque.

[0022] FIG. 4 shows a sectional view of the feedback motor 22 and the torque-increasing device 23. In the embodiment of the invention, the feedback motor 22 is an outer-rotor motor having a motor rotor 221 and a motor stator 222, the motor rotor 221 being arranged radially outside the motor stator 222. A planetary gear mechanism 23 serving as the torque-increasing device is arranged in a motor cavity formed radially inside the motor stator 222. A sun gear of the planetary gear mechanism 23 serves as the second input end 231 . A planet carrier of the planetary gear mechanism 23 is connected in a torsionally fixed manner to a rotor carrier of the motor rotor 221 , and serves as a second output end 232 to output torque to the motor rotor 221 . Because the planetary gear mechanism 23 is arranged coaxially with the feedback motor 22 and occupies only the space within the motor cavity, the axial space of the device is greatly reduced, allowing the steering wheel 1 to be arranged more flexibly.

[0023] The torque feedback device 2 designed according to the present invention further has a control device, which can be integrated with a control system of the steer-by-wire system. The control device is respectively connected to the feedback motor 22 and the rotary damper 21 , and is configured to control activation of at least one of the feedback motor 22 and the rotary damper 21 , so that the activation or deactivation of the feedback motor 22 and the rotary damper 21 can be reasonably controlled accord- ing to the vehicle operating conditions, thereby avoiding unnecessary resource consumption.

[0024] It is evident that the above embodiments of the present invention are merely examples given for clearly illustrating the invention, and are not intended to limit the embodiments of the invention. For those of ordinary skill in the art, other different forms of variations or modifications can be made on the basis of the above description. It is neither necessary nor possible to exhaustively enumerate all embodiments here. Any modifications, equivalent replacements, and improvements made within the spirit and principles of the invention shall be included within the protection scope of the claims of the invention. In addition, the terms “first,” “second,” are used solely for descriptive purposes and should not be understood as indicating or implying relative importance.

[0025] List of Reference Numerals

[0026] 1 steering wheel

[0027] 2 torque feedback device

[0028] 21 rotary damper; magnetorheological damper

[0029] 211 first input end

[0030] 212 damper stator

[0031] 213 damper coil

[0032] 214 magnetorheological fluid

[0033] 215 damper rotor

[0034] 216 first output end

[0035] 217 double-row rolling bearing

[0036] 218 cover

[0037] 22 feedback motor; outer-rotor motor

[0038] 221 motor rotor

[0039] 222 motor stator

[0040] 23 torque-increasing device; planetary gear mechanism

[0041] 231 second input end

[0042] 232 second output end

[0043] 3 Hall sensor

[0044] 4 CAN bus

[0045] 5 external controller

[0046] 6 steering motor

[0047] 7 steering actuator

[0048] 8 steered wheels

[0049] Drawings of the Description FIG. 1 FIG. 2 FIG. 3 FIG. 4

Claims

Claims1 . A torque feedback unit (2) for a steer-by-wire system of a vehicle, comprising: a rotary damper (21 ), a feedback motor (22), and a torque-increasing device (23), wherein the rotary damper (21 ) has a first input end (211 ) and a first output end (216), the torque-increasing device (23) has a second input end (231 ) and a second output end (232), the first input end (211 ) is connected in a torsionally fixed manner to a steering wheel (1 ) of the steer-by-wire system, the first output end (216) is connected in a torsionally fixed manner to the second input end (231 ), and the second output end (232) is connected in a torsionally fixed manner to a motor rotor (221 ) of the feedback motor (22), wherein the feedback motor (22) is an outer-rotor motor, the torque-increasing device (23) is arranged coaxially with the feedback motor (22), and the torque-increasing device (23) is arranged radially inside a motor stator (222) of the feedback motor (22).

2. The torque feedback unit (2) according to claim 1 , wherein the rotary damper (21 ) is a magnetorheological damper.

3. The torque feedback unit (2) according to claim 2, wherein the magnetorheological damper has a damper stator (212), a damper coil (213), and a damper rotor (215), and a magnetorheological fluid (214) is filled between the damper rotor (215) and the damper coil (213).

4. The torque feedback unit (2) according to claim 3, wherein the magnetorheological fluid (214) is a ferromagnetic fluid.

5. The torque feedback unit (2) according to claim 3, wherein a double-row rolling bearing (217) is arranged between the first input end (211 ) and the damper stator (212).

6. The torque feedback unit (2) according to any one of claims 1 to 5, wherein the torque-increasing device (23) is a planetary gear mechanism.

7. The torque feedback unit (2) according to claim 6, wherein the planetary gear mechanism has a sun gear and a planet carrier, the sun gear serving as the second input end (231 ) is connected in a torsionally fixed manner to the firstoutput end (216), and the planet carrier serving as the second output end (232) is connected in a torsionally fixed manner to the motor rotor (221 ).

8. The torque feedback unit (2) according to claim 1 , wherein the torque feedback unit (2) has a control device, the control device being in signal communication with the rotary damper (21 ) and the feedback motor (22), and the control device being configured to adjust torque outputs of the rotary damper (21) and the feedback motor (22) according to different operating conditions.

9. A steer-by-wire system, characterized in that the steer-by-wire system has the torque feedback unit (2) according to any one of claims 1 to 8.

10. A vehicle, characterized in that the vehicle has the steer-by-wire system according to claim 9.

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