JP2003142240A - Heating element for resistance furnace - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a heating element for a resistance furnace which can extend life of a heating element by decreasing surface load density or apply large electric power without making larger outside diameter or increasing the number or the heat generating elements, in a type of a heating element set in a resistance furnace used for calcining electronic components, fusing metal, glass or the like. SOLUTION: In heating element set in a resistance furnace, at least an outer surface of a heat generating part of the heating element is formed unevenly. Forming continued wavy roughness to a peripheral direction of the heat generating part is more preferable.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to firing of electronic parts,
In resistance furnaces used for melting metals and glass,
The present invention mainly relates to a resistance furnace heating element arranged as a heat source at about 1000 to 1500 ° C.

[0002]

2. Description of the Related Art As a heat source for a resistance furnace, silicon carbide (Si
C) Quality heating elements are widely used, and various shapes such as rod-shaped, U-shaped, W-shaped, and U-shaped are applied depending on the usage and application. ) Shape or a pipe (hollow) shape. A heating element made of molybdenum silicide (MoSi ₂ ) is also used.

In selecting the number and shape of heating elements in a resistance furnace, the surface load density of the heating elements (a value obtained by dividing the electric power applied to the heating elements by the surface area of the heating elements, the unit being W / cm).
² ) is important and becomes a major factor in determining the durability of the heating element. The higher the surface load density, the shorter the life of the heating element.

Usually, from the viewpoint of economy, the outer diameter and the number of heating elements are determined by calculating the total surface area of the heating portion based on the required power so that the surface load density will be about 5 W / cm ^2. If the number of heating elements is small or the outer diameter is small, the initial cost for the heating element is low, but the life of the heating element is short and the running cost increases, and if the number of heating elements is large or the outer diameter is small. Is large, the life of the heating element is long and the running cost is low, but the initial cost for the heating element is high and the equipment cost is high.

In designing a resistance furnace, it is very important to determine the outer diameter and the number of heating elements arranged as a heat source of the resistance furnace. However, when designing a resistance furnace, the requirement that a little more electric power is applied and a little more Although there are many demands for extending the life of heating elements, conventionally, in order to meet such requirements, the outer diameter of the heating elements must be increased or the number of heating elements must be increased. There was a problem that it was difficult in terms of body space and that the furnace had to be modified.

[0006]

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned conventional problems in the selection of the number of heating elements and the outer diameter of the heating elements arranged in the resistance furnace. In a resistance furnace, it is possible to reduce the surface load density to extend the life of the heating element or to apply a large amount of power without increasing the outer diameter of the heating element or increasing the number of heating elements. To provide a heating element for use.

[0007]

A heating element for a resistance furnace according to claim 1 of the present invention for achieving the above object is a heating element disposed in a resistance furnace, wherein at least a heating portion of the heating element is provided. It is characterized in that the outer surface is formed to be uneven.

According to a second aspect of the present invention, there is provided a resistance heating element for a resistance furnace, wherein at least the outer surface of the heating portion of the heating element disposed in the resistance furnace is formed into wavy concavities and convexities continuous in the circumferential direction of the heating portion. It is characterized by having done.

A heating element for a resistance furnace according to claim 3 is
In Claim 1 or 2, The said heat generating body is a silicon carbide type heat generating body, It is characterized by the above-mentioned.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention is characterized in that, as shown in FIG. 1, at least the outer surface of the heat generating portion 2 of the heat generating element 1 is formed to be uneven. Although the unevenness is formed on at least the outer surface of the heat generating portion 2, it may be formed on the entire heating element. The unevenness may be formed on the entire outer surface of the heat generating portion 2, or may be formed on a part of the heat generating portion.

The shape of the irregularities may be random, but it is preferable that the irregularities are formed in a continuous wavy pattern. As the form of the wavy unevenness, it is possible to form a wavy unevenness that is continuous in the longitudinal direction of the heat generating portion, but from the viewpoint of manufacturing,
It is preferable to form wavy concavities and convexities continuous in the circumferential direction of the heat generating portion. For example, in the case of a heating element having a pipe (hollow) heating portion, it is preferable that the heating element has a cross-sectional shape having a wavy outer surface 3 as shown in FIG. A heating element having a rod-shaped (solid) heating portion can also be formed on the same outer surface. In addition, in FIG.
Reference numeral 4 is an electrode portion of the heating element 1, and 5 is an end portion.

The wavy irregularities are curved irregularities as shown in FIG. 2, irregularities having sharp peaks and troughs, trapezoidal irregularities having peaks and troughs, and rectangular shapes. Irregularities having peaks and troughs, other irregularities that increase the surface area of the outer surface, or a combination of these irregularities can be applied.

In the case of a heating element having a pipe (hollow) shape, the heating portion has a circular outer surface 6 as shown in FIG. 3, the outer diameter of the heating portion is d, and the length of the heating portion is long. When the length is l, the surface area of the heat generating portion is given by π × d × l.

On the other hand, in the heating element of the present invention having the cross-sectional shape having the wavy outer surface 3 formed in the circumferential direction as shown in FIG. 2, the outer surface is wavy, so that For example, the surface area is 1.3 to 1.6 times that of the conventional one (1.3 to 1.6 × π × d × l), and 30 to 60%.
The heating surface area is increased to some extent. That is, in the case of the same surface load density, 30 to 60% more power can be applied, and in the case of applying the same power, the surface load density can be reduced and the life of the heating element can be extended. Can be achieved.

[0015]

EXAMPLES Examples of the present invention will be described below in comparison with comparative examples. These examples show one embodiment of the present invention, and the present invention is not limited thereto.

Example 1, Comparative Example 1 Outer diameter 20 mm, heat generating portion length 300 mm, end portion length 300
mm to a 900 mm long silicon carbide heating element,
As shown in FIG. 5, the unevenness in the shape of a continuous surface was formed in the circumferential direction of the heat generating portion.

The cross-sectional area of the heat generating portion having the irregularities is the same as the cross-sectional area of the heat generating portion having no irregularities (conventional), and therefore the resistance value is the same as that of the non-convex (conventional) 1.1 Ω. although, the surface area of the heat generating portion is 296Cm ^2, do not form irregularities has 57% larger than in 188cm ² (conventional) ones.

This heating element is placed in a resistance furnace and the temperature inside the furnace is:
1400 ° C., D.I. P (dew point): 100 at + 70 ° C
The furnace was continuously operated for 0 hours and the rate of increase in resistance was measured. The results are shown in Table 1.

[0019]

[Table 1]

As shown in Table 1, the heating element of Example according to the invention, surface loading density of 3.2 W / cm ^2, the surface loading density of 5.0 W / cm ² conventional heating element of Comparative Example As compared with the conventional method, the resistance increase rate after 1000-hour furnace operation was decreased from 95% to 50%. This means that the life of the heating element has been significantly extended.

[0021]

According to the present invention, in a heating element disposed in a resistance furnace used for firing electronic parts, melting metal or glass, etc., the outer diameter of the heating element can be increased or Provided is a resistance furnace heating element capable of reducing the surface load density to extend the life of the heating element or applying a large electric power without increasing the number of the heating elements.

[Brief description of drawings]

FIG. 1 is a front view showing an embodiment of a resistance heating element of the present invention.

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

FIG. 3 is a sectional view of a heating portion of a conventional resistance heating element.

[Explanation of symbols]

1 heating element 2 heating part 3 Wavy outer surface 4 electrode part 5 edge 6 circular outer surface

   ─────────────────────────────────────────────────── ─── Continued front page    F term (reference) 3K092 PP09 QA01 RD09 SS28 VV38                 4K063 AA04 AA06 AA13 BA01 BA06                       BA12 CA01 CA04 FA04 FA07                       FA09

Claims (3)

[Claims] 1. A heating element for a resistance furnace, characterized in that, in a heating element arranged in a resistance furnace, at least an outer surface of a heating portion of the heating element is formed to be uneven. 2. A heating element for a resistance furnace, wherein the heating element arranged in the resistance furnace has at least an outer surface of the heating portion formed into wavy irregularities continuous in the circumferential direction of the heating portion. 3. The heating element for a resistance furnace according to claim 1, wherein the heating element is a silicon carbide heating element.