Patent ID: 6880668

Claim:
A power steering device for a motor vehicle, comprising: a steering wheel adapted to be connected to a couple of steered road wheels; a power cylinder; a piston slidably disposed in said power cylinder to divide the interior of said power cylinder into first and second work chambers; a transmission mechanism for transmitting movement of said piston to said couple of steered road wheels; a reversible hydraulic pump having a first outlet/inlet port and a second outlet/inlet port; an electric motor reversibly driving said reversible hydraulic pump in accordance with a turning direction of said steering wheel; 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 first valve arranged in each of said first and second fluid passages, said first valve being constructed to permit a fluid flow from said reversible hydraulic pump toward said power cylinder when a hydraulic pressure produced by said hydraulic pump is larger than that in the corresponding work chamber by a given pressure; and a second valve arranged in each of said first and second fluid passages in parallel with said first valve, said second valve being constructed to permit only a fluid flow from one of the first and second work chambers toward said reversible hydraulic pump, wherein an opening pressure of said first valve is set higher than the lowest level of a pulse fluctuation range of the hydraulic pressure from said reversible hydraulic pump.