JPH09293582A - Covered heater element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enhance power load density and make a covered heater element small by insulating a heat radiating metal pipe covering a covered layer from a terminal near the connection part between a heater element wire of the covered heater element and the terminal. SOLUTION: In a covered heater element 30, the outer circumference of a heater element wire 32 comprising a single wire is covered with a resin tightly contact covering layer 34, and its outer circumference is further covered with a second resin covering layer 36 having environmental resistance. The covered layers 34, 36 at one end of the heater element wire 32 are peeled off, and the exposed heater element wire 32 is loosely inserted into a through hole 40 of a terminal 38. A heat radiating metal pipe 52 covering the covered layer of the covered heater element 30 near the connection part 48 between the heater element wire 32 and the terminal 38 is insulated from the terminal 38, heat stored near the connection part 48 is radiated to liquid A or gas existing on the liquid A side. The local overheat of the resin covered layers 34, 36 of the covered heater element 30 is suppressed. As a method insulating the terminal 38 from the heat radiating metal pipe 52, an insulating heat resistant material is placed between them, and heating caused by existing of air is prevented to the utmost.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a coated heating element.

[0002]

2. Description of the Related Art A conventional coating heating element 10 for heating a liquid A is, as shown in FIG.
It is general that 4 is spirally wound and the resin coating layer 16 is further coated thereon. The structure of the terminal portion 15 is also as shown in FIG. That is, the one end of the heating element wire 14 that is exposed by stripping off the coating of the coating heating element 10 is inserted into the through hole of the terminal 18 and brazed to make the terminal portion 10.
Is formed. Reference numeral 19 denotes the terminal 18 and the coating heating element 1.
It is a fitting made of resin or the like formed to cover the end portion of No. 0, and is liquid-tightly attached to the covering heating element 10 and the wall portion of the container at the terminal portion 15.

[0003]

When the liquid A is heated by the coating heating element 10 as described above, the generated heat is absorbed more and more by the liquid A at the portion in the liquid A which is always in contact with the liquid A. Therefore, overheating can be suppressed. However, the heat generated in the vicinity of the connection portion between the coated heating element 10 and the terminal 18 is covered by the fixture 19, so that there is no place for the generated heat to escape and the heat is trapped inside the fixture 19.
Overheating tends to occur in the immediate vicinity of the connecting portion. Therefore, as a result of local overheating in the vicinity of the connecting portion, the resin coating layer 16 of the coating heating element 10 in the portion is carbonized or melted, and a withstand voltage defect occurs. Further, the fixture 19 is the liquid A.
And the outside air B are in contact with each other, and the portion in contact with the outside air B has poor heat dissipation efficiency and is likely to overheat. Especially the fixture 19
When the resin is molded with resin, the fixture 19 itself is also overheated, and like the resin coating layer 16 of the coating heating element 10, there is a risk of carbonization or melting. Therefore, the conventional coated heating element of this type cannot be used under the maximum power withstand load density assumed from the heat resistance of the resin coating layer 16, and is used with a safe power load density much lower than this. I had to do it. Therefore, in order to secure the necessary capacity, it was inevitable to use a long one, and there was a problem of increasing the size.

Further, in the structure in which the spiral heating element wire 14 is wound around the core body 12 in the coated heating element, since the heating wire element 14 exists as shown in FIG. 10, the core body 12 and the resin coating layer are present. A gap 20 is likely to occur between the gap 16 and the gap 16. Therefore, the void 2
As a result of 0 acting as a heat insulating layer and being locally heated, the resin coating layer 16 is carbonized or melted to cause a pressure resistance defect. Further, since the void 20 acts as a heat insulating layer, there is a problem that the heating efficiency is poor and the rise of temperature is particularly delayed.

Therefore, the present invention has been made to solve the above problems, and an object of the present invention is to provide a coated heating element having improved power load density, reduced size, and excellent temperature rising characteristics. is there.

[0006]

The present invention has the following constitution in order to achieve the above object. That is, in the coated heating element according to the present invention, the heating element wire is covered with the resin coating layer, and the end portion of the heating element wire is connected to the terminal. It is characterized in that a metal tube for heat dissipation is provided so as to be insulated from the terminal.
If this configuration is adopted, the heat generated in the vicinity of the connecting portion between the heating element wire and the terminal can be radiated from the metal tube for heat radiation into the liquid or the gas. Local overheating of the coating layer can be suppressed. Therefore, the coated heating element can be used with the maximum power load density, and the size can be reduced. As a method of insulation between the terminal and the metal tube for heat dissipation, an insulating heat resistant material is interposed so that heating due to the presence of air can be prevented as much as possible.

Further, the heating wire is formed of a single wire, and the resin coating layer is formed on the outer circumference of the heating wire.
It is also possible to provide a coated heating element including a first resin adhesive coating layer having a heat resistant insulation performance of 00 ° C. or higher and an environment resistant second resin adhesive layer formed on the outer periphery of the resin adhesive coating layer. it can. Since the heating element wire is provided with the resin adhesion coating layer, there is no gap between the heating element wire and the resin adhesion coating layer, and local heating due to this is avoided, so that use at high power load density is possible. The temperature rise characteristics can be improved by improving the heating efficiency by improving the heating efficiency.

The metal tube may be entirely coated on the resin coating layer. By adopting this structure, no external damage is caused and handling becomes easy.
Furthermore, by mixing a powder made of an inorganic material into at least one of the resin coating layers, the heat resistance insulation performance is further improved, and the coated heating element is excellent in strength.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION Preferred embodiments of the coated heating element according to the present invention will be described in detail below with reference to the accompanying drawings. FIG. 1 shows an embodiment of the coated heating element 30. The heating wire 32 made of a single wire is covered with a first resin adhesion coating layer 34 on the outer periphery thereof, and the second resin coating layer 36 having environment resistance is further covered on the outer periphery of the resin adhesion coating layer 34. ing. The first resin adhesion coating layer 34 and the second resin coating layer 36 are peeled off to expose one end side of the heating element wire 32, and one end side of the heating element wire 32 has the through hole 4 which the terminal 38 has.
Inserted loosely at 0. The heating wire 32 is provided with a brazing material 44 such as silver braze at the terminal end 42 of the terminal 38.
Have been brazed. Further, the brazing material 44 is used as the through hole 4.
It penetrates into the inside of 0 and fixes the terminal 38 and the heating element wire 32. Also, with the heating wire 32 inserted, the terminal 3
8 and the heating element wire 32 may be crimped by a method such as caulking. The crimping portion 46 is preferably a portion near the connecting portion 48. By crimping the crimping portion 46 near the connecting portion 48, the current flowing through the heating element wire 32 can be more surely flown to the terminal 38 having a low resistance value, and the heating element wire 32 inside the terminal 38 can be obtained. It is possible to suppress the heat generation amount. By setting the diameter of the terminal 38 to 2 to 3 times the diameter of the coated heating element 30 and using copper or the like having good conductivity, the heat generation amount of the heating element wire 32 in the terminal portion can be suppressed as described above. At the same time, the heat radiation effect can be improved, which is preferable.

Reference numeral 52 is a metal tube for heat dissipation, which is a connecting portion 48.
It is provided so as to cover the covering layer of the covering heating element 30 in the immediate vicinity and to be insulated from the terminal 38, and radiates the heat accumulated in the vicinity of the connecting portion 48 into the liquid A or the gas existing on the liquid A side.
Therefore, the metal tube 52 is preferably made of copper or the like having good thermal conductivity. Further, a resin tube 54 is further coated between the metal tube 52 and the second resin coating layer 36,
The insulation between the heat generating element 32 and the heat generating element 32 may be made more reliable. In addition, in order to prevent electric leakage, it is necessary to insulate between the metal tube 52 and the terminal 38. However, if there is a gap between the metal tube 52 and the terminal 38, this gap causes local heating, so there is no gap. As described above, it is preferable to insulate by interposing the insulating heat resistant material 56. As the insulating heat resistant material 56, it is preferable to use a heat resistant resin, and polyimide or the like can be used. Further, if there is even a slight gap between the insulating heat-resistant material 56 and the second resin coating layer 36, the gap will be locally heated as described above, so that the insulating heat-resistant material 56 is injected and filled with a paste resin. Then, it is preferable to form it by a method such as curing by curing or integrally molding by injection so that no void is formed.

The mounting member 58 includes the terminal 38 and the coating heating element 3.
It is formed so as to cover the end portion of No. 0, and the covering heating element 30 is liquid-tightly attached to the wall portion of the container at the terminal portion. The fitting 58 is made of synthetic resin, and is integrally molded or halved so as to cover the metal tube 52, the terminal 38, and the heat-resistant insulating material 56, and fastened with a fixing screw (not shown) or the like. You may Needless to say, the attachment 58 is not limited to the above.

According to the above-mentioned form, the heating wire 32
Since the heat generated in the vicinity of the connecting portion between the terminal 38 and the terminal 38 can be radiated from the metal tube 52 for heat radiation into the liquid A or the gas existing on the liquid A side, the resin coating layers 34 and 36 of the coating heating element 30. Local overheating can be suppressed. Therefore, the coated heating element 30 can be used with the maximum power load density, and the size can be reduced. Further, heat can be radiated to the outside air B through the terminal 38, and the resin coating layer in the connection portion with the terminal can be preferably protected by the heat radiation effect of both the metal tube 52 and the terminal 38. Further, as an insulating method between the terminal 38 and the metal tube 52 for heat dissipation, by interposing an insulating heat resistant material 56, overheating due to the presence of air can be prevented more suitably.

FIG. 2 shows a specific example of the structure of the heat generating portion of the coated heat generating element 30, and the embodiment of the structure of the heat generating portion will be described in more detail below. As the single heating element wire 32, an iron chrome wire, a nickel chrome wire, or the like can be used. Further, the heating wire 32 can be circular, elliptical, rectangular, or the like, and is not particularly limited in cross-sectional shape. The first resin adhesion coating layer 34 is made of polyimide, polyamide, polybenzimidazole resin or the like at 200 ° C.
It is formed of a resin having the above heat resistance. The resin adhesion coating layer 34 has a thickness of 25 μm or more, preferably 25 to 3
It may be formed to have a thickness of about 0 μm.

Further, the first resin adhesion coating layer 34 is obtained by applying the resin solution to the heating element wire 32 by, for example, dipping the heating element wire 32 in the resin solution of the resin dissolved in a solvent. After that, the coating layer forming treatment of drying with hot air to remove the solvent to form the coating layer is performed several times to several tens times (about 3 to 20 times).
It can be repeatedly formed into a coating layer having a desired thickness. As a result, a coating layer having no pinhole and having good adhesion to the heating element wire 32 can be obtained. Alternatively, the resin may be extruded on the heating wire 32 to a predetermined thickness to form the resin adhesion coating layer 34 on the heating wire 32.

Second resin coating layer 36 having environment resistance
Is formed on the outer periphery of the resin adhesion coating layer 34. The resin coating layer 36 is preferably provided with a fluororesin layer having a thickness of 50 μm or more. The fluororesin can withstand suitable use for a long time in water or air, and has excellent environmental resistance. When the resin coating layer 36 is other than fluororesin, for example, polyimide, it absorbs water when used in water,
Long-term use may result in poor insulation.

The results of the withstand load density when used in water are as follows. 25 W / cm ² of the above embodiment
In the case of the coated heating element 30 having a watt density (200 ° C.), the voltage resistance in water is 1500 V 1
Insulation broke in minutes. The coated heating element 30 having a watt density (145 ° C.) of 20 W / cm ² did not cause dielectric breakdown even after being immersed in water for 500 hours or more and energized. By the way, when a similar test was conducted using the conventional coated heating element 10 shown in FIG. 9, dielectric breakdown occurred at a watt density of 10 W / cm ² . It is considered that the cause is that the void 20 is generated as described above. Further, only the resin coating layer 36 made of a fluororesin layer is directly formed on the heating element wire 1
When a coated heating element having a watt density of 5 W / cm ² was manufactured and subjected to the same test, the insulation broke due to a withstand voltage in water of 1500 V for 1 minute.

As shown in FIG. 3, the result of measuring the time until the water temperature stabilizes in running water was about 5 seconds in the case of the coated heating element 30 of the present embodiment. It took 25 seconds for the coated heating element 10. In addition, the coated heating elements are adjusted to have the same capacity, and in the present embodiment, a coiled state is used, and both coated heating elements 10 and 30 are arranged in a glass pipe. The test was conducted with running water of / min.

The results used in air are as follows. In the case of the coated heating element 30 of the present embodiment, 0.9 W / cm ²
Deterioration was observed in the resin coating layer 36 (fluorine resin layer) at the watt density (180 ° C.). In the case of the coated heating element 10 shown in the figure, the watt density of 0.65 W / cm ² (150 ° C.)
Therefore, the fluororesin layer was deteriorated. In addition, the heating wire 32
For a coated heating element in which a fluororesin layer is directly formed on the
Deterioration was observed in the fluororesin layer at a watt density (165 ° C.) of W / cm ² . As described above, the coated heating element 30 of the present embodiment can be used with a higher power load density than the conventional one or the comparative example even when used in the air.

FIG. 4 shows a concrete form in which a metal tube is entirely coated on the coating layer of the coating heating element. Further, the same reference numerals used in the above embodiments will not be described.
Reference numeral 52 is a metal tube provided so as to cover the second resin coating layer 36. The metal tube 52 is preferably copper, which has excellent heat dissipation. Second
In order to form the metal tube 52 in close contact with the resin coating layer 36, it can be formed in the same manner as the sheathed heater by rolling a large diameter tube or drawing with a die. The outer diameter of the coated heating element 30 formed as described above can be various thicknesses such as 1 to 3 mm.

The results of the power withstand load density when used in water are as follows. 25 W / cm ² of the above embodiment
In the case of the coated heating element 30 having a watt density (200 ° C.), the insulation did not break even after being immersed in water for 100 hours and energized in water at 1500V. The coated heating element 30 having a watt density (145 ° C.) of 20 W / cm ² did not cause dielectric breakdown even after being immersed in water for 500 hours or more and energized. The reason why such a large power load density is obtained is that the metal tube dissipates heat evenly in water, so that local spots (voids) in the boiling boundary film are less likely to occur.
By the way, when a similar test was conducted using the conventional coated heating element 10 shown in FIG. 9, dielectric breakdown occurred at a watt density of 10 W / cm ² . It is considered that the cause is that the void 20 is generated as described above. A heater (without metal tube coating) having a watt density of 15 W / cm ² in which only the resin coating layer 36 made of a fluororesin layer was directly formed on the heating element wire 32 was manufactured and subjected to the same test.
The insulation broke due to the breakdown voltage of 1 minute in water.

As shown in FIG. 5, the result of measurement of the time until the water temperature stabilizes in running water was about 15 seconds in the case of the coated heating element 30 of the present embodiment, but the conventional method shown in FIG. It took 25 seconds for the coated heating element 10. It should be noted that the coated heating elements 30 and 10 are adjusted to have the same capacity. In the present embodiment, a coiled state is used. Both the coated heating elements 30 and 10 are glass pipes. It was placed inside and tested with running water of 1 l / min.

The results used in air are as follows. In the case of the coated heating element 30 of the present embodiment, 0.9 W / cm ²
No deterioration was observed in the resin coating layer 36 (fluorine resin layer) after continuous energization at the watt density (180 ° C.) for 100 hours. In the case of the coated heating element 10 shown in FIG. 9, 0.65 W /
Degradation was observed in the fluororesin layer at a watt density (150 ° C.) of cm ² . Further, in the coated heating element in which only the fluororesin layer was directly formed on the heating element wire 32, the fluororesin layer was deteriorated at a watt density (165 ° C.) of 0.8 W / cm ² .
As described above, the coated heating element 30 of the present embodiment can be used with a higher power load density than the conventional one or the comparative example even when used in the air. Further, since it is covered with the metal tube 52, scratches are less likely to occur even when an external impact is applied, and handling is facilitated.

FIG. 6 shows the second resin coating layer 36 of the coating heating element.
An embodiment in which an inorganic material is mixed in is shown. Further, the same reference numerals used in the above embodiments will not be described. In the present embodiment, the second resin coating layer 36 is mixed with powder made of an inorganic material such as magnesia, alumina, aluminum nitride, or glass. The mixing amount of these inorganic powders is preferably 30 wt% or less, and is not limited to one kind, and two or more kinds may be mixed and used. By mixing the inorganic powder, the heat resistant insulation performance is further improved and the strength is also excellent. Since the hardness of the second resin coating layer 36 increases, it is suitable when the metal tube 52 of a hard material such as stainless steel is formed by drawing. In addition, when aluminum nitride was mixed, the thermal conductivity was excellent, so the temperature rising characteristics were also improved. The other electrical characteristics were similar to those shown in FIG.

FIG. 7 shows an embodiment in which an inorganic material is mixed in the first resin adhesion coating layer 34 of the coating heating element. Further, the same reference numerals used in the above embodiments will not be described. In the present embodiment, in the first resin coating layer 34,
Powders made of an inorganic material such as magnesia, alumina, aluminum nitride and glass are mixed. The mixing amount of these inorganic powders is preferably 30 wt% or less, and is not limited to one kind, and two or more kinds may be mixed and used. By mixing inorganic powder, heat resistant insulation performance is further improved,
It is also excellent in strength. In particular, when aluminum nitride was mixed in, the thermal conductivity was excellent, so the temperature rise characteristics were also improved. The other electrical characteristics were similar to those shown in FIG. It is also possible to mix inorganic powder into both the first and second resin coating layers 34 and 36.

FIG. 8 shows an embodiment in which the second resin coating layer 36 is omitted from the configuration of FIG. 4 and the metal tube 52 is directly provided on the first resin coating layer 34. Also in this embodiment, since the first resin coating layer 34 is made of the same material as that described above, the adhesion with the heating element wire 32 is good and no gap is formed between the two. Similarly, excellent electrical characteristics can be obtained and a high power load density can be obtained. The resin coating layer is not limited to one layer and two layers, and may be provided in multiple layers of three or more layers.

Although the preferred embodiment of the heat generating portion has been described above with reference to FIGS. 2 to 8, it goes without saying that the structure of the heat generating portion is not limited to this, and the conventional heat generating portion as shown in FIG. 9 is used. Even in the parts, by disposing the metal tube on the resin coating layer, it is possible to radiate heat into the liquid through the metal tube. It can be used by increasing the load density accordingly.

Although various preferred embodiments of the present invention have been described above, the present invention is not limited to the above-described embodiments, and many modifications can be made without departing from the spirit of the invention. Of course.

[0028]

The coated heating element according to the present invention is a coated heating element in which a heating element wire is covered with a resin coating layer and an end of the heating element wire is connected to a terminal, and the resin is provided in the vicinity of the connection portion. Since the metal tube for heat dissipation is provided so as to cover the covering layer and to be insulated from the terminal, the heat generated in the vicinity of the connecting portion between the heating element wire and the terminal is transferred from the metal tube for heat dissipation into the liquid. Alternatively, heat can be radiated into the gas, and local overheating of the resin coating layer of the coating heating element can be suppressed. Therefore, the coated heating element can be used with the maximum power load density, and the size can be reduced. As a method of insulation between the terminal and the metal tube for heat dissipation, an insulating heat resistant material is interposed so that heating due to the presence of air can be prevented as much as possible.

Further, the heating wire is formed of a single wire, and the resin coating layer is formed on the outer circumference of the heating wire.
According to the coated heating element including the first resin adhesive coating layer having a heat-resistant insulation performance of 00 ° C. or higher and the environment-resistant second resin adhesive layer formed on the outer periphery of the resin adhesive coating layer, Since the resin adhesion coating layer is provided on the heating element wire,
No void is generated between the heating element wire and the resin adhesion coating layer,
Since local heating due to this is avoided, it can be used with a high power load density, downsizing can be achieved, and heating efficiency can be improved to improve temperature rising characteristics. Also,
By covering the entire resin coating layer with the metal pipe, no damage is caused and handling is facilitated.
Furthermore, by mixing a powder made of an inorganic material into at least one of the resin coating layers, the heat resistance insulation performance is further improved, and the coated heating element is excellent in strength.

[Brief description of drawings]

FIG. 1 is an explanatory diagram showing a configuration of a coated heating element according to the present invention.

FIG. 2 is an explanatory diagram showing a configuration of a mode in which two resin coating layers are provided.

FIG. 3 is a graph showing the temperature rising characteristics when used in water in the form of two resin coating layers.

FIG. 4 is an explanatory view showing a form in which a metal tube is covered on the entire coated heating element.

FIG. 5 is an explanatory diagram showing temperature rising characteristics when used in water with a metal tube covering the entire coated heating element.

FIG. 6 is an explanatory diagram showing a form in which an inorganic material is mixed in the second resin coating layer.

FIG. 7 is an explanatory diagram showing a form in which an inorganic material is mixed in the first resin adhesion coating layer.

FIG. 8 is an explanatory diagram showing a form in which a second resin coating layer is omitted and a metal tube is directly provided on the first resin adhesion coating layer.

FIG. 9 is an explanatory view showing a form of a conventional coated heating element.

FIG. 10 is a cross-sectional view of a conventional coated heating element.

[Explanation of symbols]

 30 coating heating element 32 heating element wire 34 first resin adhesion coating layer 36 second resin coating layer 38 terminal 40 terminal through hole 42 terminal end portion 44 brazing material 46 crimping portion 48 connection portion 52 metal pipe for heat dissipation 54 Resin Tube 56 Insulation and Heat Resistant Material 58 Fixture A Liquid B Outside Air

Claims (5)

[Claims] 1. In a coated heating element in which a heating element wire is covered with a resin coating layer and an end portion of the heating element wire is connected to a terminal, the resin heating layer is covered so as to radiate heat. The coated heating element, characterized in that the metal tube of (4) is provided so as to be insulated from the terminal. 2. The coated heating element according to claim 1, wherein an insulating heat-resistant material is interposed between the terminal and the metal tube for heat dissipation. 3. A first resin adhesion coating layer having heat resistant insulation performance of 200 ° C. or higher, wherein the heating wire is formed of a single wire, and the resin coating layer is formed on the outer periphery of the heating wire, and the resin. The coated heating element according to claim 1 or 2, comprising a second resin coating layer having environment resistance formed on the outer periphery of the adhesion coating layer. 4. The coated heating element according to claim 1, 2 or 3, wherein the entire metal tube is coated on the resin coating layer. 5. The coated heating element according to claim 1, wherein powder of an inorganic material is mixed into at least one of the resin coating layers.