| 摘要 |
<P>PROBLEM TO BE SOLVED: To simplify the constitution of a hydraulic circuit, by enhancing operation performance of an operation lever, in proper use between a 1-pump/1-motor independent circuit system and a 2-pump merging series circuit system. Ž<P>SOLUTION: This hydraulic circuit has 2-speed cutoff switching valves 101-104 arranged in a pipe communicating with a pilot operation part of a valve section of a 2-speed spool of a control valve from remote control valves 22 and 24, a switching selecting means 105 for this switching, proportional pressure reducing valves 111-114 for changing output secondary pressure in response to secondary pressure of the remote control valves, and secondary pressure changing switching valves 116-119 arranged in the pipe communicating with the pilot operation part of the valve section of a 1-speed spool of the control valve from the remote control valves. The secondary pressure changing switching valves are respectively switched to a first position for transmitting the secondary pressure of the remote control valves to the pilot operation part when switching to a transmission position of the 2-speed cutoff switching valves and a second position for transmitting the secondary pressure of the proportional pressure reducing valves to the pilot operation part when switching to a cutoff position of the 2-speed cutoff switching valves. Ž<P>COPYRIGHT: (C)2010,JPO&INPIT Ž
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