Patent ID: 7904196

Claim:
An apparatus for controlling pressure in an electric injection molding machine, comprising: an observer arithmetic unit operative to derive an estimated melt pressure value δ^, based on an observer, from an angular velocity ω of a motor operative to propel forward a screw in an injection molding machine and a torque command value T CMD given to said motor; and a torque arithmetic unit operative to calculate said torque command value T CMD for said motor using said estimated melt pressure value δ^ derived at said observer arithmetic unit and feed back said torque command value to said motor, wherein said observer arithmetic unit comprises: a first and second adders operative to subtract the angular velocity ω from an estimated angular velocity value ω^ −1 obtained at immediately preceding processing; a first and a second adjusters operative to adjust an output value (ω^ −1 −ω) from the first and second adders into amplitude corresponding to coefficients d 1 and d 2 , respectively; a third adder operative to add the torque command value T CMD −1 and an estimated melt pressure value δ^ −1 obtained immediately preceding processing; a fourth adder operative to add an output value (T CMD −1 +δ^ −1 ) from the third adder and a frictional resistance F(ω) over the electric injection molding machine; a third adjuster operative to adjust an output value (T CMD −1 +δ^ −1 +F(ω)) from the fourth adder into amplitude corresponding to a coefficient 1/J; a fifth adder operative to add outputs from the first and third adjusters; a first integrator operative to integrate an output from the fifth adder to obtain an estimated angular velocity value ω^; and a second integrator operative to integrate an output from the second adjuster to obtain the estimated melt pressure value δ^.