HYDRAULIC SYSTEM FOR CONSTRUCTION MACHINE

摘要

Disclosed is a hydraulic system capable of reducing the discharge flow rate of a hydraulic pump during the operation of a relief valve in the hydraulic system having the relief valve. The hydraulic system for a construction machine according to the present invention comprises: a variable delivery hydraulic pump connected to an engine; a device for operating a working device, which outputs an operation signal in proportion to the amount of operation performed by an operator; an actuator for the working device, which is connected to the hydraulic pump and driven by the operation of the device for operating the working device; a control valve installed in the flow channel between the hydraulic pump and the actuator for the working device so as to control, when actuated, the start, pause, and direction change of the actuator for the working device; an orifice installed in the flow channel that is branched off from the discharge flow channel of the hydraulic pump; a relief valve installed downstream from the orifice in the flow channel; and a controller for outputting a control signal to a hydraulic pump flow control valve so as to decrease the discharge flow rate of the hydraulic pump when the pressure differential between the front portion and rear portion of the orifice exceeds a preset value.