JPS6074213A - Vacuum valve - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed description of the invention] [Technical field of invention] The present invention relates to vacuum valves.

[Technical background of the invention and its problems]

Conventional vacuum valves have VC insulation (1a) as shown in Figure 1.
An insulating container 10 consisting of two V'Cs arranged in parallel in the axial direction is provided with end plates 2 and 3 at both ends, respectively, to form a vacuum container whose interior is evacuated. The identification pole 4 is connected to the current-carrying shaft 4a that passes through the end plate 2 in an airtight manner. Electrode zlc with η feeler 4)]
has been established. Further, a movable pole 5-: a movable pole 5C is provided on the end plate 3 via a bellows 6, and has a contactor 5b on a current-carrying shaft 5a which is movably sealed. Then, place the arc 7 in the middle of the vacuum vessel (the arc 7) on the fixed pole side.
A shield 8 is provided on the movable side, and a holder 7 is provided on the movable side.

Such a 7/l/door 8 plays a major role in preventing the metal vapor emitted between the electrodes 4 and 5 from landing on the inner wall PC when the current is cut off. There is C. However, since the flange/rud 7 and the arc shield 8 are located close to each other, the fracture foot pressure is reduced. Considering the movable side as shown in Fig. 2, when an electric field is applied to the arc shield 8, the flange mold 7 on the movable side becomes a cathode and the emitted electrons e are collides with and releases secondary electrons. The relationship between the collision energy and the secondary electron emission efficiency δ(E) at this time is 1! '? The characteristic curve δ(E) is not shown in 31N.

In FIG. 3, the vertical axis shows the secondary electron emission efficiency δ(E), and the horizontal axis shows the electron pre-collision energy E (eV). This curve δ(E)K Therefore, positive charges are accumulated in the insulating cylinder 1a. The electrons emitted from the insulating tube]a multiply by a secondary electron avalanche, and eventually lead to dielectric breakdown. Therefore, a precursor breakdown current due to electron avalanche flows at a relatively low voltage, and as a result, the breakdown voltage becomes low [2
Mau. On the other hand, in recent years, circuits using vacuum valves have become increasingly high +1L, and there is a desire for a vacuum valve that can be used stably at high voltage.

Therefore, as a method to eliminate the above-mentioned drawbacks, it has been considered to coat the surfaces of the arc 7-rule 8 and the flange shield door with an insulating material such as alumina or epoxy resin. This can suppress the emission of field emission electrons from either of the shields serving as the cathode, so it is possible to suppress the primary radiation incident on the insulating tube. Therefore, it is possible to restrict the development of secondary electron avalanche on the surface of the insulating cylinder, and it is expected that the withstand voltage performance will be improved.

However, such a device has the following drawbacks.

In other words, in a vacuum valve, the electrode surface rapidly rises in IIA temperature due to the arc that occurs when the current is cut off, and the temperature rises due to heat run tests, etc., so parts inside the nitrous oxide container must have as high a thermal conductivity as possible. Must be.

However, insulating materials such as alumina or epoxy resin have low thermal conductivity, so their heat dissipation properties are significantly reduced.

Furthermore, since the dielectric strength of the insulating material itself of alumina or epoxy resin is low, the vehicle pressure resistance performance does not improve as much as expected.

Furthermore, this type of vacuum valve requires vacuum heating of several 100 degrees CVc for degassing treatment.

Therefore, the melting point of the components in Makabe pulp must be higher than the heating temperature. On the other hand, since the epoxy resin has a low melting point, in order to use the epoxy resin in a vacuum container, the heating temperature must be lowered, and sufficient degassing treatment cannot be performed.

In addition, when coated with alumina, etc., the melting point is high, so degassing treatment can be performed sufficiently.Due to the difference in thermal expansion with metal shielding), it is difficult to prevent arcing during heat treatment or when shutting off. This causes thermal expansion stress, resulting in damage and cracks.

If a slight crack occurs, let alone damage, electrons will be emitted through the crack, and the effect of suppressing electron emission will be lost, resulting in a drop in withstand voltage.

Therefore, it is difficult to coat the shield of a vacuum valve with an insulating material such as alumina or epoxy resin, and it is difficult to put into practical use a vacuum valve that has good vehicle pressure resistance and is suitable for high pressure. I was upset.

[Purpose of the invention]

An object of the present invention is to provide a vacuum valve that has good heat dissipation characteristics and excellent withstand voltage performance.

[Summary of the invention]

The present invention is characterized in that the flange shield and the arc shield are made of an insulator, and one side of the insulator is covered with a metal film.

Hereinafter, one embodiment of the present invention will be explained in detail with reference to FIGS. 4 and 5.

Note that the same parts as in FIG. 1 are designated by the same reference numerals, and the explanation thereof will be omitted. As shown in Fig. 4, the insulating cylinder 1a is
A vacuum container is formed by sealing the end plates 2 and 3 to both ends of the insulating parts 2J1 arranged in parallel, respectively, and the identification electrode 4 is a contact at the tip of the current-carrying shaft 4a that passes through the end plate 2 and is sealed. 4b and an electrode 4c is provided.

Further, the movable electrode 5 is movably sealed to the end plate 3 via a bellows 6 that covers a cover 6i+.
An electrode 5c having a tip yc contact 5b is provided. The fixed electrode side end plate 2 and the movable side end plate 3 are provided with a green bag flange shield door 7 having a metal skin cover 10 formed on one side thereof, and both flanges A support metal fitting 11 is provided on the inner wall of the connecting part of the P3 edge tube 1 in the middle of the lead 7.7 to hold the arc/- lead 9 made of an insulator on which a metal coating 10 is formed on one side. I have to.

Each axial end of the flange/rud 7 and arc/rud 9 is provided with circular arc portions 7a and 9a, and the circular arc portion 7a at the end of the flange shield 7 has a curvature of one surface. A circular arc portion 9 at the tip of the arc 7-led 9 has a radius r1.
a has a radius of curvature r2 of its cross section. These curvatures reduce the electric field strength at these ends, where the electric field strength is strongest, to below the allowable value of the insulator, and when electrons are emitted, they truss at these curvatures and the electrons enter the insulating cylinder l. The purpose is to prevent collisions.

By the way, the physical properties of the insulating materials used in the 7th grade are as shown in Table 1, including alumina, boron nitride, and glass, but also including epoxy resin.

As shown in Table 1 in the margin below, the expansion coefficients of metals and insulators differ by several times, which explains why strain increases due to heat and insulators break down. However, in the case of the insulating piece in which an iTK metal film is formed as in the present invention, it is difficult to understand whether it is due to the extensibility of the metal. Since the metal film is distorted by the thermal expansion lK of the three edges and a slight strain stress, the stress within the insulator is kept to a minimum and good characteristics are maintained.

In addition, boron nitride, borosilicate glass, quartz glass, and the like are excellent in terms of dielectric strength9, and shields made of these materials are extremely superior.

Furthermore, VC boron nitride has a thermal conductivity comparable to that of metals, making it ideal for arc shielding. Additionally, glass can be easily processed by heating, making it convenient for manufacturing effective shields.

In this way, boron nitride, borosilicate glass, quartz glass, alumina, etc. are used to form the arc of a vacuum bulb.
By manufacturing the flange shield 7 and the flange shield 7, the electric field strength in this part can be increased, and since the insulating tube is the part facing the alC, the precursor breakdown current radiated from the flange shield 7 and the arc shield 9 can be suppressed. However, secondary electron avalanche on the surface of the insulating cylinder 1a can be suppressed.

The relationship between this precursor breakdown current and the applied voltage is shown in FIG.

In the same figure, the vertical axis shows the precursor breakdown of colored lacquer, and the horizontal axis shows the applied voltage. Curves Ia and 2 are for the case where a metal shield is used, and curve Ib is for the case where a metal coating is applied to the shield made of an insulator. When this precursor breakdown current reaches a predetermined limit Ic, dielectric breakdown occurs. This precursor breakdown current suppresses ff7! The dielectric breakdown voltage increases because of the electric current.

Therefore, in FIG. 4, the fracture ↑L pressure between the arc 7 - lead 9 and the flange shield 7 increases, so the tip of the arc portion 9a of the arc shield 9 and the arc portion 7 of the flange shield 7
It is possible to shorten the gap length between the tip of the insulating cylinder 1a and the arc shield 9 and the flange/
- The distance between the leads 7 can also be shortened, and the volume of the pulp can be reduced by 42 widths.

In addition, boron nitride, borosilicate glass, quartz glass, and aluminum foil have very high melting points, and their melting points are high enough to reach the heat treatment temperature during the degassing treatment of vacuum pulp. The pressure doesn't get too high either.

Furthermore, as is clear from Table 1, boron nitride has higher thermal conductivity and better heat dissipation properties than other insulating materials such as alumina and epoxy resin, so it can be used as an insulating material for arc shields. Even if a sudden temperature rise occurs due to stain flow cutoff, the heat can be quickly radiated to the outside, and the temperature inside the bulb can be maintained at a low temperature.

Therefore, the volume of the vacuum container can be reduced, IQ1
Significant cost reductions can be achieved.

In addition, since the gap length between the arc parts 9a and 7a of the arc shield 9 and flange shield 7 can be shortened, it is possible to prevent all steam generated from between the electrodes 4.5 from adhering to the inner surface of the insulating cylinder when the current is cut off. As a result, it is possible to prevent a drop in withstand pressure due to metal vapor adhering to the inner surface of the container 1a with 7 or 8 edges when a large current is cut off.

Next, the operation and effect of another embodiment will be described with reference to FIG. 6, which is another embodiment.

Note that the same parts as in FIG. 4 are given the same reference numerals, and the explanation thereof will be omitted. As shown in FIG. 6, the metal vacuum container 1b has upper and lower insulating tubes 1a and 1a hermetically sealed, and upper and lower end plates 2 and 3 are hermetically attached to this to form a vacuum container, The fixed electrode 4 is sealed by penetrating the end plate 2).A probe 4b'f: a downwardly tilted cylindrical electrode 4c is provided at the tip of the current-carrying shaft 4a.

Further, the movable electrode 5 is provided with a contact 5b at the tip D+a l' of the current-carrying shaft 5a, which is movable through the bellows 6 having a cover 6a on the ground plate 3. ing.

The fixed electrode side end plate 2 and the movable electrode side end plate 3 are each provided with a flange mold 7 made of an insulator with a metal film 1.0 formed on one side, and furthermore, both ends VC of the metal vacuum vessel 16 are provided.
(Similarly to ri, a shield 7 made of a one-color fabric with a metal coating 10 formed on one side is provided.

In this embodiment, the metal vacuum vessel 1b also has the function of an arc shield that protects the insulator from the arc generated when it is cut off, so a total of four shields 7 are provided on the end plates 2, 3 and the metal vacuum vessel 1b. 7 for relaxing the electric field at the end
Only one field function is available.

Therefore, since the arc does not touch these directly,
Since it can be manufactured from glass that is easy to process, a shape that provides a suitable field distribution can be obtained, and the withstand voltage characteristics and breaking performance are dramatically improved.

〔Effect of the invention〕

According to the present invention, by using boron nitride-based porcelain, glass, alumina porcelain, etc. as materials for each of the fushinji shield and the arc shield, the creepage resistance between the shields is improved, and the overall shape is improved. It is possible to downsize and significantly reduce costs. In particular, when boron nitride is used, it has good heat dissipation characteristics, so it is possible to provide a vacuum valve suitable for high voltage and large capacity.

[Brief explanation of drawings]

Figure 1 is a vertical cross-sectional view showing a conventional vacuum valve, Figure 2 is a cross-sectional view showing the main parts of the arc shield and flange/rud of a conventional vacuum valve, and Figure 3 is a diagram showing the secondary/seiko emission characteristics. Characteristic diagram; Figure 4 is a vertical cross-sectional view showing the vacuum pulp of the present invention; Figure 5 is a characteristic diagram showing the relationship between applied pressure and precursor breakdown current; Figure 6 is a diagram showing the vacuum pulp of another example. FIG. 7...Flange shield 9...Arc shield 10...Metal coating (7317) Representative Patent Attorney Noriyuki Chika (Haga 1)
Name] Figure 1 Figure 2 Upper Figure 3 Figure 4 Figure 5

Claims (1)

[Claims] A pair of contactable electrodes is arranged in a vacuum container consisting of an insulating container and an end plate that closes the insulating container, and at least one of the pair of electrodes is movably sealed to the end plate via a bellows. In the vacuum pulp, a flange shield supported by the end plate is disposed and an arc 7-fold surrounds the electrode at the back. A vacuum pulp characterized by having one side formed with a metal film.