JPS6243524B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a voltage nonlinear resistor in which a ceramic tube is integrally attached to a central hollow portion.

In general, voltage nonlinear resistors (hereinafter simply referred to as elements) for lightning arresters whose main component is metal oxide, such as zinc oxide, are made of high-purity zinc oxide, ZnO, bismuth
A small amount of oxides such as Bi, cobalt Co, manganese Mn, and antimony Sb are added, mixed, granulated, and compression molded (cylindrical or disk shape), and special treatment is performed to form a high-resistance layer on the side surface of the molded product. 1000℃~ after summer
It is obtained by firing under high temperature conditions of about 1100°C or higher and 1400°C or lower. Various electrochemical reactions proceed inside the molded body during firing, and these electrochemical reactions must occur uniformly in each part. This is because it is necessary to make the electrical characteristics of each part uniform. Therefore, if the diameter, height, or thickness of the cylindrical compression molded body is small, the electrochemical reaction will proceed uniformly in each part, so no particular problem will occur. If these dimensions are large, the electrochemical reaction in the central region will proceed more slowly than in the region near the outer surface, which will cause unevenness in electrical properties and This results in a problem that an element with good physical characteristics cannot be obtained.

Conventionally, as a countermeasure to solve this problem, it has been considered to obtain an element in a ring shape or a donut shape. An element having such a shape can be obtained by forming a concentric hollow part in the center of a cylindrical compression molded body and then firing it, but when forming a hollow part in the center, Since the outer surface is also formed in the vicinity, the electrochemical reaction will proceed almost uniformly in each part.

Therefore, in order to obtain an element having a hollow portion in the center, it is necessary to form a high-resistance insulating coating not only on the outer circumferential side of the flashover prevention element but also on its inner circumferential side. The insulating film can be formed by, for example, applying an epoxy resin to the peripheral side of the element after firing, or applying an inorganic oxide to the peripheral side of the calcined compression molded body, that is, the calcined body. ) firing method is known. If formed properly, a high-low resistance insulation coating can be obtained, but the problem here is that by using the hollow part of the element and inserting the support rod into that part, multiple This is a case where the elements are pressed and fixed in a state where they are positioned in multiple stages. In this case, there is a risk that the support rod will come into contact with the formed high-resistance insulating coating, and if it does, the insulating coating will be damaged, making it impossible to prevent flashover. Furthermore, even if multiple elements can be properly positioned and fixed by pressure contact without the support rod coming into contact with the insulation coating, there is a risk that the support rod may come into contact with the insulation coating due to vibrations such as an earthquake. There is a problem that flashover cannot be prevented in the same way.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide an element in which the insulating coating formed in the central hollow portion is not damaged even when a support rod is inserted into the central hollow portion.

For this purpose, the present invention is such that a ceramic tube is attached to the central hollow portion so as to be integral with the element. In this case, there is a risk that the support rod will come into contact with the inner peripheral surface of the ceramic tube, but since the ceramic tube is interposed between the insulation coating and the support rod, damage to the insulation coating will be prevented. It is something that will be done.

The present invention will be explained below with reference to FIGS. 1 and 2. First, FIG. 1 shows a method for integrally attaching a ceramic tube to the central hollow portion of the element. The ceramic tube is used here because, considering the function of the element as a characteristic element and the atmospheric conditions in which it is placed, it must naturally have good heat resistance and good electrical insulation. Furthermore, as will be described later, it must also have sufficient mechanical strength, and a ceramic tube is suitable as one that satisfies this condition.

By the way, even if the ceramic tube is to be integrally and firmly attached to the central hollow portion of the element, the following points need to be taken into account when attaching it. That is, the ceramic tube must be tightly adhered to the insulation coating without damaging the insulation coating, and they must be able to rotate relative to each other.

In order to satisfy this condition, it is considered that the best way to attach the ceramic tube is to take advantage of the shrinkage of the calcined body during the main firing. As shown in FIG. 1, after applying inorganic oxides 2 and 3 to the outer peripheral side and inner peripheral side of the calcined compression molded body 1, main firing is performed with a ceramic tube 4 concentrically arranged in the central hollow part. This is what we do. Generally, a compression-molded body that has been pre-calcined will shrink considerably during calcination, and its inner and outer diameters will also become considerably smaller. However, taking advantage of the fact that it will also shrink slightly during final calcination, a ceramic tube is attached to the central hollow part. It is something. Outer diameter d of ceramic tube 4
When the main firing is carried out with the inner diameter D of the calcined compression molded body 1 being made slightly smaller, a desired element as shown in FIG. 2 can be obtained. In FIG. 2, numerals 5 and 6 indicate ring-shaped electrodes that were thermally sprayed after the main firing. Further, the ceramic tube 4 is set to an appropriate length, but if it protrudes from the top surface of the element after the main firing, the unnecessary portion will be cut off later.

Finally, a specific example for obtaining a device according to the present invention will be described. In this example, the composition of the element is 91% by weight of ZnO, oxides (Sb ₂ O ₃ , Bi ₂ O ₃ ,
Co ₂ O ₃ , MnO ₂ , SiO ₂ , Cr ₂ O _{3 ,} etc.) was 9% by weight. After thoroughly mixing these, apply a pressure of 250Kg/cm ² to create an outer diameter of 100mm, an inner diameter of 20mm, and a height (thickness) of 28mm.
A compression molded body of 100% was obtained. After this, the compression molded body was calcined at a temperature of 750℃ to 1000℃.
For example, when calcined at 900℃, the inner diameter changed from 20mm to 17.5mm. It was known in advance that if the calcined compression molded body obtained in this way was subjected to main firing at a temperature of 1150°C to 1400°C, its inner diameter would change to 16.3 mm. After applying an inorganic oxide to the calcined compact, an alumina tube with an outer diameter of 17 mm was placed in the hollow center of the calcined compact, and the main firing was performed, resulting in the desired element as shown in Figure 2. Got it on the street. In this case, since the outer diameter of the alumina tube does not change, the shrinkage force of the calcined compression molded body due to the main firing changes into a force that tightens and fixes the alumina tube. In this example, a tube made of alumina is used as the ceramic tube, but it is needless to say that any suitable tube can be used without being limited thereto. Furthermore, since the shrinkage rate is not uniform depending on the shape of the element, its composition, firing conditions, etc., the length and outer diameter of the ceramic tube should generally be determined appropriately.

Incidentally, the electrical characteristics of the device obtained in the above example have a nonlinear index α of 35 to 50, V/mm (current density
When the voltage is 1mA/ ^mm2 , the voltage applied per 1mm element unit length is 200V, and the discharge capacity is 200V.
It was able to withstand up to 200 kA twice (however, the current waveform was 4 x 10 μs).

As explained above, the present invention utilizes the shrinkage of the calcined compression molding itself during the main firing to attach a ceramic tube in a good condition to the central hollow part thereof. According to the present invention, the ceramic tube is attached to the element in good condition at the same time as the main firing, and the attachment is not only simple and easy, but also because the support rod is inserted through the inside of the ceramic tube. This has the effect that the insulating coating formed on the inner circumferential side of the element is protected by the ceramic tube.

[Brief explanation of the drawing]

FIG. 1 is a half-sectional view for explaining the method of attaching a ceramic tube to the central hollow portion of the device, and FIG. 2 is a cross-sectional view showing the structure of the device according to the present invention. 1'... (mainly fired) compression molded body, 2', 3'... insulation coating, 4... ceramic tube.

Claims (1)

[Claims] 1. In a donut-shaped or ring-shaped voltage nonlinear resistor that has a concentric hollow part in the center and has an insulating coating formed on the outer and inner circumferential sides, the shrinkage of the low antibody itself occurs during main firing. A voltage nonlinear resistor characterized by a structure in which a ceramic tube is attached to a hollow part by utilizing the characteristics of the voltage nonlinear resistor.