| 摘要 |
<p>PURPOSE:To keep the intra-circuit pressure of a cargo handling hydraulic cylinder at a low pressure in the region with a low engine rotating speed and at a high pressure in the region with a high engine rotating speed. CONSTITUTION:In an oil control valve 1 provided on a circuit connecting a hydraulic pump 6 driven by an engine 5 to a load handling hydraulic cylinder 8, a relief valve 3 and an orifice 4 are provided on the relief passage 11 of the operating oil connecting a high-pressure circuit 9 and a low-pressure circuit 10. The set pressure of the relief valve 3 is set lower than the conventional one, and the diameter of the orifice 4 is set to the size capable of releasing the total quantity of the operating oil discharged from the hydraulic pump 6 at least at the time of the idling of the engine 5. The intra-circuit pressure of the high-pressure circuit 9 becomes a low pressure set by the relief valve 3 in the region with a low engine rotating speed, and it becomes a high pressure added with the pressure generated by the squeezing action of the orifice 4 to the pressure set by the relief valve 3 in the region with a high engine rotating speed.</p> |
