JPS5832766B2 - Method for forming an insulating layer for preventing external flash of a non-linear resistor - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for forming an insulating layer for preventing external flashover on the side surface of a non-linear resistor whose main component is, for example, zinc oxide.

The non-linear resistance element is as shown in the figure, and includes a non-linear resistor 1 formed into a cylinder or disk shape and sintered at high temperature, electrodes 2 provided on the upper and lower surfaces of the non-linear resistor 1, and an insulator layer 3 provided on the side surfaces. It becomes more.

The insulator layer 3 is provided to prevent external flashovers of the non-linear resistor 1, such as air discharges during the absorption of impulse currents, which would otherwise occur.

The material constituting the insulator layer 3 may be organic resin or inorganic material such as B, which reacts with the nonlinear resistor 1 itself.
i2O3-8b203-8iO2 type or low melting sealing glass is used.

When an organic resin is used, its expansion coefficient is different from that of a non-linear resistor, which causes peeling and carbonization of the resin due to corona discharge, making it difficult to use in general.

Therefore, inorganic insulators are used, and the following steps are generally performed.

For example, 5b is used as a substance to form an insulating film on the side surface of a molded product made by mixing and molding zinc oxide with other additives.
A mixed powder of 2o3S t 02 B s 203 and an organic binder of appropriate viscosity such as ethyl cellulose, butyl calpitol, and n-butyl acetate are thoroughly mixed and made into a slurry.

Apply by blade method, dip method, spray method, etc.

After drying the solvent, the molded body whose side surfaces are coated with an insulating material is led into a furnace and sintered at a high temperature of 1000°C to 1500°C.

As a result, a non-linear resistor having a side insulator layer consisting only of inorganic components is obtained.

In this way, inorganic substances are generally handled in powder form, but since the powder itself does not have adhesive strength, it is necessary to integrate it with the molded body, so a wet method involving an organic binder and a solvent is used. Surface coating is performed.

This solvent and organic binder decompose and desorb at high temperatures, and the inorganic components react and adhere to the molded article itself.

As mentioned above, in the case of the conventional wet method, ■ The production process is somewhat complicated and is not suitable for mass production.

■ Volatile solvents are used to speed up drying, but these solvents are toxic and pose a fire risk.

■ Among the properties of the slurry to be applied, the viscosity in particular changes due to the presence of volatile components, and changes considerably depending on temperature, making it difficult to obtain a film with a constant thickness.

■ It is also difficult to freely control the thickness.

There were problems such as:

This invention was made in order to eliminate the drawbacks of the above-mentioned conventional methods, and eliminates the need for the use of solvents, thus eliminating toxicity and the risk of fire, and making it possible to easily obtain an insulating film with a uniform thickness. A method of forming an insulating layer for preventing external flash faults is provided.

That is, the present invention is directed to a predetermined portion of a non-linear resistor according to known prior art, which is made of zinc oxide as a main component and sintered at 1000 to 1500 °C with various additives added, or a non-linear resistor made by sintering. A thin material such as a sheet or tape made of a mixture of an inorganic powder to form an insulating layer for external flash protection and an organic resin that can be decomposed by heating is placed on a predetermined part of the molded body forming the body. This method is characterized in that a flash-flash prevention insulating layer of a desired thickness is formed on a predetermined portion of the non-linear resistor by coating the non-linear resistor and then heating the coating at a predetermined temperature.

The present invention will be described in more detail with reference to Examples below.

Example l Bi203 (8 mol %), 5b203 (20 m
o1%), 5 in2 (72 mol %), and an equal weight of ethylene vinyl acetate rubber are thoroughly kneaded and dispersed using a roll mixer,
Form into a sheet with a thickness of about 0.5 mrIL.

Diameter 7 made by mixing and molding zinc oxide with various trace additives.
The above sheet was cut into a tape shape with a size of 0m71L and a height of 30mm.

The element body is heated to 100°C, and the tape is attached using its heat-shrinkable and adhesive properties.

When this was fired at 1000°C to 1500°C, the element body became sintered and dense, and an inorganic insulating layer was also formed on the surface of the sintered body.

Note that the rubber decomposes and scatters during the firing process.

Example 2 Zinc oxide is the main component, various additives are added, and 1000
In place of B 1203 5b2o3S 102 used in Example 1, P
bO-S 102- Using ZnO-B2O3-based low-melting glass, make a tape in exactly the same way and attach it to the side surface.

By heating this to a sealing temperature of about 500° C., a nonlinear resistor having low-melting glass on the sintered body was obtained.

Conventionally, an insulating film layer has been formed on the surface of an element body by a so-called wet method using an organic binder and a solvent.

In the method of the present invention, as shown in the examples, an inorganic insulating material and an organic resin are mechanically mixed to form a thin material such as a sheet or tape, and this is thermocompressed to a base body, so to speak. It can be called a dry method.

In the method of the present invention, the ratio of organic resin to insulating inorganic powder is changed.

Alternatively, the thickness of the insulating layer can be easily changed by changing the thickness of the thin sheet material, and the work is simple, so if the ratio of organic resin to inorganic powder and the thickness of the thin sheet material are fixed, one It has the advantage that a wide range of film thicknesses can be obtained and individual variations can be kept small.

In addition, it is superior to the wet method in terms of improved workability and ease of mechanization, and there is no need for troublesome viscosity control.

In the above example, 2 is used as the inorganic insulating material.
Although two examples have been shown, any insulating material may be used as long as it ultimately causes a fixation reaction with the element body.

On the other hand, the organic resin and rubber are not limited to ethylene vinyl acetate rubber, but any material that can be mixed with an inorganic insulating material and can be processed into a sheet shape may be used.

For example, acrylic rubber, butyl rubber,
Examples include acrylic resin.

As described above, compared to the conventional wet method, the insulating layer formed by the method of the present invention has the following advantages: the thickness of the insulating layer can be easily controlled, the thickness is stabilized, the yield is improved, and the work efficiency is improved. It has many advantages, including superior safety and safety.

[Brief explanation of drawings]

The figure is a cross-sectional view showing the general structure of a zinc oxide nonlinear resistor. In the figure, 1 indicates a non-linear resistor, 1 indicates an insulator layer. 2... Electrode, 3...

Claims (1)

[Claims] 1. An inorganic powder to form an insulating layer for preventing external flash on a predetermined portion of a non-linear resistor formed by sintering or a molded body for forming a non-linear resistor by sintering. External flash protection for a non-linear resistor characterized by coating a thin sheet material formed of a mixture with an organic resin that can be decomposed by heating, and then heating the coated thin sheet material at a predetermined temperature. Method of forming an insulator layer for use. 2. A method for forming an insulating layer for preventing external flash of a non-linear resistor according to claim 1, wherein the inorganic powder forms a low-melting glass. 3. A method for forming an insulating layer for preventing external flash of a non-linear resistor according to claim 1 or 2, wherein the organic resin that can be decomposed by heating is rubber.