JP2013242978A - Vacuum valve - Google Patents

Abstract

PROBLEM TO BE SOLVED: To stabilize insulation performance of a contact and a shield efficiently by suppressing discharge occurring on the creepage of an insulation container in the voltage conditioning step of a vacuum valve, and to provide an inexpensive vacuum valve by shortening the voltage conditioning step thereby reducing the manufacturing cost.SOLUTION: The vacuum valve includes a pair of electrodes 4, 5 which hold a pair of contacts 43, 53 arranged oppositely in a vacuum container, respectively, via contact holding parts 42, 52 and making and breaking the pair of contacts, and a shield 7 formed to surround the pair of contacts and the contact holding parts facing each other and fixed to the vacuum container. A nickel plating layer 8 is provided at a part of at least one of the pair of contacts and contact holding parts facing the shield.

Description

  The present invention relates to a vacuum valve that cuts off a circuit current by utilizing the excellent diffusion performance and insulation performance of a vacuum.

In an electrode incorporated in a vacuum valve, a technique of driving and diffusing an arc by applying a magnetic field to a vacuum arc generated between the contacts by providing a coil behind the contacts is widely used. As a result, only a part of the contacts is heated in a concentrated manner to prevent a large amount of plasma from being generated, and the interruption performance can be improved. In addition to shut-off performance, vacuum valves require good insulation performance. The coil is made of a metal mainly composed of copper in order to ensure current-carrying performance, but the insulation performance of copper is low and electric discharge is likely to occur from the coil. In the vacuum valve electrode disclosed in Patent Document 1, a technique for coating the surface of the coil with chromium or tungsten is disclosed. This prevents the occurrence of electric discharge caused by the coil between the current-interrupting electrodes.
The vacuum valve has a structure in which an electrode is disposed in a cylindrical insulating container. If the insulating container is contaminated by the vapor of the electrode material generated when the current is interrupted, the insulating performance is deteriorated. Therefore, in many cases, a shield is arranged so as to surround the electrode to protect the insulating container. From the viewpoint of cost and installation volume, it is desirable to reduce the volume of the shield and the insulating container. However, if the distance between the electrode and the shield is reduced carelessly, there is a problem that electric discharge occurs between the two. . Patent Document 2 discloses a technique for suppressing the discharge generated between the electrode and the shield and reducing the size of the vacuum valve by providing a molten layer or a metal film having high insulation performance at a position facing the shield in the electrode. Is disclosed.

JP 2010-113821 (pages 3 to 4, FIG. 1) Japanese Patent Laying-Open No. 2006-318795 (first page, FIG. 1)

  As described above, it is effective to suppress the discharge between the electrode and the shield and the discharge between the electrodes when the current is interrupted by applying the metal film on the side surface of the electrode of the vacuum valve as viewed from the contact surface of the contact. It is known that there is. However, the discharge of the dark current from the metal coating may change the floating potential of the shield and induce a discharge along the surface of the insulating container. The fact that the metal coating applied to the electrode affects the creeping discharge of the insulating container not directly related to the electrode has not been clarified so far, and the coating design for suppressing the discharge has not been performed. For this reason, there has been a problem that the processing steps for stabilizing the insulation performance in the manufacturing process become long and the manufacturing cost increases.

  The present invention has been made in view of the above-described circumstances, and the discharge of dark current from the coating is suppressed, and by preventing the occurrence of creeping discharge due to the bias of the shield potential, it is possible to shorten the treatment process for stabilizing the insulation performance. Therefore, an object is to provide a vacuum valve that can be made inexpensive.

  The vacuum valve according to the present invention is opposed to a pair of electrodes provided so that the pair of contacts opposed to each other in the vacuum vessel are held via contact holding portions and the pair of contacts are contacted and separated. And a shield fixed to the vacuum vessel so as to surround the pair of contacts and the contact holding portion, and the shield in at least one of the pair of contacts and the pair of contact holding portions. A nickel plating layer is provided at the opposite location.

  According to this invention, since nickel having a high work function is used for the coating material, the discharge of the dark current from the coating is suppressed, so that it is possible to prevent the induction of the ceramic creeping discharge due to the bias of the shield potential. As a result, the process for stabilizing the insulation performance is shortened, and the vacuum valve can be provided at a low cost.

It is sectional drawing which shows the vacuum valve which concerns on Embodiment 1 of this invention. In the vacuum valve shown in FIG. 1, it is a graph which shows the result of having calculated the influence which the difference of the work function of nickel and chromium has on the creeping electric field of an insulating container. In the vacuum valve shown in FIG. 1, it is a graph which shows the result of having calculated the relationship of the molten nickel plating thickness with respect to the arc generation time in a contact side surface when an arc moves to the contact side surface at the time of interruption of electric current. It is a section end view showing the vacuum valve concerning Embodiment 3 of the present invention. FIG. 5 is a cross-sectional end view of a main part showing a modification of the electrode structure of the vacuum valve shown in FIG. 4.

Embodiment 1 FIG.
FIG. 1 is a cross-sectional view showing a vacuum valve according to an embodiment of the present invention. In the figure, the vacuum valve has a cylindrical insulating container 3 in which a fixed side end plate 1 and a movable side end plate 2 are joined at both ends and the inside is kept in a vacuum, and a rod-like shape joined to the fixed side end plate 1. The fixed side electrode 41 which consists of the fixed side conductor 41 and the fixed side contact 43 joined to the front-end | tip part in the container of the fixed side conductor 41 via the fixed side contact holding part 42, and the bellows provided in the movable side end plate 2 6 is fixed to the rod-shaped movable side conductor 51 that is airtightly held via 6 and is held movably in the direction of the axis A, and the container inner tip of the movable side conductor 51 via the movable side contact holding portion 52. 43 is formed so as to surround the movable side electrode 5 composed of the movable side contact 53 opposed to 43, and the fixed side contact 43, the fixed side contact holding part 42, the movable side contact 53, and the movable side contact holding part 52. And a shield 7 fixed to the insulating container 3. .

  The surface of the fixed side contact 43, the fixed side contact holding portion 42, the movable side contact 53, and the movable side contact holding portion 52 facing the shield 7 is nickel which is one of the characteristic portions of the present invention. A plating layer 8 is provided. The nickel plating layer 8 is for suppressing the electric discharge generated toward the shield 7, and after each member is cut, it is preferably applied to the side surface portion with a thickness of 50 μm or more. In order to distinguish the nickel plating layer 8 provided on each member, the nickel plating layer 8 is formed in the order of the fixed contact 43, the movable contact 53, the fixed contact holding part 42, and the movable contact holding part 52. May be referred to as a nickel plating layer 8a, a nickel plating layer 8b, a nickel plating layer 8c, and a nickel plating layer 8d, respectively.

  The fixed-side contact holding part 42 and the movable-side contact holding part 52 fix the fixed-side contact 43 and the movable-side contact 53 to the conductor without any positional displacement. For example, with respect to the fixed-side conductor 41 and the movable-side conductor 51, The fixed side conductor 41 and the movable side conductor 51 may be formed integrally by cutting, or may be provided by joining another member to the fixed side conductor 41 and the movable side conductor 51. Further, since the bellows 6 has flexibility, the movable contact 53 can be moved in the left-right direction along the axis A in a state where the inside is kept in a vacuum. The circuit current is opened and closed by bringing the fixed side contact 43 and the movable side contact 53 into contact with each other or opening them by the above operation. Other configurations are the same as those of the conventional one, and thus the description thereof is omitted.

  Next, the operation of the first embodiment configured as described above will be described. When the circuit current is interrupted by the vacuum valve as described above, metal vapor is generated from the stationary contact 43 and the movable contact 53. The shield 7 prevents the metal vapor from adhering to the inner surface of the insulating container 3 to deteriorate the insulating performance of the insulating container 3. Further, the shield 7 is supported by the insulating container 3 and has a configuration in which the potential is floated. Although the structure which supports the shield 7 via the metal member from the fixed side end plate 1 is also conceivable, in this case, since the potential difference generated between the movable side contact 53 and the shield 7 becomes large, it is necessary to increase the insulation distance. This leads to an increase in valve dimensions. By floating the potential of the shield 7 as in this configuration, the shield potential automatically changes to an intermediate potential between the fixed contact 43 and the movable contact 53, so the required insulation distance is minimized with a simple configuration. can do.

A technique for improving the insulation performance of a vacuum valve by providing a high pressure-resistant coating is already known. However, when the potential of the shield 7 is floating as in this configuration, the selection of the coating is not limited to the vacuum valve. Special care is required to affect the insulation performance stabilization process.
Since the insulation performance in a vacuum is strongly influenced by the micro surface state of the electrode, the insulation performance can be stabilized by a voltage conditioning process in which a weak point portion is reformed intentionally in advance. Table 1 summarizes the results of the voltage conditioning process performed to stabilize the insulation performance between the fixed side contact 43 and the fixed side contact holding part 42 and the shield 7. Table 1 shows the test results measured for the vacuum valve according to the first embodiment configured as described above, and the test measured for the comparative vacuum valve whose contact side surface was coated with chromium for comparison. The results are also shown.

  As is apparent from Table 1, the insulation performance is stabilized after the number of discharges of 146 in the vacuum valve of the first embodiment, but in the comparative example provided with the chromium film, the discharge is performed 266 times until the insulation performance is stabilized. I need a number of times. Looking at the breakdown of the discharge locations, in the first embodiment, almost all of the discharge occurs between the fixed contact 43 and the shield 7 and contributes to the modification of the electrode surface state. On the other hand, in the comparative example, as many as 74 discharges are generated between the fixed end plate 1 and the shield 7 through the creeping surface of the insulating container 3. Since this discharge does not contribute to stabilization of the insulation performance between the fixed side contact 43 and the fixed side contact holding part 42 and the shield 7 which is an original purpose of voltage conditioning, it can be said that unnecessary voltage conditioning is performed.

  As described above, the cause of the influence of the coating on the side surface of the contact on the creeping discharge of the insulating container is the bias of the shield floating potential due to the discharge of dark current from the coating. Since a high electric field is generated on the side surfaces of the contact and the contact holding portion, when a film is applied with a material having a low work function, a dark current is emitted from the film toward the vacuum. The shield 7 is electrically floated in the hope that it becomes an intermediate potential between the fixed side end plate 1 and the movable side end plate 2. However, when the charge due to the dark current accumulates in the shield 7, the potential of the shield 7 becomes intermediate. Deviation from potential. Thereby, it is considered that only a part of the electric field along the creeping surface of the insulating container is emphasized, leading to creeping discharge.

  Table 2 shows examples of work functions obtained for metal materials. Chromium and tungsten used as a high pressure-resistant coating material in Patent Document 1 and the like have a work function lower than that of copper to be coated. On the other hand, nickel used in Embodiment 1 of the present invention has both a high insulation performance in vacuum and a work function, and is therefore considered to effectively act on the suppression of creeping discharge in the insulating container 3. . FIG. 2 is a graph showing the result of calculating the influence of the work function difference between nickel and chromium shown in Table 2 on the creeping electric field of the insulating container. In FIG. 2, the vertical axis represents the ratio of the creeping electric field when nickel plating is applied to the contact side surface and the creeping electric field when a coating is formed with chromium. From FIG. 2, it can be seen that as the voltage application time is increased, the effect of nickel plating becomes significant, and the creeping electric field is reduced by 12% at the maximum as compared with the case of the chromium coating.

  The technique for providing a film on the side surface of the contact is also shown in, for example, Patent Document 2 described above. In this document, the insulation performance between the contact point and the shield 7 is improved by a coating, and the vacuum valve is miniaturized. On the other hand, as a result of further research on the coating such as the plating layer 8 on the contact side, the inventors of the present application have newly found that the coating on the contact side contributes to the improvement of the current interruption performance. That is, when the current is interrupted, the arc discharge generated on the opposing surface of the fixed contact 43 and the movable contact 53 may move to the side surface of the contact, and the high breakdown voltage layer provided on the contact side fails due to insufficient insulation performance. There is a function to prevent. It is presumed that a similar event is working in the prior art.

  However, when trying to obtain the effect of improving the current interruption performance by the metal coating, it is necessary to have a sufficient film thickness that does not melt with the energy at the time of current interruption, and by configuring to satisfy the condition, A stable effect can be expected for the first time. FIG. 3 is a graph showing the calculation result of the relationship between the thickness of the molten nickel plating and the arc generation time on the contact side surface when the arc moves to the contact side surface when the current is interrupted. In addition, it is known from the arc behavior observation at the time of current interruption that the arc generation time on the contact side surface is 4 ms at the maximum. For this reason, if the thickness of the nickel plating layer provided on the contact side surface is less than 50 μm, the nickel plating layer is melted. As in the first embodiment, by setting the thickness of the nickel plating layer to 50 μm or more, it is possible to prevent the contact from being exposed due to plating melting, and the effect of improving the stable breaking performance can be obtained.

  As described above, according to the first embodiment, the pair of fixed side contact 43 and the movable side contact 53 and the pair of fixed side contact holding unit 42 and the movable side contact holding unit 52 on the outer peripheral surface facing the shield 7. By providing the nickel plating layer 8 having a high work function with a film thickness of 50 μm or more, the discharge of dark current from the coating of the nickel plating layer 8 is suppressed, and the creeping electric field of the insulating container 3 due to the bias of the shield potential is emphasized. Therefore, it is possible to prevent the creeping discharge of the insulating container 3 from being induced. As a result, the voltage conditioning process of the vacuum valve for stabilizing the insulation performance is efficiently performed, the required time is shortened, the manufacturing cost is reduced, and the vacuum valve can be provided at a low cost. Moreover, even if the arc moves to the nickel plating side at the time of interrupting the current, the nickel plating is melted by making the thickness of the portion of the nickel plating layer 8 where the thickness is the maximum be 50 μm or more. Since the internal electrode is not exposed, good blocking performance can be expected.

Embodiment 2. FIG.
In the first embodiment, the nickel plating layer 8 is applied to all of the outer peripheral surfaces of the fixed-side contact 43 and the fixed-side contact holding portion 42 and the movable-side contact 53 and the movable-side contact holding portion 52 facing the shield 7 of each member. ing. However, of the contact and the contact holding part, the member having a larger outer diameter and a shorter distance from the shield 7 has a larger electric field generated on the surface, and thus greatly contributes to a change in shield potential due to dark current emission. Therefore, the nickel plating layer 8 can be provided only on a member having a large outer diameter among the contacts and the contact holding portion, and the nickel plating layer 8 for a member having a small outer diameter can be omitted. For example, in the example of FIG. 1, the outer diameters of the stationary contact 43 and the movable contact 53 are larger than the outer diameters of the contact holders 42 and 52. For this reason, only the nickel plating layers 8a and 8b may be provided, and the nickel plating layers 8c and 8d may be omitted.

  In the second embodiment configured as described above, the nickel plating layer is applied only to the portion that is dominant in the dark current emission phenomenon, and the nickel plating layer is not formed in the other portions, thereby removing the nickel plating layer. Since the cost required for the plating process can be reduced, a lower cost vacuum valve can be provided.

Embodiment 3 FIG.
FIG. 4 is a cross-sectional end view showing a vacuum valve according to Embodiment 3 of the present invention, and FIG. 5 is a cross-sectional end view showing a principal part of a modification of the electrode structure of the vacuum valve shown in FIG. In FIG. 4, the fixed-side contact holding part 42 and the movable-side contact holding part 52 formed of a metal such as stainless steel hold the corresponding fixed-side contact 43 or the movable-side contact 53 at the center part of the axis A, respectively. doing. The rod-shaped fixed-side conductor 41 and the fixed-side contact 43, and the rod-shaped movable-side conductor 51 and the movable-side contact 53 are electrically connected in series to the outer portions of the contact holding portions 42 and 52 with respect to the axis A. A fixed side coil electrode 44 and a movable side coil electrode 54 made of a good conductor such as copper, which are formed by being cut and connected to each other, are provided.

  The surface of the fixed side coil electrode 44 and the movable side coil electrode 54 facing the shield 7 and the outer peripheral surface of the fixed side and movable side contacts 43 and 53 are the same nickel plating layer 8 (8c) as in the first embodiment. , 8d, 8a, 8b). In the third embodiment, the fixed side and movable side coil electrodes 44 and 54 are provided behind the fixed side and movable side contacts 43 and 53, respectively, so that a magnetic field is generated between the contacts and the interruption performance is improved. Yes. As shown in the modification of FIG. 5, the outer diameters of the fixed-side coil electrode 44 and the movable-side coil electrode 54 are made larger than the outer diameters of the fixed-side and movable-side contacts 43 and 53, and the outer periphery of the coil electrode As a configuration in which the portion protrudes outward, the nickel plating layers 8c and 8d may be provided only on the protruding portion.

  According to the third embodiment configured as described above, since a uniform magnetic field is generated between the pair of contact points 43 and 53 facing each other, it can be expected that the breaking performance is improved. Thus, also in the vacuum valve which improves the interruption | blocking performance using the magnetic field by a coil, the effect similar to Claim 1 can be acquired. Further, in the configuration of the modification shown in FIG. 5, the outer diameters of the fixed side coil electrode 44 and the movable side coil electrode 54 are made larger than the outer diameters of the fixed side and movable side contacts 42, 53. As described in the second embodiment, since the nickel plating layer on the outer peripheral surfaces of the fixed side and movable side contacts 42 and 53 can be omitted, it can be provided at low cost. Further, since the coil electrode projects outward from the contact, a uniform magnetic field can be generated between the contacts, and a good breaking performance can be obtained.

  It should be noted that within the scope of the present invention, a part or all of each embodiment can be freely combined, or each embodiment can be appropriately modified or omitted.

  DESCRIPTION OF SYMBOLS 1 Fixed side end plate, 2 Movable side end plate, 3 Insulation container, 4 Fixed side electrode, 41 Fixed side conductor, 42 Fixed side contact holding part, 43 Fixed side contact, 44 Fixed side coil electrode, 5 Movable side electrode, 51 Movable side conductor, 52 Movable side contact holding portion, 53 Movable side contact, 54 Movable side coil electrode, 6 Bellows, 7 Shield, 8 (8a, 8b, 8c, 8d) Nickel plated layer, A axis.

Claims (6)

  A pair of contacts opposed to each other in the vacuum vessel are respectively held via a contact holding portion, and a pair of electrodes provided so that the pair of contacts are contacted and separated, and the pair of contacts and the contacts opposed to each other A shield formed so as to surround the holding portion and fixed to the vacuum vessel, and a nickel plating layer at a location facing at least one of the pair of contacts and the pair of contact holding portions A vacuum valve characterized by providing.   2. The vacuum valve according to claim 1, wherein the nickel plating layer is provided on a member of the pair of contacts and the pair of contact holding portions that are close to the shield. 3.   The contact holding part is composed of a part of a bar-shaped conductor constituting the electrode, and the nickel plating layer is provided on an outer peripheral surface part of the contact formed to have a diameter larger than that of the bar-shaped conductor. The vacuum valve according to claim 2.   A coil electrode that electrically connects the contact and a rod-shaped conductor that constitutes the electrode in an outer portion of the contact holding portion is provided in a portion facing the shield in the coil electrode. The vacuum valve according to claim 1, wherein a nickel plating layer is provided.   The vacuum valve according to claim 4, wherein an outer diameter of the coil electrode is larger than an outer diameter of the contact.   The vacuum valve according to any one of claims 1 to 5, wherein a thickness of the nickel plating layer is 50 µm or more.

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