PURPOSE: To reduce the occurrence of electrical processing for control of a proportional solenoid valve, to reduce the occurrence of a failure in operation, and to improve reliability by providing constitution wherein mechanical feedback of displacement of a servo piston is performed by using a feedback sleeve linked to a servo piston.
CONSTITUTION: A differential cylinder having a servo piston 2a having two ends the pressure receiving areas of which are different from each other is used as the regulation actuator 2 of the displacement volume varying mechanism 1a of a hydraulic pump 1 and the chamber 2b on the small side of the differential cylinder is communicated with a hydraulic source 3. Meanwhile, a chamber 2c on the large side is connected to the hydraulic source 3 through a proportional solenoid valve 4. A three-port proportional solenoid valve is used as the proportional valve 4, a feedback sleeve 7 is located between P, R, and T and the see 7, and the sleeve 7 is coupled to a servo piston 2a through a link 8 for interlocking. A control current responding to the target value of a pump delivery flow rate is outputted to a solenoid 4c by a control part 5.
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GOTO YASUHARU
NAKAMURA SHIGETAKA
YUASA KAZUMASA
MOTOSAWA YUKIHIRO
SAKAIRI TETSUYA
