| 摘要 |
<P>PROBLEM TO BE SOLVED: To lead high-pressure oil in an oil passage portion connecting a valve element and a filter to a relief valve by a relatively inexpensive structure, even when the filter disposed in the oil passage for connecting the valve element and the relief valve clogs. <P>SOLUTION: A hydraulic drive device for a construction machine includes a hydraulic pump 20 and a charge valve 25 to which pressure oil from the hydraulic pump 20 is supplied through an oil passage 26. In the charge valve 25, there are provided: the valve element switched according to the pressure oil discharged from the hydraulic pump 20, such as a shut-off valve 33; the relief valve 34 regulating the maximum value of the switching pressure of the shut-off valve 33; and the filter 36 disposed in the oil passage 35 connecting the shut-off valve 33 and the relief valve 34. The oil passage 35 is provided with a check valve 37 which is provided in parallel with the filter 36, and permits the flow of the pressure oil from the shut-off valve 33 side to the relief valve 34 side while blocking the flow of the pressure oil from the relief valve 34 side to the on-off valve 33 side. <P>COPYRIGHT: (C)2012,JPO&INPIT |
