Patent ID: 7325645

Claim:
A power steering device for a motor vehicle, comprising: a steering mechanism including a steering wheel; a hydraulic power mechanism for assisting operation of said steering mechanism in accordance with movement of said steering wheel, said hydraulic power mechanism including a power cylinder, a piston slidably disposed in said power cylinder to divide an interior of said power cylinder into first and second work chambers and a transmission mechanism for transmitting movement of said piston to said steering mechanism to assist the steering mechanism; a reversible hydraulic pump having a first outletlinlet port and a second outlet/inlet port; a first fluid passage extending from said first outlet/inlet port to said first work chamber; a second fluid passage extending from said second outlet/inlet port to said second work chamber; a switch system for switching the role of said first and second outlet/inlet ports in accordance with a turning direction of said steering wheel; a couple of first flow control valves respectively incorporated with said first and second fluid passages such that fluid connection between the first outlet/inlet port to the first work chamber is accomplished through one of said first flow control valves and fluid connection between the second outlet/inlet port to said second work chamber is accomplished through the other of said first flow control valves, the one of said first flow control valves selectively fluidly connecting and disconnecting said first fluid passage and a reservoir tank in accordance with a magnitude of a hydraulic pressure produced by said hydraulic pump, and fluidly connecting said first fluid passage and said reservoir tank when said hydraulic pump is under inoperative condition, the other of said first flow control valves selectively fluidly connecting and disconnecting said second fluid passage and said reservoir tank in accordance with the magnitude of a hydraulic pressure produced by said hydraulic pump, and fluidly connecting said second fluid passage and said reservoir tank when said hydraulic pump is under inoperative condition; and a flow control arrangement arranged between said first and second fluid passages, said flow control arrangement permitting a flow of residual pressure in one of said first and second work chambers toward the other of said first and second work chambers when said hydraulic pump is under inoperative condition.