JP2718175B2 - Voltage nonlinear resistor and method of manufacturing the same - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a voltage non-linear resistor mainly composed of zinc oxide used mainly in the field of electric power and a method of manufacturing the same.

2. Description of the Related Art A voltage non-linear resistor is generally called a varistor, and is widely used as a voltage stabilizing or surge absorbing element. Among them, zinc oxide is the main component, and a small amount of Bi ₂ O ₃ , Co ₂ O ₃ ,
Zinc oxide varistors to which metal oxides such as MnO ₂ , Sb ₂ O ₃ , and Cr ₂ O ₃ are added have been used in recent years as conventional elements for gapless arresters because of their large surge current capability and excellent voltage nonlinearity. Widely used instead of carbide varistors.

When this zinc oxide type varistor is used as an arrester, the discharge withstand characteristics and the charging life characteristics are extremely important characteristic elements. Here, the discharge withstand characteristic is a limit value of a current at which an impact current of 4/10 μs can be applied twice in the same direction at 5-minute intervals. The voltage application life characteristic is the life of the varistor element estimated when a rated voltage is applied to the zinc oxide type varistor element, and an acceleration test for increasing the normal temperature and the power application rate is performed.

Conventionally, as a method for producing a voltage non-linear resistor, for example, as described in JP-B-53-29375, zinc oxide as a main component and several metal oxides such as Bi ₂ O ₃ After compressing and molding the raw material powder added with
The calcined body is calcined in a temperature range of 800 ° C. to 1000 ° C., and a paste-like side agent made of Bi ₂ O ₃ , Sb ₂ O ₃ , SiO ₂ or the like is applied to the side surface of the obtained calcined body. ° C. by firing to 1300 ° C., and the side surface agent and element reaction, and Zn ₂ SiO ₄ in the sintered body side Z
A side high-resistance layer made of n ₇ Sb ₂ O ₁₂ was formed to obtain a voltage non-linear resistor.

However, when the high-resistance layer is formed by reacting the side agent with the element as described above, it is difficult to control the reaction between the side agent and the element, has a uniform thickness, and has a defect. It is difficult to obtain a small side surface high resistance layer, and as a result, there is a problem that the discharge withstand characteristics are low and the variation is large.

The present invention solves such a conventional problem,
The purpose of the present invention is to improve the performance of the voltage non-linear resistor, that is, to significantly improve the discharge capability and stabilize the quality.

Means for Solving the Problems In the present invention, in order to solve the above-mentioned conventional problems, SiO ₂ , Al ₂ O ₃ , ZrO ₂ , MgO
A main component at least one or more oxides selected from among those having a side surface high-resistivity layer including AlPO ₄ of 1.0 to 25.0 mol%. Further, after the sintered body is heat-treated at a temperature range of 450 ° C. to 700 ° C., SiO ₂ , Al
₂ O ₃ , ZrO ₂ , MgO, at least one oxide selected from the main component, and apply a side high resistance agent containing aluminum phosphate salt, baking at a temperature range of 200 ℃ ~ 700 ℃ The treatment is performed to form a high-side resistance layer.

According to the present invention, the calcining step and the formation of the side surface high-resistance layer do not require the sintering atmosphere, delicate control of the temperature rise / fall curve, and furthermore, SiO ₂ , Al ₂ O ₃ , ZrO ₂ , MgO, etc. Since the oxide has high insulation properties and good adhesion between AlPO ₄ and the sintered body, a voltage non-linear resistor having stable quality and high discharge capability can be obtained.

EXAMPLES Hereinafter, the voltage nonlinear resistor of the present invention and a method for manufacturing the same will be described in detail with reference to examples.

First, 0.5 mol% of Bi ₂ O _{3 based} on the total amount is added to ZnO powder,
Co ₂ O ₃ 0.5 mol%, MnO ₂ 0.5 mol%, Sb ₂ O ₃ 1.0 mol%,
0.5 mol% of Cr ₂ O _{3 and} 0.5 mol% of NiO were added, sufficiently pulverized and mixed, and then granulated to obtain a raw material powder. This raw material powder was compression molded to a size of 40 mm in diameter and 30 mm in thickness. Next, this molded body was fired in a temperature range of 1100 ° C. to 1250 ° C. to obtain a sintered body. This sintered body was heat-treated in a temperature range of 450 ° C to 700 ° C. Next, Al was applied to the side surface of the heat-treated sintered body.
A side surface high resistance agent containing ₂ O ₃ as a main component and containing an appropriate amount of aluminum phosphate was applied by a dipping method. Here, the application amount of the side surface high resistance agent was measured after drying the sintered body at 120 ° C. for 30 minutes or more. The sintered body of the side surface high resistance coating material thus obtained was subjected to a baking treatment in a temperature range of 200 ° C to 700 ° C. After that, both end surfaces of the sintered body were polished to form a sprayed aluminum electrode to obtain a voltage non-linear resistor. FIG. 1 is a cross-sectional view of a voltage non-linear resistor obtained as described above, wherein 1 is a sintered body mainly composed of zinc oxide, 2 is Al ₂ O ₃ as a main component and AlPO ₄ is a sub-component. The side high resistance layer 3 is a sprayed electrode of aluminum.

Next, as a comparative study example, a green compact compressed to the same shape using the same raw material powder as in the example of the present invention was calcined at 900 ° C., and then Bi ₂ O ₃ , Sb ₂ O ₃ , and SiO ₂ were removed. Paste-like side agents containing 10 mol%, 10 mol%, and 80 mol%, respectively, were applied, and baked and heat-treated under the same conditions as in the examples of the present invention, thereby preparing samples (conventional examples).

Table 1 below shows the appearance, initial characteristics, discharge withstand characteristics, and charging life characteristics of the voltage non-linear resistor according to the present invention and the conventional example. Here, the number of samples is n = 10 for each lot. As for the discharge withstand characteristic, an impulse of 4/10 μs was applied twice in the same direction at 5 minute intervals, and stepped up from 40KA. In addition, the charging life characteristic is 130
The test was performed under the conditions of ° C and a power application rate of 95% (AC, peak value). In addition, as for the charging life characteristics, the time required for the leakage current to reach 3 mA (peak value) was measured.

According to Table 1, there is no problem when baking the side surface high resistance agent at low temperature, but when baking at 500 ° C or more, the heat treatment at 450 ° C or more must be performed beforehand to peel off the side high resistance layer. It can be seen that a discharge occurs and the discharge withstand capability characteristic is lowered. However, when the heat treatment is performed at a temperature of 750 ° C. or more, it is understood that the initial characteristics are deteriorated and the charging life characteristics are deteriorated. Therefore, the heat treatment is desirably performed in a temperature range of 450 ° C to 700 ° C. Next, the baking condition of the side surface high resistance agent is such that the discharge withstand characteristic is low at 150 ° C. and the charging life characteristic deteriorates at 800 ° C. Therefore, it is desirable to perform the baking treatment in a temperature range of 200 ° C. to 700 ° C. Under these conditions, the discharge withstand characteristics show good values and small variations. On the other hand, in the conventional example, it is found that there is a large variation in the discharge withstand characteristics. This is presumably because the calcined body and the side surface high resistance agent are reacted during firing in the conventional method, so that the reaction is not performed uniformly and the thickness of the side surface high resistance layer becomes uneven.

Next, the composition ratio of Al ₂ O ₃ and AlPO ₄ in the side surface high resistance layer was examined by adjusting the addition amount of the aluminum phosphate salt in the side surface high resistance agent. The results are shown in Table 2 below. Here, the heat treatment condition of the sintered body is 500 ° C., and the applied weight of the overcoat agent is 15 mg per unit area of the sintered body.

From Table 2, it can be seen that when the amount of AlPO ₄ in the side surface high resistance layer is 0.01 mol%, the adhesion strength between the side surface high resistance layer and the sintered body is not sufficient, and the discharge withstand characteristics are low. Further, when it exceeds 25.0 mol%, the side high-resistance layer is peeled off during the baking treatment, and it is found that the discharge withstand characteristics deteriorate. based on the above results,
The optimum amount of AlPO ₄ side high-resistance layer is found to be from 0.1 to 25.0 mol%.

Next, Table 3 below shows the relationship between the applied amount of the side surface high resistance agent and various characteristics. Here, the side high resistance agent is Al
It was adjusted so that PO ₄ was 5.0 mol%. The heat treatment temperature of the sintered body is 500 ° C. Furthermore, the amount of side high resistance agent applied is controlled by the viscosity and the number of applications, and after application
After drying at 120 ° C. for 30 minutes or more, the coating weight was measured.

From Table 3, when the application amount of the side surface high resistance agent is 0.1 mg,
Since the thickness of the high-resistance layer is small and the withstand voltage is low, the discharge withstand characteristic is low. If the coating amount exceeds 100 mg, the side high-resistance layer is peeled off. Therefore, the optimal amount of application is 1.0 to 10.00.0 mg
/ cm ² .

In this example, only the case where the main component of the side surface high resistance agent was Al ₂ O ₃ was described, but it was confirmed that the same effect was obtained in any case of SiO ₂ , ZrO ₂ , and MgO. . Also, the dipping method was used for applying the side high resistance agent,
This is the same as the effect of the present invention as long as a uniform coating method such as a spray method or a brush coating method is possible.

Effects of the Invention As described above, according to the present invention, a sintered body containing zinc oxide as a main component is heat-treated in a temperature range of 450 ° C to 700 ° C, and SiO ₂ , A
l ₂ O _3, ZrO _2, as a main component one or more oxides selected from among MgO, coated side high-resistance agent containing aluminum phosphate salt, baking in the temperature range of 200 ° C. to 700 ° C. By performing the treatment, a side-surface high-resistance layer having a uniform thickness and a high withstand voltage can be formed on the side surface of the sintered body. As a result, a voltage non-linear resistor having a high discharge withstand characteristic and a small characteristic variation can be obtained. be able to.

[Brief description of the drawings]

FIG. 1 is a sectional view of a voltage non-linear resistor according to an embodiment of the present invention. 1 ... sintered body, 2 ... side high resistance layer, 3 ... electrode.

Claims (3)

(57) [Claims] 1. A side face of a sintered body mainly composed of zinc oxide,
The main component is at least one oxide selected from SiO ₂ , Al ₂ O ₃ , ZrO ₂ and MgO, and AlPO ₄ is 1.0 to 25.0 mol%
A voltage non-linear resistor having a side high resistance layer. 2. A sintered body comprising zinc oxide as a main component at a temperature of 450.degree.
After heat treatment in a temperature range of 00 ° C., Si
O ₂ , Al ₂ O ₃ , ZrO ₂ , at least one oxide selected from MgO as a main component, coated with a side surface high resistance agent containing aluminum phosphate, 200 ℃ ~ 700 ℃ A method for manufacturing a voltage non-linear resistor, wherein a side surface high resistance layer is formed by performing a baking treatment in a temperature range. 3. The application amount of the side surface high resistance agent on the side surface of the sintered body is as follows:
3. The method for producing a voltage non-linear resistor according to claim ² , wherein after drying is in the range of 1.0 to 100.0 mg / cm ² .