| 摘要 |
PROBLEM TO BE SOLVED: To reduce a shock, only adding a simple control device, by controlling a solenoid valve such that a direction switching valve returns to a neutral position or a neighboring position when a controller detects a rapid increase of negative pressure or a negative pressure exceeding a predetermined pressure. SOLUTION: A pressure sensor 22 for detecting a working fluid pressure is connected to an oil passage 23, and a controller is connected to an output end. The controller detects a load pressure, or an increasing speed of the load pressure based on a measured pressure data from the output end of the pressure sensor 22. When the load pressure exceeds a predetermined load pressure, control current is output to a solenoid of a solenoid proportional pressure reducing valve 14, and a solenoid control valve 14 is changed from a state (a) to a state (b), thereby controlling such that same pilot hydraulic pressure acts on pilot ports 4c, 4d of the direction control valve 4 via shuttle valves 11, 12. Accordingly, reduction of a shock can be performed using the pressure sensor 22 and a simple control device.
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