JP2001006850A - Infrared heater - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an infrared heater wherein a heating body is arranged in an armoring body transparent for an infrared ray and for which devitrification is prevented from occurring in the armoring body. SOLUTION: This infrared heater is so structured that a thin-film SiO2-ZrO2 coating layer is formed on the surface of an armoring body 1 formed of a quartz glass pipe transparent for an infrared ray by using a solution obtained by a sol-gel method. By virtue of the structure, impurities never directly attach to the surface of the armoring body 1, so that the quartz glass pipe is prevented from causing devitrification.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an infrared heater in which an exterior body on which a heater wire is arranged is prevented from devitrification.

[0002]

2. Description of the Related Art Conventionally, as an exterior body of such an infrared heater, a tungsten wire spirally wound as a heating element in a quartz glass tube or the like and sealed with an inert gas as a filament, or a similar quartz glass pipe is used. A lamp generally called a halogen lamp heater (halogen heater for short) in which a tungsten filament is enclosed together with a halide, and a crystallized glass tube in which an Fe-Cr-Al wire coil is inserted are generally used.

[0003]

It is desirable that the outer body for inserting the heating element is heat-resistant and transparent to infrared rays as much as possible, that is, one having as high a transmittance of infrared rays as possible. For example, quartz glass can be cited from among many materials in consideration of the fact that it can be melted by heat for the purpose.

[0004] However, when a quartz glass pipe is used for the exterior body, particularly when used as a heating source of a heating cooker, foods, oils, and other seasonings are scattered and adhere to the surface of the quartz glass tube. Crystallization occurs in a short time, and countless minute cracks enter the surface of the glass pipe, resulting in a phenomenon in which the strength is reduced and the glass becomes white and tattered.

[0005] This phenomenon is devitrification. Generally, it is used for a long time at a high temperature lower than the melting temperature, or impurities adhere to the surface, in particular, alkaline earths such as Na, Ca and K form nuclei, and It has been introduced in many literatures that it has a great effect on devitrification in order to promote the growth of. When impurities are attached, devitrification occurs even at a low temperature. Therefore, it is the most important to prevent impurities from attaching to prevent devitrification of quartz glass and improve durability.

Due to the devitrification, there is a problem in that the strength of the glass tube is reduced and the heat permeability is deteriorated, the heating efficiency is reduced, and if the devitrification further proceeds, the glass tube is eventually broken.

[0007] In the case of quartz glass, although it has extremely excellent performance in terms of heat resistance, it tends to cause devitrification.
Heretofore, in the case of being used in a cooking cabinet or the like, the temperature cannot be increased too much, and the range of use has been limited.

Therefore, in the past, a heater using a quartz glass pipe for a cooker or the like cannot perform a surface treatment or the like to reduce the transmittance of infrared rays, and a guard is provided on the front surface of the heater to prevent dirt from adhering as much as possible. At present, special measures have been taken on the equipment side so as not to dispose or expose, and this has an effect on heating efficiency and heating performance.

[0009]

In order to solve the above-mentioned problems, the present invention is to form a thin film coating layer on a surface of an exterior body transparent to infrared rays using a material obtained by a sol-gel method. .

According to the above invention, the coating layer formed on the surface of the exterior body acts as a strong barrier layer to guard the exterior body surface, so that various impurities do not directly adhere to the exterior body, so that deterioration due to devitrification of the exterior body is prevented. Can be prevented.

[0011]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a perspective view of an external body which is transparent to infrared rays, a heating element disposed in the external body, and a lead wire connected to the heating element. An infrared heater comprising: SiO2 and a mixture thereof, ZrO2, Ti
A thin film coating layer made of one selected from O2 and AL2O3 is formed.

The thin coating layer is obtained by a sol-gel method.

With this structure, the coating layer on the surface of the exterior body is formed as a very thin and dense film, so that the surface of the exterior body is strongly guarded, and the exterior body is degraded without various impurities directly adhering. Can be prevented, and it can be used safely and safely even in the case of a cooker with severe dirt.

[0014]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a sectional view showing an infrared heater according to a first embodiment of the present invention, and FIG. 2 is an enlarged sectional view of a main part of the infrared heater.

In FIGS. 1 and 2, reference numeral 1 denotes an exterior body which is transparent to infrared rays, which is a transparent quartz glass pipe. An outer diameter of 10 mm and an inner diameter of 8 mm were used. A carbon heating element 2 is sealed in the quartz glass pipe 1 together with an inert gas such as argon or nitrogen.

The carbonaceous heating element 2 is made of a mixture of graphite, amorphous carbon, a resistance control filler, and the like, and the specific resistance can be adjusted by the mixing ratio of these. Here, it is 21800 μΩ · cm.

Reference numeral 3 denotes an internal lead wire.
One of them is provided with a spring coil 4 for absorbing the elongation in the longitudinal direction generated when the carbonaceous heating element 2 is energized and generates heat. Are formed.

The internal lead wire 3 is a tungsten wire having a wire diameter of 0.445 mm. The other of the internal lead wires 3 is connected to an external lead wire 7 at a lead wire connecting portion 6 of molybdenum foil and is led out. This part is a quartz glass pipe 1
Is heated and melted by a burner, and is pressurized from the periphery at the time of melting to be welded together with the lead wire connecting portion 6 to form a sealing portion 8. Thereby, airtightness inside the quartz glass pipe 1 is ensured.

A coating layer 9 of a SiO2-ZrO2 mixture is formed on the surface of the quartz glass pipe 1 using a sol-gel coating solution.

The coating layer 9 is obtained by a dipping method. As a treatment step, first, the quartz glass pipe 1 is washed with alcohol, degreased, and then SiO2-ZrO.
It is immersed in a two-mix sol-gel solution, pulled up, dried at room temperature, and baked in a 350 ° C. electric furnace for 20 minutes. At this time, the film thickness was about 0.25 μm.

Next, the operation and operation will be described.

When the infrared heater having the above configuration is energized, the carbonaceous heating element 2 generates heat and emits strong infrared rays.

At this time, the heating temperature of the carbonaceous heating element 2 is 120
It rises above 0 ° C. Naturally, the temperature of each part of the heater is also high, but there is no problem in heat resistance since both tungsten and molybdenum foil have high melting points.

The quartz glass pipe 1 is also brought into a high temperature state of 650 ° C. or more by the heat generated by the carbonaceous heating element 2.

When salt and various contaminants adhere to the quartz glass pipe 1 under such a high temperature, the portion becomes a nucleus and crystallizes to cause devitrification. Since the coating layer 9 made of SiO2-ZrO2 is formed on the surface, the quartz glass pipe 1
These do not directly adhere to the quartz glass pipe 1, and devitrification does not occur in the quartz glass pipe 1.

The barrier effect of the coating layer on devitrification was confirmed by the following experiment. A 50% aqueous edible salt solution is used as a devitrification promoting material on the surface of the quartz glass pipe 1 on which the coating layer 9 is formed.
The sprayed material was used as a test sample. And 500
An experiment was conducted in which the test sample was held for 100 hours in each electric furnace set at a temperature of 600C, 600C, and 700C.

[0028] The reason for using the fermented salt is that the contained glutamic acid has a great influence on the glass at high temperatures.

A similar experiment was carried out on an untreated quartz glass pipe.

As a result, in the case of no treatment, after 48 hours at 600 ° C., the pipe had numerous fine cracks and was markedly devitrified until it could be visually confirmed. Was observed.
Even at 500 ° C., the tendency of devitrification began to be recognized in part when the heating holding time was long.

On the other hand, the quartz glass pipe coated with SiO2-ZrO2 showed no change in appearance even after elapse of 500 hours at 700 ° C., and a superior coating effect was obtained without any decrease in strength.

In this embodiment, Na and Ca are used as contaminants.
Since the influence of alkalis and alkaline earths such as Mg is strong, a SiO2-ZrO2 mixture system is used. However, similar effects and effects can be obtained in the above-described devitrification test with SiO2, ZrO2, TiO2 and AL2O3. It is possible to arbitrarily select and use these materials.

According to the sol-gel method, the film is thin, and the film can be formed uniformly and easily. Therefore, it is extremely convenient particularly when used at a high temperature and when the surface of a pipe-shaped material is treated. It is almost impossible to form such a thin film by other coating methods.

Since the coating layer 9 is as thin as 0.25 μm and can be formed uniformly, it has been confirmed that peeling does not occur due to expansion and contraction due to repeated heating and cooling. Further, the coating is made of a material similar to that of the quartz glass pipe in terms of components, and has a similar thermal expansion, so that there is no problem in peeling. Since it is almost transparent to infrared rays, transmission of infrared rays does not decrease.

As described above, the structure of the present invention in which the coating layer of SiO2-ZrO2 is formed on the surface of the quartz glass pipe is an effective means for the stability of the infrared heater. This is a particularly effective means for a carbonaceous heating element that emits light.

In the above embodiment, a tungsten wire is used for the lead wire and a molybdenum foil is used for the lead wire connecting portion 6. However, other materials can be used as long as there is no problem in heat resistance and coefficient of thermal expansion. is there.

In addition, quartz glass is used as the outer package material because of its heat resistance, infrared ray transmission characteristics, thermal shock resistance, etc., and 96% silica glass or the like as another material has almost the same performance as quartz glass. And can be sufficiently used, and is not limited to only quartz glass.

[0038]

As described above, the infrared heater of the present invention has a coating layer formed by a sol-gel method on a quartz glass pipe which rises to a high temperature. Since the material is the same as that of the pipe, the coating does not peel off due to a difference in expansion coefficient due to repeated heating and cooling. Therefore, the quartz glass pipe enclosing the carbonaceous heating element does not devitrify and ragged from the surface, and the airtightness is impaired, and the carbonaceous heating element does not cause abnormalities. There is an effect that an infrared heater having high target value can be provided.

[Brief description of the drawings]

FIG. 1 is a sectional view of an infrared heater according to an embodiment of the present invention.

FIG. 2 is an enlarged sectional view of a main part of the infrared heater.

[Explanation of symbols]

 1 quartz glass pipe (exterior) 2 carbonaceous heating element (heating element) 9 coating layer

 ──────────────────────────────────────────────────の Continuing on the front page (72) Inventor Toshimitsu Komozawa 1006 Kadoma Kadoma, Osaka Prefecture Inside Matsushita Electric Industrial Co., Ltd. Term (reference) 3K092 PP03 QA01 QA02 QB14 QB24 QB60 QB71 RA03 RD11 SS35 SS36 SS37 VV09

Claims (3)

[Claims] 1. An infrared heater comprising: an exterior body that is transparent to infrared rays; a heating element disposed in the exterior body; and a lead wire connected to the heating element. SiO2 and its mixture or ZrO2, TiO
2. An infrared heater having a thin film coating layer formed of one material selected from AL2O3. 2. SiO2 and its mixture or ZrO
2. The infrared heater according to claim 1, wherein the coating layer of the thin film made of one material selected from the group consisting of TiO2 and ALO3 is formed by a sol-gel method. 3. The infrared heater according to claim 1, wherein the heating element is a carbonaceous heating element.