| 摘要 |
A hydraulic driving system uses a variable capacity type swash plate piston pump that discharges a fixed quantity of operation oil. The piston pump is provided with a swash plate and a swash-plate tilt angle control mechanism. The pump is operated by the engine to drawing discharge oil whose quantity corresponds to the tilt angle of the swash plate. An oil passage provided with a restriction, is connected to the discharge side of the piston pump. A control valve functions in accordance with the pressure difference between the input and output sides of that restriction to feed operation oil to the tilt angle control mechanism via the oil passage. A tilt angle generating mechanism in the tilt angle control mechanism, causes the oil controlled by the control valve to act on the swash plate in order to increase its tilt angle. A tilt angle return mechanism in the tilt angle control mechanism urges the swash plate to decrease the tilt angle. A switching valve is provided between the tilt angle generating mechanism and the control valve, and is switchable between at two positions. With the valve located at the first switching position, the action of the operation oil to the tilt angle generating mechanism is suppressed. With the valve set at the second switching position, the operation oil is allowed to act on the tilt angle generating mechanism via the control valve. Consequently, when the pump is driven, the tilt angle is minimized to reduce the load on the engine.
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