JPH0669002A - Positive temperature coefficient characteristic thermistor - Google Patents

Abstract

PURPOSE:To avoid the cracking of the positive temperature coefficient characteristic thermistor and the short-circuit of electrodes by suppressing any abnormal heat. CONSTITUTION:The electrodes 2 in contact with feeder terminals 3 are divided into two parts so that the whole current amount fed to the positive temperature coefficient characteristic thermistor element 1 may be dispersed in the divided numbers of the electrodes 2 to avoid the local current concentration in the same electrodes 2 while suppressing the abnormal heat.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a positive temperature coefficient thermistor used as a heater and a resistor for vehicles.

[0002]

2. Description of the Related Art FIG. 5 is a block diagram of a conventional positive temperature coefficient thermistor. In the positive temperature coefficient thermistor, electrodes 2 are provided on both sides of the positive temperature coefficient thermistor element 1 shown in FIG. 5A, and the power supply terminal 3 shown in FIG. 5B is fixed on the electrode 2 by pressing or insulating adhesive. In the contact state, the surface of the PTC thermistor element 1 and the power supply terminal 3 are electrically connected.

The contact structure between the power supply terminal 3 and the electrode 2 of the above-mentioned positive temperature coefficient thermistor shown in FIG. 5 (c) is microscopically a projection 2a on the electrode 2 side or a projection 3a on the power supply terminal 3 side. Are in contact with each other. Here, when the contact portion between the power supply terminal 3 and the electrode 2 is extremely reduced, abnormal heat generation occurs. For example, in the case where only one point contact is made, if I is the current flowing through the positive temperature coefficient thermistor element 1 and R is the contact resistance of the contact portion, the heat generation amount Q per unit time is given by the following equation.

[0004]

[Equation 1] Q = I ² R

The current is concentrated in the point contact portion to cause abnormal heat generation, which causes problems such as cracking of the PTC thermistor element 1 and short circuit due to breakdown of the PTC thermistor element 1 withstand voltage.

Accordingly, the plate thickness of the PTC thermistor element 1 has been increased, the flatness of the contact surface has been improved, and the pressing load has been increased. It wasn't a good measure.

[0007]

SUMMARY OF THE INVENTION In order to solve the above problems, it is an object of the present invention to reduce the current concentration to a level at which the PTC thermistor element is not cracked or short-circuited with a simple structure.

[0008]

In order to solve the above problems, the present invention provides a positive temperature coefficient thermistor in which electrodes are provided on both sides of a plate-shaped positive temperature coefficient thermistor element and a power supply terminal for supplying power to the electrodes is provided. Provided is a positive temperature coefficient thermistor which is characterized by dividing an electrode into a plurality of power supply terminals facing the electrode or having the same or the same potential and reducing current concentration at a contact point between the electrode and the positive temperature coefficient thermistor.

[0009]

According to the present invention, as shown in FIG. 1, when the electrode 2 is applied to the positive temperature coefficient thermistor element 1 from the power supply terminal 3 by dividing it into two parts on both sides, the contact becomes a contact state with only one point and the amount of heat generation. Q is shown by the following equation.

[0010]

## EQU2 ## Q = (I / 2) ² R = 1 / 4I ² R

Then, the calorific value Q becomes 1/4 of the conventional value. Further, as shown in FIG. 2, when the electrode 2 is divided into four, the heat generation amount is 1/16. By dividing the electrode 2 as described above, it is possible to reduce the current concentration at the contact point, easily reduce the abnormal heat generation amount, and prevent the PTC thermistor element 1 from cracking or the electrode 2 from being short-circuited.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described with reference to the accompanying drawings FIGS. FIG. 1 is a configuration diagram of a positive temperature coefficient thermistor according to the embodiment. Electrodes 2 are provided on both surfaces of a flat plate type positive temperature coefficient thermistor element 1 shown in FIG. The positive temperature coefficient thermistor element 1 is a ceramic-based sintered body obtained by mixing and sintering oxide-based powder or the like as a raw material. Electrode 2
Is made of a material such as Al, Ag, and Cu, and is formed on the surface of the positive temperature coefficient thermistor element 1 by a method such as paste printing or thermal spraying. As shown in FIG. 1B, in order to feed power to the PTC thermistor element 1, the feed terminal 3 is made of a conductive material such as Cu or Al. Here, the positive temperature coefficient thermistor element 1
The power supply terminal 3 is fixed by pressing the spring 4 shown in FIG. 3 or the insulating adhesive 7 as shown in FIG.

Next, the operation of the embodiment of the present invention shown in FIG. 1 will be described. When a power source is applied between the power feeding terminals 3 that face each other with the positive temperature coefficient thermistor element 1 in between, a current is generated.
To the electrode 2 through the convex portion 2a or the convex portion 3a shown in FIG. 1C, the positive characteristic thermistor element 1 and the opposite side power supply terminal 3.

At the contact portions of the convex portions 2a and 3a, local heat generation tends to occur due to the flowing current value and the number of contact portions. In this embodiment, however, the convex portions 2a and the convex portions 3a are formed.
In order to reduce the amount of current flowing through the electrode 2, the electrode 2 in contact with the power supply terminal 3 is divided and the total amount of current supplied to the positive temperature coefficient thermistor element 1 is distributed to the number of divisions of the electrode 2. The local concentration of current by the electrode 2 is prevented, abnormal heat generation of the electrode 2 and the power supply terminal 3 is suppressed, and element cracking, short circuit, etc. are prevented.

Next, other application examples will be described. FIG. 3 is a configuration diagram showing a second embodiment of the present invention.
In FIG. 3 (a), the electrodes 2 are provided on both surfaces of a circular plate-shaped positive temperature coefficient thermistor element 1 in four divisions. The electrode 2 is formed by paste printing of Ag, Al, or the like. The cover 5 shown in FIG. 3B is made of a metal material and serves as a heat dissipation member and an electrode member, and the positive temperature coefficient thermistor element 1 is fixed by pressing with a spring 4 via a power supply terminal 3. The contact portion between the positive temperature coefficient thermistor element 1 and the cover 5 shown in FIG. 3C is a microscopic convex portion 2 a of the electrode 2.
Becomes

Next, further application examples will be described. FIG. 4 is a configuration diagram showing a third embodiment of the present invention.
In FIG. 4 (a), the electrodes 2 are provided on both surfaces of the positive temperature coefficient thermistor element 1 in four divisions. As shown in FIGS. 4 (b) and 4 (c), the electrode 2 has an uneven surface formed by thermal spraying or adding metal particles to the paste, and the power supply terminal 3 and the fin 6 are brazed or soldered. Is fixed by an insulating adhesive 7 so that the power supply terminal 3 is in contact with the convex portion 2a of the electrode 2 of the positive temperature coefficient thermistor element 1. Here, the electrode 2 of the positive temperature coefficient thermistor element 1 and the power supply terminal 3 are in contact with each other by the convex portion 2 a of the electrode 2. The protrusions 2a may be formed by a method such as thermal spraying of the electrode 2 or addition of metal powder to the paste, but microscopic protrusions formed by Ag or Al paste or undulations or cut-and-raised parts of the power supply terminal 3 In some cases, etc.

[0017]

As described above, according to the present invention, since the current is suppressed by dividing the electrodes and distributing the current supplied from the power supply terminal, abnormal heat generation can be easily reduced and the positive temperature coefficient thermistor element can be cracked. There is an excellent effect that it is possible to prevent a short circuit of the electrodes.

[Brief description of drawings]

FIG. 1 is a configuration diagram showing an embodiment of the present invention.

FIG. 2 is a perspective view showing an embodiment in which the positive temperature coefficient thermistor of the present invention is divided into four parts.

FIG. 3 is a configuration diagram showing a second embodiment of the present invention.

FIG. 4 is a configuration diagram showing a third embodiment of the present invention.

FIG. 5 is a configuration diagram showing a conventional technique.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Positive characteristic thermistor element, 2 ... Electrode, 2a ... Convex part, 3 ... Feeding terminal, 3a ... Convex part.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Yasuhiro Oya 1-1-1, Showa-cho, Kariya city, Aichi prefecture Nihon Denso Co., Ltd.

Claims (1)

[Claims] 1. A positive temperature coefficient thermistor in which electrodes are provided on both sides of a plate-shaped positive temperature coefficient thermistor element and a power supply terminal for supplying electric power to the electrodes is provided. A positive temperature coefficient thermistor which is characterized in that the current concentration at a contact point between the electrode and the positive temperature coefficient thermistor is reduced.