Control system for a hydraulically driven vehicle

摘要

A control system for a hydraulically driven vehicle having a pair of variable displacement hydraulic pumps driven by an engine and a pair of hydraulic motors each being connected with the respective variable displacement hydraulic pumps in a closed loop and driven thereby. The control system comprises a pair of servo valves each for controlling the displacement of the respective variable displacement hydraulic pumps, a servo control valve for controlling the servo valve and a manually operated change-over valve connected with a fixed displacement charge pump and with the servo control valve, the change-over valve being normally held in a communication position and being adapted to be changed over to an offset position when operated where the output side of the fixed displacement charge pump is connected with a tank.