JPS62287585A - Sheathed heater - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] 3. Detailed Description of the Invention Industrial Application Field The present invention relates to a type of sheathed heater impregnated with silicone oil, among sheathed heaters widely used as a heating source. be.

BACKGROUND ART Conventionally, sheathed heaters have been widely used as a heating source for general cooking appliances such as toaster ovens, microwave ovens, rice cookers, and hot plates.

In general, a sheathed heater consists of inserting a coiled heating wire with terminal rods at both ends into the center of a metal pipe, filling the metal pipe with electrically insulating powder made of fused magnesia powder, and then inserting the metal pipe into the metal pipe. Manufactured by rolling to reduce diameter.

In order to use fused magnesia powder, which is highly hygroscopic, as the electrical insulating powder, the following various methods have been considered.

0) Seal the mouth of the metal pipe.

@) Impregnate with silicone oil.

In particular, various methods have been considered for method 0, such as complete sealing with low melting point glass, simple sealing with silicone resin, epoxy resin, etc.

However, in order to ensure workability and reliability after sealing, (
Regarding method 1), two methods have been particularly devised and implemented.

0)-1 Insert the backing impregnated with oil and insert the sealant on the outside to seal it. (Japanese Unexamined Patent Publication No. 121346/1983) (1) Seal the mouth of the metal pipe with a -2 plug body, and
The gap between the plug, metal pipe, and terminal is sealed by interposing a low polymerization degree polymer such as silicone grease or a high viscosity liquid such as silicone oil. (Japanese Unexamined Patent Publication No. 52-6839) Also, in method (2), silicone oil remains at the mouth of the metal pipe or blows out when energized, making it difficult to put it into practical use. The silicone oil at the mouth of the metal pipe is gelled in advance, and then
It is sealed with silicone resin or the like.

Problems to be Solved by the Invention However, in the above-mentioned method, especially (1)-1
In 0)-2, the electric insulating powder made of fused magnesia powder is not treated with any water repellent treatment, so in the unlikely event that the sealing structure is defective or the backing or plug is damaged during use. When moisture enters as a result of deterioration over time, the electrical characteristics deteriorate significantly.

Further, the backing used in 0)-1 is a porous material such as asbestos or foamed rubber, which does not have very good heat resistance and may deteriorate during actual use.

On the other hand, in method (2), the gelation operation is complicated;
This becomes a major factor in increasing costs.

For these reasons, a sheathed heater having a sealing structure that is relatively simple and has excellent reliability has been desired.

In view of these problems, it is an object of the present invention to provide a sheathed heater that has high reliability in electrical characteristics and can be manufactured by a relatively simple method.

Means for Solving the Problems In order to solve the above problems, the present invention uses fused magnesia powder impregnated with silicone oil as the electrical insulating powder, and silica or alumina fibers are applied to the mouth of the metal pipe. A silicone oil-impregnated layer made of inorganic fiber paper as a main component and an insulating layer made of a silicone rubber molded body or a ceramic molded body located outside this layer are formed respectively.

Function Conventionally, the opening of the metal pipe of a sheathed heater has been sealed for various purposes, such as 0) preventing dust from entering, (2) ensuring insulation distance, and 3) ensuring electrical properties by preventing moisture from entering. A stop occurs.

However, as mentioned in the prior art section, when sealing the mouth of a metal pipe, other than complete sealing with low-melting glass, other methods do not require water-repellent electrical insulating powder. Since no treatment has been applied, if the sealed portion deteriorates over time and moisture enters, the electrical characteristics will significantly deteriorate. Furthermore, in the method of impregnating the metal pipe with silicone oil, the silicone oil is not completely impregnated into the electrical insulating powder, and only a small amount remains at the mouth of the metal pipe, making it difficult to seal it easily.

In contrast, according to the present invention, electrical insulating powder is impregnated with silicone oil and treated to make it water repellent, and the silicone oil slightly remaining at the mouth of the metal pipe is replaced by silica or alumina. Since it is absorbed by the silicone oil-impregnated layer made of inorganic fiber paper whose main component is fiber, the silicone oil will not blow out when electricity is applied. In order to ensure the distance, only an insulating layer made of a silicone rubber molded body or a ceramic molded body is provided, which is very simple.

For these reasons, the method of impregnating silicone oil has traditionally had problems such as (1) blowing out of silicone oil when using electricity, and (2) complicating the sealing process at the mouth of the metal pipe. In addition to solving problems such as these, it is also possible to ensure reliability that could not be obtained by simply sealing the mouth of the metal pipe.

On the other hand, inorganic fiber paper mainly composed of silica or alumina fibers used as a silicone oil-impregnated layer has excellent heat resistance, absorbs silicone oil remaining at the mouth of metal pipes, and is treated to be water repellent. Therefore, the electrical characteristics are not impaired in this part.

EXAMPLE Below, an example of the present invention is inserted into the center of a metal pipe 3 in Figs. , and the diameter of the metal pipe 3 was reduced by rolling.

Thereafter, after annealing and bending into a predetermined shape, silicone oil was injected from the mouth of the metal pipe 3 to impregnate it into the electrical insulating powder 4. Next, an inorganic fiber paper made of silica-alumina fibers shown in FIG. 1 is inserted into the mouth of the metal pipe 3 to absorb the silicone oil remaining at the mouth of the metal pipe 3, thereby forming a silicone oil-impregnated layer. 5 was formed.

Furthermore, a second layer is provided on the outside of this silicone oil impregnated layer 6.
A ceramic molded body mainly composed of alumina having the shape shown in the figure was inserted to form an insulating layer 6, and the sheathed heater of the present invention shown in FIG. 3 was completed.

In order to evaluate the sheathed heater of the present invention completed in this way, we tested the
After being left for a month, electricity was applied to evaluate silicone oil for blistering, etc.

After being left in a humid atmosphere for one month, no particular decrease in insulation resistance or withstand voltage was observed. Furthermore, no silicone oil was blown out due to energization. Thus, it showed very excellent characteristics.

In the examples of the present invention, a ceramic molded body is used as the insulating layer, but the insulating layer is not limited to this, and other silicone molded bodies may also be used.

Effects of the Invention As is clear from the above explanation, according to the present invention, electrofused magnesia powder impregnated with silicone oil is used as the electrical insulating powder, and the mouth of the metal pipe is made of silica or alumina fiber as the main component. It has a silicone oil-impregnated layer made of inorganic fiber paper and an insulating layer made of a silicone rubber molded product or ceramic molded product located outside this layer, so it has high reliability and relatively low electrical properties. It is possible to provide a sheathed heater that can be manufactured by a simple method.

[Brief explanation of drawings]

Fig. 1 is a perspective view of an inorganic fiber paper used as a silicone oil impregnated layer in a sheathed heater according to an embodiment of the present invention, and Fig. 2 is a perspective view of a ceramic molded body used as an insulating layer in the same embodiment. FIG. 3 is a plan view showing a section of a part of a sheathed heater showing an embodiment of the present invention. 3...Metal pipe, 4...Electrical insulating powder, 6...Silicone oil impregnated layer, 6...
...Insulating layer.

Claims (1)

[Claims] Electrofused magnesia powder impregnated with silicone oil is used as the electrical insulating powder, and a silicone oil-impregnated layer made of inorganic fiber paper mainly composed of silica or alumina fibers is placed at the mouth of the metal pipe, and a silicone oil-impregnated layer is placed on the outside of this layer. 1. A sheathed heater comprising: and an insulating layer made of a silicone rubber molded body or a ceramic molded body.