DRIVING CIRCUIT OF HYDRAULIC OPERATION MACHINE

Japanese Patent JP3037828

B2

PURPOSE: To make good composite drive of both system by providing a variable differential pressure compensating valve to a directional control valve belonging to a high pressure hydraulic pump, providing a constant differential pressure compensating valve to a directional control valve belonging to low pressure pump, and connecting both systems selectively through a control valve.
CONSTITUTION: For example, when traveling is separately controlled, pressure oil for a variable capacity hydraulic pump 30a is supplied to a left traveling directional control valve 5 and a variable differential pressure compensating valve 20e, and pressure oil for a hydraulic pump 30b is supplied to a right traveling directional control valve 6 and a variable differential pressure compensating valve 20f to separately travel. At that time, the maximum load pressure of a left traveling motor is applied to the variable differential pressure compensating valve 20e and a differential pressure detector 32a, and flow rate of the pump 30a is so controlled that discharge pressure of the pump 30a is higher than the maximum load pressure by ΔPLS. Flow rate of the pump 30 is controlled by the compensating valve 20f and a differential pressure detector 32b even in the case of a right traveling motor. According to the constitution, in the case of composite drive of both systems, better driving can be made without requiring any adjustment of metering.

Ken Ichiyanagi
Masami Ochiai
Touichi Hirata

JP15962692A

May 08, 2000

June 18, 1992

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Hitachi Construction Machinery Co., Ltd.

E02F9/22; (IPC1-7): E02F9/22

JP384204A
JP2279839A
JP2291435A
JP419409A

Kenjiro Take

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