Patent ID: 6390228
Filing Date: 2002-05-21
Classification: B62D,Y10T

Abstract:
A hydraulic power steering apparatus for a vehicle comprising:an input member interlocking with a steering wheel; an output member connected to said input member so as to move relatively freely; a steering mechanism steering a wheel in an interlocking relationship with said output member; a main control valve having a first valve portion and a second valve portion in which a valve opening degree is controlled on the basis of a relative movement between said input member and said output member; a power cylinder mechanism generating a steering assist force applied to said steering mechanism in correspondence to a fluid pressure in a working chamber in which a working fluid is supplied and discharged; a first flow passage communicating a pump apparatus for discharging a fixed flow amount of working fluid with said main control valve; a second flow passage branched from said first flow passage and communicated with a low pressure portion via an assist control valve and said main control valve; a control unit controlling said assist control valve; said first valve portion controlling a supply amount of the working fluid in said first flow passage to said working chamber; and said second valve portion controlling a discharge amount of the working fluid in said second flow passage to said low pressure portion in accordance with cooperation with said assist control valve, wherein a vehicle speed sensor for detecting a vehicle speed and a pressure sensor for detecting a fluid pressure of the working fluid in said first flow passage are provided, and said control unit controls a valve opening degree of said assist control valve to a set valve opening degree set on the basis of the vehicle speed detected by said vehicle speed sensor and the fluid pressure detected by said pressure sensor.