JPH07109787B2 - Positive resistance temperature coefficient heating element - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a heat collecting device and a structure of a heating element useful as 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) is disclosed in, for example, Japanese Patent Publication No. 57-43995 and Japanese Patent Publication No. 55-40161.
The structure is as shown in Japanese Patent Publication No. JP-A-2003-242, and it is self-controlled to an appropriate temperature by the PTC characteristics of the PTC resistor between the pair of electrodes.

However, especially when a large electrode density is required, it is essential to improve the temperature distribution in the direction between the pair of electrodes in order to make the temperature distribution of the heating element itself uniform.
As a solution to this problem, a method has been taken in which the distance between a pair of electrodes is close to each other, as shown in JP-A-60-28195 and FIG. In FIG. 3, 1a and 1b are a pair of parallel plate electrodes provided close to each other, and
By arranging the PTC resistor 2, it became possible to expose a high-output PTC heating element.

Problems to be Solved by the Invention It is indispensable to anneal these PTC heating elements in order to obtain a stable resistance value and eliminate processing strain.
In the case of actually using this PTC heating element, an insulator which is an outer layer of the PTC heating element is required. However, if the insulating material is coated after annealing, not only must measures be taken to prevent deterioration of the resistor and electrode body due to annealing, but also processing strains associated with this processing will occur.
It is possible to install it so that processing strain does not remain, but considering the adhesion of this PTC heating element to the object to be heated, it is not only difficult, but also the PT covered with this insulator
There is a risk that oxygen remains around the C resistor and the electrode body, the resistor and the electrode body deteriorate due to heat resistance, and sparks to ignite.

On the other hand, when annealing is performed in a state where the insulator and the PTC heating element are in close contact with each other after the insulator is covered, thermal stress such that the heating element is distorted or bent due to contraction of the insulator, thermal expansion of the electrode body, etc. There was a problem that not only the shape was distorted or bent, but also the resistance value could not be stabilized.

Means for Solving the Problems Technical means for solving the above problems are based on a composition in which a conductive fine powder is dispersed in a crystalline polymer containing a metal-adhesive functional group. A heating element having a thin positive temperature coefficient of resistance, a pair of electrode bodies made of metal provided to apply a voltage in the thickness direction thereof, and an insulator covering the resistor body and the electrode body, The insulator has a polymer layer having thermal adhesiveness with the electrode body and the contact surface with the resistor body, and after forming the resistor body, the electrode body and the insulator body integrally, Annealing is performed at a temperature higher than the melting point of the molecular layer to obtain a predetermined resistance value.

Action The action of this technical means is as follows. That is, when annealing is performed after forming the resistor, the electrode body, and the insulator covering them, thermal stress acts due to thermal stress due to the difference in thermal expansion and thermal contraction of each component, but the insulator resistor Also, there is a polymer layer having thermal adhesiveness with these on the contact surface with the electrode body, and the polymer layer is melted during annealing, so that each constituent member is free to undergo thermal expansion,
It is made possible to be heat-shrinked, the processing strain is removed without difficulty, and it becomes possible to realize a stable resistance value without thermal strain. Further, after cooling, everything is brought into close contact with each other, and the thermal efficiency is also improved.

Example Hereinafter, a first example of the present invention will be described with reference to the accompanying drawings.

In FIG. 1, reference numeral 3 is a thin-walled PTC resistor having a thickness of 0.5 mm, and metal plate-shaped electrodes 4 and 5 are bonded to the upper and lower surfaces of the resistor 3. Next, insulators 6 and 7 that cover the resistor 3 and the electrodes 4 and 5 are sequentially formed. The PTC resistor 3 is a polymer composition impregnated with a particulate conductive agent centering on carbon black. For example, the resin used for this is polyethylene-vinyl acetate copolymer, ionomer-polyethylene-ethyl acrylate copolymer. There are crystalline resins such as coalesced and various organic acid-modified polyethylenes, which show a sharp positive temperature coefficient near each crystal transformation point.

The distance between the pair of electrodes 4 and 5 is preferably 0.3 to 3 mm, and the PTC
The resistor 3 may be a composition having a high specific resistance, and the PTC characteristic for controlling the self temperature can be easily obtained. In this example, the melting point is 120.
An organic acid-modified polyethylene at ℃ was used.

Moreover, as the electrode, a copper foil having a thickness of 50 μm was used.

Next, as the insulator, an ionomer resin having a melting point of 99 ° C. was used on the side in contact with the resistor 3 and the electrodes 4 and 5, and a chlorinated polyethylene resin was used on the outside thereof.

As described above, after the resistor 3, the electrodes 4 and 5, and the insulators 6 and 7 are all integrally formed, annealing is performed at 150 ° C. for 5 hours. However, surprisingly, despite the expansion of the electrodes 4 and 5 and the contraction of the insulator 7 at the annealing temperature of 150 ° C., the shape is smooth without thermal strain, bending, etc., and the sample n = 20. The individual pieces had an excellent effect that the variation of the resistance value was ± 3% or less. This is because the melting point of the insulator 6 was lower than the annealing temperature, so that the insulator 6 melted during annealing, and the electrodes 4 and 5 and the insulator 7 freely moved and did not generate thermal stress. Also, since the melting point of the insulator 6 is preferably lower than that of the resistor 3, the resistance of the resistor is maintained after the resistor is completely held in its shape during cooling of annealing. The stabilization of the value is further enhanced. Furthermore, after annealing, everything is completely and integrally bonded, so that it also has the effect of increasing the thermal efficiency of this heating element to the heat load element. In addition, since the pair of electrodes are very close to each other in the configuration of this heating element, there is a risk of sparks and the like due to burr distortion of the electrode body in the creeping portion, but the resistor 3 is placed between the pair of electrodes 4 and 5. Safety can be improved by making the creepage distance larger than the distance.
Further, preferably, not only can this safety be further enhanced by adopting a structure in which the electrode end face portion is also covered with a resistor, but also the degree of adhesion with an insulator can be enhanced, and low resistance sparks due to oxygen deterioration, etc. Danger can also be prevented.

On the other hand, the part A covered with the metal electrodes 4 and 5 has very excellent heat deterioration resistance, but the other creeping parts deteriorate quickly, and there is a risk of low resistance at high temperatures and sparks. However, it has a compatibility with the insulator 6, and this creeping portion also has the effect of increasing the resistance by melting the resin of the insulator 6 during annealing and increasing the safety. This effect is further enhanced by adding a safety agent such as an antioxidant that improves the heat resistance and increases the resistance value to the insulator 6.

Next, a second embodiment of the present invention will be described with reference to FIG.

The same parts as those in the first embodiment are designated by the same reference numerals. The electrodes 4 and 5 are formed on both sides of the resistor 3, and the insulators 6a and 7a are sealed from above and the insulators 6b and 7b are sealed from below and bonded to each other.
Polyester film is used for a and 7b. Ionomer resin impregnated with carbon black is used for the resistor, and not only the excellent effect similar to that of the first embodiment can be obtained by annealing at 150 ° C. for 4 hours, but the film is not formed by the insulator. It is possible to realize with very simple processing equipment such as bonding two sheets.

As described above, the present invention is a PTC heating element with a large electrode area in which the electrode spacing is very close to each other. It also enables a stable and excellent heating element structure. The resulting PTC heating element has a high calorific value and high reliability, and breaks the concept of the conventional PTC heating element.

[Brief description of drawings]

FIG. 1 is a perspective view of a positive resistance temperature coefficient heating element of a first embodiment of the present invention, FIG. 2 is a perspective view of a positive resistance temperature coefficient heating element of a second embodiment of the present invention, and FIG. It is a perspective view of the conventional positive resistance temperature coefficient heating element. 3 ... PTC resistor, 4,5 ... electrode, 6,7,6−a, 6−b, 7−a, 7
-B ... Insulator.

Claims (5)

[Claims] 1. A thin-walled resistor having a positive temperature coefficient of positive resistance, which is mainly composed of a composition in which electrically conductive fine powder is dispersed in a crystalline polymer containing a metal-adhesive functional group, and its thickness direction. A pair of electrode bodies made of metal provided to apply a voltage to, and an insulator covering the resistor body and the electrode body,
The insulator has a polymer layer having thermal adhesiveness with the electrode body and the contact surface with the resistor body, and after the resistor body, the electrode body and the insulator body are integrally formed, A positive resistance temperature coefficient heating element obtained by annealing at a temperature higher than the melting point of the polymer layer to obtain a predetermined resistance value. 2. An end face in which a resistor and an electrode body are integrally adhered to each other, and a creepage distance between end faces of the electrode bodies is larger than a thickness dimension of the resistor. A positive resistance temperature coefficient heating element as described in the item. 3. The positive resistance temperature coefficient heating element according to claim 1, wherein the polymer layer of the insulator is made of a material having a melting point equal to or lower than that of the resistor. 4. A positive resistance temperature coefficient heating element according to claim 1 or 2, wherein an end face of the electrode body is covered with a resistor. 5. The positive resistance temperature coefficient heating element according to claim 1, wherein the adhesive polymer layer of the insulator is added with an additive for increasing the resistance value of the resistor. .