Motor-driven injection driving apparatus for an injection molding machine

A motor-driven injection driving apparatus for an injection molding machine, which is configured so that the rotation of an electric motor is converted into linear motion, and an injection screw is moved forward and rearward by said linear motion, comprising:

• a fixed frame provided with an injection cylinder in which said injection screw is fitted so as to be moved forward and rearward;
• first and second injection drive motors installed on said fixed frame;
• first and second ball screw shafts which are pivotally supported on both sides of said fixed frame so as to be in parallel and symmetrical with respect to the axis of said injection cylinder and so as to be rotatable, and are driven by said first and second injection drive motors, respectively;
• a movable frame capable of being moved in the direction of injection together with said injection screw;
• a screw drive motor, which is mounted on said movable frame, for rotatively driving said injection screw;
• first and second ball screw nuts threaded on ball threads of said first and second ball screw shafts, respectively;
• a pressure detecting sensor interposed between said movable frame and each of said ball screw shafts;
• and
• control means for providing feedback control of a screw back pressure, injection speed, and dwell pressure after injection so that the pressure detected by said pressure detecting sensor becomes a preset injection pressure.

A motor-driven injection driving apparatus for an injection molding machine, which is configured so that the rotation of an electric motor is converted into linear motion, and an injection screw is moved forward and rearward by said linear motion, comprising:

• a fixed frame provided with an injection cylinder in which said injection screw is fitted so as to be moved forward and rearward;
• first and second injection drive motors installed on said fixed frame;
• first and second ball screw shafts pivotally supported on both sides of said fixed frame so as to be in parallel and symmetrical with respect to the axis of said injection cylinder and so as to be rotatable;
• first and second intermediate bearing frames, provided on one side and another side of said fixed frame;
• first and second power transmission mechanisms for transmitting the rotational forces of said first and second injection driving motors to said first and second ball screw shafts, respectively, while reducing the speed, each of said power transmission mechanism including an intermediate transmission shaft pivotally supported on said intermediate bearing frame so as to be rotatable and winding transmission means for transmitting power from said injection drive motor to said ball screw shaft through said intermediate transmission shaft while reducing the speed;
• a movable frame which is provided, on both sides, with first and second ball screw nuts threaded on ball threads of said first and second ball screw shafts, respectively, and is capable of being moved in the direction of injection together with said injection screw;
• a screw drive motor, which is mounted on said movable frame, for rotatively driving said injection screw;
• and
• a controller for synchronously rotating said first and second injection drive motors,
• said movable frame being moved so that a tensile force acts on said first and second ball screw shafts in an injection process.