JPH0414792A - Infrared ray heater - Google Patents

Abstract

PURPOSE:To prevent peeling-off while preventing generation of discharge between conductive films by forming a conductive film on the surface of a base body by a vapor growth method while being formed on the surface of an insulating base body with a spiral wiring pattern. CONSTITUTION:A heating element 12 consisting of a conductive film formed on the surface of the base plate 11 consists of a carbon group material such as graphite while being formed on the surface of this base body by a vapor growth method. The heating element 12 consisting of this conductive film is formed on the outer surface of the cylindrical base body 11 while forming a spiral wiring pattern and the conductive film 12 thereof is zonally formed. Accordingly, even when a thermal shock such as a mechanical shock and a rapid temperature change is applied, peeling-off of the conductive film is prevented, local heat generation due to peeling-off is prevented, temperature unevenness and deterioration in a heat generation characteristic is reduce while also preventing breaking of a wire.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial Application Field) The present invention relates to an infrared heater configured by providing a heating element made of a conductive film on the surface of an insulating substrate.

(Prior Art) For example, infrared heaters are used to dry food and various industrial parts.

As conventional infrared heaters used in such fields, heaters having structures as shown in FIGS. 3 and 4 are known. This device consists of a cylindrical base 1 made of insulating ceramic such as alumina, and a base 1 made of insulating ceramic such as alumina.
The heating element 2 is made of a carbon-based conductive film such as graphite formed on the surface of the cylindrical base 1, and a power supply terminal 3.3 is attached to the end of the cylindrical base 1.

The cylindrical base 1 is formed into a cylindrical shape by pressure molding and fired, and the heating element 2 made of a conductive film is attached to the outer surface of the cylindrical base 1 by sputtering or coating. has been done.

The heating element 2 made of the conductive film is formed in a band shape, and is formed in a meandering wiring pattern on the outer surface of the cylindrical base 1. Both ends of the heating element 2 in the meandering band shape A power supply terminal 3 attached to the end of the base 1.
Connected to 3.

Therefore, when the power supply terminal 3.3 is connected to a power source, a current flows through the heating element 2, which generates heat and emits infrared rays.

(Problems to be Solved by the Invention) However, in the case of the above conventional structure, the heating element 2 made of a conductive film such as graphite is attached to the surface of the cylindrical base 1 made of an insulating ceramic such as alumina. Since the conductive film 2 is simply attached by sputtering or coating, the adhesion strength of the film 2 is low, that is, the adhesive strength of the conductive film 2 to the substrate 1 is weak.

Therefore, when a mechanical shock or a thermal shock such as a sudden temperature change is applied, the conductive film 2 is likely to peel off. Especially 10
When the temperature exceeds 00° C., the conductive film 2 becomes extremely easy to peel off.

Such peeled parts may become locally high in temperature, causing temperature unevenness, or the peeled parts may evaporate due to the high temperature, resulting in increased resistance over time, or a decrease in heat generation characteristics in response to input. There are also problems such as wire breakage.

Further, the conductive film 2 is formed in a band shape and has a meandering wiring pattern in order to obtain uniform heat generation distribution over the entire surface of the cylindrical substrate 1.

In the case of such a wiring pattern, the ends of the meandering extend to the ends of the cylindrical substrate 1, resulting in a large potential difference between adjacent conductive films 2, and discharge between adjacent conductive films 2 or at each corner. This may occur.

Once a discharge occurs, discharge occurs many times at this location, and this discharge portion deforms and a large current flows locally, which invites further discharge and eventually destroys the conductive film 2. There is.

The present invention was developed based on the above circumstances, and its purpose is to strengthen the binding force of the conductive film to the substrate to prevent peeling, and to prevent discharge from occurring between the conductive films. It is an object of the present invention to provide an infrared heater which can easily form a uniform wiring pattern of a conductive film and which does not cause uneven heat generation.

[Structure of the Invention] (Means for Solving the Problems) The present invention provides an infrared heater in which a heating element made of a conductive film is attached to the surface of an insulating base having a cylindrical or cylindrical shape, wherein the conductive film is attached to the surface of the base. It is characterized in that it is formed on the surface of the insulating substrate by a vapor phase growth method, and a spiral wiring pattern is formed on the surface of the insulating substrate.

(Function) According to the present invention, since the conductive film is formed on the surface of the substrate by a vapor phase growth method, the binding force of the conductive film to the substrate becomes strong, and peeling can be prevented. In addition, the wiring pattern of the conductive film is spiral, making it easy to manufacture.
The potential difference between adjacent conductive films is reduced, preventing discharge, and the distribution of the conductive films tends to be uniform, reducing variations in heat generation distribution.

(Example) The present invention will be described below based on an example shown in FIGS. 1 and 2.

The basic structure of the infrared heater shown in the figure is the same as that of the conventional one, and 11 is an insulating cylindrical base, 12 is a heating element made of a conductive film formed on the surface of this base 11, and 13 and 13 are the above-mentioned cylinders. This is a power supply terminal attached to the end of the shaped base 11.

In the case of this embodiment, the heating element 1 made of the above-mentioned conductive film
The outer surface of 2 is covered with an insulating layer 20.

The cylindrical base 11 of this embodiment is made of an insulating ceramic such as boron nitride, and is manufactured by a vapor phase growth method.

The base body 11 formed by the vapor phase growth method of boron nitride has, for example, a perfect circular cylindrical shape with an inner diameter of 12 mm, an outer diameter of 14 am, and a length of 250 mm.

A heating element 12 made of a conductive film formed on the surface of the base 11 is made of a carbon-based material such as graphite, and is formed on the surface of the base 11 by vapor phase growth.

In the case of this embodiment, the heating element 12 made of the conductive film is formed in a spiral wiring pattern on the outer surface of the cylindrical base 11, and the conductive film 12 is formed in a band shape. In this case, the film thickness is 80 μm, and the width of the band is 2.011 μm.
The distance p between 1% adjacent bands is set to 5.0 Im.

The ends of such a helical conductive coating 13 are connected to power supply terminals 13.13 fixed to the ends of the base body 11. Note that the power supply terminals 13.13 are bonded to the base 11 using a conductive heat-resistant adhesive or the like.

The outside of the heating element 12 made of the conductive film is covered with an insulating layer 20 made of an insulating ceramic such as boron nitride, and this insulating layer 20 is coated by a vapor phase growth method.

The insulating layer 20 formed by this boron nitride vapor phase growth method has a film thickness of about 0.08 mm, and the cylindrical base 1
It is formed over a range of 230v in length along the axial direction of 1.

Note that a method for manufacturing such a heater will be explained.

First, the method for manufacturing the base body 11 will be explained.The diameter 11.
A core material made of carbon with a length of 5 mm and a length of 300+ am is prepared. This core material is placed in a container for vapor phase growth work, and the inside of this container is evacuated. The core material is heated to, for example, about 2000° C. in the container, and rotation is applied to the core material while maintaining this temperature. In this state, a small amount of boron trichloride (B
When Cjl13) and a small amount of ammonia (NH3) gas are injected, boron nitride is formed on the surface of the core material made of carbon by a chemical reaction, that is, by vapor phase growth. By continuing this for a predetermined period of time, a cylindrical shape of boron nitride having a wall thickness of about 1.25 mm is formed on the surface of the core material, for example.

By such a method, the core material on which boron nitride has been formed on the surface by vapor phase growth is taken out from the container for vapor phase growth work, and the core material made of carbon is cut out by lathe processing. In this case, the outer diameter of the core material is 11.5 mm,
Since the boron nitride base 11 has an inner diameter of 12a+i and an outer diameter of 14sffi, the carbon core material is scraped off and removed by the cutting process, and the inner surface of the boron nitride layer is slightly turned to the side, thereby reducing the inner diameter to 12mm. A cylindrical substrate 11 having an outer diameter of 14 am can be obtained.

By cutting this into a predetermined length, a cylindrical base 11 made of boron nitride is completed.

Next, the case of forming a conductive film as the heating element 12 will be described.

The surface of the cylindrical substrate 11 made of boron nitride obtained by the above vapor phase growth method is masked. This masking is performed by applying heat-resistant metal foil, such as molybdenum (M
o) Wrap the foil tightly.

The masked cylindrical substrate 11 is placed in a container for vapor phase growth work, and the inside of this container is evacuated. The cylindrical substrate 11 is heated to, for example, about 1800° C. in the container, and rotation is applied to the cylindrical substrate 11 while maintaining this temperature. In this state, a small amount of ethane or methane gas is injected into the container. .

Then, the cylindrical base 1 made of boron nitride
Carbon is formed on the surface of 1 by a chemical reaction, that is, by vapor phase growth. By continuing this for a predetermined period of time, a conductive heat generating film having a predetermined thickness, for example about 80 μm, is formed.

After that, the cylindrical base 11 on which the conductive heating coating was formed
was removed from the vapor phase growth work container, and the masked molybdenum foil was peeled off.

As a result, a spiral conductive film 12 is formed in the shaded area in FIG.

Furthermore, in order to produce the outermost insulating layer 20, the heater formed by the above manufacturing method is further placed in a container for vapor phase growth work, and the inside of this container is evacuated to a vacuum. The heater is heated to, for example, about 2000° C. in the container, and the heater is rotated while maintaining this temperature. In this state, a small amount of boron trichloride (BCN 3 ) and a small amount of ammonia (N
When the gas H3) is injected, boron nitride is formed on the surface of the heater by a chemical reaction, that is, by vapor phase growth. By continuing this for a predetermined period of time, an insulating layer 20 made of boron nitride with a thickness of 0.08 cm is formed on the surface of the conductive heating coating 12.

The operation of the heater having such a configuration will be explained.

When the power supply terminal 13.13 is connected to the power supply, the heating element 1
A current flows through the heating element 12, and the heating element 12 generates heat. In this case, the heating elements 12 are formed in a strip shape in a spiral pattern on the outer surface of the cylindrical base 11, and the pitch of the spiral is arranged at a predetermined constant interval, so that the distribution of the heating elements 12 is in the axial direction. and are uniform in the circumferential direction, and the heat generation distribution is also uniform.

In such an embodiment/example, the cylindrical substrate 11 is formed of boron nitride by vapor phase growth, so it is lighter than the conventional substrate 1. In other words, since the conventional cylindrical base 1 was made of alumina or the like by pressure molding and firing, the wall thickness was kept to a certain extent so as not to be damaged during the pressure molding and subsequent firing steps.

In contrast, the cylindrical substrate 11 of the embodiment is formed of boron nitride by vapor phase growth, so it can be formed thin and therefore lightweight.

If the cylindrical base 11 is thin and lightweight, it will be easy to handle and a lightweight heater will be realized.

The heating element 12 made of the conductive film of this example was formed on the surface of the cylindrical base 11 made of boron nitride by chemical reaction, that is, vapor phase growth, so that the binding force of the conductive film 12 to the base 11 was increased. Becomes extremely strong.

Therefore, even if a thermal shock such as a mechanical shock or a sudden temperature change is applied, the conductive film 12 is prevented from peeling off.

Therefore, local heat generation due to peeling is prevented, temperature unevenness and deterioration of heat generation characteristics are reduced, and wire breakage is also prevented.

Since the conductive film 12 is arranged in a spiral shape,
The distance between the conductive films 12 can be made constant, the potential difference between adjacent conductive films 12 can be reduced, and no corners are generated, so that no discharge occurs between the conductive films 12.

Further, since the conductive film 12 is arranged in a spiral shape, the distribution of the heat generating elements 12 can be made uniform in both the axial direction and the circumferential direction, making it easy to make the heat generation distribution even.

Furthermore, the spiral conductive film 12 can be easily formed by masking as described above, and is easy to manufacture.

Furthermore, since the conductive film 12 is covered with the insulating layer 20, the conductive film 12 is not exposed directly, and dust and dirt are prevented from adhering and accumulating on the surface of the conductive film 12.

Therefore, problems such as obstruction of infrared radiation due to dust and dust are prevented, and the conductive film 12 reacts with oxygen, resulting in an increase in resistance value, a decrease in temperature, and damage to the conductive film 12. Problems such as this will be resolved.

Further, since the conductive film 12 is protected by the insulating layer 20, problems such as the conductive film 12 being damaged during handling or the surface becoming dirty are also prevented.

Since the insulating layer 20 is formed by vapor phase growth, the adhesion strength to the cylindrical substrate 11 and the conductive film 12 is high, and there is no fear that the insulating layer 20 itself will peel off.

The results of experiments on the above heater will be explained.

Ten heaters having the structure of the above example were made, and a blinking test of 2 hours on and 30 minutes off with 2KW input was continued for 1000 hours.

In the conventional heaters shown in FIGS. 3 and 4, which had a meandering pattern, discharge was observed to occur by the time the heaters reached 1000 hours, and 8 of them were destroyed midway through.

On the other hand, in the heater of the present invention, all 10 heaters have 1000
Could withstand the lifespan of time.

In the above embodiment, the cylindrical substrate 11 is formed of boron nitride by vapor phase growth, which makes it possible to reduce the thickness and weight. The conductive coating heating element 1 is not limited to being formed from nitride.
If the conductive film 12 is formed on the surface of the substrate by chemical reaction, that is, by vapor phase growth, the conductive film 12 will be difficult to peel off from the substrate.

Furthermore, the conductive layer H12 is not limited to being covered with the insulating layer 20;
It may be housed in an airtight container filled with vacuum or inert gas.

The base body is not limited to a cylindrical shape, but may be a columnar shape.

[Effects of the Invention] As explained above, according to the present invention, the conductive film that serves as a heating element is formed on the surface of the substrate by vapor phase growth, so the adhesion of the conductive film to the substrate becomes strong and peeling is prevented. can do. Therefore, even if a mechanical shock or a thermal shock such as a sudden temperature change is applied, the conductive film is prevented from peeling off, local heat generation due to peeling is prevented, and temperature unevenness and deterioration of heat generation characteristics are prevented. This also reduces wire breakage and prevents wire breakage. In addition, since the conductive film has a spiral wiring pattern, it is not only easy to manufacture, but also has a small potential difference between adjacent conductive films and no corners.
Electric discharge is prevented from occurring at the corners, the service life is extended, and the heat generation can be evenly distributed in the circumferential and axial directions of the cylindrical or cylindrical base, making it easier to make the heat generation evenly distributed.

[Brief explanation of drawings]

1 and 2 show one embodiment of the present invention, FIG. 1 is a side view of the heater, FIG. 2 is a side view of the heater before coating with an insulating film, and FIGS. 3 and 4 are Showing the conventional structure,
Figure 3 is a side view of the heater, Figure 4 is IV-IV in Figure 3.
FIG. 11... Cylindrical substrate, 12... Conductive film, 13...
Terminal, 20...insulating layer. Applicant's agent Patent attorney Takehiko Suzue

Claims (2)

[Claims] (1) In an infrared heater in which a heating element made of a conductive film is provided on the surface of an insulating base having a cylindrical or cylindrical shape, the conductive film is formed on the surface of the base by a vapor phase growth method, and the insulating base is An infrared heater characterized in that a spiral wiring pattern is formed on the surface of the infrared heater. (2) The infrared heater according to claim 1, wherein the surface of the conductive film is coated with an insulating film.