JPS6151791A - 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 Field of Industrial Application The present invention relates to a sheathed heater that is widely used as a heating source for general home appliances, industrial electric furnaces, and the like.

Regarding the configuration of the conventional example and its problems, sheathed heaters are currently widely used as a heating source for industrial electric furnaces.

This is because the sheathed heater is simple, has excellent electrical insulation, is safe, and has excellent corrosion resistance.

In general, a sheathed heater has a coiled heating wire with electrical outlet terminals at both ends inserted into the center of a metal pipe, and this metal pipe is filled with electrically insulating powder made of electrofused mag powder. Both ends are sealed with low melting point glass and heat resistant resin.

A sheathed heater with this structure has excellent electrical insulation between the metal pipe and the electrical outlet terminal, so this type of sheathed heater is used in products where safety is particularly important. Their sheathed heaters use 5US304, 5US321, NC as metal pipe materials.
Use any of the Fso○ materials, 5O83o4 as the electrical outlet terminal, and low melting point glass as the
A glass material having a linear expansion coefficient of 110 to 130 x 10-7/c has been used to match the metal pipe material and the electrical outlet terminal material.

However, during the manufacturing process of such 7-Z heaters, especially in the post-process after sealing the glass, or when assembling the sheathed heater into the product, a load is applied to the electrical outlet terminal, causing the low melting point glass to break. However, electrical insulation properties may be impaired, and a sealing material, fold or sealing structure with excellent mechanical strength is desired.

OBJECTS OF THE INVENTION The present invention solves the above-mentioned conventional drawbacks, and an object of the present invention is to provide a sheathed heater having a sealed structure with excellent mechanical strength.

Structure of the Invention In order to achieve the above object, the present invention provides a sheathed heater in which the gap between the metal pipe and the electrical outlet terminal is sealed with a glass sealing material, in which the coefficient of thermal expansion of the metal pipe is ap /
℃r The thermal expansion coefficient of the electrical outlet terminal is a T/t
: When the thermal expansion coefficient of the glass sealing material is (lq/℃, αq≦ap-40X10-', and aq-30X
10-7≦ (ZT≦ag+20 , which can increase mechanical strength.

DESCRIPTION OF THE EMBODIMENTS An embodiment of the present invention will be described below with reference to FIG.

As a metal material, NCFao○, 5US3041NCF
600.5US430. Iron, 42Fe-Ni, 50Fa
Ni.

α=40~180×1 using Kovar etc. or glass
Using a material with a coefficient of thermal expansion of 0-77°C,
We made metal pipes, electrical output terminals, and glass tablets. Table 1 shows the thermal expansion coefficients of the metal materials used here. The above-mentioned materials were combined as shown in Table 2 to produce a sheathed heater having a diameter of 6.6 mm and a length of 500 vrm as shown in FIG. 1.

As shown in FIG. 1, the sheathed heater has a coiled heating wire 3 connected to an electricity extraction terminal 2 placed in the center of a metal pipe 1, and magnesia powder is placed between the metal pipe 3 and the heating wire 3. The metal pipe 30 was prepared by filling the metal pipe 30 with a metal pipe 4, rolling it to reduce its diameter, annealing it, and then sealing both ends of the metal pipe 30 with a glass sealing material S.

Margin Table 1 Below: On the other hand, the number of sheathed heaters in each combination was 2 to 10, and sample numbers 1 to γ7 were assigned according to each combination.

The thermal expansion coefficients αq and αT of the glass sealing material and the electrical output terminal are respectively changed based on the thermal expansion coefficient of 12T of the metal pipe.

In this way, in order to check the mechanical strength of the sealed structure of the completed sheathed heater, as shown in Fig. 2, a load was applied at a point 10 am from the tip of the metal pipe 1, and then the water pressure tank was closed. The cracks in the glass sealing material were investigated by putting the glass in the container and pressurizing it at 3.5 atmospheres for 1 hour, and then measuring the electrical insulation value between the metal pipe 1 and the electrical outlet terminal 2. At this time, the sheathed heaters that showed 2000 MΩ or more were considered to be good and marked with an O mark, and those below 20001 V1Ω were marked with an X mark, and the results are shown in Table 2.

Note that the load was set between F=o to 6 to 9.

Table 2 in the margin below Note: Some temperature ranges are different. (See Table 1) As is clear from Table 1, the sheathed heater made of the conventional combination of sample numbers 10 and 17 has a maximum of F = 2 K, and if a load higher than that is applied, the glass will break. It cracked and the electrical insulation deteriorated. On the other hand, αq≦ap-40X 10-' and aq-3
When using a combination of materials that satisfies 0X10"≦LIT≦ag+20X10-', it is possible to withstand up to F=4 to 6 K7, and as a result, it is possible to obtain a sheathed heater having a sealed structure with excellent mechanical strength. did it.

In the present invention, by using a combination of materials having the above-mentioned coefficient of thermal expansion, it is possible to create a seal that leaves compressive strain in the glass part when it is left to cool in the atmosphere after sealing. As a result, a sealed structure with excellent mechanical strength was obtained.

Effects of the Invention As is clear from the above explanation, according to the present invention, the thermal expansion coefficient of the metal pipe is ap/°C+, the thermal expansion coefficient of the electrical outlet terminal is αT/°C, and the thermal expansion coefficient of the glass sealing material is αT/°C. When α97℃, aq≦ap-40X10
And aq-30XjO≦αT≦ag+20X10-
Since the combination of materials is used, it is possible to obtain a sheathed heater having a sealing structure with excellent mechanical strength.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view of a sheathed heater showing an embodiment of the present invention, and FIG. 2 is a simplified diagram showing a state in which a load is applied to the electrical outlet terminal of the same sheathed heater. 1... Metal pipe, 2... Electrical outlet terminal, 3... Heating wire, 4... Magnesia powder, 6... River/glass sealing material.

Claims (1)

[Claims] In a sheathed heater in which the gap between the metal pipe and the electrical outlet terminal is sealed with a glass sealant, the coefficient of thermal expansion of the metal pipe is ap/℃, and the coefficient of thermal expansion of the electrical outlet terminal is a_
T/℃, and when the thermal expansion coefficient of the glass sealing material is ag/℃, ag≦ap-40×10^-^7 and ag-3
0×10^-^7≦a_T≦aq+20×10^-^7
A sheathed heater characterized by using a combination of materials.