Power steering apparatus

• US 7,051,834 B2
• Filed: 07/29/2005
• Issued: 05/30/2006
• Est. Priority Date: 08/06/2001
• Status: Expired due to Fees

• Current Assignee: Koyo Seiko Co., Ltd. (Toyota Motor Corporation)
• Original Assignee: Koyo Seiko Co., Ltd. (Toyota Motor Corporation)
• Inventors: Fujita, Kazuhiko
• Primary Examiner(s): Morris, Lesley D.
• Assistant Examiner(s): ARCE, MARLON ALEXANDER
• Application Number:
  US11/191,998
• Publication Number:
  US 20050257994A1
• Time in Patent Office: 305 Days
• Field of Search: 180/446, 180/443
• 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

In a power steering apparatus, a basic-target-rotational-speed setting portion 42 sets a basic target rotational speed Rb of an electric motor 27 on the basis of the vehicle speed and the angular velocity of steering. A temperature-coefficient setting portion 43 sets a temperature coefficient a which becomes smaller with an increase in the temperature. A target-rotational-speed setting portion 44 sets a target rotational speed R of the electric motor 27 on the basis of the formula R=α·Rb. A motor-drive control portion 45 controls a drive circuit 28 so that this target rotational speed R will be attained.

Claims

1. A power steering apparatus for generating a steering assisting force by hydraulic pressure generated by a pump driven by an electric motor, the apparatus comprising:

steering detecting means for detecting the steering by an operation member for steering;

driving-target-basic-value setting means for setting a driving target basic value for driving said electric motor on the basis of an output signal of said steering detecting means;

temperature detecting means for detecting a temperature of said electric motor;

temperature-coefficient setting means for setting a temperature coefficient, which becomes smaller as the temperature of said electric motor becomes higher, on the basis of an output of said temperature detecting means;

driving-target-value setting means for setting a driving target value for driving said electric motor by multiplying the driving target basic value set by said driving-target-basic-value setting means by the temperature coefficient set by said temperature-coefficient setting means;

motor driving means for driving said electric motor on the basis of the driving target value set by said driving-target-value setting means; and

steering-direction detecting means for detecting whether the steering by said operation member comprises steering-wheel-turning steering, which is steering in a direction away from a midpoint of a steering angle, or steering-wheel-returning steering, which is steering in a direction toward the midpoint of the steering angle,

wherein said driving-target-basic-value setting means sets the driving target basic value corresponding to the angular velocity of steering such that the driving target basic value at the time of steering-wheel-turning steering becomes larger than the driving target basic value at the time of steering-wheel-returning steering.

2. A method of controlling an electric motor driving a hydraulic pump generating a steering assisting force in a power steering apparatus, the method comprising:

detecting the steering by an operation member for steering, and generating an output signal indicative of the detected steering;

setting a driving target basic value for driving said electric motor on the basis of the output signal indicative of the detected steering;

detecting a temperature of said electric motor and generating an output signal indicative of the detected temperature;

setting a temperature coefficient, which becomes smaller as the temperature of said electric motor becomes higher, on the basis of the output signal indicative of the detected temperature;

setting a driving target value for driving said electric motor by multiplying the driving target basic value by the temperature coefficient;

driving said electric motor on the basis of the driving target value; and

detecting whether the steering by said operation member comprises steering-wheel-turning steering, which is steering in a direction away from a midpoint of a steering angle, or steering-wheel-returning steering, which is steering in a direction toward the midpoint of the steering angle,

wherein the driving target basic value corresponding to the angular velocity of steering is set such that the driving target basic value at the time of steering-wheel-turning steering becomes larger than the driving target basic value at the time of steering-wheel-returning steering.