JPH0620549A - Manufacture of arc-extinguishing plate of arc extinguish chamber - Google Patents

Abstract

(57) [Abstract] [Purpose] To improve the material of the arc-extinguishing plate of a switchgear for vehicles such as contactors and circuit breakers used in vehicle equipment circuits. [Arrangement] In an arc-resistant arc-extinguishing plate that constitutes an arc-extinguishing chamber of a vehicle switchgear, the arc-extinguishing plate is made of a material with a weight composition ratio.
Mixing 80% or more of aluminum oxide and 10% or more of silica stone and pulverizing to a particle size of 10 μm or less, 2.5% to 2.
1% magnesium oxide was added as a sintering aid,
This is due to the use of ceramics that undergo high pressure sintering at temperatures between ℃ and 1600 ℃.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to improvements in the material of arc-extinguishing plates of switchgear for vehicles, such as contactors and circuit breakers, which are used especially in vehicle equipment circuits.

[0002]

2. Description of the Related Art Conventionally, an arc extinguishing chamber of a general vehicle opening / closing device is shown in FIG. FIG. 2 is a perspective view showing an example thereof. In FIG. 2, the arc-extinguishing plate 11 divided into two parts is integrated by fastening portions 11a, and blow-off pole pieces 33 are fastened by screws 33a on both side faces thereof. The blow-off coil 22 is mounted between the ends of the blow-off pole piece 33, and the contacts are opened and closed in an arc-extinguishing chamber provided in the arc-extinguishing plate 11 near the blow-off coil 22. In such a structure, the arc-extinguishing plate 11 is frequently exposed to arc heat of several thousands of degrees, and therefore arc-extinguishing plate 11 is not required to have arc resistance, thermal shock resistance, and good electric insulation. Needless to say, the vehicle equipment is required to have sufficient strength against mechanical shock in addition to water resistance. In particular, it is necessary to select a material that can withstand the wear caused by the arc generated when the contacts are opened and closed and that can effectively extinguish the arc. Asbestos cement is most often used for the arc-extinguishing plate 11 that has been conventionally used, and rarely, porcelain is sometimes used. Further, the mica-based one has a defect in arc extinguishing property and is hardly practically used at present. Asbestos cement is mainly made of asbestos fiber and kneaded with Portland cement as a binder. This is put in a mold and pressed to form various shapes, but it is considered that the one with a large amount of asbestos is of good quality.

[0003]

The asbestos-cement arc-extinguishing plate 11 normally has about 3% residual intrinsic water content,
When exposed to the arc, it has the feature of effectively extinguishing the arc by releasing residual moisture vapor. However, since it has water absorbency, when the vehicle switchgear is exposed to rain or snow, water penetrates into the arc-extinguishing plate 11 and weakens due to high temperature history due to the frequently generated arc, resulting in large wear. ,
It may be damaged during a long time, and the intended insulation function is lost. Furthermore, the inner surface of the arc-extinguishing plate 11 that is exposed to a thermal shock of several thousand degrees carbonizes relatively early and the insulation resistance of the creeping surface remarkably decreases.Therefore, it is necessary to modify the carbonized surface to restore the insulating property. It was essential.
In addition, asbestos is a harmful substance designated as a characteristic chemical substance to the human body, and therefore, there are countries that completely prohibit industrial use of asbestos, and Japan is also considering to take similar measures. Therefore, it is required to manufacture arc-extinguishing plates using safe alternative materials. On the other hand, another conventional material, porcelain, is a dense and durable fired product in which one or more elemental compounds are combined into fine particles. Normally, several types of crystalline raw material powders are mixed and molded at 1300 to 1500 ° C.
It was baked in. At this time, a part of the raw material is melted and the other crystalline parts are fused. After cooling, the molten part is vitreous. In general, balcon porcelain and cordierite porcelain may be applied to the arc-extinguishing plate 11.

The characteristic of porcelain is that it is scientifically stable,
It has high hardness and excellent dielectric strength. On the other hand, the disadvantages are that once fired, it is almost impossible to process it, and because of the shrinkage during firing (burning), complicated shapes such as arc-extinguishing plates cannot be accurately dimensioned. They are difficult to make, and because they are brittle, they tend to crack due to impact or sudden temperature changes. Since the zircon porcelain and cordierite porcelain that have been conventionally applied to arc-extinguishing plates also have the above-mentioned drawbacks,
In particular, as the arc-extinguishing plate 11 of a vehicle opening / closing device to which vibration is constantly applied, it is rarely used because it may be damaged during use. Although porcelain made by firing alumina, that is, aluminum oxide (Al ₂ O ₃ ) in porcelain has excellent insulating properties and particularly high heat resistance, the melting point of alumina is high at 2050 ° C.
Therefore, it is difficult to make it into a porcelain independently, and it is considered impossible to apply it to the arc-extinguishing plate 11 due to its limited use. The present invention was created in view of the above points,
The purpose is to eliminate the drawbacks of the prior art, to have a high mechanical strength, to prevent the arc discharge resistance from deteriorating for a long period of time, and to maintain stable arc discharge resistance with good reproducibility. A method of manufacturing an arc extinguishing plate for an arc chamber is provided.

[0005]

[Means for Solving the Problems] That is, the means for achieving the object is to use aluminum oxide having a weight composition ratio of 80% or more as a material of an arc extinguishing plate that constitutes an arc extinguishing chamber of a vehicle switchgear. 2.5% to 2.7% of magnesium oxide is added as a sintering aid to the powder which is mixed with 10% or more of silica stone and pulverized to a particle size of 10 μm or less, and a ceramic which is sintered under high pressure at a temperature of 1400 to 1600 ° C is used. There is something I did.

[0006]

The applicant noticed that the melting point of aluminum oxide was 2000 ° C. or higher, and tried various experiments to find a method of sintering aluminum oxide even if it did not melt. As a result, aluminum oxide powder having a weight composition ratio of 80% or more and silica powder having a melting point of about 1500 ° C of 10% or more are mixed,
After milling until 90% or more of the total powder amount becomes powder with a particle size of 10 μm or less, 2.5% to 2.7% magnesium oxide is added as a sintering aid, and high pressure sintering is performed at 1400 to 1600 ° C. , An arc-extinguishing plate that is smooth from the surface, has good dimensional accuracy, great mechanical strength, and excellent electrical insulation properties, but also has excellent arc conductivity with excellent thermal conductivity and reproducibility. I was able to get it. Here, the particle size represents the size of powder particles having an unspecified shape. Although aluminum oxide does not melt even under high-pressure sintering at a temperature of 1600 ° C or lower as described above, the mixed silica stone melts with the help of a melting aid, and the aluminum oxide fine powders are bonded together. Unify.

When the content of aluminum oxide having good electric insulation properties is reduced to less than 80%, the electric insulation properties are drastically deteriorated. Further, if the content of silica stone is less than 10%, the aluminum oxide fine powders cannot be sufficiently bonded and integrated with each other, so that they are not uniformly solidified. When the particle size of the powder obtained by crushing the mixture of aluminum oxide and silica stone is not 10 μm or less and the powder is coarse, various values relating to the mechanical strength are not stable and cannot be made uniform. When the content of magnesium oxide as a sintering aid to be added is less than 2.5%, the melting of the silica stone does not progress easily and the solidification cannot be expected sufficiently. 2.7%
If it exceeds the range, the amount of metal ions contained will be too much, and the insulating characteristics will suddenly deteriorate. If the temperature during high-pressure sintering is 1400 ° C or lower, the silica stone will not melt even with the aid of a sintering aid, and thus aluminum oxide will not solidify. On the contrary, when the temperature exceeds 1600 ° C, the metal ions of the sintering aid are vaporized, the normal melting of silica stone cannot be expected, and the finish after integral solidification is not precise. An embodiment of the present invention will be described in detail below with reference to the drawings.

[0008]

1 is a perspective view showing an embodiment of the present invention. In FIG. 1, a through hole 1b is provided for integrating an arc-extinguishing plate 1 formed into two parts with a fastening component 1a. The inside of the through hole 1b is provided with a pedestal.
The fastening part 1a penetrating therethrough is configured so as not to be exposed to the arc. Further, a screw hole 3b for fastening the blow-off pole piece 3 with a screw 3a is provided on the outer surface of the arc-extinguishing plate 1,
The structure is such that the position of the arc-extinguishing plate 1 and the blow-off coil 3 can be held by the fastened blow-off pole piece 3. The method for manufacturing the arc-extinguishing plate having such a structure is as follows. Aluminum oxide (Al ₂ O ₃ ) 80%, silica stone (SiO ₂ ) 11
%, Magnesium oxide (MgO) 2.6%, other calcium oxide (CaO) and other 6.4% by weight composition ratio of the new alumina ceramic material is significantly higher than the asbestos cement and zircon porcelain currently used for arc-extinguishing plate 1. In order to prove that it is an excellent material, a comparative test was performed using test pieces in accordance with JIS C2210 “electrical insulating asbestos cement board” and JIS C2141 “electrical insulating ceramic material test method”. Table 1 shows some of the test results.

[0009]

[Table 1]

Comparing the characteristic values of the currently used asbestos cement as a criterion, the conventional porcelain is excellent in electrical characteristics and water absorption, but has a small impact strength and is comparable to that of asbestos cement. As is clear from Table 1, the new material ceramic showed the best characteristics in terms of insulation performance, water absorption, mechanical performance, thermal conductivity, and the like.
In particular, the dielectric loss always becomes a problem when handling a high voltage that causes an arc, but tan δ, which influences the magnitude of the dielectric loss, was significantly improved and decreased. Also,
Since the thermal conductivity is very good, the temperature rise in the arc extinguishing chamber at the time of arcing can be reduced, the change in creeping insulation resistance can be reduced, the arc extinguishing performance can be improved, and the reproducibility is stable with good repeatability. The resulting arc resistance characteristics are obtained. The arc-quenching plate made of alumina ceramic according to the present invention is also extremely difficult to machine after firing is completed. Therefore, the through hole 1b and the screw hole 3b also need to be molded at the same time during high pressure sintering, but the dimensional accuracy can be maintained by high pressure sintering with a molding die.

[0011]

As described in detail above, according to the present invention, the asbestos-based material or the porcelain-based material used for the arc-extinguishing plate 1 is more excellent in insulation performance, water absorption rate, mechanical performance and thermal conductivity. By replacing it with alumina ceramic, it is possible to obtain an arc-extinguishing plate of a switchgear for a vehicle, which does not absorb water, does not wear, does not cause crack destruction, and has high arc-extinguishing performance. It should be noted that the high-performance arc-extinguishing plate can be produced without using asbestos as a derivative effect of the present invention.

[Brief description of drawings]

FIG. 1 is a perspective view of an example of an arc extinguishing plate to which the present invention is directed.

FIG. 2 is a perspective view of an example of an arc extinguishing chamber of a vehicle opening / closing device.

[Explanation of symbols]

 1 Arc extinguishing plate 1b Through hole 3b Screw hole 11 Arc extinguishing plate 22 Blowing coil 33 Blowing pole piece 11a Fastening part 33a Screw

Claims (1)

[Claims] 1. An arc-resistant arc-extinguishing plate that constitutes an arc-extinguishing chamber of a vehicle switchgear, wherein the arc-extinguishing plate is made of aluminum oxide of 80% or more by weight and silica stone of 10% or more by weight. 2.5 to a powder crushed to a particle size of 10 μm or less.
% -2.7% of magnesium oxide is added as a sintering aid, and a method of producing an arc-extinguishing plate for an arc-extinguishing chamber is characterized by using a ceramic which is subjected to high-pressure sintering at a temperature of 1400 ° C-1600 ° C.