HYDRAULIC CONTROL DEVICE OF CONSTRUCTION MACHINE

摘要

PROBLEM TO BE SOLVED: To provide a hydraulic control device of a construction machine capable of effectively relieving a shock during the starting while well maintaining the operability. SOLUTION: This hydraulic control device of a construction machine comprises a control valve 16 interposed between a hydraulic pump 10 and a hydraulic actuator 12 for opening and closing a meter-in control flow path, and a flow rate control valve 18 interposed between a pump discharge line 24 on the upstream side of the control valve 16 and a tank T. The flow rate control valve 18 receives a pump pressure and a load sensing pressure corresponding to a pressure on the downstream side of the meter-in control flow path as a pilot pressure, and is activated for opening and closing so as to maintain a constant differential pressure therebetween. The flow rate control valve 18 is maintained in a closed state by a pilot pressure selector valve when the load sensing pressure is low. The control valve 16 opens bypass lines 46, 34 when the meter-in control flow path is closed. COPYRIGHT: (C)2008,JPO&INPIT