Vehicle steering system

• US 20080006470A1
• Filed: 07/09/2007
• Published: 01/10/2008
• Est. Priority Date: 07/10/2006
• Status: Active Grant

• Current Assignee: DENSO Corporation
• Original Assignee: DENSO Corporation
• Inventors: Kameya, Hisashi, Hidaka, Kenichirou
• Granted Patent: US 7,604,089 B2
• Time in Patent Office: Days
• US Class Current: 180/443
• CPC Class Codes: B62D 5/008 Changing the transfer ratio between the steering wheel and the steering gear by variable supply of energy, e.g. by using a superposition gear

Abstract

A storage part stores an initial sum, which is obtained by summing a steering angle of a steering wheel and a rotational angle of an electric actuator before checking of unlocking of a transmission ratio variable mechanism by a computer part. The computer part determines that the storage part is abnormal when a sum, which is obtained by summing the steering angle of the steering wheel and the rotational angle of the electric actuator after the checking of the unlocking of the transmission ratio variable mechanism by the computer part, differs from the initial sum, which is retrieved from the storage part.

Claims

1. A vehicle steering system comprising:

a transmission ratio variable mechanism that is placed between a steering wheel and steerable vehicle wheels in a vehicle and includes an electric actuator, which is rotated to change a transmission ratio between a steering angle of the steering wheel and a turning angle of the steerable vehicle wheels, wherein the transmission ratio variable mechanism makes a change in the turning angle of the steerable vehicle wheels in a generally linear relationship with a sum of the steering angle of the steering wheel and a rotational angle of the electric actuator;

a rotatable member that is rotated synchronously with the electric actuator;

a lock means for locking and unlocking the transmission ratio variable mechanism, wherein the lock means locks the transmission ratio variable mechanism by holding the rotatable member and unlocks the transmission ratio variable mechanism by releasing the rotatable member;

a control means for controlling the electric actuator and for checking whether the unlocking of the transmission ratio variable mechanism is succeeded by rotating the rotatable member through rotation of the electric actuator in a stopped state of the vehicle;

a storage means for storing an initial sum, which is obtained by summing the steering angle of the steering wheel and the rotational angle of the electric actuator before the checking of the unlocking of the transmission ratio variable mechanism by the control means; and

a sensing means for sensing an abnormality of the storage means, wherein the sensing means determines that the storage means is abnormal when a sum, which is obtained by summing the steering angle of the steering wheel and the rotational angle of the electric actuator after the checking of the unlocking of the transmission ratio variable mechanism by the control means, differs from the initial sum, which is retrieved from the storage means.

2. The vehicle steering system according to claim 1, wherein the initial sum is obtained and is stored in the storage means in a locked state of the transmission ratio variable mechanism.

3. The vehicle steering system according to claim 1, wherein the electric actuator includes:

an electric motor; and

a speed reducer that reduces a rotational speed of rotation, which is transmitted from the electric motor, and outputs the rotation of the reduced rotational speed.

4. A vehicle steering system comprising:

a transmission ratio variable mechanism that is placed between a steering wheel and steerable vehicle wheels in a vehicle and includes an electric actuator, which is rotated to change a transmission ratio between a steering angle of the steering wheel and a turning angle of the steerable vehicle wheels, wherein the transmission ratio variable mechanism makes a change in the turning angle of the steerable vehicle wheels in a generally linear relationship with a sum of the steering angle of the steering wheel and a rotational angle of the electric actuator;

a rotatable member that is rotated synchronously with the electric actuator;

a lock means for locking and unlocking the transmission ratio variable mechanism, wherein the lock means locks the transmission ratio variable mechanism by holding the rotatable member and unlocks the transmission ratio variable mechanism by releasing the rotatable member;

a control means for controlling the electric actuator and for checking whether the unlocking of the transmission ratio variable mechanism is succeeded by rotating the rotatable member through rotation of the electric actuator in a stopped state of the vehicle;

a storage means for storing an initial steering angle of the steering wheel and an initial rotational angle of the electric actuator, which are obtained before the checking of the unlocking of the transmission ratio variable mechanism by the control means; and

a sensing means for sensing an abnormality of the storage means, wherein the sensing means determines that the storage means is abnormal when a sum, which is obtained by summing the steering angle of the steering wheel and the rotational angle of the electric actuator after the checking of the unlocking of the transmission ratio variable mechanism by the control means, differs from a sum, which is obtained by summing the initial steering angle of the steering wheel and the initial rotational angle of the electric actuator that are retrieved from the storage means.

5. The vehicle steering system according to claim 4, wherein the initial steering angle of the steering wheel and the initial rotational angle of the electric actuator are obtained and are stored in the storage means in a locked state of the transmission ratio variable mechanism.

6. The vehicle steering system according to claim 4, wherein the electric actuator includes:

an electric motor; and

a speed reducer that reduces a rotational speed of rotation, which is transmitted from the electric motor, and outputs the rotation of the reduced rotational speed.

7. A vehicle steering system comprising:

a transmission ratio variable mechanism that is placed between a steering wheel and steerable vehicle wheels in a vehicle and includes an electric actuator, which is rotated to change a transmission ratio between a steering angle of the steering wheel and a turning angle of the steerable vehicle wheels;

a rotatable member that is rotated synchronously with the electric actuator;

a lock means for locking and unlocking the transmission ratio variable mechanism, wherein the lock means locks the transmission ratio variable mechanism by holding the rotatable member and unlocks the transmission ratio variable mechanism by releasing the rotatable member;

a control means for controlling the electric actuator and for checking whether the unlocking of the transmission ratio variable mechanism is succeeded by rotating the rotatable member through rotation of the electric actuator;

a storage means for storing;

an initial rotational angle of the electric actuator, which is obtained in a locked state of the transmission ratio variable mechanism before the checking of the unlocking of the transmission ratio variable mechanism by the control means; and

initial information, which indicates a magnitude relation between the initial rotational angle of the electric actuator and a threshold angle set in a preset rotational direction before the checking of the unlocking of the transmission ratio variable mechanism by the control means; and

a sensing means for sensing an abnormality of the storage means, wherein the sensing means determines that the storage means is abnormal when a magnitude relation between the initial rotational angle of the electric actuator, which is retrieved from the storage means, and the threshold angle differs from the magnitude relation, which is indicated by the initial information that is retrieved from the storage means.

8. The vehicle steering system according to claim 7, wherein:

the sensing means determines that the storage means is normal when the magnitude relation between the initial rotational angle of the electric actuator, which is retrieved from the storage means, and the threshold angle coincides with the magnitude relation, which is indicated by the initial information that is retrieved from the storage means; and

when the sensing means determines that storage means is normal, the control means unlocks the transmission ratio variable mechanism by controlling the lock means and checks whether the unlocking of the transmission ratio variable mechanism is succeeded by rotating the rotatable member through the rotation of the electric actuator.

9. The vehicle steering system according to claim 7, wherein the electric actuator includes:

an electric motor; and

a speed reducer that reduces a rotational speed of rotation, which is transmitted from the electric motor, and outputs the rotation of the reduced rotational speed.

10. A vehicle steering system comprising:

a transmission ratio variable mechanism that is placed between a steering wheel and steerable vehicle wheels in a vehicle and includes an electric actuator, which is rotated to change a transmission ratio between a steering angle of the steering wheel and a turning angle of the steerable vehicle wheels;

a rotatable member that is rotated synchronously with the electric actuator;

a lock means for locking and unlocking the transmission ratio variable mechanism, wherein the lock means locks the transmission ratio variable mechanism by holding the rotatable member and unlocks the transmission ratio variable mechanism by releasing the rotatable member;

a control means for controlling the electric actuator and for checking whether the unlocking of the transmission ratio variable mechanism is succeeded by rotating the rotatable member through rotation of the electric actuator;

a storage means for storing an initial rotational angle of the electric actuator, which is obtained in a locked state of the transmission ratio variable mechanism before the checking of the unlocking of the transmission ratio variable mechanism by the control means; and

a sensing means for sensing an abnormality of the storage means, wherein the sensing means determines that the storage means is abnormal when the initial rotational angle of the electric actuator, which is retrieved from the storage means, is larger than a threshold angle set in a present rotational direction, wherein when a rotational angle of the electric actuator, which is obtained after the checking of the unlocking of the transmission ratio variable mechanism, differs from the initial rotational angle of the electric actuator, which is retrieved from the storage means, the control means returns the rotational angle of the electric actuator to the initial rotational angle of the electric actuator by rotating the electric actuator.

11. The vehicle steering system according to claim 10, wherein:

the sensing means determines that the storage means is normal when the initial rotational angle of the electric actuator, which is retrieved from the storage means, is not larger than the threshold angle; and

when the sensing means determines that storage means is normal, the control means unlocks the transmission ratio variable mechanism by controlling the lock means and checks whether the unlocking of the transmission ratio variable mechanism is succeeded by rotating the rotatable member through the rotation of the electric actuator.

12. The vehicle steering system according to claim 10, wherein the electric actuator includes:

an electric motor; and

a speed reducer that reduces a rotational speed of rotation, which is transmitted from the electric motor, and outputs the rotation of the reduced rotational speed.

13. A vehicle steering system comprising:

a transmission ratio variable mechanism that is placed between a steering wheel and steerable vehicle wheels in a vehicle and includes an electric actuator, which is rotated to change a transmission ratio between a steering angle of the steering wheel and a turning angle of the steerable vehicle wheels;

a rotatable member that is rotated synchronously with the electric actuator;

a lock means for locking and unlocking the transmission ratio variable mechanism, wherein the lock means locks the transmission ratio variable mechanism by holding the rotatable member and unlocks the transmission ratio variable mechanism by releasing the rotatable member;

a control means for controlling the electric actuator and for checking whether the unlocking of the transmission ratio variable mechanism is succeeded by rotating the rotatable member through rotation of the electric actuator in a preset rotational direction;

a storage means for storing an initial rotational angle of the electric actuator, which is obtained in a locked state of the transmission ratio variable mechanism before the checking of the unlocking of the transmission ratio variable mechanism by the control means; and

a sensing means for sensing an abnormality of the storage means, wherein the sensing means determines that the storage means is abnormal when the initial rotational angle of the electric actuator, which is retrieved from the storage means, is larger than a threshold angle set in the present rotational direction, wherein when a difference between the initial rotational angle of the electric actuator, which is retrieved from the storage means, and the threshold angle, is smaller than an allowable angle, the control means unlocks the transmission ratio variable mechanism by controlling the lock means and checks whether the unlocking of the transmission ratio variable mechanism is succeeded by rotating the rotatable member through rotation of the electric actuator upon reversing the preset rotational direction of the electric actuator.

14. The vehicle steering system according to claim 13, wherein when the difference between the initial rotational angle of the electric actuator, which is retrieved from the storage means, and the threshold angle, is equal to or larger than the allowable angle, the control means unlocks the transmission ratio variable mechanism by controlling the lock means and checks whether the unlocking of the transmission ratio variable mechanism is succeeded by rotating the rotatable member through rotation of the electric actuator while maintaining the preset rotational direction of the electric actuator.

15. The vehicle steering system according to claim 14, wherein when the control means checks whether the unlocking of the transmission ratio variable mechanism is succeeded, the control means rotates the electric actuator by a preset rotational angle, which is smaller than the allowable angle.

16. The vehicle steering system according to claim 13, wherein:

the sensing means determines that the storage means is normal when the initial rotational angle of the electric actuator, which is retrieved from the storage means, is not larger than the threshold angle; and

when the sensing means determines that storage means is normal, the control means unlocks the transmission ratio variable mechanism by controlling the lock means and checks whether the unlocking of the transmission ratio variable mechanism is succeeded.

17. The vehicle steering system according to claim 13, wherein the electric actuator includes:

an electric motor; and

a speed reducer that reduces a rotational speed of rotation, which is transmitted from the electric motor, and outputs the rotation of the reduced rotational speed.