Electric screw actuator system

• US 20030139243A1
• Filed: 12/02/2002
• Published: 07/24/2003
• Est. Priority Date: 04/11/2000
• Status: Active Grant

• Current Assignee: SKF Engineering & Research Centre BV
• Original Assignee: SKF Engineering & Research Centre BV
• Inventors: Kapaan, Hendrikus Jan, Nervo, Aurello, Holweg, Eduardus Gerardus Maria
• Granted Patent: US 7,052,427 B2
• Time in Patent Office: Days
• US Class Current: 475/149
• CPC Class Codes: B62D 1/163 Part of the steering column replaced by flexible means, e.g. cable or belt
• CPC Class Codes: B62D 5/003 Backup systems, e.g. for manual steering B62D5/30 takes precedence
• CPC Class Codes: B62D 5/0448 Ball nuts
• CPC Class Codes: F16H 25/20 Screw mechanisms with automatic reversal F16H25/12

Abstract

An electric screw actuator system, e.g. for an electrically driven and controlled steering device, comprises a screw actuator, an electric motor (2) engaging the screw actuator through a reduction gear mechanism (3), electronic operating means for operating the screw actuator electrically, and a mechanical back-up system for operating the screw actuator in the absence of electric power e.g. in the case of an electric power failure of in the case the electric power is switched off, maintenance, garage parking etc. The mechanical back-up system comprises a manually controllable operation member (4) and an electromagnetic coupling (6), said coupling disengaging the rotation member from the screw actuator in the case of nominal operation and availabitity of electric power, and engaging the rotation member with the screw actuator in the case of electric power failure.

Claims

1. Electric screw actuator system, e.g. for an electrically driven and controlled steering device, said system comprising a screw actor (1), an electric motor (2) engaging the screw actuator (1) through a reduction gear mechanism (3), electronic operating means (26) for operating the screw actuator (1) electrically, and a mechanical back-up system (4) for operating the screw actor (1) in the absence of electric power e.g. in the case of an electric power failure or in the case the electric power is switched off, maintenance, garage pang etc., said mechanical back-up system (4) comprising a manually controllable operation member (5) and an electromagnetic coupling (6), said coupling (6) disengaging the rotation member (5) from the screw actuator (1) in the case of nominal operation and availability of electric power, and engaging the rotation member (5) with the screw actuator (1) in the case of absence of electric power.

2. System according to claim 1, wherein an electromagnetic coupling (6) is connected to an auxiliary gear mechanism (7) which engages the actuator (1) in case of absence of electric power.

3. System according to claim 2, wherein the reduction gear mechanism (2) and the auxiliary gear mechanism (7) are integrated.

4. System according to claim 3, wherein the reduction gear mechanism (2) comprises a sun gear wheel (8) which is driveable by the electric motor (2), a fixed ring gear wheel (9) connected to one of the nut (12) and the screw (13), satellite gear wheels (10) which engage the sun gear wheel (8) and the ring gear wheel (9), and a carrier (11) onto which the satellite gear wheels (10) are rotatably mounted, said carrier (11) engaging the other of the nut (12) and the screw (13).

5. System according to claim 4, wherein the coupling (6) is connected to an auxiliary drive gear wheel (14) which engages the screw actor (17).

6. System according to claim 5, wherein the auxiliary drive gear wheel (14) engages an auxiliary carrier (15) onto which auxiliary satellite gear wheel (16) are rotatably mounted, said auxiliary satellite gear wheels (16) engaging an auxiliary ring gear wheel (17) which is fixed with respect to the other ring gear wheel (9), and an auxiliary sun gear wheel (18) connected to the other carrier (11).

7. System according to any of claims 2-6, wherein the auxiliary gear mechanism (7) is an accelerating gear mechanism.

8. System according to any of claim 4-7, wherein the nut (12) of the screw actuator (1) is connected to a housing (19), said housing (19) furthermore carrying the fixed ring gear wheels (5, 9, 17) which is (are) concentric with respect to the out (11) and the screw (12), as well as the electromagnetic coupling (6).

9. System according to claim 8, wherein the screw (12) engages the carrier (11) through a spline/ball mechanism (20).

10. System according to claim 8 or claim 9, wherein the axis of the coupling (6) is transverse with to the axis of the screw actuator (1), and the coupling (6) engages the auxiliary gear mechanism (7) through bevel gears (14, 21).

11. System according to any of the preceding claims, wherein the mechanical back-up system (4) comprises a flexible cable drive (22), capable of transmission a torque, or a pulling cable or a mechanical linkage, which at one end is connected to the coupling (6), and which at the other end is provided with an hand operated lever means (23), e.g. a steer, joystick or the like.

12. System according to claim 11, wherein the manually operated lever means (23) has a swivel point (24) which is fixed with respect to the screw actuator (1), the flexible cable drive (22) being connected to the lever means (22) at the swivel point (24) thereof, electromagnetic immobilisation means (25) being provided for preventing rotation of the lever means (23) in the case of nominal operation and availability of electric power, and for allowing rotation of the lever means (23) in the case of electric power failure.

13. System according to claim 12, wherein the lever means (23) carries said electronic operating means (26) for operating the screw actuator (1) electrically.

14. System according to claim 13, wherein the electronic operating means comprises a joy stick (26).

15. System according to claim 14, wherein the joystick is at a distance from the swivel point (24).

16. System according to claim 14, wherein the joystick (26) is directly mounted to the swivel point (24), and is rotatable and/or liftable (x-y-z axis).

17. System according to any of the preceding claims, wherein a sensor is provided for monitoring and controlling a displacement and/or a rotation of e.g. the nut and/or the screw in closed loop configuration with the electric motor (2), the electronic operating means (26), and an electronic control unit (27).

18. System according to any of the preceding claims, wherein the reduction gear mechanism (13) comprises an excentric gear reduction.

19. System according to any of the preceding claims, wherein the reduction gear mechanism (13) comprises a combination of bevel gears, and/or planetary gears, and/or excentric gears.

20. System according to any of the preceding claims, wherein the screw actuator (1) has a rotatably supported nut (12) and a non-rotatable, translatable screw (13).

21. System according to any of claims 1-19, wherein the screw actuator has a non-rotatable, translatable nut and a rotatably supported screw.

22. System according to claim 21, wherein the nut is connected to or integrated with a piston.

23. Electromechanical steering system, comprising an electric screw actuator system according the one of the claims 1-21, and comprising a joystick (26) having at least one force sensor and/or at least one displacement or rotation sensor steering, and/or braking, and or accelerating action.

24. Electromechanical brake system, comprising an electric screw actuator system according to one of claims 1-21.