| 摘要 |
PROBLEM TO BE SOLVED: To save energy by eliminating the need of a dedicated pump for a pilot pressure source. SOLUTION: This control circuit comprises pilot primary pressure passages 10, 11 having a pump P, a supply passage 6 connected to the pump, and control valves 7, 8, 9 connected to the supply passage 6 and controlling the direction and amount of a working fluid supplied to actuators 2, 3, 4 and connected to the control valves, a high-pressure selection circuit 18 selecting the maximum load pressure of the load pressures of the actuators, and a connection passage 19 serving as a neutral passage 5 and connecting the downstream side A of the control valves to the high-pressure selection circuit. The pilot primary pressure passages are connected to the middle part of the connection passage 19. When the neutral passage 5 is communicated, the pressure generated in the neutral passage is used as a pilot pressure source led into the pilot primary pressure passage. When the neutral passage 5 is cut off by changing over the control valves, the pressure in the high-pressure selection circuit 19 is used as the pilot pressure source. COPYRIGHT: (C)2007,JPO&INPIT
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