| 摘要 |
PURPOSE:To prevent excessive torgue to an engine by providing a variable restriction device which is operated to open a check valve on a throttle valve located in the pilot circuit of a pump capacity control cylinder when a hydraulic drive main circuit is under high pressure. CONSTITUTION:The pilot circuit 10 of a pump capacity control cylinder C is provided with a oneway throttle valve 11 (a throttle valve 111, a check valve 112) and a pilot operation switching valve 13 which is operated by main circuit oil pressure let through a pilot pipe 12 from a main circuit S. The switching valve 13 is provided in parallel with the oneway throttle valve 11 in the pilot circuit 10 so that the switching valve 13 is opened when oil pressure in the main circuit S increases over the set pressure of the switching valve 13, and pressurized oil in the control cylinder C flows out via the switching valve 13, consequently, the reducing speed of the discharge capacity of a variable pump P becomes fast and excessive torque to an engine is prevented. |
