JPS6255887A - Positive temperature coefficient thermistor heat generating body and manufacture thereof - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a positive temperature coefficient thermistor heating element used in clothes dryers and various heaters, and a method for manufacturing the same.

BACKGROUND OF THE INVENTION Conventionally, a positive temperature coefficient thermistor heating element has a barium titanate positive temperature coefficient thermistor element attached with heat dissipation fins to improve the efficiency of heat dissipation. (For example, JP-A-58-11767
No. 4 uses an aluminum plate processed into a corrugated shape as a radiation fin. 1) In general, such heat dissipating fins are closely fixed with a silicone-based or polyamide-based heat-resistant resin adhesive.

Problems to be Solved by the Invention In such conventional PTC thermistor heating elements, heat dissipation fins made of metal such as aluminum are closely fixed to the PTC thermistor element with heat-resistant resin, so there is a problem in the relationship between the metal and the PTC thermistor element. The difference in thermal expansion coefficients caused cracks in the element and corrosion of the metal, causing problems in terms of reliability. In addition, various reducing decomposition gases are generated due to deterioration of the heat-resistant resin used for tightly fixing the metal heat dissipating fins, which deteriorates the withstand voltage characteristics, making it difficult to use in a high-temperature atmosphere.

The present invention has been made in view of the above, and an object of the present invention is to provide a positive temperature coefficient thermistor heating element that is highly reliable, can be used up to high temperatures, and has excellent thermal efficiency, and a method for manufacturing the same.

Means for Solving the Problems In order to solve the above problems, the present invention is made by processing a barium titanate-based positive temperature coefficient thermistor into a spiral shape, and by processing a barium titanate-based positive temperature coefficient thermistor into a rod-like shape. After extrusion molding, a positive temperature coefficient thermistor heating element is obtained by spirally molding while moving a take-up reel. 1. Effects The effects of the technical means of the present invention are as follows. That is, by having a helical structure, it has a large surface area and efficiently dissipates heat. Furthermore, this effect is increased by applying a metal layer such as λg, Ni, etc. by electrode treatment on the surface.

In addition, since metal heat dissipation fins are not used, there is no cracking due to the difference in thermal expansion coefficient between the metal and PTC thermistor element, and no deterioration of withstand voltage characteristics due to decomposition of the heat-resistant resin used for tightly fixing the element. A positive temperature coefficient thermistor heating element with excellent thermal efficiency and reliability can be obtained.

By the way, for forming complex spiral structures, ordinary dry forming,
This is difficult to achieve with injection molding, but extrusion molding according to the present invention, drying the extruded molded product to a moisture content of 2 to 8 wt%, and then molding while moving the take-up reel produces the least amount of molding distortion and is superior in mass productivity. ing. Further, by arbitrarily selecting the diameter and moving speed of the take-up reel, a molded body having a helical structure with an arbitrary diameter and pitch can be obtained. Here, the water content was limited to 2 to 8 wt% because 2W
If it is less than t, the flexibility will be insufficient and cracks will occur during winding with a take-up reel, and molding distortion will remain, resulting in cracks and deformation during firing. Moreover, if it exceeds 8 wt%, it is not preferable because deformation occurs during winding or cracks occur due to rapid moisture scattering during firing.

As a result, a positive temperature coefficient thermistor heating element that has excellent thermal efficiency and reliability and can be used in a high-temperature atmosphere is obtained.

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

A barium titanate-based positive temperature coefficient thermistor raw material having an average particle size of 1.4 μm and the following composition was used.

(BN2.78 PbO, 22) Ti1.020zo
4+ 0-0010Nb20s+ 0.0028i02
+0.0006 MnO2 Next, a) Ceramic raw material 10kgb) Methyl cellulose 340y C) Glycerin 4eo (/d) Pure water 2.11 were blended and kneaded to produce a clay for extrusion molding. This clay was put into the extrusion molding apparatus 1 shown in FIG.
A rod-shaped molded body 2 having a through hole with a wall thickness of 3H was produced by extrusion molding. Next, the rod-shaped molded body 2 was dried in an infrared drying device 3 to a moisture content of 4 wt%, and then a diameter of 30
A helical molded body according to the present invention was created while moving the take-up reel 4 of ff perpendicular to the moving direction of the extrusion molded body. Next, the molded body thus obtained was fired at 1300°C for 1 hour. Further, ohmic electrodes were formed on the outer and inner surfaces of the obtained sintered body by electroless nickel plating, and then terminal electrodes were soldered using high temperature solder having a melting point of 300'C.

FIG. 1 shows the spiral positive temperature coefficient thermistor heating element 6 thus obtained.

Effects of the Invention Due to the structure of the present invention as described above, it can be used in a high-temperature atmosphere with excellent thermal efficiency and reliability without using metal heat dissipation fins or heat-resistant resin for closely fixing them. The positive temperature coefficient thermistor heating element has excellent mass productivity and can be provided at low cost, making it extremely useful in practice.

[Brief explanation of drawings]

FIG. 1 is a perspective view of a helical PTC thermistor heating element according to an embodiment of the present invention, and FIG. 2 is a sectional view showing an apparatus for manufacturing a helical PTC thermistor heating element of the present invention. DESCRIPTION OF SYMBOLS 1... Extrusion molding device, 2... Rod-shaped molded product, 3... Infrared drying device, 4... Winding 1-roll, 6... ...Spiral positive temperature coefficient thermistor heating element.

Claims (2)

[Claims] (1) A PTC thermistor heating element characterized by processing a barium titanate PTC thermistor into a spiral shape. (2) A positive temperature coefficient thermistor heating element characterized by extruding a barium titanate positive coefficient thermistor into a rod shape, drying it to a water content of 2 to 8 wt%, and forming it into a spiral shape while moving a take-up reel. manufacturing method.