Patent ID: 7313967

Claim:
A pressure abnormality detecting device for an injection molding machine, comprising: position detecting means for detecting the position of an injection screw; speed detecting means for detecting a movement speed in the axial direction of the injection screw; pressure detecting means for detecting an injection pressure generated by the movement of the injection screw; and means for sequentially determining the rate of change in the pressure with respect to the movement distance of the injection screw from data detected with the position detecting means for the injection screw and the pressure detecting means; wherein a deceleration distance until the injection screw comes to a stop is sequentially obtained from a current speed determined by the speed detecting means during an injection process and a previously determined deceleration inherent in the machine of the injection screw, then the amount of change in the pressure generated until the injection screw comes to a stop is sequentially determined from the obtained deceleration distance and the rate of change in the pressure, and if the sum of the amount of change in the pressure and the pressure detected by the pressure detecting means exceeds a predetermined limit pressure, the injection screw is stopped.