JPH07148782A - Injection molding machine - Google Patents

Abstract

PURPOSE:To provide an injection molding machine by which the temp. of a molten resin is uniformed during a weighing process to obtain a molded product of high quality. CONSTITUTION:An opening and closing gate 20 for arbitrarily and freely changing the resin passing cross-sectional area of the resin discharge port 10a of a hopper 10 is provided to the resin discharge port 10a and the power means 30 of an opening and closing gate 20 for decreasing the resin passing cross-sectional area corresponding to the recession of a screw in a weight process to reduce a resin discharge amt. and a control unit are provided.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an injection molding machine for injecting and molding a molten resin in a mold, and particularly to an injection molding intended to keep the temperature of the molten resin at the same temperature in the measuring process. Regarding the machine.

[0002]

2. Description of the Related Art An injection molding machine, as shown in FIG. 3, has a nozzle 3 at its tip and a temperature adjusting device (heater 1) at its outer periphery.
It comprises a barrel 1 with 1). This barrel 1
It is arranged so that the nozzle 3 can face the material injection port of the die 4. The resin sent from the hopper 10 into the barrel 1 through the resin discharge port 10a is transferred from the material supply unit to the compression unit by the screw 2 which is rotationally driven by the motor 5, and the groove depth of the screw groove is formed in the compression unit. Is gradually compressed due to the gradual decrease. In this process, the resin between the flights 2a of the screw 2 is removed by the heater 11 from the barrel 1
The inner wall surface of the barrel 1 due to the heat transfer from the inner wall surface of the barrel 1 and the resin itself due to the rotating action of the screw 2 and the frictional heat generated between the resin and the barrel 1 or the screw 2 (generated by shearing energy). A melted film is formed on the surface of the screw 2 and is collected by the flight 2a to form a melt pool in the screw groove 2b. In this way, the resin in the barrel 1 in the process of promoting plasticization is composed of three parts of the melt film, the melt pool and the solid bed which has not reached the melting point yet, and these are accompanied by the rotation of the screw 2, During the forward transfer, the unmelted portion (solid bed) is continuously heated by the heater 11 and rotated by the screw 2.
Is converted into a melted portion (melt), and the unmelted portion is eliminated in the measuring portion of the screw 2 to obtain a homogeneous molten plasticized resin.

[0003]

However, in the plasticizing and measuring step of the injection molding machine, the resin pellets supplied to the hopper 10 enter the barrel 1 through the resin discharge port 10a, and the heater 11 from the barrel 1 is discharged. Since it is plasticized by the heat generated by the shearing heat generated by the rotation of the screw 2 and the rotation of the screw 2 and is sequentially stored in the void of the nozzle 3 at the tip, the screw 2 retracts as the storage amount increases. There was a problem that the residence time of the resin was different at the beginning and the end of the metering process, so that the molten resin temperature was not uniform. As a result, the quality of the resin injected into the mold is not constant, and the generation of defective molded products cannot be avoided.

[0004]

[Means for Solving the Problems] By solving the above problems,
In order to make the temperature of the molten resin injected into the mold uniform, in the present invention, in the injection molding machine equipped with a hopper for supplying the resin into the barrel, the resin discharge port of the hopper is cut off from the resin discharge port. An opening / closing gate whose area can be freely changed is provided, and power means and control for the opening / closing gate that reduces the resin discharge cross-sectional area and reduces the resin discharge amount in accordance with the backward movement of the screw in the plasticizing and measuring process of the injection molding machine. It is configured to include a device.

[0005]

In the present invention, an opening / closing gate whose resin passage cross-sectional area can be freely changed is provided at the resin outlet, and the opening / closing gate is operated and moved as the screw moves backward to control the amount of resin supplied into the barrel. Since the amount of heat received by the resin is controlled according to the change in the residence time, it is possible to keep the resin temperature substantially constant during or after the measuring process, as at the start of the measuring process. Therefore, a good molded product having a constant quality can be obtained.

[0006]

Embodiments of the present invention will be described below in detail with reference to the drawings. 1 and 2 relate to an embodiment of the present invention, FIG. 1 is a longitudinal sectional view of a main part of an injection molding machine, and FIG. 2 is a configuration diagram of an injection molding machine showing another embodiment. In FIG. 1, the opening / closing gate 20 capable of horizontal reciprocating movement is disposed in the resin discharge port 10a of the hopper 10 of the injection molding machine 100, and the resin passing cross-sectional area of the resin discharge port 10a is provided by the power means 30 of the opening / closing gate. Can be arbitrarily reduced or enlarged. The power means 30 is the rod 20 at the other end of the opening / closing gate 20.
a rack 30a attached downward to a and a rack 3 attached upward to a rod 2c fixed to the screw 2
0b and the pinion 32 are meshed with each other, and the opening / closing gate 20 advances automatically through the rotation of the pinion 32 in accordance with the backward movement of the screw 2, and the resin discharge port 10
It is configured to reduce the resin passage sectional area of a. On the other hand, in the one shown in FIG. 2, the opening / closing gate 20 is of a rotating type instead of the sliding type shown in FIG. 1, and the lever 26 is rotated by the operation of the hydraulic cylinder 40 to move the opening / closing pin 24 around the pin 24. It tilts to control the resin passage cross-sectional area of the resin discharge port 10a. In this case, screw 2
The position sensor 50 detects the retracted position of the control unit 60, transmits this position information to the control device 60 every moment, and sends a command to the hydraulic unit 70 by a preset program to operate the hydraulic cylinder 40 to tilt the opening / closing gate 20. To control.
In the case of FIG. 2, the hydraulic cylinder 40 is used as the power means 30, but an air cylinder may be used instead of the hydraulic cylinder. It is also possible to use hydraulic motors or other power mechanisms that convert rotary motion directly into linear motion.

Next, the operation of the present invention will be described. In the measuring process of the injection molding machine, as described above, the resin pellets supplied into the barrel 1 are heated by the heat generated by the rotation of the barrel 1 and the screw 2 as the measuring process progresses,
While being plasticized by the molten resin, it is stored in the space in front of the screw head 2 behind the nozzle 3 by the screw flight 2a, and at the same time, the screw 2 is pushed backward and moves backward, so The residence time is long, and the resin residence time at the end of the measuring process is short. Therefore, if the amount of resin supplied during the metering process is kept constant, the amount of heat received at the end will be less than that at the beginning,
The degree of temperature rise of the resin becomes low, which causes non-uniformity of the resin temperature in the entire measuring process. In the present invention, in order to reduce such non-uniformity of the resin temperature and to make the resin temperature uniform throughout the measuring process, in the embodiment of FIG.
The opening / closing gate 20 is slid forward to reduce the supply amount in conjunction with the retreat. As a result, since the supply amount also decreases in accordance with the heat receiving amount that decreases as the residence time decreases, the heat receiving amount of the resin per unit weight is kept constant and the resin temperature is kept uniform. Also in the embodiment of FIG.
According to the same idea, the retracted position of the screw 2 is detected via the position sensor 50 according to the decrease of the residence time, and this information is transmitted to the control device 60, which then controls the hydraulic pressure based on a predetermined program. An operation command is transmitted to the unit 70. As a result, the power means 30 having the hydraulic cylinder 40 changes the inclination angle of the opening / closing gate 20 to reduce the resin passage cross-sectional area of the resin discharge port 10a, thereby reducing the supply amount. The relationship between the inclination angle of the opening / closing gate 20 and the supply amount is desirably obtained by actually causing the resin pellets to naturally fall in advance. As described above, in the injection molding machine of the present invention, it is possible to remotely and automatically control the change in the supply amount that compensates for the change in the residence time due to the screw retreat during the metering process. It is possible to make the temperature of the molten resin supplied into the mold uniform.

[0008]

As described above, according to the present invention,
By homogenizing the resin temperature during the measuring step, a homogeneous molten resin can be supplied into the mold, so that a high quality molded product can be obtained.

[Brief description of drawings]

FIG. 1 is a longitudinal sectional view of an essential part of an injection molding machine according to an embodiment of the present invention.

FIG. 2 is a configuration diagram of an injection molding machine according to another embodiment of the present invention.

FIG. 3 is an overall vertical sectional view of a conventional injection molding machine.

[Explanation of symbols]

 1 barrel 2 screw 2a screw flight (flight) 2b screw groove 2c rod 3 nozzle 4 mold 5 motor 10 hopper 10a resin discharge port 11 heater 20 opening / closing gate 20a rod 24 opening / closing pin 26 lever 30 power means 30a rack 30b rack 32 pinion 40 Hydraulic cylinder 50 Position sensor 60 Control device 70 Hydraulic unit 100 Injection molding machine

Claims (1)

[Claims] 1. An injection molding machine equipped with a hopper for supplying a resin into a barrel, wherein an opening / closing gate is provided at a resin discharge port of the hopper, the opening / closing gate being capable of arbitrarily changing a resin passage cross-sectional area of the resin discharge port. An injection molding machine characterized by comprising power means for an opening / closing gate and a control device for reducing the resin passage cross-sectional area according to the backward movement of the screw in the plasticizing and measuring step of the molding machine to reduce the resin discharge amount.