JPH0679499B2 - Positive resistance temperature coefficient heating element - Google Patents

Description

TECHNICAL FIELD The present invention relates to a useful 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.

It has been known that a resistor composition in which a conductive fine powder is dispersed in a crystalline polymer exhibits remarkable PTC characteristics.
Attempts have been made to construct a heating element having self-temperature controllability using this composition. The advantage of this method is 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 to make 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 composed mainly of a material in which conductive fine powder is dispersed in a crystalline polymer is closely adhered,
Measures have been taken such as providing a pair of electrodes 3a and 3b at both ends thereof. (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 not enough room for the voltage concentration limit. Furthermore, since ceramic materials such as alumina sintered bodies are not flexible and have poor adhesion to objects to be heated, or it is difficult to make large ones, the dimensions and shape of the heating element that is integrally formed There was also a limit. On the other hand, as a material that replaces the ceramic heat equalizing plate, a heat equalizing plate made by laminating a high thermal conductivity metal plate such as aluminum and an electrical insulating plate such as polyester film has been devised, but it has sufficient withstand voltage characteristics. If the thickness of the electric insulating plate is set to be sufficient, it is difficult to obtain a soaking effect over the alumina sintered body, and a large power density cannot be obtained. Thus, conventional high power density PTC
The heating element had many problems caused by the heat equalizing plate, and there was 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 and the effective heat generating part is almost eliminated, so that a large power density cannot be obtained. . As a solution to this problem, a voltage application method in the thickness direction of the PTC resistor was introduced, and as a result of repeated experiments, no extreme voltage concentration phenomenon was observed if the thickness of the resistor was 5 mm or less. Also, 1m thick
Below m, no anomaly was observed even when heat was generated at ² W / cm ² (60 deg heating) under a large heat radiation load. From this result, it is concluded that a 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 essentially no voltage concentration phenomenon can occur. did. However, although the breakdown of the resistor due to voltage concentration does not occur, there is an unexpectedly large voltage gradient distribution and temperature distribution between the heating element electrodes for a large heat load, and the heat of the local resistor composition is locally generated. The thickness of the resistor should be at least 3 mm or less, preferably 1 mm, as it may deteriorate or cause heat transfer loss.
It turned out to be: Since the heating element of this structure has a very simple structure and is free from various restrictions caused by the heat equalizing plate, it is expected to make a great leap in terms of performance, structure and construction method.

If a specific study is started based on this conclusion, various problems such as 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 piled up,
It was far from practical use. As a result of examining a ceramic-based PTC resistor such as barium titanate sintered body as an alternative method, it was found that it has excellent power density, heat resistance, withstand voltage characteristics and thermal conductivity, It was judged that there was no specific problem. However, since it is a sintered body, it has no flexibility, and there is a problem that it is extremely difficult to process a large area or a long length. It was difficult to fulfill the functions of thinness like a body, large area, uniform heat generation, flexibility, and continuous long processing. Judging from these points, we abandoned the ceramic PTC resistor and confirmed that the only way to solve the problems when using the organic PTC resistor was to solve it.

Hereinafter, specific problems to be solved by the present invention will be described.

Thin-walled organic PTC with a thickness of 3 mm or less, preferably 1 mm or less
The method of applying 100V or 200V in the thickness direction of the resistor seems to be reckless at first glance, considering the common sense so far. The main reason is that even if there are extremely minute defects due to the close distance between different poles, breakdown voltage breakdown easily occurs, and in the worst case, burnout is expected. . One of the important factors that can cause the defect is the structure and the processing method of the end faces of the pair of different-polarity electrodes that are formed at extremely close positions. Since the pair of different-polarity electrode end faces are separated from each other by a distance of 3 mm or less or 1 mm or less, it is easily assumed that the withstand voltage characteristics are insufficient due to scraps of the electrode material or deformation due to external force. Further, even if a post-processing step is added for the insulation treatment of the electrode end face, since the portions are very close to each other, there is a possibility that a defective portion may be created, and there is no reliable method.

Means for Solving the Problems The present invention is a thin-walled PTC resistor mainly composed of a composition in which a conductive differential powder is dispersed in a crystalline polymer in order to solve the above problems, and a voltage in the thickness direction thereof. And a creeping distance along the outer surface of the resistor formed between the end faces of the pair of electrode bodies is at least larger than the thickness dimension of the resistor. While the widthwise both end portions of the resistor body protrude from one widthwise direction of the pair of electrode bodies, at the same time the protrusion portion holds the shape from the back surface by laminating with the other of the pair of electrode bodies. It is configured to be formed.

Operation The effects of this technical means are as follows. That is, since it is dangerous to subject the end faces of the electrodes of different polarities to the contact with the thin PTC resistor via the end face, it is dangerous to perform insulating treatment on the end faces.
Since the PTC resistor itself is a material that can withstand overvoltage application,
Instead of using other electrically insulating material on the end face,
It is conceivable that the C-resistor itself should be placed in a positional relationship that allows a sufficient creepage distance between the electrode end faces of different polarities. The larger the creepage distance, the safer it will be.However, at least the creepage distance of the PTC resistor is formed by protruding it from the electrode body in the width direction, but since this part is a thin resistor itself, it has sufficient strength. It is not rigid and may be lost during processing. The resistor protruding from one electrode body is laminated with the other electrode body at the same time when it is formed, and the strength and shape thereof can be maintained.

Embodiments Embodiments will be described below with reference to the accompanying drawings.

(Example 1) In FIG. 1, 4 is a PTC resistor having a thickness of 0.3 mm,
Is a metal plate electrode 3 mm narrower than the PTC resistor 4. The electrodes 5a and 5b are attached to the center of the PTC resistor 4 along with the protruding portions at both ends, and the creepage distance is 3.3 mm because it is the sum of two locations in the width direction and one location in the thickness direction. Although it is not easy to cut the end face of the electrode after adhering it to the entire surface or to cut it out from the large adhered one, it is easy to process with this method. In the structure of FIG. 1, the widths of the electrodes 5a and 5b are not necessarily the same,
Further, the same effect can be obtained as long as the positional relationship is such that the creepage distance can be secured even if it is not necessarily provided in the center of the PTC resistor 4. Although it is possible to secure a creepage distance with this configuration, it is necessary to have the configuration shown in FIG. 2 in order to ensure high reliability.

In Fig. 2, 6 is a PTC resistor with a thickness of 0.3 mm, and 7a is a PT resistor.
A metal plate electrode whose width is 5 mm smaller than the C resistor 6, 7b is PTC
It is a metal plate electrode having the same width as the resistor 6. The electrode 7a is attached to the center of the PTC resistor 6 with protruding portions at both ends, and the electrode 7b is attached so as to overlap the PTC resistor 6, and the creepage distance is 2.8 mm.

The structure shown in FIG. 2 is characterized in that the protruding portion of the PTC resistor 6 is reinforced by the electrode 7b, and the creepage distance can be reliably obtained. In the configuration of FIG. 2, even if the width of the electrode 7b is larger than the width of the PTC resistor 6,
Further, even if the electrode 7a is not necessarily located at the center of the PTC resistor 6, the same effect can be obtained.

(Example 2) In FIG. 3, 8 is a PTC resistor having a thickness of 0.3 mm, and 9a, 9b
Is a metal plate electrode having a width 2.5 mm smaller than that of the PTC resistor 8. The electrode 9a is adhered along the left end of the PTC resistor and the electrode 9b is adhered along the right end of the PTC resistor, and the creepage distance is 2.8 mm. The structure shown in FIG. 3 is characterized in that the creeping distance component of the PTC resistor 8 is reinforced by the electrodes 9a and 9b, and that the electrodes 9a and 9b may have the same width. In the configuration of FIG. 3, the end faces of the electrodes 9a and 9b do not have to be along the end face of the PTC resistor 8, and the same effect can be obtained even if there is a protruding portion.

EFFECTS OF THE INVENTION As described above, the present invention is intended for processing while reliably ensuring the creepage distance between the different-polarity electrode end faces, and as a result, the PTC heating element obtained has the following effects, and the conventional concept It is a breakthrough.

(1) Since the creeping distance constituent portion composed of the resistor itself is reinforced from the back surface by the other electrode body at the same time as the formation thereof, no defect in the creeping structure occurs.

Therefore, a positive resistance temperature coefficient heating element having extremely high reliability can be configured. Further, even if continuous and high-speed extrusion processing is performed, defects in the creeping structure do not occur, so that a highly accurate and highly reliable positive resistance temperature coefficient heating element can be quantitatively manufactured.

(2) The creepage distance can be formed at the same time as the processing, without any post-processing being applied to the creepage distance constituting portion of the resistor. Therefore, there is no factor for deterioration to progress in this portion, and a highly reliable positive resistance temperature coefficient heating element can be configured.

(3) In addition to the flexibility and shape freedom peculiar to organic resistance materials, it has a high output that follows ceramic resistance materials.
A positive resistance temperature coefficient heating element with dramatically improved heat generation performance, productivity, reliability, application range, etc. can be constructed.

[Brief description of drawings]

FIG. 1 is a vertical sectional view of a PTC heating element showing the basic concept up to the first embodiment of the present invention, and FIG. 2 is a vertical sectional view of a PTC heating element of the first embodiment of the present invention. FIG. 3 is a vertical sectional view of a PTC heating element according to a second embodiment of the present invention, and FIG. 4 is a perspective view of a conventional PTC heating element. 4,6,8 …… PTC resistors, 5a, 5b, 7a, 7b, 9a, 9b …… electrodes.

 ─────────────────────────────────────────────────── ─── 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 Laid-Open No. 53-122942 (JP, A) Japanese Patent Laid-Open No. 59-205704 (JP, A) Japanese Utility Model Laid-Open No. 58-81889 (JP, U)

Claims (1)

[Claims] 1. A thin positive temperature coefficient resistor having a thickness of 1 mm or less, which is mainly composed of a composition in which conductive fine powder is dispersed in a crystalline polymer, and a voltage is applied in the thickness direction. A pair of electrode bodies provided in such a way that the creeping distance along the outer surface of the resistor formed between the end faces of the pair of electrode bodies is at least greater than the thickness dimension of the resistor, and At the same time, both end portions in the width direction of the resistor body are formed so as to protrude from one width direction of the pair of electrode bodies, and at the same time, the protruding portion is formed by laminating with the other of the pair of electrode bodies while holding the shape from the back surface. Positive resistance temperature coefficient heating element.