JPH1145801A - Manufacture of nonlinear resistor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve thermal stability by making the grain size of the whole nonlinear resistor uniform. SOLUTION: Zinc oxide, additives, and an organic binder are mixed and dried to make a granulated powder (S21). The granulated powder is formed into a discoidal body (S22). The formed body is calcined for making it into calcination body (S23). A solvent made by dissolving any of antimony trioxide, nickel oxide, and silicon dioxide in the organic binder is applied to the outer surface of a calcination body (S24). A high-resistant material is applied to the surface of the solvent applied to the outer surface of a calcination body (S25) and is fired to make a fired body having a high-resistant layer on the outer surface of a calcination body (S26). A solvent D made by mixing a glass powder with an organic binder and adjusted to a predetermined viscosity is applied to the surface of the high-resistant layer formed on the outer surface of the fired body (S27) and is fired (S28). Electrodes are fixed to the both ends of the fired body (S29) to make a nonlinear resistor.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of manufacturing a nonlinear resistor mainly composed of zinc oxide and mainly incorporated in a lightning arrester.

[0002]

2. Description of the Related Art Many non-linear resistors are mainly composed of zinc oxide, and additives such as bismuth oxide, antimony oxide, cobalt oxide, manganese oxide, chromium oxide, nickel oxide, silicon oxide and the like An oxide is added, and the composition is composed of a composition having high non-linearity and low heat loss.

Usually, the above-mentioned additive components are preliminarily pulverized by a ball mill or the like, and then added to zinc oxide and a binder (a binder, for example, an organic binder) to obtain a mixture. The mixture is spray-dried by a spray drier. A granulated powder with good fluidity is obtained. In addition, in the organic binder,
Water-based organic binder, for example, polyvinyl alcohol
(PVA) is used. The granulated powder is formed into a disk-shaped molded body by a die press, and after the molded body is degreased, it is calcined at a temperature of 700 to 1000 ° C. for several hours to form a calcined body.

[0004] The outer peripheral surface of the calcined body is coated with an insulating material (a high-resistance layer material) made of, for example, a ceramic.
Heat treatment is performed at a temperature of 300 ° C. to obtain a fired body having an insulating layer (a high-resistance layer, which will be described in detail later) formed on the outer peripheral surface. next,
Means are employed in which both end faces of the fired body are polished smoothly, and then the non-linear resistor is completed by spraying an electrode material made of, for example, aluminum on the both polished end faces.

[0005] The nonlinear resistor formed as described above is used for a current limiting element unit of an arrester. In particular, nonlinear resistors for lightning arresters can absorb a large amount of energy compared to general light-current surge absorbers.
A large volume or large diameter non-linear resistor is required.

Further, since the non-linear resistor has very high non-linearity, it is necessary to form a high-resistance layer on the outer peripheral surface of the fired body as described above to prevent external flashes. In order to obtain a fired body having a high resistance layer formed on the outer peripheral surface, first, zinc oxide, bismuth oxide (bismuth trioxide), antimony oxide (antimony trioxide), and silicon oxide (silicon dioxide) are wet-pulverized in a predetermined mixture. After drying, it is calcined at a temperature of 800 to 1000 ° C. to obtain a high resistance layer material.

After the high-resistance layer material is roughly pulverized and finely pulverized, an organic binder and a solvent are added and kneaded to form a paste, which is then applied to the outer peripheral surface of the calcined body by, for example, roller application, followed by heat treatment. Thus, a fired body having a high resistance layer formed on the outer peripheral surface is obtained. In some cases, a low-melting glass material is applied to the surface of the high-resistance layer and then heat-treated to form a two-layer high-resistance layer.

As described above, the non-linear resistor obtained by forming the high-resistance layer has very good characteristics against external flashes.

[0009]

The characteristics of the non-linear resistor greatly change depending on the mixing ratio of the four components used as the material of the high resistance layer. For example, reducing the amount of antimony trioxide improves the insulating properties of the non-linear resistor, but the antimony trioxide acts as a grain growth inhibitor for the zinc oxide particles in the non-linear resistor during firing. On the other hand, bismuth trioxide acts as a grain growth promoter for zinc oxide particles in the non-linear resistor during firing.

Therefore, if the amount of antimony trioxide is reduced, bismuth trioxide diffuses more from the high resistance layer into the non-linear resistor. therefore,
If the amount of antimony trioxide is reduced, the particle size of the zinc oxide particles near the outer peripheral surface of the nonlinear resistor becomes larger than the particle size of the zinc oxide particles in the central portion of the nonlinear resistor. I will.

It is known that the electrical resistance of a nonlinear resistor in a small current range is proportional to the number of grain boundary layers of zinc oxide, that is, the particle size of zinc oxide particles. Therefore, if a difference between the resistance value near the outer peripheral surface of the nonlinear resistor and the resistance value at the central portion is caused by a grain growth promoter such as bismuth trioxide, the current flowing through the entire nonlinear resistor becomes uneven. Become.

When the current value near the outer peripheral surface of the non-linear resistor is larger than the current value at the central portion, the temperature near the outer peripheral surface of the non-linear resistor becomes higher than the temperature at the central portion. The overall temperature rises. When the temperature of the entire non-linear resistor rises, the thermal stability of the lightning arrester constituting the non-linear resistor decreases, causing a problem that the life of the arrester decreases.

The present invention has been made on the basis of the above-mentioned problem, and makes the diameter of zinc oxide particles in the entire non-linear resistor uniform so that the current flows uniformly in the entire non-linear resistor. Another object of the present invention is to provide a method of manufacturing a non-linear resistor having good thermal stability and suppressing external flashover due to lightning surge or the like.

[0014]

According to the present invention, in order to solve the above-mentioned problems, a first invention is to mix and dry zinc oxide, an additive component, and an organic binder which are main components of a nonlinear resistor. After obtaining the granulated powder, the compact obtained by molding the granulated powder into a disc shape is calcined to obtain a calcined body, and a high resistance layer material is applied to the outer peripheral surface of the calcined body and calcined. After obtaining a fired body provided with a high resistance layer on the outer peripheral surface, in a method of manufacturing a nonlinear resistor characterized by providing electrodes on both end surfaces of the fired body, the outer peripheral surface of the calcined body Is antimony trioxide, nickel oxide,
The method is characterized in that after applying a solvent made of any of silicon dioxide, the high-resistance layer material is applied.

In a second aspect based on the first aspect, antimony trioxide is added on the outer peripheral surface of the calcined body in an amount of from 0.002 to 0.
It is characterized in that the high-resistance layer material is applied after application of 02 g / cm ² .

In a third aspect based on the first aspect, nickel oxide is applied to the outer peripheral surface of the calcined body in an amount of 0.005 to 0.05.
g / cm ^{2, and then} applying the high-resistance layer material.

According to a fourth aspect, in the first aspect, silicon dioxide is added to the outer peripheral surface of the calcined body in an amount of 0.002 to 0.01.
g / cm ^{2, and then} applying the high-resistance layer material.

[0018]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The first to third embodiments of the present invention will be described below.
An embodiment will be described with reference to the drawings. In the first embodiment of the present invention, first, a process of generating a high-resistance layer material applied to the outer peripheral surface of the calcined body will be described with reference to a generation process diagram of FIG.
In FIG. 1, step S11 shows a mixed powder production step, in which zinc oxide, bismuth oxide,
Antimony oxide and silicon oxide are blended in predetermined amounts and mixed with pure water in a preliminary stirring tank for a certain period of time to obtain a mixed powder.

Step S12 shows a first pulverizing step, in which the mixed powder is pulverized to a predetermined particle size by a vibration mill or the like. The mixed powder pulverized to a predetermined particle size is sent to a drying step shown in step S13, and is conveyed by a pump to a medium-flow type drier filled with a medium, and the heat is applied by heat conduction and hot air from the heated medium. The mixed powder is dried instantaneously and continuously to obtain a dry powder, which is collected by a bag filter and stored in a temporary storage hopper.

Step S14 shows a calcining step. In this step, the dry powder stored in the storage hopper is supplied to the rotary kiln by a quantitative feeder, and calcined continuously at a predetermined temperature and residence time. To obtain a calcined powder. Then, in a second pulverization step shown in step S15, the calcined powder is conveyed to a millstone type pulverizer by a screw conveyor and pulverized to a predetermined particle size, and then the pulverized powder is mixed in a kneading step shown in step S16. And a binder and a solvent are kneaded to complete the formation of the high-resistance layer material.

Next, the manufacturing process of the non-linear resistor will be described with reference to the manufacturing process diagram shown in FIG. Step S21 shows a granulated powder generation step. In this step, zinc oxide as a main component of the non-linear resistor, a predetermined amount of additive component, and an organic binder are mixed and defoamed, and then the mixture is spray-dried or the like. Spray dry to obtain granulated powder. Then, in the forming step shown in step S22, the granulated powder is formed into a disk-shaped formed body having a diameter of 60 mm (φ60) by a die press or the like. Step S23 shows a calcining step, in which the molded body is calcined at a temperature of 700 to 1000 ° C. to obtain a calcined body.

Step S24 shows a first coating step. In this step, antimony trioxide is dissolved in an aqueous organic binder to obtain a solvent (hereinafter referred to as solvent A), and the solvent A is calcined. Apply the roller to the outer surface of the body. Thereafter, in a second coating process shown in step S25, the solvent A applied by roller to the outer peripheral surface of the calcined body is used.
The material of the high-resistance layer obtained through the generation process shown in FIG. 1 is applied by roller to the surface of the substrate, and baked at a temperature of 1000 to 1300 ° C. in the firing process shown in step S26 to form a high-resistance layer on the outer peripheral surface. Is obtained.

Step S27 shows a third coating step. In this step, a glass powder and an organic binder are mixed and adjusted to a predetermined viscosity to obtain a solvent (hereinafter referred to as solvent D). Is applied by a roller to the surface of the high resistance layer formed on the outer peripheral surface of the fired body, and is baked at a temperature of 550 to 700 ° C. in a baking step shown in step S28. Then, it is sent to the electrode forming step shown in step S29, and both end surfaces of the fired body are polished smoothly,
Electrodes are provided on both end surfaces polished to be smooth, thereby completing the manufacture of the non-linear resistor.

As described above, the non-linear resistor manufactured according to the first embodiment of the present invention is used as a sample, and the outer peripheral portion (the outer peripheral electrode 32 described later) and the central portion (the later described central electrode 33) of the sample are used. ) Were measured to determine the current density ratio.

In the above measurement, the sample was prepared by changing the amount of the solvent A applied from 0 to 1.0 g / cm ² . The electrodes formed on both end surfaces of the sample are shown in FIG.
As shown in A and B, both end surfaces 31a and 31b of the fired body 31
(Hereinafter, referred to as an outer peripheral electrode) 32 are provided in a portion of about 10 mm width from the outer peripheral portion, and an electrode is provided at a central portion of both end surfaces 31a, 31b at a certain interval from the outer peripheral electrode.
(Hereinafter, referred to as central electrode) 33 and that each provided, current value at the outer peripheral portion electrode 32 (hereinafter, referred to as the current value I ₁₎ and the current value at the center electrode 33 (hereinafter,
Referred to as the current value I ₂₎ and were each measured.

In the current density ratio, the current value I ₁ and the current value I ₂ are converted into current densities, respectively, and the current density ratio (I ₁ /
I ₂ ) was determined. The current density ratio is “1” when the current values at the outer peripheral portion and the central portion of the nonlinear resistor are both uniform. The current density ratio between the outer peripheral portion and the central portion of the nonlinear resistor is 1
0% or less (in FIG. 4, FIG. 5, and FIG.
When the current density ratio is 0.9 to 1.1), the non-linear resistor is considered to have no practical problem.

The results of the measurement are shown in the characteristic diagram of the current density ratio with respect to the coating amount of the solvent A in FIG. In order to compare with the sample manufactured using the solvent A, a non-linear resistor sample S was manufactured according to a conventional method without using the solvent A, and the sample S was manufactured.
The current value I ₁ and the current value I ₂ were measured to determine the current density ratio, and the results are shown in FIG.

In FIG. 4, the coating amount of the solvent A is 0.02
In the sample exceeding g / cm ² , the current density ratio was less than “0.9”, and the high-resistance layer was separated from the sample. Further, in the sample in which the coating amount of the solvent A was less than 0.002 g / cm ² , the current density ratio exceeded “1.1”, and the effect of the solvent A was not observed. Note that the current density ratio of the sample S manufactured by the conventional method considerably exceeded “1.1”. On the other hand, the coating amount of the solvent A is 0.002 to 0.02 g /
The current density ratio of the sample of cm ² was in the range of 0.9 to 1.1, the high resistance layer did not peel off from the sample, and the effect of the solvent A was observed.

Therefore, when forming the high-resistance layer on the outer peripheral surface of the calcined body, the solvent A made of antimony trioxide must be prepared in advance.
By applying 0.002 to 0.02 g / cm ² to the outer peripheral surface of the calcined body, the outer peripheral portion and the central portion of the non-linear resistor can be compared with the non-linear resistor produced by the conventional example. It was confirmed that the current value can be made uniform, and a non-linear resistor having high insulation properties and preventing external flash can be manufactured.

Next, a second embodiment of the present invention will be described. The same components as those in FIGS. 1, 2, and 3 are denoted by the same reference numerals, and detailed description thereof will be omitted.
First, as in the first embodiment, step S in FIG.
A calcined body is obtained from the granulated powder producing step shown in FIG. 21 through the calcining step shown in step S23.

Thereafter, in the first coating step shown in step S24, nickel oxide is used in place of antimony trioxide, and the nickel trioxide is dissolved in an aqueous organic binder to obtain a solvent (hereinafter referred to as solvent B). The solvent B is applied by a roller to the outer peripheral surface of the calcined body. Hereinafter, the second coating process shown in step S25 of FIG.
Through the electrode forming process shown in FIG. 29, the manufacture of the non-linear resistor is completed.

As described above, the non-linear resistor manufactured according to the second embodiment of the present invention is used as a sample, and the outer peripheral portion (outer peripheral electrode 32 described later) and the central portion (central electrode 33 described later) of the sample are used. ) Were measured to determine the current density ratio. In the measurement, the sample was manufactured by changing the coating amount of the solvent B to 0 to 1.0 g / cm ² , and the current value I in the outer peripheral electrode 32 was measured similarly to the measurement in the first embodiment. ₁ and the current value I _{2 at the} center electrode 33 were measured, and the current density ratio was determined.

The measurement results are shown in a current density ratio characteristic diagram with respect to the coating amount of the solvent B in FIG. In FIG.
The sample having a coating amount of more than 0.05 g / cm ² had the high resistance layer peeled off from the sample even when the current density ratio was in the range of 0.9 to 1.1. The sample having a coating amount of the solvent B of less than 0.005 g / cm ² has a current density ratio of “1.
1 ", and the effect of the solvent B was not observed. On the other hand, the coating amount of the solvent B is 0.005 to 0.05 g /
The current density ratio of the sample of cm ² was in the range of 0.9 to 1.1, the high resistance layer did not peel off from the sample, and the effect of the solvent B was observed.

Therefore, when forming the high resistance layer on the outer peripheral surface of the calcined body, the solvent B0.
By applying 005 to 0.05 g / cm ² to the outer peripheral surface of the calcined body, the current value between the outer peripheral part and the central part of the non-linear resistance body is compared with that of the non-linear resistance body manufactured by the conventional example. Was confirmed to be uniform, and it was confirmed that a non-linear resistor having high insulation properties and preventing external flashing could be manufactured.

Next, a third embodiment of the present invention will be described. The same components as those in FIGS. 1, 2, and 3 are denoted by the same reference numerals, and detailed description thereof is omitted. First, as in the first embodiment, step S2 in FIG.
A calcined body is obtained from the granulated powder producing step shown in FIG. 1 through the calcining step shown in step S23.

Thereafter, in the first coating step shown in step S24, silicon dioxide is used instead of antimony trioxide, and the silicon dioxide is dissolved in an aqueous organic binder to obtain a solvent (hereinafter referred to as solvent C). The solvent C is applied by roller to the outer peripheral surface of the calcined body. Hereinafter, FIG.
From the second coating process shown in step S25 to step S2
Through the electrode forming process shown in FIG. 9, the manufacture of the non-linear resistor is completed.

As described above, the non-linear resistor manufactured according to the third embodiment of the present invention is used as a sample, and the outer peripheral portion (the outer peripheral electrode 32 described later) and the central portion (the later described central electrode 33) of the sample are used. ) Were measured to determine the current density ratio. In the measurement, the sample was manufactured by changing the coating amount of the solvent C to 0 to 1.0 g / cm ² , and the current value I in the outer peripheral electrode 32 was measured similarly to the measurement in the first embodiment. ₁ and the current value I _{2 at the} center electrode 33 were measured, and the current density ratio was determined.

The results of the measurement are shown in the current density ratio characteristic diagram with respect to the coating amount of the solvent C in FIG. In FIG.
The current density ratio of the sample in which the coating amount of exceeds 0.01 g / cm ² was less than “0.9”, and especially the coating amount of
In the sample exceeding 02 g / cm ² , the high resistance layer was peeled off from the sample. Further, the amount of the solvent C to be applied is 0.
The sample having a current density ratio of “1.1” or less than 002 g / cm ²
And the effect of the solvent C was not observed.
On the other hand, the coating amount of the solvent C is 0.002 to 0.01 g / cm.
The current density ratio of the sample No. ² was in the range of 0.9 to 1.1, the high resistance layer did not peel off from the sample, and the effect of the solvent C was observed.

Therefore, when the high resistance layer is formed on the outer peripheral surface of the calcined body, the solvent C0.
By applying 002 to 0.01 g / cm ² to the outer peripheral surface of the calcined body, the current value between the outer peripheral portion and the central portion of the non-linear resistor was compared with that of the non-linear resistor produced by the conventional example. Was confirmed to be uniform, and it was confirmed that a non-linear resistor having high insulation properties and preventing external flashing could be manufactured.

[0040]

According to the present invention as described above, after applying a solvent made of any one of antimony trioxide, nickel oxide and silicon dioxide to the outer peripheral surface of the calcined body, applying a high-resistance layer material and firing. Then, by obtaining a fired body having a high resistance layer formed on the outer peripheral surface, the particle diameter of the entire non-linear resistor is made uniform, the current flowing through the entire non-linear resistor is made uniform, and the high resistance layer is formed. Can be prevented from peeling off from the fired body, so that the yield in the production of the non-linear resistor is improved.

Therefore, a current can be uniformly supplied to the entire non-linear resistor, the thermal stability can be improved, and a non-linear resistor in which an external flash due to a lightning surge or the like is suppressed can be obtained.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating a process of forming a high-resistance layer material of a non-linear resistor according to first to third embodiments of the present invention.

FIG. 2 is a manufacturing process diagram of a non-linear resistor according to the first to third embodiments of the present invention.

FIG. 3 is a front view and a top view of a sample according to the first to third embodiments of the present invention.

FIG. 4 is a graph showing a current density ratio characteristic with respect to a coating amount of a solvent A according to the first embodiment of the present invention.

FIG. 5 is a current density ratio characteristic diagram with respect to an applied amount of a solvent B according to a second embodiment of the present invention.

FIG. 6 is a graph showing a current density ratio characteristic with respect to an applied amount of a solvent C according to a third embodiment of the present invention.

[Explanation of symbols]

 S11: mixed powder generating step S12: first pulverizing step S13: drying step S14: calcining step S15: second pulverizing step S16: kneading step S21: granulated powder generating step S22: forming step S23: calcining step S24 ... First coating step S25 ... Second coating step S26 ... Firing step S27 ... Third coating step S28 ... Baking step S29 ... Electrode forming step 31 ... Fired bodies 31a and 31b ... End surface 32 ... Outer peripheral electrode 33 ... Center electrode

Continued on the front page (72) Inventor Noriaki Nakata 2-1-1-17 Osaki, Shinagawa-ku, Tokyo Inside Meidensha Corporation

Claims (4)

[Claims] 1. A zinc oxide which is a main component of a non-linear resistor,
After the additive component and the organic binder are mixed and dried to obtain a granulated powder, the granulated powder is formed into a disc shape, and the obtained compact is calcined to obtain a calcined body. A non-linear resistor characterized in that a high-resistance layer material is applied to the outer peripheral surface of the non-linear resistor and fired to obtain a fired body having a high-resistance layer provided on the outer peripheral surface, and electrodes are provided on both end faces of the fired body. In the manufacturing method, after applying a solvent composed of any of antimony trioxide, nickel oxide and silicon dioxide to the outer peripheral surface of the calcined body,
A method for manufacturing a non-linear resistor, comprising applying the high-resistance layer material. 2. The high-resistance layer material according to claim 1, wherein 0.002 to 0.02 g / cm ^{2 of} antimony trioxide is applied to the outer peripheral surface of the calcined body. Manufacturing method of non-linear resistor. 3. The method according to claim 1, wherein nickel oxide is applied to the outer peripheral surface of the calcined body in an amount of 0.005 to 0.05 g / cm ² , and then the high-resistance layer material is applied. Manufacturing method of linear resistor. 4. The method according to claim 1, wherein the calcined body is coated with silicon dioxide in an amount of 0.002 to 0.01 g / cm ^{2 and then} coated with the high-resistance layer material. Manufacturing method of linear resistor.