Steer unit for steer-by-wire

• US 7,207,411 B2
• Filed: 07/25/2002
• Issued: 04/24/2007
• Est. Priority Date: 07/25/2001
• Status: Expired due to Term

• Current Assignee: AB SKF
• Original Assignee: AB SKF
• Inventors: Schmidt, Klemens, Van Der Ham, Andreas Clemens, Duits, Johannes Adrianus Maria, Van Der Kamp, Johannes Haaye
• Primary Examiner(s): Morris; Lesley D.
• Assistant Examiner(s): LUM VANNUCCI, LEE SIN YEE
• Application Number:
  US10/484,771
• Publication Number:
  US 20040262071A1
• Time in Patent Office: 1,734 Days
• Field of Search: 180/402, 180/403, 180/421, 180/422, 701 41- 43
• US Class Current: 180/402
• CPC Class Codes: B62D 5/005 means for generating torque on steering wheel or input member, e.g. feedback
• CPC Class Codes: B66F 9/07568 Steering arrangements

Abstract

Steer unit for steer-by-wire comprising angle sensing means (12) for detecting the angular position of a steering wheel (11), processing means (10) connected to the angle sensing means (12) and connectable to a wheel position sensor (22), the wheel position sensor (22) being arranged for providing an output signal representing the position of steered wheels (20) of a vehicle. The processing means (10) are connectable to a steering actuator (21) mechanically coupled to the steered wheels (20), the processing means (10) being arranged for driving the steering actuator (21) dependent on the angular position of the steering wheel (11). The steer unit further comprises friction means (14) for providing a friction force on the steering wheel (11), the friction means (14) being connected to the processing means (10), and the processing means (10) being arranged for driving the friction means (14) in dependence of the wheel position sensor output signal.

Claims

1. A steer unit for steer-by-wire comprising:

angle sensing means (12) for detecting an angular position of a steering wheel (11);

processing means (10) connected to the angle sensing means (12) and connectable to a wheel position sensor (22),

the wheel position sensor (22) being arranged for providing an output signal representing the angular position of steered wheels (20) of a vehicle,

the processing means (10) being connectable to a steering actuator (21) mechanically coupled to the steered wheels (20),

the processing means (10) being arranged for driving the steering actuator (21) dependent on the angular position of the steering wheel (11);

friction means (14) for providing a friction force on the steering wheel (11),

the friction means (14) being connected to the processing means (10),

the processing means (10) being arranged for driving the friction means (14) in dependence of the wheel position sensor output signal, wherein,

the processing means (10) are arranged to energise the friction means (14) at variable end-stops, and

the processing means (10) are arranged to increase the friction on the steering wheel (11) when a rotation rate of the steering wheel (11), as determined from the angle sensing means (12), is greater than a corresponding maximum rotation rate of the steering actuator (21).

2. Steer unit according to claim 1, in which a particular end-stop condition corresponds to mechanical limits of the steering actuator (21).

3. Steer unit according to claim 1, in which the processing means (10) are arranged to determine the end-stops based on at least one vehicle parameter.

4. Steer unit according to claim 3, in which the at least one parameter is one or more of the group of vehicle speed, load, load height.

5. Steer unit according to claim 1, in which the processing means (10) are arranged to gradually increase the friction on the steering wheel (11) when approaching an end-stop.

6. Steer unit according to claim 1, in which the processing means (10) are arranged to drive the friction means (14) to exert a higher friction force when the steering wheel (11) rotates in a first direction as compared to when the steering wheel (11) rotates in a direction opposite to the first direction.

7. Steer unit according to claim 1, in which the processing means (10) are arranged to adapt a ratio between the steering wheel rotation and a steered wheel rotation.

8. Steer unit according to claim 1, in which the friction means (14) engage a first part (17) of the steering wheel (11), and the steering wheel (11) comprises a flexible coupling (41) to the first part, and in which the processing means (10) are arranged to release the friction means (14) when a change of direction of the steering wheel is detected from the angular sensing means signal.

9. Steer unit according to claim 1, in which the steer unit further comprises a detection element (13) for detecting torque force on the steering wheel shaft (17), the detection element (13) being connected to the processing means (10).

10. Steer unit according to claim 1, in which the processing means (10) are arranged to reduce friction on the steering wheel shaft (17) when the detected torque force on the steering wheel (11) changes direction.

11. Steer unit according to claim 1, in which the steer unit further comprises at least one wheel torque sensor (23) detecting an external torque on the wheels (20) of the vehicle, the at least one wheel torque sensor (23) being connected to the processing means (10).

12. Steer unit according to claim 11, in which the processing means (10) are further arranged for driving the friction means (14) in dependence of the wheel torque sensor output.

13. Steer unit according to claim 1, in which the friction means (14) comprise an electrically controlled brake (15, 16).

14. Steer unit according to claim 13, in which the electromagnetic brake comprises a disc (15) attached to a shaft (17) of the steering wheel (11) and at least one electromagnetic coil (16) positioned substantially in parallel to the disc, the electromagnetic coil being connected to the processing means (10).

15. Steer unit according to claim 14, in which the disc (15) is attached to the shaft (17) of the steering wheel (11) by means of a flexible coupling.

16. Steer unit according to claim 1, in which the friction means (14) comprise mechanical blocking means (50, 51;

53).

17. Steer unit according to claim 16, in which the mechanical blocking means comprise a disc (50) attached to the steering wheel shaft (17), the disc (5) being provided with at least one saw tooth profile at its perimeter, and a blocking member (51) which is controllable by an actuator (52) between a blocking position and an idle position.

18. Steer unit according to claim 17, in which the actuator (52) comprises a sensor for sensing motion of the blocking member (51).

19. Steer unit according to claim 18, in which the mechanical blocking means comprise a disc (50) attached to the steering wheel shaft (17), the disc (50) being provided with semi-spherical indentations at its perimeter, and a blocking member (53) which is moveable between a first position in which the blocking member (53) engages the spherical indentation and a second position in which the disc (50) can rotate freely.

20. Steer unit according to claim 1, in which the friction means (14) engage a first part (17) of the steering wheel (11), and the steering wheel (11) comprises a clearance (41) to the first part, and in which the processing means (10) are arranged to release the friction means (14) when a change of direction of the steering wheel is detected from the angular sensing means signal.

21. Steer unit according to claim 1, in which the friction means (14) engage a first part (17) of the steering wheel (11), and the steering wheel (11) comprises a space for motion (41) to the first part, and in which the processing means (10) are arranged to release the friction means (14) when a change of direction of the steering wheel is detected from the angular sensing means signal.

22. Steer unit of claim 8, wherein, the flexible coupling is a steering shaft of an elastic material.

23. Steer unit of claim 8, wherein, the flexible coupling comprises elastic elements.