Patent ID: 8479870

Claim:
A power steering system comprising: a power cylinder equipped with a pair of pressure chambers to provide a steering force for at least one of steered wheels on a basis of a pressure difference between the pair of pressure cylinders; a steering mechanism configured to turn the steered wheel in accordance with a rotational steering operation of a steering wheel; a first pump equipped with a first drive shaft to suck and drain a working liquid along with a revolution of the first drive shaft to supply the working liquid to the power cylinder, the first pump being rotationally driven by means of a first driving source; a second pump equipped with a second drive shaft to suck and drain the working liquid along with the revolution of the second drive shaft to supply the working liquid to the power cylinder; a second driving source which is a driving source different from the first driving source, is constituted by an electric motor, and rotationally drives the second pump; a control valve disposed in the steering mechanism to selectably supply the working liquid supplied from the first pump or second pump to the pair of pressure chambers in accordance with a rotational steering operation of the steering wheel; a first switching valve disposed between the first pump and the control valve to switch a communication and an interruption of the working liquid between the first pump and the control valve; and a second switching valve disposed between the second pump and the control valve to switch the communication and the interruption of the working liquid between the second pump and the control valve, a communication state and an interruption state being selectably formed in the second switching valve when the first switching valve is in the communication state.