| 摘要 |
<p>Cylinder drift resulting from internal leakage of a recycling circuit, which recycles oil returned from an arm cylinder of a hydraulic shovel to the hydraulic supply end, is reduced by an hydraulic circuit which includes a recycle valve attached directly to a control valve. When working fluid is returned from a rod chamber of an arm cylinder into the control valve, the recycle valve recycles a part of the working fluid through a recycle selector valve to the hydraulic supplying end. A pilot operated check valve is disposed in the oil channel that connects the rod chamber and recycle selector valve together. When extending arm cylinder of the hydraulic shovel, pilot pressure from control valve shifts a pilot selector valve in such a direction as to open pilot operated check valve. When the control valve is at the neutral position, pilot selector valve is shifted back to the return position and closes the pilot operated check valve so that return oil of the arm cylinder is prevented from working on recycle selector valve. Thus, internal leakage of recycle selector valve is prevented. <IMAGE></p> |
