HYDRAULIC PRESSURE CONTROL DEVICE FOR CONSTRUCTION MACHINE

摘要

PROBLEM TO BE SOLVED: To stably control pump flow rate irrespective of dynamic pressure change while employing a load sensing control system. SOLUTION: Areas of both of a meter in opening and a meter out opening are changed by operating a control valve 23 by a remote control valve 24. An unload valve 26 is provided between a pump line 25 and a tank T and load sensing control changing opening area of the unload valve 26 to keep load sensing pressure difference which is difference between upstream pressure and downstream pressure of the meter in opening constant is performed. On an assumption that the device is constructed like this, a side bypass valve 32 operating as one unit with the unload valve 26 is provided, and pump control pressure Pi taken out from the side bypass valve 32 is introduced to a regulator 38 of the hydraulic pump 21 to control pump flow rate. COPYRIGHT: (C)2008,JPO&INPIT