HYDRAULIC CIRCUIT OF WHEEL TYPE EXCAVATOR FOR RELIEVING DISCOMFORT OF DRIVER BY RESTRICTING BOOM FROM LIFTING UP IN RELEASING BOOM HOLDING FUNCTION BY DETECTING TRAVEL SIGNAL

摘要

PURPOSE: A hydraulic circuit of a wheel type excavator is provided to relieve the fatigue of an operator without placing the boom in the boom rest by stopping the equipment in moving up the boom while traveling, and to improve the safety by finely controlling the boom down. CONSTITUTION: A hydraulic circuit of a wheel type excavator comprises hydraulic pumps(1,1a) connected to an engine, a pilot pump(16), actuators driven and connected to the hydraulic pumps, switching valves installed between the hydraulic pumps and the actuators and switched to control operation, stop and direction change of the actuator according to the pilot signal pressure from the pilot pump, a holding valve(9) mounted between the boom switching valve and the boom cylinder to prevent leak of the spool, a shuttle valve(10) installed in the confluence of the pilot signal line of the boom switching valve and the holding valve to select high pressure among boom down pilot pressure and pilot pressure for opening the holding valve, and a pressure unit pressurizing the pilot signal pressure to the holding valve via the shuttle valve to release boom holding function in selecting the travel mode.