JPH0785436B2 - Positive resistance temperature coefficient heating element - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a heating element useful as a heat collecting device and a general heating device.

2. Description of the Related Art A conventional heating element having a positive temperature coefficient of resistance (hereinafter referred to as PTC) has been self-controlled to an appropriate temperature by the PTC characteristic of a PTC resistor between a pair of electrodes.

However, particularly when a high power density is required, it is essential to make the temperature distribution in the direction between the pair of electrodes good in order to make the temperature distribution of the heating element itself uniform.
As a solution to this problem, as shown in FIG. 5, a method has been taken in which the distance between a pair of electrodes is close to each other. In FIG. 5, 1a and 1b are a pair of parallel plate-shaped metal electrodes provided close to each other, and by placing a PTC resistor 2 between them, a high output PTC heating element can be revealed. It has become possible.

Problems to be Solved by the Invention Generally, such a PTC resistor is oxidatively deteriorated due to long-term heat resistance and temporarily becomes high in resistance, or finally the crystalline resin is deteriorated and the positive resistance temperature characteristic disappears. Has a low resistance, and there is a risk of abnormal overheating, smoking, and ignition.
However, when the resistance is temporarily increased, it will be almost safe to generate heat and it is safe. However, in the structure in which the thin-walled opposing surfaces of the PTC resistor 2 along the longitudinal direction are covered with the flat plate metal electrodes 1a, 1b, the oxygen gas permeability of the portion covered by the flat plate metal electrodes 1a, 1b becomes 0. The heat deterioration is almost eliminated. On the other hand, not covered with the average metal electrodes 1a and 1b, for example, the edge surface portion 2a of the PTC resistor 2 shown in FIG. The heat-resistant deterioration rates of the part covered and the part not covered by are greatly different. Further, although the heat resistance deterioration rate can be slowed by the heat resistance stabilizer such as the antioxidant, it is not the ratio of the presence or absence of the flat plate metal electrode. Therefore, only the creeping part formed by the resistor 2 itself between the flat plate metal electrodes 1a, 1b undergoes heat oxidative deterioration to temporarily increase the resistance, but the part covered with the average metal electrodes 1a, 1b normally generates heat. This heat promotes further deterioration of the creeping part, eventually lowering the resistance,
There was a risk of abnormal heating, smoke, and ignition due to cracks. As described above, the conventional PTC heating element as shown in FIG. 5 has a risk of impairing safety due to the difference in oxidative deterioration rate.

The present invention solves the above problems, and an object of the present invention is to provide a safe, highly reliable, and long-life positive resistance temperature coefficient heating element.

Means for Solving the Problems In order to solve the above problems, the present invention provides a long thin plate-shaped positive resistance containing a composition in which a conductive fine powder is dispersed in a crystalline polymer as a main component. At least one of the pair of electrode plates is provided with a resistor having a temperature coefficient, a pair of metal electrode plates provided on thin facing surfaces along the longitudinal direction of the resistor, and an insulator covering the metal electrode plate. Is a structure in which the edge surface portion along the longitudinal direction of the resistor is covered.

Action As in the above-mentioned configuration, by covering both edge surfaces along the longitudinal direction of the PTC resistor with the metal plate, the creeping portion formed by the resistor itself between the pair of electrode plates becomes one electrode plate. Since it can be configured on the same surface as that of the PTC resistor, it is possible to easily place a heat load body made of metal in this part, which causes the entire circumference of the PTC resistor to be covered with the metal body, which causes deterioration. It is difficult to remove, and every part of the resistor deteriorates at the same rate, and the temperature gradually decreases, allowing normal heat generation for a very long time, and a highly safe and long-life heating element is obtained. .

Embodiment An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a perspective view of a positive resistance temperature coefficient heating element showing a first embodiment of the present invention. In Fig. 1, 11 is 0.6 mm thick
Is a thin-plate-shaped PTC resistor of which the main component is a composition in which conductive fine powder is dispersed in a crystalline polymer. Metal plate electrodes 12 and 13 are adhered to the upper and lower surfaces, which are thin facing surfaces, along the longitudinal direction of the resistor 11. The electrode 12 is a copper plate having a thickness of 35 μm and having a U-shaped cross section so as to cover the upper surface and both edge surfaces of the resistor 11. Since it is bent in a U-shape, the bending rigidity in the longitudinal direction is also strong. The electrode 13 is a resistor with respect to the electrode 12.
11 is formed by providing a creeping portion 14 having a creeping distance of 2.5 mm formed by itself, and a copper plate having a thickness of 35 μm is also used. The electrodes 12 and 13 and the resistor 11 are covered with an insulator 15 made of vinyl chloride. The creeping portion 14 of the electrodes 12 and 13 is formed on the same surface as the electrode 13, and when a radiator plate (not shown) made of Al is attached to this portion 14 via an insulator 15 as a heat load body, the resistor 11 Is covered with metal in the entire circumferential direction, oxygen hardly permeates, and the resistor
All parts of 11 are less likely to deteriorate, generate normal heat for a long period of time, and have an excellent effect of being safe.

By the way, the PTC resistor 11 is a polymer composition containing a particulate conductive agent centered on carbon black. For example, the resin used therefor may be a polyethylene-vinyl acetate copolymer or a polyethylene-ethyl acrylate copolymer. Polyolefins such as polyethylene and polypropylene, and crystalline resins such as polyamide, polyvinylidene halide, and polyester are present, and each of them shows a sharp positive temperature coefficient near the crystal transformation point. Further, the distance between the pair of electrodes 12 and 13 is about 0.3 to 3 mm, the PTC resistor 11 may be a composition having a high specific resistance, and the PTC characteristic for positive self-temperature control can be easily obtained.

Therefore, the heating element of the present example, which has an Al heat radiating plate attached to the surface on the electrode 13 side, and the heating element of the conventional example shown in FIG. 5, which is covered with an insulator made of the same vinyl chloride, are used. 130 ° C
When placed in a constant temperature bath of No. 2 and taken out after 4000 hours and applied with AC100V, the conventional heating element cracked in the creeping part not covered with metal and sparked. On the other hand, the heating element of the present example had no abnormality in the resistor, and generated heat normally when AC100V was applied. The same 1 up to 10000 hours
After leaving it in a constant temperature bath at 30 ° C, I tried to apply AC100V, but even in this case, it generated heat safely without sparking. However, the exothermic temperature was lowered by about 3 ° C. Furthermore, at 15,000 hours continuously, although the temperature dropped by about 15 ° C, heat was safely generated, and the temperature gradually decreased at the end stage, confirming that it was safe. As described above, it has an excellent effect of safely generating heat for a long period of time and having high safety.

In addition, PTC heating elements are generally annealed after this processing to remove processing strain and stabilize resistance.However, in the conventional example, a flat metal plate is used due to the bimetal effect between the flat plate electrode and the PTC resistor. Although it was considerably distorted in the creeping portion between the electrodes, in this embodiment, the electrode 12 was bent in a U-shape and the bending rigidity was strong, so that the electrode 12 was easily attached to the heat dissipation plate with almost no distortion. Thus, there is also an effect that the thermal strain associated with the annealing treatment can be eliminated.

FIG. 2 shows the second embodiment. Like the first embodiment, the electrode 23 has the creeping portion 24 formed by the resistor 21 itself for the electrode 222 on the same surface, but the electrode 22 is in the longitudinal direction. Ear portions 26 extending on the same plane as the creeping portion 24 are formed on both edge portions, and also have an effect of increasing the thermal efficiency to a heat load body (not shown) attached to the electrode 23 side.

FIG. 3 shows a third embodiment, in which the electrodes 32 and 33 have the same shape and the resistors 31 for the electrodes 33 and 32 are formed on the same surface.
It has creepage portions 34a and 34b formed by itself, and the respective ears 36a and 36b are formed on the same plane as the creepage portions 34a and 34b, and the heat load body 37a is formed on both surfaces via an insulator 35 covering them. And 37b are pasted.

FIG. 4 shows the fourth embodiment, and the electrode 42 is the electrode 22 of FIG.
The other electrode 43 is joined to the other electrode 43 through an extremely thin insulator 48 having a thickness of, for example, 100 μm or less, which is arranged in the U-shape and has an ear portion.
The resistors 41 and 42 are configured to completely cover the resistor 41 without a creeping portion. In this case, similarly, after covering with an insulator (not shown) such as vinyl chloride, and attaching a heat load body (not shown) to the side of the electrode 43, power is supplied to parts A and B in FIG. Therefore, there is also an effect that a simple power feeding structure can be obtained without special processing of the heat load body. Besides, by adjusting the distance C in FIG. 4 by the length of the insulator 48, the resistance can be easily adjusted. Also, by using a polyester film preferably for the insulator 48, a capacitor and a PTC that are virtually formed in this portion.
Since a parallel circuit structure with the resistor 41 is provided, the current of the heating element is more stabilized, and there is also an effect of eliminating malfunctions when controlling the heating element. Such a structure can be easily processed by adhering the insulator 48 to the electrode 43 in advance.

The above embodiments do not refer to all structures of the heating element. For example, a portion not covered with metal is formed at the end in the longitudinal direction, the power feeding portion, etc., and the safety device is provided at the portion that deteriorates fastest. Such a configuration may be used.

EFFECTS OF THE INVENTION According to the present invention, it is possible to provide a structure in which the PTC resistor can be completely covered with a metal body, and the structure can be made extremely resistant to deterioration, and abnormal overheating, smoke generation, ignition, etc. which occur after long-term use. It eliminates the danger of and provides a safe, reliable and long-life heating element.

[Brief description of drawings]

FIG. 1 is a perspective view of a positive resistance temperature coefficient heating element showing a first embodiment of the present invention, and FIGS.
4 is a sectional view of a positive resistance temperature coefficient heating element, and FIG. 5 is a perspective view of a conventional positive resistance temperature coefficient heating element. 11,21,31,41 …… PTC resistor, 12,13,22,23,32,33,42,43
...... Electrodes, 14,24,34a, 34b …… Creepage, 15,35 …… Insulators, 26,36a, 36b …… Ears, 37a, 37b …… Heat load, 48…
… Second insulator.

Claims (4)

[Claims] 1. A long thin plate-shaped resistor having a positive resistance temperature coefficient, which is mainly composed of a composition in which conductive fine powder is dispersed in a crystalline polymer, and a longitudinal direction of the resistor. A pair of metal electrode plates provided on the thin opposing surfaces along with an insulator that covers the metal electrode plates, and at least one electrode plate of the pair of electrode plates covers the edge surface portion along the longitudinal direction of the resistor. A positive resistance temperature coefficient heating element configured. 2. An electrode plate of a pair of metal electrode plates covers both edge surfaces along the longitudinal direction of the resistor, and the other electrode plate is the same as the other electrode plate with respect to the one electrode plate. The positive resistance temperature coefficient heating element according to claim 1, which has a creeping portion formed by the resistor itself on the surface. 3. An electrode plate of a pair of metal electrode plates covers one of respective edge surfaces of the resistor along the longitudinal direction, one electrode plate being one electrode plate with respect to the other electrode plate. The positive resistance temperature coefficient heating element according to claim 1, which has a creeping portion formed by the resistor itself on the same plane as the above. 4. The pair of metal electrode plates are used to cover the entire surface of the resistor in the longitudinal direction by using both electrode plates, and the respective electrode plates are joined via a second insulator. The positive resistance temperature coefficient heating element described.