HYDRAULIC CIRCUIT, AND PRESSURE CONTROL METHOD FOR INJECTION DEVICE OF INJECTION MOLDING MACHINE AND HYDRAULIC CIRCUIT

摘要

PROBLEM TO BE SOLVED: To eliminate chattering by correctly controlling pressure of hydraulic oil. ;SOLUTION: In an injecting process, a pressure command setting apparatus 27 supplies operating currents different from each other to pressure control valves 25a and 25b by amplifiers 26a and 26b, and their pressures are set such that a set pressure of the pressure control valve 25b is smaller than a set pressure of the pressure control valve 25a by a predetermined value. A hydraulic oil is sent to a bottom of an injection cylinder 3 passing through branch pipes 5a and 5b of a main line 5 so as to move the injection cylinder 3 by injection. At this time, a pressure reducing valve 23b makes the hydraulic oil flow to the branch pipe 5b so as to heighten responsibility of pressure rise. Also, a check valve 30 blocks back flow of the hydraulic oil which has passed through a flow rate control valve 13a to the branch pipe 5b, and leakage of the hydraulic oil from the pressure reducing valve 23b of small pressure setting is prevented.;COPYRIGHT: (C)1998,JPO