Vacuum capacitor

Abstract

The present invention comprises a polygonal cylinder-like conductive wall part (5) which can extend / contract in the axial direction with respect to the outer peripheral side of a bellows (4) inside a vacuum container (10) and has a larger diameter than the bellows (4). A cutout part (61) having a shape penetrating in the radial direction and extending in the axial direction is provided at a central part, in the axial direction, of each corner part (6) positioned on each ridge line of the conductive wall part (5). In each of side wall parts (7) positioned between the ridge lines of the conductive wall part (5) and extending in the axial direction, an inter-cutout portion (71) positioned between the pair of cutout parts (61), facing each other in the circumferential direction, of the side wall part (7) is configured to be curved outward in the radial direction or curved inward in the radial direction. Each of the corner parts (6) has only one of the cut-out parts (61) or a plurality of the cut-out parts (61).

Description

Vacuum Capacitor

[0001] The present invention relates to a vacuum capacitor, and more particularly to a vacuum capacitor technology applicable to impedance adjustment in high-frequency devices such as high-frequency power sources for semiconductor equipment and high-power oscillator circuits.

[0002] 2. Description of the Related Art Conventionally, various vacuum capacitors have been used for impedance adjustment in high-frequency devices such as high-frequency power supplies and high-power oscillator circuits in general semiconductor equipment.

[0003] A typical vacuum capacitor uses a vacuum container having a cylindrical body at least part of which is insulating, and this vacuum container is configured such that one side (hereinafter simply referred to as the one axial side) of the cylindrical body in the axial direction (hereinafter simply referred to as the axial direction) is closed with a fixed-side conductor, and the other side (hereinafter simply referred to as the other axial side) of the cylindrical body in the axial direction is closed with a movable-side conductor.

[0004] Within the vacuum vessel, there are provided a fixed electrode provided on one axial side (fixed conductor side) of the vacuum vessel, a movable electrode support part located opposite the fixed electrode within the vacuum vessel and movable in the axial direction, and a movable electrode provided opposite the fixed electrode on one axial side of the movable electrode support part and forming an electrostatic capacitance between it and the fixed electrode.

[0005] A cylindrical bellows, which is expandable and contractible in the axial direction and supports the movable electrode support on the movable conductor, is provided between the movable electrode support and the movable conductor. The bellows divides the interior of the vacuum vessel into a vacuum chamber on the outer periphery of the bellows and an atmospheric chamber on the inner periphery of the bellows.

[0006] In recent years, the load on high-frequency equipment has gradually increased, and the high-frequency current that can flow through such equipment has also increased. For this reason, vacuum capacitors used in such equipment are required to have a high ability to pass high-frequency current.

[0007] For example, in Patent Document 1, a cylindrical conductive wall portion (a "second bellows" designated by reference numeral 17 in Patent Document 1) having a larger diameter than a bellows (a "first bellows" designated by reference numeral 16 in Patent Document 1) is provided by being joined (electrically connected) to both the movable electrode support portion and the movable-side conductor on the outer periphery of the bellows. As a result, due to the skin effect, high-frequency current flows more easily through the conductive wall portion than through the bellows.

[0008] If the conductive wall were simply a thin-walled cylindrical structure, even if a high-frequency current could be passed through it, it would be difficult for it to expand and contract in the axial direction, which could hinder the expansion and contraction of the bellows and the movement of the movable electrode support part. Furthermore, if a simple flat plate structure were used, even if the axial bending and stretching motion allowed the entire wall to expand and contract in the axial direction, buckling or breakage of the conductive wall would likely occur.

[0009] For this reason, in the conductive wall portion shown in Patent Document 1, a bellows-shaped configuration is applied in which the cross section of the conductive wall portion in the radial direction (hereinafter simply referred to as the radial direction) is circular, and reduced diameter portions and expanded diameter portions are arranged alternately in the axial direction, similar to a bellows.

[0010] Japanese Patent Application Publication No. 10-284347

[0011] In the conductive wall portion having a circular radial cross section and a simple bellows-like shape as described above, in order to obtain the desired axial flexibility, for example, reduced diameter sections and expanded diameter sections are arranged in multiple stages, which tends to increase the number of stages in the axial direction.

[0012] As the number of steps in the axial direction increases, the creepage distance (corresponding to the current-carrying distance) in the axial direction tends to increase, and the resistance tends to increase. In such a conductive wall portion, the amount of heat generated when a high-frequency current flows through the conductive wall portion (hereinafter simply referred to as the heat generation amount during current flow) increases, which may make it difficult to obtain the desired current-carrying capacity.

[0013] For example, if the conductive wall portion is simply increased in diameter in the radial direction or simply made thicker (a shape with increased radial thickness), the radial cross-sectional area of ​​the conductive wall portion will increase, which may potentially reduce the amount of heat generated when current is applied as described above.

[0014] However, this leads to an increase in the mass of the conductive wall itself, and stress (bending stress, etc.) due to the moment of inertia is more likely to occur during operation of the vacuum capacitor (for example, during sudden acceleration or sudden stopping due to high-speed operation), which may shorten the product life (high-speed operating life, etc.). Furthermore, if the wall is thickened, the elasticity in the axial direction decreases and bending stress increases, which may result in a shorter product life.

[0015] The present invention has been made in consideration of the above-mentioned technical problems, and has an object to provide a vacuum capacitor that can contribute to making it easier to obtain a desired high-frequency current carrying capacity and product life.

[0016] The vacuum capacitor of the present invention is an invention that can solve the above-mentioned problems, and one aspect thereof comprises: a vacuum container having a cylindrical body at least partially insulating, the fixed side of the cylindrical body being closed with a fixed conductor and the movable side of the cylindrical body being closed with a movable conductor; a fixed electrode provided on one side of the vacuum container in the axial direction; a movable electrode support part located opposite the fixed electrode within the vacuum container and movable in the axial direction; a movable electrode provided on one side of the movable electrode support part in the axial direction opposite the fixed electrode and forming a capacitance between it and the fixed electrode; a bellows that is cylindrical and expandable in the axial direction between the movable electrode support part and the movable conductor, and supports the movable electrode support part on the movable conductor; and a conductive wall part that is polygonal and expandable in the axial direction and has a diameter larger than the bellows, is located coaxially on the outer periphery of the bellows, and is joined to the movable electrode support part and the movable conductor.

[0017] The interior of the vacuum vessel is divided by the bellows into a vacuum chamber on the outer periphery of the bellows and an atmospheric chamber on the inner periphery of the bellows, and the conductive wall portion has a plurality of corners located on each ridge line of the conductive wall portion in the axial direction and extending along each of the ridge lines, and a plurality of side wall portions located between each of the ridge lines in the circumferential direction of the conductive wall portion and extending in the axial direction.

[0018] Each of the corners has a notch at the center of the axial direction of the corner, the notch penetrating the conductive wall in a radial direction and extending in the axial direction, and each of the side wall portions has an inter-notch portion, which is a portion of the side wall portion between a pair of the notches that are opposed to each other in the circumferential direction, that is, a portion that is convexly curved outward in the radial direction.

[0019] Furthermore, each of the side wall portions may be characterized in that the inter-notch portions, which are portions of the side wall portion between a pair of the notches opposing each other in the circumferential direction, are each curved convexly inward in the radial direction.

[0020] In addition, each corner may have a plurality of the notches formed at predetermined intervals in the axial direction.

[0021] The present invention may also be characterized in that an elastic body extending in the axial direction and being stretchable in the axial direction is provided between the bellows and the conductive wall portion.

[0022] The conductive wall portion may also be characterized in that a middle wall portion located between the respective notches aligned in the axial direction of the conductive wall portion is provided with a protruding wall portion protruding radially inward from the middle wall portion, the protruding wall portion dividing the space between the bellows and the conductive wall portion into sections of approximately equal dimensions in the axial direction, and each divided section is provided with an elastic body that is freely expandable and contractible in the axial direction and has approximately equal elastic modulus.

[0023] Each of the side wall portions may be characterized in that the hardness of a non-inter-notch portion portion, which is a portion of the side wall portion other than the inter-notch portion portion, is greater than the hardness of the inter-notch portion portion.

[0024] The present invention may also be characterized in that a reinforcing portion is provided in the area between the non-cutout portions.

[0025] The cross-sectional area of ​​each of the portions between the cutouts at both end sides in the axial direction may be larger than the cross-sectional area of ​​the portion between the cutouts at a central portion in the axial direction.

[0026] As described above, the present invention can contribute to making it easier to obtain the desired high frequency power carrying capacity and product life.

[0027] Schematic explanatory diagram of a vacuum capacitor 1A in an embodiment (longitudinal cross-sectional view in the axial direction). Cross-sectional view of vacuum capacitor 1A along line X-X'. Schematic diagram of a metal panel for explaining an example of a method for forming a conductive wall portion 5 (a case where there are multiple cutout portions 61 at each corner 6, and a view equivalent to a developed view of the conductive wall portion 5). Schematic diagram of a metal panel for explaining an example of a method for forming a conductive wall portion 5 (a case where there is one cutout portion 61 at each corner 6, and a view equivalent to a developed view of the conductive wall portion 5). Schematic explanatory diagram of a vacuum capacitor 1B in an embodiment (longitudinal cross-sectional view in the axial direction).

[0028] The vacuum capacitor according to the embodiment of the present invention is completely different from the conductive wall portion of Patent Document 1, which has a circular radial cross section and a simple bellows-shaped configuration (hereinafter simply referred to as a bellows-shaped configuration).

[0029] That is, the vacuum capacitor of this embodiment has a polygonal cylindrical conductive wall portion that is axially expandable and contractible and has a diameter larger than that of a bellows. This conductive wall portion has a notch (such as a slit hole) that penetrates radially and extends axially at the center of each corner located on each ridge line of the conductive wall portion in the axial direction.

[0030] In each side wall portion located between each ridge line in the circumferential direction (hereinafter simply referred to as the circumferential direction) of the conductive wall portion and extending in the axial direction, the portion between a pair of circumferentially opposing notches in the side wall portion (hereinafter simply referred to as the inter-notch portion portion) is configured to be convexly curved radially outward or convexly curved radially inward.

[0031] According to the configuration of this embodiment, the portions of each side wall of the conductive wall between the notches can bend and stretch in the axial direction while being convexly curved either radially outward or radially inward, thereby enabling the conductive wall as a whole to expand and contract in the axial direction.

[0032] On the other hand, the conductive wall portions other than the portions between the notches (hereinafter referred to simply as "non-notch portions") do not bend or stretch like the portions between the notches, but function as frames (supports). In particular, corners (corners other than the notches) tend to function as frames. This increases the mechanical strength of the conductive wall portions, making it easier to prevent buckling or breakage of the conductive wall portions, and thus making it easier to achieve the desired product life.

[0033] For example, in order to increase the axial flexibility of a bellows-shaped cylindrical structure, the number of stages in the axial direction can be increased, but in this case, the creeping distance in the axial direction tends to become longer and the resistance value tends to become larger.

[0034] In contrast, in the configuration of this embodiment, the axial flexibility of the conductive wall portion can be improved simply by increasing the amount of axial bending and stretching movement (hereinafter simply referred to as the amount of bending and stretching movement) of the portions between the notches of each side wall portion, without increasing the number of axial steps as in the bellows-shaped configuration.

[0035] One way to increase the amount of bending and stretching motion is to increase the axial dimension of the area between the cutouts by increasing the axial dimension of the cutouts formed in each corner.Another way is to increase the total amount of bending and stretching motion in each area between the cutouts by forming multiple cutouts in each corner and multiple areas between the cutouts in each side wall.

[0036] In other words, compared to a bellows-shaped configuration, the configuration of this embodiment can be configured with fewer steps in the axial direction, which makes it easier to prevent the axial creepage distance of the conductive wall portion from becoming too long and also makes it easier to prevent the resistance value from becoming too large.

[0037] Therefore, according to the configuration of this embodiment, the amount of heat generated during current flow can be sufficiently suppressed and the desired high-frequency power carrying capacity can be obtained without increasing the radial cross-sectional area as in the bellows-shaped configuration. Furthermore, since there is no increase in the mass of the conductive wall portion itself, stress due to the moment of inertia that may occur during operation of the vacuum capacitor can be sufficiently suppressed, and the desired product life can be obtained.

[0038] The vacuum capacitor of this embodiment can be configured in a variety of ways, as long as the portions of each side wall of the polygonal cylindrical conductive wall between the notches are curved convexly either radially outward or radially inward, thereby allowing the conductive wall as a whole to expand and contract in the axial direction, as described above. That is, the design can be modified by appropriately applying common technical knowledge in various fields (e.g., vacuum capacitors, bellows, molding, springs, etc.) and by referring to prior art documents as necessary. The following examples are examples of such modifications.

[0039] In the following embodiments, detailed explanations will be omitted as appropriate, for example, by referring to the same reference numerals for similar contents.

[0040] 1 to 4 illustrate the configuration of a vacuum capacitor 1A according to an embodiment. In this vacuum capacitor 1A, both axial ends (one axial side and the other axial side) of a cylindrical body 1, at least a portion of which is insulating, are closed by a fixed conductor 2 and a movable conductor 3, respectively, to form a vacuum vessel 10.

[0041] Within the vacuum vessel 10, there are provided a fixed electrode 21 provided on the side of the fixed side conductor 2 within the vacuum vessel 10, a movable electrode support part 30 arranged opposite the fixed electrode 21 within the vacuum vessel 10 and movable in the axial direction (towards both ends of the cylindrical body 1), and a movable electrode 31 arranged opposite the fixed electrode 21 on one side of the axial direction of the movable electrode support part 30 and forming an electrostatic capacitance between it and the fixed electrode 21.

[0042] Between the movable electrode support part 30 and the movable-side conductor 3 in the vacuum vessel 10, there is provided a bellows 4, which is cylindrical and expandable in the axial direction, and which supports the movable electrode support part 30 on the movable-side conductor 3. One axial side of the bellows 4 is joined to the other axial side of the movable electrode support part 30, and the other axial side of the bellows 4 is joined to the inner wall side of the movable-side conductor 3.

[0043] The bellows 4 allows the movable electrode 31 and the movable electrode support part 30 to move axially while maintaining an airtight (airtight so as to create a vacuum) space 11 (hereinafter referred to as the vacuum chamber) surrounded by the outer periphery of the bellows 4 within the vacuum vessel 10, i.e., the cylindrical body 1, the fixed conductor 2, the movable conductor 3, the bellows 4, and the movable electrode support part 30. Inside the vacuum vessel 10, an atmospheric pressure space 12 (hereinafter referred to as the atmospheric chamber) is formed on the inner periphery of the bellows 4.

[0044] A conductive wall portion 5 is provided on the outer periphery of the bellows 4 in the vacuum chamber 11. The conductive wall portion 5 is a polygonal cylindrical portion (hexagonal cylindrical portion in FIGS. 1 to 4) that is expandable and contractible in the axial direction and has a larger diameter than the bellows 4. The conductive wall portion 5 is positioned coaxially on the outer periphery of the bellows 4, and both ends of the conductive wall portion 5 in the axial direction are joined to the movable electrode support portion 30 and the movable-side conductor 3, respectively.

[0045] In each corner 6 of the conductive wall 5, which is located on each axial ridge (the dotted line portion depicted as extending in the vertical direction in Figures 3 and 4 ) of the conductive wall 5, a notch (slit hole, etc.) 61 is provided in the axial center of the corner 6, which has a shape that penetrates radially and extends in the axial direction.

[0046] Furthermore, side walls 7 extending in the axial direction are provided between each ridge line in the circumferential direction of the conductive wall 5. In the case of each side wall 7 shown in Figures 1 and 2, inter-notch regions 71, which are regions between a pair of circumferentially opposing notches 61 of the side wall 7, are configured to be curved convexly outward in the radial direction. This type of conductive wall 5 allows each side wall 7 to bend and stretch while curving convexly outward in the radial direction at the inter-notch regions 71, and the conductive wall 5 as a whole is configured to be able to expand and contract in the axial direction.

[0047] 1, an elastic body 8 (specifically, two elastic bodies 8a and 8b in FIG. 1; hereinafter, these will be simply referred to as the elastic body 8 as appropriate) that extends axially and is flexible in the axial direction is provided in the space 90 between the bellows 4 and the conductive wall 5. Both axial ends of the elastic body 8 are joined to the movable electrode support part 30 and the movable-side conductor 3, respectively.

[0048] The materials (electrode materials, metal materials, insulating materials, etc.), shapes, etc. of the components of the vacuum capacitor 1A described above, as well as the processing and assembly methods of the components, can be appropriately applied in various ways depending on the intended use of the vacuum capacitor 1A, as long as the structures are appropriately designed so that the components do not interfere with each other.

[0049] <Example of vacuum vessel 10> The vacuum vessel 10 can be configured in various ways as long as both axial ends of a cylindrical body 1, at least a portion of which is insulating, can be closed by a fixed conductor 2 and a movable conductor 3, and a vacuum chamber 11 and an atmospheric chamber 12 can be formed within the vacuum vessel 10 via a bellows 4 or the like.

[0050] In the case of the cylindrical body 1 shown in Figures 1 and 2, flange tubes 14 (fixed conductor 2 side) and 15 (movable conductor 3 side) made of a metal material (for example, metal materials such as copper, stainless steel (SUS), various alloys (beryllium copper, etc.), and metal materials that have been subjected to various processing processes (copper plating, copper clad lamination, etc.)) are coaxially connected to both axial ends of an insulating tube 13 made of an insulating material (for example, a ceramic material, etc.). Both ends of the cylindrical body 1 are closed by flat plate-shaped fixed conductors 2 and movable conductors 3 made of metal materials, respectively.

[0051] <Example of Fixed Electrode 21 and Movable Electrode 31> Both the fixed electrode 21 and the movable electrode 31 (hereinafter simply referred to as the two electrodes) can form a capacitance between them, and various configurations can be applied to each of them as long as the capacitance changes in accordance with the axial movement of the movable electrode 31. One example is a configuration in which the two electrodes can cross each other in the axial direction without contacting each other, and a desired capacitance is formed between the two electrodes in accordance with the amount of crossing (crossing area) in the axial direction.

[0052] 1, the electrodes are configured as an electrode group in which a plurality of substantially cylindrical electrode members (thin-walled electrode members with small radial thicknesses) 21a, 31a, each having a different inner diameter, are concentrically arranged at regular intervals. The electrode members of both electrodes can cross each other in the axial direction without contacting each other, and a desired capacitance can be formed between the electrodes depending on the amount of crossing in the axial direction.

[0053] Instead of the plurality of substantially cylindrical electrode members as described above, the electrodes may each be formed of an electrode member extending in a spiral shape. In this case, the electrode members of the electrodes can cross each other in the axial direction without contacting each other, and a desired capacitance can be formed between the electrodes depending on the amount of crossing in the axial direction.

[0054] <Example of Movable Electrode Supporting Section 30> The movable electrode supporting section 30 may be configured to be movable in the axial direction while supporting the movable electrode 31, and various configurations are applicable.

[0055] 1 is made of a metal material and has a flat plate shape extending in the radial direction, with the central portion being thickened in the axial direction. The movable electrode 31 is supported on one side of the movable electrode support part 30 in the axial direction.

[0056] A movable rod (cylindrical movable rod in Figures 1 and 2) 32 is provided in the center of the back side of the movable electrode support part 30 (the other axial side where the movable electrode 31 is not provided) and has a shape extending from the center to the other axial side (in Figure 1, it has a shape extending so as to penetrate through the movable side conductor 3 side of the vacuum vessel 10 and protrude).

[0057] In the case of the movable rod 32 shown in Figure 1, it is supported so as to be freely slidable in the axial direction (the outer surface of the movable rod 32 is freely slidable on the bearing member 34) via a bearing member 34 provided in the vacuum vessel 10 (provided in the through hole 33 at approximately the center of the movable side conductor 3 in Figure 1).

[0058] By moving this movable rod 32 in the axial direction via, for example, a drive source (motor or the like) not shown, the movable electrode support part 30 moves in the axial direction together with the movable electrode 31 .

[0059] <Example of Bellows 4> The bellows 4 is cylindrical and can expand and contract in the axial direction, and can support the movable electrode support part 30 so that it can move freely relative to the movable-side conductor 3 while keeping the vacuum chamber 11 airtight, and various configurations are possible.

[0060] The bellows 4 shown in FIGS. 1 and 2 is a molded body formed from a metal material (e.g., stainless steel) into a thin-walled bellows-like cylindrical shape, and has a configuration in which reduced diameter portions 41 and expanded diameter portions 42 are alternately arranged in multiple stages in the axial direction (e.g., approximately 10 to 20 reduced diameter portions 41 and approximately 10 to 20 expanded diameter portions 42 are alternately arranged).

[0061] <Example of conductive wall portion 5> The conductive wall portion 5 is a polygonal tube having a larger diameter than the bellows 4, and it is sufficient that the inter-notch portions 71 of the side wall portions 7 between the ridge lines (between the corners 6) are able to bend and stretch so as to be convexly curved only either radially outward or radially inward (radially outward in FIGS. 1 and 2 ). It is also sufficient that the conductive wall portion 5 as a whole is configured to be able to expand and contract in the axial direction by the bending and stretching, and various configurations are applicable.

[0062] Each corner 6 of the conductive wall 5 may have only one notch 61 formed therein, or may have a plurality of notches 61 formed therein.

[0063] When multiple notches 61 are formed in each corner 6, multiple inter-notch regions 71 are formed in each side wall 7. As a result, when the conductive wall 5 expands or contracts, the inter-notch regions 71 in each side wall 7 share the bending and stretching action.

[0064] Furthermore, since the amount of bending and stretching of each inter-notch portion 71 can be reduced, it becomes easier to prevent interference with, for example, adjacent components (such as the inner wall surface of the cylindrical body 1 in the case of FIG. 1 ). Also, the space required for bending and stretching each inter-notch portion 71 is reduced. This may contribute to, for example, miniaturization of the vacuum capacitor 1A and improved storage efficiency of each component.

[0065] The plurality of notches 61 formed in each corner 6 may have substantially the same shape (e.g., axial dimension) (including "equal"; the same applies hereinafter) and may be appropriately formed at a predetermined interval in the axial direction (hereinafter simply referred to as "axial interval"). Also, the axial interval of each notch 61 may be appropriately set so that the inter-notch portions 71 in each side wall portion 7 are positioned at substantially the same interval in the axial direction.

[0066] By forming each notch 61 in this manner, the inter-notch regions 71 in each side wall 7 have approximately the same elastic modulus. When the conductive wall 5 expands or contracts, the inter-notch regions 71 in each side wall 7 are likely to bend or stretch with approximately the same elastic force. Furthermore, although the elastic force of each inter-notch region 71 may act on non-inter-notch regions 72 located between the inter-notch regions 71 and on non-inter-notch regions 73 located on one axial side or the other axial side of the side wall 7, this is likely to be offset by approximately the same reaction force.

[0067] The number of notches 61 formed in each corner 6 is not particularly limited, but if the number is too large, it may increase the number of steps in the axial direction of the conductive wall portion 5 (the number of steps due to the portions 71 between the notches), increase the number of steps and complexity involved in processing the notches 61, and reduce the mechanical strength. For this reason, it is preferable to prevent the number of notches 61 from becoming too large. One example of this is to set the number of notches 61 to be less than the number of steps in the axial direction of the bellows 4.

[0068] Furthermore, the number of corners of the conductive wall portion 5 (i.e., the number of corners 6) is not particularly limited. For example, the more corners the conductive wall portion 5 has, the smaller the circumferential dimension of each side wall portion 7 can be, which may contribute to, for example, miniaturization of the vacuum capacitor 1A and improved storage efficiency of each component. However, if the number of corners of the conductive wall portion 5 is too large, as described above, it may increase the number of steps and complexity involved in processing the notch portion 61 and reduce mechanical strength, so it is preferable to set the number of corners appropriately.

[0069] As a specific example, assuming the shape, size, etc. of each component when vacuum capacitor 1A is applied to a general high-frequency device, the number of notches 61 formed in each corner 6 is preferably set to less than about 10, more preferably set to about 2 to 5. Furthermore, the number of corners of conductive wall portion 5 is preferably set to about 3 to 10, more preferably set to about 5 to 8.

[0070] When the inter-notch portions 71 of each side wall portion 7 bends and stretches, bending stress is likely to occur at both axial end sides of the inter-notch portions 71. For this reason, it is preferable to make the hardness of both axial end sides of the inter-notch portions 71 greater than the hardness of the axial center portion of the inter-notch portions 71, so that the bending stress occurring in the inter-notch portions 71 can be easily dispersed.

[0071] 3 and 4, for example, by forming elliptical cutouts 61 elongated in the axial direction at each corner 6, the central portion of the inter-cutout region 71 in the axial direction is made narrow. As a result, the cross-sectional area of ​​both end sides of the inter-cutout region 71 in the axial direction is larger than that of the central portion of the inter-cutout region 71 in the axial direction, and as a result, the hardness is increased. On the other hand, the central portion of the inter-cutout region 71 in the axial direction has a smaller elastic modulus and is more susceptible to elastic deformation.

[0072] It is also preferable that the non-notched portions 72, 73 which function as frames in each side wall portion 7 also have a high hardness, as described above.One example is to thicken the non-notched portions 72, 73 (for example, to about twice the thickness of the non-notched portion 71) by providing reinforcing portions (e.g., ribs, etc.) not shown in the figures in the non-notched portions 72, 73.

[0073] <Example of a method for forming the conductive wall portion 5> The conductive wall portion 5 is configured to be formed into a thin polygonal tube using a metal material (for example, a metal material such as copper or stainless steel (SUS), as well as various alloys (beryllium copper, etc.), and metal materials that have been subjected to various processing processes (copper plating, copper clad lamination, etc.)), and can be manufactured using various processing methods. One example is manufacturing the conductive wall portion 5 by appropriately processing a thin metal panel as shown in Figure 3 (when there are multiple notches 61 at each corner 6) or Figure 4 (when there is one notch 61 at each corner 6).

[0074] Specifically, for example, a thickness of 10 －２ mm (for example, 0.03 mm) to 10 －１A thin metal panel, approximately 1 / 4" thick, is prepared. This metal panel is then processed appropriately (shearing, bending, pressing, etc.) to form notches 61 at positions corresponding to the ridges of the intended conductive wall portions 5 (in FIG. 3, two notches 61 are formed at each corner 6). This allows the portions 71 between the notches of each side wall portion 7 of the metal panel to be convex in the thickness direction of the metal panel and elastically curve.

[0075] Then, by bending the metal panel at the ridge line position and joining the predetermined locations appropriately (for example, joining the both edge portions in the left and right directions in Figures 3 and 4 by welding, brazing, etc.), a polygonal cylindrical conductive wall portion 5 as shown in Figures 1 and 2 is formed.

[0076] 1 and 2 , an elastic body 8 that can expand and contract in the axial direction may be provided in the space 90 between the bellows 4 and the conductive wall 5 of the vacuum chamber 11. This elastic body 8 compensates for the elastic force when the inter-notch portions 71 of each side wall 7 bend and stretch. Even when the elastic body 8 is provided in this manner, high-frequency current flows more easily through the conductive wall 5 than through the elastic body 8 due to the skin effect.

[0077] For example, as shown in Figures 1 to 3, when multiple inter-notch portions 71 are formed in each side wall portion 7 and the conductive wall portion 5 has a multi-stage structure, an elastic body 8 may be provided corresponding to each stage as shown below.

[0078] First, a protruding wall portion 74 is provided in a middle wall portion of the conductive wall portion 5 located between each of the inter-notch portions 71 arranged in the axial direction (the middle wall portion located in the non-inter-notch portions 73 in FIGS. 1 to 4 ; hereinafter, appropriately referred to as the middle wall portion), protruding radially inward from the middle wall portion. The protruding wall portions 74 divide the space portion 90 into a plurality of sections of approximately equal dimensions in the axial direction. Then, an elastic body 8 that can expand and contract in the axial direction is disposed in each of the sections 9 thus divided (specifically, two sections 9a and 9b in FIG. 1 ; hereinafter, appropriately referred to as the section 9).

[0079] It is preferable that the elastic bodies 8 provided in each section 9 have approximately the same elastic modulus. As a result, when the conductive wall 5 expands or contracts, each elastic body 8 expands or contracts in the axial direction with approximately the same elastic force. In other words, approximately the same elastic force is supplied to each inter-notch region 71.

[0080] The protruding wall portion 74 may be configured to divide the space 90 as described above and appropriately support the elastic bodies 8 arranged in the adjacent sections 9. As an example, a flange-like configuration may be applied that protrudes radially inward from the inner peripheral surface of the middle wall portion and extends circumferentially along the inner peripheral surface.

[0081] The elastic body 8 may be stretchable in the axial direction in the space 90 (or in each of the plurality of divided sections 9). As an example, it may be made of a metal material (a spring material such as stainless steel or Inconel) having a wire diameter of about several mm (about 1 mm), and the metal material may be formed into a coil shape.

[0082] <Example of operation of vacuum capacitor 1A> In vacuum capacitor 1A, by moving the movable rod 32 in the axial direction using a drive source not shown, the amount of intersection between the fixed electrode 21 and the movable electrode 31 changes, and the capacitance is adjusted, thereby adjusting the impedance.

[0083] When a voltage is applied between the electrodes of the vacuum capacitor 1A to pass a high-frequency current, the high-frequency current flows along the following current path: the high-frequency current first flows through the fixed conductor 2 and the fixed electrode 21, and then flows to the movable electrode 31 via the capacitance between the two electrodes.

[0084] After this, the current can flow from the movable electrode 31 to the movable side conductor 3 via the movable electrode support part 30, bellows 4, movable rod 32, conductive wall part 5, and elastic body 8, but due to the skin effect, it will flow mainly via the conductive wall part 5 to the movable side conductor 3.

[0085] For example, in the case of a high frequency current of about 10 kHz, the extremely thin subsurface layer (thickness 10 －２This allows the amount of heat generated when electricity is applied to be sufficiently small.

[0086] <Another example of conductive wall portion 5> In the conductive wall portion 5, when the inter-notch portions 71 of each side wall portion 7 are caused to bend and extend so as to be curved convexly only radially inward, it may be configured as in the vacuum capacitor 1B shown in Figure 5, for example.

[0087] In this vacuum capacitor 1B, the portions 71 between the notches of each side wall 7 are bent and stretched so as to be convexly curved only radially inward, thereby enabling the conductive wall 5 as a whole to expand and contract in the axial direction, thereby achieving the same effects as those of the vacuum capacitor 1A.

[0088] Although the present invention has been described in detail above only with respect to the specific examples, it will be apparent to those skilled in the art that various modifications are possible within the scope of the technical concept of the present invention, and it is natural that such modifications fall within the scope of the claims.

[0089] 1A, 1B... vacuum capacitor, 10... vacuum container, 1a... cylindrical body, 21... fixed electrode, 31... movable electrode, 30... movable electrode support portion, 4... bellows, 5... conductive wall portion, 6... corner portion, 61... notch portion, 7... side wall portion, 71... portion between notch portions, 72, 73... portion between non-notch portions, 74... protruding wall portion, 8 (8a, 8b)... elastic body, 90... space portion, 9 (9a, 9b)... section portion

Claims

1. A vacuum vessel having a cylindrical body at least a portion of which is insulating, the fixed side being one axial side of the cylindrical body closed with a fixed conductor, and the movable side being the other axial side being closed with a movable conductor; a fixed electrode provided on one side of the vacuum vessel in the axial direction; a movable electrode support part located inside the vacuum vessel opposite the fixed electrode and movable in the axial direction; a movable electrode provided on one side of the movable electrode support part in the axial direction opposite the fixed electrode and forming a capacitance between it and the fixed electrode; a bellows having a cylindrical shape that is expandable and contractible in the axial direction between the movable electrode support part and the movable conductor, and supporting the movable electrode support part on the movable conductor; and a conductive wall part that is expandable and contractible in the axial direction and has a larger diameter than the bellows, is located coaxially on the outer periphery of the bellows, and is joined to the movable electrode support part and the movable conductor. a conductive wall portion having a plurality of corners located on each ridge line of the conductive wall portion in the axial direction and extending along each of the ridge lines, and a plurality of side wall portions located between each of the ridge lines in the circumferential direction of the conductive wall portion and extending in the axial direction, wherein each of the corners has a notch at a central portion in the axial direction that penetrates the conductive wall portion in the radial direction and extends in the axial direction, and wherein each of the side wall portions has a portion between a pair of notches that are opposed in the circumferential direction and that is curved convexly outward in the radial direction.

2. A vacuum vessel having a cylindrical body at least a portion of which is insulating, the fixed side being one axial side of the cylindrical body closed with a fixed conductor, and the movable side being the other axial side being closed with a movable conductor; a fixed electrode provided on one side of the vacuum vessel in the axial direction; a movable electrode support part located inside the vacuum vessel opposite the fixed electrode and movable in the axial direction; a movable electrode provided on one side of the movable electrode support part opposite the fixed electrode in the axial direction, forming electrostatic capacitance between the fixed electrode and the movable electrode support part; a bellows having a cylindrical shape that is expandable and contractible in the axial direction between the movable electrode support part and the movable conductor, and supporting the movable electrode support part on the movable conductor; and a conductive wall part that is expandable and contractible in the axial direction, has a larger diameter than the bellows, is located coaxially on the outer periphery of the bellows, and is joined to the movable electrode support part and the movable conductor, a conductive wall portion having a plurality of corners located on each ridge line of the conductive wall portion in the axial direction and extending along each of the ridge lines, and a plurality of side wall portions located between each of the ridge lines in the circumferential direction of the conductive wall portion and extending in the axial direction, wherein each of the corners has a notch at a central portion in the axial direction that penetrates radially through the conductive wall portion and extends in the axial direction, and wherein each of the side wall portions has a portion between a pair of notches that are opposed in the circumferential direction, and the portion between the notches is curved convexly inward in the radial direction.

3. A vacuum capacitor according to claim 1 or 2, wherein each of said corners has a plurality of said notches formed at predetermined intervals in the axial direction.

4. A vacuum capacitor according to claim 1 or 2, characterized in that an elastic body extending in the axial direction and capable of expanding and contracting in the axial direction is provided between the bellows and the conductive wall portion.

5. A vacuum capacitor as described in claim 3, characterized in that the conductive wall portion has a middle wall portion located between the respective notched portions aligned in the axial direction, and a protruding wall portion protruding radially inward from the middle wall portion, the protruding wall portion dividing the space between the bellows and the conductive wall portion into sections of approximately equal dimensions in the axial direction, and each divided section is provided with an elastic body that is stretchable in the axial direction and has approximately equal elastic modulus.

6. A vacuum capacitor according to claim 1 or 2, characterized in that the hardness of the non-inter-notch portions, i.e., the portions of each side wall other than the portions between the notches, is greater than the hardness of the portions between the notches.

7. A vacuum capacitor according to claim 6, characterized in that a reinforcing portion is provided in the area between said non-cutout portions.

8. A vacuum capacitor according to claim 1 or 2, characterized in that the cross-sectional area of ​​the portion between the notches on both end sides in the axial direction is larger than the cross-sectional area of ​​the portion between the notches at the center in the axial direction.

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