JPH0755526B2 - Heating device for synthetic resin molding machines - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a heating device for a synthetic resin molding machine, and more specifically, heating a heating cylinder with a heater to heat and melt the synthetic resin in the heating cylinder. The present invention relates to a heating device for a synthetic resin molding machine.

(Prior Art) Conventionally, a synthetic resin molding machine is provided with a dedicated heating device for heating and melting a solid synthetic resin material, like the injection device 10 in the injection molding machine shown in FIG. .

In general, the injection device 10 of the injection molding machine is composed of a tubular heating tube 12 and a heater 22 provided in close contact with the outer peripheral surface of the heating tube 12.

The solid synthetic resin material sent from the hopper 20 into the heating cylinder 12 is heated and melted by the heat from the heater 22, and is heated and held at a desired temperature.
Ejected from 18.

In such melt molding, in order to obtain a uniform molded product, it is necessary that the melt viscosity and the like of the molten resin be uniform, and the temperature of the inner peripheral surface of the heating cylinder 12 that comes into contact with the synthetic resin is as low as possible. Needs to be uniform.

By the way, as the heater 22 for heating the heating cylinder 12, a band heater has been generally used.

As a band heater, usually, a heating wire such as a nichrome wire is wound around a strip-shaped heat-resistant electric insulating material, for example, mica, and the heat-resistant electric insulating material is laid on top of it. A heater wrapped in a shape is used.

(Problems to be Solved by the Invention) Since heating of the heating cylinder by the band heater uses conduction heat transfer, if the heating surface of the band heater and the outer peripheral surface of the heating cylinder are in close contact with each other. For example, the inner peripheral surface of the heating cylinder can be heated uniformly.

However, in reality, the ideal adhesion between the heating surface of the band heater and the outer peripheral surface of the heating cylinder is such that even if the tightening force of the band heater to the heating cylinder is increased, a non-uniform gap (clearance) is formed between the two surfaces. Remains and is impossible.

Such non-uniform residual clearance causes heating spots due to local heat storage on the heating surface of the band heater. Further, in the band heater, since the portion where the heating wire is not present is inevitable due to its structure, heating spots are likely to occur on the heating surface of the band heater.

Further, if the nonuniformity of the temperature of the heating surface expands due to the occurrence of such heating unevenness, the resistance value of the heating wire changes, and the nonuniformity of the temperature further expands.

As described above, according to the heating device of the conventional synthetic resin molding machine in which the band heater is heated by directly contacting the outer peripheral surface of the heating cylinder, it is extremely difficult to uniformly heat the inner peripheral surface of the heating cylinder.

Therefore, an object of the present invention is to provide a heating device of a synthetic resin molding machine capable of uniformly heating the inner peripheral surface of the heating cylinder.

(Means for Solving the Problems) The inventors of the present invention have conducted extensive studies to achieve the above-mentioned object, and as a result, heat from the band heater can be transferred to the heating cylinder through the ceramic layer that emits far infrared rays. They have found that the inner peripheral surface of the cylinder can be heated as uniformly as possible, and have reached the present invention.

That is, the present invention has a heating cylinder and a plurality of band-shaped heaters which are wound to be heated by contacting the outer peripheral surface of the heating cylinder with the inner peripheral surface, and heating and melting in the heating cylinder. In a heating device of a synthetic resin molding machine configured to inject or extrude a synthetic resin from the tip of the heating cylinder, at least the entire surface of the outer peripheral surface of the heating cylinder over the entire length of the region wound, It is characterized in that a ceramic layer that emits far infrared rays is fixedly formed.

The "far infrared" in the present invention has a wavelength of 25 to 5000μ.
Infrared rays of m are designated.

(Operation) According to the present invention, the inner peripheral surface of the heating cylinder can be heated to a temperature as uniform as possible. The detailed reason for this is not clear, but it is presumed as follows.

When the ceramic layer fixedly formed on the outer peripheral surface of the heating cylinder is heated by the heat of the band-shaped heater wound in contact with the outer peripheral surface of the heating cylinder on the inner peripheral surface, the ceramic layer is transferred to the conductive layer. The heating cylinder is heated by heat, and far infrared rays are emitted to heat the heating cylinder by radiation.

Since the heating by the radiation is performed by the ceramic layer fixedly formed on the outer peripheral surface of the heating cylinder, even if a clearance remains between the heating surface of the heater and the ceramic layer, or between the heater and the heater. Even if there is a gap between them, the heating cylinder can be heated efficiently and uniformly, and the inner peripheral surface of the heating cylinder can be made as uniform temperature as possible.

(Embodiment) A preferred embodiment of the present invention will be described in detail with reference to the accompanying drawings.

FIG. 1 is a vertical sectional view showing an embodiment of the present invention.

FIG. 1 shows an injection device 10 of an injection molding machine including a heating cylinder 12 having a cylindrical shape.

An injection nozzle 18 is connected to the tip of the heating cylinder 12, and molten resin heated and melted in the heating cylinder 12 is injected.

The rear end of the heating cylinder 12 is connected to the front end of the injection cylinder 16.

A hopper 20 for supplying synthetic resin into the heating cylinder 12 is provided near the tip of the injection cylinder 16.

The screw 14 that transfers the solid synthetic resin supplied from the hopper 20 toward the injection nozzle 18 is fitted inside the tip ends of the heating cylinder 12 and the injection cylinder 16.

On the outer circumference of the heating cylinder 12, a ceramic layer 24 that radiates far infrared rays is spray-coated and fixedly formed over the entire surface. The heating cylinder that is the outer peripheral surface of this ceramic layer 24
Three band-shaped heaters 22 are arranged adjacent to each other in the longitudinal direction of the heating cylinder 12 and wound on the outer peripheral surface of the heating member 12 so as to contact and heat the inner peripheral surface.

As the ceramic that covers the heating cylinder 12 and emits far infrared rays, known ceramics that emit far infrared rays, such as titanium oxide ceramics, alumina ceramics, magnesia ceramics, and zirconia ceramics, can be used. . In particular, a titanium oxide-based ceramic is suitable.

Further, on the heater 22, a heating wire such as a nichrome wire is wound around a strip-shaped heat-resistant electric insulating material, for example, mica,
A band heater is used in which heat-resistant electrical insulating materials are stacked and further wrapped in a metal plate into a band plate shape.

In the heating device shown in FIG. 1 having such a configuration, the heater 22 generates heat to heat the ceramic layer 24 by conduction and heat transfer.

Next, the heated ceramic layer 24 heats the heating cylinder 12 by conduction heat transfer, and also heats the heating cylinder 12 by radiating far infrared rays.

Since the heating by the radiation is performed by the ceramic layer 24 formed by being fixed to the outer peripheral surface of the heating cylinder 12 by thermal spraying, an uneven clearance remains between the heating surface of the heater 22 and the ceramic layer 24. Alternatively, even if there is a gap between the heaters, the heating cylinder can be efficiently and uniformly heated, and the inner peripheral surface of the heating cylinder can be made as uniform temperature as possible.

As shown in FIG. 2, the temperature distributions on the outer peripheral surface and the inner peripheral surface of the heating cylinder 12 in the heating cylinder 12 of this embodiment in which the heating due to the conduction heat transfer from the ceramic layer 24 and the heating due to the radiation can be used together. And shown in FIG.

The graphs shown in FIGS. 2 to 3 show a heating cylinder 12 having an inner diameter of 28 mm, an outer diameter of 105 mm, and a length of 535 mm in which a ceramic layer 24 having a thickness of 50 to 200 μm is formed by spraying a titanium oxide ceramic on the outer peripheral surface.
The outer peripheral surface of is heated by the heater 22, and changes in temperature of the outer peripheral surface and the inner peripheral surface with time are measured.

Here, the heater 22 is a band heater having a heat output of 2 KW, and is installed on the ceramic layer 24 of the heating cylinder 12 at a position where the end surface of the band heater is 150 mm from one end surface of the heating cylinder 12.

A voltage of 150 V is supplied to the band heater to heat the heating cylinder 12 for 180 minutes, and the temperatures of the inner peripheral surface and the outer peripheral surface of the heating cylinder 12 are 160 mm (A) and 200 mm from the end surface of the heating cylinder 12.
Measurements were made by thermocouples at positions (B), 240 mm (C), and 280 mm (D), and the results are shown in FIGS. 2 and 3.

FIG. 2 shows the temperatures on the outer peripheral surface of the heating cylinder 12, which are A to D.
There is a large variation in temperature at the position.

On the other hand, the temperature variation on the inner peripheral surface of the heating cylinder 12 shown in FIG. 3 is extremely small.

On the other hand, the ceramic layer 24 made of titanium oxide ceramic
In the conventional heating cylinder 12 shown in FIG. 5, in which the band heater is directly mounted on the outer peripheral surface without forming
The results of measuring the temperature distribution of the heating cylinder while heating under the same conditions as in this example are shown in FIGS. 6 and 7.

FIG. 6 shows the temperature distribution on the outer peripheral surface of the heating cylinder 12, and the degree of variation is the same as the variation on the outer peripheral surface of the heating cylinder according to this embodiment shown in FIG.

However, in the conventional heating cylinder 12, as shown in FIG. 7, the variation in the temperature distribution on the inner peripheral surface of the heating cylinder 12 is
Although it is slightly smaller than the variation of the outer peripheral surface of the heating cylinder 12, it is significantly larger than the variation of the inner peripheral surface of the heating cylinder 12 according to the present embodiment shown in FIG.

Thus, the temperature of the inner peripheral surface of the heating cylinder 12 can be made uniform because the heat of the heater 22 can be transferred to the heating cylinder 12 through the ceramic layer 24 by radiation. That is, the ceramic layer 24 is fixedly formed over the entire length of the outer peripheral surface of the heating cylinder 12, and the ceramic layer 24 is also provided in the gap between the adjacent heaters 22. , The entire heating cylinder 12, including the portion where the inner peripheral surface of the heater 22 is not in contact, can be efficiently and uniformly heated by the radiation of far infrared rays generated from the ceramic layer 24, and the temperature of the inner peripheral surface of the heating cylinder 12 can be increased. It can be made uniform.

When the ceramic layer 24 is formed by thermal spraying, since the ceramic is formed as an agglomerate of particles by thermal spraying, the surface area is 2 to 3 times that of a simple plate even if the thickness is thin, and therefore the emission efficiency of far infrared rays is increased. Is high. That is, the action of radiation of far infrared rays can be enhanced, and due to this property, the heating cylinder 12 can be heated more uniformly.

Further, when the ceramic layer is formed by thermal spraying, the ceramic layer 24 is thin (50 to 200 μm), so that the temperature response is fast and the heat is transferred quickly. This property also allows the heating cylinder 12 to be heated uniformly.

In this embodiment described so far, the heater 22 is installed so as to be in close contact with the ceramic layer 24.
As shown, a space may be formed by inserting a spacer 26 between the ceramic layer 24 and the heater 22. In this case, the heating of the ceramic layer 24 is mainly due to the radiation from the heater 22.

Therefore, in the heating device shown in FIG. 4, the heating of the ceramic layer 24 is uniformly heated as compared to the heating of the ceramic layer 24 caused by conduction heat transfer, as in the heating device shown in FIG. The temperature distribution on the inner peripheral surface of the heating cylinder 12 can be further homogenized.

In the embodiments described above, the example in which the ceramic layer 24 is coated on the outer peripheral surface of the heating cylinder 12 by thermal spraying has been described, but the ceramic layer 24 may be formed by coating or the like.

Since the ceramic layer can be formed by thermal spraying or coating, there is also an advantage that it can be easily manufactured without requiring many parts.

Furthermore, it goes without saying that the heating device of this embodiment can also be used as a heating device for an extruder.

The heating device of this embodiment can be used not only for a molding machine for thermoplastic synthetic resins but also for a molding machine for thermosetting synthetic resins.

(Effect of the Invention) According to the present invention, the ceramic layer is fixedly formed over the entire length of the outer peripheral surface of the heating cylinder, and the ceramic layer is also provided in the gap between the adjacent heaters. Therefore, it is possible to efficiently and uniformly heat the entire heating cylinder, including the portion where the inner peripheral surface of the heater is not in contact, particularly by the action of radiation of far infrared rays.

In this way, the inner peripheral surface of the heating cylinder can be heated as uniformly as possible, and the melt viscosity and the like of the molten resin can be made uniform, so that a uniform molded product can be obtained.

[Brief description of drawings]

FIG. 1 is a longitudinal sectional view showing an embodiment of the present invention, FIGS. 2 and 3 are graphs showing temperature distributions on the outer peripheral surface and the inner peripheral surface of the heating cylinder shown in FIG. 1, and FIG. FIG. 5 is a longitudinal sectional view showing another embodiment of the invention, FIG. 5 is a longitudinal sectional view showing a conventional example, and FIGS. 6 and 7 show temperature distributions on the outer peripheral surface and the inner peripheral surface of the heating cylinder shown in FIG. The graphs shown are each shown. In the figure, 10 ... Injection device, 12 ... Heating cylinder, 22 ... Heater, 24 ... Ceramic layer.

Claims (1)

[Claims] 1. A heating cylinder and a plurality of band-shaped heaters which are wound to be heated by contacting the outer peripheral surface of the heating cylinder with the inner peripheral surface, and heating and melting in the heating cylinder In a heating device of a synthetic resin molding machine in which a resin is injected or extruded from the tip of the heating cylinder, at least the entire surface of the outer peripheral surface of the heating cylinder over the entire length of the area around which the heaters are wound is A heating device for a synthetic resin molding machine, wherein a ceramic layer that emits infrared rays is fixedly formed.