Patent ID: 8392067

Claim:
A power steering device comprising: an oil-hydraulic pump, an electric motor arranged and configured to drive the oil-hydraulic pump, an inverter arranged and configured to output a drive signal to the electric motor, a control valve arranged and configured to switch passages for oil supplied from the oil-hydraulic pump, a power cylinder arranged and configured to produce a steering assist force by a piston driven by oil supplied from the oil-hydraulic pump through the control valve, and a control unit configured to control the drive signal of the inverter, the control valve including a pump port supplied with oil from the oil-hydraulic pump, a first cylinder port connected to a first cylinder chamber on one side of the piston, a second cylinder port connected to a second cylinder chamber on the other side of the piston, and a discharge port, communication between the first cylinder port and the pump port and communication between the second cylinder port and the discharge port being established in steered status in one direction, and communication between the first cylinder port and the discharge port and communication between the second cylinder port and the pump port being established in steered status in another direction, communication among the pump port, the first cylinder port and the second cylinder port being established when the control valve is in neutral status, and isolation of the discharge port from the pump port and the first and second cylinder ports being established when the control valve is in neutral status.