JP3345495B2 - Manufacturing method of high voltage insulator - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a high voltage insulator, and more particularly to a method for manufacturing an alumina ceramic high voltage insulator capable of withstanding a high voltage.

[0002]

2. Description of the Related Art Ceramics have excellent insulation resistance and are widely used in fields such as spark plugs and insulators. In particular, insulators made of high-purity alumina ceramics are used as insulating materials in portions where a high voltage is applied.

However, when a conventional high-purity alumina ceramic insulator is to be used in an environment where a creeping discharge can be removed, such as in a vacuum or in an SF ₆ gas atmosphere,
When a high voltage is applied, there is a problem that the insulator is broken down. That is, when a DC voltage of a certain level or more is applied to the insulator, electric charges concentrate on minute pores inside the insulator, and as a result, dielectric breakdown occurs.

[0004] In order to solve this problem,
In order to withstand a high voltage, conventionally, an attempt has been made to increase the distance between the electrodes.

[0005]

However, the above-mentioned conventional solution cannot be adopted for a product which is limited in size and cannot have a sufficient distance between electrodes. When a high voltage is applied to such a product, the distance between the electrodes is short, so that there is a disadvantage that dielectric breakdown occurs. Therefore, when using alumina as an insulator for a product with a limited size, the withstand voltage must be increased so that dielectric breakdown does not occur even if the distance between the electrodes is short. there were.

The present invention has been made in view of the above-mentioned drawbacks and problems, and an object of the present invention is to provide a high-voltage insulator made of alumina ceramics with improved withstand voltage. Another object of the present invention is to provide a high-voltage insulator that can be used even for a product whose size is limited and a sufficient distance between electrodes cannot be obtained. The purpose is to provide an insulator.

[0007]

SUMMARY OF THE INVENTION The present invention is characterized in that an alumina ceramic insulator manufactured by a normal manufacturing method is heat-treated under a predetermined heat treatment condition to remove minute pores present in the ceramic. Thus, the high-voltage insulator aimed at above is provided. That is, the feature of the present invention focuses on the fact that the cause of dielectric breakdown generated when a high voltage is applied to an alumina ceramic insulator is minute pores present in the ceramic, and this ceramic is treated at high temperature and high pressure. In order to remove minute pores.

The gist of the present invention is as follows:
`` High-purity alumina ceramic sintered body, 1000 ~ 1600 ℃ under argon or nitrogen atmosphere, 10 ~ 2000 atm, 10 minutes ~
A method for manufacturing a high-voltage insulator, which is heat-treated for 10 hours. ".

Hereinafter, the present invention will be described in detail. In the present invention, the high-purity Al ₂ O ₃ ceramic sintered body to be subjected to the heat treatment contains Al ₂ O _{3 in an amount} of 90% by weight or more, and can be manufactured by the following method. .
However, the present invention is not limited to the following method.

The raw material powder has an average particle size of 0.1 to 5 μm (preferably 0.2 to 1.5 μm) and a purity of 95% or more (preferably 99%
A molded body is prepared using the above alumina powder. An arbitrary method such as press molding, CIP molding, injection molding, and cast molding can be used for producing the molded body. The obtained molded body is fired in an air atmosphere at 1200 to 1700 ° C. (preferably 1350 to 1600 ° C.) for 1 to 30 hours (preferably 5 to 20 hours) to produce an alumina sintered body.

Next, this sintered body is subjected to "heat treatment at high temperature and high pressure", which is a feature of the present invention, to obtain a desired insulator having a high withstand voltage. The heat treatment conditions are Ar or N ₂
In atmosphere, 1000-1600 ° C (preferably 1300-1500 ° C), 10
To 2000 atm (preferably 1000 to 2000 atm) for 10 minutes to 5 hours (preferably 1 to 5 hours).

In the present invention, although not particularly limited, the alumina sintered body obtained as described above is car-
Bon or magnesia crucible, average particle size 0.2-5
After filling with Al ₂ O ₃ powder of μm, it is preferable to heat-treat with, for example, a carbon heater.

The present invention relates to this "heat treatment by high temperature and high pressure".
In addition, an insulator having various withstand voltages can be obtained by appropriately selecting the conditions for the heat treatment within the above range. That is, the temperature, pressure, and processing time during the heat treatment, the higher the temperature,
The higher the pressure, and the longer the treatment time, the higher the withstand voltage tends to be.Therefore, in the present invention, the withstand voltage can be controlled by appropriately selecting the conditions during the heat treatment within the above range, Insulators having various withstand voltages can be obtained.

[0014]

The present invention focuses on the "fine pores present in the insulator" which cause insulation breakdown, and the pores can be removed by the "heat treatment by high temperature and high pressure" which is a feature of the present invention. It is possible to prevent dielectric breakdown due to the pores. Further, according to the present invention, an insulator with improved withstand voltage can be obtained by removing these minute pores, and an insulator whose withstand voltage can be easily controlled by appropriately selecting conditions for heat treatment can be obtained. Can be

[0015]

EXAMPLES Examples of the present invention subjected to a heat treatment and examples not subjected to a heat treatment (comparative examples) will be described below for comparison.

(Example) Al ₂ O ₃ powder (manufactured by Daimei Chemical Co., Ltd .: purity)
99.99%) 100 parts by weight of polyvinyl alcohol (PVA)
5 parts by weight and 100 parts by weight of ion-exchanged water were added and mixed in a mill for 24 hours to prepare a raw material slurry, and this raw material slurry was dried by a spray dryer to produce alumina granules. .

The size (φ14 m) shown in FIG.
m, φ20 mm × φ40 mm × 50 mm) was molded using the CIP molding method. The temperature of the molded body 1 was raised to 1350 ° C. at a rate of 100 ° C./min in the air, and the temperature was maintained for 3 hours.
The temperature was lowered at a rate of 0 ° C./min to obtain an alumina sintered body.

Next, this alumina sintered body is placed in a carbon crucible.
(Carbon crucible coated with boron nitride on its inner surface), and sufficiently filled with alumina powder having an average particle size of 1.0 μm (purity: 99.9%, manufactured by Showa Denko KK). In a furnace at room temperature in an atmosphere filled with argon at a pressure of 600 kg / cm ² at a temperature rising rate of 200 ° C./min.
After holding at 1800 ° C. and 1800 atm for 5 hours, the temperature was lowered at a rate of 100 ° C./min.

With respect to the alumina insulator thus treated at high temperature and high pressure, a metallized layer was formed on portions A and B in FIG. 2 by a molybdenum manganese method, and Ni plating was applied. Subsequently, the metal fitting 3 for fixing the electrode was brazed to the part A, and the outer tube 4 made of Kovar was brazed to the part B with an Ag-Cu braze to produce the alumina insulator 2 shown in FIG.

The alumina insulator 5 thus obtained
DC voltages of 50 kV, 100 kV, and 150 kV were respectively applied to the test pieces, and no breakage occurred when any of the voltages was applied or after holding for 1 minute.

(Comparative Example) The same raw material slurry as in the example was prepared and dried by a spray dryer in which the outlet temperature of the slurry was set at 120 ° C. to produce alumina granules. Using these berries, an alumina molded body 1 having the same shape as that of the example and having the size (φ14 mm, φ20 mm × φ40 mm × 50 mm) shown in FIG. 1 was formed by the same CIP molding method.

Next, an alumina sintered body was obtained from this compact under the same conditions as in the example. The electrode fixing bracket 3 and the outer cover 4 made of Kovar are brazed to the alumina sintered body in the same manner as the alumina insulator 2 of the embodiment, and the alumina insulator 2 shown in FIG. An insulator 2) not subjected to the above was produced. When a voltage of 100 kV was applied to the insulator 2, the alumina was broken.

When comparing the embodiment of the present invention with the comparative example,
In the insulator of the heat-treated example, the DC voltage of 50 kV, 100 kV, and 150 kV were applied, respectively, and they did not break even after holding for 1 minute. In the insulator, the alumina was broken when a voltage of 100 kV was applied. It is apparent from the comparison between the two that a significant difference in effect occurs depending on the presence or absence of the heat treatment.

[0024]

As described in detail above, the present invention is characterized in that an alumina sintered body produced by a normal production method is heat-treated under a predetermined heat treatment condition. There is an effect that a high voltage insulator having a higher withstand voltage can be obtained as compared with the alumina insulator. According to the present invention, it is possible to provide a high-voltage insulator that can be used even for a product whose size is limited and a sufficient distance between electrodes cannot be obtained, and that conditions for heat treatment are appropriately selected. Thereby, an effect is obtained that an insulator whose withstand voltage is easily controlled can be obtained.

[Brief description of the drawings]

FIG. 1 is a view for explaining one embodiment of the present invention, and is a half sectional view of an alumina molded body.

FIG. 2 is a diagram showing a heat treatment of an alumina sintered body obtained by firing the alumina molded body of FIG. 1 to form a metallized layer on portions A and B of an alumina insulator, followed by Ni-plating alumina The half sectional view of an insulator.

FIG. 3 is a half sectional view of an alumina insulator obtained by brazing an electrode fixing bracket and an outer tube made of Kovar to portions A and B of FIG. 2;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Alumina molded object 2 Alumina insulator 3 Metal fitting for electrode fixing 4 Outer tube

──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Shigeru Takahashi 6-25-27 Kashiwacho, Shiki-shi, Saitama (72) Inventor Chitose Yamagishi 2-17-4 Ogikubo, Suginami-ku, Tokyo (56) References 7-101771 (JP, A) JP-A-5-286753 (JP, A) JP-A-1-212272 (JP, A) JP-A-55-109270 (JP, A) JP-A-5-327146 (JP, A A) (58) Field surveyed (Int. Cl. ⁷ , DB name) C04B 35/10-35/119 C04B 35/64-35/645 H01B 3/12 H01T 13/38

Claims (2)

(57) [Claims] 1. A high-purity alumina ceramic sintered body,
A method for producing a high-voltage insulator, comprising heat-treating at 1000 to 1600 ° C. and 10 to 2000 atm for 10 minutes to 10 hours in an argon or nitrogen atmosphere. 2. The method for manufacturing a high-voltage insulator according to claim 1, wherein the high-purity alumina ceramic sintered body is filled with alumina powder having an average particle size of 0.2 to 5 μm and then heat-treated.