Patent ID: 6953102

Claim:
A power steering system comprising: a steering input mechanism connected to steerable wheels; an oil pressure cylinder operable to apply a steering assist force to the steering input mechanism and having a first oil pressure chamber and a second oil pressure chamber; a reversible pump having a pair of outlets; a first oil passage connecting between the first oil pressure chamber and one of the outlets of the reversible pump; a second oil passage connecting between the second oil pressure chamber and the other of the outlets of the reversible pump; a torque sensor for detecting a steering torque of the steering input mechanism; a motor connected to the reversible pump for driving the reversible pump in a normal direction and a reverse direction on the basis of the steering torque; a reservoir for reserving working oil; a first drain passage connecting between the first oil passage and the reservoir; a second drain passage connecting between the second oil passage and the reservoir; a first switch valve disposed in the first drain passage for selectively opening and closing and the first drain passage; a second switch valve disposed in the second drain passage for selectively opening and closing the second drain passage; a first compensator passage connecting between the first oil passage and the reservoir; a first check valve disposed in the first compensator passage for allowing flow of working oil only from the reservoir to the first passage; a second compensator passage connecting between the second oil passage and the reservoir; and a second check valve disposed in the second compensator passage for allowing flow of working oil only from the reservoir to the second passage.