JPH03179688A - Positive characteristic thermistor heating element - Google Patents

Abstract

PURPOSE:To reduce the number of circuit to which a bonding agent is applied, so as to reduce an assembly manhour, and to eliminate the crack of an insulating plate by applying and fixing an insulating coating layer on the surface where it is abutted on a positive characteristic thermistor on a metallic radiator. CONSTITUTION:A bonding agent 6 is applied on both surfaces of a positive characteristic thermistor, 1 and common electrode plates 5 are abutted on both sides thereof, while the bonding agent 6 is applied on the surface of an insulating coating layer 7 applied and fixed on the surface where it is abutted on the positive characteristic thermistor 1 of a metallic radiator 3, which is pressued on each of the both sides of the common electrode plates 5, and is fixed by hardening the bonding agent 6. The common electrode plate 5 and the metallic radiator 3 are insulated with each other through the insulating coating layer 7 preliminarily formed on the one side surface of the metallic radiator, and there is no possibility of causing electric shock, even when the metallic radiator 3 is touched by hand. When a silicon bonding agent is used as the bonding agent 6, each of the parts can be fixed solidly. The number of application of the bonding agent is reduced, and the assembly work is facilitated as well, while the crack of the insulating plate at the time of assembly pressurization can be eliminated thereby.

Description

[Detailed Description of the Invention] Industrial Field of Application The present invention relates to a positive temperature coefficient thermistor heating element having self-temperature control characteristics using a positive temperature coefficient thermistor, and in particular to a positive temperature coefficient thermistor heating element that uses a metal heat sink to increase the amount of heat generated. This relates to a heating element for hot air.

A positive temperature coefficient thermistor, which is well known in the prior art, is a semiconductor ceramic whose resistance value rapidly increases when the temperature exceeds a certain temperature (Curie temperature).

On the other hand, when pressure is applied, it generates heat, and once the Curie temperature is exceeded, the temperature stops rising and remains at a constant temperature. Therefore, it is widely used as a safe heating element that does not overheat. Furthermore, in order to increase the amount of heat generated by such a heating element, several methods have already been proposed for fixing a metal heat sink to a positive temperature coefficient thermistor. One of them is a structure in which a metal heat radiator is directly fixed to the electrode of a positive temperature coefficient thermistor, and the metal heat radiator also serves as a power supply terminal. There are also products whose metal heat sinks are insulated so that they are safe even when touched by hands or metal rods.

4 and 6 are a perspective view and an exploded perspective view of a conventional positive temperature coefficient thermistor heating element, and FIG. 6 is an enlarged sectional view of a main part. In FIGS. 4 to 6, reference numeral 1 denotes a positive temperature coefficient thermistor, and electrodes 2 provided by aluminum spraying or the like are provided on both sides of the thermistor. 3 is a metal heat sink made of a material with good thermal conductivity, such as aluminum, and has a large number of through holes formed therein to increase its surface area. and,
Three of the positive temperature coefficient thermistors 1 are arranged so that the electrodes on both sides are in one plane, and the metal heat radiator 3 on the bottom of the tank is
The picture electrode 2 of the three positive temperature coefficient thermistors 1 is used.
The two metal heat radiators 3 were fixed to each other with an adhesive 6, with an insulating sheet 4 made of alumina or the like and a common electrode plate 6 made of a thin aluminum plate interposed between the surfaces.

Problems to be Solved by the Invention However, the conventional PTC thermistor heating element as described above has the following problems. A common electrode plate was required to supply electricity to the positive temperature coefficient thermistor. Therefore, it is necessary to fix these with an adhesive, which requires applying the adhesive many times, which is very time-consuming.

In other words, if the metal heat radiator was directly fixed to the electrodes of a positive temperature coefficient thermistor, it would be sufficient to apply adhesive once between them, but because the metal heat radiator is insulated, the adhesive can be applied once. It required three times: between the heat sink and the insulating sheet, between the insulating sheet and the common electrode plate, and between the common electrode plate and the positive temperature coefficient thermistor, and six times for both sides, which was very time-consuming. .

In addition, if an attempt is made to increase the amount of heat generated by the positive temperature coefficient thermistor heating element, the heat generation temperature will be 200° C. or higher, but in this case, the insulating sheet must have heat resistance. Here, an alumina porcelain board is often used as an insulating sheet with excellent heat resistance, but if the board is thin (0.
, 5mm or less), and the adhesion surface (fixed surface) of metal heat sinks and positive temperature coefficient thermistors because they are easily broken when pressure is applied during bonding.
There was a problem in that it was necessary to increase the smoothness of the surface, making it expensive. On the other hand, if the plate thickness is thicker than the above, there is a problem in that the plate itself absorbs heat, resulting in heat loss and a loss in calorific value.

It is also possible to use organic films such as polyimide, but in this case they are soft and can absorb the warping of metal heat sinks and positive temperature coefficient thermistors, but these have low heat resistance and have low surface activity. Because of the low temperature, there was not enough adhesive.

The present invention has been made in view of the above-mentioned conventional problems.It reduces the number of adhesive application circuits, reduces assembly man-hours, solves the problem of cracking of insulating plates, and also provides strong bonding. The object of the present invention is to provide a positive temperature coefficient thermistor heating element.

Means for Solving the Problem In order to solve this problem, the present invention comprises a plurality of positive temperature coefficient thermistors each having electrodes on both sides, and a common electrode plate made of a thin metal plate interposed between the electrode surfaces of the thermistors. an insulating coating layer is thinly coated and fixed on the surface of at least one of the metal heat sinks that comes into contact with the PTC thermistor, and the common electrode plate is electrically connected to the electrodes of the PTC thermistor. >9, and the insulating coating layer insulates the electrodes of the positive temperature coefficient thermistor and the metal heat sink, and the positive temperature coefficient thermistor, the common electrode plate, and the metal heat sink are fixed with an adhesive. The configuration is as follows.

Function: According to this configuration, the number of applications of adhesive is reduced, which reduces the labor required for assembly.It also solves the conventional problem of cracking of the insulating plate during assembly pressurization, and improves reliability. This makes it possible to provide a thermistor heating element with high positive temperature coefficient.

EXAMPLE Hereinafter, an example of the present invention will be described with reference to FIGS. 1 to 3, with the same numbers assigned to the same parts as in the conventional example.

In FIGS. 1 to 3, reference numeral 7 denotes an insulating coating layer made of, for example, alumina, which is thinly coated and fixed on the surface of the metal heat sink 3 that comes into contact with the PTC thermistor 1. This insulating coating layer 7 is made of aluminum oxide, silicon oxide,
Either one of aluminum nitride or silicon nitride is used to form the insulating coating layer 7 of a certain thickness by plasma spraying, or a flucoxide solution of one of the above materials is sprayed and heat treated to form an insulating coating layer 7 of a certain thickness. This is achieved by forming a thick insulating coating layer. and,
The positive temperature coefficient thermistor 1 provided with these electrodes 2, the common electrode plate 6, and the metal heat sink 3 having an insulating coating layer 7 coated and fixed on one side of the positive temperature coefficient thermistor 1 are sequentially attached to the common electrode plate 5 on both sides of the positive temperature coefficient thermistor 1. , is in contact with the metal heat radiator 3, and is fixed with, for example, a silicon adhesive e.

Further, as shown in FIG. 3, the common electrode plate 3 is in contact with a minute convex portion on the electrode 2 surface of the positive temperature coefficient thermistor 1.

When assembling this positive temperature coefficient thermistor heating element, the adhesive 6 is applied to both sides of the positive temperature coefficient thermistor 10, and the common electrode plate 6 is brought into contact with both surfaces, which are then brought into contact with the positive temperature coefficient thermistor 1 of the metal heat sink 3. The adhesive 6 may be applied to the surface of the insulating coating layer 7 that has been applied and fixed in advance to the surface, pressed against both sides of the common electrode plate 5, and the adhesive 6 cured and fixed. At this time, the common electrode plate 5 and the metal heat sink 3 are insulated by the insulating coating layer 7 formed in advance on one side of the metal heat sink 3, so that even if the metal heat sink 3 is touched, You won't get an electric shock. In addition, when a silicone adhesive is used as the adhesive 6, it has good heat resistance and elasticity, so it can be used for a heating element and for bonding materials with different coefficients of thermal expansion, such as ceramics and metals. , is optimal. In addition, many of them have self-adhesive properties, so they adhere the above-mentioned parts very firmly.

As described above, according to this embodiment, the number of times the adhesive is applied can be reduced, and the effort required for assembly can be reduced. Since the casing does not use an insulating sheet as in the conventional case, the number of assembly parts is reduced, so a highly reliable positive temperature coefficient thermistor heating element can be provided.

In the above embodiment, a case has been described in which both of the metal heat sinks 3 located on both sides of the PTC thermistor 10 are insulated, but it is also possible to insulate only one of them.

Effects of the Invention As described above, according to the present invention, an insulating coating layer is applied and fixed to the surface of at least one metal heat sink that comes into contact with the PTC thermistor, thereby reducing the number of adhesive applications. This can reduce assembly effort. In addition, since the conventionally used insulating sheet is not used, the number of parts can be reduced, and the problem of cracking of the insulating sheet during assembly and pressurization, which was a big problem in the past, has been solved, resulting in a highly reliable A characteristic thermistor heating element can be provided.

[Brief explanation of drawings]

Fig. 1 is a perspective view of a PTC thermistor heating element that can be pressed according to an embodiment of the present invention, Fig. 2 is an exploded perspective view of the same, Fig. 3 is an enlarged sectional view of the same main part, and Fig. 4 is a conventional button FIG. 5 is an exploded perspective view of the positive temperature coefficient thermistor heating element, and FIG. 6 is an enlarged sectional view of the main part thereof. 1... Positive temperature coefficient thermistor, 2... Electrode, 3... Metal heat sink, 6... Common electrode plate, 6... Adhesion agent, 7...insulating coating layer.

Claims (1)

[Claims] Multiple positive temperature coefficient thermistors with electrodes on both sides,
A metal heat sink is brought into contact with the electrode surface with a common electrode plate made of a thin metal plate interposed therebetween, and a thin insulating coating layer is provided on the surface of at least one of the metal heat sinks that comes into contact with the positive temperature coefficient thermistor. The common electrode plate is coated and fixed, and the common electrode plate is electrically connected to the electrode of the PTC thermistor, and the insulating coating layer insulates the electrode of the PTC thermistor and the metal heat sink, and the A positive temperature coefficient thermistor heating element in which the positive temperature coefficient thermistor, common electrode plate, and metal heat sink are fixed with adhesive.