Injection molding machine, injection molding apparatus, and injection molding method

An injection molding machine configured to cause a torpedo piston to slide inside a cylinder toward an opposite side of the cylinder to which an injection part is fixed to thereby plasticize a resin material supplied to a first space in the cylinder arranged on the side of the cylinder opposite to the side of the cylinder close to the injection part with the torpedo piston interposed therebetween among spaces of the first space and a second space in the cylinder arranged on the side of the cylinder close to the injection part, and to cause a molten resin to flow into the second space in the cylinder, and cause the torpedo piston to be slid toward the injection part inside the cylinder to thereby inject the molten resin from the injection part, the injection molding machine comprising:

• a pressurizing piston that is inserted into a sliding part formed in the torpedo piston so that the pressurizing piston can be slid in an axial direction of the cylinder in such a way that an amount of protrusion of the piston into the second space with respect to the torpedo piston is changed, and
• energizing means for energizing the pressurizing piston toward the second space of the cylinder with respect to the torpedo piston, wherein
• the pressurizing piston has a bottomed cylindrical shape with an end on the injection part side closed, an outer diameter thereof being equal to the inner diameter of the torpedo piston, and is inserted into the torpedo piston,
• the energizing means is made of an elastic body and is disposed inside the pressurizing piston, and when the torpedo piston is moved inside the cylinder to the opposite side of the cylinder to which the injection part is fixed in order to plasticize the resin material, the energizing means energizes the pressurizing piston in such a way that an amount of increase in the volume of the second space of the cylinder becomes equal to or smaller than an amount of decrease in the volume of the first space of the cylinder;
• and
• as the pressure of the molten resin flowing into the second space of the cylinder rises, when a force pushing the pressurizing piston in the opposite side to the injection part side exceeds a force of the energizing means by which the pressurizing piston is energized, the pressurizing piston is pushed in the opposite side to the injection part side.