| 摘要 |
PURPOSE:To provide a control device which can control an actuator to high speed when a pump is operated by disposing a piston between high-speed and low-speed control switching valve and an inclined plate control piston and a pilot control valve switched to connect with a hydraulic motor driving circuit and a tank. CONSTITUTION:In case of driving a hydraulic running motor 51 at high speed, with a switching control valve 55a on the upper position, a high-speed and low- speed control switching valve 55 is switched to the upper position. When a car is braked or the car travels down a steep slope during high-speed driving, the motor 51 performs a pump action by inertia. Since the pressure of a driving circuit 59 is high, the pressure is conducted through a branch circuit 65, a check valve 67, a circuit 64, a pilot control valve 62 and a circuit 61 to a piston chamber 53b of an inclined plate control piston 53, so that the piston chamber 53b is kept at high pressure, and the high-speed range can be retained. At the time of low-speed driving, the valve 55 is switched to switch a valve 62, so that the piston chamber 53b is connected to a tank 57.
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