JPH065355A - Sheet heater element - Google Patents

Abstract

PURPOSE:To prevent a heater wire from being disconnected due to an excessive temperature rise, and lengthen the service life by providing a fibrous heat insulating member, and heater wire curved in a zigzag shape or in a waveform and an opening part formed in the fibrous heat insulating member. CONSTITUTION:A heater wire 1 curved in a zigzag shape or in a waveform is buried closely to the surface of a ceramic fibrous heat insulating member 2, and an opening part is formed by removing a part 4 on the surface of the member 2 in which the wire 1 is embedded so that the greater part of the wire 1 except curved parts can be exposed. Radiation from the wire 1 and direct heat conduction to the atmosphere are made possible. Thereby, the lowering of wire 1 temperature becomes possible, and working temperature of a heater element can be raised, and the service life can be lengthened remarkably. The wire 1 is not separated unnecessarily from the member 2, and quantity of heat in this embedded part is conducted to a part whose surface is exposed due to the heat conduction, so that temperature does not become high so much. Thereby, since the wire 1 can be prevented from being disconnected due to an excessive temperature rise, the service life can be lengthened.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention relates to a sheet heating element, particularly 100
The present invention relates to a sheet heating element used in a heating furnace for high temperatures of 0 ° C. or higher.

[0002]

2. Description of the Related Art Conventionally, a heating wire is embedded in a ceramic fiber insulating material having a high heat insulating effect to form a heating element, which is installed on the inner surface of an electric furnace or used as a planar heating element. Generally, in the case of such a heating element, the heating wire is processed into a coil shape and disposed as close to the surface of the ceramic fiber heat insulating material as possible to prevent the temperature of the heating wire from becoming too high. If the heating wire is deeply embedded in the ceramic fiber heat insulating material, the temperature difference between the surface of the ceramic fiber heat insulating material that is the heat dissipation surface and the deepest part of the heating wire becomes large,
The heating wire will overheat and break.

Therefore, as shown in FIGS. 4 and 5, in the case where the heating wire 1 is processed into a coil shape, the heating wire 1 is buried so that a part or all of one surface of the heating wire 1 is exposed to the atmosphere. The opening 3 is provided in the surface portion of the ceramic fiber heat insulating material 2. However, in such a case, there is a problem that the temperature of the other surface of the other surface of the heating wire 1 that is farther than the surface tends to be high, and that the thickness of the heating element cannot be easily reduced.

Therefore, as shown in FIGS. 6 and 7, a heating element in which the heating wire 1 is bent in a zigzag shape and arranged near the surface of the ceramic fiber insulating material 2 is also widely used.

[0005]

However, in the case of such a heating element, even though it is close to the surface of the ceramic fiber insulating material 2, the heating wire 1 is entirely covered by the ceramic fiber insulating material 2. There is a drawback that the temperature of the heating wire 1 is inevitably increased due to the covering and no heat transfer due to radiation and the heat insulating effect of the covering ceramic fiber heat insulating material 2.

The present invention eliminates the above drawbacks.

[0007]

The sheet heating element of the present invention comprises a fibrous heat insulating material, a zigzag or wavy curved heating wire embedded near the surface in the fibrous insulating material, and a heating wire of the heating wire. It is characterized in that it comprises an opening formed in the above-mentioned fibrous heat insulating material for exposing most of it.

[0008]

Embodiments of the present invention will be described below with reference to the drawings.

In the present invention, as shown in FIGS. 1 to 3, a heating wire 1 curved in a zigzag shape or a wave shape is embedded near the surface of a ceramic fiber heat insulating material 2, and the curved portion of the heating wire 1 is removed. By removing a part 4 of the surface of the ceramic fiber-like heat insulating material 2 in which the heating wire 1 is buried so that most of the heating wire 1 is exposed, radiation from the heating wire 1 and direct heat transfer to the atmosphere can be achieved. It can be so.

Since the sheet heating element of the present invention is constructed as described above, the temperature of the heating wire 1 can be lowered, the operating temperature of the heating element can be raised, and the life can be remarkably extended. Becomes

Further, since the curved portion of the zigzag or wavy heat generating wire 1 is buried in the ceramic fiber heat insulating material 2, the heat generating wire 1 does not detach from the ceramic fiber heat insulating material 2 unintentionally. The amount of heat of this buried portion is not so high as a result of being conducted to the exposed portion of the surface by heat conduction. However,
If this part is buried too deeply, the heat conduction distance becomes large and the life is affected.

According to the trial production example, if the depth of the heating wire was kept to be 2.5 times or less, it could be practically used without any problem. For example, if the heating wire diameter is 2 m / m, the burial depth is 5 m / m.
In the following, the maximum temperature of the buried portion was 1250 ° C. or lower when the temperature of the exposed portion was 1200 ° C. in the atmosphere, but it was 1370 ° C. in the conventional one shown in FIGS. 6 and 7. So, the operating temperature of the heating wire has reached the limit.

Further, as compared with the conventional heating wire 1 in which the entire surface of the heating wire 1 is covered, the heating rate is about 30 when there is no object to be heated.
%, And the cooling rate was also about 15% faster. As a result, not only when there is no object to be heated but also when the object to be heated is placed at a short distance, the response speed when performing temperature adjustment is fast, and accurate temperature adjustment is possible, and the temperature can be adjusted accurately. The overshoot against the set temperature at the start-up was much less, the damage to the heating wire was less, and the life could be extended.

[0014]

As described above, according to the sheet heating element of the present invention, it is possible to prevent the heating wire from being overheated and to be disconnected, and there is a great advantage that the life can be extended.

[Brief description of drawings]

FIG. 1 is a plan view of a sheet heating element of the present invention.

FIG. 2 is a sectional view taken along the line AA of FIG.

FIG. 3 is a sectional view taken along line BB of FIG.

FIG. 4 is a cross-sectional view of a conventional sheet heating element.

FIG. 5 is a cross-sectional view of a conventional sheet heating element.

FIG. 6 is a plan view of another conventional sheet heating element.

7 is a cross-sectional view taken along the line AA of FIG.

[Explanation of symbols] 1 heating wire 2 ceramic fiber heat insulating material 3 opening 4 part of the surface

Claims (1)

[Claims] 1. A fibrous heat insulating material, a zigzag or wavy curved heating wire embedded near the surface in the fibrous insulating material, and the fibrous heat insulating material for exposing most of the heating wire. A planar heating element comprising a formed opening.