Power steering apparatus

• US 6,945,351 B2
• Filed: 08/02/2002
• Issued: 09/20/2005
• 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): DePumpo, Daniel G.
• Application Number:
  US10/210,080
• Publication Number:
  US 20030024758A1
• Time in Patent Office: 1,145 Days
• Field of Search: 180/443, 180/444, 180/446, 180/422, 180/417, 180/403, 701/41, 701/42
• US Class Current: 180/422
• 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 α 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-angular-velocity calculating means for calculating the angular velocity of steering by an operation member for steering;

steering-angular-acceleration calculating means for calculating the angular acceleration of steering based upon said calculated angular velocity of said steering by an operation by said operation member;

driving-target-basic-value setting means for setting a driving target basic rotational speed value for driving said electric motor on the basis of an output signal of said steering-angular-velocity calculating means;

correction-value setting means for setting a correction rotational speed value for correcting the driving target basic rotational speed value, wherein the correction value is directly proportional to an output of said steering-angular-acceleration calculating means when the output is close to zero and when the output is not close to zero;

driving-target-value setting means for setting a driving target rotational speed value for driving said electric motor by correcting the driving target basic rotational speed value set by said driving-target-basic-value setting means by the correction rotational speed value set by said correction-value setting means; and

motor driving means for driving said electric motor on the basis of the driving target rotational speed value set by said driving-target-value setting means.

2. The apparatus of claim 1, wherein said angular acceleration of steering is based upon a time differentiation of said calculated angular velocity of said steering.

3. The apparatus of claim 1, wherein said driving-target-value setting means adds said correction rotational speed value to said driving target basic rotational speed value to provide said driving target rotational speed value.

5. The method of claim 2, wherein said angular acceleration of steering is based upon a time differentiation of said calculated angular velocity of said steering.

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

calculating the angular velocity of steering by an operation member for steering and generating an output signal indicative of the calculated angular velocity;

calculating the angular acceleration of steering based upon said calculated angular velocity of said steering by an operation by said operation member and generating an output signal indicative of the calculated angular acceleration;

setting a driving target basic rotational speed value for driving said electric motor on the basis of the output signal indicative of the calculated angular velocity;

setting a correction rotational speed value for correcting the driving target basic rotational speed value, wherein the correction rotational speed value is directly proportional to the output signal indicative of the calculated angular acceleration when the output signal is close to zero and when the output signal, which is indicative of the calculated angular acceleration, is not close to zero;

setting a driving target rotational speed value for driving said electric motor by correcting the driving target basic rotational speed value by the correction rotational speed value; and

driving said electric motor on the basis of the driving target rotational speed value.

6. The method of claim 4, wherein setting said driving target rotational speed value comprises adding said correction rotational speed value to said driving target basic rotational speed value.

7. A power steering apparatus comprising:

a steering angle sensor that outputs a steering angle signal that indicates a steering angle;

a steering angle velocity calculator that outputs a steering angle velocity signal based upon the steering angle signal;

a steering angle acceleration calculator that outputs a steering angle acceleration signal based upon a time differentiation of said steering angle velocity signal;

a basic target rotational speed value setter that sets a basic target rotational speed value that is based upon the steering angle velocity signal;

a corrector that outputs a corrected rotational speed signal that is directly proportional to the steering angle acceleration signal when the steering angle acceleration signal is close to zero and when the steering angle acceleration signal is not close to zero; and

a target rotational speed setter that sets a target rotational speed based upon the basic target rotational speed value and the corrected rotational speed signal.

8. The apparatus of claim 7, further comprising a motor driver that outputs a motor drive signal based upon the target rotational speed.

9. The apparatus of claim 7, wherein said target rotational speed setter adds said basic target rotational speed value and said corrected rotational speed signal to set said target rotational speed.

10. A method for controlling a power steering apparatus, the method comprising:

generating a steering angle signal that indicates a steering angle;

calculating a steering angle velocity signal based upon the steering angle signal;

calculating a steering angle acceleration signal based upon a time differentiation of said steering angle velocity signal;

setting a basic target rotational speed value based upon the steering angle velocity signal;

calculating a rotational speed correction signal that is directly proportional to the steering angle acceleration signal when the steering angle acceleration signal is close to zero and when the steering angle acceleration signal is not close to zero; and

setting a target rotational speed based upon the basic target rotational speed value and the rotational speed correction signal.

11. The method of claim 10, further comprising outputting a motor drive signal based upon the target rotational speed.