JPH07282961A - Heater - Google Patents

Abstract

PURPOSE:To provide a low-cost heater presenting a high reliability, which excels in the heat resistance and has a good heat emission efficiency. CONSTITUTION:A heat emission layer 3 consisting of a carbonic mixture with a metal foil or carbon fibers is provided on an insulative layer 2 formed on the surface of a base material 1 by means of fusion spraying. and a covering layer 4 consisting of an electrically insulative, high heat conductive material is formed on the heat emission layer 3. A far-infrared ray generating substance layer 5 is formed on either or both surfaces of the heat, emission layer 3 by means of fusion spray or coating.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a heater for heating a fluid.

[0002]

2. Description of the Related Art A heater, which is a means of heating fluid,
As is well known, sheathed heaters, ceramics heaters,
Many types of silicon carbide heaters have been developed and used in various fields.

The sheathed heater is simple and inexpensive, and the ceramics heater and the silicon carbide heater are excellent in heat resistance and suitable for infrared heating.

Recently, there is a thin film heater using a silicone or fluorine type material. Here, a metal foil is used for the heating element, and both surfaces are covered with a resin-based insulating layer, which is excellent in weather resistance and chemical resistance.

Furthermore, a heater having a structure in which a heating element made of platinum or the like is screen-printed between alumina ceramic sheets and then integrally sintered has been developed, and since the heating element can be designed with a thin film to be dense and dense, a uniform heating is possible. The temperature can be secured.

[0006]

However, the sheathed heater has a drawback in that it has a low power density, poor heat resistance, and has a limit of up to 500 ° C., and is easily broken, especially at high temperatures.

Further, the ceramics heater and the silicon carbide heater are excellent in heat resistance as described above, and are about 12
Although it can withstand heat of 00 ° C., it is easily cracked, cannot be formed into a complicated shape, and its composition is not uniform, so that the amount of resistance varies.

A thin-film heater made of silicone or fluorine-based material and having a resin-based insulating layer on both sides of the heating element can withstand heat of about 300 ° C. because it is made of resin-based material. However, there is a problem that the power density is low.

Further, a heater having a construction in which platinum or the like is screen-printed between alumina ceramic sheets and integrally sintered is associated with reliability in bonding a heating element and a lead wire and a difference in thermal expansion coefficient between alumina and platinum. There are drawbacks such as peeling and platinum itself being expensive.

That is, the alumina ceramics have a problem that the insulating property remains uncertain, and there is a drawback that the material portion through which the current flows most deteriorates. The lead wire has its terminal fastened and connected to the heating element, but the terminal is easily oxidized, and thus the reliability of the joining is poor.

Therefore, the present invention has been proposed in order to solve the above-mentioned drawbacks, inconveniences, and problems of the prior art and to meet the demand, and is excellent in heat resistance and heat generation efficiency, inexpensive and reliable. Aims to provide a high heater.

[0012]

In order to solve the above-mentioned problems, the heater of the present invention has a heating layer formed of a metal foil on the surface of an insulating layer formed by thermal spraying on the surface of a base material, and an insulating high-heat layer is formed on the heating layer. This is a configuration in which a coating layer made of a conductive material is provided.

A heat-generating layer made of a metal foil is formed on the surface of the insulating layer formed by thermal spraying on the surface of the base material, and a coating layer made of an insulating high thermal conductive material is provided on the heat-generating layer, and at least one of the heat-generating layers is formed. The far-infrared generating material layer is sprayed or coated on the surface.

A mixture of carbon fiber and carbon may be used as the heat generating layer.

[0015]

The heater according to the present invention has the above-mentioned structure. Therefore, since the insulating layer formed on the surface of the base material is achieved by thermal spraying, even if the base material is a conductive material, it peels off against the difference in the coefficient of thermal expansion and the generation of thermal stress due to the turning on and off of the heater. It is also difficult to peel off the metal foil when used as a heat generating layer.

That is, the coating layer formed by thermal spraying is
Due to its characteristics, it becomes porous and crack-shaped, and absorption and relaxation of thermal stress can be expected, and since the surface becomes uneven, surface bonding with the base material or metal foil is reliable, a strong adhesive action works, peeling It becomes difficult.

When a metal foil is used as the heat generating layer,
The same product can be uniformly molded, and a desired form of processing for forming a patterned current path can be easily achieved.

That is, in order to obtain highly efficient heat generation, the heat generating layer serving as a current path is usually formed in a pattern, but if this heat generating layer is formed by, for example, thermal spraying. Although it is difficult and time-consuming to form the same shape, the heat generation characteristics of each product vary, but the above-mentioned metal foil solves such a problem.

Furthermore, since a metal foil is used as the heat generating layer,
The joining with the lead wire can be easily achieved by spot welding, the fastening work for joining the terminals can be omitted, the joining strength is extremely high, and further, the oxidation of the terminal portion can be prevented.

When a mixture of carbon fibers and carbon is used for the heat generating layer, this mixture has a higher resistance value than the metal foil, and therefore has a higher heat generating effect.

Since the coating layer made of the insulating and high thermal conductive material is provided on the heat generating layer, not only the safety is ensured, but also the high heat generated by the heat generating layer is radiated (removed) to the outside at a high rate. It is possible.

On the other hand, the Joule heat generated by energization is
It is important to quickly transfer heat to the object to be heated. If the transfer of heat is conducted, it is important that the overall heat transfer coefficient is large. Therefore, the thermal resistance between the layers is reduced.

Further, since the film thickness is thin, even if the ceramic has a small thermal conductivity, the heat transfer resistance is reduced. That is, since the effect of removing heat is great, it does not melt and break even if the power of the heat generating layer is increased.

Further, if the far infrared generating substance layer is sprayed or coated on at least one surface of the heat generating layer, far infrared heating can be achieved with high efficiency.

[0025]

The present invention will be described below with reference to the illustrated embodiments. The base material 1 has a capacitor structure when a metal-based material or a conductive material is used. If a capacitor is used, the use of a substance having a small dielectric constant in the insulating layer 2 will reduce the electrostatic capacitance, and thus the leakage current will be reduced.

Insulating layer 2 formed by thermal spraying on the surface of substrate 1.
Is alumina, gray alumina, silica, zircon, mullite, steatite, forsterite, titanium,
Cordierite, beryllica, magnesia, calcia,
Zirconia or the like may be used as a material, and a mixture thereof may be used.

Since the insulating layer 2 is formed by thermal spraying on the surface of the substrate 1, unevenness is formed on the upper surface thereof, which is shown by a wavy line in the drawing.

When the heat generating layer 3 formed on the upper surface of the insulating layer 2 is formed of a metal foil, the shape thereof can be freely selected because it is easy to process, and therefore, highly efficient heat generation can be obtained. In order to form a proper current path, not only a simple surface but also a pattern pattern of, for example, a meandering line may be used.

As a conventional concrete means for forming the heat generating layer 3 on the upper surface of the insulating layer 2, vapor deposition, printing or the like is often used, but in the illustrated embodiment, the heat generating layer 3 is shown linearly.
Are actually formed on the upper surface of the insulating layer 2.

The heat generating layer 3 formed on the upper surface of the insulating layer 2
In the drawing, if the upper surface of the uneven insulating layer 2 shown by the wavy line is exactly joined, the insulating layer 2 and the heat generating layer 3 are more likely to be separated due to the difference in expansion coefficient. Therefore, a slight gap is formed between the uneven insulating layer 2 and the heat generating layer 3 shown by the wavy line, which alleviates the difference in expansion coefficient and makes peeling difficult.

The material of the metal foil forming the heat generating layer 3 includes stainless steel, platinum, copper, brass, nickel, etc.,
Further, a mixture of these may be used.

Before the heat-generating layer 3 is mounted on the upper surface of the insulating layer 2, or in a state where the heat-generating layer 3 is mounted, a well-known far-infrared-generating substance layer 5 is sprayed on at least one surface of the heat-generating layer 3. Alternatively, high efficiency far-infrared heating can be achieved by forming a coating, but the formation of the far-infrared generating material layer 5 is selected according to the application.

A coating layer 4 made of an insulating high thermal conductive material is provided with the heat generating layer 3 mounted on the upper surface of the insulating layer 2 or with the far infrared generating material layer 5 sprayed or coated on the upper surface thereof. The above far-infrared ray generating substance layer 5 shown as a separate layer in the illustrated embodiment may be formed by mixing this substance with the coating layer 4.

When the heat generating layer 3 is mounted on the upper surface of the insulating layer 2, the upper surface of the heat generating layer 3 has uneven wavy lines corresponding to the unevenness of the upper surface of the insulating layer 2. Therefore, this wavy line is formed. Is used to form the coating layer 4 made of a paste-like insulating and high-conductivity material, so that the heat-generating layer 3 is firmly joined.

Examples of the insulating high thermal conductive material include boron nitride, aluminum nitride and the like. These paste materials are applied and coated, and baked and fixed in an electric furnace.

The lead wires 6 are spot-welded to the metal foil or the like which is the heat generating layer 3 at appropriate positions so that the electric current can flow in a preferable state, and the far-infrared radiation generated as described above is generated. The layer thickness from the insulating layer 2 including the material layer 5 to the coating layer 4 is within about 1 mm.

Further, FIG. 2 shows a schematic flow chart of one embodiment showing the manufacturing process of the heater of the present invention, but the present invention is not limited to this process, and for example, a metal foil which is the heat generating layer 3 is predetermined. A means for fixing with a jig and spraying the insulating layer 2 thereon may be adopted.

Although the heater of the present invention has a form in which the heat generating layer 3 is sandwiched between the insulating layer 2 and the coating layer 4 for safety reasons, it can be regarded as a heating source for an object to be heated such as fluid. The issue of heat transfer must be considered. Therefore, when designing the heater, it is necessary to consider the balance between the heat generation rate and the heat radiation (heat removal) rate of the heater, that is, the heating rate.

That is, it is important to increase the amount of heat generation (P) in order to improve the production efficiency, and for that purpose, the heat generating layer 3 is made of a metal system in which a large current (I) can be obtained from P = I ² R. Since it is necessary to use the metal foil, a metal foil that is thin, easy to process, and inexpensive is appropriate, and is appropriately selected from the materials described above.

When a metal foil is used as the heat generating layer 3 and stainless steel is used as the metal foil, the resistivity of this stainless steel is about 1/10 ⁴ Ωcm, and the heat generation efficiency is low because the resistance value is low. It has the advantage of being easy to process.

On the other hand, when a mixture of carbon fiber and carbon is adopted as the heat generating layer 3, the resistivity of this mixture is about 1/10 ¹ to 1/10 ² Ωcm,
High heat generation efficiency.

On the other hand, in consideration of heat radiation (removal of heat), it is a principle to use a material having a high thermal conductivity. However, when ceramics or the like as an insulating material is used, these substances are thermally conductive. Since the rate is small, it is important to reduce the layer thickness itself.

[0043]

The present invention is constructed as described above. Therefore, the base material and the insulating layer are difficult to be peeled off by thermal spraying, and the combination of the thermal spraying insulating film and the coating layer made of the insulating high thermal conductive material automatically encloses the thermal spraying film, and the heat cycle of the heater and the different materials When joining,
The thermal stress absorption action and the adhesive action of the thermal spray coating were reliably achieved, and the withstand voltage and insulation were further improved to improve reliability and safety.

Since the metal foil is used as the heat generating layer, products having the same characteristics can be easily achieved in the desired processing form, and the lead wires can be easily joined by spot welding with high strength.

When a mixture of carbon fiber and carbon is used for the heat generating layer, a material having high heat generating efficiency can be obtained.

Since the resin material is not used, or in addition, the far-infrared emitting material layer is sprayed or coated, the operating temperature range can be from -30 to 700 ° C. and high heat resistance can be obtained. Can be equipped with
Moreover, it is possible to manufacture at any power density.

Since the heater is a thin film as a whole,
The weight of the heater itself, that is, the heat capacity is small, which inevitably saves energy, and because the thermal spray coating is part of the thin film structure, it has excellent durability and can be manufactured in a mass-production process. Etc., and many excellent effects are achieved.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of a heater of the present invention.

FIG. 2 is a flowchart showing a manufacturing process of the present invention.

[Explanation of symbols]

1; substrate, 2; insulating layer, 3; heat generating layer, 4; coating layer, 5;
Far infrared emitting material layer, 6; lead wire.

Claims (3)

[Claims] 1. A heat-generating layer (3) made of a metal foil is formed on the surface of an insulating layer (2) formed by thermal spraying on the surface of a base material (1), and the heat-generating layer (3) is coated with an insulating high thermal conductive material. A heater comprising layers (4). 2. A heat-generating layer (3) made of a metal foil is formed on the surface of the insulating layer (2) formed by thermal spraying on the surface of the base material (1), and the heat-generating layer (3) is coated with an insulating high thermal conductive material. A heater comprising a layer (4), and a far-infrared ray-generating substance layer (5) formed by thermal spraying or coating on at least one surface of the heat generating layer (3). 3. The heater according to claim 1, wherein a mixture of carbon fiber and carbon is used as the heat generating layer (3).