JP3245930B2 - Manufacturing method of vacuum capacitor - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of manufacturing a vacuum capacitor used in an oscillation circuit, an amplifier circuit, a tank circuit of an induction heating device or the like of a high power transmitter, and more particularly to a method of manufacturing a variable vacuum capacitor. .

[0002]

2. Description of the Related Art High voltage and current ratings, tuning ratios,
In recent years, vacuum capacitors have been used for large power capacitors because of their excellent self-healing properties.

FIG. 3 is a cross-sectional structural view of a conventional general-purpose variable vacuum capacitor. For example, a side portion is formed of a ceramic 12 having copper flanges 11a and 11b at both ends, and the side portion is fixed conductor. A vacuum container 10 for filling a high-yield vacuum dielectric by being closed and joined with the metal cover 13 and the metal cover 14 is formed.

A plurality of substantially cylindrical electrode plates having different inner diameters are provided concentrically at a fixed interval inside the fixed conductor 13 to form the fixed electrode 15. The movable electrode 16 is formed by providing a plurality of cylindrical electrode plates having different inner diameters so that they can be inserted and removed in a contact state. The movable electrode 16 is attached to a movable conductor 18 slidable along a bearing 17.

Reference numeral 19 denotes a bellows made of a soft metal having elasticity. One end of the bellows is provided on the inner wall of the lid 14 so that the movable conductor 18 (movable electrode 16) can move up and down while keeping the inside of the vacuum vessel 10 airtight. The edge is joined, and the other end is joined to the back surface of the movable conductor 18 or the side surface of the support. The bellows 19 also serves as a current path between an external power supply terminal (not shown) provided on the lid 14 and the movable electrode 16 in addition to the vacuum seal.

When adjusting the capacitance of a vacuum capacitor having such a structure, the movable conductor 18 is slid to change the crossing area between the fixed electrode 15 and the movable electrode 16 to generate a voltage between the two electrodes. The value of the capacitance is continuously changed.

In a vacuum capacitor, since the dielectric material is in a vacuum, the loss is low. However, since it is normally used in a high frequency band, the material of the bellows 19 is Cu, which has excellent conductivity.
It was necessary to select an alloy or the like containing Sn and P as main components.

Further, when manufacturing a vacuum capacitor having the above structure, the joining of the respective parts is usually performed by brazing. However, the adverse effect of vaporizing the brazing material, for example, brazing between the movable conductor 18 and the bearing 17 is required. To prevent this, the brazing atmosphere must be Ar or N ₂ gas and brazing must be performed at a pressure of 10 [Pa] or more.

For this reason, in the manufacturing process of the vacuum capacitor, for example, an exhaust pipe 20 is provided on a fixed conductor, and after brazing, gas is exhausted from the exhaust pipe 20 and 400 to 600 [deg. ° C], and after cooling, the exhaust pipe 20 was pinched.

[0010]

As described above, according to the conventional method for manufacturing a vacuum capacitor, at least a complicated evacuation step is required in addition to the brazing step. In addition, since the outer surface is oxidized during heating during degassing, it is necessary to remove oxide scale. In this case, the movable conductor 18 and the bearing 17 are also on the outer surface, but it is desirable to prevent the adhesion of the oxide scale itself in order not to deteriorate the slidability of the two. Movable conductor 1
It was necessary to sufficiently shield the space between the bearing 8 and the bearing 17 from the atmosphere.

[0011] Therefore, in the conventional method, the manufacturing process becomes complicated, and there is a limit in improving the productivity and reducing the cost.

The present invention has been made under such a background, and an object of the present invention is to provide a method of manufacturing a vacuum capacitor capable of simplifying and simplifying steps.

[0013]

In order to achieve the above object, the construction of the present invention is such that the opening surface of the cylindrical conductor is closed and joined with a fixed conductor to form an end portion of the container, and further, between the container forming members and between the container forming members. In a method of manufacturing a vacuum capacitor for brazing each joint between internal members, an exhaust hole is formed in the fixed conductor, and a pressure of at least 10 [Pa] is applied to each joint in an oxygen-free atmosphere. A first brazing step for brazing, and a second brazing step for brazing a joint between the plug closing the exhaust hole and the fixed conductor in a vacuum after the first brazing step. And characterized in that:

More specifically, at least the surface portions of the fixed conductor and the plug are made of copper, and in the second brazing step, 20-30 [Wt%] of In and the balance are Cu, A brazing material made of an Ag alloy, or 15-
Using a brazing material made of an alloy of 25 [Wt%] Sn and the balance of Cu and Ag, brazing is performed in a vacuum of 0.001 [Pa] or less and at a temperature not exceeding 700 [° C].

[0015]

After the main structure of the vacuum capacitor is formed in the first brazing step, the second brazing step is performed in a vacuum, so that the inside of the container is kept in a vacuum without providing an evacuation step after the brazing. It is. Also, the second brazing step is performed at 700
By performing the heating at a temperature of [° C.] or less, vaporization of the brazing material is prevented.

[0016]

Embodiments of the present invention will be described below. Since the present invention is an improvement of the conventional manufacturing method, the structure of the vacuum capacitor as a finished product will be described using the reference numerals shown in FIG.

This embodiment eliminates the conventional evacuation process and manufactures a vacuum capacitor by processing the fixed conductor 13 and performing two brazing processes.

More specifically, the exhaust hole 1 is formed in the fixed conductor 13 and, as a first brazing step, as shown in FIG. To f in an oxygen-free atmosphere at least 10 [Pa]
And then brazing. To make the atmosphere oxygen-free, for example, an Ar gas or a N ₂ gas is filled, and an alloy containing Cu, Ag, and Sn as main components is used as the brazing material. Thus, first, the main structure of the vacuum capacitor is completed.

Next, a second brazing step is performed. In this step, after completing the main structure of the vacuum capacitor, the plug 2 for closing the exhaust hole 1 is brazed to the fixed conductor 13 as shown in FIG. At this time, the fixed conductor 13 and the plug 2
And at least the surface portion is made of copper, and
A brazing material made of an alloy of 0 [Wt%] In and a balance of Cu and Ag, or a brazing material made of an alloy of 15 to 25 [Wt%] Sn and a balance of Cu and Ag is used.
It is brazed in a vacuum of [Pa] or less and at a temperature not exceeding 700 [° C.]. Thereby, the inside of the container 10 is kept in a vacuum after brazing.

The copper fixed conductor 13 and the plug 2 may be used from the beginning. Further, the shape of the plug 2 may be a blind plate shape.

When the second brazing step is performed at a temperature not exceeding 700 ° C., when the temperature becomes higher, the Cu—Ag—Sn component of the brazing material used in the first brazing step is vaporized. This is because this enters into the minute gap between the bearing 17 and the movable conductor 18 and is joined, so that 0.00
The reason why the treatment is performed in a vacuum of 1 [Pa] or less is to keep the inside of the container 10 in a vacuum state after brazing.

The reason why at least the surface portions of the fixed conductor 13 and the plug 2 are made of copper and the brazing material used is limited is as follows.

That is, high vacuum (less than 0.001 [Pa])
Medium and at a temperature of 700 ° C. or lower, Zn—Cd
-P or the like containing a high vapor pressure component is not applicable, so it is limited to a brazing material made of a Cu-Ag-In-based or Cu-Ag-Sn-based alloy. Ag-15In, Cu-Ag-10Sn, that is,
A brazing material containing 15 [Wt%] In and 10 [Wt%] Sn requires a brazing temperature of 750 [° C] or more and cannot be applied.

Therefore, in order to further lower the melting point, Cu-
In a brazing material made of an Ag-In-based or Cu-Ag-Sn-based alloy, the content of In is 20 to 30 [Wt%],
Alternatively, a material having a Sn content of 15 to 25 [Wt%] is applied.

[0025] Of these brazing materials, those having an In content of 20 to 30 [Wt%] cannot be brazed with phosphor bronze or ceramic (metallized and copper ring). , Sn content is 15 to 25 [Wt]
%] Cannot be brazed with ceramics (metallized and copper rings). On the other hand, both brazing of copper and copper is possible. Therefore, the surface of the joint between the fixed conductor 13 and the plug 2 is made of at least copper.

[0026]

As described above, according to the present invention, an exhaust hole is formed in a fixed conductor, brazed in the same manner as in the prior art to form a main structure of a vacuum capacitor, and then the exhaust hole is formed. Since the joint between the plug to be closed and the fixed conductor is brazed in a vacuum, the inside of the container can be kept in a vacuum without providing an evacuation step. Therefore, there is no need for overheating at the time of evacuation, an operation of removing oxide scale on the outer surface, or an operation of shielding from the atmosphere, which has an effect of greatly simplifying the manufacturing process.
Thereby, productivity can be improved and manufacturing cost can be reduced.

Further, by forming at least the surface of the exhaust hole and the fixed conductor with copper, a low melting point brazing material,
It is possible to use a brazing material composed of an alloy of 30 [Wt%] In and the balance of Cu and Ag, or a brazing material composed of an alloy of 15 to 25 [Wt%] Sn and a balance of Cu and Ag. Since the brazing at the time of closing the hole can be performed in a vacuum of 0.001 [Pa] and at a temperature of 700 [° C.] or less, there is an effect that vaporization of the brazing material is prevented.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram of a first brazing step in one embodiment of the present invention.

FIG. 2 is an explanatory view of a second brazing step in the embodiment.

FIG. 3 is a sectional structural view of a vacuum capacitor to which the present invention is applied.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Exhaust hole part, 2 ... Plug body, 10 ... Vacuum container, 11a, 1
1b: flange, 12: ceramic, 13: fixed conductor,
14 ... lid, 15 ... fixed electrode, 16 ... movable electrode, 17 ...
Bearings, 18: movable conductor, 19: bellows, 20: exhaust pipe, a to f: joints.

Claims (3)

(57) [Claims] 1. A method of manufacturing a vacuum capacitor in which an opening surface of a cylindrical conductor is closed and joined with a fixed conductor to form an end of a container, and furthermore, each joint between a container forming member and a container inner member is brazed. Forming an exhaust hole in the fixed conductor, and forming each joint at least one in an oxygen-free atmosphere.
A first brazing step in which a pressure of 0 [Pa] is applied and brazing; and a joining portion between the plug closing the exhaust hole and the fixed conductor in a vacuum after the first brazing step. A second brazing step of brazing. 2. The fixed conductor and at least the surface of the plug body are formed of copper, and the second brazing step is performed in a range of 20 to 30 [Wt%] of In, and the balance is Cu, Ag.
2. The method of manufacturing a vacuum capacitor according to claim 1, wherein the brazing is performed in a vacuum of 0.001 [Pa] or less and at a temperature not exceeding 700 [° C.] using a brazing material made of the alloy of (1). Method. 3. The method of manufacturing a vacuum capacitor according to claim 2, wherein said brazing material containing In is replaced with 15%.
A method for manufacturing a vacuum capacitor, comprising using a brazing material made of an alloy of Sn and Cu and Ag with the balance being up to 25 [Wt%].