JPH05114461A - Heating body of positive characteristic thermistor - Google Patents

Abstract

PURPOSE:To provide substantially uniform thermal distribution by distributing metal electrodes irregularly for the principal plane of a positive characteristic thermistor element. CONSTITUTION:A metal electrode 1 is made to have the same rectangular form as the principal plane of a positive characteristic thermistor element 2, and another metal electrode 3 is made to have a form with a triangular portion removed from a rectangular area. As a result, the temperature of the principal plane of the element 2 drops where the electrode 3 is cut out. On the other hand, more heat radiation takes place at the left end of the element 2 and, therefore, temperature becomes higher at the left end than at a center position. Also, when several of the same element 2b are so arranged as to be adjacent to one another and electric current is caused to flow between the electrodes 1 and 3 of a resulting long-sized thermistor heating body, a surface temperature difference becomes small. When a large-sized heating body is constituted of many elements 2, therefore, temperature gradient at an element boundary becomes small, and substantially uniform thermal distribution can be provided.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a PTC thermistor heating element, and more particularly to a PTC thermistor heating element including a plurality of PTC thermistor elements.

[0002]

2. Description of the Related Art A PTC thermistor element has a low resistance value at room temperature, but when the temperature exceeds the switching temperature,
It has the property that the resistance value rapidly increases. For this reason, when a current is passed through the PTC thermistor element, the temperature rises due to heat generation, but above the switching temperature, the amount of heat generation decreases due to the increase in resistance, and the amount of heat radiation is balanced and stabilized. Therefore, the PTC thermistor element does not generate much heat above the switching temperature and is used as a safe heating element. The temperature on the surface of such a positive temperature coefficient thermistor heating element is constant under the same heat radiation conditions.

However, since heat is radiated from the side surface of the main heat radiating surface in addition to the main heat radiating surface, the temperature in a small portion of the outer circumference of the main heat radiating surface is slightly low.

[0004]

When the heat radiation condition is constant on the heat radiation surface, the positive temperature coefficient thermistor element functions as a uniform heating element. Further, when a part of the heat radiation surface is cooled, the resistance of the positive temperature coefficient thermistor element decreases due to the temperature decrease, and the current density of the part increases, and a self-adjusting function for maintaining uniform heating works. However, in practical use, the heat dissipation conditions are often different, and this difference in the heat dissipation conditions often exceeds the self-adjusting function of the positive temperature coefficient thermistor element, and the positive temperature coefficient thermistor element is no longer a uniform heating element.

That is, the positive temperature coefficient thermistor heating element up to now does not function as a uniform temperature heating element at a constant temperature in practical use. Further, a positive temperature coefficient thermistor heating element that does not differ depending on the location, that is, has a substantially uniform temperature distribution, has not been obtained. Therefore, it is an object of the present invention to provide a PTC thermistor heating element that does not vary significantly from place to place, that is, has a substantially uniform temperature distribution.

[0006]

Means for Solving the Problems The inventors of the present invention have made earnest studies on the relationship between a positive temperature coefficient thermistor element and a metal electrode on the main surface of the positive temperature coefficient thermistor element. understood. For example, as shown in FIGS. 1 and 2, the metal electrode 1 has the same rectangular shape as the main surface of the positive temperature coefficient thermistor element 2, but the shape of the metal electrode 3 is different from that of the metal electrode 1 and is rectangular. With respect to the PTC thermistor heating element having a shape obtained by removing the triangle from, the voltage was applied between the metal electrodes 1 and 3, and the surface temperature at the center line position was measured. As shown in FIG. The surface temperature is lowered at the position 4 where the metal electrode 3 is missing on the main surface, and the maximum temperature (2
It was found that the temperature was 25 ° C lower than that of (45 ° C).
At the left end position of the positive temperature coefficient thermistor element 2, since the amount of heat radiation from the side is large, the maximum temperature (24
5 ° C).

From this finding, it is found that the surface temperature can be set low at the position where the metal electrode is not formed. For example, if the metal electrode is omitted at the center position side, the center part and the side part are separated. It has been found that the temperature difference between the two is small and the entire temperature can be made uniform. The present invention has been achieved based on the above findings, and the object of the present invention is a PTC thermistor heating element in which a metal electrode is provided on the main surface of a PTC thermistor element, The metal electrode has a structure having a non-uniform distribution with respect to the main surface of the PTC thermistor element.

Also, in the PTC thermistor heating element, in which a metal electrode is provided on the main surface of the PTC thermistor element, one of the metal electrodes is disposed on the main surface of the PTC thermistor element. And the other metal electrode has a non-uniform distribution with respect to the main surface of the PTC thermistor element.

Further, in the PTC thermistor heating element in which the metal electrode is provided on the main surface of the PTC thermistor element, the distribution density of the metal electrode corresponding to the portion where the heating temperature is desired to be set lower is further lowered. This is achieved by a positive temperature coefficient thermistor heating element characterized by being constructed. In addition, a PTC thermistor heating element in which a metal electrode is provided on the main surface of the PTC thermistor element, characterized in that the distribution density of the metal electrode corresponding to a portion with a smaller heat radiation amount is configured to be lower. And a positive temperature coefficient thermistor heating element.

Further, positive temperature coefficient thermistor elements having different heat generation temperatures are used, and metal electrodes are respectively provided on the main surfaces of the plurality of positive temperature coefficient thermistor elements, and at least one of the metal electrodes has a positive temperature coefficient. This is achieved by a PTC thermistor heating element having a structure having a non-uniform distribution with respect to the main surface of the thermistor element. In the PTC thermistor heating element configured as described above, for example, the central portion of the conventional PTC thermistor heating element has a high temperature, the peripheral portion has a low temperature, and has a temperature gradient. On the other hand, the temperature difference between the peripheral portion and the central portion was small, and a substantially uniform heating element could be obtained.

Further, even in the case where the heat generation area is large and one PTC thermistor element cannot deal with it, the temperature gradient is small and a substantially homogeneous heat generating element can be obtained.

[0012]

EXAMPLE FIG. 4 is a perspective view showing an example of the PTC thermistor heating element according to the present invention, and FIG. 5 is a graph showing the surface temperature at the position of the virtual center line in FIG. In each figure, 1a is a metal electrode having the same rectangular shape as the main surface provided on the main surface (lower surface in FIG. 4) of the positive temperature coefficient thermistor element (switching temperature α) 2a, and 3a is the metal electrode 1a. Unlike the shape of
This is a metal electrode formed by removing a triangle from a rectangle, and the metal electrode 3a is provided on the main surface (upper surface in FIG. 4) of the positive temperature coefficient thermistor element 2a.

Reference numeral 2b is a PTC thermistor element (switching temperature β, α> β), and this PTC thermistor element 2b is the right end of the PTC thermistor element 2a (metal electrode 3a).
(The side where is missing) is connected. Reference numerals 1b and 3b denote metal electrodes having the same rectangular shape as the main surface provided on the main surface of the positive temperature coefficient thermistor element 2b.

In this embodiment, the same positive temperature coefficient thermistor element 2b is provided adjacent to the positive temperature coefficient thermistor element 2b. An electric current is caused to flow between the metal electrodes of the long positive temperature coefficient thermistor heating element configured as described above,
When the surface temperature was examined, it was as shown in FIG. On the other hand, when the metal electrode 3a is formed in the same rectangular shape as the metal electrode 1a, a current is passed between the metal electrodes of the long-type positive temperature coefficient thermistor heating element of the type shown in FIG. As shown in FIG. 7, and in the positive temperature coefficient thermistor heating element shown in FIG. 6, a positive temperature coefficient thermistor element (switching temperature β) 2b is used instead of the positive temperature coefficient thermistor element (switching temperature α) 2a, and When a current is passed between the metal electrodes of the positive temperature coefficient thermistor heating element of the type shown in FIG. 8 in which the metal electrodes have the same rectangular shape and the surface temperature is examined, it is as shown in FIG.

According to this, the positive temperature coefficient thermistor heating element of the type shown in FIG. 4 of the present embodiment is different from the positive temperature coefficient thermistor heating element of the type shown in FIGS.
It can be seen that the temperature difference is small and therefore a more uniform exotherm is exhibited. Further, when a large heating element is formed by using some positive temperature coefficient thermistor elements, it can be formed without a large temperature gradient at the boundary.

[0016]

[Effect] According to the present invention, there can be obtained a heating element having no large temperature change, that is, a substantially uniform temperature distribution.

[Brief description of drawings]

FIG. 1 is a plan view of a PTC thermistor heating element.

FIG. 2 is a sectional view of a PTC thermistor heating element.

FIG. 3 is a graph of the surface temperature of a PTC thermistor heating element.

FIG. 4 is a perspective view of a PTC thermistor heating element.

5 is a graph of the surface temperature of the PTC thermistor heating element of FIG.

FIG. 6 is a perspective view of a PTC thermistor heating element according to a comparative example.

7 is a graph of the surface temperature of the PTC thermistor heating element of FIG.

FIG. 8 is a perspective view of a positive temperature coefficient thermistor heating element according to a comparative example.

9 is a graph of the surface temperature of the PTC thermistor heating element of FIG.

[Explanation of symbols]

 1, 1a, 1b Metal electrode 2, 2a, 2b Positive characteristic thermistor element 3, 3a Metal electrode 3b Metal electrode

Claims (5)

[Claims] 1. A PTC thermistor heating element comprising a metal electrode provided on the main surface of the PTC thermistor element.
The PTC thermistor heating element, wherein the metal electrode has a non-uniform distribution with respect to the main surface of the PTC thermistor element. 2. A PTC thermistor heating element having a metal electrode provided on the main surface of the PTC thermistor element,
One of the metal electrodes has a uniform distribution on the main surface of the PTC thermistor element, and the other metal electrode has a non-uniform distribution on the main surface of the PTC thermistor element. A positive temperature coefficient thermistor heating element characterized by having a structure. 3. A PTC thermistor heating element comprising a metal electrode provided on the main surface of the PTC thermistor element,
A positive temperature coefficient thermistor heating element, characterized in that the distribution density of the metal electrode corresponding to a portion where the heating temperature is desired to be set lower is configured to be lower. 4. A PTC thermistor heating element comprising a PTC thermistor element provided with a metal electrode on a main surface thereof.
A PTC thermistor heating element, characterized in that the distribution density of the metal electrode corresponding to a portion having a smaller amount of heat radiation is made lower. 5. A positive temperature coefficient thermistor element having different heat generation temperatures is used, and metal electrodes are respectively provided on main surfaces of the plurality of positive temperature coefficient thermistor elements, and at least one of the metal electrodes has a positive temperature coefficient. A PTC thermistor heating element having a structure having a non-uniform distribution with respect to the main surface of the thermistor element.