| 摘要 |
An actuator comprises a driving section driven and rotated by a supplied current, a pump mechanism driven by a driving force supplied from the driving section to suck and discharge pressure oil, and a cylinder mechanism having a piston displaceable by the pressure oil supplied from the pump mechanism. When a pressure of the pressure oil is at or greater than a predetermined value in the cylinder mechanism, a relief valve provided in the pump mechanism is opened to thereby discharge the pressure oil into a pressure oil-charging chamber of the pump mechanism. Pressure within a first or second cylinder chamber of the cylinder mechanism and into which the pressure oil is introduced is maintained substantially constant.
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