Patent ID: 8776513

Claim:
A fluid-pressure actuator unit comprising: an electric motor; a fluid-pressure pump comprising a discharge port and a suction port, which is driven by the electric motor to pressurize a working fluid suctioned via the suction port and discharge the working fluid into the discharge port in a pressurized state; a fluid pressure cylinder; a discharge passage through which the working fluid discharged into the discharge port is supplied to the fluid pressure cylinder to operate the fluid pressure cylinder; a tank from which the working fluid is supplied to the suction port; a discharge flow restrictor disposed in the discharge passage; a pilot-pressure-operated shut-off valve that assumes a connecting position at which the discharge passage between the discharge flow restrictor and the fluid-pressure cylinder is connected to the tank and a shut-off position at which the discharge passage is disconnected from the tank, with the connecting position or the shut-off position selected in response to a pressure in the discharge passage between the discharge flow restrictor and the discharge port, a recirculation passage that connects the discharge passage between the discharge flow restrictor and the fluid-pressure cylinder to the tank via the pilot-pressure-operated shut-off valve in the connecting position; and a recirculation flow restrictor disposed in the recirculation passage between the pilot-pressure-operated shut-off valve and the tank, wherein the pilot-pressure-operated shut-off valve is configured to selectively assume the connecting position or the shut-off position in accordance with a differential pressure between a pressure in the discharge passage between the discharge flow restrictor and the discharge port and a pressure in the recirculation passage between the pilot-pressure-operated shut-off valve and the recirculation flow restrictor.