| 摘要 |
PURPOSE:To form a charge pump in small size by using return oil of a power steering hydraulic circuit partly as operating oil supplied to a running main hydraulic circuit. CONSTITUTION:Return oil from a swash plate control circuit 13 and from a power steering hydraulic circuit 34 is merged in the upstream of a filter 33 and supplied to a running main hydraulic circuit 10 via a branch pipe line 17 while a pressure of operating oil in the upstream from a charge relief valve 18 is lower than the relief pressure. After a necessary amount of operating oil is supplied to the running main hydraulic circuit 10, a pressure of operating oil in the upstream from the charge relief valve 18 is increased higher than the relief pressure, and the surplus operating oil is returned to an oil tank 15 by opening the charge relief valve 18. Thus, a necessary amount of the operating oil is always supplied as the return oil to the running main hydraulic circuit 10 through the branch pipe line 17 and a supply circuit 21. In this way, a charge pump 4 can be formed in small size. |
