JPH027129B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a vacuum shear breaker, and more particularly to a vacuum sheath breaker in which a vacuum container is formed of a metal cylinder and an insulating end plate that closes both ends of the cylinder in the axial direction. It is related to.

What is shown in Fig. 1 is an example of a conventional vacuum shield disconnector. In the figure, 11 is a metal cylinder made of, for example, SUS material. At both ends of the metal cylinder 11 in the axial direction, ring-shaped Auxiliary fittings 21 and 22
Insulating end plates 3a and 3b made of ceramic (for example, alumina ceramic) are provided through them to form the required vacuum vessel 1.

As shown in FIG. 2, the insulating end plates 3a and 3b are formed into a ring shape with a concave cross section, and ring-shaped convex seats 31 and 32 are provided on the outer and inner circumferential sides of one surface, respectively. , and metallized portions 33 and 34, which serve as brazing joints for the auxiliary metal fittings 21 and 22 and further for the auxiliary metal fittings 23 and 24, which will be described later, are provided on the surfaces of each of these convex seats, respectively.

A movable electrode rod 4 having an electrode 41 at its inner end is provided on one end plate 3a (lower side in the figure) so as to be movable airtightly and axially via a bellows 5. This bellows 5 is usually made of SUS material, and one end (upper side in the figure) is hermetically connected to the rod of the movable electrode rod 4, and the other end (lower side in the figure)
is the insulating end plate 3a via the ring-shaped auxiliary fitting 23.
It is joined to the inner circumferential side of the

Moreover, on the other insulating end plate 3b (upper side in the figure),
A fixed electrode rod 6 having an electrode 61 at its inner end has one end joined to the insulating end plate 3b and the other end connected to the fixed electrode rod 6.
The substantially cylindrical auxiliary fitting 24 is airtightly joined to the ring member 62 to pass through the ring member 62 in an airtight manner.

The movable and fixed electrode rods 4 and 6 are made of, for example, SUS, located on the back of the electrodes 41 and 61.
A shield 71 made of
It is provided so as to protrude in the direction b. Furthermore, auxiliary metal fittings 2
1 and 22 are each provided with a shield 72 that protrudes in the direction of the electrodes 41 and 61 and is located inside the shield 71.
1 and 72 are a pair of electrodes 41 and 6 when the
The metal vapor generated between the insulating end plates 3a and 3
This prevents the inner wall surface of b from being soiled.

The vacuum shield disconnector having the above-described configuration is temporarily assembled with a brazing material placed between each member to be joined, and in this state is heated in a vacuum furnace, for example.
It is heated and evacuated at 900°C to 1050°C, and each member is brazed and joined to form the required vacuum chamber and disconnector.

Note that metal members that can be joined to ceramic by brazing must have similar coefficients of thermal expansion, or even if there is a difference in coefficient of thermal expansion, the brazing temperature (for example, 900°C to
In order to achieve a highly durable bond, the material and shape must be able to soften at 1050° C. and be plastically deformed during bonding to absorb residual stress due to the difference in thermal expansion coefficients. For this purpose, the metal cylinder 1
1 and bellows 5 are made of SUS material, and fixed electrode rod 6
is made of rod-shaped Cu material, and since each of these members has a large difference in thermal expansion coefficient from ceramic and is difficult to deform plastically, it is not possible to directly apply solder to the insulating end plates 3a and 3b made of ceramic. It is difficult to join them together, and it is common to use auxiliary metal fittings 21, 22, 23, and 24 as described above.

And these auxiliary metal fittings 21, 22, 23, 24
When the ceramic is made of alumina ceramic, Fe-Ni-Co, which has a similar coefficient of thermal expansion,
Alternatively, Fe-Ni is used, but the brazing temperature (900℃~
The Cu material, which softens at temperatures of 1050℃), is formed into a shape that is easily plastically deformed. Just Fe−Ni−
Since Co and Fe-Ni are expensive, it is desirable to use Cu material, which is cheaper than these.

By the way, the conventional insulating end plates 3a and 3b mentioned above
In this case, the cross section consists of a ring shape with a recessed part, and a recessed part 35 (depth -t) is provided between the convex seats 31 and 32 located on the outer and inner peripheral sides thereof,
The reason for providing this concave portion is that the creepage distance is increased by the double convex seats 31 and 32, and the metallized portions 33 and 34
It has the role of electrically insulating the space between them by creating a highly insulating vacuum space.

However, when comparing the ideal vacuum creepage strength on ceramic (a state in which electrodes with rounded tips are placed facing each other at a distance l on the ceramic) as 100%, the second
It was actually measured that the dielectric strength of the insulating end plate in the shape shown in the figure was 50%.

The cause of this decrease in dielectric strength is that the existence of the recess 35 created a state in which the edges of the metallized parts 33 and 34 directly opposed each other, and that the metal sintered body was formed due to the firing performed after the metallized application. However, it has been found that fine edges are formed by this firing, and the electric field is concentrated at the opposing ends of both the metallized parts 33 and 34, which leads to dielectric breakdown. Moreover, this edge is
It was thought that it could also be removed by coating with Ni plating performed after metallization firing, but
It was found that it was not actually removed and the electric field concentration could not be alleviated.

Moreover, the above-mentioned problem is caused by the distance between flat insulating end plates 3a and 3b without unevenness as shown in FIG.
A similar phenomenon occurred between the metallized portions 33 and 34, which were provided at an interval of l ₀ .

The present invention has been made in view of the above points, and a protrusion is provided between a pair of spaced apart metallized parts located on the same insulating end plate so that the pair of metallized parts do not directly face each other in a vacuum. The purpose of this invention is to obtain a vacuum shield and disconnector which has an insulating end plate and thereby improves dielectric strength.

Next, one embodiment of the present invention will be described based on FIGS. 4 to 6.

First of all, what is shown in Fig. 4 is a vacuum shield disconnector that is an embodiment of the present invention, and items with the same reference numerals as those in Fig. 1 above are equivalent products, so details thereof will be explained below. Further explanation will be omitted.

That is, the present invention provides insulating end plates 3a, 3 constituting a vacuum vessel 1 of a vacuum shield disconnector as shown in FIG.
As shown in FIG.
A protrusion 36 of +t is provided between the metallized part 34 and the metallized part 34 located at the stepped part on the inner peripheral side, so that the pair of metallized parts 33 and 34 separated by a distance _l0 can be directly connected in a vacuum. This is to prevent them from facing each other.

FIG. 6 shows impulse withstand voltage characteristics based on changes in the shape (recess 35, protrusion 36) of a portion located between a pair of metallized portions 33, 34 separated by a constant distance l. The vertical axis shows the ratio when the ideal vacuum creeping withstand voltage on the ceramic is 100%, while the horizontal axis shows the shape between the pair of metallized parts 33 and 34. That is, on the horizontal axis, t<0 (minus value) indicates the depth of the recess 35 as shown in FIG. 2, t=0 indicates a flat plate as shown in FIG. 3, and t>0 (positive value).
indicates the height of the protrusion 36 as shown in FIG.

As is clear from Fig. 6, when t≦0, the creeping voltage is about 50% of the ideal ceramic creeping voltage, but when t>
0, that is, the protrusion 36 exists between the metallized parts 33 and 34 (in other words, the metallized parts 33 and
34 below the ceramic surface), and this protrusion 3
It can be seen that as the height of 6 increases, the withstand voltage also increases. For example, at t=1mm, it is 70% of the ideal value,
At t=3 mm, it recovers to 90%, and thereafter, even if the t value is increased, the rate of increase is small, and the increase characteristic is such that the asymptote is 100% of the ideal condition.

Furthermore, in the above description, the vacuum container 1 constituting the vacuum shield and disconnector is formed of a metal cylinder 11 with both axial ends open and both insulating end plates 3a and 3b. However, the present invention is not limited to this, and may be constructed of a cup-shaped metal container with one opening and one insulating end plate.

As is clear from the above description, in the present invention, a pair of metallized portions 33, spaced apart on insulating end plates 3a, 3b made of ceramic,
Since the protrusion 36 is provided between the insulating end plates 3a and 3b, and the insulating end plates 3a and 3b are used to constitute the vacuum shield and disconnector, the protrusion 36
A pair of metallized parts 3 separated by the presence of
3 and 34 do not directly face each other in vacuum, and the withstand voltage characteristics at the insulating end plates 3a and 3b can be significantly improved.

Therefore, in order to obtain the same level of withstand voltage characteristics as the conventional one, the distance l between the pair of metallized parts 33 and 34 can be reduced accordingly, and as a result, the insulating end plate 3
The outer diameter of a and 3b can be made small, making it an inexpensive insulating end plate 3.
a and 3b are obtained.

Also, depending on the presence of the protrusion 36, the metallized portion 3
Auxiliary metal fittings 21, 22, 2 joined to 3, 34
3 and 24, the assembly work of the vacuum shield and disconnector becomes very simple.

[Brief explanation of drawings]

Figure 1 is a cross-sectional view of the main part of a conventional vacuum shield disconnector, Figures 2 and 3 are cross-sectional views of a conventional insulated end plate, and Figure 4 is a cross-sectional view of a conventional vacuum insulation breaker.
5 and 5 are sectional views of essential parts of a vacuum insulation breaker and an insulating end plate according to an embodiment of the present invention, and FIG. 6 is a vacuum withstand voltage characteristic diagram of the conventional insulating end plate and the insulating end plate of the present invention. . 1 is a vacuum container, 11 is a metal cylinder, 3a and 3b
is an insulating end plate, 33 and 34 are metallized parts, 36
is a protrusion, 4 is a movable electrode rod, 41 and 61 are electrodes,
5 is a bellows, 6 is a fixed electrode rod.

Claims (1)

[Claims] 1. A vacuum container is formed by a metal container having at least one opening and an insulating end plate made of ceramic that closes the opening, and at least a pair of electrodes that can be freely moved toward and away from the vacuum container are provided. At least one of the pair of electrodes is formed to be movable via a bellows, and ring-shaped metallized parts are spaced apart from each other on the outer and inner circumferential sides of the insulating end plate forming the vacuum container. provided,
In the structure in which the metal container and either the electrode or the bellows are brazed to each of these metallized parts, the insulating end plate is formed into a ring shape with a convex cross section, and a stepped portion on the outer peripheral side of the convex part is formed. and a vacuum chamber disconnector, characterized in that the metallized portion is provided on the stepped portion on the inner peripheral side.