Patent ID: 8871128
Filing Date: 2014-10-28
Classification: B29C

Abstract:
1. A method for controlling pressure in an electric-motor driven injection molding machine having an injection and pressure application mechanism in which rotation of a servomotor is transferred to rotation of a ball screw through a reduction gear and rotation of said ball screw is converted to a linear motion of a nut of said ball screw and said nut drives a moving part and a linear motion of a screw is realized through said moving part and pressure application to a melted polymer stored at the end of a barrel and fill-up of a cavity with polymer melt are realized by a movement of said screw, comprising: deriving an estimate of injection pressure {circumflex over (x)} where x where k: Discrete variable representing a discrete-time t where {circumflex over (η)}(k): Estimate η(t where {circumflex over (x)}(k): Estimate {circumflex over (x)} where {tilde over (η)}: Estimate error of injection pressure, χ providing a detection means having very small time-lag for said estimate of injection pressure which makes the estimation error tend to zero rapidly and enables said estimate of injection pressure to be detected with very small time-lag wherein the equation (119) given as the time response of the equation (118) is used to show that the estimation error {tilde over (η)} caused by neglecting the effects of the model errors δ where {tilde over (η)} feeding said estimate of injection pressure and an injection pressure command signal fed by an injection pressure setting device to a subtractor; deriving a difference signal between said injection pressure command signal and said estimate of injection pressure by using said subtractor; feeding said difference signal to a pressure controller; deriving said motor current demand signal by using said pressure controller so that said estimate of injection pressure follows said injection pressure command signal; feeding said motor current demand signal to a motor controller; and controlling said servomotor by said motor controller so as to generate an actual motor torque corresponding to said motor current demand signal so that an injection pressure equal to said injection pressure command signal is realized.