JPH01110119A - Method for controlling temperature of injection cylinder of injection molding machine - Google Patents

Abstract

PURPOSE:To accurately control the temp. of an injection cylinder by providing a heating medium flow passage to the outer peripheral part of the injection cylinder of an injection molding machine and allowing a heating medium whose temp. is controlled to a predetermined value to flow through said flow passage. CONSTITUTION:A control apparatus is constituted of a housing 2 arranged so as to cover the outer peripheral part of an injection cylinder 1, the heating medium 4 flowing through the space part (flow passage) 3 formed between the inner wall of the housing 2 and the outer wall of the injection cylinder 1, a heating medium temp. control part 5 setting the temp. of the heating medium 4 to a desired value and the tube 6 connecting the heating medium temp. control part 5 and the heating medium input part 2a of the housing 2 as well as the heating medium output part 2b of the housing and said heating medium temp. control part 5. The heating medium temp. control part 5 has a pump or recirculating the heating medium 4 mounted therein. By this constitution, the temp. of the injection cylinder can be accurately controlled.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to a method for controlling the temperature of an injection cylinder of an injection molding machine, and particularly for molding optical disk substrates that require highly accurate temperature control. , relates to a temperature control method for an injection cylinder of an injection molding machine.

(Prior art) In injection molding, the fluidity and viscosity of a resin during molding are factors that determine the quality of the product, and the properties of such resins are largely dependent on the resin temperature during injection. Therefore, it is necessary to accurately control the resin temperature, and for this reason, conventionally, the temperature of the injection cylinder was controlled to a desired value to control the temperature of the resin filled in the cylinder. The method of controlling the temperature of this injection cylinder to a desired value is to wrap a band heater around the outer circumference of the injection cylinder, apply a current to the band heater, and change the current to 0N10FF based on the temperature detected from the injection cylinder. Methods of controlling the temperature of injection cylinders are known.

In addition, as other conventional technology, the current is 0N10FF.
It is also known to control the amount of current instead, thereby controlling the temperature of the injection cylinder.

Furthermore, a method has also been proposed in which the filling conditions such as resin pressure and temperature within the mold cavity are detected to control molding (Japanese Patent Application Laid-Open No. 123081/1981).

(Problem to be Solved by the Invention) However, depending on the method of controlling the temperature of the injection cylinder through 0N10FF control of the current as described above, the cylinder temperature may exceed the above level due to the high thermal conductivity of the cylinder and band heater. The resin temperature cannot be accurately controlled because it changes greatly with switching between 0N10FF. Particularly in the molding of optical disk substrates, changes in resin temperature have an adverse effect on the optical properties of the substrate, especially the birefringence properties, and cause product quality deterioration. Development was considered a major issue.

Furthermore, in the above-mentioned method of controlling the temperature of an injection molding machine by controlling the amount of current and method of controlling molding by detecting the filling state in the mold cavity, the control equipment and components are expensive. However, there is a problem in that the manufacturing cost is high.

The present invention has been made to solve the above problems, and provides an injection molding machine that can accurately and inexpensively control the temperature of the injection cylinder of the injection molding machine, and by extension, the temperature of the resin filled in the injection cylinder. The object of the present invention is to provide a method for controlling the temperature of an injection cylinder.

(Means for Solving the Problems) A method for controlling the temperature of an injection cylinder of an injection molding machine according to the present invention is to provide a flow path through which a heat medium can flow in the outer circumference of the injection cylinder, and to set a temperature in this flow path. The invention is characterized in that the temperature of the injection cylinder is controlled by continuously flowing a controlled heating medium.

The flow passage may be formed so that the heat medium can be in direct contact with the cylinder outer circumference or indirectly through the flow passage wall and can always flow along the cylinder outer circumference, for example. The outer periphery of the cylinder may be covered with a housing provided with an input part and an output part for the heat medium, and the gap between the housing and the outer wall of the cylinder may be used as a flow path, or the outer periphery of the cylinder may be wrapped with a tubular material through which the heat medium flows. This hose-like material may be used as a flow path.

(Effects of the Invention) According to the method for controlling the temperature of an injection cylinder of an injection molding machine of the present invention, the temperature of the cylinder is controlled by continuously flowing a temperature-controlled heat medium through the flow path provided on the outer periphery of the injection cylinder. The temperature of the injection cylinder will be sequentially controlled by the newly lengthened heat medium, and the outer circumference of the injection cylinder will be insulated from external temperature changes by the heat medium. Compared to a method using 0N10FF control of a band heater, the temperature change of the injection cylinder is gentler, there are fewer ripples, and the temperature of the injection cylinder can be accurately controlled.

Furthermore, compared to the above-described method of controlling temperature by controlling the amount of current, this method does not require a complicated control section, so the manufacturing cost is low.

(Embodiments) Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings.

FIG. 1 is a sectional view showing an example of an injection cylinder temperature control device for carrying out the method of the present invention. 1st
The control device shown in the figure includes a housing 2 disposed so as to cover the outer periphery of an injection cylinder 1, and
A heat medium 4 flowing through a space (flow path) 3 formed between the inner wall of the injection cylinder 1 and the outer wall of the injection cylinder 1; a heat medium temperature control unit 5 that sets the temperature of the heat medium 4 to a desired value; Between the heat medium temperature control section 5 and the heat medium input section 2a of the housing 2, and between the heat medium output section 2 of the housing 2.
b and the heat medium temperature control section 5, and the heat medium temperature control section 5 has a built-in pump for circulating the heat medium 4.

Further, the control by the heating medium temperature control unit 5 may be feedback control in which the temperature of the injection cylinder 1 or the plastic material in the injection cylinder 1 is detected and the heating medium temperature is changed based on this detected temperature. desirable. Note that a screw 7 is tightly inserted into the hollow part of the injection cylinder 1, and the thread trough 7a of this screw 7 is filled with molten plastic material, and the screw 7 is rotated in the direction of arrow A. The plastic material in the thread trough 7a is conveyed to the special injection unit 8 in front of the screw 7, and when the injection unit 8 is filled with the plastic material in the injection amount for - batches, the rotation of the screw 7 is stopped. Then, the screw 7 is pushed forward (in the direction of arrow B) inside the injection cylinder 1, and the plastic material in the injection special part 8 is injected to the outside of the injection cylinder 1 through the injection hole 9. It has become so.

By the way, the fluidity and viscosity of resins such as plastic materials change greatly depending on their temperature, and such changes in fluidity and viscosity can cause quality deterioration, especially when molding optical disk substrates, etc. Therefore, depending on the resin temperature, It is necessary to control the temperature of the injection cylinder, which affects the injection cylinder. Therefore, in the above-mentioned device, the temperature-controlled heat medium 4 is configured to circulate and flow through the heat medium flow path 3 formed between the housing 2 and the outer circumference of the injection cylinder 1. The temperature, and thus the temperature of the plastic material filled in the injection cylinder 1, can be stably controlled.

That is, the heat medium 4, which has been set to a desired temperature by the heat medium temperature control section 5, is transferred to the flow path 3 through the tube 6 and the heat medium input section 2a of the housing by the pump provided in the heat medium temperature control section 5. It is sent out to the rear part of the injection cylinder 1, flows along the outer circumference of the injection cylinder 1 through the flow path 3, and returns to the heat medium temperature control part 5 via the heat medium output part 2b of the housing 2 and the tube 6. As a result, the temperature-controlled flowing heat medium 4 is always in contact with the outer circumference of the injection cylinder 1, and the temperature of the injection cylinder 1 and the amount of plastic material in contact with the inner wall of the injection cylinder 1 are increased. The temperature will be controlled. This heat medium is preferably a liquid such as heat-resistant oil that exhibits fluidity at a desired temperature (for example, 300° C. or higher).

Next, FIG. 2 is a sectional view showing a part of a temperature control device for carrying out the embodiment method of the present invention when it is necessary to provide a temperature distribution to the injection cylinder.

That is, the device shown in FIG. 2 has an annular protrusion disposed on the inner wall of the housing 2, which extends around the entire circumference of the inner wall.
This protrusion is configured to come into contact with the outer circumference of the cylinder and function as a separate part of the flow path. A plurality of flow paths are formed by the protrusions that function as separators, and the heat medium 4 controlled at a different temperature is flowed through each flow path, so that the injection cylinder 1 has a desired temperature distribution in its front and back direction. Set to . The device shown in FIG. 2 is provided with two projections 12a and 12b in the front and back direction of the injection cylinder 1, thereby forming three flow passages 13a, 13b and 13C. Note that an input portion and an output portion for the heat medium are formed in the housing 12 for each of the flow passages 13a, 13b, and 13c.

FIG. 3 shows an example of a modification of the housing of the device shown in FIG. 1. When the housing is attached to the injection cylinder 1, the central axis extends in the longitudinal direction of the cylinder on the outer circumference of the injection cylinder 1. FIG. 3 is a cross-sectional view showing a housing 22 in which a spiral groove 22a whose central axis extends in the longitudinal direction of the cylinder is provided in the inner wall so as to form a spiral flow path.

FIG. 4 also shows an example of a modification of the housing of the device shown in FIG. FIG. 3 is a sectional view showing a housing 23 in which a groove 23a is provided on the inner wall so as to surround the outer periphery of the cylinder while reciprocating in the cylinder front-rear direction so as to form a flow path arranged in the cylinder.

A housing 22 as shown in FIGS. 2 and 3
．． Even when using a temperature control device having 32, the temperature of the injection cylinder 1 can be controlled in the same way as when using the device shown in FIG.

In addition, in the above description, the flow path for the heat medium is formed by providing a groove in the inner wall of the housing, but instead of this, a groove is provided in the outer peripheral part of the injection cylinder,
The groove portion may be covered with a sheet or the like to form a flow path, and the temperature of the injection cylinder may be controlled by flowing a heat medium through the flow path. Alternatively, a tube made of a material with good thermal conductivity may be wrapped around the outer periphery of the injection cylinder, and the temperature of the injection cylinder may be controlled by flowing a heat medium through the protection tube.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view showing a temperature control device for carrying out an embodiment method of the present invention, and FIG. 2 is a sectional view showing a temperature control device for carrying out the embodiment method when providing a temperature distribution in the front and back direction of an injection cylinder. Control. - A sectional view showing a small device; FIGS. 3 and 4 are sectional views showing a modification of the housing of the device shown in FIG. 1; 1... Injection cylinder 2.12.22.32... Housing 3, 13a, 13b, 13cm... Flow path 4... Heat medium 5... Heat medium temperature control section 12a, 12b -... protrusion

Claims (1)

[Claims] 1. A method for controlling the temperature of an injection cylinder of an injection molding machine, comprising: providing a heat medium flow path on the outer periphery of the injection cylinder of the injection molding machine; and flowing a heat medium whose temperature is controlled to a predetermined value through the flow path.