JP6853091B2 - Vacuum switch container - Google Patents

Description

Regarding ceramic structures and containers for vacuum switches.

Conventionally, as a switch that opens and closes the current supply to a high-voltage load device, a semiconductor element such as a silicon rectifier is used to prevent sparks due to current interruption and subsequent discharge short circuit to ensure sufficient electrical insulation. Is stored in a ceramic tubular container (hereinafter, this tubular container is referred to as a container), and a vacuum switch is used in which the inside of the container is depressurized. The outer peripheral surface of this container is usually covered with a coating layer made of glaze in order to suppress the adhesion of dirt by smoothing the surface and to increase the insulation withstand voltage against creeping discharge short circuit and the like. .. Patent Document 1 contains SiO ₂ ; 60 to 80% by weight, Al ₂ O ₃ ; 10 to 20% by weight, K ₂ O; 4 to 10% by weight, and Na ₂ O, MgO, CaO, Fe in the balance. A glaze containing at least one of ₂ O _{3 has been proposed.}

Further, as for a ceramic substrate glaze composition, in Patent Document _2, Si0 2; 60 to 70 _{mol%, Al} 2 0 3; _{5.1~12 mol%, B} 2 0 3; _0.5~5 mol%, It is described that CaO; 3 to 18 mol%, BaO; 1 to 15 mol%, Sr0; 0.5 to 25 mol%.

Japanese Unexamined Patent Publication No. 2001-89268 Japanese Unexamined Patent Publication No. 60-118648

When the container is required to be miniaturized and the distance between the inner wall of the container and the semiconductor element is narrowed, the electronic component such as the semiconductor element is erroneously used when the coating layer cannot sufficiently absorb high-frequency noise radio waves coming from the outside. May cause operation. Further, when moisture contained in the atmosphere is adsorbed in the coating layer, there is a problem that the insulating property is lowered.

The present disclosure has been devised in view of such circumstances, and provides a ceramic structure and a container for a vacuum switch, which are less likely to cause malfunction of electronic components and whose coating layer insulation is less likely to deteriorate. To do.

The container for a vacuum switch of the present disclosure is a container for a vacuum switch including a ceramic structure, and the ceramic structure includes a substrate made of ceramics and a coating layer located at least a part of the substrate. The coating layer contains silicon, calcium, aluminum, potassium, at least one of barium and strontium, and oxygen. In the coating layer, out of a total of 100% by mass of all the components constituting the coating layer, each content is _{60% by mass or more in terms of SiO 2 for} silicon and 12% by mass or more and 18% by mass or less in terms of CaO for calcium. , Aluminum is 10% by mass or more and 14% by mass or less in terms of _{Al 2} O _{3 , potassium is 3% by mass or more and 7% by mass or less in terms of K 2} O, barium is converted to BaO and strontium is converted to SrO, totaling 0.2% by mass. % Or more and 0.6% by mass or less.

In the vacuum switch container of the present disclosure, there is little possibility that electronic components will malfunction, and the insulating property of the coating layer is unlikely to deteriorate. As a result, the size of the vacuum switch container can be reduced. Moreover, since it is excellent in reliability, it can be used for a long period of time.

It is sectional drawing which shows an example of the schematic structure of the container for a vacuum switch of this embodiment.

The ceramic structure and the container for the vacuum switch of the present disclosure will be described with reference to the drawings.

FIG. 1 is a cross-sectional view showing an example of a schematic configuration of a vacuum switch container of the present embodiment. The vacuum switch container 20 shown in FIG. 1 includes a ceramic structure 3 having a substrate 1 made of ceramics and a coating layer 2 located at least a part of the substrate 1. The substrate 1 is formed of a tubular body having an inner peripheral surface 1a and an outer peripheral surface 1b, and the outer peripheral surface 1b is covered with a coating layer 2.

The substrate 1 is made of, for example, ceramics containing aluminum oxide, zirconium oxide, silicon carbide, silicon nitride or sialon as a main component.

The substrate 1 can have, for example, an outer diameter of 60 mm or more and 100 mm or less, an inner diameter of 50 mm or more and 80 mm or less, and a height H ₁ of 50 mm or more and 70 mm or less. Then, a tubular metal arc shield 4 is joined to the inner peripheral surface 1b via a joining layer 5 made of a brazing material.

A disk-shaped first metal plate 6 is attached to the upper side of the substrate 1, and a disk-shaped second metal plate 7 is attached to the lower side. Both the first metal plate 6 and the second metal plate 7 are made of a Fernico alloy.

A fixed electrode 8 is attached to the first metal plate 6. The fixed electrode 8 includes a fixed shaft 8a that penetrates the central portion of the first metal plate 6 and is fixed to the first metal plate 6, and a fixed side contact 8b that is connected to the tip end side of the fixed shaft 8a. .. On the other hand, the movable electrode 9 is attached to the second metal plate 7. The movable electrode 9 includes a movable shaft 9a penetrating the central portion of the second metal plate 7, and a movable side contact 9b connected to the tip end side of the movable shaft 9a. The movable electrode 9 is approached or separated from the fixed electrode 8 by a bellows-shaped metal bellows 10. With such a configuration, the movable side contact 9b comes into contact with or separates from the fixed side contact 8b. Then, when the movable side contact 9b comes into contact with the fixed side contact 8a, electricity is applied in the axial direction A of the substrate 1.

The fixed side contact 8a and the movable side contact 9b are arranged inside the arc shield 4. The arc shield 4 suppresses the adhesion of metal vapor generated from the fixed side contact 8a and the movable side contact 9b to the inner peripheral surface 1a by applying a voltage, and prevents the deterioration of the insulating property of the substrate 1. Further, the bellows 10 is covered with a bellows cover 11. The bellows cover 11 suppresses the adhesion of metal vapor to the bellows 10.

The coating layer 2 constituting the ceramic structure 3 contains silicon, calcium, aluminum, potassium, at least one of barium and strontium, and oxygen. In other words, the coating layer 2 contains at least one of an oxide of silicon, an oxide of calcium, an oxide of aluminum, an oxide of potassium, an oxide of barium and an oxide of strontium.

_{The content of the coating layer 2 is 60% by mass or more in terms of SiO 2} and 12% by mass or more and 18% by mass or less of calcium in terms of CaO, out of a total of 100% by mass of all the components constituting the coating layer 2. , Aluminum is 10% by mass or more and 14% by mass or less in terms of _{Al 2} O _{3 , potassium is 3% by mass or more and 7% by mass or less in terms of K 2} O, barium is converted to BaO and strontium is converted to SrO, totaling 0.2% by mass. % Or more 0. It is mass% or less.

In the following, silicon oxide is SiO ₂ , calcium oxide is CaO, aluminum oxide is Al ₂ O ₃ , potassium oxide is K ₂ O, barium oxide is BaO, and strontium oxide is. Described as SrO.

SiO ₂ is a component for forming the skeleton of the glaze to be the coating layer 2, and the coefficient of linear expansion is the smallest among the above oxides constituting the coating layer 2. Therefore, if _{the content of SiO 2} is too small, the weather resistance of the coating layer 2 is lowered. In addition, since the amount of oxides contained in the coating layer 2 increases, the coefficient of linear expansion of the coating layer 2 increases. The coating layer 2 constituting the ceramic structure of the present disclosure is excellent in weather resistance because silicon is 60% by mass or more in terms of _{SiO 2.} Further, the coefficient of linear expansion of the coating layer 2 can be brought close to the coefficient of linear expansion of the substrate 1 in relation to the content of other oxides.

CaO is a component that improves chemical durability (acid resistance and alkali resistance) because it restricts the movement of the alkali metal constituting the coating layer 2. However, if the CaO content is too small, the chemical durability Cannot be improved. Further, if the CaO content is too large, foreign matter due to devitrification is generated in the coating layer 2. Of the above oxides, CaO has a large coefficient of linear expansion. The coating layer 2 constituting the ceramic structure of the present disclosure has a calcium content of 12% by mass or more and 18% by mass or less in terms of CaO, so that it has chemical durability and suppresses the generation of foreign substances due to devitrification. Can be done. Further, the difference between the linear expansion coefficient of the substrate 1 and the linear expansion coefficient of the coating layer 2 can be reduced.

Al ₂ O ₃ is a component that enhances the water resistance, heat resistance, and devitrification resistance of the coating layer 2. If _{the content of Al 2} O ₃ is too small, foreign matter may be generated due to devitrification. Further, Al ₂ O ₃ can raise the softening temperature of the coating layer 2, and the surface of the coating layer 2 is roughened when brazing after forming the coating layer 2, especially when brazing under high vacuum. It is possible to prevent deterioration of the appearance due to the above and deterioration of the insulating property due to the adhesion of dirt. Further, even when brazing is not performed, when the ceramic structure 3 is used in a high temperature environment, the surface roughness of the coating layer 2 can be suppressed. Further, if _{the content of Al 2} O ₃ is too large, the chemical durability is lowered.

The coating layer 2 constituting the ceramic structure 3 of the present disclosure is excellent in water resistance, heat resistance and devitrification resistance because aluminum is 10% by mass or more and 14% by mass or less in terms of _{Al 2} O _3. In addition, it is possible to suppress the generation of foreign matter due to devitrification.

K ₂ O contributes to the smoothness of the surface of the coating layer 3 because it imparts appropriate fluidity when forming the coating layer 2. Coating layer 2 constituting the ceramic structure 3 of the present disclosure, the potassium is at most 3 mass% or more and 7% by weight K _{2 O} in terms, since the smoothness of the surface of the coating layer 2 is improved, dirt adhesion It becomes difficult to do so, and the deterioration of the insulating property can be suppressed. It also gives gloss to the surface of the coating layer 2.

BaO and SrO are components having high electromagnetic wave absorption ability. Therefore, if the amount is too small, the electromagnetic wave absorption capacity will not be high. Further, if the content is too large, foreign matter due to devitrification will be removed from the coating layer 2
Occurs within.

In the coating layer 2 constituting the ceramic structure 3 of the present disclosure, the total of barium in terms of BaO and strontium in terms of SrO is 0.2% by mass or more. When the mass is less than%, foreign matter due to devitrification is less likely to be generated in the coating layer 2, and electromagnetic waves arriving from the outside can be absorbed. Therefore, malfunctions of electronic components such as the fixed side contact 8a and the movable side contact 9b arranged inside the ceramic structure 3 are reduced.

Further, the coating layer 2 further contains sodium, and even if the content of all the components constituting the coating layer 2 in a total of 100% by mass is 0.6% by mass or more and 1.6% by mass or less in terms of _{Na 2 O.} Good. Na ₂ O imparts appropriate fluidity when forming the coating layer 2, and thus contributes to the smoothness of the surface of the coating layer 3. When sodium _{contains a content in the above range in terms of Na 2} O, the high antifouling property can suppress the adhesion of floating metal powder. In addition, it is possible to suppress a decrease in insulating property.

Further, the coating layer 2 further contains iron, and the content of all the components constituting the coating layer 2 in a total of 100% by mass is 0.1% by mass or more and 0.3% by mass or less in terms of _{Fe 2} O _3. May be good. When iron _{contains a content in the above range in terms of Fe 2} O ₃ , the impact resistance of the ceramic structure 3 can be increased.

Further, the surface of the coating layer 2 may have an arithmetic mean roughness Ra of 0.2 μm or less. Further, the coating layer 2 may have a maximum surface height Rt of 4 μm or less. When the arithmetic mean roughness Ra of the surface of the coating layer 2 is 0.2 μm or less, or the maximum cross-sectional height Rt is 4 μm or less, the contact angle of the surface of the coating layer 2 with water becomes large, so that the moisture in the air atmosphere Is less likely to be adsorbed, and a decrease in withstand voltage can be suppressed.

The arithmetic mean roughness Ra and the maximum cross-sectional height Rt of the surface of the coating layer 2 conform to JIS B 0601: 2001. For example, a stylus type surface roughness meter (manufactured by Kosaka Laboratory Co., Ltd., surface roughness) -Using a contour shape measuring machine SEF3500), the measurement length may be 10 mm, the cutoff value may be 0.8 mm, the tip radius of the stylus may be 5 μm, and the scanning speed of the stylus may be 0.5 mm / sec.

Further, the substrate 1 may have an average value of the equivalent circle diameter of the pores of 5 μm or less. When the average value of the equivalent circle diameters of the pores is within this range, the infiltration of water and gas molecules in the atmospheric atmosphere into the pores and the adsorption into the pores due to this invasion are suppressed, so that the decrease in withstand voltage is suppressed. can do.

Further, in the substrate 1, the maximum value of the equivalent circle diameter of the pores may be 14 μm or less. When the maximum value of the equivalent circle diameter of the pores is in this range, the large pores in which moisture in the atmosphere is likely to enter is reduced, so that the decrease in withstand voltage can be further suppressed.

Further, the substrate 1 may have a pore area ratio of 4.5% or less. When the area ratio of the pores is in this range, the area in which moisture in the atmospheric atmosphere infiltrates decreases, so that the decrease in withstand voltage can be further suppressed.

In the substrate 1, the average value of the distance between the centers of gravity of the adjacent pores may be 5.5 times or more the average value of the equivalent circle diameters of the pores. When the relationship between the average value of the distance between the centers of gravity of adjacent pores and the average value of the equivalent circle diameters of the pores is within this range, the distance between the adjacent pores is relatively large compared to the equivalent circle diameter of the pores. Even if the inside of the is charged with charge or exposed to high humidity, for example, an atmosphere having a humidity of 40% or more for a long time, the decrease in withstand voltage can be further suppressed.

Next, a method for measuring the average value of the equivalent circle diameter of the substrate 1, the maximum value and the area ratio of the equivalent circle diameter, and the average value of the distance between the centers of gravity of the pores will be described.

First, the substrate 1 is cut out and its cross section is polished with diamond abrasive grains. Then, after cleaning the mirror surface obtained by polishing, the mirror surface is observed with an optical microscope at a magnification of 175 times, and the area is, for example, 3.3 mm ² (horizontal length is 2.0 mm, vertical length). The range of 1.7 mm) is photographed using a CCD camera attached to an optical microscope, and image data is acquired. Using the obtained image data, particle analysis was performed using the image analysis software "A image-kun (ver2.52)" (registered trademark, manufactured by Asahi Kasei Engineering Co., Ltd.), and the average value of the equivalent circle diameter of the substrate 1 was obtained. , The maximum value of the circle equivalent diameter and the area ratio can be obtained. As the setting conditions for particle analysis, for example, the brightness is darkened, the binarization method is manual, the small figure removal area is 3 μm ² , and the noise removal filter is provided, and the markers appearing on the screen are the pores. The threshold value may be set so as to match the shape.

Further, the distance between the centers of gravity of the pores can be obtained by applying the distance method between the centers of gravity of the image analysis software using the above image data. The setting condition of the distance between the centers of gravity may be the same as the setting condition of the particle analysis.

Although the case where the ceramic structure of the present embodiment is used for the container for a vacuum switch has been described above, it may be used for applications requiring high insulation such as insulators.

Next, an example of the method for manufacturing the ceramic structure of the present embodiment will be described.

To obtain a ceramic structure whose main component is aluminum oxide, first, aluminum oxide powder, which is the main component, silicon oxide, magnesium oxide, and calcium oxide powders as sintering aids, and aluminum oxide powder, if necessary, are used. The dispersant and the binder are wet-mixed with a ball mill or a bead mill for 40 to 50 hours to prepare a slurry.

Here, the content of the silicon oxide powder in the total 100% by mass of the powder is 3.3 to 5% by mass, the content of the calcium carbonate powder is 1.3 to 2.0% by mass, and the content of the magnesium oxide powder is Is 1.7 to 2.6% by mass.

Here, a bead mill is used to obtain a substrate in which the average value of the equivalent circle diameter of the pores is 5 μm or less, the maximum value of the equivalent circle diameter of the pores is 14 μm or less, or the area ratio of the pores is 4.5% or less. , It may be adjusted by the crushing time.

Further, in order to obtain a substrate in which the average value of the distance between the centers of gravity of the adjacent pores is 5.5 times or more the average value of the equivalent circle diameters of the pores, the amount of the dispersant added may be adjusted.

Then, the slurry is spray-dried to obtain granules whose main component is aluminum oxide. Next, the granules are filled in a predetermined molding mold, and the molding pressure is set to, for example, 80 MPa or more and 120 MPa or less, and a cylindrical molded body is obtained using a uniaxial press device.

The obtained molded product can be held at 1530 ° C. or higher and 1630 ° C. or lower to obtain a substrate made of ceramics.

Next, barium carbonate, kaolin, lime, fused silica and feldspar powders are prepared.

The ratio of each powder in the total 100% by mass of the above powders was 5% by mass or more and 9% by mass or less for barium carbonate, 10% by mass or more and 16% by mass or less for kaolin, 10% by mass or more and 16% by mass or less for lime, and molten silica. Is 27% by mass or more and 35% by mass or less, and the balance is feldspar. The barium source is barium carbonate, and the potassium sources are kaolin and feldspar.

The powder is put into a pot mill together with water and a binder, and then mixed and pulverized to obtain a paste.

A coating layer is formed by applying a paste to the outer peripheral surface of the substrate by brush coating, spray coating, etc., and heat-treating with a holding temperature of 1350 ° C. or higher and 1450 ° C. or lower and a holding time of 2 hours or more and 4 hours or less. The ceramic structure of the embodiment can be obtained.

In order to obtain a ceramic structure having an arithmetic mean roughness Ra of the surface of the coating layer of 0.2 μm or less, the pulverization time in the pot mill may be 40 hours or more and 45 hours or less.

1: Base 2: Coating layer 3: Ceramic structure 4: Arc shield 5: Bonding layer 6: First metal plate 7: Second metal plate 8: Fixed electrode 9: Movable electrode 10: Bellows ceramic structure 11: Bellows cover 20: Vacuum switch container

Claims (9)

A vacuum switch container with a ceramic structure.
The ceramic structure includes a substrate made of ceramics and a coating layer located at least a part of the substrate.
The coating layer contains silicon, calcium, aluminum, potassium, at least one of barium and strontium, and oxygen.
Of the total 100% by mass of all the components constituting the coating layer
60% by mass or more of silicon in _{terms of SiO 2}
Calcium is 12% by mass or more and 18% by mass or less in terms of CaO,
Aluminum is 10% by mass or more and 14% by mass or less in terms of _{Al 2} O _3,
Potassium or 3% by mass _{K 2} O in terms of 7 wt% or less,
A container for a vacuum switch containing 0.2% by mass or more and 0.6% by mass or less in total of barium in terms of BaO and strontium in terms of SrO. The coating layer further comprises a sodium content in the total 100 mass% of all the components constituting the coating layer is not more than 1.6 mass% to 0.6 mass% in terms of Na 2 _O, claim 1 The container for the vacuum switch described in. The coating layer further contains iron, and the content of all the components constituting the coating layer in a total of 100% by mass is 0.1% by mass or more and 0.3% by mass or less in terms of _{Fe 2} O _3. 1 or the container for a vacuum switch according to claim 2. The vacuum switch container according to any one of claims 1 to 3, wherein the coating layer has an arithmetic mean roughness Ra of the surface of 0.2 μm or less. The vacuum switch container according to any one of claims 1 to 4, wherein the substrate has an average value of the equivalent circle diameter of pores of 5 μm or less. The vacuum switch container according to any one of claims 1 to 5, wherein the substrate has a maximum value of the equivalent circle diameter of the pores of 14 μm or less. The vacuum switch container according to any one of claims 1 to 6, wherein the substrate has a pore area ratio of 4.5% or less. The vacuum switch container according to any one of claims 1 to 7, wherein the average value of the distance between the centers of gravity of the adjacent pores is 5.5 times or more the average value of the equivalent circle diameters of the pores. .. The container for a vacuum switch according to any one of claims 1 to 8, wherein the substrate is made of a tubular body having an inner peripheral surface and an outer peripheral surface, and the outer peripheral surface is covered with the coating layer.

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