Patent ID: 6851507

Claim:
A power steering system for controlling a steering of a wheel, comprising: a) an oil pressure cylinder including: i) a first oil pressure chamber, ii) a second oil pressure chamber, and iii) a piston partitioning the oil pressure cylinder into the first oil pressure chamber and the second oil pressure chamber; b) an oil passage including: a first oil passage connected to the first oil pressure chamber, for a supply and a drainage of an oil pressure, and a second oil passage connected to the second oil pressure chamber, for the supply and the drainage of the oil pressure; c) a reversible oil pump, in accordance with an input torque outputted from a steering input mechanism, supplying the oil pressure to one of the first oil pressure chamber and the second oil pressure chamber while draining the oil pressure from the other of the first oil pressure chamber and the second oil pressure chamber, thus controlling the steering of the wheel; d) a drain passage including: i) a first drain passage for draining the oil pressure from the first oil passage, and ii) a second drain passage for draining the oil pressure from the second oil passage; e) a reservoir connected to the first drain passage and the second drain passage, the reservoir reserving the oil pressure drained from the first oil passage and the second oil passage respectively through the first drain passage and the second drain passage; and f) a switch valve including: i) a first switch valve connected to the first drain passage, and ii) a second switch valve connected to the second drain passage, when one of the first oil passage and the second oil passage is so pressurized by an operation of the reversible oil pump as to have an increased internal pressure, a pair of the first switch valve and the second switch valve allowing the following: i) closing one of the first drain passage and the second drain passage which one is connected to the oil passage having the thus increased internal pressure, while ii) opening the other of the first drain passage and the second drain passage which other is connected to the oil passage that is so depressurized as to have a decreased internal pressure.