JPS61260608A - Manufacture of voltage non-linear resistor - 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 [Technical Field of the Invention] The present invention relates to a method for manufacturing an overvoltage protection device in an electrical system (a nonlinear resistor in which the sintered body used itself has voltage nonlinearity).

[Technical background of the invention]

A voltage nonlinear resistor is generally called a varistor, and its excellent nonlinear voltage-current characteristics are utilized to make it widely used in lightning arresters and surge absorbers for the purpose of voltage stabilization or surge absorption.

A typical example is the recently developed zinc oxide varistor. The main component is zinc oxide, and a small amount of oxides such as bismuth, antimony, cobalt, manganese, and chromium are added to this mixture for granulation.

After shaping, it is fired at high temperature in air, and the sintered body (= electrode is attached to it) is formed. Its non-linear resistance characteristics are very excellent, and the sintered body is made of zinc oxide particles and their surroundings. It consists of a grain boundary layer formed by additives surrounding the
The excellent non-linear resistance characteristics are thought to be due to the interface between the zinc oxide particles and the grain boundary layer, and it has many features such as being able to arbitrarily adjust the voltage-current characteristics to some extent.

[Problems with background technology]

However, the use of these zinc oxide-based varistors as lightning arresters for electric power has the following drawbacks. In other words, a zinc oxide element alone has poor moisture resistance and is not suitable for use in harsh environments such as lightning arresters, and the rate of change in the resistance of the nonlinear resistor when a large current pulse is applied is large. <1, therefore, it is unsuitable for an overvoltage protection device that receives lightning pulses or voltage surge pulses for a long period of time. Therefore, there has been a demand for a metal oxide nonlinear resistor that has stable electrical characteristics over a long period of time.

In response to these demands, we applied an epoxy resin coat to the side of the sintered material, which is mainly made of zinc oxide, and developed Zn7SJ.
O11, Zn! It has been proposed and implemented to form a high-resistance layer centered on S to.

However, the epoxy resin coating has poor voltage resistance characteristics, and as shown in Japanese Patent Publication No. 59-41284,
S J 011.

Although the Z nl Si O4 system had improved moisture resistance, it still had the problem of a large rate of change in resistance when a large current pulse was applied.

[Purpose of the invention]

The present invention was made in view of the above-mentioned needs, and an object of the present invention is to provide a method for manufacturing a metal oxide nonlinear resistor whose electrical characteristics are less likely to deteriorate even when overcurrent pulses are repeatedly applied over a long period of time. .

[Summary of the invention]

In order to achieve such an object, the present invention involves applying a substance containing ZnFetOs or Zn I T 104 to the side surface of a calcined body mainly composed of zinc oxide, and then sintering the side surface of the sintered body ( : By forming a high resistance I-, a voltage non-linear resistor is obtained which reduces the rate of change in varistor voltage when a large current pulse is applied.

[Embodiments of the invention]

Hereinafter, a first example using Zn1TIO4 of the present invention will be described in detail.

A non-linear resistor having such a configuration is manufactured as follows.

First, bismuth oxide (B) is added to zinc oxide (ZnO) powder.
ttos), cobalt oxide (CO, O,), manganese oxide (MnO), and chromium oxide (Crtoa) with 0.5 mol each, antimony oxide (Sb, 0.) and nickel oxide (NIO) powder with 1. In order to thoroughly mix these raw material powders, they were placed in a mixing device along with water, a dispersant, a binder, and an NAfR agent. This mixture slurry is granulated using a spray dryer so that the average particle size is, for example, 120 microns, and the powder is pressed to a diameter of 55 mm and a thickness of 301 mm.
It was molded into 11 discs. Added dispersant, binder,
After firing at 500C in air to remove lubricant in advance,
A previously prepared slurry for forming a high resistance layer was applied to the element body calcined at 20 C using a spray gun.

The slurry for forming a high-resistance layer was prepared as follows: A mixture of titanium oxide (Tto) and zinc oxide (ZnO) weighed to have a chemical formula of Zn1T104 was mixed at 11,000 m After pre-sintering for a period of time, it is pulverized to make a fine powder, and pure water is added to make a suitable slurry at a weight ratio of 1:1.At this time, about 10wt5 of bismuth oxide (BiffiOs) is added as a reaction accelerator, and A binder such as polyvinyl alcohol is added in an amount of about 0.1 wt* to increase the strength of the coating.

Next (= This slurry was coated on the element body. It was fired at a temperature of 12,000 ℃ in an air atmosphere. After polishing both sides of the sintered element thus obtained in parallel to a thickness of 201111 mm,
Electrodes were formed by spraying aluminum to obtain a voltage nonlinear resistor. The characteristics of the nonlinear resistor of the first example obtained in this manner are shown in FIG. 181 and FIG.

Figure 1 shows the vl corresponding to the number of pulse applications when a pulse current of 8 x 20 μS waveform is repeatedly applied to 5000 people.
. , A shows the rate of change. Also, the second figure is 4×10
The pass rate is shown when an impulse current with a μs waveform is applied. In Figures 1 and 2, the solid line indicates the conventional Zn18
The broken line B shows the characteristics of a nonlinear resistor in which a high resistance layer was formed by coating a substance containing i04, Zn, 8b, and O8. The characteristics of the formed nonlinear resistors are shown below. As is clear from FIGS. 1 and 2, the zfl, 'rio,
A non-linear resistor with a sintered high-resistance layer coated with a material containing .

[Other embodiments of the invention]

Next, ZnFe, 0
An example using No. 4 will be described.

The slurry for forming a high resistance layer in the second embodiment is as follows:
Use the adjusted one.

Iron oxide (Fe, Os) and zinc oxide (ZnO) are
nFe, 0. A mixture weighed to have the chemical formula of 11
After pre-sintering at 0.00C for 3 hours, the powder is pulverized to form a fine powder, and pure water is added thereto at a weight ratio of 1:1 to form a suitable slurry.

At this time, bismuth oxide (Bffi20
．． ) and 0.1wtm of a binder such as polyvinyl alcohol to increase the strength of the coating film.
Add as much as possible.

A slurry for forming a high resistance layer according to the present invention can be obtained by the above-described method.

The second embodiment is completely the same as the first embodiment except for the difference in the nature of the high-resistance layer forming slurry.

The characteristics of the non-linear resistor according to the second example obtained as described above were determined by the same method as in the example 9s1.
l～beta. That is, ■ Pulse current 5 with a waveform of 8×20μ8
vl corresponding to the number of pulse applications when applying 000 people repeatedly. The rate of change in vocalizations and the pass rate when an impulse current with a waveform of 4×10μ8 was applied were investigated.

These rate of change and pass rate were almost the same as those of the first example. Graphs corresponding to FIGS. 1 and 2 of the example of this first example are omitted.

Therefore, it can be seen that this material has almost the same effect as ZaFelOa or Zn1TiO as a material for the high resistance layer slurry.

According to the above embodiments, the nonlinear resistor of the present invention has excellent withstand voltage characteristics, has a small rate of change with respect to large current pulses, and
It can be seen that it exhibits extremely excellent stability. This means that
When the device is used in a power surge arrester, etc., it guarantees extremely high reliability and is important from a practical standpoint.

In the examples of the present invention, an oxide was used as a raw material, but any material may be used as long as it becomes an oxide when sintered, such as hydroxide, carbonate, oxalate, etc. Needless to say, it is effective. In addition, other components may be added in addition to the additives shown in Examples (=) for the purpose of improving the characteristics of the non-linear resistor. It is desirable to bake glass components or the like onto the outside of the body.

Furthermore, the calcination temperature is ZlFe, 04 or Zn! T
Of course, it is desirable to select conditions that have the same shrinkage rate as the material containing tO4.

〔Effect of the invention〕

As described above, according to the present invention, it is possible to provide a highly reliable voltage nonlinear resistor with excellent withstanding voltage characteristics and large current pulse characteristics.

[Brief explanation of drawings]

FIG. 1 is a characteristic diagram showing the rate of change in Δv1°1m after application of a large current pulse according to an embodiment of the present invention, and FIG. 2 is a characteristic diagram similarly showing the withstand voltage characteristics. Agent: Patent attorney: Noriyuki Chika (and 1 other person) / Number of Mars stamps (times) Figure 1

Claims (1)

[Claims] 1) After calcining a molded body mainly composed of zinc oxide to which an additive that causes the sintered body itself to have voltage nonlinearity is added,
ZnFe_2O_4 or Zn_2TiO_ on its side
1. A method for manufacturing a voltage nonlinear resistor, which comprises applying a material containing 4 and sintering the material to form a high-resistance layer on the side surface of the sintered body.