VEHICLE STEERING CONTROL SYSTEM AND CONTROL METHOD THEREFOR

• US 20090276121A1
• Filed: 09/14/2007
• Published: 11/05/2009
• Est. Priority Date: 09/15/2006
• Status: Active Grant

• Current Assignee: Toyota Jidosha Kabushiki Kaisha (Toyota Motor Corporation)
• Original Assignee: Toyota Jidosha Kabushiki Kaisha (Toyota Motor Corporation)
• Inventors: Kojo, Takahiro, Limpibunterng, Theerawat
• Granted Patent: US 8,229,629 B2
• Time in Patent Office: Days
• US Class Current: 701/41
• CPC Class Codes: B62D 5/0463 calculating assisting torque from the motor based on driver input
• CPC Class Codes: B62D 5/0496 by using a temperature sensor

Abstract

A vehicle steering control system that controls the operation of an electric vehicle steering device, which applies a steering assist force to a steering mechanism via a gear mechanism and includes: a temperature estimating section for estimating the temperature of or around the gear mechanism; and a correcting section for correcting the steering assist force according to the estimated gear temperature.

Claims

1. A vehicle steering control system for controlling operation of an electric vehicle steering device which applies a steering assist force to a steering mechanism via a gear mechanism, comprising:

a temperature estimating section for estimating a gear temperature as a temperature of the gear mechanism or around the gear mechanism; and

a correcting section for correcting the steering assist force according to the estimated gear temperature.

2. The vehicle steering control system according to claim 1, wherein the temperature estimating section estimates the gear temperature based on convective heat from the radiator.

3. The vehicle steering control system according to claim 2, wherein the temperature estimating section estimates the gear temperature by estimating an amount of change in the gear temperature caused by convective heat from the radiator based on at least one of an engine speed, the vehicle speed and the coolant temperature as a temperature of cooling water for cooling the internal combustion engine.

4. The vehicle steering control system according to claim 1, wherein the temperature estimating section estimates the gear temperature based on self-heating of an electric motor that applies the steering assist force.

5. The vehicle steering control system according to claim 4, wherein the temperature estimating section estimates the gear temperature by estimating an amount of change in the gear temperature caused by self-heating of the electric motor based on the amount of current supplied to the electric motor.

6. The vehicle steering control system according to claim 1, wherein the temperature estimating section estimates the gear temperature based on radiant heat from the internal combustion engine.

7. The vehicle steering control system according to claim 6, wherein the temperature estimating section estimates the gear temperature by estimating an amount of change in the gear temperature caused by radiant heat from the internal combustion engine based on elapsed time after the start of the internal combustion engine.

8. The vehicle steering control system according to claim 1, wherein the temperature estimating section estimates the gear temperature based on ambient temperature.

9. The vehicle steering control system according to claim 1, wherein the correcting section corrects the steering assist force by adding a low-temperature correcting assist force determined according to the gear temperature to a normal assist force, which is applied when the gear temperature is above a prescribed temperature.

10. The vehicle steering control system according to claim 9, wherein the correcting section corrects the steering assist force by increasing the low-temperature correcting assist force as the gear temperature decreases.

11. The vehicle steering control system according to claim 9, wherein the prescribed value of the gear temperature is a temperature at which the preload of the gear mechanism begins to increase.

13. The vehicle steering control system according to claim 1, wherein the temperature estimating section estimates the gear temperature based on at least one of an engine speed, the vehicle speed and the coolant temperature as a temperature of cooling water for cooling the internal combustion engine.

14. The vehicle steering control system according to claim 1, wherein the temperature estimating section estimates the gear temperature based on elapsed time after the start of the internal combustion engine.

12. A method for controlling a vehicle steering control system for controlling operation of an electric vehicle steering device, which applies a steering assist force to a steering mechanism via a gear mechanism, comprising:

estimating a gear temperature as a temperature of or around the gear mechanism; and

correcting the steering assist force according to the estimated gear temperature.

15. A vehicle steering control system for controlling operation of an electric vehicle steering device which applies a steering assist force to a steering mechanism via a gear mechanism, comprising:

a temperature estimating section for estimating a gear temperature as a temperature of the gear mechanism or around the gear mechanism based on a difference between a temperature of a control unit that controls the operation of the vehicle steering device and an ambient temperature; and

a correcting section for correcting the steering assist force according to the estimated gear temperature.

16. The vehicle steering control system according to claim 15, wherein the temperature estimating section estimates that the gear temperature is equal to the gear temperature that is last estimated while an internal combustion engine is previously being driven, in a case where the ambient temperature at a time when the internal combustion engine is started is equal to the ambient temperature that is last detected while the internal combustion engine is previously being driven, and the temperature of the control unit at the time when the internal combustion engine is started is higher than the temperature of the control unit that is last detected while the internal combustion engine is previously being driven.

17. The vehicle steering control system according to claim 15, wherein the temperature estimating section estimates that the gear temperature is equal to the ambient temperature at a time when the internal combustion engine is started, or the temperature of the control unit at the time when the internal combustion engine is started, in a case where an absolute value of a difference between the ambient temperature at the time when the internal combustion engine is started and the temperature of the control unit at the time when the internal combustion engine is started is smaller than a prescribed threshold.

18. The vehicle steering control system according to claim 15, wherein the temperature estimating section estimates that the gear temperature is equal to a value obtained by an equation, the ambient temperature at a time when the internal combustion engine is started+{(the temperature of the control unit at the time when the internal combustion engine is started−

the ambient temperature at the time when the internal combustion engine is started)/(the temperature of the control unit that is last detected while the internal combustion engine is previously being driven−

the ambient temperature that is last detected while the internal combustion engine is previously being driven)×

(the gear temperature that is last estimated while the internal combustion engine is previously being driven−

the ambient temperature that is last detected while the internal combustion engine is previously being driven)}, in a case where an absolute value of a difference between the ambient temperature at the time when the internal combustion engine is started and the temperature of the control unit at the time when the internal combustion engine is started is equal to or larger than a prescribed threshold.

19. The vehicle steering control system according to claim 16, wherein the temperature estimating section corrects the estimated gear temperature based on convective heat from a radiator.

20. The vehicle steering control system according to claim 19, wherein the temperature estimating section corrects the estimated gear temperature by estimating an amount of change in the gear temperature caused by the convective heat from the radiator based on at least one of an engine speed, a vehicle speed and a coolant temperature as a temperature of cooling water for cooling the internal combustion engine.

21. The vehicle steering control system according to claim 16, wherein the temperature estimating section corrects the estimated gear temperature based on self-heating of an electric motor that applies the steering assist force.

22. The vehicle steering control system according to claim 21, wherein the temperature estimating section corrects the estimated gear temperature by estimating an amount of change in the gear temperature caused by self-heating of the electric motor based on an amount of current supplied to the electric motor.

23. The vehicle steering control system according to claim 16, wherein the temperature estimating section corrects the estimated gear temperature based on radiant heat from the internal combustion engine.

24. The vehicle steering control system according to claim 23, wherein the temperature estimating section corrects the estimated gear temperature by estimating an amount of change in the gear temperature caused by the radiant heat from the internal combustion engine based on elapsed time after start of the internal combustion engine.

25. The vehicle steering control system according to claim 15, wherein the correcting section corrects the steering assist force by adding a low-temperature correcting assist force determined according to the gear temperature to a normal assist force, which is applied when the gear temperature is above a prescribed temperature.

26. The vehicle steering control system according to claim 25, wherein the correcting section corrects the steering assist force by increasing the low-temperature correcting assist force as the gear temperature decreases.