JPH0697596B2 - Structure of ceramic airtight junction of electron tube - Google Patents

Description

Description: TECHNICAL FIELD OF THE INVENTION The present invention relates to an improvement in a ceramic airtight joint structure of an electron tube.

[Technical Background of the Invention and Problems Thereof] For example, high-frequency electron tubes such as a high-power multi-cavity klystron, a traveling wave tube, a gyrotron, a high-power magnetron, and a high-power transmitter tube have electron gun parts and resonance cavity parts thereof The cathode support portion, the high frequency output portion, and the like have a joint portion between the ceramic cylindrical body and the metal support plate. In many cases, such a ceramic cylinder is provided in a portion that insulates high voltage or a portion through which high frequency power is passed. For example, the high-frequency output section of a high-power multi-cavity klystron is conventionally configured as shown in FIG. In the figure, reference numeral 11 is an output cavity, 12 and 13 are drift tubes, 14 is a cavity wall, 15 is a collector portion, 17 is an output coaxial line, 18 is an inner conductor thereof, 18a is an inner conductor tip portion, and 18b is a loop coupling. , 19 is an outer conductor, 20 is a ceramic cylinder, 21 and 22 are metal support plates that are airtightly joined to both open ends of the ceramic cylinder, and 23 and 24 are the airtightness of the ceramic cylinder and the metal support plate, respectively. The joint portion, 25, represents a rectangular waveguide. In this way, the output coaxial line is converted into a rectangular waveguide at a high frequency for use.

Now, as shown in an enlarged view of one of the airtight joints, the first thin-walled sealing metal ring 26 is airtightly brazed at the brazing portion B to the open end surface of the alumina ceramic cylindrical body 20 and folded back in a U-shape. In addition, the other end is extended outward. On the back surface of the first sealing metal ring 26, a spacer ring 27, which is commonly called a backup ring and is made of ceramic of the same quality, is brazed and fixed. The back surface of the spacer ring 27 is held in an annular recess 21a formed in the metal supporting plate 21. On the outer peripheral side of the annular recess 21a of the metal supporting plate, a second sealing metal ring 28 made of thin metal is airtightly brazed. The first and second sealing metal rings 26 and 28 are partly face-to-face with each other and arc-welded, as indicated by the symbol A, at the outer peripheral end on the atmosphere side. A discharge prevention ring 29 is fixed to the inner peripheral portion of the annular recess 21a of the metal supporting plate, and a discharge prevention ring 30 is also fixed to the waveguide 25. Then, they are joined by a fixing flange 31. These metal supporting plate 21, first and second sealing rings 26,
Vacuum tightness is maintained by 28 and the ceramic cylinder 20. The spacer ring 27 has a function of relieving and protecting the stress at the brazing portion between the first sealing ring 26 and the ceramic cylindrical body 20.

By the way, in the operation of the microwave tube, a high frequency current flows in the vicinity of the airtight junction as shown by an arrow. Therefore, a problem is that the inner surfaces of the welded portions of the first and second sealing rings 26 and 28 are aligned with each other at a slight interval, and therefore high frequency discharge is likely to occur at these portions. This is of little concern if the high frequency power is relatively small,
It cannot be ignored in a high power microwave tube of several hundred kw or more. If discharge occurs at such a portion, the brazing portion between the sealing ring and the ceramic material may be damaged due to local heat generation of the sealing ring.

Such an airtight junction structure and a phenomenon caused thereby are not limited to the output part, and are disclosed in, for example, Japanese Utility Model Application Laid-Open No. 59-16057, in which a metal supporting plate and a ceramic cylindrical body in an external cavity type resonator are connected to each other. A similar phenomenon may occur at the brazing portion.

[Object of the Invention]

The present invention solves the above-mentioned inconvenience, and further reliably suppresses high-frequency discharge at the airtight joint between the ceramic cylinder and the metal support plate even at high power operation, and provides a stable operation of the high-frequency electron tube ceramic cylinder. An airtight joint structure is provided.

[Outline of Invention]

The present invention relates to a ceramic cylindrical body that is hermetically joined to a metal supporting plate and transmits high frequencies, a first sealing metal ring that is hermetically brazed to its end surface, a ceramic spacer ring that is brazed and fixed to this back surface portion, and a metal. A second sealing metal ring, which is airtightly bonded to the support plate and partially bonded to the first sealing metal ring, is airtightly bonded on the atmosphere side, and the first sealing metal ring supports the metal on the vacuum region side. A ceramic airtight junction structure of a high-frequency electron tube, which is electrically short-circuited with a plate and shields a space including a spacer ring from a space inside a ceramic cylinder in a high frequency manner.

As a result, a high-frequency current does not flow between the inner surfaces of a plurality of sealed metal rings that are airtightly joined to the metal support plate and partly face-to-face and airtightly joined on the atmosphere side, and a high-frequency discharge occurs there. The risk of Therefore, stable and reliable operation can be obtained.

Example of Invention

An embodiment will be described below with reference to the drawings. The same parts are represented by the same symbols.

The embodiment shown in FIG. 1 is applied to airtight joints 23 and 24 between a disk-shaped metal supporting plate fixed to the outer conducting end of the output coaxial line 17 and a ceramic cylindrical body 20. As shown in the enlarged view of one of the figures, a first sealing ring 26 in which a ceramic cylindrical body 20 and a ceramic spacer ring 27 of the same quality for backup are brazed on both sides at a brazing portion B
Is bent in a substantially U-shape on the inner peripheral side thereof, that is, on the inner side of the ceramic cylindrical body. This inner circumference 26
a covers the inner peripheral surface of the spacer ring 27, and the bent end 2
6b extends to the back surface of the spacer ring 27. Then, it is brought into contact with the surface of the annular recess 21a of the metal supporting plate 21. Further, a number of slits 26c parallel to the tube axis direction are formed in the U-shaped inner peripheral portion 26a, and the spacer ring 27
Also, electrical contact with the ventilation hole for exhausting the outer peripheral space S to a vacuum and the metal supporting plate is improved. The slit 26c has a cut-off size that hardly transmits an electromagnetic field having an operating fundamental frequency.

With such a structure, when the inside becomes a vacuum state, the ceramic cylinder body and the bent end portion 26b of the first sealing metal ring 26 are strongly pressed against the metal supporting plate surface by the atmospheric pressure to maintain a reliable electrical contact. Be done. The high-frequency current during operation flows only on the upper surface side of the first sealing metal ring 26 as indicated by the arrow, and hardly flows on the rear surface side, that is, the surface of each metal member in the space S where the spacer ring is located. Therefore, there is no possibility of high frequency discharge occurring at the inner surface mating portion of the welded portion A of the first and second sealing metal rings. Further, since no high-frequency current flows in the brazing portion between the first sealing ring 26 and the ceramic spacer ring 27, the fear of damage to the brazing portion is eliminated.

In such a structure, the first sealing metal ring 26 is
As shown in the figure, the slits 26c are formed and bent. Next, as shown in FIG. 3, the ceramic spacer ring 27 is fixed to the back surface by brazing like the brazing portion B. Then, as shown in FIGS. 4 and 5, the inner peripheral end portion 26b of the sealed metal ring is bent to the back surface side of the spacer ring 27. The sealing metal ring 26 may be brazed to the spacer ring after the inner peripheral portion thereof is bent into a U shape as shown in FIG. After configuring like this,
The open end surface of the ceramic cylindrical body 20 is brazed to the upper surface of the flat portion from the first sealing metal ring 26. On the other hand, the second sealing metal ring 28 is brazed to the metal supporting plate, and by combining these, the outside air side ends of the face-to-face portions of both sealing metal rings are vacuum-tightly joined by heliarc welding over the entire circumference. . In this way, the joint is completed.

In the embodiment shown in FIG. 6, an inverted U-shaped portion 26d is formed on the inner peripheral portion of the first sealing metal ring 26. As a result, high-frequency discharge inside the ceramic cylindrical body 20 can be reliably prevented.

The embodiment shown in FIG. 7 has an inner peripheral portion of the first sealing metal ring 26.
26a is provided with a spring force acting in the direction of arrow P, and the inner peripheral surface thereof is press-fitted into the inner peripheral wall surface of the concave portion of the metal supporting plate 21 to make electrical contact. According to this embodiment, the parts can be processed more easily, and the same discharge prevention effect as in the above-mentioned embodiments can be obtained.

The portion of the inner peripheral portion of the first sealing metal ring that electrically contacts the metal support plate may be electrically and mechanically joined by brazing or the like.

〔The invention's effect〕

As described above, according to the present invention, a high-frequency wave is applied between the inner surfaces of a plurality of sealed metal rings that are partially air-tightly joined to each other for airtightly joining the metal supporting plate and the ceramic cylindrical body and are airtightly joined on the atmosphere side. No current flows, and there is no possibility of high-frequency discharge occurring there. Therefore, stable and reliable operation can be obtained.

[Brief description of drawings]

FIG. 1 is a longitudinal sectional view of an essential part showing an embodiment of the present invention.
FIG. 5 to FIG. 5 are semi-longitudinal sectional views and bottom views of essential parts showing the procedure for assembling the parts, FIG. 6 and FIG. 7 are sectional views of essential parts showing other embodiments of the present invention, and FIG. It is a principal part longitudinal cross-sectional view which shows a structure. 20 …… Ceramic cylinder, 21 …… Metal support plate, 23 , 24 ……
Airtight joint, 26 ... First sealing metal ring, 27 ... Spacer ring, 28 ... Second sealing metal ring, 26c ... Slit, A ... Welding, B ... Brazing joint.

Claims (3)

[Claims] 1. A first support member comprising a metal supporting plate through which a high-frequency current flows, a ceramic cylindrical body hermetically bonded to the metallic supporting plate and transmitting a high frequency, and a thin-walled metal hermetically brazed to an opening end surface of the ceramic cylindrical body. Sealed metal ring and this 1st
A ceramic spacer ring, which is brazed and fixed to the back surface of the ceramic cylindrical joint portion of the sealing metal ring and mechanically held by a part of the metal supporting plate, and the metal support plate on the outer peripheral side of the spacer ring. A ceramic airtight junction structure for an electron tube, comprising: a second airtight metal ring that is airtightly joined to the first airtight metal ring and is partially face-to-face and airtightly air-tightly joined to the atmosphere side. The first sealing metal ring, which is airtightly brazed to the ceramic cylinder, electrically short-circuits the metal supporting plate on the vacuum region side and shields the space including the spacer ring from the space inside the ceramic cylinder in a high frequency manner. A ceramic airtight joint structure for an electron tube, which is characterized in that 2. The electron tube according to claim 1, wherein the first sealing metal ring covers the inner peripheral surface of the spacer ring, extends to the bottom surface, and is electrically contacted with the metal supporting plate surface. Ceramic hermetic joint structure. 3. The ceramic hermetic joint portion of the electron tube according to claim 1, wherein the first sealing metal ring has a plurality of slits formed in a portion electrically contacting the metal supporting plate. Construction.