JPH0656792B2 - Positive resistance temperature coefficient heating element manufacturing method - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a positive resistance temperature coefficient heating element (hereinafter referred to as PTC heating element) which is useful as a heating tool and a general heating device.

2. Description of the Related Art Conventionally, it has been known that a resistor composition in which a conductive fine powder is dispersed in a crystalline polymer exhibits remarkable PTC characteristics, and using this composition, a heating element having self-temperature controllability can be obtained. Attempts have been made to configure it. The advantages of this method are that the shape of the resistor is excellent in processability, any shape can be easily obtained, the flexibility is excellent, and the resistance value adjustment range is wide. It has been used as a low power density sheet heating element and a long flexible heating element.

However, when a large power density is required, a soaking plate is indispensable for making the temperature distribution of the heating element itself uniform, and in the conventional PTC heating element, as shown in FIG. On an electrically insulating substrate 1 made of a good alumina sintered body, a PTC resistor 2 whose main component is a material in which conductive fine powder is dispersed in a crystalline polymer is adhered, and both ends thereof are formed. Countermeasures have been taken such as providing a pair of electrodes 3a and 3b on the. (Japanese Patent Publication No. 55-40161) Problems to be solved by the invention In such a conventional high power density PTC heating element, a soaking plate is indispensable. Without the soaking plate, local abnormal heat generation due to voltage concentration A phenomenon occurs and normal heat generation characteristics cannot be obtained. Further, even if there is a soaking plate, there is a limit to the thermal conductivity of an electrically insulating material such as an alumina sintered body, and there is no sufficient margin for preventing the occurrence of voltage concentration. In addition, ceramic materials such as alumina sintered bodies are not flexible and have poor adhesion to objects to be heated, and there is a limit to the size and shape of the heating element that is integrally formed due to processing size restrictions. was there. As a material that replaces the ceramic-based heat equalizing plate, a heat equalizing plate made by laminating a metal plate with high thermal conductivity such as aluminum and an electrical insulating plate such as polyester film has been devised, but it only satisfies the withstand voltage characteristics sufficiently. When the thickness of the electric insulating plate is provided, it is difficult to obtain a soaking effect over the alumina sintered body, and it is not possible to obtain a large power density. As described above, the conventional high power density PTC heating element has many problems caused by the heat equalizing plate, and there is no room for further development.

In order to solve all the problems at once, it was important to introduce a PTC heating element that does not need to rely on a soaking plate.
As a result of studying with this point in mind, it was found that the width of the part where the voltage concentration phenomenon occurs is several millimeters or less, and if a pair of electrodes is installed within that range, the voltage gradient between the electrodes It was estimated that the heat generation distribution was almost uniform. As a result of further study, it was found that if a fine comb-shaped electrode is provided on the surface of the PTC resistor, the area occupied by the electrode becomes considerably large, the effective heat generating portion is almost eliminated, and such a large power density cannot be obtained. . As a solution to this problem, a method of applying a voltage in the thickness direction of the PTC resistor was introduced, and as a result of repeated experiments, no extreme voltage concentration phenomenon was observed when the thickness of the resistor was 5 mm or less. If the thickness is 1 mm or less, 2 W /
No abnormalities were observed even during heat generation of cm ² (temperature rise of 60 deg). From this result, it was concluded that the heating element with electrodes on both sides of a thin PTC resistor with a thickness of 5 mm or less has a high heat diffusion ability between the electrodes, and the voltage concentration phenomenon cannot occur essentially. did. However, although the breakdown phenomenon of the resistor due to the voltage concentration does not occur, there is an unexpectedly large voltage gradient distribution and temperature distribution between the heating electrode and the electrode against a large heat load, and the heat of the local resistor composition is locally generated. The thickness of the resistor should be at least 3mm as it will deteriorate and heat transfer loss will occur.
It has been found that it is preferably 1 mm or less. Since the heating element of this structure has a very simple structure and is free from various restrictions due to the heat equalizing plate, it is expected to make a great leap in terms of performance, structure and construction method.

When a specific study is started based on this conclusion, various problems concerning the withstand voltage characteristics of the PTC resistor composition, the securing of the insulation distance, the terminal treatment method, the mounting structure, the processing method, etc. are accumulated,
It was far from practical use. At the position where a ceramic-based PTC resistor such as a barium titanate sintered body was examined as an alternative, it is excellent in power density, heat resistance, withstand voltage characteristics, and thermal conductivity, and is a basic element for constructing a small heating unit. It was judged that there was no specific problem. However,
Since it is a sintered body, there is no flexibility, and there is a problem that it is extremely difficult to process a large area or a long length.Thus, it has a thin wall and a large area like a conventional sheet heating element or a long flexible heating element. It was difficult to satisfy the functions of uniform heat generation, flexibility, and continuous long processing. Judging from these points, the ceramic-based PTC resistor was abandoned, and it was confirmed that the only way to solve various problems in the case of using the organic-based PTC resistor was. Hereinafter, specific problems to be solved by the present invention will be described.

Made of organic material, thickness less than 3mm, preferably 1mm
The following heating element of the type in which 100 V to 200 V is applied in the thickness direction of the thin PTC resistor is excellent not only in terms of characteristics but also in productivity. In particular, the method of joining the electrode plates to both surfaces of the thin-walled PTC resistor while continuously forming it is the best. However, since the electrode plates of different polarities are very close to each other, even if there are extremely minute defects, breakdown of the withstand voltage may occur, and in the worst case, burnout may occur.
There are various possible causes of the defects, such as those caused by the resistor or those caused by the end faces of the electrodes, but there is one major problem in the processing method. It is relatively easy to finish the resistor and electrode into a long product by continuous processing, but it is how to process the cut end face. When a long object in which an electrode and a resistor are joined is cut, a thin wall is formed to form an exposed end surface in which electrodes of different polarities come close to each other through the resistor. Not only the electrodes of different polarities are close to each other on this end surface, but also cutting pieces of the electrodes,
Burrs in the cutting direction of the electrode end face and deformation at the end face portion of the resistor itself add a very dangerous point in terms of withstand voltage characteristics. Even if this is processed into a long product with an electrical insulation coating and then cut, the situation does not change. Even if the cut end face is molded with an insulating material, it is not guaranteed to be a good product.

The situation described above was extremely serious, and the possibility of long continuous machining was good or bad.

Means for Solving the Problems In order to solve the above problems, the present invention provides a thin positive temperature coefficient resistor having a thin film positive resistance temperature coefficient mainly composed of a composition in which conductive fine powder is dispersed in a crystalline polymer. A pair of electrode bodies are provided to apply a voltage in the vertical direction, and a long body in which the pair of electrode bodies are closely adhered to each other is formed at an arbitrary cutting interval so that the end face creepage distance between the electrodes is more than the thickness dimension of the resistor body. After cutting in a slanted shape so as to be large, at least the cut end face is covered with an electrically insulating material.

Action The action of this technical means is as follows. That is, a long body in which an electrode body integrated with a resistor is closely adhered enables excellent productivity by continuous processing, but a work piece in which a pair of heteropolar electrodes are joined via a thin-walled resistor. When is cut vertically, the distance between the electrodes of different polarities is closest to each other, so that the risk ratio is maximized. However, when cutting in a slanted shape such as making the cutting angle shallow with respect to the longitudinal direction, the gap between the electrodes of different electrodes in the cut surface widens, and electrode debris, burrs on the electrode end surface, and even the resistor itself It is possible to dramatically improve safety against deformation. Moreover, as a cutting method, it is possible not only to simply make the angle shallow, but also to widen the distance between different-polarity electrodes, such as curved surface cutting and stepwise cutting,
Further, by covering the cut single surface with an electrically insulating material, the safety can be further improved.

Example Hereinafter, an example will be described with reference to the accompanying drawings.

In FIG. 1, 4 is a PTC resistor having a thickness of 0.5 mm,
Reference numerals 5 and 6 are metal plate electrodes joined to the PTC resistor 4. These joined ends are 1
It has been cut at an angle of 1 degree, and the creepage distance between the electrodes 5 and 6 has increased to 2.6 mm, while at the same time greatly improving the safety against withstand voltage breakdown due to metal fragments and electrode burrs during cutting. ing. Not only can the end be cut at a uniform angle, but also the curved surface cutting as shown in FIG. 2 can further increase the creepage distance, and as shown in FIG. ．With a milling machine-shaped tool having a stepped blade with 1 mm steps, cutting with steps
Since a predetermined withstand voltage characteristic is obtained at each step, the safety can be further enhanced. Although such a cutting structure is effective, it is important to cut in a slanted shape in any case. The "inclined shape" is a general term for a face-like shape, a curved surface shape, and a stepped shape shown in FIGS. 1, 2, and 3. Further, in consideration of productivity, when a long workpiece is cut at a predetermined interval like the cut surfaces 7 and 8 shown in FIG. 4, there is no loss portion at all and an arbitrary length is obtained. It can also be manufactured efficiently. The end surface cut to increase the creepage distance is protected by an electrically insulating molding material 9 as shown in FIG. 5, or the entire surface is covered with an electrically insulating material. , Can further increase safety. As a result, in addition to the flexibility and workability peculiar to organic resistor materials, it has a high output that is close to that of a ceramic-based positive resistance temperature coefficient heating element. A coefficient heating element can be formed.

Effects of the Invention As described above, the present invention has the following effects.

(1) Even with a structure in which the electrode spacing is very close, it is possible to secure the safety against breakdown of the electrode due to cutting and breakdown of the withstand voltage due to burrs on the electrode cross section, etc., and a high output and highly reliable positive resistance A temperature coefficient heating element can be realized.

(2) It enables a safe processing structure that does not cause breakdown voltage breakdown even after cutting after continuous long-length processing, and the structure of the positive resistance temperature coefficient heating element with a structure in which the electrode intervals are very close to enable.

[Brief description of drawings]

FIG. 1 is a PTC showing a manufacturing method in an embodiment of the present invention.
2 and 3 are partial cross-sectional views of a PTC heating element showing a manufacturing method in another embodiment of the present invention, and FIG. 4 is a P showing a manufacturing method in an embodiment of the present invention.
FIG. 5 is a sectional view illustrating a method for cutting a TC heating element, FIG. 5 is a sectional view illustrating a manufacturing method in an embodiment of the present invention in which an end surface of a PTC heating element is covered with a molding material, and FIG. 6 is a perspective view of a conventional example. . 4 ... PTC heating element, 5, 6 ... Electrode, 9 ... Mold material.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Yasutomo Funakoshi 1006 Kadoma, Kadoma City, Osaka Prefecture Matsushita Electric Industrial Co., Ltd. (72) Inventor Tadashi Sakairi 1006 Kadoma, Kadoma City, Osaka Matsushita Electric Industrial Co., Ltd. 56) References Japanese Patent Application Laid-Open No. 53-122942 (JP, A) Japanese Patent Application No. 56-177656 (Japanese Utility Model Application No. 58-81889) The microfilm (J. P, U)

Claims (1)

[Claims] 1. A thin-walled positive temperature coefficient resistor having a composition in which a conductive fine powder is dispersed in a crystalline polymer as a main component,
Providing a pair of electrode bodies to apply a voltage in the thickness direction,
After cutting the elongated body in which the pair of electrode bodies are closely adhered to each other at an arbitrary cutting interval in an inclined shape so that the end face creepage distance between the electrodes is larger than the thickness dimension of the resistor, at least the cutting is further performed. A manufacturing method of a positive resistance temperature coefficient heating element in which the end face is covered with an electrically insulating material.