| 摘要 |
PURPOSE:To limit excessive pump discharge flow rate over the specified flow rate by interposing a shuttle valve in a negative-control command circuit to communicate a port located mostly downstream from a center bypass to the regulator of a hydraulic pump, and providing an electromagnetic proportional pressure reducing valve to introduce a pilot pressure against the negative-- control pressure. CONSTITUTION:A shuttle valve 22 is interposed in a negative-control circuit A to communicate a port 19 located mostly downstream from a hydraulic changeover valve 12 to a regulator, and there is provided an electromagnetic proportional pressure reducing valve 23 to introduce the pilot pressure against the negative control pressure and it is controlled by a controller 26. The controller 26 receives input signals from a turning maximum flow rate command setting device 27 and a flow rate stepless command setting device 28, sets up the maximum discharge flow rate of a pump 1, then the pilot pressure from a pilot pressure oil source 25 via the electromagnetic proportional pressure reducing valve 23 is selected by means of the shuttle valve 22 and is applied to the regulator 3. Accordingly excessive discharge flow rate of the pump 1 is limited, leading to improvement of energy loss. |
