Hydraulic control system for construction machine

摘要

In a controller (229) of a hydraulic control system for construction machines, a valve control signal calculating function (301) works such that when an operation pattern signal (A - I) for actuators (201, 202...) is outputted, it selects corresponding one of plural output patterns for an auxiliary valve control pressure stored, as a function of a differential pressure signal between a pump delivery pressure and a maximum load pressure, in relation to the operation pattern signals, followed by calculating an auxiliary valve control pressure (Pc) dependent upon the differential pressure signal based on the selected output pattern, and also selects corresponding one of plural sets of change speeds (K.., K..) for the auxiliary valve control pressure stored in relation to the operation pattern signals, followed by combining the calculated auxiliary valve control amount with the selected set of speed changes to calculate each of valve control signals (S21 - S26). A pump control signal calculating function (300) works such that when an operation pattern signal is outputted, selects both corresponding one of plural sets of control gains (LSD, LSU) for a hydraulic pump (220) stored in relation to the operation pattern signals (A - I) and corresponding one of plural differential target pressures also stored in relation to the operation pattern signals, followed by determining a deviation between the differential pressure signal and the selected target differential pressure, calculating pump control signals (S11, S12) to reduce the differential pressure deviation using the differential pressure deviation and the selected set of control gains (LSD, LSU), and controlling the displacement volume of the hydraulic pump (220). <IMAGE>