PCA HYDRAULIC SYSTEM OF CONSTRUCTION MACHINERY

摘要

The present invention relates to a PCA hydraulic system of construction machinery, including an actuator (70) formed with first and second ports (70a, 70b) at a head side of a cylinder (72) and a rod (74) side; an accumulator (80); a first hydraulic line (La) connected to a pump/motor (40) and the first port (70a), in which the first pressure (Pa) is formed; a second hydraulic line (Lb) connected to the pump/motor (40) and the second port (70b), in which the second pressure (Pb) is formed; first and second check valves (310, 320) for allowing working oil to flow toward the first and second hydraulic lines (La, Lb) only; a plurality of relief valve units (60) for maintaining the first and second pressure (Pa, Pb) in a value equal to or less than the set pressure; and a control valve unit (200), if the first and second pressure (Pa, Pb) is applied to both sides of a spool, and high pressure is formed at any one of the first and second pressure (Pa, Pb), for interrupting the high pressure from the accumulator (80), and connecting the low pressure with the accumulator (80).