JPH0316758B2 - - Google Patents

Description

[Detailed description of the invention]

SUMMARY OF THE INVENTION An object of the present invention is to provide, at a low cost, a heating element device that generates a large amount of heat and has good moisture resistance and corrosion resistance at the connecting portion of electrodes. A positive temperature coefficient thermistor has a characteristic that its resistance value increases rapidly at a certain temperature (Curie temperature). Therefore, it has a self-temperature control effect in that when it is energized, the temperature it generates remains almost constant regardless of fluctuations in ambient temperature or voltage.
Therefore, various heating elements have been devised by utilizing the properties of this positive temperature coefficient thermistor. Furthermore, by applying air to this heating element, it can be used as a hot air heater that heats the air. In order to increase the heat output of the above-mentioned heating element and obtain a large output, it is effective to increase its heat dissipation coefficient, and for this purpose, heat dissipation fins with a large surface area and high thermal conductivity are used. A method is known in which it is closely fixed to a characteristic thermistor. It is also known that the heat dissipation fins are preferably made of aluminum or an alloy containing aluminum as a main component in consideration of cost, specific gravity, thermal conductivity, workability, and the like. Furthermore, in order to apply a voltage to the positive temperature coefficient thermistor, if the heat dissipation fins are also used, the structure is simplified and new electrode terminal parts are not required. Now, at this time, the aluminum heat dissipation fin becomes a conductive path and must be connected to external connection terminals and lead wires. Copper or a copper alloy is generally used for these connection terminals and lead wires because it is a good electrical conductor. However, if copper or copper alloy is connected to aluminum heat dissipation fins, if left in a humid environment for a long time or if the connection becomes condensed, a local battery will occur and aluminum, which is a base metal, will There is a risk of corrosion. For this reason, in the past, in order to prevent corrosion of the connection part and obtain complete reliability, it was necessary to cover the connection part with resin so as not to expose it to the air. Figure 1 shows such a conventional heating element device, in which heat dissipation fins 3, 3' made of aluminum plates or aluminum alloy plates are adhered to a positive temperature coefficient thermistor 1, which has electrodes 2, 2' on both sides. The heat dissipation fins 3,
Copper wires 4, 4' are connected to a part of 3' by soldering, welding, etc., and the connection part is covered with epoxy resin 5, 5'.
It is covered with etc. In this way, in the conventional example, the connection between the aluminum heat dissipation fin and the copper or copper alloy was covered with resin, which was a necessary and sufficient measure, but it was not perfect, required extra material cost, and required a lot of assembly man-hours. There was a drawback. The present invention has been made to eliminate the above-mentioned conventional drawbacks. That is, the present invention proposes a heating element device in which aluminum or an aluminum alloy is electrically connected to copper or a copper alloy through another metal that is less susceptible to electrolytic corrosion. First, the inventors selected stainless steel, nickel, zinc, and brass as other metals in terms of cost, ease of acquisition, workability, etc., and each
A copper plate and an aluminum plate were brought into contact with both ends of a plate cut into a size of 200 mm x 0.2 mm, and tests were conducted in humidity and water. The table below shows the corrosion results of the contact area after 500 hours.

[Table] Here, the mark ◯ indicates that there is almost no corrosion and there is no problem in practical use, and the mark x indicates that the corrosion has progressed and it cannot be used in practical use. Therefore, from the above results, the present inventors found that stainless steel has no corrosion problem compared to both copper and aluminum. The same results were obtained for aluminum alloys and copper alloys. The present invention has been made in view of these points, and one embodiment thereof is shown in FIG. As shown in the figure, electrodes 7 and 7' are provided on both sides of a thin plate-shaped positive temperature coefficient thermistor 6 by spraying aluminum. Heat dissipation fins 8, 8' made of aluminum or aluminum alloy are closely fixed to both surfaces of the positive temperature coefficient thermistor 6 with a conductive adhesive (not shown). 9 and 9' are terminal plates made of stainless steel with spring properties, and are connected to the heat dissipation fins 8,
8' by appropriate means. Therefore,
The heat dissipation fins 8, 8' and the terminal plates 9, 9' constitute a heat dissipation body that also serves as a power supply path.
When a current is passed through 9', the positive temperature coefficient thermistor 6 generates heat. According to this embodiment, the stainless steel is in contact with the heat dissipation fin made of aluminum or aluminum alloy, and it can be connected to an external conductive part such as a copper wire through the stainless steel.
Therefore, there is no corrosion even without special measures such as resin sealing for each connection part, and a highly reliable heating element device can be provided at low cost with a simple configuration. FIG. 3 shows another embodiment of the invention. In this embodiment, aluminum plates 10, 10' are fixed to a positive temperature coefficient thermistor 6 with electrodes (not shown) on both sides using a conductive adhesive (not shown), and the aluminum plates 10, 10' and the stainless steel plate Heat radiation fins 11 and 11' formed by bending an aluminum brazing sheet into a wave shape are sandwiched between the heat dissipating fins 12 and 12', and are fixed by brazing, respectively. Therefore, these aluminum plates 10, 10',
radiation fins 11, 11' and stainless steel plate 12,
12' constitutes a heat sink. and,
Current is supplied through the stainless steel plates 12, 12', to which external copper wires or the like can be directly connected. Here, the aluminum plates 10 and 10' may be aluminum alloy plates, and the portion that becomes the electrode terminal plate is the stainless steel plate 1.
2, 12', the radiation fins 11,
The other aluminum plate 10, 1 sandwiching 11'
0' may be a stainless steel plate.
Furthermore, the radiation fins 11, 11' may be made of aluminum plates or aluminum alloy plates. According to this second embodiment, it becomes easy to connect external copper wires, etc., and corrosion of the connecting parts does not occur, and furthermore, an aluminum brazing sheet or an aluminum plate formed by bending into a corrugated shape as a heat dissipation fin can be used. , it is easy to obtain thin heat dissipation fins with a large surface area. Therefore, when used as a hot air heater, low pressure loss and high output can be obtained at the same time, and the weight of the heat dissipation fin can also be reduced. In addition, since the stainless steel plate is connected with brazing, the strength is high, and there is no risk of contact failure due to changes or variations in the pressing force of the spring plate, unlike when pressing with a spring plate, and a perfect electrical connection can be obtained. . As explained in detail above, the present invention consists of a metal heat sink mainly made of aluminum or its alloy, which has a large heat dissipation effect and good conductivity, and uses stainless steel for the part corresponding to the electrode extraction part. It is characterized by: This configuration eliminates the risk of electrolytic corrosion in connection with external electrode lead wires made of copper or copper alloy.
Moreover, joining aluminum and stainless steel can be easily formed by appropriately selecting brazing conditions, and connecting stainless steel and copper wires is extremely easy as a general technique, making manufacturing simple. Its reliability has been greatly improved, and the practical effects are extremely large.

[Brief explanation of the drawing]

FIG. 1 is a perspective view of a heating element device in a conventional example.
2 and 3 are perspective views showing embodiments of the heating element device according to the present invention, respectively. 6... Positive characteristic thermistor, 7, 7'... Electrode,
8, 8', 11, 11'...radiating fin, 9, 9'
...Terminal board (stainless steel), 10,10'...aluminum plate, 12,12'...stainless steel plate.

Claims (1)

[Claims] 1. In a heating element device in which electrodes are provided on both sides of a thin plate-shaped PTC thermistor, a metal heat radiator is closely fixed to the PTC thermistor, and the metal heat radiator also serves as a current feeding path, the metal The heat sink is made of aluminum or an aluminum-based alloy, and stainless steel is electrically connected to the metal heat sink, and copper or copper-based lead wires or terminal plates for power supply are electrically connected to the stainless steel. A heating element device connected to