| 摘要 |
PROBLEM TO BE SOLVED: To solve problems that oil passages are branched in a conventional hydraulic circuit, a pilot oil passage control valve is provided between the oil passages, and the piping becomes complicated and the cost is increased. SOLUTION: The hydraulic pressure feed control of a plurality of hydraulic actuators is performed by each control valve, each control valve is switched by a pilot operating means and other means, an unload oil passage switching valve 35 is provided between an unload oil passage leading to an oil tank, oil passages 36 and 40 to feed the hydraulic pressure to a control valve of each hydraulic actuator, and a hydraulic pump 31, control valves 50 and 60 to simultaneously switch ON-OFF output ports of two systems are provided on a discharge oil passage of the hydraulic pump, the output port of one system is connected to valves 56, 57, 58 and 59 to switch the feed of the pilot hydraulic oil to the control valves, and the other system is connected to a pilot operation unit 35a of the unload oil passage switching valve. |
