Hydraulic circuit of an injection molding machine

摘要

A hydraulic circuit of an injection molding machine includes a 4-port servo valve having A, B, P, and T ports and adapted to drive and control an injection cylinder. The A and B ports are connected respectively to the front and rear oil chambers of the injection cylinder. The P port is connected to a hydraulic power unit. The T port is connected to an oil tank via a shutoff valve for selecting a regular mode or a differential mode. The T port is connected to the rear oil chamber via the logic valve. Alternatively, the rear oil chamber is connected to a hydraulic power unit side via the servo valve; the front oil chamber is connected to an oil tank via the shutoff valve; and the front oil chamber is connected to the P port of the servo valve via the logic valve. The above configuration eliminates or simplifies an additional braking circuit. Also, proper and accurate braking control can be performed.