| 摘要 |
PURPOSE:To reduce the discharge quantity in response to the rise of the rotating speed at the fixed rotating speed or above by providing the valve body of a variable throttle valve so as to decrease the throttle opening in response to the rise after the rise to the fixed rotating speed, and connecting the downstream side of the throttle to a suction passage. CONSTITUTION:After the rotating speed of a driving shaft 14 rises to the fixed rotating speed, the valve body 31 of a variable throttle valve B is moved by the action force of the liquid pressure generated on the upstream side of a throttle E by a fixed displacement type hydraulic pump D and the throttle E to decrease the throttle opening. The front/rear pressure difference of the variable throttle valve B is increased by the decrease of the throttle opening, and a pressure compensating valve C moves a valve body 44 to the balanced position between the action force based on the front/rear pressure difference of the variable throttle valve B with the decreased throttle opening and the elastic force of a spring 46 to guide a pressure liquid to the action chamber 28 of an operation piston 26. The operation piston 26 is moved to displace a swash plate 21 in the discharge quantity decreasing direction, and the discharge quantity of a variable displacement type hydraulic pump A is decreased so that the front/rear pressure difference of the variable valve B with the decreased throttle opening is made constant. |
