Patent ID: 7044262

Claim:
A power steering system comprising: a steering shaft operatively associated with a steering mechanism; a power cylinder that has a pair of hydraulic chambers for boosting a steering torque of the steering mechanism; a first oil passage hydraulically connected to one of the hydraulic chambers of the power cylinder; a second oil passage hydraulically connected to another of the hydraulic chambers of the power cylinder; a reversible pump having an oil outlet hydraulically connected to the first oil passage and another oil outlet hydraulically connected to the second oil passage; a drive unit that drives the reversible pump; a control unit that outputs a drive signal to the drive unit, based on a steered state of the steering shaft; a bypass passage that hydraulically connects the first oil passage to the second oil passage; a switching valve provided in the bypass passage, for switching between an open state and a closed state of the bypass passage; an oil reservoir that stores hydraulic fluid; a first communicating passage that communicates the bypass passage and the oil reservoir via the switching valve to each other; a first oil supply passage that communicates the oil reservoir and the first oil passage to each other; a first check valve provided in the first oil supply passage, for allowing one-way supply from the oil reservoir to the first oil passage; a second oil supply passage that communicates the oil reservoir and the second oil passage to each other; and a second check valve provided in the second oil supply passage, for allowing one-way supply from the oil reservoir to the second oil passage.