JPH03147221A - Plastic mold vacuum valve - Google Patents

Abstract

PURPOSE:To prevent cracks of material due to thermal stresses and separation due to opening and closing shocks by molding under vacuum a material containing silica particles and short strand glass fibers in a high density after forming a glass cloth layer around a vacuum valve body. CONSTITUTION:A vacuum valve is constituted with a main body 1 around which a glass cloth layer is formed while applying tension, and an insulated reinforcement layer 23 formed by molding a material containing silica particles and short strand glass fibers in a high density under vacuum. This causes the plastic component in the molding material serving as matrix impregnated into the glass cloth so as to form a firm FRP layer 21. Since the glass cloth layer is formed under a tension, the cloth is attached around the valve main body 1 with a constant tightening force.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial Application Field) The present invention relates to a vacuum valve, and particularly to the structure of a resin molded vacuum valve with reinforced outer creeping insulation.

(Prior Art) FIG. 2 is a sectional view showing an example of a conventional vacuum valve. This vacuum valve 1 has openings at both ends of an insulating cylinder 2 connected to a fixed side end plate 3. A vacuum container 5 is formed by air-tightly sealing the movable end plate 4, a fixed shaft 6 is vacuum-tightly fixed to the fixed end plate 3, and a movable shaft 7 is connected to the movable end plate 4 via a bellows 8. The contact 9 can be opened and closed while maintaining the vacuum.

The vacuum valve 1 described above has the inside of the insulating cylinder 2 as a high vacuum having excellent dielectric strength against high voltages, and immediately extinguishes the arc that occurs when the contacts 9 open and close in this high vacuum, and the high voltage circuit This is to block the

In this way, the vacuum valve 1 opens and closes the contacts 9 in a high vacuum, so that the high-voltage circuit can be interrupted by extremely shortening the electrode opening/closing distance required for interruption. For this reason.

The insulating cylinder 2 houses the electrodes of the vacuum valve.

Can be made small and compact for high voltage.

However, the fact that the insulating cylinder 2 can be made small and compact means that the creepage insulation distance on the outside is shortened, and when atmospheric contaminants (air, dust, etc.) adhere to the insulating cylinder 2, the withstand voltage decreases. , external flashover is more likely to occur.

Therefore, as a means to eliminate the above-mentioned drawbacks, the vacuum container 5
It is known that an insulating jacket made of epoxy resin or the like is integrally formed on the outside of the housing by casting in consideration of contamination conditions.

However, in such a monolithic structure, since the coefficient of thermal expansion of the MM jacket and the coefficient of thermal expansion of the insulating cylinder 2 are different, cracks may occur due to generation of thermal stress, and the interface may peel off due to impact force during opening/closing operations. Such defects may occur, reducing the reliability of the product.

Therefore, as one of the structures to eliminate the above-mentioned problems such as cracks, an insulation reinforcing tube with a substantially increased outer creeping insulation length is manufactured in advance by casting using Evogishi JFM resin, etc., and this is assembled into the vacuum valve. There is something like this.

FIG. 3 is a sectional view showing an example of this configuration.

A rubber-like elastic material 1 made of polybutadiene, polyurethane, etc. is formed in the gap between the vacuum container 5 and the insulation reinforcing tube 10 to alleviate stress.

However, the rubber-like elastic body 11 has poor heat resistance, and its hardness and adhesive strength are easily affected by temperature, and the adhesive strength decreases as the temperature rises. In addition, if exposed to high temperatures for a long time, it will easily deteriorate, become hard, and increase the amount of shrinkage, so peeling is likely to occur at +jll of the vacuum container 4 and the insulation reinforcing cylinder 10.

Therefore, an object of the present invention is to provide a highly reliable resin-molded vacuum valve that is free from cracks caused by thermal stress or peeling caused by impact force during opening/closing operations, and which can reliably guarantee withstand voltage between outer electrodes. It's about doing.

[Structure of the invention]

(Means for Solving Problem 1) The present invention provides a pair of contacts that can be freely brought into and out of contact with each other inside a vacuum container formed by airtightly sealing the openings at both ends of an insulating cylinder made of a ceramic material with end plates. A casting material containing a high density of fine silica powder and short glass fibers is cast in a vacuum while applying tension and forming a glass cloth layer around the outer periphery of the vacuum valve body. It is constructed of an insulating reinforcing layer formed by molding.

(Function) Since the casting material is molded in a vacuum to form an insulating reinforcing layer, the matrix resin in the casting material is impregnated into the glass cloth, making it strong! -' The RP layer is formed, and since the glass cloth layer is formed under tension, it is attached to the outer periphery of the vacuum valve body under constant tightening force.

In addition, the resin containing fine silica powder is impregnated into the glass cloth, but the short glass fibers are not filtered through the glass cloth, so a short glass fiber layer containing many glass fibers is formed around the FRP layer, and the The expansion coefficient becomes very small.

Since these layers also act as stress relaxation layers, it is possible to prevent the insulation reinforcing layer from peeling off or cracking even when subjected to sudden thermal shock.

(Example) Hereinafter, an example of the present invention will be described with reference to the drawings. FIG. 1 is a sectional view showing an embodiment of the present invention.

As shown in the figure, the resin molded vacuum valve 20 has an insulation reinforcing layer 23 formed on the outer periphery of the vacuum valve 1 using an alumina ceramic for the insulation cylinder 2 via an FRP layer 21 and a short glass fiber layer 22. It is composed of Here, the insulation reinforcing layer 23 is formed so that its outer side has a desired creeping insulation length.

The resin mold vacuum valve 20 having the above configuration is manufactured by the following procedure. First, the vacuum valve 1 mentioned above
A glass tape having a thickness of 0.3 mm and a width of 25 nm+m is wound around the outer periphery of the glass cloth with 172 wraps while applying a tension of 3 to 4 kgf to form a glass cloth layer. The obtained vacuum valve was assembled into a mold, preheated under specified conditions, and mixed with bisphenol A epoxy resin (Epicoat 828, a product of Shell Chemical Co., Ltd.), a modified acid anhydride curing agent (produced by Hitachi Chemical Co., Ltd.) Product HN 2200) 85 parts by weight, 150 parts by weight of silica powder with an average particle size of 1.0 μm or less as an inorganic particulate filler (■Tatsumori product Glistalite 5X), short glass fiber with fiber length 30 = 150 μm (Japan) A hardening accelerator was added to a casting resin composition mixed with 250 parts by weight of milled fiber REV-7) manufactured by Sheet Glass Co., Ltd.,
Mold is performed in a vacuum of 3 Torr or less. At this time,
It is desirable to control the viscosity of the casting resin composition to 2500 cps or less, since the lower the viscosity, the easier the glass cloth will be impregnated with the resin.

Further, the vacuum holding time should be 30 minutes or more, and if possible, it is better to apply a pressure of 3 to 41 Kgf/cxl after releasing the vacuum.

After molding as described above, the mold is firstly cured under specified conditions, then released from the mold, and then secondly cured.

Since it is manufactured using the above procedure, the resin content in the casting resin is impregnated into glass cloth to form a strong l-' RP.
Form layer 21. In addition, the short glass fibers in the casting resin are not passed through the glass cloth.

FR)' A short glass fiber layer 22 containing many glass fibers is formed around the N21.

Next, the resin-molded vacuum valve 20 according to the present invention manufactured as described above and the conventional vacuum valve using the insulation reinforcing cylinder 10 and the rubber-like elastic body 11 made of polyurethane resin shown in FIG. After the thermal shock test, an impulse withstand voltage test was conducted, and the results shown in the following table were obtained.

The thermal shock test is performed as one of the reliability tests for resin molded parts, and is performed by repeatedly subjecting thermal shock to thermal shocks that occur due to the difference in thermal expansion coefficient between the insulation reinforcing layer 23 or the rubber-like elastic body 11 and the insulation cylinder 2. The purpose is to investigate the presence or absence of mutual peeling and the occurrence of cracks in the insulation reinforcing layer 23 based on the thermal stress generated.

The heat used in this invention? #The conditions for the impact test are 98-100℃
One cycle consists of immersing the sample in hot water for 1 hour, taking it out from the hot water, and immediately immersing it in cold water at 0 to 2°C for 1 hour, and repeating up to 10 cycles. Further, the vacuum valve used in the present invention has a rating of 6.9 KV and a standard impulse withstand voltage of ±85 KV or more after a thermal shock test.

As shown in the table above, the impulse withstand voltage after the thermal shock test is
In the case of a vacuum valve using the conventional insulating reinforcing cylinder 10, a flash fault occurred at the interface between the rubber-like elastic body 11 and the insulating cylinder 2. This is considered to be due to peeling occurring between the two as a result of the thermal shock test.

On the other hand, the resin molded vacuum valve according to the present invention is
Even after the thermal shock test, the specified impulse withstand voltage was sufficiently satisfied, and no peeling occurred at the interface of the insulating cylinder 2.

〔Effect of the invention〕

As explained above, according to the present invention, a glass cloth is wound around the outer periphery of a vacuum bulb body having a ceramic insulating cylinder while applying tension, and a casting material containing a large amount of inorganic fine powder and short glass fibers is formed. By molding with FRP, a strong FRP layer is formed near the insulating cylinder, and the coefficient of thermal expansion is small, so it will not peel or crack even under sudden thermal shock, and it will be able to withstand electricity such as impulse withstand voltage. A resin molded vacuum valve with excellent insulation properties can be provided.

[Brief explanation of the drawing]

Fig. 1 is a sectional view showing an embodiment of the present invention, Fig. 2 is a sectional view showing an example of a conventional vacuum valve, and Fig. 3 is a sectional view showing an example of a vacuum valve using a conventional insulation reinforcing tube. It is. ■... Vacuum valve, 3... Fixed end plate, 5... Vacuum container, 21... FRP layer, 23... Insulating reinforcement layer 2... Insulating cylinder 4... Movable end plate 9 ...Contact point 22...Glass short fiber layer

Claims (1)

[Claims] A vacuum valve has a pair of contacts that can be freely connected and separated inside a vacuum container formed by airtightly sealing the openings at both ends of an insulating cylinder made of ceramic material with end plates, and the outer periphery of the vacuum valve body. It is characterized by an insulating reinforcing layer formed by forming a glass cloth layer while applying tension, and then molding a casting material containing fine silica powder and short glass fibers in a vacuum in a vacuum. Resin molded vacuum valve.