Screw, injection molding machine, and injection molding method

An injection molding machine to which a resin raw material is fed on an upstream side and to which reinforcing fibers are fed on a downstream side, the injection molding machine comprising:

• a cylinder at which a discharge nozzle has been formed;
• a screw provided rotatable and movable in a rotation axis direction inside the cylinder;
• a resin feed portion that feeds the resin raw material in the cylinder;
• and
• a fiber feed portion that is provided closer to a downstream side than the resin feed portion, and feeds the reinforcing fibers in the cylinder, wherein
• the screw comprises:
• a first stage at which the resin raw material which is fed is melted;
• and
• a second stage that continues to the first stage and comprises a feed portion and a compression portion closer to the downstream side than the feed portion, and at which the melted resin raw material and the fed reinforcing fibers are mixed with each other, wherein
• a flight provided at the feed portion in the second stage includes:
• a large-diameter flight with a relatively large outer diameter, and a small-diameter flight with a relatively small outer diameter;
• and
• a resin passage formed with a gap between a top portion of the small-diameter flight and the cylinder and in which a backflow of the melted resin raw material is generated from a screw groove of the downstream side toward a screw groove of the upstream side of the screw.

An injection molding machine to which a resin raw material is fed on an upstream side and to which reinforcing fibers are fed on a downstream side, the machine comprising:

• a cylinder at which a discharge nozzle has been formed;
• a screw provided rotatable and movable in a rotation axis direction inside the cylinder;
• a resin feed portion that feeds the resin raw material in the cylinder;
• and
• a fiber feed portion that is provided closer to a downstream side than the resin feed portion, and feeds the reinforcing fibers in the cylinder, wherein
• the screw comprises:
• a first stage at which the resin raw material which is fed is melted;
• and
• a second stage that continues to the first stage and at which the melted resin raw material and the fed reinforcing fibers are mixed with each other, wherein:
• a flight provided at the second stage is an intermittent flight in which a notch has been provided in a part of the flight so that continuity is lacked in a winding direction of the flight, the flight either comprising plural threads in which the number of the threads of the flight of the upstream side is more reduced than the number of the threads of the flight of the downstream side or provided with a phase thereof being displaced to an extension in the winding direction of the flight of the upstream side;
• and
• the flight includes a resin passage formed with the notch and in which a backflow of the melted resin raw material is generated from a screw groove of the downstream side toward a screw groove of the upstream side of the screw.

A method of feeding a resin raw material to a cylinder inside which a screw rotatable and movable in a rotation axis direction has been provided, also feeding reinforcing fibers closer to a downstream side than the resin raw material, and injection-molding the reinforcing fibers, wherein

• the screw includes:
• a first stage at which the resin raw material which is fed is melted;
• and a second stage that continues to the first stage and comprises a feed portion and a compression portion closer to the downstream side than the feed portion, and at which the melted resin raw material and the reinforcing fibers which are fed are mixed with each other, and
• in the feed portion of the second stage, the resin raw material is made to flow into a screw groove of an upstream side over a top portion of a flight provided at the screw.