| 摘要 |
PURPOSE:To decrease the discharge amount and shorten the time of response by furnishing a throttle element between a solenoid-operated proportional valve and an operational cylinder, and installing a bypass valve which is actuated only when the pump discharge amount decreases in response to the differential pressure given by the first mentioned arrangement. CONSTITUTION:A throttle element 6 is interposed between a head oil chamber 12 of an operational cylinder 4 and a solenoid-operated proportional four-way valve 5, and the differential pressure in front of and behind this throttle element 6 is led to pilot chambers 25, 26 of a bypass valve 8 through pipelines 9, 24. This bypass valve 8 is a one-way selector valve and is installed between pump 3 discharge line 15 and the head oil chamber 12. The valve element of the bypass valve 8 is operated in these pilot chambers 25, 27 and energized by a spring always to the right, i.e., in the direction of closing. When the differential pressure is greater than the force of spring, the valve is moved to the left, i.e., in the direction of opening to introduce the discharge pressure in the line 15 to the head oil chamber 12, while a variable device 11 is moved to the side of decreasing the pump 3 discharge amount quickly. |
