JPH07263203A - Production of voltage nonlinear resistor - Google Patents

Abstract

PURPOSE:To enhance the discharge withstanding characteristics of a ZnO element by improving the conditions for coating the side face of the element with an insulating material of low melting point glass thereby making uniform the thickness of coating. CONSTITUTION:After mixing principal components of a low melting point glass at a specified ratio, polyvinylalcohol or methyl cellulose is admixed as an organic binder. A spray material is conditioned to have a viscosity of 50-200 (cP) using pure water as a solvent and then sprayed toward the side face of a fired ZnO element mounted on a rotating base thus producing a voltage nonlinear resistor. In practice, the sintered element is preheated at 50-200 deg.C and the base is rotated at 30-90r.p.m.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention mainly relates to a method of manufacturing a voltage non-linear resistor incorporated in a zinc oxide type arrester.

[0002]

2. Description of the Related Art A voltage non-linear type resistor whose main component is zinc oxide (hereinafter abbreviated as ZnO) is bismuth oxide (Bi ₂ O ₃ ) or antimony oxide (Sb) as an additive component to ZnO.
₂ O ₃ ), cobalt oxide (Co ₂ O ₃ ), chromium oxide (Cr
₂ O ₃ ), silicon oxide (SiO ₂ ), manganese oxide (Mn
O ₂ ), nickel oxide (NiO), and other metal oxides are pulverized to obtain a composition composition having high non-linearity and small heat loss.

Usually, these auxiliary additives are fluidized by being preliminarily ground with ZnO in a ball mill or the like, mixed with an organic binder solution such as polyvinyl alcohol (PVA), and spray-dried with a spray dryer. Highly granulated powder is used as a raw material, and the raw material is molded into a substantially cylindrical shape by a mold press and degreased, followed by firing at 1000 to 1300 ° C. for several hours. Then, a low-melting-point glass-based side surface insulating paste is applied to the obtained ZnO element, baked and fixed, both surfaces are sufficiently polished, and then an electrode metal such as aluminum is sprayed to manufacture. When the above ZnO element is incorporated in a lightning arrester, the above-mentioned many ZnO elements are fixed by using a support plate or a spring in the presence of an insulating support rod, and the periphery is surrounded by an insulating porcelain tube to complete the process. .

The ZnO element has a large volume and a large diameter size because it has a high voltage non-linearity, a composition composition with a small heat loss, and a large energy that can be absorbed as compared with a general surge absorber for weak electricity. is necessary. The aluminum electrode has a role of a surge energy collector in the large-diameter sintered body.

[0005]

DISCLOSURE OF THE INVENTION The conventional ZnO described above is used.
It is known that, when a low-melting-point glass-based side surface insulating paste is applied to the obtained ZnO fired body in the device manufacturing process, the discharge resistance of the device significantly changes depending on the applied amount. However, there is a problem that the discharge withstand voltage may vary greatly due to the fact that the discharge resistance is not perfect.

Possible causes for this are as follows. That is, a roll coater is usually used as a method for applying the insulating material to the side surface of the element, but at this time, it is necessary to make the insulating material into a paste in advance and then add the binder and the organic solvent. Therefore, in this method, the solvent gradually evaporates during the application of the insulating paste, and the viscosity and the concentration become higher in the middle of the work and immediately before the completion compared with the state when the application of the insulating paste was started. Cheap.

That is, when a roll coater is used to apply the insulating paste, the amount of binder to be added and the adjustment of the viscosity of the paste must be well controlled in order to keep the thickness of the applied insulating layer constant. , Especially when using a roll coating machine, it is difficult to maintain the coating thickness of the paste constant over the entire surface, and even if viewed physically, the coating height cannot be made uniform over the entire surface. .

Therefore, in general, an operator regularly adds an organic solvent to the paste and agitates the paste to cope with the change in the viscosity and the concentration. The operation of keeping the temperature constant requires advanced control technology, and since the specific gravity of the coating material is large, solid-liquid separation phenomenon may occur in the roll coating machine. It is difficult to completely eliminate. Therefore, the planar properties after coating are not uniform, and it becomes difficult to maintain high stability of the electrical characteristics such as the discharge withstand capability of the ZnO element described above.

Since the above organic solvent has high flammability and is harmful to the human body when it inhales gas, special caution is required in handling.

The present invention solves the problems that occur during the manufacturing process of such a conventional voltage non-linear resistor mainly composed of ZnO elements, and improves the material and coating conditions of the side surface insulating material to improve the insulation material. It is an object of the present invention to provide a method for manufacturing a voltage non-linear resistor, which is capable of eliminating variations in discharge withstand capability of devices obtained with uniform thickness and achieving uniform quality.

[0011]

In order to achieve the above object, the present invention is a slurry obtained by adding a pulverized product of a metal oxide as a secondary additive component to zinc oxide and mixing it with an organic binder solution. Fill the slurry tank with the above raw materials, send the above raw materials to the spray dryer and spray dry, measure a certain amount of the obtained high fluidity granulated powder, mold with a mold press, degrease Manufacturing a voltage non-linear resistance element in which a low melting point glass-based insulating paste is applied to the side surface of the obtained ZnO element and baked and fixed to obtain a resistance element. In the method, the main components of the low melting point glass are mixed at a predetermined mixing ratio, polyvinyl alcohol or methyl cellulose is added as an organic binder, and pure water is used as a solvent to have a viscosity of 50 to 200. The spray material is adjusted so as to be cP), the fired body obtained in the manufacturing process is placed on a rotating table, and then the spray material is sprayed and attached to the side surface of the fired body. There is provided a method of manufacturing a voltage non-linear resistance element.

In practice, the fired body is preheated to 50 to 200 ° C. before spraying the spray material, and the rotation speed of the table on which the fired body is placed is set to 30 to 90 (rpm).

As the sub-addition component, any one of metal oxides of bismuth oxide, antimony oxide, cobalt oxide, chromium oxide, manganese oxide, silicon oxide and nickel oxide,
Alternatively, a mixture is used.

[0014]

According to the method of manufacturing such a voltage non-linear resistor, since the solvent of the low melting point glass forming the side surface insulating material is water-based, the viscosity is kept constant and the temperature is less affected by the ambient temperature. Moreover, since the spray material is sprayed and attached to the side surface of the fired body by using the spray method, the application amount can be controlled only by controlling the spraying time, and the effect of eliminating the variation in the application thickness can be obtained.

As a coating condition for further coating, the preheating temperature of the fired body before spraying the spray material is 50 to 200 ° C.,
The rotation speed of the table on which the fired body is placed is 30 to 90 (rp
By setting m), the coating thickness of the insulating material becomes uniform, and the discharge withstand voltage characteristic of the obtained device is improved.

[0016]

EXAMPLES Specific examples of a method of manufacturing a voltage non-linear resistor according to the present invention will be described below. In the present embodiment, in the manufacturing process of the ZnO element described above, by improving the application conditions when applying the low-melting-point glass-based side surface insulating paste to the obtained ZnO element, the application thickness of the insulating material is made uniform and It is characterized in that the discharge withstand characteristic of the obtained device is improved.

Specific examples will be described below. First, in a binder solution prepared by dissolving a predetermined amount of polyvinyl alcohol (PVA) as a binder and cation MA as a dispersant, ZnO as a main raw material and bismuth oxide, antimony oxide, cobalt oxide, chromium oxide as auxiliary additives, respectively, Add and pulverize mixed metal oxides such as silicon oxide, manganese oxide, nickel oxide, etc., emulsify and mix with a disper mill, sufficiently defoam the resulting raw material slurry, and then spray using a spray dryer. It was dried to obtain granulated powder having good fluidity.

Next, a predetermined amount of the above-mentioned granulated powder was weighed based on an automatic system, and molding was performed with a press die. At this time, the outer shape of the molded body is φ40-t40, and the molding pressure is 3
It was set to 50 (kgf / cm ² ). The obtained molded body is 70
Calcination was performed at 0 to 1000 ° C. for about 2 hours.

In parallel with the above, a spray material for forming a side surface insulating material was prepared. This spray material is a main component of low melting point glass, for example, zinc oxide, bismuth oxide,
Antimony oxide and silicon dioxide are mixed in a predetermined mixing ratio, and polyvinyl alcohol (PV
Various spray materials were prepared by adding A) or methylcellulose and then adding pure water as a solvent so that the viscosity was 50 to 500 cP.

Next, the calcined body is preheated to 50 to 200 ° C., placed on a table rotating at 30 to 120 rpm, and then the spray material is sprayed on the side surface of the calcined body. Was sprayed. The fine droplets produced by spraying are dried and fixed at the moment of contact with the side surface of the calcined body, so that a drying step after coating is unnecessary.

The molded element thus sprayed with the spray material on the side surface is fired at 1000 to 1200 ° C. for about 10 hours, and then the insulating paste is applied again to the side surface using a roll coater or the like, and the temperature is adjusted to 550 to 700 ° C. After baking, the both end surfaces were polished and aluminum electrodes were sprayed to complete a ZnO element. And 4 for the obtained ZnO element
A discharge withstand voltage test was carried out for / 10 μs.

Table 1 shows the viscosity (cP) of the insulating paste (spray material) and the preheating temperature (° C.) of the insulating paste (spray material) when the spray method is used for coating the side surface insulating material for Samples 1 to 14, and the rotation speed (rpm) of the table. The results of the measurement of the coating thickness standard deviation and the results of the 4/10 μs discharge withstand voltage test carried out under various conditions are shown. Sample 15 shows the result of using a conventional roll coater for coating the side surface insulating material as a comparative example.

[0023]

[Table 1]

Sample 2 in Table 1 is an example of "no preheating". The coating thickness standard deviation and the results of the 4/10 μs discharge withstand voltage test were comparable to those of the other samples, but many planar irregularities were observed. The appearance is judged to be unfavorable.
The rotation speed of the table of Sample 7 was too low at 10 rpm, and the standard deviation of coating thickness and the result of 4/10 μs discharge withstand voltage test were unsatisfactory.

Sample 10 has a table rotation speed of 120 rpm.
However, the appearance became poor. Furthermore, samples 12, 13, and 14 have insulating paste viscosities of 300, 4
The result was increased to 00,500, and the operability deteriorated, and all became defective in the 4/10 μs discharge withstand voltage test. This is because if the viscosity of the insulating paste becomes too high, it becomes difficult to handle, and minute voids are generated due to thermal decomposition after baking, which causes a decrease in discharge withstand capability and a deterioration in the charging life.

From the above results, the viscosity of the insulating paste is 50.
To 200 (cP), and the preheating temperature of the calcined body is 50 to 20.
It was found that it is preferable to spray the insulating paste by a spray method while setting the temperature to 0 (° C.) and the rotation speed of the table on which the calcined body is placed to 30 to 90 (rpm).

The 4/10 μs discharge withstand voltage test adopted in this embodiment means a test current value of 5 kA from 65 kA to 80 kA.
It is the breakdown rate of the sample when it is increased in steps. An X mark broken at a test current value of 65 kA was unconditionally determined to be defective.

Therefore, in Table 1, the samples satisfying the manufacturing conditions disclosed as the present invention are "1, 3, 4, 5, 6, 8, 9, 11" as sample NO.

In this embodiment, as the spray material for forming the side surface insulating material, polyvinyl alcohol or methyl cellulose is added to the main component of the low melting point glass, and then pure water is added as the solvent. One of the features is that the organic solvent system of above has been replaced with an aqueous system. Therefore, the spray material is less likely to be affected by the ambient temperature, and the viscosity can be kept constant. Another feature is that the conventional roll coater was changed to a spray method as the method of applying the side surface insulating agent. By adopting this spray method, the application amount can be controlled only by controlling the spraying time. It is possible to eliminate variations in coating thickness.

As described above, in this embodiment, by improving the coating conditions when the low-melting-point glass-based side surface insulating paste is coated, the coating thickness of the insulating material becomes uniform, and the discharge withstand characteristic of the obtained device is improved. It

[0031]

As described in detail above, according to the method of manufacturing a voltage non-linear resistor according to the present invention, the solvent of the low melting point glass constituting the spray material as the side surface insulating material is water-based. As a result, the viscosity of the spray material hardly changes with the passage of time, the viscosity is kept constant and is hardly affected by the ambient temperature, and the spray material is applied to the side surface of the fired body. By spraying and adhering on, it is possible to obtain the effect that the variation in discharge withstand amount due to the imperfect coating method does not occur. In particular, it does not require a high-level control technique for adding an organic solvent, which is added in order to keep the viscosity constant, as in the prior art, and can make the planar properties uniform after coating.

As a coating condition for further coating, the preheating temperature of the fired body before spraying the spray material is 50 to 200 ° C.
The rotation speed of the table on which the fired body is placed is 30 to 90 (rp
By setting m), the coating thickness of the insulating material can be made uniform, and the generation of voids due to thermal decomposition after baking can be prevented, and the discharge withstand capability can be improved and the service life can be improved.

Further, the solvent of the spray material is water-based, has no flammability, and has the advantage that the human body is not adversely affected by the suction of gas and the handling is easy.

Therefore, according to the present invention, by improving the material of the side surface insulating material and the coating conditions, it is possible to eliminate the variation in the discharge withstand amount of the element obtained by making the thickness of the insulating material uniform and to make the voltage uniform in quality. A method for manufacturing a non-linear resistor can be provided.

Claims (5)

[Claims] 1. A slurried raw material obtained by adding a pulverized product of a metal oxide as a sub-addition component to zinc oxide and mixing it with an organic binder solution is filled in a slurry tank, and the raw material is spray-dried. ZnO obtained by sending in and spray-drying, weighing a certain amount of the obtained granulated powder with high fluidity, molding with a die molding press, degreasing and then firing at a predetermined temperature and time In a method of manufacturing a voltage non-linear resistor, which is obtained by applying a low-melting-point glass-based insulating paste to the side surface of an element and fixing it by baking to obtain a resistor element, a main component that constitutes the above-mentioned low-melting-point glass is mixed in a predetermined amount After mixing at a ratio, polyvinyl alcohol or methyl cellulose is added as an organic binder, and the spray material is adjusted to a viscosity of 50 to 200 (cP) using pure water as a solvent, A method for producing a voltage non-linear resistor, comprising placing the fired body obtained in the above on a rotating table, and then spraying and adhering the above-mentioned spray material on the side surface of the fired body. . 2. A fired body is prepared before the spraying of the spray material.
The method for producing a voltage nonlinear resistor according to claim 1, wherein the resistor is preheated to 200 ° C. 3. The number of rotations of the table on which the fired body is placed is 3
The method for producing a voltage non-linear resistor according to claim 1, wherein the resistance is 0 to 90 (rpm). 4. A slurried raw material obtained by adding a pulverized product of a metal oxide as a secondary additive component to zinc oxide and mixing it with an organic binder solution is filled in a slurry tank, and the raw material is spray dried. ZnO obtained by sending in and spray-drying, weighing a certain amount of the obtained granulated powder with high fluidity, molding with a die molding press, degreasing and then firing at a predetermined temperature and time In a method of manufacturing a voltage non-linear resistor, which is obtained by applying a low-melting-point glass-based insulating paste to the side surface of an element and fixing it by baking to obtain a resistor element, a main component that constitutes the above-mentioned low-melting-point glass is mixed in a predetermined amount After mixing at a ratio, polyvinyl alcohol or methyl cellulose is added as an organic binder, and the spray material is adjusted to a viscosity of 50 to 200 (cP) using pure water as a solvent, The sintered body obtained in the middle 50 to 20
A voltage non-linear resistor characterized by being preheated to 0 ° C. and placed on a table rotating at 30 to 90 (rpm), and the above spray material is sprayed and attached to the side surface of the fired body. Manufacturing method. 5. Bismuth oxide as the auxiliary additive component,
5. The method for producing a voltage non-linear resistor according to claim 1, wherein any one of metal oxides of antimony oxide, cobalt oxide, chromium oxide, manganese oxide, silicon oxide and nickel oxide or a mixture thereof is used.