| 摘要 |
An hydrostatic transmission for a vehicle having a closed loop hydraulic system hydraulically interconnecting a variable displacement hydraulic pump 1 and a hydraulic motor 2. The closed loop hydraulic system includes first and second circuits 3, 4 forming the closed loop. The first circuit 3 is connected with a first relief valve 7a having high and low setting pressure and the second circuit 4 is connected with a second relief valve 7b having high and low setting pressure. An hydraulic control pump 11 is provided for controlling the setting pressure of the first and second relief valves and a pilot-operated change over valve 9 is disposed between the control pump and the first and second relief valves. For each direction of travel the relief valve for the flow line (3 or 4) from the pump to the motor is set at a high pressure and that for the return line (4 or 3 respectively) is set at a low pressure to limit hydrostatic braking, prevent cavitation and prevent overspeeding of the prime mover during braking. <IMAGE> |
