JPH11150002A - Overcurrent protective element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an overcurrent interrupt element responsiveness of which is satisfactory, in which the energy loss due to the existence of the element itself can be sufficiently suppressed within a use temperature range. SOLUTION: A primary layered product 10 is formed by interposing the both faces of a sheet being a PCT mixed body A between nickel electrodes, and two notched parts 10a are formed by removing the nickel electrodes. Primary layered products 20 are formed by pressurizing nickel electrodes to one face of a sheet which is a PCT mixed body B having an operating temperature lower than that of the PCT mixed body A which is different from the PCT mixed body A, and the faces of the primary laminate 20 opposite to the faces having the nickel electrodes are allowed to cover the two notched parts 10a. Then, a secondary laminate 30 is formed by laminating the both primary laminate 10 and 20. Thus, the secondary laminate 30 is cut, and the primary laminate 20 are allowed to cover the electrode separating parts of the primary laminate 10.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is mainly applied to a circuit of an electronic device or the like. When an excessive current flows due to some abnormality in the circuit, an instantaneous protection is provided for protecting other circuit elements and batteries from being damaged. The present invention relates to an overcurrent protection element that cuts off current.

[0002]

2. Description of the Related Art Heretofore, as this kind of overcurrent protection element, a PTC element formed by sandwiching a PTC mixture of a polymer powder and a conductive filler powder between electrodes made of a conductive plate has been widely used. For example, a mixture of polyethylene, which is a polymer, and carbon black, which is a conductive filler, forms a network between carbon particles when the volume ratio of carbon black exceeds 10%. However, when the temperature rises and reaches the melting point of polyethylene, the network between the carbon particles is cut, so that the conductivity sharply decreases and the material becomes an insulator.

Utilizing such properties, a PTC element having a constant resistance value by sandwiching a mixture having both such conductive and insulating properties between terminals is used in a circuit of an electronic device or the like. When connected and used, it acts as a mere conduction path in the circuit due to low resistance for normal current values, but it is generated by itself when a large current exceeding a certain level flows due to abnormality of the circuit etc. The Joule heat causes a sharp rise in temperature, which causes the current to be cut off by reaching a temperature near the melting point of polyethylene and causing a sharp rise in resistance. The temperature at which the resistance value rises sharply is called the operating temperature. In an overcurrent protection element (PTC element), this operating temperature can be changed depending on the melting point of the polymer and the type of conductive filler used.

[0004]

In the case of the above-mentioned overcurrent protection element (PTC element), the resistance is as low as possible in a normal state for the purpose of use, and excess energy loss due to the presence of the element itself is suppressed. However, if the resistance value up to the operating temperature rises sharply at a constant temperature while the resistance value is extremely low, the time from the occurrence of overcurrent to the cutoff becomes longer, resulting in poor response. is there. For example, in a mixture of high-density polyethylene and carbon black, the change in resistivity is only about twice from 25 ° C near room temperature to 100 ° C. With such a degree of temperature dependence, the response time becomes long and cannot be ignored depending on the application.

Therefore, the resistance value of the overcurrent protection element (PTC element) in a normal state at room temperature is kept as small as possible, and the resistance value from about 80 ° C. to 4 to 1 during the temperature rise is increased.
By increasing the temperature to 0 times, the generation of Joule heat is accelerated and the cutoff time is shortened. That is, the energy loss due to the presence of the element itself is basically suppressed within the operating temperature range, and the response is improved. Performance is desired.

SUMMARY OF THE INVENTION The present invention has been made to solve such a problem, and a technical problem thereof is to provide an overcurrent having good responsiveness which can sufficiently suppress energy loss due to the presence of the element itself within a use temperature range. An object of the present invention is to provide a blocking element.

[0007]

According to the present invention, there is provided an overcurrent protection device comprising a first PTC mixture obtained by mixing a polymer powder and a conductive filler powder between electrodes made of a conductive plate. In the device, the electrodes are separated into a plurality of pieces on one surface, and a first PTC mixture obtained by mixing different kinds of polymer and conductive filler powder between the electrodes is used. Is obtained by electrically coupling different second PTC mixtures.

Further, according to the present invention, in the above-mentioned overcurrent interrupting device, the first PTC mixture comprises high-density polyethylene as a polymer powder and carbon black as a conductive filler powder. , The second P
As the TC mixture, an overcurrent interrupting element using a mixture of high-density polyethylene and ethylene ethyl acrylate as a polymer powder and using titanium carbide as a conductive filler powder can be obtained.

Further, according to the present invention, in any one of the above-mentioned overcurrent cutoff devices, the operating temperature of the first PTC mixture is higher than the operation temperature of the second PTC mixture. Can be

[0010]

Generally, the room temperature resistance of the overcurrent cutoff element is
If the thickness of the element itself is constant, it is proportional to the electrode area. Therefore, in the overcurrent interruption element of the present invention, the operating temperature range of the electronic device to be applied is assumed, and for example, the effective electrode area is suppressed to as low as possible the entire surface of the element up to 80 ° C, while exceeding 80 ° C. In this case, the resistance is increased several times above that temperature by separating a part of the electrode to reduce the effective electrode area by a factor of several, thus realizing performance that can accelerate response. Is being measured. As an electrode separation structure for this, an electrode on one surface is divided in advance, and a space between the divided electrodes is, for example, a PTC composite material (PTC mixture) having an operating temperature of 80 ° C.
It becomes possible by combining with. That is, when the temperature reaches 80 ° C., the portion electrically connecting the main electrode (the electrode connected to the electrode terminal) and the sub-electrode becomes almost an insulator, and the two are electrically separated from each other. The resistance decreases and the resistance increases. Therefore, after the excess current is separated, it flows only to a specific part and accelerates the generation of Joule heat,
The time required to reach, for example, 120 ° C. as the operating temperature can be greatly reduced.

[0011]

Embodiments of the present invention will be described below in detail with reference to the accompanying drawings.

First, the outline of the basic configuration of the overcurrent cutoff device of the present invention will be briefly described. This overcurrent cutoff element has a common point with a conventional one in that it has a portion formed by sandwiching a first PTC mixture obtained by mixing a polymer powder and a conductive filler powder between electrodes made of a conductive plate. However, the electrode is separated into a plurality on one surface, and between the electrodes is a first PTC mixture obtained by mixing different types of polymer and conductive filler powder respectively. Comprises a different second PTC mixture electrically coupled.

Examples of the first PTC mixture include a case where high-density polyethylene is used as the polymer powder and carbon black is used as the conductive filler powder.
Examples of the PTC mixture include a mixture of a polymer powder and high-density polyethylene and ethylene ethyl acrylate, and a case where titanium carbide is used as a conductive filler powder. Here, the operating temperature of the first PTC mixture is higher than the operating temperature of the second PTC mixture.

Hereinafter, a method of manufacturing such an overcurrent cutoff device and a method of manufacturing the same will be specifically described. First, a different PCT mixture A (first PTC mixture), PC, which is used in this overcurrent blocking element and is made by mixing different types of polymer and conductive filler powder.
Table 1 shows the component constitution of the T mixture B (second PTC mixture).

[0015]

[Table 1]

FIG. 1 shows the results of measuring the temperature change of the resistivity with each of these PCT mixtures A and B sandwiched between nickel electrodes made of nickel foil. From FIG. 1, the operating temperature of the PCT mixture A represented by the resistivity A is 1
20 ° C. to 125 ° C., indicating that the operating temperature of the PCT mixture B represented by the resistivity B is about 85 ° C.

Therefore, as a procedure for fabricating an overcurrent interrupting device using these PCT mixtures A and B, first, a polymer and a conductive filler were added in a proportion of 150 as shown in Table 1.
The mixture was mixed using a hot roll at a temperature of at least ℃ to disperse the conductive filler.

Next, each of the PCT mixtures A and B is rolled again by a heating roll, and has a thickness of 500 μm and a width of 50 m.
m sheet.

Further, with respect to the sheet made of the PCT mixture A, both sides thereof are sandwiched between two nickel electrodes made of nickel foil having a thickness of 50 μm and hot-pressed at a temperature of 150 ° C. or more, and the end faces are cut. As a result, a primary laminate 10 having a width W of 30 mm, a length L of 50 mm, and a thickness D of 300 μm was obtained as shown in a plan view of FIG. 2A and a side view of FIG. . However, in the primary laminated body 10, the distance d was set to 20 mm at a position 5 mm from both ends in the width W direction with a dicing saw with respect to the nickel electrode on one side, and the width 1 mm was parallel to the length L direction at two places. After the cut portion 10a was formed, the nickel electrode in the cut portion 10a was peeled off.

On the other hand, with respect to the sheet made of the PCT mixture B, a nickel electrode made of a single nickel foil having a thickness of 50 μm is pressed on only one side of the sheet and hot-pressed at a temperature of 150 ° C. or more, and the end face is cut. By doing so, another primary laminate 20 having a width W of 5 mm, a length L of 50 mm, and a thickness D of 200 μm is shown in a plan view of FIG. 3A and a side view of FIG. I got

Thereafter, regarding the primary laminates 10 and 20,
The primary laminate 20 was placed on the two cut portions 10a of the primary laminate 10 from which the nickel electrodes had been removed, and the surfaces opposite to the surface having the nickel electrodes were respectively covered, and both were laminated again by hot pressing at 150 ° C. or higher. 4 (a) shows a plan view, FIG. 4 (b) shows a side view, and FIG. 4 (c) shows a partial perspective view of the secondary laminate 30 having a maximum thickness D of 450 μm. Was.

Finally, regarding the secondary laminate 30, FIG.
PTC element samples 11 and 12 were obtained by cutting into shapes as shown in the plan views of (a) and (b). As shown in FIG. 5A, the PTC element sample 11 has a structure according to one embodiment of the present invention in which the primary separation body 20 is covered on the electrode separation part of the primary stack 10. ,
As shown in FIG. 5B, for comparison, the outer dimensions of the PTC element sample 11 were the same, and the structure according to the comparative example was cut from the primary laminate 10.

In short, in the above-described overcurrent interrupting element (PTC element sample 11) of the present invention, the nickel electrode of the primary laminate 10 formed by laminating the both surfaces of the sheet made of the PCT mixture A between the nickel electrodes was removed. The two cut portions 10a are different from the PCT mixture A, respectively.
PCT having lower operating temperature than PCT mixture A
A primary laminate 20 formed by pressing a nickel electrode against one surface of the sheet of the mixture B is covered with a surface opposite to the surface having the nickel electrode, and a secondary laminate 30 formed by laminating both is cut; It is obtained as a structure in which the primary laminate 20 is covered on the electrode separation portion of the primary laminate 10.

In the case of the PTC element sample 11, the primary laminate 1
The local part on the front side at 0 is the electrode terminal T1, and the local part on the back side is the electrode terminal T2. Similarly, PTC element sample 1
Also in the case of No. 2, an arbitrary portion on the front side of the primary laminate 10 becomes the electrode terminal T1, and an arbitrary portion on the back side becomes the electrode terminal T2.

Therefore, these PTC element samples 11, 1
2 was measured for the electrical resistance between the electrode terminals T1 and T2, and the results as shown in Table 2 (in Table 2, PT
C element sample 11 is α, and PTC element sample 12 is β).

[0026]

[Table 2]

From Table 2, it can be seen that the electrical resistance of each of the PTC element samples 11 and 12 is approximately 20 mmΩ.

Next, these PTC element samples 11, 12
With respect to, when the temperature change of the electric resistance between the electrode terminals T1 and T2 was measured using a thermostat and a four-terminal resistance meter,
The results shown in FIG. 6 were obtained (in FIG. 6, the PTC element sample 11 was α and the PTC element sample 12 was β).

FIG. 6 shows that when the PTC element samples 11 and 12 are compared, the temperature change of the electric resistance of 80 ° C. or more is different. It can be seen that the resistance value is doubled.

Further, the current interruption time of the PTC element samples 11 and 12 was compared using an overcurrent interruption test circuit as shown in FIG. Incidentally, this overcurrent cutoff test circuit is, for example, a 30 V DC power supply 13, a switch SW, 5Ω
, A PTC element sample 11 or PTC element sample 12, and an ammeter 14 are connected in series as a closed circuit, and an oscilloscope 15 is connected in parallel to the protection resistance R.

FIG. 8 shows the measurement results of comparing the current interruption time with the current (A) with respect to time (sec) in this overcurrent interruption test circuit. Sample 12 is denoted by β). From FIG. 8, regarding the current interruption time,
It can be seen that the time for the PTC element sample 12 is 4 seconds, whereas the time for the PTC element sample 11 is 2.5 seconds, which is almost half.

[0032]

As described above, according to the overcurrent cutoff device of the present invention, the energy loss (resistance value) due to the presence of the device itself can be sufficiently suppressed within the operating temperature range, and the response is good. Therefore, the current interruption time is short and the performance is excellent.

[Brief description of the drawings]

FIG. 1 shows the results of measuring the temperature change of resistivity with a different PCT mixture used for an overcurrent cutoff device according to one embodiment of the present invention interposed between nickel electrodes.

FIGS. 2A and 2B show a primary laminated body produced by using one of different PCT mixtures to produce the overcurrent cutoff device described with reference to FIG. 1, wherein FIG. (B) relates to the side view.

FIGS. 3A and 3B show another primary laminated body produced by using the other of the different PCT mixtures to produce the overcurrent cutoff device described with reference to FIG. 1, wherein FIG. (B) relates to the side view.

4A and 4B show a secondary laminate formed by laminating the primary laminates shown in FIGS. 2 and 3, wherein FIG. 4A is related to a plan view, FIG. 4B is related to a side view thereof, (C) relates to a partial perspective view thereof.

5 is a PTC obtained by cutting the secondary laminate shown in FIG.
5A and 5B show element samples, in which FIG. 6A is a plan view of a structure according to an example, and FIG. 6B is a plan view of a structure according to a comparative example.

FIG. 6 shows a result of measuring a temperature change of an electric resistance between electrode terminals of a PTC element sample.

FIG. 7 shows a simplified configuration of an overcurrent cutoff test circuit applied to a PTC element sample.

8 is a diagram showing a PTC in the overcurrent cutoff test circuit shown in FIG. 7;
5 shows a measurement result of a current interruption time of an element sample.

[Explanation of symbols]

 10, 20 Primary laminate 10a Cut portion 11, 12 PTC element sample 13 DC power supply 14 Ammeter 15 Oscilloscope 30 Secondary laminate A, B PCT mixture R Protection resistor SW switch T1, T2 Electrode terminal

Claims (3)

[Claims] 1. An overcurrent protection element comprising a first PTC mixture obtained by mixing a polymer powder and a conductive filler powder sandwiched between electrodes made of a conductive plate, wherein the plurality of electrodes are provided on one surface. The first P is obtained by mixing different kinds of the polymer and the conductive filler powder between the electrodes.
An overcurrent protection element, wherein a second PTC mixture different from the TC mixture is electrically coupled. 2. The overcurrent protection device according to claim 1, wherein the first PTC mixture uses high-density polyethylene as the polymer powder and uses carbon black as the conductive filler powder. In the second PTC mixture, a mixture of the high-density polyethylene and ethylene ethyl acrylate is used as the polymer powder, and titanium carbide is used as the conductive filler powder. Overcurrent protection element. 3. The overcurrent protection device according to claim 1, wherein an operating temperature of the first PTC mixture is higher than an operating temperature of the second PTC mixture. Protection element.