JP2734250B2 - Positive resistance temperature coefficient heating element - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a positive resistance temperature coefficient heating element used for a warming device and a general heating device.

[0002]

2. Description of the Related Art A conventional cylindrical temperature coefficient of positive resistance (hereinafter referred to as P
The heating element is a resistor 9 having a PTC provided between a pair of electrode wires 7 and 8 as shown in FIG.
And an electrical insulator 10 for covering the electrode wires 7 and 8 and the resistor 9. The temperature of the heating element was self-controlled to a constant temperature by the PTC characteristic of the resistor 9. In such a configuration, when a large power density is required, in order to make the temperature distribution of the heating element uniform, it is essential to improve the temperature distribution in the direction between the pair of electrode wires. As a solution, a means has been adopted in which the distance between the pair of electrode wires is made closer to each other. The resistor 9 is obtained by dispersing a conductive powder in a crystalline polymer, cross-linking with a cross-linking agent such as an electron beam or an organic peroxide, and then processing the finely-divided conductive particles into a long cylindrical shape. Met.

[0003]

However, in the above-mentioned conventional PTC heating element, the resistance value easily changes due to the use of current, and a stable output cannot be obtained. In order to obtain a low resistance value, it is necessary to apply a voltage of 70 V or more.
At a voltage of 0 V or less, no current flowed and no heat was generated. Therefore, it is not suitable for a battery-driven heating element.

An object of the present invention is to solve the above-mentioned problems, and to provide a PTC heating element which generates heat at a low voltage, can stably maintain a resistance value, is safe and can withstand long-term use. .

[0005]

In order to achieve the above object, a PTC heating element according to the present invention is obtained by dispersing a conductive powder in a crystalline polymer and using a crosslinking agent such as an electron beam or an organic peroxide. After crosslinking, the finely divided conductive particles and the average particle size are 40
A long columnar resistor having a temperature coefficient of positive resistance kneaded with a conductive composition obtained by dispersing carbon of about 120 nm in a crystalline polymer, and a spiral along the longitudinal direction of the resistor. A configuration is provided that includes a pair of wound electrode wires that pass at equal intervals and an electrical insulator that covers the resistor and the resistor.

[0006]

According to the above construction, the workability and safety of the heating element are maintained by the conductive particles, and the conductivity is supplemented by carbon.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A PTC heating element according to an embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a top view of a PTC heating element according to the present embodiment, and a pair of equally spaced metal electrode wires spirally wound along a longitudinal direction of a long cylindrical PTC resistor 1. 2 (a copper wire having an outer diameter of 0.1 mm and twisted into 16 strands) and a metal electrode wire 3 (the same configuration as the electrode wire 2) are provided, and the whole is made of an electric insulator 4 (polyvinyl chloride or the like). Cover and PT
C heating element.

The resistor 1 comprises the following composition. Polyethylene is used as the crystalline polymer, and 60 is used as the conductive powder.
100 parts by weight of a low-density polyethylene kneaded product containing 0.5% by weight of furnace black and 4.5 parts by weight of dicumyl peroxide as a cross-linking agent were blended and subjected to a heat treatment at 180 ° C. for 1 hour to obtain a frozen product. Pulverization produced conductive particles having an average particle size of about 50 μm. afterwards,
A mixture consisting of the conductive particles 1a (FIG. 1) and carbon 1b having an average particle diameter of 70 nm (FIG. 1) at a ratio of 10: 1 was kneaded in high-density polyethylene so that the total carbon content was 50% by weight. The resistor was processed into a long cylindrical shape to obtain a resistor 1. This resistor 1 showed a volume resistivity of 6 × 10 ² Ωcm. Also, when power is supplied at DC12V, about 63
C. indicated a saturation temperature.

As a comparative example, one using carbon having an average particle diameter of 20 nm was prepared. Then, a continuous energization durability test at an applied voltage of 12 V was performed on the example and the comparative example. As a time when the resistance value change rate reaches −50%, the comparative example is 10 times.
Although it was less than 00 hours, in the example, there was almost no change in the resistance value even after 3000 hours had elapsed, and the stability of the resistance value due to energization was excellent.

The relationship between the average particle diameter of carbon, the volume resistivity and the rate of change of resistance in this embodiment is as shown in FIG. 2, and is stable at 40 to 120 nm.

In the figure, ● and Δ indicate that the average particle size is 51 nm or 10 nm.
It is a volume specific resistance value and a resistance value change rate when using a mixture of 2 nm carbon in a ratio of 1: 1 (weight ratio).

Although polyethylene is used as the crystalline polymer in the examples, a similar effect can be obtained by using polyamide, ethylene-vinyl acetate copolymer or polypropylene instead.

[0014]

As is apparent from the above description, according to the present invention, heat is generated at a low voltage, and the resistance can be stably maintained.
A positive resistance temperature coefficient heating element that is safe and durable for long-term use can be obtained.

[Brief description of the drawings]

FIG. 1 is a top view of a positive resistance temperature coefficient heating element according to an embodiment of the present invention.

FIG. 2 is a characteristic diagram of average particle diameter, volume resistivity, and resistance change rate of carbon.

FIG. 3 is a top view of a conventional positive resistance temperature coefficient heating element.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Positive resistance temperature coefficient resistor 1a Conductive particle 1b Carbon 2,3 Electrode wire 4 Electric insulator

Claims (2)

(57) [Claims] 1. After dispersing a conductive powder in a crystalline polymer and crosslinking with a crosslinking agent such as an electron beam or an organic peroxide,
A long columnar resistor having a positive resistance temperature coefficient obtained by kneading finely divided conductive particles and a conductive composition in which carbon having an average particle size of 40 to 120 nm is dispersed in a crystalline polymer, A positive-resistance temperature coefficient heating element comprising a pair of electrode wires wound in a spiral shape along the longitudinal direction of the resistor and passing at equal intervals and an electrical insulator covering the resistor and the resistor. . 2. The heating element according to claim 1, wherein the carbon has two or more different average particle diameters.