PURPOSE: To enable control with high speed and high accuracy by communicating a pressure chamber with a pump port and a tank port according to a spool displacing direction, and communicating an actuator port with the pump port and the tank port according to displacement of an amplifying sleeve of a proportional solenoid valve.
CONSTITUTION: A control signal is output to a proportional solenoid valve 4 according to deviation between a target value and a detected value of a push-out volume of a hydraulic pump 1. A solenoid 4c makes a spool 4b displace in one direction in respect to an amplifying sleeve 4e. One of the pressure sleeves SL, SR is communicated with a pump port Pa, while the other is communicated with tank ports R1, R2. The amplifying sleeve 4e is moved in the same direction of the spool 4b. The amplifying sleeve 4e is displaced in one direction in respect to a casing 4a. An actuator port T of the proportional control valve 4 is communicated with the pump port Pa. Pressure oil is introduced into a large diameter side pressure chamber 2c of a differential cylinder 2, for moving a push-out variable volume mechanism 1a. A discharge flow rate can be controlled with high speed and high accuracy.
NAKAMURA SHIGETAKA
YUASA KAZUMASA
MOTOSAWA YUKIHIRO
SAKAIRI TETSUYA
GOTO YASUHARU
KOKUBU HARUO
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