| 摘要 |
PURPOSE:To absorb surge pressure in the vicinity of set pressure no matter how various at values may be set, by connecting a spring chamber to a space between a throttle and an electromagnetic proportion relief valve. CONSTITUTION:At the time of flow control, a controller 75 outputs to an electromagnetic proportion relief valve 38 a variation (q) between a set value Q1 and a variable pump 31 discharge quantity detected by means of a flow sensor 72. Pressure difference is generated at the front and rear of the throttle 37 of a control line 35 by the operation of the electromagnetic proportion relief valve 38, and a control valve 41 conducts changeover operation by receiving at a spring chamber 62b pressure downstream of the throttle 37 and receiving at a pilot chamber pressure upstream of the throttle 37, that is, a discharge line 32, and controls the discharge amount of the variable pump 31. In this control state, when surge pressure is suddenly generated at the discharge line 32, pressure difference is generated at the front and rear of the throttle 37 through the throttle 37 of the control line 35 and the electromagnetic proportion relief valve 38, and pressure downstream of the throttle 37 is led to the spring chamber 62b of a surge absorption valve 62. Accordingly, surge pressure can be cut at all times. |
