| 摘要 |
PCT No. PCT/JP96/02660 Sec. 371 Date May 16, 1997 Sec. 102(e) Date May 16, 1997 PCT Filed Sep. 17, 1996 PCT Pub. No. WO97/11278 PCT Pub. Date Mar. 27, 1997Pump ports 9p, 10p, 11p, 13p of boom, arm, bucket and first travel directional control valves 9-11, 13 are connected to first and second hydraulic pumps 1a, 1b through feeder lines 93a, 93b; 103a, 103b; 113a, 113b; 133a, 133b. Auxiliary valves 91a, 91b; 101a, 101b; 111a, 101b; 131a, 131b controlled respectively by proportional solenoid valves 31a, 31b; 32a, 32b; 33a, 33b; 34a, 34b are disposed in those feeder lines. The auxiliary valves each have a function as a reverse-flow preventing function and a variable resisting function including a flow cutoff function, whereby a joining circuit and a preference circuit can be realized in the closed center circuit with a simple structure and further, a preference degree and metering characteristics can be set independently of each other during the combined operation of plural actuators.
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