| 摘要 |
PURPOSE: To reduce a discharge capacity in the minimum capacity operating state of a minimum capacity starting pump by switching a capacity switching valve into a communicating position when a cargo switching valve is switched into a cargo position, and switching the capacity switching valve into a shut-out position when the cargo switching valve is switched into a no cargo position. CONSTITUTION: In a cargo switching valve 20 which is connected to a cargo actuator 22 to be connected to the discharge pipe passage 21 of a pump P1, limit switches 24α to 24γ are provided so as to detect the operating position of an operating lever 23 for switch-operating the valve 20, and a cargo position signal and a no cargo position signal are supplied to a control circuit 25 according to a detecting position. In a pump 1, the capacity thereof is switched by a control cylinder 14, and the control chamber 14αof the control cylinder 14 and the discharge pipe passage 21 are connected to each other by control passages 26α, 26β with which a capacity switching valve 27 is interposed. The capacity switching valve 27 is switching-controlled on a communicating position by the control circuit 25 when the cargo switching valve 20 is on a cargo position. |
