JP2010073460A - Vacuum bulb - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a vacuum bulb using a vacuum insulated container which hardly charges and of which the surface dielectric strength can be improved. <P>SOLUTION: The vacuum bulb is provided with a vacuum insulated container 1 made of ceramic, sealing fittings 2, 3 which are respectively sealed at the both end apertures of the vacuum insulated container 1, a pair of contactable and separable contacts 5, 6 housed in the vacuum insulated container 1, and a first resistance layer 11 which is installed on the inner face of the vacuum insulated container 1 and has a resistivity smaller than ceramic. A concavo-convex part 10 is provided on the inner face of the vacuum insulated container 1, and the resistance layer 11 has also concavo-convex shape. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a vacuum valve having a pair of contactable and separable contacts, and more particularly to a vacuum valve that can improve creeping dielectric strength in a vacuum.

2. Description of the Related Art Conventionally, vacuum valves that house a pair of contactable contacts in a vacuum insulating container have been reduced in size due to the excellent dielectric strength and arc extinguishing properties of the vacuum. Ceramics such as alumina porcelain having excellent electrical characteristics such as mechanical characteristics and insulation resistance are used for the vacuum insulating container (see, for example, Patent Document 1).
JP 2004-319151 A (page 3, FIG. 1)

The above-described conventional vacuum valve has the following problems. Although the resistivity of the vacuum insulation container is as high as about 10 ¹⁵ Ω · cm at a temperature of 25 ° C. and exhibits an excellent insulation resistance, electrons emitted from a portion having a high electric field strength such as an arc shield end due to an insulation resistance is too high. May be trapped and charged.

  When charging occurs, the electric field distribution in the vacuum bulb is disturbed, leading to a decrease in dielectric strength. In particular, on the inner surface of the vacuum insulating container, the creeping dielectric strength is reduced, which may cause penetration failure. For this reason, it has been desired to reduce the resistivity to such an extent that it does not affect the operation and to increase the creeping insulation distance so that it is difficult to cause charging and can improve the creeping dielectric strength.

  The present invention has been made to solve the above-described problems, and an object of the present invention is to provide a vacuum valve using a vacuum insulating container that is difficult to be charged and has a creeping insulation distance increased.

  In order to achieve the above object, a vacuum valve according to the present invention is housed in a vacuum insulating container made of ceramics, a sealing metal fitting sealed at both ends of the vacuum insulating container, and the vacuum insulating container. And a pair of contact points that can be contacted and separated, and a resistance layer having a resistivity lower than that of the ceramic provided on the inner surface of the vacuum insulating container, and a convex recess is provided on the inner surface of the vacuum insulating container. .

  According to the present invention, a resistance layer having a resistivity lower than that of ceramics is provided on the inner surface of the vacuum insulating container, and the inner surface is uneven, so that the charging phenomenon hardly occurs, the creeping insulation distance increases, Creeping dielectric strength can be improved.

  Embodiments of the present invention will be described below with reference to the drawings.

  First, a vacuum valve according to Embodiment 1 of the present invention will be described with reference to FIG. FIG. 1 is a cross-sectional view illustrating a configuration of a vacuum valve according to Embodiment 1 of the present invention.

  As shown in FIG. 1, a fixed-side sealing metal fitting 2 and a movable-side sealing metal fitting 3 are sealed at both end openings of a cylindrical vacuum insulating container 1 made of ceramics such as alumina porcelain. A fixed-side energizing shaft 4 is fixed through the fixed-side sealing fitting 2, and a fixed-side contact 5 is fixed to an end in the vacuum insulating container 1.

  A movable contact 6 that can be moved toward and away from the fixed contact 5 is fixed to the end of the movable energizing shaft 7 that movably penetrates the opening of the movable seal 3. Between the middle part of the movable-side energizing shaft 7 and the movable-side sealing metal fitting 3, both ends of a telescopic cylindrical bellows 8 are sealed. Thereby, the movable energizing shaft 7 can be moved in the axial direction while maintaining the vacuum in the vacuum insulating container 1. A cylindrical arc shield 9 is fixed to the intermediate portion of the vacuum insulating container 1 so as to surround both the contacts 5 and 6.

  The inner surface of the vacuum insulating container 1 is provided with a convex concave portion 10 in which crests and troughs are randomly formed by, for example, sandblasting. The height of the peak is several tens to several hundreds of micrometers. Further, an amorphous resistance layer 11 made of a hydrocarbon or carbon allotrope is provided on the surface of the convex / concave portion 10 over the entire area from the fixed-side sealing fitting 2 to the movable-side sealing fitting 3. ing. The resistance layer 11 has a thickness of several tens of nanometers to several μm, and the surface shape of the resistive layer 11 is uneven as well.

The resistance layer 11 is made of so-called diamond-like carbon, and can be provided by, for example, a plasma CVD method in which a hydrocarbon gas such as acetylene is turned into plasma and hydrocarbon is deposited on the inner surface of the vacuum insulating container 1. And after vapor deposition, the resistivity can be changed to 10 ⁸ to 10 ¹⁴ Ω · cm by controlling the temperature for heat treatment. If the temperature of the heat treatment is increased, the randomly arranged carbon atoms are regularly arranged, and the resistivity is reduced.

As a result, the inner surface of the vacuum insulating container 1 can be controlled to have a resistivity of about 10 ¹⁵ Ω · cm, which is smaller than that of high-resistance ceramics. For this reason, charging tends to occur in the portion where the electric field strength is high facing the end of the arc shield 9 or the like, but since the resistivity of the resistance layer 11 is small, the electric charge is on the fixed side sealing fitting 2 side or the movable side sealing side. Move to the fitting 3 side in a short time. That is, it becomes difficult to be charged. Further, the random convex and concave portions 10 can increase the creeping insulation distance and improve the creeping dielectric strength.

Note that if the resistivity of the resistance layer 11 is less than 10 ⁸ Ω · cm, the leakage current increases, and if it exceeds 10 ¹⁴ Ω · cm, it is difficult to move charges in a short time, which is not preferable.

  According to the vacuum valve of the first embodiment, since the resistance layer 11 having a resistivity smaller than that of ceramics is provided on the inner surface of the vacuum insulating container 1 and the surface is uneven, the charge to be trapped is short. It moves to the sealing metal fittings 2 and 3 side with time, charging becomes difficult to occur, the creeping insulation distance is increased, and the creeping dielectric strength in vacuum can be improved.

  In the first embodiment, the resistance layer 11 is described as an amorphous hard film made of an allotrope of carbon. However, a metal oxide layer obtained by evaporating copper oxide or the like, or an oxide such as magnesium oxide or sodium oxide on silicon dioxide. Even if an oxide glass layer to which is added is provided, the resistivity becomes smaller than that of ceramics, and the charging phenomenon can be suppressed.

  Further, when the vacuum insulating container 1 is manufactured by heat treatment, it is in an unglazed state, and its inner surface is somewhat uneven. For this reason, it is not necessary to perform the sandblasting process if the size of the unevenness is larger than the film thickness of the resistance layer 11 and the portion recessed in the recess is not buried by the film thickness of the resistance layer 11.

  Next, a vacuum valve according to Embodiment 2 of the present invention will be described with reference to FIG. FIG. 2 is an enlarged half sectional view of a main part showing the configuration of the vacuum valve according to the second embodiment of the present invention. The difference between the second embodiment and the first embodiment is that the inner surface of the vacuum insulating container is an annular convex recess. In FIG. 2, the same components as those in the first embodiment are denoted by the same reference numerals, and detailed description thereof is omitted.

  As shown in FIG. 2, a plurality of convex and concave portions 12 having annular crests and troughs are provided on the inner surface of the vacuum insulating container 1 by machining. The height of the peak is several tens to several hundreds of micrometers. A resistance layer 13 having a resistivity lower than that of ceramics similar to that of the first embodiment is provided on the surface of the convex and concave portion 12. The convex recess 12 and the resistance layer 13 are provided over the entire area from the fixed side to the movable side. In addition, you may provide the convex concave part formed at random like Example 1 in the surface of the convex concave part 12. FIG.

  According to the vacuum valve of the second embodiment, in addition to the effect of the first embodiment, the diffusion of the metal vapor released from the contact 5 at the convex recess 12 can be suppressed. Further, the creeping insulation distance can be increased reliably.

  Next, a vacuum valve according to Embodiment 3 of the present invention will be described with reference to FIG. FIG. 3 is an enlarged half sectional view of the main part showing the configuration of the vacuum valve according to Embodiment 3 of the present invention. The third embodiment is different from the second embodiment in that the convex and concave portions are formed in a spiral shape. In FIG. 3, the same components as those in the second embodiment are denoted by the same reference numerals, and detailed description thereof is omitted.

  As shown in FIG. 3, the inner surface of the vacuum insulating container 1 is provided with a convex recess 14 having spiral peaks and valleys. A resistance layer 15 having a resistivity lower than that of ceramics similar to that of the first embodiment is provided on the surface of the convex recess 14. The convex recesses 14 and the resistance layer 15 are provided over the entire area from the fixed side to the movable side. In addition, you may provide the convex concave part formed in the convex concave part 14 like Example 1 at random.

  According to the vacuum valve of the third embodiment, the same effect as that of the second embodiment can be obtained.

Sectional drawing which shows the structure of the vacuum valve which concerns on Example 1 of this invention. The principal part expanded half sectional view which shows the structure of the vacuum valve which concerns on Example 2 of this invention. The principal part expanded half sectional view which shows the structure of the vacuum valve which concerns on Example 3 of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Vacuum insulating container 2 Fixed side sealing metal fitting 3 Movable side sealing metal fitting 4 Fixed side energizing shaft 5 Fixed side contact 6 Movable side contact 7 Movable side energizing shaft 8 Bellows 9 Arc shields 10, 12, 14 Convex recesses 11, 13, 15 Resistance layer

Claims (5)

A vacuum insulating container made of ceramics;
Sealing metal fittings sealed at both ends of the vacuum insulating container, and
A pair of detachable contacts housed in the vacuum insulating container;
A resistance layer having a resistivity lower than that of the ceramic provided on the inner surface of the vacuum insulating container,
A vacuum valve characterized in that a convex recess is provided on the inner surface of the vacuum insulating container.   2. The vacuum valve according to claim 1, wherein the convex concave portion has a crest and a trough formed at random.   The vacuum valve according to claim 1, wherein the convex recess is formed in an annular shape.   The vacuum valve according to claim 1, wherein the convex concave portion is formed in a spiral shape.   The vacuum valve according to any one of claims 1 to 4, wherein the resistance layer is made of an amorphous material made of an allotrope of hydrocarbon or carbon.

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