| 摘要 |
PURPOSE:To enable a delivery amount of a variable displacement pump to be controlled easily further in plural steps, by providing a throttle and a selector valve or the like respectively in plural branch lines which branch to a tank from a control line connecting a control pump to the variable displacement pump. CONSTITUTION:An engine 11 connects a variable displacement pump 12 and a fixed displacement control pump 13 respectively to be associated with the engine. And the pump 12 connects an oil hydraulic motor 15 for vehicle running through each main line 16, 17. While the control pump 13 connects each cylinder 22, 23, which controls a tilt angle of a swash plate 21 in the pump 12, through each control line 26-28 having a selector valve 25 in the intermediate. Here the control line 26 provides a branch line 41, which branches to a tank 38 from between a sequence valve 37 and the control pump 13 in the control line 26, and a throttle 39 in this branch line 41. While the control line 26 is connected to a return line 46 by a branch line 49 having a selector valve 47 and a relief valve 48. |
