HYDRAULIC CONTROL SYSTEM

摘要

PROBLEM TO BE SOLVED: To improve a pressure control characteristic with a reduction in cut-off range, and a dynamic characteristic at the time of switching from flow control to pressure control. SOLUTION: When pressure liquids discharged from variable delivery hydraulic pumps 4 and 5 are joined via a check valve 1 by operating a direction switching valve 6, an operating command input means 30 outputs an operating pressure command value Sp2 identically for control devices 18 and 27. At that time a pressure signal switch 15 switches each control pressure signal of the variable delivery hydraulic pumps 4 and 5 to a pressure signal of a pressure detector 7a. Thereby an increase in cut-off range due to a pressure loss of the check valve 1 and a control oscillation phenomenon due to a rapid shutoff of the same are prevented. And a head differential set switch 16 outputs an operating signal Sh2 to a control valve 9 such that a pressure P2 is controlled much lower than a pressure P1.