Patent ID: 8807200

Claim:
An electrically driven injection device for a die-casting machine, comprising a first injection electric motor used for low-speed injection and intensification, a second injection electric motor used for high-speed injection, a first power transmission mechanism for transmitting rotary motion of the first injection electric motor to a screw shaft of a ball screw mechanism, a second power transmission mechanism for transmitting rotary motion of the second injection electric motor to the screw shaft, a first clutch mechanism provided in the first power transmission mechanism, a second clutch mechanism provided in the second power transmission mechanism, a nut threaded on the screw shaft, a linear motion body holding the nut, an injection plunger having one end linked with the linear motion body, and a controller for controlling start/stop of the first and second injection electric motors and disengagement/engagement of the first and second clutch mechanisms, wherein: the controller memorizes points in time where a low-speed injection step, a high-speed injection step and an intensification step are to commence; starts the second injection electric motor from a stopped state before the point in time where the high-speed injection step is to commence; and switches the second clutch mechanism from a disengaged state to an engaged state at the point in time where the high-speed injection step is to commence, or at a point prior thereto and after a point in time where the second injection electric motor is started.