FLOW CONTROL DEVICE OF A HYDRAULIC PUMP OF AN EXCAVATOR FOR PREVENTING THE SPEED REDUCTION OF AN ATTACHMENT BY HOLDING THE INCLINATION ANGLE OF A MAIN PUMP BY CONTROLLING PRESSURE INSERTED FROM A NEGATIVE LINE TO AN INCLINATION ANGLE CONTROL UNIT

摘要

PURPOSE: A flow control device of a hydraulic pump of an excavator is provided to prevent pressure applied into an inclination angle control unit of a main pump from rising by the increase of bypass flow caused by work load in a negative line by installing a solenoid pressure-reducing valve in the negative line. CONSTITUTION: A flow control device of a hydraulic pump of an excavator is composed of a main pump(1) for supplying working fluid; a control valve(8) for controlling the direction of the working fluid fed from the main pump; an attachment(7) connected with the control valve and operated by the working fluid discharged from the control valve; a negative relief valve(9) for forming negative pressure by the working fluid discharged form the control valve; a pilot gear pump(2) for exhausting pilot pressure to adjust the inclination angle of the main pump; and a solenoid pressure-reducing valve(4,5) for controlling the inclination angle of the main pump by a control signal of a CPU(Central Processing Unit,6) for detecting the load of an engine(3) by using the pilot pressure. The flow control device detects the load of the engine by the CPU in driving the attachment and keeps the speed of the attachment constant by controlling the secondary pressure of the solenoid pressure-reducing valve installed on a negative line(10) extended from the negative relief valve to the main pump and controlled by the CPU.