JPH0714706A - Ceramic ring varistor - Google Patents

Abstract

PURPOSE:To suppress the fluctuation of varister characteristics while increasing the nonlinear coefficient by providing a plurality of varistor electrodes on one main surface of a ceramic ring varistor element, an interconnection conductor layer on the other main surface, and isolation regions between the plurality of varistor electrodes. CONSTITUTION:A metal oxide paste is applied selectively to three regions split at an equal angular interval on the ring-like main surface of a varistor element 1. It is then heat treated in the atmosphere to diffuse the metal oxide (Bi2O3, Cub) into the varistor element 1 thus forming isolating regions 10, 11, 12. Silver paste is then printed between the isolating regions 10, 11, 12 on one main surface of the ceramic varistor element 1 and entirely on the other main surface. It is then baked to form first, second and third varistor electrodes 2, 3, 4 and an interconnection conductor layer 9 thus completing a ring varistor.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a ring-shaped porcelain varistor for use in spark reduction, noise prevention, etc. of small motors.

[0002]

2. Description of the Related Art A conventional ring-shaped porcelain varistor configured to be mounted on a small motor is a ring-shaped porcelain varistor body 1 as shown in FIGS. For example, 3 arranged on one main surface
It is composed of individual varistor electrodes 2, 3, 4. The varistor electrodes 2, 3, 4 of this varistor are connected to the motor circuit by connecting conductors 5, 6, 7. Note that, in FIG. 1, the varistor electrodes 2, 3 and 4 are hatched to distinguish them from others.

In this type of varistor, as is apparent from FIG. 2 which is a developed sectional view of a portion indicated by a chain line 8 in FIG.
Since the three varistor electrodes 2, 3 and 4 are arranged on the same flat surface, the current between them flows laterally,
The current concentrates on the portion where the electrode interval is narrow, the current distribution in the porcelain varistor element body 1 becomes non-uniform, and the varistor effect cannot be sufficiently obtained.

In order to solve the above-mentioned problem, as shown in FIG. 3, a relay conductor layer 9 irrelevant to electrical connection to an external circuit is provided on the other main surface (back surface) of the porcelain varistor element body 1. is there. With this structure, the varistor current flows from the first varistor electrode 2 toward the relay conductor layer 9, and then from the relay conductor layer 9 toward the second varistor electrode 3. As a result, the current component in the vertical direction of the porcelain varistor element body 1 increases, and the current distribution is made uniform. However, since there is also a lateral current component between the varistor electrodes 2, 3, and 4, the varistor current has a large current density in a region where the varistor electrodes 2, 3, and 4 have a short mutual interval, and a sufficient varistor effect is obtained. I can't. In addition, the variation in the mutual distance between the varistor electrodes 2, 3, and 4 greatly affects the variation in the varistor characteristics. That is,
When the mutual interval changes, the varistor voltage also changes, and the manufacturing variations of the varistor voltage increase. Moreover, the nonlinear coefficient cannot be increased.

Therefore, an object of the present invention is to provide a ring-shaped porcelain varistor capable of reducing the variation in varistor characteristics and increasing the nonlinear coefficient α.

[0006]

The present invention for achieving the above object provides a ring-shaped porcelain varistor element body, a plurality of varistor electrodes formed on one main surface of the porcelain varistor element body, A ring-shaped porcelain varistor including a relay conductor layer formed on the other main surface of a porcelain varistor body and an insulating region formed between the plurality of varistor electrodes of the porcelain varistor body It is a thing. It is preferable that the insulating region is a metal oxide diffusion region as described in claim 2.

[0007]

In the varistor of the present invention, the insulated region in the varistor element body has a higher resistivity than the other regions (semiconductor regions). Therefore, the lateral current of the varistor element body is suppressed between the varistor electrodes, the vertical current component between the varistor electrode and the relay conductor layer increases, the effect of increasing the nonlinear coefficient α, the effect of increasing the varistor voltage, Also, the effect of reducing variations in varistor voltage can be obtained.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A ring-shaped porcelain varistor according to an embodiment of the present invention and a method of manufacturing the same will now be described with reference to FIGS. In order to obtain a porcelain varistor element body, SrCO ₃ (strontium carbonate) and TiO ₂ (titanium oxide) were weighed in a molar ratio of 1: 1 and stirred with a ball mill for 10 hours and dried, 4 at 1200 ℃ after crushing
After firing for a period of time and pulverization again, a powder of SrTiO ₃ (strontium titanate) was obtained. Next, 0.2 mol% of each of Nb ₂ O ₅ (niobium oxide) and Y ₂ O ₃ (yttrium oxide) was added to this SrTiO ₃ , and these were stirred in a ball mill for 10 hours, dried and pulverized. To the obtained varistor porcelain material, polyvinyl alcohol was added as an organic binder in an amount of 10% by weight and granulated.
kg / cm ² , outer diameter 12 mm, inner diameter 8 mm, thickness 1 m
It was formed into a ring shape of m. Next, this molded body is
After removing the binder by heat-treating it in the atmosphere for 1 hour at
_A semiconductor ceramic was obtained by firing in a reducing atmosphere (non-oxidizing atmosphere) consisting of 22% by volume of N _{2 and} 98% by volume of N ₂ at about 1400 ° C. for 4 hours. Next, place it in the atmosphere
Re-oxidation firing was performed in the range of 1200 ° C. for 2 hours to obtain a ring-shaped porcelain varistor element body 1 composed of the reduction re-oxidation type semiconductor porcelain shown in FIG.

Next, a metal oxide paste containing 75% by weight of Bi ₂ O ₃ (bismuth oxide), 5% by weight of CuO (copper oxide) and 20% by weight of a resin varnish was prepared. Next, this metal oxide paste is selectively applied to a region obtained by dividing the ring-shaped main surface of the varistor element body 1 of FIG. 1 into three at equal angular intervals, and subjected to a heat treatment at 850 to 1100 ° C. in the atmosphere to form a metal. An oxide (Bi ₂ O ₃ , CuO) was diffused into the varistor element body 1 to form the insulating regions 10, 11 and 12 shown in FIG.

Next, as shown in FIGS. 6 and 7, the insulating regions 10, 11, 1 on one main surface of the porcelain varistor element body 1 are formed.
The silver paste (conductive paste) is printed between the two main surfaces and on the other main surface, and baked at 600 to 1000 ° C. to form the first, second and third varistor as in FIGS. 1 and 2. The electrodes 2, 3, 4 and the relay conductor layer 9 were formed to complete the ring-shaped varistor. For the motor, as shown in FIG. 6, the first, second and third varistor electrodes 2,
3, 4 are connected by connecting conductors 5, 6, 7. In addition, FIG.
In the figure, the varistor electrodes 2, 3 and 4 are hatched to distinguish them from others. Further, FIG. 7 shows a developed cross section along a chain line 8 in FIG.

In the varistor of this embodiment, insulating regions 10, 11 and 12 are provided between the varistor electrodes 2, 3 and 4, and the resistivity of this portion is the other portion, that is, the varistor electrodes 2, 3 and 4. Since it is larger than the resistivity of the lower part of 4,
The lateral current is significantly limited and most of the current flows from the varistor electrodes 2, 3, 4 to the relay conductor layer 9 or vice versa.

The average value of the varistor voltage E10 of 100 varistor manufactured as described above was calculated to be 10.8.
It was V. The varistor voltage E10 is an inter-electrode voltage when 10 mA is applied between two electrodes selected from the three varistor electrodes 2, 3, 4. The standard deviation (variation) of the varistor voltage E10 of 100 varistor was calculated and found to be 6.7%. The average value of the non-linear coefficient α of 100 varistor was 5.9. The non-linear coefficient α was calculated based on the varistor voltage E10. Also,
In order to know the resistance values of the insulated regions 10, 11, and 12, the insulation resistance between the varistor electrodes 2, 3, and 4 was found to be about 500 MΩ when a direct current of 15 V was applied for 30 seconds.

For comparison, the insulated regions 10, 11, 1
The same varistor as that of the embodiment was prepared except that 2 was not provided, and the same measurement as that of the embodiment was performed. The varistor voltage E10 was 10.3 V, and the variation of the varistor voltage E10 was 1.
It was 2.9% and the non-linear coefficient α was 5.1. As is clear from the comparison between the example and the comparative example, according to this example, the varistor voltage E10 is somewhat high, the variation of the varistor voltage E10 is significantly small, and the nonlinear coefficient α is somewhat large.

[0014]

MODIFICATION The present invention is not limited to the above-mentioned embodiments, and the following modifications are possible. (1) In the embodiment, the insulated regions 10, 11 and 12 can be obtained by a simple method of applying a metal oxide paste and diffusing it. However, in order to further simplify the production, in the reducing atmosphere, After firing, the metal oxide paste is applied to the inter-electrode region, and thereafter, the metal oxide is diffused into the varistor element body 1 at the same time as the reoxidation treatment at 900 to 1200 ° C. in the atmosphere, and the insulating regions 10 and 11, You may get twelve. Further, a metal oxide paste is selectively applied to the varistor element body 1, and a conductor paste for electrodes (silver paste) is applied and heat-treated to diffuse the metal oxide and at the same time bake the electrode material. , Insulated region 10,
11, 12 and varistor electrodes 2, 3, 4 and relay conductor layer 9
And may be formed substantially simultaneously. (2) The varistor porcelain is not limited to the SrTiO ₃ system porcelain, but may be (Sr, Ba, Ca) TiO ₃ system porcelain, SnO system porcelain, ZnO system porcelain, TiO ₂ system porcelain, and the like. (3) The composition of the metal oxide paste for forming the insulated regions 10, 11, 12 can be variously changed.
Alternatively, the metal oxide paste may be selectively applied to the varistor element body 1 on both main surfaces of the varistor element body 1 and diffused from both sides. (4) The relay conductor layer 9 can be divided at the portion facing the intermediate portion of each varistor electrode 2, 3, 4. That is, a plurality of relay conductor layers 9 can be provided alternately with respect to the varistor electrodes 2, 3, 4.

[Brief description of drawings]

FIG. 1 is a plan view showing a conventional varistor.

FIG. 2 is a developed sectional view of the varistor of FIG.

FIG. 3 is a developed sectional view of another conventional varistor.

FIG. 4 is a plan view showing a varistor element body before forming an insulating region of a varistor according to an embodiment of the present invention.

FIG. 5 is a plan view showing a varistor element body in which an insulated region is formed.

FIG. 6 is a plan view showing a varistor of a completed embodiment.

7 is a developed sectional view of the varistor of FIG.

[Explanation of symbols]

 1 Varistor Element Body 2, 3, 4 Varistor Electrode 9 Relay Conductor Layers 10, 11, 12 Insulated Area

Claims (2)

[Claims] 1. A ring-shaped porcelain varistor element body, a plurality of varistor electrodes formed on one main surface of the porcelain varistor element body, and a relay formed on the other main surface of the porcelain varistor element body. A ring-shaped porcelain varistor including a conductor layer and an insulating region formed in a portion of the porcelain varistor element body between the plurality of varistor electrodes. 2. The ring-shaped ceramic varistor according to claim 1, wherein the insulating region is a diffusion region of a metal oxide.