JPH048637Y2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a terminal portion of a sheathed heater in which the sheathed heater is connected to a lead terminal.

[Prior Art] As shown in FIGS. 4 and 5, a sheathed heater 1 is constructed by covering a heater wire 4 such as a nichrome wire with an inorganic insulating material 3 such as magnesia and a metal sheath 2 such as a stainless steel tube. When connecting to a conductive wire for wiring to a power source, a terminal portion as shown in the figure is constructed, covered with a metal pipe 6 and an inorganic insulating material 3.

For example, the terminal section shown in FIG. 4 has the following structure. That is, the heater wire 4 of the sheathed heater 1 is exposed from the sheath 2 made of a stainless steel pipe or the like and the inorganic insulating material 3 made of magnesia powder, alumina powder, etc., and connected to the lead terminal 5. These sheathed heaters 1 and lead terminals 5
A metal pipe 6 is placed over the metal pipe 6, and one tapered end of the metal pipe 6 is welded to the sheath 2. In addition, in Fig. 4, the symbol 7 is shown as
A metal sleeve 7 welded near the end of the sheath 1 is inserted to reinforce the welded portion between the metal pipe 6 and the sheath 2. Further, the metal pipe 6 is filled with an inorganic insulating material 3 such as magnesia powder or alumina powder, and the metal pipe 6 is crimped to compress the insulating material 3 and increase its density.

On the other hand, the terminal section shown in Figure 5 is
Instead of the metal sleeve 7, the metal pipe 6 is fixed to the sheath 2 via a metal ring 8 having a sufficient thickness, that is, a difference in inner and outer diameters. The other configurations are the same as those described above.

[Problems to be Solved by the Invention] Compared to other parts of the sheathed heater 1, the terminal portion where the heater wire 4 is housed in the metal pipe 6 has a structure in which the heater wire 4 passes through the inorganic insulating material 3 and the metal The thickness of the portion extending to the outside of the pipe 6 is increased. In particular, the thickness of the inorganic insulating material 3 layer increases dramatically.

This inorganic insulating material 3 itself has high heat transfer resistance and is difficult to conduct heat, and it is also difficult to make the inorganic insulating material 3 denser in the metal pipe 6, and heat transfer occurs due to the presence of voids. It becomes more difficult to do. As a result, the amount of heat dissipated from the terminal portion is smaller than that from other portions, and the temperature of this portion becomes extremely high. Incidentally, when the heating temperature of the heater is approximately 800°C, the temperature near the exposed wire 4 may reach approximately 900°C.

For this reason, when heated, the terminal portion is likely to be seize, metal deterioration due to heat, or dielectric breakdown of the inorganic insulating material, etc., which are the main causes of reduced durability.

The present invention aims to solve the above-mentioned problems in the conventional terminal section.

[Means for Solving the Problem] That is, the gist of the means adopted in the present invention to achieve the above object is to connect the heater wire exposed from the end of the sheathed heater to a lead terminal, and connect the sheathed heater to the lead terminal. A metal pipe is placed from the end of the lead terminal to the end of the lead terminal, one end of which is fixed to the sheath of the sheathed heater, and the metal pipe is filled with an inorganic insulating material. Align the end of the metal sleeve, which has a tapered outer diameter that gradually becomes thinner toward the end, with the end of the sheath of the sheathed heater,
A metal sleeve is placed and fixed over the end of the sheath, one end of the metal pipe is joined to the sleeve, and the diameter of the portion of the metal pipe beyond the end of the metal sleeve is narrowed to remove the inorganic insulating material therein. This is the terminal part of a sheathed heater that is compressed.

[Function] In the sheathed heater according to the present invention, there is a metal sleeve near the peeled part of the heater wire where the inorganic insulating material layer is the thickest, and which has a much better heat conduction than the inorganic insulating material, and this metal sleeve has a much better thermal conductivity than the inorganic insulating material. Since it is fixed to a metal pipe, the heat generated in this part is released to the outside through the sheath and metal sleeve.

Furthermore, the end of this metal sleeve is tapered so that the outer diameter gradually becomes smaller toward the tip, and the metal pipe from the end of this metal sleeve is narrowed down. The inorganic insulating material inside is compressed to a high density by the compressive force acting along the taper gradient of the metal sleeve.

As a result, heat is smoothly radiated from the tip of the sheathed heater, where heat is most likely to accumulate in the past, and an extreme temperature rise is no longer observed.

[Example] Next, an example of the present invention will be described in detail with reference to the drawings.

As shown in Figures 1 to 3, the sheathed heater 1
The sheath 12 and the inorganic insulating material 13 are removed from the end of the heater wire 14 to expose the heater wire 14. A metal sleeve 17 is placed over the end of the sheathed heater 11 and fixed to the end of the sheath 12. The metal sleeve 17 has an inner diameter approximately equal to the outer diameter of the sheath 12, and is fitted tightly into the sheath 12. Note that the end of the metal sleeve 17 and the end of the sheath 12 are approximately aligned.

A steep taper 20 is formed at the end of the metal sleeve 17 so that the outer diameter gradually becomes thinner toward the tip, and the tip is aligned so as to match the tip of the sheath 12.

The metal pipe 16 is fitted into the metal sleeve 17, and the heater wire 14 exposed from the tip of the sheathed heater 11 is connected to the lead terminal 15.
Then, one end side of the metal pipe 16 is fixed to the metal sleeve 17 by means of welding 22 or the like.

Furthermore, an inorganic insulating material 13 is provided inside the metal pipe 16.
The inorganic insulating material 13 is compressed and densified by narrowing the portion of the metal pipe 16 beyond the metal sleeve 17 as shown by the two-dot chain line in each figure. Then, by sealing (not shown) the end of the metal pipe 16 on the lead terminal 15 side, a terminal portion is completed.

In the embodiment shown in FIG. 1, the inner diameter of the metal pipe 16 is approximately equal to the outer diameter of the metal sleeve 17;
A metal sleeve 17 is fitted into the pipe 16 and fixed. Therefore, in this case, metal sleeve 1
The outer periphery of 7 is covered with the metal pipe 16.

On the other hand, in the embodiments shown in FIGS. 2 and 3, the metal pipe 16 is joined to the end of the metal sleeve 17 in abutted state, and most of the outer periphery of the metal sleeve 17 is exposed to the outside. are doing.
Furthermore, in the embodiment shown in FIG.
a has been formed.

In the latter embodiment, since the outer periphery of the metal sleeve 17 is exposed from the metal pipe 16, heat is smoothly radiated therefrom. In particular, in the embodiment shown in FIG. 5, heat is radiated smoothly by the unevenness 17a, which is a heat radiating means. This heat dissipation means
In addition to the above-mentioned unevenness, appropriate means can be adopted as needed, such as spirally winding a pipe or band-like body with good heat conduction, or protruding a large number of metal fin-like objects.

In addition, in the terminal part according to the present invention having the structure shown in FIG. 1, when the heating temperature by the sheathed heater 11 is about 800°C, it is possible to suppress the temperature of the terminal part to around 600°C. That is, the heating temperature can be reduced by about 300° C. compared to the conventional terminal portion having the structure as shown in FIG.

[Effects of the invention] As explained above, according to the invention, heat is smoothly emitted from the inside of the terminal section to the outside, so there is no extreme temperature rise inside the terminal section, and the sheathed heater 11 is heated. It becomes possible to improve durability.

[Brief explanation of the drawing]

1 to 3 are longitudinal sectional side views of a sheathed heater 11 showing each embodiment of the present invention, and FIGS. 4 and 5 are longitudinal sectional side views showing each conventional example of the sheathed heater 11. 11... Sheathed heater, 12... Sheath, 13
... Inorganic insulating material, 14 ... Heater wire, 15 ...
Lead terminal, 16...metal pipe, 17...metal sleeve.

Claims (1)

[Scope of Claim for Utility Model Registration] (1) Connect the heater wire exposed from the end of the sheathed heater to the lead terminal, and cover the metal pipe from the end of the sheathed heater to the end of the lead terminal. A metal sleeve whose one end side is fixed to the sheath of the sheathed heater, and in which the metal pipe is filled with an inorganic insulating material, has a taper formed in the terminal portion of the sheathed heater, the outer diameter of which gradually becomes thinner toward the tip. Align the end of the sheath with the end of the sheath of the sheathed heater, cover and fix a metal sleeve over the end of the sheath, join one end of the metal pipe to the sleeve, and then A terminal part of a sheathed heater characterized by narrowing the diameter of the tip and compressing the inorganic insulating material therein. (2) A terminal portion of a sheathed heater according to claim 1 of the utility model registration, wherein the outer peripheral surface of the metal sleeve is covered with a metal pipe. (3) A terminal portion of a sheathed heater according to claim 1 of the utility model registration, in which the outer peripheral surface of the metal sleeve is exposed from the metal pipe. (4) A terminal portion of a sheathed heater according to claim 3 of the utility model registration, in which a heat dissipation means is formed on the outer peripheral surface of the metal sleeve.