INJECTION PRESSURE CONTROL OF INJECTION MOLDER

摘要

PURPOSE:To prevent the overrun of a servo motor and a screw and control an injection pressure at any value by outputting a torque command to a servo motor which drives an injection mechanism through a torque limiting means and applying torque limitation to only an injection direction. CONSTITUTION:A torque limiting command (g) is output by a digital control and other means so that an injection pressure may reach a target level to allow a control voltage + Vr as a torque limiting value to be input to a buffer amplifier 10 through a diode D. If an injection position command (a) is input to this servo circuit 1, a speed command value (c) is output by a D/A converter 4 as a voltage and the differential between said voltage (c) and a voltage V which meets the real speed of a servo motor M is amplified by an error amplifier 6. Then the differential is output as a torque command (e). The differential between the voltage (e) and a detection output f (voltage) to detect an armature current of the servo motor M from a current detector 9 is amplified by an error amplifier 7 and then by a power amplifier 8 to drive the servo motor M. Thus a screw is advanced to allow the injection.