| 摘要 |
PROBLEM TO BE SOLVED: To provide a hydraulic control device of a construction machinery considering energy saving without lowering speed in simultaneously operating a heavy load and a light load and capable of providing favorable operability. SOLUTION: A main spool 36 is provided on a central part of a valve body 34 of a hydraulic control valve CV. Hydraulic oil from a hydraulic supply port 46 reaches a detection port 48 as shown by perspective viewsα,β,γ,δthrough a passage 54c of a spool 54a of a pressure compensating valve 54 arranged on the meter-in side relative to a hydraulic cylinder 32 when the main spool moves in the Y direction when the maximum negative load on the other side 52b of a load sensing part 52 is inferior to springing force of a spring 54d and is supplied to a cylinder port PA from a hydraulic supply passage 44 through a hydraulic supply passage 58 and through a check valve 66. In the meantime, the spool 54a moves to the left and blocks the passage 54c when the maximum load pressure is dominant. The hydraulic oil of the detection port is supplied to the hydraulic supply passage 58 through a by-pass 50 even in this blocked state. COPYRIGHT: (C)2008,JPO&INPIT
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