Hand wheel actuator with steering-feel enhancement

• US 20040011585A1
• Filed: 07/17/2002
• Published: 01/22/2004
• Est. Priority Date: 07/17/2002
• Status: Active Grant

• Current Assignee: GM Global Technology Operations Incorporated (Motors Liquidation Co. GUC Trust), Steering Solutions IP Holding Corporation (Nexteer Automotive Group Ltd.)
• Original Assignee: Delphi Technologies, Inc. (Aptiv PLC)
• Inventors: Card, James M., Menjak, Ratko
• Granted Patent: US 6,820,713 B2
• Time in Patent Office: Days
• US Class Current: 180/402
• CPC Class Codes: B62D 5/006 power actuated
• CPC Class Codes: F16H 2025/2096 using endless flexible members

Abstract

A hand wheel actuator for a steer-by-wire steering system having a steering feel that meets drivers'"'"' expectations is provided with a first housing having an aperture, a steering shaft extending through the aperture and rotatably supported by the housing, an electric motor, a position sensor and torque sensor, and a mechanical steering feel enhancement device. The position and torque sensors, are positioned within said first housing and configured to detect the angular displacement of the steering shaft and torque applied against the steering shaft respectively. The mechanical steering feel enhancement device is attached to the first housing and provides at least one of a positive stop function, a return-to-center function, or a friction/weight function by mechanical means. The mechanical steering feel enhancement device is in mechanical communication with said steering shaft and is disposed in a second housing and existing as a separate unitary subassembly prior to being installed on said first housing. The electric motor is mounted to one of the first housing and second housing and has an output shaft that is in mechanical communication with the steering shaft for imparting a torque to the steering shaft.

Claims

1. A hand wheel actuator for a steer-by-wire steering system comprising:

a first housing having an aperture;

a steering shaft extending through said first housing, said steering shaft having an upper end adapted for attaching a hand wheel, and a lower end opposite said upper end, said steering shaft being rotatably supported by said first housing;

a position sensor and a torque sensor, each positioned within said first housing and configured to detect the angular displacement of the steering shaft and torque applied against the steering shaft respectively, said torque sensor being positioned between the upper end of the steering shaft and a location at which the motor applies torque to the steering shaft;

a mechanical steering feel enhancement device attached to said first housing, said mechanical steering feel enhancement device providing at least one of a positive stop function, a return-to-center function, or a friction/weight function by mechanical means, said mechanical steering feel enhancement device being in mechanical communication with said steering shaft, and said mechanical steering feel enhancement device being disposed in a second housing and existing as a separate unitary subassembly prior to being installed on said first housing; and

an electric motor mounted to one of said first housing and second housing, said electric motor having an output shaft in mechanical communication with said steering shaft for imparting a torque to said steering shaft.

2. The hand wheel actuator of claim 1 wherein said torque sensor is a non-compliant torque sensor, said first housing separating and shielding said non-compliant torque sensor from magnetic fields generated by said electric motor.

3. The hand wheel actuator of claim 1 wherein said mechanical steering feel enhancement device comprises a positive stop, said positive stop limiting travel of said hand wheel to a preselected angular displacement in either direction from a central position.

4. The hand wheel actuator of claim 3 wherein said positive stop mechanism comprises an inside gear engaging a pinion on said steering shaft, said inside gear having an axis of rotation substantially parallel to said steering shaft, said inside gear further having a stop surface extending from a hub of said inside gear to a perimeter, said stop surface engaging said pinion at limits of rotation of said steering shaft, said inside gear including a sloped outer surface which engages a roller cam, said roller cam being biased by a spring substantially radially towards said axis of rotation of said stop gear, said sloped surface and said roller cam interacting to provide a return-to-center function for said positive stop mechanism.

5. The hand wheel actuator of claim 1 wherein said steering feel enhancement device comprises a steering return/resistance device implementing a constant-force spring, said steering return/resistance device including an auxiliary shaft disposed substantially in parallel with said steering shaft, said auxiliary shaft being in mechanical communication with said steering shaft, said steering return/resistance device further comprising:

a first spool on said auxiliary shaft;

a second spool on said steering shaft, said constant force spring having a first end fixed to said first spool and a second end fixed to said second spool, said constant force spring extending between said first spool and said second spool.

6. A hand wheel actuator for a steer-by-wire steering system comprising:

a steering shaft, said steering shaft having an upper end adapted for attaching a hand wheel, and a lower end opposite the upper end;

a steering shaft housing, said steering shaft extending through said steering shaft housing and rotatably supported by said steering shaft housing, said steering shaft housing containing a mechanical steering feel enhancement device in mechanical communication with said steering shaft;

a driver interface electronics module attached to an upper end of said steering shaft housing, said driver interface electronics module comprising a control unit, a position sensor, and driver interface controls including a stalk-mounted switches;

said position sensor detecting relative angular displacement of said steering shaft relative to a nominal position, said driver interface electronics module existing as a subassembly prior to being mounted on said steering shaft housing;

an electric motor and a transmission placing said electric motor and said steering shaft in mechanical communication, said electric motor being attached to a lower portion of said steering shaft housing opposite said driver interface electronics module.

7. The hand wheel actuator of claim 6 wherein said driver interface electronics module includes a non-compliant torque sensor, said steering shaft extending through said non-compliant torque sensor when attaching said driver interface electronics module onto said steering shaft housing.

8. The hand wheel actuator of claim 6 wherein said control unit is in communication with said position sensor and a road wheel actuator, said control unit signaling said road wheel actuator to steer road wheels in response to rotations of the steering shaft sensed by said position sensor.

9. The hand wheel actuator of claim 8, driver interface electronics module including a torque sensor;

said control unit and said torque sensor being in electronic communication so that said control unit receives torque signals generated by said torque sensor, said torque signals being representative of torsion of the steering shaft;

said control unit also receiving force signals from said road wheel actuator, said force signals being representative of force exerted against said steering system, wherein said control unit drives said motor in response to said force signals and said torque signals.

10. The hand wheel actuator of claim 6 wherein said mechanical steering feel enhancement device comprises a positive stop, said positive stop limiting travel of said hand wheel to a preselected angular displacement in either direction from a central position.

11. The hand wheel actuator of claim 10 wherein said positive stop comprises a stop gear engaging a pinion on said steering shaft, said stop gear having a stop tooth preventing engagement thereby by said pinion such that said pinion and said steering shaft are limited by said stop tooth to a selected amount of angular displacement.

12. The hand wheel actuator of claim 10 wherein said positive stop mechanism comprises an inside gear engaging a pinion on said steering shaft, said inside gear having an axis of rotation substantially parallel to said steering shaft, said inside gear further having a stop surface extending from a hub of said inside gear to a perimeter, said stop surface engaging said pinion at limits of rotation of said steering shaft.

13. The hand wheel actuator of claim 12 wherein said inside gear includes a sloped outer surface which engages a roller cam, said roller cam being biased by a spring substantially radially towards said axis of rotation of said stop gear, said sloped surface and said roller cam interacting to provide a return-to-center function for said positive stop mechanism.

14. The hand wheel actuator of claim 6 wherein said steering feel enhancement device comprises a steering return/resistance device implementing a constant-force spring.

15. The hand wheel actuator of claim 14 wherein said steering return/resistance device includes an auxiliary shaft disposed substantially in parallel with said steering shaft, said auxiliary shaft being in mechanical communication with said steering shaft, said steering return/resistance device further comprising:

a first spool on said auxiliary shaft;

a second spool on said steering shaft, said constant force spring having a first end fixed to said first spool and a second end fixed to said second spool, said constant force spring extending between said first spool and said second spool.

16. The hand wheel actuator of claim 15 further comprising a first pulley on said steering shaft, a second pulley on said auxiliary shaft, and a belt extending from said first pulley to said second pulley thereby placing said auxiliary shaft in mechanical communication with said steering shaft.

17. The hand wheel actuator of claim 16 wherein said belt is a timing belt and has teeth engaging mating structures on each of said first pulley and said second pulley, thereby maintaining a constant turn ratio between said first pulley and said second pulley.

18. A hand wheel actuator for a steer-by-wire steering system comprising:

a steering shaft, said steering shaft having an upper end adapted for attaching a hand wheel, and a lower end opposite said upper end;

a steering shaft housing, said steering shaft extending through said steering shaft housing and rotatably supported by said steering shaft housing, an electric motor having an output shaft in mechanical communication with said steering shaft for imparting a torque to said steering shaft; and

a torque sensor and a position sensor positioned and configured to detect the angular displacement of the steering shaft and torque applied against the steering shaft, said torque sensor being positioned between the upper end of the steering shaft and a location at which the motor applies torque to the steering shaft;

a controller in electronic communication with the torque sensor, the position sensor, and the motor;

a steering feel enhancement device comprising an auxiliary shaft being rotatably supported substantially in parallel to and adjacent said steering shaft, said auxiliary shaft being in mechanical communication with said steering shaft such that rotation of one of said auxiliary shaft and said steering shaft causes an other of said auxiliary shaft and said steering shaft to rotate, said steering feel enhancement device including a first spool on said auxiliary shaft, a second spool on said steering shaft, and a constant force spring extending from said first spool to said second spool.

19. The hand wheel actuator of claim 18 wherein said constant force spring partially wound on each of said first spool and said second spool when said steering shaft is in a central position, said constant force spring generating a bias against said steering shaft tending said steering shaft to return to a central position when displaced therefrom.

20. The hand wheel actuator of claim 18 wherein said constant force spring has a first end fixed to said first spool and a second end fixed to said second spool, said constant force spring limiting angular displacement of said steering shaft from a central position to a selected angle when fully unwound from one of said first spool and said second spool.