JPS62285332A - Self-return type overcurrent protection element - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

Detailed Description of the Invention 3. Detailed Description of the Invention (Field of Industrial Application) The present invention is a self-resetting overcurrent protection element (hereinafter referred to as overcurrent protection element in obvious cases) whose performance is improved using an organic conductive material. (abbreviated as current protection element or element)).

(Prior Art) Fuses, circuit breakers, and the like are widely used as protection devices against overcurrent. However, fuses need to be relined before they can be used again after they have blown out, while circuit breakers are relatively easy to reset after operation, but are difficult to miniaturize and are not suitable for use when installed on temporary print distribution panels, etc. It's inappropriate. Therefore, as a substitute for these, resistors that utilize the characteristic that the resistance value increases significantly as the temperature rises, such as positive temperature coefficient thermistors, have come to be used as self-resettable protective elements.

By the way, conventional positive temperature coefficient thermistors include those whose main component is barium titanate-based ceramic semiconductors and plastic thermistors that use organic semiconductors, but the former have poor moldability and flexibility, and the latter have poor moldability and flexibility, and the latter As the value increases, the conductivity increases over a wide range and the overcurrent limiting effect is lost.Therefore, there has been no satisfactory self-resetting overcurrent protection element.

Recently, a positive characteristic thermistor that does not have these drawbacks has been developed by graft polymerizing vinyl monomers such as acrylic acid and methacrylic acid ester to carbon plastic, and then adding a crosslinking agent such as epoxy resin and curing with heat. It is being done.

(Problems to be Solved by the Invention) The above-mentioned thermistor obtained through graft polymerization has positive characteristics, good moldability, and is stable against thermal history due to thermal cycles, etc., so it is a self-returning type. It can be used as an overcurrent protection element.

However, this type of thermistor has a relatively high resistance value as an element due to the high grafting rate and large resin content in order to obtain a large resistance temperature coefficient, and the operating voltage or rated voltage is several hundred
In case (2), the operating current, that is, the rated current, can only be obtained at a maximum of several mA or less.

On the other hand, overcurrent protection elements are mostly used in small, low-voltage circuits such as printed wiring circuits, and a device suitable for these uses has not yet been obtained.

(Means for Solving the Problems) The present inventors have conducted extensive research to solve the above problems and obtain a self-resetting overcurrent protection element that has a large resistance temperature coefficient and a small resistance value. The inventors have discovered that these objectives can be achieved by using carbon black whose particle surfaces are partially plated with metal, and have completed the present invention. That is, the present invention uses a cured product obtained by graft polymerizing a vinyl monomer onto a carbon blank whose surface is partially plated with metal, adding an epoxy resin as a crosslinking agent, and heating it. It is a feature.

The carbon blanks used in the present invention include channel black and furnace black.

Examples include acetylene blank. Metal plating is applied partially to the surface of the carbon blank. Electroless plating, so-called chemical plating, is usually used for metal plating. There are no particular restrictions on the metal to be plated, but nickel, copper, copper, SPA, gold, etc. are practically used.

If the entire surface of the carbon blank particles is covered with metal, the vinyl monomer cannot be graft-polymerized and a thermistor with a positive temperature coefficient of resistance cannot be obtained. Therefore, in the present invention, only the exposed surface of the carbon black particles is Apply partial plating with metal so that some parts remain. For this reason, the amount of metal deposited is usually 0.1 to IO1, and a preferable value is 0.5 to 6, based on the weight ratio of carbon blank.

Now, on the particle surface of a carbon blank that has been partially plated with metal, there are parts to which metal has adhered and parts to which it has not, but there are also pinholes and cracks in the parts to which metal has adhered, and the surface of carbon black is directly coated with metal. Since some parts are exposed, the vinyl monomer causes a graft reaction with the parts not covered by these metals. Note that carbon black partially plated with metal and carbon black not plated with metal may be partially mixed and used in the same manner as above. However, a thermistor having a positive temperature coefficient of resistance cannot be obtained by simply mixing these metal powders into a carbon blank instead of using a metal-plated carbon blank.

As mentioned above, in the present invention, a vinyl monomer is graft-polymerized onto metal-plated carbon black. However, the vinyl monomer has the general formula % (where R is hydrogen or a methyl group, and R is hydrogen Or an alkyl group having 1 to 10 carbon atoms, or a glycidyl group.

NN'-dialkylamino substituted hydrocarbon group), such as acrylic acid, methacrylic acid or esters of these acids, acryl or methacrylamide, and acrylonitrile.

These include methacrylonitrile, vinyl acetate, styrene and its derivatives, and maleic anhydride.

Among these, a combination of acrylic acid and methacrylic acid ester is particularly suitable.

Further, as the polymerization initiator, α,α゛-azobisisobutyronitrile, α,α′-azobispropionitrile, other azo and diazo compounds, peroxides, etc. are used.

As the polymerization method, a solution polymerization method is usually used, but methods such as bulk polymerization and suspension polymerization can also be used.

In this manner, the vinyl monomer reacts with the non-metal-plated portions of the carbon black surface, producing a carbon black graft polymer. A compound having an epoxy ring as a crosslinking agent in these carbon black graft polymers.

Usually, after applying an epoxy resin to a substrate made of alumina or the like (heating and curing at 150 to 200°C), a self-resetting overcurrent protection element with a positive temperature coefficient of resistance and low resistance value is obtained. be able to.

FIG. 1 shows an example of the structure of a self-resetting overcurrent protection element according to the present invention, in which (a) is a plan view and (bl is a cross-sectional view). Ag, pdii pole 2a on both sides of the top surface.

2b is attached, and the carbon black graft polymer 3 is applied to the part sandwiched between the two electrodes 2a and 2b on the upper surface of the alumina substrate 1, overlapping part of the electrodes 2a and 2b, and heated and hardened to make them adhere. A device made by is shown. When a voltage is applied between the electrodes 2a and 2b, a current flows, but when the value of the current becomes abnormally large, the resistance of the element increases rapidly due to temperature rise, and the current is cut off. However, as the voltage returns to a steady state and the temperature of the element decreases, the element resistance also decreases and the current automatically returns.

(Embodiment of the Invention) Three types were partially plated with nickel by depositing nickel on a carbon blank (furnace black) at a weight ratio of 1, 2, and 5 parts, respectively, using a chemical plating method. A carbon blank was prepared. Using α, α°-azobisisobutyronitrile as catalysts and dimethylformamide and methyl isobutyl ketone as carriers, acrylic acid and octyl methacrylate were prepared by solution polymerization in the proportions shown in the table below. were reacted at 95° C. for 8 hours to produce carbon blank graft polymers with different nickel contents.

Next, 20 g of epoxy resin (trade name Epicote 828) was mixed with each of the metal-plated carbon black graft polymers obtained in this way as a crosslinking agent, and the distance between the electrodes was 0.5 mm and the width was 8 fl as in Fig. 1. After coating on the alumina substrate surface of
Three types of self-resetting overcurrent protection elements having different nickel contents were obtained by heat curing at 0°C for 2 hours and then at 180°C for 1 hour.

For comparison, instead of using a partially nickel-plated carbon blank as in the present invention, a normal unplated carbon blank was used and a self-resetting overcurrent protection element was fabricated in exactly the same manner as in the previous embodiment. The results were as follows.

Figures 2 and 3 are comparative diagrams of resistance temperature characteristics.
First of all, Figure 2 is a characteristic comparison diagram with and without Ni plating.
1 is the case without Ni plating, and 2 is the case where Ni plating was performed at a ratio of Ni: CB (carbon black) = 1:1. As is clear from this figure, the characteristics (1) and (2) show almost similar change characteristics, but the resistance value of the element according to the present invention is much smaller. Next, Figure 2 is a characteristic comparison diagram when the amount of Ni plating is changed for the example element.The ratio of Ni to CB is 1:1° for curve ■, 2:11 for curve ■, and 5:1 for curve ■. . As is clear from this figure, as the amount of Ni plated on the carbon blank increases, the resistance value decreases. Therefore, it can be seen that an element having an arbitrary resistance value can be obtained by adjusting the amount of Ni plating.

FIG. 4 is a diagram showing an example of a circuit for determining the voltage-current characteristics of an overcurrent protection element, where ``■'' is a variable voltage source, 4 is an element to be tested, and its terminal voltage is ``7'', and R is a resistor. Also the fifth
This figure and FIG. 6 show the voltage-current characteristics of the element 4 obtained by this circuit. First, Figure 5 shows a comparison of characteristics with and without Ni plating, where the characteristic (■) in the figure is for an element without Ni plating, and the characteristic (■) is for an element with Ni plating at a Ni:CB=1:1 ratio. It is. From Figure 5, Ni
It can be seen that the element of the present invention using a plated carbon blank has a larger peak current Ep and a lower peak voltage V than the conventional element. Figure 6 shows the voltage-current characteristics of element 4 when the amount of Ni plating is changed, and the curve ■ in the figure is Ni:CB.
The 1:11 curve (■) and the 2:11 curve (■) indicate the 5:1 cases, and as the amount of nickel plating on the carbon blank increases, I tends to increase and (■) tends to decrease.

Now, in FIG. 5, when the current (2) flowing through the element is equal to or less than the peak current value I, the overcurrent protection element is in a steady state and is in the flat part of the curve (2) in FIG. 2, that is, in a low resistance state. If we consider the case where ■ in Figure 4 becomes large, or the load resistance R becomes small and the current I becomes 11 or more and ■A>V, then the transition occurs to the rapidly increasing part of the curve ■ in Figure 2. Therefore, the element current I exhibits a time vs. current I characteristic as shown in FIG.

Figure 7 shows the current-limiting characteristics of overcurrent protection elements with and without Ni plating. The curve ■ in the figure is for the element without Ni plating, and the curve ■ is for the element with Ni plating at Ni:CB = 1: 1.
Each corresponds to the element made at the weight ratio of . In other words, this characteristic becomes the current-limiting characteristic of the overcurrent protection element, and its peak current value! , has the same contents as the rated current of a fuse or breaker, but from this characteristic, the same voltage ■, is N
When applied to each element with and without T plating, it can be seen that the element of the present invention with N+ plating has a low resistance, so current is immediately limited by self-heating that causes a large current to flow. To explain the example of curve ■ in Figure 7, when 103 mA flows, the current limiting operation takes effect within 5 to 8 seconds and the circuit current I is reduced to 5 mA.
The current will continue to be limited to a certain extent, and after the current is limited, the power supply is generally turned off and the element is allowed to cool, allowing the device to return to the steady state. This is why it is called a self-resetting overcurrent protection device.

(Effects of the Invention) The self-resetting overcurrent protection element according to the present invention has a large positive temperature coefficient of resistance and has a small resistance value, so it can obtain a large rated current even at a low operating voltage. It has excellent properties that could not be obtained with conventional products, and these properties can be adjusted arbitrarily by adjusting the amount of metal plating on carbon black, can be made smaller, and can be used in low-voltage circuits that could not be used with conventional products. It has great practical effects and has a wide range of uses.

[Brief explanation of drawings]

FIG. 1 is a plan view (a) and a cross-sectional view of a self-resetting overcurrent protection element according to the present invention! bl, Figures 2 and 3 are the resistance-temperature characteristics of the overcurrent protection element 9, Figure 4 is the test circuit diagram of the overcurrent protection element, and Figures 5 and 6 are the voltage of the overcurrent protection element. -Current characteristic diagram, FIG. 7 is a side diagram of the current limiting characteristic of the overcurrent protection element. 1... Alumina substrate, 2a, 2b... Electrode, 3...
...Carbon black graft polymer, 4...Self-resetting overcurrent protection element. (, +; 龜、i ('C1 臂ミ→-んSち、7陻 (0C) 5 prisoners 164 7 prisoners 3 sales (Hoshosho (self-proposal) July 1985 Commissioner of the Patent Office Michibe Uga 1, Indication of the case Japanese Patent Application No. 127257/1986 2, Name of the invention Self-resetting overcurrent protection device 3, Person making the amendment Relationship to the case Applicant Daito Tsushinki Co., Ltd. Nippon Bionics Co., Ltd. Company 4, Agent 1-23-1 Nishi-Shinjuku, Shinjuku-ku, Tokyo 5. Column 6, “Detailed Description of the Invention” of the specification to be amended, Contents of the amendment

Claims (1)

[Claims] It is characterized by graft polymerizing a vinyl monomer onto carbon black particles whose surface is partially plated with metal, and then heating the mixture with an epoxy resin added as a crosslinking agent.The resulting cured product is used as an element. Self-resetting overcurrent protection element.