| 摘要 |
<p>This invention relates to a hydraulic circuit device of a construction vehicle equipped with an excessive pressure oil control circuit (50) in order to reduce a pressure loss when all the operation valves of a work machine are at neutral positions, to reduce power consumption of a hydaulic pump as a whole when a small amount of pressure oil is necessary for a hydraulic circuit of the work machine, to make it possible to effect arbitrarily an unload instruction of the excessive pressure oil and to make it easier to adjust the change of a flow rate at the time of valve switching. This excessive pressure oil control circuit includes a pilot operated unload valve (11) disposed inside an excessive pressure oil supply pipe (51) connected between a hydraulic pump (P1) dedicated to the work machine and a drain pipe (Ct) through a check valve (20) and a pilot pressure change-over valve (12) disposed inside one of pilot pipes (19) for this unload valve.</p> |
