To provide an actuator which achieves down-sizing of a motor pump and reduction in cost by imparting an assisting force provided by an oil pump to a rotation drive motion of the motor pump.
The actuator comprises a hydraulic drive mechanism 21 which outputs a driving force to a compression ratio adjustable device by means of the pressure of oil which is charged to or discharged from a pair of the first working chamber 28 and the second working chamber 29, and a motor-driven pump 22 which is driven by a reversible rotation electric motor 36 to selectively charge the oil pressure to or discharge it from the first working chamber and the second working chamber via oil paths 33 and 34. In addition, the actuator is provided an electromagnetic direction control valve 25 which imparts a drive assisting force to the electric motor by means of the oil pressure supplied from the oil pump 23 driven by an internal combustion engine to the hydraulic motor 24, and controls the working direction of the rotation force of the hydraulic motor and the amount of supply of an oil pressure from the oil pump to the hydraulic motor.
NAKAMURA MAKOTO
Hiromichi Kobayashi
Tomioka Kiyoshi
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