| 摘要 |
<P>PROBLEM TO BE SOLVED: To achieve excellent operability by using at least three variable capacity type hydraulic pumps, to save on the energy, and to appropriately cope with the use of an attachment requiring a fixed flow rate, in a hydraulic circuit device of a construction machine. <P>SOLUTION: The hydraulic circuit comprises a switch 28 for commanding to fix the capacity of a third hydraulic pump 4, an electromagnetic proportional pressure reducing valve 30 operated based on a signal from the switch 28, and a selector valve 31 to be switched so that an input port is connected to an output port when the signal pressure is received from the electromagnetic proportional pressure reducing valve 30. A second regulator 27 has a built-in selector valve 67 for fixing the capacity of the third hydraulic pump 4 at the maximum by the signal pressure from the electromagnetic proportional pressure reducing valve 30. <P>COPYRIGHT: (C)2003,JPO |
