Power steering apparatus

• US 6,334,502 B1
• Filed: 03/31/2000
• Issued: 01/01/2002
• Est. Priority Date: 04/07/1999
• Status: Expired due to Term

• Current Assignee: Koyo Seiko Co., Ltd. (Toyota Motor Corporation)
• Original Assignee: Koyo Seiko Co., Ltd. (Toyota Motor Corporation)
• Inventors: Tsujimoto, Taisuke
• Primary Examiner(s): Swann, J. J.
• Assistant Examiner(s): LUM VANNUCCI, LEE SIN YEE
• Application Number:
  US09/540,522
• Time in Patent Office: 641 Days
• Field of Search: 180/446, 180/421, 180/422, 701/41
• US Class Current: 180/446
• CPC Class Codes: B62D 5/065 characterised by specially adapted means for varying pressurised fluid supply based on need, e.g. on-demand, variable assist

Abstract

Disclosed is a power steering apparatus using an electric motor as a drive source. The power steering apparatus includes a drive inhibiting circuit for inhibiting an electric motor from being driven when the temperature detected by a temperature sensor is not less than an upper-limit temperature, a judging circuit for judging, in a state where the electric motor is inhibited from being driven by the drive inhibiting circuit, whether or not the steering angle is included in a predetermined steering angle midpoint range when the temperature sensor detects a temperature which is not more than a lower-limit temperature, and a re-drive allowing circuit for allowing, when it is judged that the steering angle is within the steering angle midpoint range, the electric motor to be driven again.

Claims

1. A power steering apparatus using an electric motor as a drive source, comprising:

a temperature detection section for detecting a temperature in a predetermined portion;

a steering angle detection section for outputting steering angle data corresponding to a steering angle;

a drive inhibiting circuit for inhibiting the electric motor from being driven when the temperature detected by the temperature detection section is not less than a predetermined upper-limit temperature;

a judging circuit for judging, in a state where the electric motor is inhibited from being driven by the drive inhibiting circuit, whether or not the steering angle is included in a predetermined steering angle midpoint range on the basis of the steering angle data from the steering angle detection section when the temperature detected by the temperature detection section is lowered to not more than a predetermined lower-limit temperature; and

a re-drive allowing circuit for allowing, when the judging circuit judges that the steering angle is within the steering angle midpoint range, the electric motor to be driven again.

2. The power steering apparatus according to claim 1, wherein

the power steering apparatus produces a steering assist force for assisting in steering by oil pressure created by a pump driven by the electric motor.

3. The power steering apparatus according to claim 1, wherein

the predetermined portion is a portion in which the temperature changes depending on how the electric motor is energized.

4. The power steering apparatus according to claim 1, wherein

the predetermined portion is the inside of a control unit for controlling the drive of the electric motor.

5. The power steering apparatus according to claim 1, further comprising

a maximum motor rotational speed setting circuit for controlling, when the temperature detected by the temperature detection section takes an intermediate value between the upper-limit temperature and the lower-limit temperature, the maximum rotational speed of the electric motor to an intermediate rotational speed between a predetermined maximum value and a predetermined minimum value depending on the detected temperature.

6. A system for controlling an electric motor in a power steering apparatus for a vehicle, the comprising:

means for providing steering angle data corresponding to a steering angle of the vehicle; and

a control unit controlling operation of the electric motor, including

means for detecting a temperature of the control unit,

means for driving the electric motor,

means, responsive to detection by the temperature detecting means of a control unit temperature not less than a predetermined upper-limit temperature value, for inhibiting the driving means from driving the electric motor,

means, responsive to detection by the temperature detecting means of a reduction in the control unit temperature to not more than a predetermined lower-limit temperature value, while the inhibiting means is inhibiting the driving, means from driving the electric motor, for judging whether or not the steering angle is included in a predetermined steering angle midpoint range on the basis of the steering angle data provided by the steering angle data providing means, and

means, responsive to a judgment by the judging means that the steering angle is within the steering angle midpoint range, for discontinuing the inhibiting of the driving means by the inhibiting means.

7. The system according to claim 6, wherein the power steering apparatus produces a steering assist force for assisting in steering by oil pressure created by a pump driven by the electric motor.

8. The system according to claim 6, wherein the temperature in the control unit changes depending on how the electric motor is energized.

9. The system according to claim 6, further comprising means for controlling the maximum rotational speed of the electric motor to an intermediate rotational speed between a predetermined maximum value and a predetermined minimum value depending on the detected temperature, when the temperature detected by the temperature detecting means takes an intermediate value between the upper-limit temperature value and the lower-limit temperature value.

10. A power steering system for a vehicles the comprising:

a hydraulic pump for providing a steering assist force for assisting in steering of the vehicle;

an electric motor for driving the pump;

means for providing steering angle data corresponding to a steering angle of the vehicle; and

a control unit controlling operation of the electric motor, including

means for detecting a temperature of the control unit that changes depending on how the electric motor is energized,

means for driving the electric motor,

means, responsive to detection by the temperature detecting means of a control unit temperature not less than a predetermined upper-limit temperature value, for inhibiting the driving means from driving the electric motor,

means, responsive to detection by the temperature detecting means of a reduction in the control unit temperature to not more than a predetermined lower-limit temperature value, while the inhibiting means is inhibiting the driving means from driving the electric motor, for judging whether or not the steering angle is included in a predetermined steering angle midpoint range on the basis of the steering angle data provided by the steering angle data providing means, and

means, responsive to a judgment by the judging means that the steering angle is within the steering angle midpoint range, for discontinuing the inhibiting of the driving means by the inhibiting means.

11. The system according to claim 10, further comprising means for controlling the maximum rotational speed of the electric motor to an intermediate rotational speed between a predetermined maximum value and a predetermined minimum value depending on the detected temperature, when the temperature detected by the temperature detecting means takes an intermediate value between the upper-limit temperature value and the lower-limit temperature value.

12. A system for controlling an electric motor in a power steering apparatus for a vehicle, the comprising;

means for providing steering angle data corresponding to a steering angle of the vehicle; and

a control unit controlling operation of the electric motor, including

means for detecting a temperature of the control unit,

means for driving the electric motor,

means, responsive to detection by the temperature detecting means of a control unit temperature not less than a predetermined upper-limit temperature value, for inhibiting the driving means from driving the electric motor,

means, responsive to detection by the temperature detecting means of a reduction in the control unit temperature to not more than a predetermined lower-limit temperature value, while the inhibiting means is inhibiting the driving means from driving the electric motor, for judging whether or not the steering angle is included in a predetermined steering angle midpoint range on the basis of the steering angle data provided by the steering angle data providing means, and

means, responsive to a judgment by the judging means that the steering angle is within the steering angle midpoint range while the inhibiting means is inhibiting the driving means from driving the electric motor, for discontinuing the inhibiting of the driving means by the inhibiting means, the inhibiting means, once responding to the detection of a control unit temperature not less than a predetermined upper-limit temperature value to inhibit the driving, means from driving the electric motor, continuing to inhibit the driving means from driving the electric motor until the discontinuing means responds to the judgment by the judging means to discontinue the inhibiting.

13. The system according to claim 12, further comprising means for controlling the maximum rotational speed of the electric motor to an intermediate rotational speed between a predetermined maximum value and a predetermined minimum value depending on the detected temperature when the temperature detected by the temperature detecting means takes an intermediate value between the upper-limit temperature value and the lower-limit temperature value.