JPS627154B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a ceramic structure in which a ceramic characteristic element mainly composed of zinc oxide, which has a different coefficient of thermal expansion from that of the insulator porcelain, is fitted into a through hole of the insulator porcelain and is fixed integrally with a low melting point glass. It is something. The inside of the through-hole of the insulator porcelain is a ceramic structure in which ceramic characteristic elements mainly composed of zinc oxide, which have different coefficients of thermal expansion, are inserted. Because there is a risk of damage to one or both of them due to the difference in their thermal expansion coefficients, for example, if a ceramic characteristic element with a different thermal expansion coefficient is placed inside a porcelain cylinder for insulators with base metal fittings attached to both ends, A design in which a suitable number of ceramic characteristic elements are fitted loosely and held by pressing against a lid fixed to the base metal fitting via a spring has been adopted for equipment such as lightning arresters that may be affected by heat. In such a structure, the airtightness is insufficient, and even if a sealing member such as an O-ring is used, the sealing member deteriorates and cannot be used for a long time, but sufficient airtightness can be secured without using a sealing member, Moreover, there is a strong demand for a ceramic structure in which a ceramic characteristic element having a different coefficient of thermal expansion is fitted into a through hole of porcelain for an insulator, which is not likely to be damaged even when subjected to heat effects. The present invention was completed with the purpose of meeting the above-mentioned demands, and it is possible to insert a ceramic characteristic element containing zinc oxide as a main component into the through hole of the insulator porcelain from the open end surface of the through hole of the insulator porcelain. At least 3 mm or more of the material is fitted inside and fixed together at a temperature below the thermal deterioration temperature of the ceramic characteristic element with a low melting point glass having a coefficient of thermal expansion that is between or equal to the coefficient of thermal expansion of the insulator porcelain and the ceramic characteristic element. It is characterized by this. Hereinafter, the present invention will be described in detail using the illustrated lightning arrester as an example. Reference numeral 1 denotes a cylinder made of ordinary porcelain for insulators, and a ceramic characteristic element mainly composed of zinc oxide is provided in the inner cavity of the insulator. A ceramic characteristic element 2 whose main component is zinc oxide and which has a different coefficient of thermal expansion from that of porcelain is fitted. The ceramic characteristic element 2 is fitted inside the porcelain cylindrical body 1 for insulators to a depth of 3 mm or more beyond the open end surface 3, so that the coefficient of thermal expansion is the same as that of the ceramic characteristic element 2 and the porcelain cylindrical body 1 for insulators. It is integrally fixed to the inner surface of the porcelain cylindrical body 1 for insulators by a low melting point glass 4, preferably of B ₂ O ₃ --PbO type, which has a coefficient of thermal expansion in between.
Further, in order to fit the ceramic characteristic element 2 properly into the inner cavity of the porcelain cylinder 1 for insulators, an enlarged hole 5 extending a required length from the open end surface 3 is formed as necessary. In this structure, both the insulator porcelain cylinder 1 and the ceramic characteristic element 2 fitted therein are made of ceramic, and the low melting point glass 4 that fixes them together is also used. It belongs to ceramics in a broad sense, and since it is entirely made of inorganic material, its properties are very similar, so it can be bonded together accurately and has excellent airtightness, and it can also be used as an insulating material for all three. The ceramic characteristic element 2, which is fitted into the porcelain cylinder 1 for insulators and fixed together with low melting point glass 4, has good insulation performance due to its structure. When heating and cooling are repeated due to being located 3 mm or more inside the end face 3, the porcelain cylindrical body 1 for insulators has a different coefficient of thermal expansion from the porcelain cylindrical body 1 for insulators. and the ceramic characteristic element 2 does not crack or break. The reason for this is not completely elucidated, but it is clear from the experimental results shown in the table below.
Considering that cracks will occur from the upper end when there is no embedding, by creating a embedding structure, there will be a part at the open end of the porcelain cylinder 1 for insulators that is not involved in adhesion, so stress will not concentrate. Moreover, it is thought that this is because the parts involved in adhesion are less susceptible to sudden changes in temperature during the thermal test. Next, in order to confirm the effects of the present invention, a cylindrical body 1 made of three types of insulator porcelain each having a different coefficient of thermal expansion.
, 3 types of B ₂ O ₃ -PbO-based low melting point glasses 4, and 30mmφ diameter, 30mm long glass whose main component is zinc oxide.
Select one type of ceramic characteristic element 2 of mm, and also make sure that the end face of the ceramic characteristic element 2 that fits inside the porcelain cylinder 1 for insulator is 0 mm and 3 mm, respectively, from the open end face 3 of the porcelain cylinder 1 for insulator. , 7mm, 15mm,
An enlarged hole 5 was formed inside the porcelain cylinder 1 for insulators so that it could be fitted into the inside by 30 mm and 50 mm, and as a result of adhesion experiments using these combinations, the results were as follows.
It was confirmed that cracks did not occur only when the ceramic characteristic element 2 was fitted inside the opening end face 3. The porcelain cylindrical body 1 for insulators and the ceramic characteristic element 2 are bonded together by suspending low melting point glass powder in an organic binder, and after vacuum degassing, the ceramic characteristic element 2 and the porcelain cylindrical body 1 for insulators are bonded together. Pour into the gap to dry and volatilize the organic binder,
The glass was melted by heating in an electric furnace for 30 minutes at a temperature of 420 to 460 DEG C., below the thermal deterioration of ceramic characteristic element 2, at a temperature suitable for the work of each low melting point glass. All samples obtained in this way
A cold-heat test was performed by immersing the specimen in 90°C hot water and 20°C water alternately for 3 cycles, and the presence or absence of cracks was confirmed with the naked eye or with a stereomicroscope. The results are as follows.

【table】

[Table] In other words, when the embedding depth h of the ceramic characteristic element fitted inside the porcelain cylinder for insulators is 0 mm, the thermal expansion coefficients of the low melting point glass and the porcelain cylinder for insulators are approximated. However, as in Sample D, cracks occur in the insulator porcelain, and this type of adhesion does not necessarily yield satisfactory results. The reason for this is that the coefficient of thermal expansion of the porcelain for insulators constituting the cylinder apparently exceeds the coefficient of thermal expansion of the porcelain in the temperature range from room temperature to the solidification temperature of the low-melting point glass. The coefficient is not necessarily uniform in a partial temperature range due to the thermal expansion behavior of quartz, mullite, cristobalite, etc. in porcelain.
It is thought that this is because stress is generated inside the adhesive structure. Furthermore, even if the coefficient of thermal expansion of porcelain is uniform in the above temperature range, porcelain is usually composed of a non-equilibrium reaction system of a glass matrix and various types of crystals, so it depends on the initial firing conditions of porcelain. Since the coefficient of thermal expansion changes over time, it is practically difficult to always keep the coefficient of thermal expansion consistent with that of low-melting glass. On the other hand, as shown in the figure, in the case of the present invention in which the end of the ceramic characteristic element 2 is fitted inside the open end surface 3 of the porcelain cylinder 1 for insulators, the embedding depth h is 3, 7, 15. ,30,50mm
The results of experiments conducted for each of these were obtained as shown in the embedding depth 3, 7, 15, 30, and 50 mm columns in the table. That is, when the distance from the open end surface 3 of the porcelain insulator cylinder 1 to the end surface of the ceramic characteristic element is set to 3 mm, no cracks are observed in samples A and B. By ensuring an embedding depth h of 3 mm or more, the insulator porcelain cylinder 1, low melting point glass 4, and ceramic characteristic element 2 can be assembled.
If the difference in the coefficient of thermal expansion between the two ^and , and the embedding depth h is 7 mm.
As is clear from the above samples C and D, cracks cannot be prevented even if the coefficient of thermal expansion of the low-melting glass 4 is made equal to the coefficient of thermal expansion of the porcelain cylinder 1 for insulators or the ceramic characteristic element 2. It means that you can. In any case, the coefficient of thermal expansion of the low melting point glass 4 can be approximated to the characteristic elements of porcelain for insulators and ceramic by using a value that is between the coefficients of thermal expansion of each of the characteristic elements of porcelain for insulators and ceramic characteristic elements. It's important. In this way, by making the thermal expansion coefficient of the low melting point glass that fits the insulator porcelain and the ceramic characteristic element take a value that is between or equal to the thermal expansion coefficient of both, it is possible to prevent the ceramic structure from heating or cooling rapidly. Destruction due to thermal stress can be prevented. In other words, if the thermal expansion coefficients of insulator porcelain and ceramic characteristic elements are different, thermal stress corresponding to the difference in thermal expansion coefficient will be generated at the boundary between the two due to rapid heating and cooling, and the value will exceed the strength of the material. However, in the present invention, the coefficient of thermal expansion of the low melting point glass is set to a value that is between or equal to the coefficients of thermal expansion of both, so that the layer of low melting point glass acts as a buffer layer. As a result, the thermal stress generated between the insulator porcelain and the ceramic characteristic element can be reduced. It goes without saying that the porcelain cylinder 1 for insulators may be pleated or non-pleated. When a helium gas permeation test was carried out on the ceramic structures thus obtained, all of them had a permeation value of 4×10 ^-10 atm·cc/sec or less, and airtightness was sufficiently ensured. As is clear from the above description, the present invention is a porcelain for insulators in which a ceramic characteristic element containing zinc oxide as a main component is fitted into a through hole of the porcelain for insulators from the open end surface of the through hole. It is integrated with low-melting glass having a coefficient of thermal expansion that is between or equal to the coefficients of thermal expansion of the ceramic characteristic elements, and the opening side part, which is susceptible to sudden changes in temperature, is not involved in adhesion and is in a stress-free state. No cracks occur even when heated or cooled, and
It becomes easier to inject low-melting glass into the gap between the insulator porcelain and the ceramic characteristic element, and the space above the ceramic characteristic element becomes effective even when conducting conduction treatment on the ceramic characteristic element afterwards, resulting in high airtightness. It is widely used as a basic ceramic structure that can be widely applied to insulator devices that require long-term electrical insulation properties of the bonded parts, such as gear press lightning arresters and capacitor insulators.
It is a major contribution to the development of industry.

[Brief explanation of the drawing]

The drawing is a partially cutaway front view showing an embodiment of the present invention. 1: Porcelain cylinder for insulator, 2: Ceramic characteristic element, 3: Open end surface, 4: Low melting point glass.

Claims (1)

[Scope of Claims] 1. A ceramic characteristic element containing zinc oxide as a main component is inserted into a through-hole of the insulator porcelain at least 3 mm or more from the open end surface of the through-hole of the insulator porcelain, and the insulator porcelain is A ceramic structure characterized in that the ceramic characteristic elements are fixed together at a temperature below the thermal deterioration temperature of the ceramic characteristic elements by a low melting point glass having a thermal expansion coefficient intermediate or equal to each of the ceramic characteristic elements. 2. The ceramic structure according to claim 1, wherein the low melting point glass is a _{B2O3 -} PbO glass.