| 摘要 |
PURPOSE: A hydraulic circuit for the heavy equipment having a two-stage port relief valve is provided to offer convenience to a driver by automatically increasing the operating pressure in a hydraulic circuit via a two-stage relief valve operated via a switch, to reduce the prime cost by reducing the number of parts, and to easily lay pipes by excluding a pipe for returning an operating oil. CONSTITUTION: A main pump(4) and a pilot pump(5) are driven by an engine. An actuator is driven by being connected to the main pump. A directional change valve(3) installed on a path between the main pump and the actuator controls the flow direction of an operating oil supplied to the actuator. A remote control valve(2) operated by a driver supplies a pilot signal for change to the directional control valve. Two-stage port relief valves(11,12) set the pressure in a hydraulic circuit as a high-pressure region or a low-pressure region to selectively supply high-pressure operating oil or low-pressure operating oil to the actuator. A solenoid valve(13) supplies the pilot signal pressure to the directional change valve and the two-stage port relief valves from the pilot pump.
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