JPH0992507A - Positive temperature characteristic thermistor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To eliminate a quick trip phenomenon at a high temperature and high voltage by reducing the variation of the trip time caused by the environmental temperature. SOLUTION: The first PTC element 5-1 and the second PTC element 5-2 are provided on a PTC element, and the PTC elements 5-1 and 5-2 are arranged between electrodes 5a and 5b in a non-contact state with each other. As a result, the PTC elements 5-1 and 5-2 are operated without directly subjected to the influence of thermal conductivity, the change in temperature characteristics becomes small, the variation in trip time caused by the environmental temperature becomes small, and the generation of a quick trip effect phenomenon at high temperatures and high voltages can be prevented.

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 (PT) mainly used as an overcurrent / overheat protection element.
C (Positive Temperature Coefficient) thermistor)
It is about.

[0002]

2. Description of the Related Art Current PTC thermistors are roughly classified into ceramic type and polymer type. Basically, any PTC thermistor has an integral structure in which only one PTC element (PTC element) whose resistance value increases with temperature rise is arranged between electrodes. FIG. 4 shows a circuit example using a PTC thermistor. In the figure, 1 is a battery, 2 is a motor, and 3 is a PTC thermistor. In this example, a PTC thermistor 3 is inserted in series with the motor 2 for overcurrent protection, and when an overcurrent flows through the motor 2,
The PTC thermistor 3 generates heat, its resistance value becomes large, and the current to the motor 2 decreases. FIG. 5 shows an outline of the internal configuration of the PTC thermistor 3. The PTC thermistor 3 has an integral structure in which only one PTC element 3-1 is arranged between the electrodes 3a and 3b.

[0003]

However, according to the conventional PTC thermistor, the resin polymer system, which is particularly inexpensive in price, has a large variation in the volume specific resistance value inside the PTC element and a large change in the temperature characteristic. The time (trip time) required for protection against overheating and overheating varied greatly depending on the ambient temperature. That is, the PTC shown in FIG.
Explaining with the thermistor 3, the PTC element 3-1 is the electrode 3
Since it is arranged as an integral structure between a and 3b, once it enters a heat generating state, it rapidly generates heat from a partial block (local block) with a high volume specific resistance value in the PTC element 3-1. Heat is affected to the block of, and the heat generation and resistance value increase at once, and it becomes a trip state (equilibrium state with high resistance). The main reason for this is a large change in temperature characteristics,
The trip time varies greatly depending on the environmental temperature.

FIG. 6 shows the temperature (T) -resistance value (R) characteristic (characteristic I of the solid line in the figure) and the temperature (T) -trip time (Tp) characteristic (characteristic II of the broken line in the figure) of the PTC thermistor 3. As can be seen from this characteristic, in the conventional PTC thermistor 3, the trip time Tp greatly varies depending on the environmental temperature T, and the trip time Tp sharply shortens as the environmental temperature T rises. This means that the trip early effect phenomenon occurs at high temperature and high voltage.

The present invention has been made in order to solve such a problem, and its object is to reduce the variation in trip time with respect to the environmental temperature and eliminate the phenomenon of early trip effect at high temperature and high voltage. It is to provide a positive temperature coefficient thermistor capable of doing so.

[0006]

In order to achieve such an object, the first invention (the invention according to claim 1) is a positive characteristic element, wherein the first to nth positive characteristic elements (5-1, 5-2)
Are provided, and the first to n-th positive characteristic elements are arranged between the electrodes (5a, 5b) in a non-contact state with each other. According to the present invention, the first to n-th positive characteristic elements are arranged between the electrodes in a non-contact state with each other.
~ The n-th positive temperature coefficient device operates without being directly affected by the conduction of heat. A second invention (the invention according to claim 2) is the same as the first invention, except that at least two volume specific resistance values of the first to n-th positive characteristic elements are different. A third invention (an invention according to claim 3) is the first invention, wherein one positive characteristic element (5-1) is arranged on the outer peripheral portion between the electrodes so as to surround another positive characteristic element (5-2). It was done.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in detail based on embodiments. FIG. 1 (a) is a side sectional view showing the outline of the internal configuration of a PTC thermistor showing an embodiment of the present invention, and FIG. 1 (b) is a plan view showing the arrangement of PTC elements between electrodes. In the present embodiment, a first PTC element 5-1 and a second PTC element 5-2 are provided as PTC elements, and the PTC elements 5-1 and 5-2 are placed between the electrodes 5a and 5b in a non-contact state with each other. I'm trying to place it. That is, the PTC element 5-2 is connected to the electrodes 5a and 5b.
A ring-shaped PTC element 5-1 is arranged inwardly between the electrodes 5a and 5b so as to surround the PTC element 5-2. FIG. 2 shows an example of a circuit using this PTC thermistor 5.

In this embodiment, since the PTC elements 5-1 and 5-2 are arranged between the electrodes 5a and 5b in a non-contact state, the PTC elements 5-1 and 5-2 conduct heat to each other. Operates without being directly affected by. As a result, changes in temperature characteristics are reduced, and variations in trip time with respect to environmental temperature are reduced. This means that the trip pre-action phenomenon does not occur at high temperature and high voltage.

That is, the resistance value R of the conventional PTC thermistor 3 and the resistance value R of the PTC thermistor 5 of the present embodiment.
When (R = (R1 + R2) / (R1 · R2)) is the same (R1: resistance value of PTC element 5-1, R2: PT
The resistance value of the C element 5-2), PT in the PTC thermistor 5
Since the C elements 5-1 and 5-2 operate without being directly affected by heat conduction, the trip time becomes long. This is true even at high temperature and high voltage,
As the trip time becomes longer, the trip early effect phenomenon does not occur.

In this embodiment, the PTC element 5-
2 is arranged inside the electrodes 5a and 5b, and the PTC element 5-
A PTC element 5-1 is arranged on the outer peripheral portion between the electrodes 5a and 5b so as to surround the electrode 2. Thereby, the PTC element 5-1
Since the outer periphery of the PTC is exposed to air, it becomes easier to cool and the PTC
Since the element 5-2 does not come into contact with air, heat is easily accumulated, and by combining this, characteristics different from those of the conventional PTC thermistor 3 can be created. That is, it becomes possible to change and adjust the trip time within the operating temperature range, and it is possible to keep up with the required trip time. To change or adjust the trip time within the operating temperature range,
It is also possible to make the volume specific resistance values of the PTC element 5-1 and the PTC element 5-2 different.

Further, in the present embodiment, the PTC element 5-
Although 1 has an annular shape, as shown in FIG. 1 (c), it may have a square band shape, and various shapes are possible. Further, in the present embodiment, the PTC element 5-2 is arranged inside the electrodes 5a and 5b, and the PTC element 5-2 is surrounded by the PTC element 5-2.
The element 5-1 is arranged on the outer peripheral portion between the electrodes 5a and 5b,
As shown in FIG. 3, PTC elements 5-3, 5-4, 5-5
May be juxtaposed between the electrodes 5a and 5b in a non-contact state.

[0012]

As is apparent from the above description, according to the present invention, in the first invention, the positive characteristic elements are
Since the n-th positive characteristic element is provided and these first to n-th positive characteristic elements are arranged between the electrodes in a non-contact state, the first to n-th positive characteristic elements are caused by heat conduction to each other. It operates without being directly affected, changes in temperature characteristics are small, variations in trip time with respect to ambient temperature are small, and it is possible to eliminate the premature trip phenomenon at high temperatures and high voltages. Further, in the second invention, at least two volume specific resistance values of the first to n-th positive characteristic elements are made different, and in the third invention, another positive characteristic element is provided in the outer peripheral portion between the electrodes. Since one positive temperature coefficient element is placed so as to surround it, changing the trip time within the operating temperature range
Adjustments are possible, and it is possible to keep up with the required trip time.

[Brief description of drawings]

FIG. 1 is a diagram showing a schematic internal configuration of a PTC thermistor (ring type) showing an embodiment of the present invention.

FIG. 2 is a diagram showing a circuit example using this PTC thermistor.

FIG. 3 is a diagram showing an outline of an internal configuration of a PTC thermistor (chip type) showing another embodiment of the present invention.

FIG. 4 is a diagram showing a circuit example using a conventional PTC thermistor.

FIG. 5 is a diagram showing an outline of an internal configuration of a conventional PTC thermistor.

FIG. 6 is a diagram showing temperature-resistance value characteristics and temperature-trip time characteristics of a conventional PTC thermistor.

[Explanation of symbols]

1 ... Battery, 2 ... Motor, 5 ... PTC thermistor, 5
a, 5b ... Electrode, 5-1 ... First PTC element, 5-2 ...
Second PTC element.

Claims (3)

[Claims] 1. A positive characteristic thermistor in which a positive characteristic element whose resistance value increases with temperature rise is arranged between electrodes, wherein the positive characteristic element includes first to nth positive characteristic elements,
A positive temperature coefficient thermistor, wherein the first to nth positive temperature coefficient elements are arranged between the electrodes in a non-contact state with each other. 2. The positive temperature coefficient thermistor according to claim 1, wherein at least two volume specific resistance values of the first to nth positive temperature coefficient elements are different. 3. The positive temperature coefficient thermistor according to claim 1, wherein one positive temperature coefficient element is arranged on the outer peripheral portion between the electrodes so as to surround another positive temperature coefficient element.