Molten-resin extrusion device and extrusion method as well as molten resin molding machine and molding method

A molten-resin extruder comprising:

• an accumulator extending vertically and provided with a space coupled to a head, the head having an extrusion port at a lower end thereof, the accumulator including a core configured to adjust opening area of the extrusion port;
• a piston that is fitted to the space and is able to move vertically in the space, wherein a charging space into which a molten resin can be charged is formed under the piston in the space;
• a shaft inserted into the core of the accumulator, the shaft configured to move the core upward and downward to adjust the opening area of the extrusion port;
• a lower plate disposed over the accumulator and coupled to the piston from above;
• a level detector configured to detect a level of the lower plate;
• a screw shaft that extends vertically;
• an electric motor configured to rotationally drive the screw shaft;
• a nut secured to the screw shaft and capable of making a vertical linear motion along the screw shaft, wherein the screw shaft is rotated around a vertical direction by the electric motor;
• and
• an upper plate coupled to the nut and disposed over the lower plate so as to be able to surface-contact the lower plate, wherein
• the molten-resin extruder comprises only one upper plate, and
• the upper plate and the lower plate respectively include openings through which the shaft passes,
• after the upper plate is retracted upward by the electric motor, the molten resin is charged into the charging space while applying back pressure based on a self-weight of the lower plate to the molten resin in the charging space, and the charged molten resin is extruded from the extrusion port downward.