JPS6236610B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for manufacturing a voltage nonlinear resistor containing zinc oxide (ZnO) as a main component, and particularly to a method for insulating the side surfaces thereof.

Conventionally, in the side insulation of voltage nonlinear resistors (hereinafter abbreviated as resistors) whose main component is ZnO,
After firing, an epoxy-based organic substance is applied to the side surface of the resistor for insulation, or before the resistor is fired, various inorganic compounds are applied to the side surface of the resistor and then fired to form a glassy or crystalline insulating film. It was insulated.

However, the former method has the disadvantage that moisture is adsorbed to the resistor due to poor adhesion between the applied epoxy-based organic substance and the resistor, resulting in significant deterioration of characteristics and weakening of short wave tail resistance. Furthermore, since there is a difference in thermal expansion between the resistor and the epoxy organic material, there is a drawback that the epoxy organic material may crack due to thermal shock, causing deterioration. In addition, in the latter method, it is necessary to match the shrinkage rates of the resistor and the inorganic compound during firing, so after the resistor is first fired to shrink to some extent, the inorganic compound is applied and the main firing is performed. , a side insulation coating is formed. Therefore, in this case, the firing must be carried out twice, which increases fuel (including electricity) costs, and the firing apparatus is used twice, which increases manufacturing costs. Furthermore, both methods have the disadvantage that considerable skill and equipment are required to make the side insulating coating uniform to the required thickness.

For this reason, a method has been proposed in which antimony oxide (such as sb ₂ O ₃ ) is placed in the firing container during firing of the resistor, and a side insulating film is formed by a gas-solid phase reaction at the same time as the firing. The method utilizes a gas-solid phase reaction between antimony oxide vapor and the resistor, so it has good adhesion between the resistor and the insulating film.
An insulating film with dense and uniform crystal grains without pinholes is obtained, and various electrical properties such as current discharge withstand, corona resistance, and arc resistance are significantly improved compared to when epoxy-based organic materials are applied. In addition, compared to the case where an inorganic compound is applied and fired, there is no need to consider the shrinkage rate, the firing can be completed in one time, and the manufacturing is easy and inexpensive. However, in this case, the evaporation rate of Sb ₂ O ₃ is 0.07 at 1000℃
Relatively fast at 0.45mg/min at 1050℃. For this reason, the side surfaces of the resistor react with gas remaining in the resistor, and when the temperature increases, the residual gas is released from the resistor, reducing the adhesion between the resistor and the side insulation coating, resulting in electrical Various properties also deteriorated.

The present invention eliminates the above-mentioned drawbacks, makes it possible to form a side insulating coating of a voltage non-linear resistor with good adhesion, improving various electrical characteristics, and making the side insulating coating easy and inexpensive to manufacture. An object of the present invention is to provide a method for manufacturing a voltage nonlinear resistor that can be formed into a voltage nonlinear resistor.

Embodiments of the present invention will be described below with reference to the drawings.
First, the configuration of the firing apparatus will be explained using FIG. The second material is preferably alumina or a zinc oxide sintered plate, and in particular, the zinc oxide sintered plate has the same quality as the main component of the resistor, so there is no risk of impairing the characteristics of the resistor. Reference numeral 3 denotes a compression-molded voltage non-linear resistor whose main component is ZnO, and the resistor 3 is placed on the upper surface of the pedestal 2 with a padding material 4 in between. The bedding powder 4 is for preventing welding between the pedestal 2 and the resistor 3.
A substance similar or the same as the components of the resistor 3 is required, such as alumina, granulated powder of the resistor 3, or resistor 3.
Powder etc. that are calcined and crushed are used. If the pedestal 2 is made of the same material as the resistor 3, the bedding powder 4 may be omitted. 5 is a coating agent applied to the inner surface of the sheath 1 to form a side insulation coating on the resistor 3; 6 is the sheath 1;
The lid 6 is made of the same material as the sheath 1 and covers the upper part of the sheath 1 in a substantially airtight manner. The coating agent 5 may be applied to a part or all of the inner surface of the sheath 1 or to the inner surface of the lid 6, and it is sufficient if it is provided inside the firing container. In fact, a shielding member is provided on the upper surface of the resistor 3 to prevent the formation of an insulating film.

Next, we will discuss the manufacturing method using the above firing equipment. First, resistor 3 is made of ZnO (91 mol%).
A total of 9 mol % of Sb ₂ O ₃ , Bi ₂ O ₃ , CO ₂ O ₃ , MnO ₂ , Cr ₂ O ₃ , SiO ₂ and the like are added, thoroughly mixed, and then compression molded into an appropriate shape. For example, diameter 40mmφ, thickness 30
A cylindrical molded body with a diameter of mm. Further, the coating agent 5 uses Sb ₂ O _{3 and} oxides that react with Sb ₂ O ₃ such as Bi _{2 O 3} , ZnO, and _{SiO 2} as starting materials _.
After weighing to give a molar ratio of 10ZnO-20SiO ₂ , water is added to these and thoroughly mixed to obtain a slurry, which is applied to the inner wall of the sheath 1 and dried. and,
The resistor 3 is placed inside the sheath 1 as shown in FIG. 1, and the lid 6 is closed.
to almost seal the sheath 1. 1000℃~1500 in this state
℃ (preferably 1100℃ to 1300℃), Sb ₂ O ₃ and Bi ₂ O ₃ in the coating agent 5 evaporate, the inside of the sheath 1 is filled with these atmospheres, and the resistor 3 A high-resistance insulating film is formed on the surface of the resistor 3 by a gas-solid phase reaction with ZnO, Bi ₂ O ₃ , etc. inside the resistor 3. When this insulating film was examined by X-ray diffraction, as shown in FIG. 2, it was found that spinel (Zn _{2 .33} Sb _{0 .67} O ₄ ) was the main component. This was also confirmed when examined using an X-ray microanalyzer.

In the above gas-solid phase reaction, the coating agent 5 is
During the heating process of SbO ₃ and ZnO up to 1000℃, ZnSb ₂ O ₆ begins to be formed at 700℃ due to the reaction ZnO + Sb ₂ O ₃ + O ₂ →ZnSb ₂ O ₆ ...(1), and the amount of formation increases up to about 800℃. increases and then decreases. Also, due to the reaction 7ZnO + Sb ₂ O ₃ + O ₂ →Zn ₇ Sb ₂ O ₁₂ ...(2), Zn ₇ Sb ₂ O ₁₂ (Zn ₂ . ₃₃ Sb ₀ . ₆₇ O ₄ ) becomes 800
It begins to form around ℃ and increases thereafter. or,
ZnO and SiO ₂ of the coating agent 5 form Zn ₂ SiO ₄ at around 800° C. due to the reaction 2ZnO+SiO ₂ →Zn ₂ SiO ₄ (3).

Furthermore, ZnO, Bi ₂ O ₃ and Sb ₂ O ₃ of coating agent 5 are converted into Zn 2 Sb 3 Bi by the reaction of 4ZnO + 3Bi ₂ O ₃ + 3Sb ₂ O ₃ + O ₂ →Zn _{2 Sb 3} Bi ₃ O ₁₄ ( ₄ ) ₃ O ₁₄ (virochloa)
It begins to form at around 700°C, and after reaching a maximum at around 900°C, it begins to decrease.

The evaporation of Sb ₂ O ₃ is suppressed by the reactions of equations (1) and (2) above, and the reaction rate of ZnO that reacts with Sb ₂ O ₃ is increased by SiO ₂ by the reaction of equation (3) above. suppressed. However, ZnO−Bi ₂ O ₃ −Sb ₂ O ₃ shown in Fig. 3
-As can be seen from the change in crystal structure of the SiO ₂ system during heating, ZnSb ₂ O ₆ also changes at temperatures above 800℃.
Because it changes to Zn ₂ Bi ₃ Sb ₃ O ₁₄ and Zn ₇ Sb ₂ O ₁₂ ,
As a result, the evaporation of Sb ₂ O ₃ was suppressed by the reactions of equations (2), (3), and (4). Therefore, in order to evaporate Sb ₂ O ₃ , an amount exceeding that required for the reactions of equations (2), (3), and (4) is required, so Sb ₂ O ₃ and ZnO, Bi ₂ O ₃ , and From formulas (2) to (4), the ratio with SiO ₂ is Sb ₂ O ₃ /ZnO>
4/13, also Sb ₂ O ₃ /Bi ₂ O ₃ > 4/3, also Sb ₂ O ₃ /SlO
₃ > 4/1. In this way, since Sb ₂ O ₃ exists in an amount exceeding the amount required for the above reaction, the Sb ₂ O ₃ remaining in the above reaction
evaporates at around 1000℃. However, this evaporation is slower than in the case of a single application of Sb ₂ O ₃ because Sb ₂ O ₃ is consumed in the above reaction. Figure 4 shows the application agent 5.
Sb ₂ O ₃ single case and 60Sb ₂ O ₃ −10Bi ₂ O ₃ −10ZnO−
This figure shows the relationship between temperature and Sb ₂ O ₃ evaporation amount in the case of 20SiO ₂ , and it can be seen that evaporation is slower in the latter case than in the former case. On the other hand, resistor 3 is 800
It begins to shrink at around 1000°C, and in addition to ZnO, it also contains ZnSiO ₄ , Zn ₂ . ₃₃ Sb ₀ . ₆₇ O ₄ , Zn ₂ Bi ₃ Sb ₃ O ₁₄ ,
14Bi ₂ O ₃ −Cr ₂ O ₃ etc. are formed. As a result, on the side surface of resistor 3, Sb ₂ O ₃ vapor and ZnO of resistor 3
A high-resistance insulating film containing Zn ₂ . ₃₃ Sb ₀ . ₆₇ O ₄ as a main component is formed by a gas-solid phase reaction. Also, Bi ₂ O ₃
The vapor suppresses evaporation from Bi ₂ O ₃ of the resistor 3, which governs the voltage non-linearity of the resistor 3, and
It has the effect of promoting the reaction of Sb ₂ O ₃ with vapor.

In the above example, Sb ₂ O ₃ in the coating agent 5 is
Because it reacts with _SiO2 through ZnO and ZnO
Evaporation of Sb ₂ O ₃ becomes slower. Therefore, a gas-solid phase reaction occurs after the resistor 3 sufficiently contracts and releases gas, and no residual gas is generated, resulting in good adhesion between the resistor 3 and the side insulating coating, and current discharge. Electrical properties such as durability, corona resistance, and arc resistance are improved. Incidentally, as a result of measuring the short wave tail discharge resistance of resistor 3, it was found that, for example, coating material 5
In the case of 60Sb ₂ O ₃ −10Bi ₂ O ₃ −10ZnO−20SiO ₂ , apply 4 × 10 μS impulse twice.
It showed a discharge capacity of 75KA. In addition, since the method does not apply the coating material 5 directly to the side surface of the resistor 3, there is no need to consider the difference in shrinkage rate between the resistor 3 and the coating material 5 during firing, and the method is simple and inexpensive with one firing. A high-resistance side insulating film can be formed on the surface.

In the above embodiment, the resistor 3 housed in the sheath 1 may be compressed and then pre-fired to shrink to some extent. Alternatively, instead of forming the coating agent 5, the slurry may be dried into powder and spread within the sheath 1. Furthermore, ZnO, Bi ₂ O ₃ and SiO ₂ also include salts, such as carbonates, which thermally decompose with these to become ZnO, Bi ₂ O ₃ and GiO ₂ .

As described above, in the present invention, when firing a voltage non-direct resistor whose main component is zinc oxide, antimony oxide reacts with the antimony oxide in the firing container to prevent evaporation of the antimony oxide. Since a retardant oxide is provided and this oxide is fired using Bi ₂ O ₃ , ZnO and SiO ₂ , the evaporation of antimony oxide is slower than when only antimony oxide is provided, and in particular, the resistor shrinks sufficiently. after
Since a gas-solid phase reaction with Sb ₂ O ₃ occurs, a dense and high-resistance insulating film can be obtained, and the adhesion of the film is extremely good, as well as good electrical properties.

[Brief explanation of the drawing]

FIG. 1 is a longitudinal sectional front view of a firing device according to the present invention;
FIG. 2 is an X-ray diffraction diagram of the side insulating coating according to the present invention, and FIG. 3 is an X-ray diffraction diagram of the ZnO-Bi ₂ O ₃ -Sb ₂ O ₃ according to the present invention.
FIG. ₄ is a characteristic diagram showing the relationship between temperature and Sb ₂ O ₃ evaporation amount according to the present invention. 1... Sheath (container for firing), 3... Voltage nonlinear resistor, 5... Coating agent, 6... Lid.

Claims (1)

[Claims] 1. A voltage nonlinear resistor containing zinc oxide as a main component is stored in a firing container, and an oxide that reacts with antimony oxide to retard the evaporation of antimony oxide is mixed with antimony oxide. In the manufacturing method, when the resistor is fired after being placed in the firing container, a side insulating coating is obtained on the resistor by a gas-solid phase reaction at the same time as the firing. A method for manufacturing a voltage nonlinear resistor, characterized in that the oxide that retards the voltage is comprised of Bi ₂ O ₃ , ZnO, and SiO ₂ .