JPS6248351B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for manufacturing a barium titanate-based semiconductor porcelain heating element having a positive temperature coefficient of resistance (hereinafter referred to as a positive characteristic porcelain heating element).

As is well known, positive characteristic porcelain heating elements have a self-temperature control function that automatically controls self-heating by rapidly increasing electrical resistance when a certain temperature is reached, and unlike nichrome heating elements, there is no danger of overheating. Since it is safe and highly reliable, it has been widely used as a heat source in various heat generating devices.

Positive characteristic porcelain heating elements are generally formed in the form of pellets, but in the form of pellets, the amount of heat generated per element is small, and the heat generated by hair dryers, warm air machines, clothes dryers, etc., which can reach several hundred watts or more, can be avoided. When used as a source, the number of elements used increases, which is disadvantageous in terms of performance and cost. In order to eliminate these drawbacks, as shown in Figure 1, the porcelain element 1
A honeycomb-shaped positive temperature characteristic porcelain heating element has been proposed in which a large number of through holes 2 are provided in the thickness direction. This positive characteristic porcelain heating element has a very large effective surface area per unit volume, and by allowing fluid such as air to flow directly through the through hole 2, an efficient heat exchange effect can be obtained between it and the partition wall 3. It is possible to generate more than several hundred watts of heat per element, which could not be achieved with conventional pellet-like products, and it can also extract hot air with excellent temperature-raising characteristics, making it suitable for hair dryers, hot air blowers, etc.
It has become widely used as a heat source for large-capacity products that require air blowing, such as clothes dryers. In addition, in FIG. 1, 4 and 5 are positive characteristic porcelain bodies 1.
This is an electrode provided on the end face of the partition wall 3.

The through holes 2 are circular or polygonal and are provided at approximately equal intervals, but conventionally, as shown in an enlarged view in FIG. The tubes were formed into straight tubes so that they were almost the same.

Therefore, the inner wall surface 3a of the partition wall 3 forming the through hole 2 is oriented in the flow direction a of the fluid flowing through the through hole 2.
Since the fluid flows linearly along the inner wall surface 3a, the heat exchange efficiency between the inner wall surface 3a and the fluid is poor, and there is a limit to the increase in the amount of heat generated.

SUMMARY OF THE INVENTION An object of the present invention is to eliminate the above-mentioned conventional drawbacks and to provide a method for easily manufacturing a honeycomb-shaped positive temperature characteristic porcelain heating element that has high heat exchange efficiency and a large calorific value.

In order to achieve the above object, the method for manufacturing a PTC porcelain heating element according to the present invention provides a method for producing a PTC porcelain heating element, in which a porcelain powder-containing lacquer is applied to the inner surface of the through hole at the end of a PTC porcelain molded body having a large number of through holes. The method is characterized in that the positive characteristic porcelain molded body is fired after adhering the fluid liquid.

DESCRIPTION OF THE PREFERRED EMBODIMENTS The content of the present invention will be specifically described below with reference to the accompanying drawings, which are examples. FIG. 3 is a partially enlarged sectional view of a positive characteristic ceramic heating element obtained by the manufacturing method according to the present invention. In this embodiment, the thickness _t 1 of the partition wall 3 located at a depth H ₁ from one end surface of the positive characteristic porcelain body 1 is
is thicker than the thickness t ₂ of the partition wall 3 below it,
The hole shape of the through hole 2 at the depth _H1 portion is made smaller than the hole shape at other portions. With such a structure, the inner wall surface 3a of the partition wall 3 constituting the through hole 2 becomes non-linear, so when fluid flows through in the direction of arrow a or b, the thickness of the partition wall 3 changes from t1 _to t. ₂ , the flow resistance changes, creating forced turbulence in the fluid and stirring the fluid. As a result, the heat exchange efficiency between the fluid and the partition wall 3 is improved, and the amount of heat generated is increased.

In this embodiment, the thickness t ₁ of the partition wall 3 at the depth H ₁ is approximately uniform over the entire circumference of the through hole 2, but as shown in FIG. Alternatively, part of the circumference may have a thickness of _t1 .

Figure 5 is an air volume-calorific value characteristic diagram, and the curve L ₁
is the air volume-heat value characteristic curve of the positive characteristic porcelain heating element according to the present invention, and curve _L2 is the air volume-heat value characteristic curve of the conventional positive characteristic porcelain heating element. This data was obtained using a honeycomb positive temperature coefficient porcelain heating element with a diameter of 42 mm and a thickness of 8 mm. As is clear from this characteristic diagram, the positive characteristic porcelain heating element according to the present invention has a significantly larger calorific value than the conventional one, and moreover, as the air volume increases, a larger calorific value can be obtained.
At an air volume of 0.4m ³ /mm, the amount of heat generated is more than 50W higher than before.

Next, a method for manufacturing the PTC porcelain heating element having the above structure will be described.

First, a positive characteristic porcelain molded body having a normal through-hole with a cross-sectional pore shape that is approximately the same over the entire length is produced according to a normal process, and this is once dried.

Separately, a binder resin and a solvent are added to the porcelain powder and kneaded to produce a lacquer-like fluid liquid. The porcelain powder may include porcelain materials of the same type as the positive characteristic porcelain molded body, as well as porcelain materials that do not adversely affect the properties of the molded body after firing, such as magnesia (MgO), zirconia (ZrO ₂ ), or alumina ( Oxides such as Al ₂ O ₃ ), or non-reactive compounds such as forsterite (Mg ₂ SiO ₄ ) and zircon (ZrSiO ₄ ) can be used.

Next, at one end of the dried positive characteristic porcelain molded body,
After depositing the lacquer-like fluid liquid to a suitable depth, it is dried again. As a result, the thickness of the partition wall 3 at one end of the molded body to which the ladle-like fluid has adhered becomes thicker as shown in FIGS. It becomes something different from the shape.

Methods for attaching the luscious fluid to the positive characteristic porcelain molded body include a dipping method in which one end of the mold is immersed in the fluid and pulled up, and a spray method in which the luscious fluid is sprayed onto one end of the molded body obliquely from above. Possible methods include a spraying method and an application method using a brush or roller. When the spray method is adopted, the structure shown in FIG. 3 or the structure shown in FIG. 4 can be obtained by selecting the spray angle.

Next, the molded body to which the fluidized liquid has been applied and dried is fired in accordance with the usual process, and the electrode forming surface is polished to expose the positive characteristic porcelain body, and then the electrode is coated and baked to complete the molded body. In this case, since the lacquer-like fluid is made of a porcelain material having a shrinkage ratio similar to that of the compact, firing cracks and the like will not occur.

As described above, in the method for manufacturing a PTC porcelain heating element according to the present invention, on the inner surface of the through hole at the end of a PTC porcelain molded body having a large number of through holes,
The feature is that the positive characteristic porcelain molded body is fired after adhering a ladle-like flowing liquid containing porcelain powder, so that turbulence is generated in the fluid flowing through the through hole due to the difference in hole shape. It is possible to provide a manufacturing method that can easily manufacture a positive characteristic porcelain heating element that forcibly generates heat, improves heat exchange efficiency, and increases calorific value.

[Brief explanation of the drawing]

FIG. 1 is a perspective view of a conventional PTC porcelain heating element, FIG. 2 is a partially enlarged sectional view of the same, and FIGS. 3 and 4 are PTC porcelain heating elements obtained by the manufacturing method according to the present invention. FIG. 5 is a partially enlarged sectional view of each embodiment of the body, and FIG. 5 is an air volume-heat amount characteristic diagram. 1...Positive characteristic porcelain body, 2...Through hole, 3...
Partition wall, 4, 5...electrode.

Claims (1)

[Scope of Claims] 1. After attaching a lacquer-like fluid containing porcelain powder to the inner surface of the through holes at the end of a positive characteristic porcelain molded body having a large number of through holes, the positive characteristic porcelain molding is performed. A method for producing a positive characteristic porcelain heating element, characterized by firing the body. 2. Claim 1, wherein the end portion of the positive characteristic molded body is immersed in the ladle-like fluid and then pulled up in order to adhere the lacus-like fluid to the inner surface of the through-hole. A method for manufacturing a positive characteristic porcelain heating element as described in . 3. The positive characteristic porcelain according to claim 1, characterized in that, in attaching the lacky fluid liquid to the inner surface of the through hole, the lacky fluid liquid is sprayed onto the positive characteristic porcelain molded body. Method of manufacturing a heating element.