JPH0528883B2 - - Google Patents

Description

[Detailed description of the invention]

(Industrial Application Field) The present invention relates to a method for manufacturing a voltage nonlinear resistor, and more specifically, to a method for manufacturing a voltage nonlinear resistor suitable for a lightning arrester element with little variation in electrical characteristics. . (Prior art) Conventionally, when manufacturing a voltage nonlinear resistor, Bi ₂ O ₃ , Co ₂ O ₃ , MnO ₂ ,
When various additives such as Sb ₂ O ₃ , Cr ₂ O ₃ , SiO ₂ , NiO, glass, etc. are pulverized, the entire additives are mixed and pulverized at once. (Problems to be Solved by the Invention) However, as described above, when pulverizing additives, if the entire additive is mixed and pulverized at once,
Since the hardness and particle size of the metal oxides supplied as raw materials for each additive vary greatly, it has been extremely difficult to uniformly grind and mix the additives. As a result, the electrical properties of the resulting voltage nonlinear resistor, such as voltage nonlinearity, energized life, and lightning surge resistance, deteriorate or vary widely. The purpose of the present invention is to provide a method for manufacturing a voltage nonlinear resistor that can eliminate the above-mentioned problems and provide a constant quality with good electrical properties such as voltage nonlinearity, energized life, and lightning surge resistance. This is what we are trying to provide. (Means for Solving the Problems) The method for manufacturing a voltage nonlinear resistor of the present invention uses a raw material containing zinc oxide as a main component, bismuth oxide, cobalt oxide, manganese oxide, antimony oxide, chromium oxide, and silicon oxide. , in a method for manufacturing a voltage nonlinear resistor in which a sintered body is obtained by mixing an additive made of a metal oxide of nickel oxide and then firing the mixture,
When finely pulverizing the additives prior to mixing them into the zinc oxide raw material, the pulverized product obtained after preferentially and selectively pulverizing the additives with an average particle size of more than 2 μm to 2 μm or less. It is characterized in that the additives are finely pulverized by adding an additive having an average particle diameter of 2 μm or less to the mixture, uniformly mixing the mixture, and pulverizing the mixture. (Function) In the above-mentioned configuration, only the additives with large particle sizes are selectively pulverized prior to mixing all of the additives, and then the additives with fine particle sizes are mixed.
Even if the particle sizes of the additives supplied as raw materials are different, each component will be uniform and variations in composition will be reduced. As a result, it is possible to uniformly pulverize additives to a particle size almost the same as that of zinc oxide, and the effect is effectively exerted even when the amount of various additives that form grain boundary phases is very small. Therefore, it is possible to obtain a voltage nonlinear resistor that has good various characteristics and stable performance. In addition, when selectively pulverizing SiO ₂ having the smallest specific gravity is pulverized first, a more uniform additive can be obtained. Further, as the pulverizing method, a wet pulverizing method using a ball mill, a disper mill, etc. is preferable. A method for manufacturing a voltage nonlinear resistor containing zinc oxide as a main component will be described. First, among the additives supplied as raw materials, those with an average particle size exceeding 2 μm, such as Bi ₂ O ₃ , Co ₂ O ₃ , MnO ₂ ,
A predetermined amount of Sb ₂ O ₃ , SiO _{2 ,} etc. is pulverized to a particle size of 2 μm or less. At this time, it is preferable to crush SiO ₂ , which has a light specific gravity, first. Next, among these pulverized products and additives, additives with an average particle size of 2 μm or less,
For example, predetermined amounts of Cr ₂ O ₃ and NiO are mixed and further pulverized. At this time, additives other than metal oxides, which are the object of the present invention, such as glass frit, may be crushed at any stage of the above-mentioned crushing process. The pulverization is performed by wet pulverization using, for example, a ball mill for a predetermined period of time to obtain an additive slurry. Thereafter, a conventional organic binder and zinc oxide are mixed into the additive slurry, a granulated mixture is made using a spray dryer, and the granulated mixture is press-molded into a disk shape to obtain a compact. This molded body is heated and cooled at a rate of 60℃/hr.
The binder is scattered and removed by pre-sintering at 900°C for 2 hours. Next, an insulating coating layer is formed on the side surface of the pre-sintered molded body. For example, an oxide paste made of Bi ₂ O ₃ , Sb ₂ O ₃ , SiO _{2 ,} etc. and ethyl cellulose, butyl carbitol, n-butyl acetate, etc. added as an organic binder is applied to the side of the calcined body to a thickness of 100 to 200 μm. After coating, this is fired at 1200°C for 5 hours at a temperature increase/decrease rate of 50°C/hr to obtain a voltage nonlinear resistor. Furthermore, a glass paste prepared by adding ethyl cellulose, butyl carbitol, n-butyl acetate, etc. as an organic binder to glass powder is applied to the insulating coating layer at
Coated to a thickness of 200 μm and heated at a rate of 150 μm in air.
It is preferable to form the glass layer by heat treatment under the conditions of 1 hour at 500°C and 1 hour at 500°C. Next, both end faces of the voltage nonlinear resistor were polished smooth.
Aluminum electrodes are provided on both end faces by thermal spraying. Examples From the raw material powder obtained by the pulverization method consisting of various steps outside the scope of the present invention and the present invention shown in Table 1,
A voltage nonlinear resistor with a diameter of 47 mm and a thickness of 20 mm was created using the method described above. At this time, the additives are pulverized using a wet ball mill, and
Mixing of ZnO and ground additives was carried out using a dispersion mill. Also, among the additives used,
Bi ₂ O ₃ , Co ₂ O ₃ , MnO ₂ , Sb ₂ O ₃ and SiO ₂ had an average particle size of more than 2 μm, and NiO and Cr ₂ O ₃ had an average particle size of 2 μm or less. Thereafter, for the obtained voltage nonlinear resistor, the average value and standard deviation of each characteristic of the voltage nonlinear index, ΔV _{1 nA} after lightning surge, and leakage current ratio were determined. The results are shown in Table 1. In Table 1, the voltage nonlinearity index α is determined from the values of V _1nA and V ₁₀₀ 〓 _A based on the formula =KV〓 (: current, V: voltage, K: proportionality constant). Further, ΔV _1nA after a lightning surge indicates the rate of decrease in V _1nA when a current of 40 KA is repeatedly applied to the device 10 times with a current waveform of 4×10 μs. Furthermore, the leakage current ratio was determined by applying electricity to the device at an ambient temperature of 130° C. and an application rate of 95%, and calculating the current ratio 100 hours/0 hours after 100 hours of application of electricity to that immediately after the application of electricity.

〔Effect of the invention〕

As is clear from the detailed explanation above, according to the method for manufacturing a voltage nonlinear resistor of the present invention, the average powder diameter is
Selectively pulverize only additives larger than 2μm,
Additives with an average particle size of 2μm or less are then mixed and pulverized to obtain a uniform raw material powder, resulting in stable quality with good electrical properties such as voltage nonlinearity, charging life, and lightning surge resistance. It is possible to obtain a voltage nonlinear resistor having the following characteristics.

Claims (1)

[Claims] 1. After mixing additives consisting of metal oxides such as bismuth oxide, cobalt oxide, manganese oxide, antimony oxide, chromium oxide, silicon oxide, and nickel oxide into a raw material containing zinc oxide as a main component, In the manufacturing method of a voltage nonlinear resistor in which a sintered body is obtained by firing a mixture, the average particle size of the additive is
Preferentially and selectively reduce additives larger than 2μm to 2μm
After pulverizing the resulting pulverized material, additives with an average particle size of 2 μm or less are added to the resulting pulverized material, mixed uniformly, and further pulverized to finely pulverize the additives. A method of manufacturing a voltage nonlinear resistor. 2 The additives to be uniformly mixed after the selective pulverization are
The method for manufacturing a voltage nonlinear resistor according to claim 1, wherein the material is bismuth oxide, cobalt oxide, manganese oxide, antimony oxide, or silicon oxide. 3. The method for manufacturing a voltage nonlinear resistor according to claim 2, wherein silicon oxide among the additives is selectively crushed first. 4. The method for manufacturing a voltage nonlinear resistor according to claim 1, wherein the additives that are uniformly mixed without performing selective pulverization are chromium oxide or nickel oxide. 5. The method for manufacturing a voltage nonlinear resistor according to claim 1, wherein the pulverization is performed wet.