| 摘要 |
PURPOSE:To decrease a power loss of an engine, by using two fixed displacement discharge pumps so that two kinds of flows of low pressure but high rate and high pressure but low rate may be obtained, thereby it is possible to automatically select the operation of a vehicle between the high speed run on a flat land and the climbing run on an acsending slope road. CONSTITUTION:First and second pumps P1, P2 are driven by an engine installed in the rear of a turn bed, and the discharge amounts Q1, Q2 of te first and second pumps P1, P2 are set such as Q2>Q1. The discharge circuits 101, 102 of the pumps incorporate check valves CK1, CK2, and the discharge circuit 102 is merged and connected with the discharge circuit 101. A branch line incorporating an unloader valve R3 which is opened at a set pressure PC is connected to the discharge circuit 101, and a solenoid shutoff valve V which may be controlled from a control section is incorporated in a vent circuit for a second relief valve R2. The discharge circuit 101 is connected to electromagnetic proportional control valves V1... which are connected in parallel with each other, and hydraulic pressure from the valve V1 is fed to a travelling motor 11. |
