| 摘要 |
PROBLEM TO BE SOLVED: To simplify a structure and reduce a cost by attaining merit of an after-orifice type circuit where satisfactory flow rate distribution performance is shown even in the case that sum of required flow rates exceeds a maximum discharge rate of a pump under the condition of multiple operation, with a function of before-orifice type circuit without arranging anti-saturation valves. SOLUTION: A before-orifice type load sensing circuit has pressure compensation valves 12, 13 arranged on upstream sides of throttles 15, 16 internally arranged in control valves 10, 11. In such a load sensing circuit, the pressure compensation valves 12, 13 are formed to be a four-signal input type which is energized to a flow passage disconnection side, by utilizing a first intermediate pressure PZ after passing the pressure compensation valves, and before passing the throttle 15, and a maximum load pressure VLS among load pressures of hydraulic actuators 6C, 7C and a spring 21. The valves 12, 13 are energized to a flow passage connection side, by utilizing a discharge pressure VP of a hydraulic pump 9 and a second intermediate pressure PL after passing the throttle 15, and before passing the hydraulic actuators 6C, 7C.
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