JPH0156496B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (a) Field of Industrial Application The present invention relates to a magnetron, and more particularly to a sealing structure for a cathode support rod.

(B) Prior Art Conventionally, a cathode support rod for supplying heating power to a cathode filament placed in a vacuum container is led out from the vacuum container as shown in FIG. 1st
In the figure, 1 and 1 are a pair of cathode support rods that are connected to a directly heated cathode filament (not shown), and the cathode support rods 1 and 1 are at high temperatures due to heat conduction from the cathode filament when the magnetron is in operation. Therefore, it is made of an expensive high-melting point metal such as molybdenum (Mo). Reference numeral 2 denotes a cathode insulator made of alumina ceramic or the like, through which the pair of cathode support rods 1, 1 are inserted in the axial direction of the insulator 2 and extend out of the vacuum vessel. 3, 3 is a first sealing metal that hermetically seals the insertion portion of the cathode support rods 1, 1 on the outer surface of the cathode insulator 2 by brazing; 4, the one open end 5 is sealed above; A second sealing metal 4 is hermetically sealed by brazing similarly to the first sealing metals 3, 3, and the other open end of the second sealing metal 4 is connected to a vacuum container (not shown). There is.

(C) Problems to be Solved by the Invention By the way, the first and second sealing metals 3 and 4 are brazed to the cathode insulator 2 as described above, but it is difficult to braze them directly to the cathode insulator 2. This problem is dealt with by forming a metallized layer in advance at that location.

However, according to such a structure, the metallized layer of the cathode insulator 2 must be formed on both surfaces facing the first sealing metal 3 and the second sealing metal 4, respectively. Usually, the metallized layer is formed on one side by printing, which results in very poor workability. Also, the first
Since the first sealing metal 3 to be brazed to the metallized layer is exposed to the atmosphere, in order to obtain a predetermined withstand voltage between the second sealing metal 4, it must be long in order to increase the creepage distance. I had to. In other words, in the atmosphere, for example, if the withstand voltage is 10KV, the creepage distance is 10 to 15mm.
is necessary. Therefore, the magnetron itself becomes larger and the cathode support rods 1, 1 are also longer, which poses problems in terms of cost and vibration and shock resistance.

(d) Means for Solving the Problems The present invention has been made to solve the above problems, and includes a vacuum vessel, a cathode filament placed in the vacuum vessel, and a pair of cathode filaments that support the cathode filament. A cathode support rod, a cathode insulator that supports the support rod, a first sealing metal that seals the pair of cathode support rods to the cathode insulator, and seals the open end of the vacuum vessel together with the cathode insulator. a second sealing metal; a first brazing surface for brazing the cathode insulator and the first sealing metal; It consists of a second brazing surface that performs brazing with the sealing metal, and a non-brazing surface separated from the first and second brazing surfaces, and the first and second brazing surfaces are arranged at approximately the same height. It has a flat surface and a metallized layer is formed on the surface.

(d) Effect The brazed parts between the first and second brazed surfaces (metallized layers) and the first and second sealing metals will be placed in a vacuum, and when obtaining the same withstand voltage of 10Kv, The creepage distance can be as small as approximately 0.5mm.
Furthermore, since the first and second brazed surfaces are constructed as flat surfaces having approximately the same height, and the non-brazed surface is separated from the brazed surface, a metallized layer is formed on the first and second brazed surfaces. It's easy to do.

(F) Embodiment An embodiment of the present invention will be described with reference to FIGS. 2 and 3.

10, 10 are a pair of cathode support rods made of molybdenum (Mo), etc., and 11 are the cathode support rods 10, 10.
Top hat 12 and end hat 1 between both ends of
Thermionic electrons are emitted by the cathode filament held between the cathode filaments 3 and 3 by receiving power from the cathode support rods 10, 10. 14 is a highly heat-resistant cathode insulator made of alumina ceramic or the like, and the cathode support rods 10, 10 are inserted into a pair of insertion holes 19, 19. 15 is the cathode support rod 1
16 is a second sealing metal that seals the open end of the vacuum container together with the cathode insulator 14;
6 is brazed to the same surface of the cathode insulator 14 on the vacuum vessel side.

Reference numerals 17 and 17 denote the surface of the cathode insulator 14 on the vacuum vessel side, and the insertion holes 1 of the pair of cathode support rods 10 and 10.
9, 19 is the first brazing surface formed on the periphery; 18 is the first brazing surface;
A second brazing surface 21 is formed on the outer periphery of the insulator 14 surface which is the same as the brazing surfaces 17, 17, and 21 is a non-brazing surface formed on the insulator 14 surface other than the first and second brazing surfaces 17, 17, 18. The brazing surface is separated from the first and second brazing surfaces. The first brazing surface 17, 17 and the second brazing surface 1
8 are constructed as flat surfaces having approximately the same height. Then, a metallized layer is formed on the surface of the insulator 14 by printing molybdenum (Mo) or manganese (Mn) by screen printing or the like. 18
Since the non-brazed surface 21 is separated from the first and second brazed surfaces, it is not printed;
A metallized layer is formed only on the brazed surfaces 17, 17, 18. After printing, a drying and firing process is performed, and nickel (Ni) plating is applied to further improve brazing, completing the metallized layer.

The insulator 1 has a pair of cathode support rods 10, 10 sealed by brazing a first sealing metal 15 to the metallized layer formed on the first brazing surfaces 17, 17.
Supported by 4. A second sealing metal 16 for sealing the open end of the vacuum vessel is brazed to the metallized layer formed on the second brazing surface 18.

An annular projecting wall 20 is formed on the outer periphery of the opposite surface of the insulator 14 to cover the cathode support rods 10, 10, and maintains a creeping distance in the atmosphere.

(g) Effect Brazing the surface of the cathode insulator on the vacuum vessel side with the cathode insulator and the first sealing metal; brazing the first brazing surface with the cathode insulator and the second sealing metal; It consists of a second brazed surface and a non-brazed surface separated from the first and second brazed surfaces, and the first and second brazed surfaces are flat surfaces with approximately the same height, so metallization is possible. The layers can be formed at the same time, improving workability, and since the brazed parts of the first and second sealing metals are placed in a vacuum, high withstand voltage can be obtained with a small creepage distance. The cathode insulator 14 is an industrially valuable invention, as it can be made smaller and the expensive cathode support rod can be made shorter.

[Brief explanation of drawings]

FIG. 1 is a sectional view showing the main part of the conventional example, FIG. 2 is a partial sectional view showing the main part of the present invention, and FIG. 3 is a front view showing the main part of the present invention. 10... Cathode support rod, 11... Cathode fillant, 1
4... Cathode insulator, 15... First sealing metal, 16... Second sealing metal, 17... First brazing surface, 18... Second brazing surface.

Claims (1)

[Claims] 1. A vacuum container, a cathode filament placed in the vacuum container, a pair of cathode support rods that support the cathode filament, a cathode insulator that supports the support rods, and the pair of cathode supports for the cathode insulator. a first sealing metal that seals the rod; a second sealing metal that seals the open end of the vacuum container together with the cathode insulator;
a first brazing surface for brazing the cathode insulator and the first sealing metal on the surface of the cathode insulator on the vacuum vessel side; and a first brazing surface for brazing the cathode insulator and the second sealing metal. It is composed of a second brazed surface on which brazing is performed, and a non-brazed surface separated from the first and second brazed surfaces, and the first and second brazed surfaces are flat surfaces having approximately the same height. A magnetron is characterized by having a metallized layer formed on its surface.