| 摘要 |
PURPOSE:To control torque to be constant with one control valve and without using any mechanical feedback mechanism, and improve fine operability of an actuator. CONSTITUTION:A control valve 30 to supply pump discharge pressure to the large diameter pressure receiving chamber 28 of a variable capacity cylinder 25 is switched to the pressure oil supply position B or to the drain position A by pressure difference between the upper stream side pressure of the restriction 43 provided in the discharge passage 21 of a variable capacity type hydraulic pump 20 and the output side pressure of a direction control valve 22 and pressure difference PC across the restriction 35 provided in the discharge passage 34 of a fixed pump 33 and whose passing flow is controlled by the pump discharge pressure. Flow variation of the variable capacity type hydraulic pump 20 is fed back as a pressure difference between the upper stream side pressure of the restriction 43 and the output side pressure of the direction control valve 22, and rotating speed variation is fed back as a pressure difference across the restriction 35. |
