JP2005235459A - Sheathed heater, its manufacturing method and heater - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a sheathed heater to minimize adverse effects due to difference of water quality and environment of use, while maintaining a good manufacturing property. <P>SOLUTION: The sheathed heater with an heating wire 2 is arranged inside a heater cylinder body 1, with a terminal body 3 taken out from an end of the heater cylinder body 1 connected to either end of the heating wire 2, and with the heater cylinder body 1 tapered after insulation powder 4 is filled inside the cylinder body 1. The heater cylinder body 1 has a double-tube structure consisting of an outer cylinder tube 7 and an inner cylinder tube 6 adhered to each other, and either one of the outer cylinder tube 7 or the inner cylinder tube 6 is structured of any one of stainless steel, anti-corrosion heat-resistant super alloy, and titanium, and the other is structured of copper. An end opening of the heater cylinder body 1 is sealed with a simple sealing material 5 not containing an airtight sealing material. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a sheathed heater used in various heaters such as an electric water heater, and more particularly to a sheathed heater effective for a bending process, a manufacturing method thereof, and an improvement of the heater.

Conventionally, in an electric water heater or the like, a sheath heater is provided in a storage tank, and water stored in the storage tank is heated by the sheath heater.
In this type of sheathed heater 120, for example, as shown in FIGS. 7A and 7B, a coil-shaped heating wire 122 is disposed in a metal pipe (heater cylinder) 121 and insulated in the metal pipe 121. Filled with magnesia oxide as powder 126, the metal pipe 121 is rolled to form a reduced diameter processed portion 121a, and both ends of the metal pipe 121 are sealed with a sealing material 128. Reference numerals 123 and 124 denote terminal bars connected to both ends of the heating wire 122.
Here, this type of sheathed heater 120 is not limited to a linear form, but, for example, as shown in FIGS. 7A and 7B, a form in which a desired shape is bent (bending portion) 121b) is also widely used.
As the metal pipe 121 of this type of sheathed heater 120, austenitic stainless steel such as SUS304 and SUS321, stainless steel such as ferritic stainless steel, corrosion-resistant heat-resistant superalloy, titanium, or copper has been widely used. (For example, see Patent Document 1).
Further, as shown in FIG. 7A, the sheathed heater 120 is attached by inserting the sheathed heater 120 into the mounting hole 161 of the mounting plate 160 according to the material of the metal pipe 121, for example, stainless steel. If it is, it fixes with the welding 162, and as shown in FIG.7 (b), if it is a copper pipe, the system fixed with the brazing 163 is used abundantly.

Japanese Unexamined Patent Publication No. Hei 6-260266 (Prior Art, Example, FIG. 1) Japanese Patent Laid-Open No. 6-267641 (Example, FIG. 1)

However, in this type of sheathed heater 120, for example, the sheathed heater 120 used in an electric water heater or the like has insufficient corrosion resistance of the metal pipe 121 due to the difference in water quality and usage environment in each region. The technical problem of being easy was found.
For example, in an embodiment in which an austenitic stainless steel pipe is used as the metal pipe 121, although high temperature strength and oxidation resistance are excellent, local corrosion such as stress corrosion cracking is likely to occur in a water environment where chlorine ions are present.
On the other hand, in the aspect using the copper pipe as the metal pipe 121, although it is excellent in corrosion resistance in a water quality environment where chlorine ions are present, a tendency to be inferior in corrosion resistance in an acidic water quality environment is seen. It is necessary to apply nickel plating.
Further, in the embodiment using a ferritic stainless steel pipe as the metal pipe 121, local corrosion such as stress corrosion cracking is effectively avoided even in a water quality environment where chlorine ions are present, but compared to austenitic stainless steel. Therefore, it tends to be inferior in terms of oxidation resistance, weldability, bending workability, etc., and inferior in terms of poor productivity compared to copper.
Further, as a conventional sheathed heater, for example, as shown in Patent Document 2, a metal pipe that employs a double pipe structure composed of an inner tube and an outer tube that are in close contact with each other is known. Both the inner tube and the outer tube are made of the same austenitic stainless steel (for example, SUS304), and are still inadequate in terms of corrosion resistance.
As described above, the various pipes that have been used as metal pipes have their merits and demerits, and users have strongly desired to provide metal pipes that do not take into account differences in water quality and usage environments in each region.

  In addition, when the metal pipe 121 filled with the insulating powder 126 is bent, an annealing process is usually performed, but the annealing temperature differs depending on the material of the metal pipe 121. When the annealing temperature is low, as the insulating powder 126, for example, magnesia oxide mixed with a silicone resin that is a moisture absorption preventing material is used to wet the interface of magnesia oxide and ensure water repellency. On the other hand, when the annealing temperature is high, even if a silicone resin that is a moisture absorption preventing material is mixed in magnesia oxide, the silicone resin is decomposed during the annealing process, and the water repellent function is lost. It becomes difficult to use magnesia oxide mixed with a moisture absorption preventing material.

Therefore, conventionally, in an embodiment in which, for example, a copper pipe is used as the metal pipe 121, the annealing temperature is as low as about 400 to 500 ° C. as shown in FIG. The mixed magnesia oxide can be used, and as the sealing process of the metal pipe 121, for example, a sealing material 128 made of silicone rubber 128a and insulating packing 128b can be used.
However, in an embodiment using, for example, austenitic stainless steel as the metal pipe 121, as shown in FIG. 7A, the annealing temperature is as high as about 1050 to 1100 ° C. It becomes difficult to use the mixed magnesia oxide. In this case, as a sealing process of the metal pipe 121, the opening of the metal pipe 121 is completely sealed with the glass sealing material 130, and further, the outside of the glass sealing material 130 is made of silicone rubber 128a and insulating packing 128b. It becomes necessary to seal with the next sealing material 128.
At this time, in order to perform the glass sealing, a process of heating and sealing the glass pellet to a temperature equal to or higher than the softening point is necessary, and in addition, an inspection process of whether or not it is completely sealed is necessary. Therefore, not only does the manufacturing cost increase, but the glass sealing material 130 is vulnerable to mechanical shock, and thus there is a technical problem that it requires careful handling.
Therefore, in the sheathed heater 120 that performs the bending process, there is a strong demand for selecting a metal pipe 121 that can be simply sealed without a hermetic seal such as a glass seal.

  The present invention has been made to solve the above technical problem, and a sheathed heater capable of minimizing adverse effects due to differences in water quality and use environment while maintaining good manufacturability and its A manufacturing method and a heater are provided.

  That is, in the present invention, as shown in FIG. 1, a heating wire 2 is disposed in the heater cylinder 1, and a terminal body 3 drawn from the end of the heater cylinder 1 is connected to both ends of the heating wire 2. In the sheathed heater in which the heater cylinder 1 is reduced in diameter after the insulating powder 4 is filled in the heater cylinder 1, the heater cylinder 1 is composed of an outer cylinder pipe 7 and an inner cylinder pipe 6 that are in close contact with each other. It has a double tube structure, and one of the outer tube 7 and the inner tube 6 is made of stainless steel, a corrosion-resistant heat-resistant superalloy and titanium, and the other is made of copper. 1 end opening was sealed with the simple sealing material 5 which does not contain an air-sealing sealing material.

In such technical means, this case is based on the premise that the heater cylinder 1 has been subjected to diameter reduction processing (referred to as a diameter reduction processing portion 1a), and is mainly configured to perform bending processing (mode including a bending processing portion 1b). ), But also includes a linear form without the bent portion 1b.
Further, the shape of the heating wire 2 may be linear or U-shaped, and the terminal body 3 may be either pulled out from both ends of the heater cylinder 1 or pulled out from one end side.
Furthermore, as the terminal body 3, a rod-shaped member is usually used, but any form may be used as long as it functions as a terminal electrode.
Furthermore, the insulating powder 4 insulates the heating wire 2 and functions as a heat conductive material for the heater cylinder 1, and a material having high heat conductivity such as magnesia oxide is preferable. In addition, the insulating powder 4 can increase the packing density by reducing the diameter of the heater cylinder 1, and can improve the thermal conductivity between the heating wire 2 and the heater cylinder 1.

  The heater cylinder 1 may be of a double tube structure. As a method of manufacturing the double tube, the outer tube 7 and the inner tube 6 may be fitted and adhered in advance, or the sheathed heater is being manufactured. Then, the outer tube 7 may be covered with the inner tube 6 and rolled. Further, either the outer tube 7 or the inner tube 6 may be copper or stainless steel. Here, the stainless steel widely includes austenitic stainless steel, ferritic stainless steel, and the like. Furthermore, instead of stainless steel, a corrosion-resistant heat-resistant superalloy or titanium may be used.

Furthermore, since an opening for filling the insulating powder 4 is secured at at least one end of the heater cylinder 1, the opening needs to be sealed in a subsequent process after the insulating powder 4 is filled.
In this case, the sealing process is sufficient with the simple sealing material 5. Here, the simple sealing material 5 may be any material as long as it does not include an air-sealing sealing material (such as a glass sealing material), and a combination of insulating rubber (for example, silicone rubber) and insulating packing (an insulator such as alumina porcelain) is appropriately selected. There is no problem.
At this time, since the sealing process is performed with the simple sealing material 5, it is preferable to prevent the insulating powder 4 from being hygroscopic (for example, magnesia oxide). Etc.) may be used. At this time, as an aspect including the moisture absorption preventing material, there are a case where a film is formed on the insulating powder 4 by heat by heat treatment, a case where the insulating powder 4 is coated in advance.

In particular, the present embodiment is preferably an embodiment in which the heater cylinder 1 is bent.
At this time, as a preferable manufacturing method of the sheathed heater to bend, after subjecting the rod-shaped sheathed heater intermediate molded product subjected to diameter reduction processing to an annealing temperature condition of at least less than 800 ° C., A bending process may be performed.
Here, the annealing temperature is the in-furnace atmosphere temperature of the annealing furnace, for example, by appropriately controlling the conveyor speed, the substantial annealing temperature and the in-furnace atmosphere temperature that substantially act on the intermediate molded product that is the object to be annealed. For example, there is a temperature difference of 200 to 300 ° C.

As described above, the annealing process is normally performed during the bending process of the heater cylinder 1, but the substantial annealing temperature that substantially acts during the bending process of the double-pipe structure according to the present embodiment is substantially the same as that of the copper single pipe. However, the temperature is not as high as that of an austenitic stainless steel single tube (about 1050 ° C.).
Therefore, in this case, since an annealing temperature of 400 to 500 ° C. is sufficient, it is possible to use the insulating powder 4 in which a moisture absorption preventing material (silicone resin or the like) for preventing moisture absorption is mixed with magnesia oxide. .

Moreover, as a preferable aspect of the heater cylinder 1, what is the double pipe structure of the outer cylinder pipe 7 which consists of either stainless steel, a corrosion-resistant heat-resistant superalloy, and titanium and the inner cylinder pipe 6 which consists of copper is mentioned. . Thus, if any of stainless steel, corrosion-resistant heat-resistant superalloy, and titanium excellent in oxidation resistance is the outer tube 7, it is rich in corrosion resistance to the outside air, and follows the copper inner tube 6 during bending. Thus, it is preferable in that it is easily bent and deformed.
Further, the thicknesses of the outer tube 7 and the inner tube 6 may be appropriately selected as long as they can constitute a double tube structure, but are selected from any of stainless steel, corrosion-resistant heat-resistant superalloy, and titanium. An embodiment in which the tube is thinner than the copper tube is preferred. Thus, if the stainless steel pipe or the like is thinner than the copper pipe, the stainless steel pipe or the like is preferable in that it is easy to bend and deform following the copper pipe.
Of course, even if the stainless steel pipe or the like is made thicker than the copper pipe, it does not matter if it can be bent and deformed.

  Furthermore, the present invention is not limited to the sheathed heater 8, but also includes a heater (including an electric heater and various other forms) in which the above-described sheathed heater 8 is incorporated.

According to the sheathed heater according to the present invention, since the aspect of the double tube structure of copper and stainless steel, any one of the corrosion-resistant heat-resistant superalloy and titanium is used as the heater cylinder, the copper tube and the stainless steel for corrosion resistance, The advantages of a pipe made of either a corrosion-resistant heat-resistant superalloy or titanium can be complemented with each other, and adverse effects due to differences in water quality or usage environment can be minimized.
In particular, in the present invention, the heater cylinder having a double-pipe structure can be bent by a low-temperature annealing treatment, so that the end opening of the heater cylinder can be sealed with a simple sealing material. For this reason, it is not necessary to carry out a sealing process including an air-sealing sealing material such as a glass sealing, so that the manufacturability of the sheathed heater can be simplified, and the handleability of the sheathed heater can be kept good. Can do.
Furthermore, according to the heater according to the present invention, since the reliability of the sheathed heater that performs the bending process can be increased, a highly safe heater can be simply provided.

Hereinafter, the present invention will be described in detail based on embodiments shown in the accompanying drawings.
Embodiment 1
Fig.2 (a) shows embodiment of the electric water heater incorporating the sheathed heater to which this invention was applied.
In the figure, an electric water heater 50 supports a storage tank 51 by a tank support leg 52, a hot water supply pipe 51a is connected to the upper part of the storage tank 51, and a water absorption pipe 51b is connected to the lower part thereof. The sheathed heater 20 is disposed in the storage tank 51, and the sheathed heater 20 is fixed to the outer wall of the storage tank 51 to heat the water contained in the storage tank 51.
Reference numeral 55 denotes a heat insulating material that covers the periphery of the storage tank 51 in order to keep the storage tank 51 warm.

  In the present embodiment, as shown in FIG. 2 (b), the sheathed heater 20 is inserted, for example, in a metal pipe 21 with coiled heating wires 22 having terminal rods 23 and 24 connected to both ends. While the terminal rods 23 and 24 are exposed to the outside from both ends of the metal pipe 21, the metal pipe 21 is filled with the insulating powder 26, and then the metal pipe 21 is subjected to a diameter reduction process to reduce the diameter reduction part 21a. And further bending is performed to form a bent portion 21b.

In the present embodiment, the metal pipe 21 has a double pipe structure composed of an outer cylinder pipe 32 and an inner cylinder pipe 31 that are in close contact with each other. The tube 32 is made of an austenitic stainless steel tube (for example, SUS304, Incoloy, etc.).
At this time, the thickness of the inner tube 31 and the outer tube 32 may be appropriately selected, but the thickness of the outer tube 32 made of an austenitic stainless steel tube is the wall thickness of the inner tube 31 made of a copper tube. It is set thinner. For example, an austenitic stainless steel pipe is 0.4 mm per 1 mm of copper pipe.

The heating wire 22 is usually disposed along the axis of the metal pipe 21, but is not limited to this, and may be arbitrarily disposed.
Furthermore, as the insulating powder 26, a material having good thermal conductivity is preferable. For example, magnesia oxide or the like is used. In this example, magnesia oxide having hygroscopicity is mixed with a silicone resin as a moisture absorption preventing material. in use.
Furthermore, in the present embodiment, both end openings of the metal pipe 21 are sealed with the simple sealing material 28. Here, the simple sealing material 28 refers to a sealing material that does not include an air-sealing sealing material such as a glass sealing material, and is sealed with, for example, a silicone rubber 28a as an insulating rubber and an insulating packing 28b made of an insulator such as alumina porcelain. Is.
In FIG. 2B, the sheathed heater 20 is inserted into the mounting hole 61 of the mounting plate 60 and fixed by, for example, welding 62.

Next, an example of a manufacturing process of the sheathed heater 20 according to the present embodiment will be described with reference to FIG. 3 (a) and FIGS.
When manufacturing the sheathed heater 20, first, as shown in FIG. 4 (a), a subassembly 25 in which terminal rods 23 and 24 are connected to both ends of the heating wire 22 is configured in advance, and a double tube The subassembly 25 is integrally inserted and arranged in a metal pipe 21 having a structure.
3A and 4B, the metal pipe 21 is filled with the insulating powder 26, and the terminal rods 23 and 24 are exposed to the outside at both ends of the metal pipe 21. A temporary stopper 27 (for example, insulating rubber or insulating paper) is applied in this state.
In this state, as shown in FIG. 3 (a), the metal pipe 21 is rolled (diameter reduction) to form a diameter reduction portion 21a (see FIG. 4 (c)).

Thereafter, the intermediate molded product of the sheathed heater 20 that has been subjected to diameter reduction is bent, and when this bending is performed, a low-temperature annealing treatment is performed as a pre-process as shown in FIG. In this low-temperature annealing treatment, the annealing temperature in the annealing furnace is set to a predetermined low-temperature annealing temperature, and the sheathed heater 20 intermediate molded product is placed and conveyed on a conveyor whose transport speed can be appropriately selected. The substantial annealing temperature that acts substantially on the surface is 400 to 500 ° C.
At this low temperature annealing treatment, the sheathed heater 20 intermediate molded product is treated at a substantial annealing temperature of 400 to 500 ° C., so that the silicone resin in the insulating powder 26 is melted by the heat and a film is formed on the surface of magnesia oxide. The film made of this silicone resin prevents magnesia oxide from absorbing moisture from the moisture of the outside air.
Then, after the bending process is performed, the temporary stoppers 27 at both ends of the metal pipe 21 are removed, and a sealing process using a simple sealing material 28 (silicone rubber 28a + insulating packing 28b) is performed as shown in FIG.

Further, as a comparative model, the manufacturing process of a sheathed heater (for example, an embodiment in which the metal pipe 121 is a single pipe of an austenitic stainless steel pipe) 120 subjected to bending as shown in FIG. ).
As shown in FIG. 7A, the sheathed heater 120 in this comparative model has terminal rods 123 and 124 connected to both ends of the heating wire 122, and these are integrally inserted into the metal pipe 121. The metal pipe 121 is filled with the insulating powder 126, and a temporary sealing material (for example, insulating rubber) is applied to both ends of the metal pipe 121 with the terminal rods 123 and 124 exposed to the outside.
In this state, as shown in FIG. 3B, the metal pipe 121 is subjected to rolling (diameter reduction process) to form a diameter reduction process part 121a.
Next, prior to bending, the metal pipe 121 is subjected to high-temperature annealing (for example, the annealing temperature in the annealing furnace is about 1050 to 1100 ° C.), and after the metal pipe 121 is softened, bending is performed. A bent portion 121b as shown in FIG. 7 (a) is formed.
Further, the temporary plugs at both ends of the bent metal pipe 121 are removed, the insulating powder 126 in the metal pipe 121 is dried, and an air-sealing port is provided by the glass sealing material 130 as a moisture absorption measure against the insulating powder 126. Thereafter, secondary sealing is performed with a secondary sealing material 128 (silicone rubber 128a + insulating packing 128b).

Thus, in the comparative form, in order to bend the metal pipe 121, it is necessary to perform a high-temperature annealing process at about 1050 to 1100 ° C. in advance, but at that time, silicone resin was mixed in When the insulating powder 126 is used, the silicone resin contained in the insulating powder 126 deteriorates and water repellency is lost.
For this reason, in order to reliably prevent moisture from the outside air, an air-sealing port such as a glass seal is required as the sealing process for the end of the metal pipe 121, which may increase the manufacturing cost.
In contrast, in the present embodiment, since the metal pipe 21 having a double pipe structure is used, even if the annealing process prior to the bending process is a low-temperature annealing process and the insulating powder 26 mixed with the silicone resin is used. Further, loss of water repellency due to deterioration of the silicone resin can be avoided.
In addition, since the water repellency can be maintained, it is not necessary to employ an air-sealing port such as a glass seal as a sealing process for the metal pipe 21, and the manufacturing cost can be reduced correspondingly.

Moreover, in the sheathed heater 20 according to the present embodiment, the inner cylindrical pipe 31 made of a copper pipe and the outer cylindrical pipe 32 made of an austenitic stainless steel pipe are provided in duplicate, so that it depends on the water quality and the use environment. Even if a part of the outer tube 32 is corroded, the presence of the inner tube 31 can compensate for the adverse effects caused by the corrosion of the outer tube 32.
In the present embodiment, since the austenitic stainless steel pipe is the outer cylindrical pipe 32, it is preferable in terms of excellent oxidation resistance. Also, during bending, the outer cylindrical pipe 32 is an inner cylindrical pipe made of a copper pipe. However, since the wall thickness of the outer tube 32 is set to be thinner than that of the inner tube 31, the bending deformation of the outer tube 32 follows the inner tube 31. It is preferable in that it is easy to do.

In the present embodiment, as shown in FIGS. 4A to 4D, the sheathed heater 20 is manufactured using a metal pipe 21 having a double pipe structure manufactured in advance. For example, as shown in FIG. 5A to FIG. 5D, after forming the sheathed heater 20 intermediate molded product with respect to the inner cylindrical pipe 31 made of a copper pipe, the outer cylindrical pipe 32. May be fitted.
In this modification, for example, as shown in FIG. 5 (a), a subassembly 25 in which terminal rods 23 and 24 are connected to both ends of a heating wire 22 in an inner tube 31 made of a copper tube is configured in advance. The subassembly 25 is inserted into the inner tube 31 as a unit.
Then, as shown in FIG. 5 (b), the inner cylindrical tube 31 is filled with the insulating powder 26, and at both ends of the inner cylindrical tube 31, the terminal rods 23 and 24 are exposed to the outside. 27 (for example, insulating rubber, insulating paper) is applied. In this state, the inner tube 31 is rolled (diametering) to form a diameter reducing portion 21a (see FIG. 5C).
Next, as shown by phantom lines in FIG. 5 (c), the outer cylindrical tube 32 is loosely fitted to the inner cylindrical tube 31 that has been reduced in diameter, and then the outer cylindrical tube 32 is rolled, whereby the inner cylindrical tube is rolled. The inner peripheral surface of the outer tube 32 is brought into close contact with the outer peripheral surface of the metal 31 to form a metal pipe 21 having a double tube structure (see FIG. 5D).
Each subsequent process (low-temperature annealing process, bending process, simple sealing process) is the same as that of the embodiment (see FIG. 3A).
As described above, according to the manufacturing method according to this modified embodiment, since the diameter reduction of the outer cylindrical tube 32 is small, work hardening is small, and further, since there is little residual stress, there is an advantage that bending work is facilitated. .

Embodiment 2
FIG. 6 shows a second embodiment of a sheathed heater to which the present invention is applied.
In the figure, the basic configuration of the sheathed heater 20 is substantially the same as that of the first embodiment, but includes a configuration of a metal pipe 21 different from that of the first embodiment. Components similar to those in the first embodiment are denoted by the same reference numerals as those in the first embodiment, and detailed description thereof is omitted here.
That is, in the present embodiment, the metal pipe 21 has a double tube structure including an outer tube 42 and an inner tube 41 that are in close contact with each other, and the inner tube 41 is an austenitic stainless steel tube (for example, SUS304). On the other hand, the outer tube 42 is formed of a copper tube.
At this time, the wall thickness of the inner tube 41 and the outer tube 42 may be appropriately selected, but the wall thickness of the inner tube 41 made of an austenitic stainless steel tube is the wall thickness of the outer tube 42 made of a copper tube. It is set thinner. For example, an austenitic stainless steel pipe is 0.4 mm per 1 mm of copper pipe.
In the present embodiment, the sheathed heater 20 is inserted into the mounting hole 61 of the mounting plate 60 and fixed by, for example, brazing 63.

Even in the present embodiment, the sheathed heater 20 is manufactured through a process as shown in FIG. That is, at the time of bending, the inner cylindrical pipe 41 made of an austenitic stainless steel pipe is bent and deformed following the outer cylindrical pipe 42 made of a copper pipe in a low temperature annealing process. Therefore, the simple sealing with the simple sealing material 28 is sufficient for the sealing process of the sheathed heater 20.
Also in the present embodiment, depending on the water quality and use environment, even if a part of the outer tube 42 made of a copper tube is corroded, the presence of the inner tube 41 causes the outer tube 42 to It is possible to compensate for harmful effects caused by corrosion.

In the first and second embodiments, as the metal pipe 21, a double pipe structure of a copper pipe and an austenitic stainless steel pipe is shown, but the metal pipe 21 is not limited to this, For example, a double tube structure of a copper tube and a ferritic stainless steel tube (for example, SUS444) may be used. Further, instead of the stainless steel pipe, a pipe made of a corrosion-resistant heat-resistant superalloy (see JIS G 4902: NCF600, NCF800, etc.) or titanium may be used together with a copper pipe to form a double pipe structure.
Even in these embodiments, the sheathed heater 20 can be manufactured in each step shown in FIG.
In such a case, for example, if the outer tube 42 is any one of ferritic stainless steel, corrosion resistant heat resistant superalloy, and titanium, the austenitic stainless steel according to the first embodiment is the same as the outer tube 32. It is preferable in that it has excellent oxidation resistance, and it is preferable in that the outer tube 42 is easily deformed following the inner tube 41 made of a copper tube during bending. In particular, in a mode in which the thickness of the outer cylindrical tube 42 is thinner than that of the inner cylindrical tube 41 made of a copper tube, the followability during bending deformation of the outer cylindrical tube 42 is better maintained.

It is explanatory drawing which shows the outline | summary of the sheathed heater which concerns on this invention. (A) is explanatory drawing which shows Embodiment 1 of the electric heater incorporating the sheathed heater which concerns on this invention, (b) is explanatory drawing which shows the detail of the sheathed heater used in Embodiment 1. FIG. (A) is explanatory drawing which shows the manufacturing process of the sheathed heater which concerns on embodiment model, (b) is explanatory drawing which shows the manufacturing process of the sheathed heater which concerns on the comparative form model. (A)-(d) is explanatory drawing which shows typically the example of a manufacturing process of the sheathed heater which concerns on embodiment model. (A)-(d) is explanatory drawing which shows typically the manufacturing process example of the sheathed heater which concerns on the deformation | transformation aspect of embodiment model. It is explanatory drawing which shows the sheathed heater which concerns on Embodiment 2. FIG. (A) (b) is explanatory drawing which shows an example of the conventional sheathed heater.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Heater cylinder, 1a ... Diameter reduction process part, 1b ... Bending process part, 2 ... Heating wire, 3 ... Terminal body, 4 ... Insulating powder, 5 ... Simple sealing material, 6 ... Inner cylinder pipe, 7 ... Outer cylinder Tube, 8 ... sheathed heater

Claims (7)

A heating wire is arranged in the heater cylinder, and a terminal body drawn from the end of the heater cylinder is connected to both ends of the heating cylinder. After the insulating powder is filled in the heater cylinder, the diameter of the heater cylinder is reduced. In the sheathed heater
The heater cylinder has a double pipe structure composed of an outer cylinder pipe and an inner cylinder pipe that are in close contact with each other, and either one of the outer cylinder pipe and the inner cylinder pipe is made of stainless steel, a corrosion-resistant heat-resistant superalloy, or titanium, The other is made of copper,
A sheathed heater, wherein the end opening of the heater cylinder is sealed with a simple sealing material that does not include an airtight sealing material. The sheathed heater according to claim 1,
A sheathed heater, wherein the heater cylinder is bent. The sheathed heater according to claim 1,
The sheathed heater is characterized in that the heater cylinder has a double pipe structure of an outer cylinder made of stainless steel, a corrosion-resistant heat-resistant superalloy, and titanium and an inner cylinder made of copper. The sheathed heater according to claim 1,
A sheathed heater, wherein the insulating powder includes a moisture absorption preventing material. The sheathed heater according to claim 1,
A sheathed heater in which a tube made of any one of stainless steel, a corrosion-resistant heat-resistant superalloy, and titanium is thinner than a copper tube among an outer tube and an inner tube of a heater tube. In the manufacturing method of the sheathed heater of Claim 2,
A method for manufacturing a sheathed heater, comprising subjecting a rod-shaped sheathed heater intermediate molded product subjected to diameter reduction processing to an annealing treatment under an annealing temperature condition of at least 800 ° C. and then bending.   A heater comprising the sheathed heater according to claim 1.

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