JPH0315291B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a magnetron cathode structure in which deformation of a helical filament is suppressed.

As shown in Fig. 1, the cathode of a conventional magnetron is generally made by inserting a short cylindrical convex part 3 of an upper end shield 2 into one end of a helical filament 1 made of thorium tungsten, and brazing it to the helical filament 1. Then, the other end of the helical filament 1 is inserted into the short cylindrical recess 5 of the lower end shield 4 and brazed thereto. Then, the head of the center support 6 is welded to the upper end shield 2, and the head of the side support 7 is welded to the lower end shield 4. The upper and lower end shields 2 and 4, the center support 6, and the side supports 7 are made of a high melting point metal such as molybdenum, and the short cylindrical convex portion 3 and the short cylindrical recess 5 are connected to the helical filament 1 and the upper and lower ends. To facilitate alignment of the shields 2 and 4 when brazing them together. However, the height of the short cylindrical convex part 3 and the short cylindrical concave part 5 is usually set to about 1.3 mm in order to ensure the effective length of the helical filament 1 and avoid a decrease in the electron emission area, and furthermore, Contact portions 8 and 9 at both ends of the helical filament 1 of the end shields 2 and 4 are perpendicular to the central axis of the cathode. Therefore, when the ends of the helical filament 1 are brazed to the upper and lower end shields 2 and 4, the filament tends to tilt due to the repulsive force of the helical filament's own weight, and the high temperature heating or magnetron operation during the brazing process tends to occur. The entire filament is deformed due to the heat generated during the process. As a result, the current density of the thermoelectrons emitted from the cathode is not uniform, making the operation of the magnetron unstable.

The purpose of the present invention is to prevent the above-mentioned defects from occurring.
That is, the object of the present invention is to provide a magnetron cathode structure that prevents deformation of the helical filament and allows stable microwave oscillation operation.

In order to achieve the above object, in the present invention,
At least one of the upper and lower end shields is provided with a threaded slope portion or an uneven portion corresponding to the helix of the filament, the end of the helical filament is brought into engagement contact with these portions, and this engaging portion is further brazed or It was fixed by welding.

FIG. 2 shows an embodiment of the present invention, and FIG. 3 shows upper and lower end shields according to the present invention, and figures a and b respectively show the upper and lower end shields for the embodiment shown in FIG. Figures 10 and 13, Figures c and d are for use in other embodiments, as well as lower end shields 10',
Fig. 13'. In the embodiment shown in FIG. 2, the lower end shield 13 has a threaded slope portion 12 corresponding to the helix of the filament 1 on the outer periphery of the short cylindrical convex portion 11 of the upper end shield 10 (FIG. 3 a).
A threaded inclined surface 15 corresponding to the helix of the filament 1 is provided on the inner periphery of the short cylindrical recess 14 (FIG. 3b). The end of the helical filament 1 is
Since the helical filament 1 is in engagement contact with the slope portions provided on the end shield, the repulsive force of the helical filament 1 due to its own weight is reduced, the helical filament 1 is difficult to tilt, and no deformation occurs due to high temperature heating during brazing work. FIGS. 3c and 3d show upper and lower end shields 10' and 13' used in other embodiments, respectively. A threaded concave and convex portion 15' is provided on the inner periphery of 14'. It is obvious that such an end shield prevents the filament 1 from being deformed. Although the shape of the end shield according to the present invention is slightly more complicated than that of the conventional end shield, conventionally, at least for mass production, the final shape has been made directly by powder metallurgy, which increases manufacturing costs. do not. On the other hand, conventionally the engagement part between the filament end and the end shield was set to 1.3 mm, for example, but by implementing the present invention, 1.0 mm is sufficient because the engagement is reliably and effortlessly carried out. The amount of thorium tungsten wire used for filaments and molybdenum powder used for end shield molding is reduced, resulting in savings in these raw materials during mass production.

As explained above, according to the present invention, deformation of the filament is prevented, thermoelectrons are emitted at a uniform current density into the so-called working space around the filament, and stable magnetron operation is performed.Moreover, the upper and lower end shields Even if the length of the short cylinder part is shortened, deformation of the filament can be prevented and the effective length of the cathode can be easily secured.

[Brief explanation of drawings]

Figure 1 is a diagram showing the cathode structure of a conventional magnetron, Figure 2 is a diagram of an embodiment of the present invention, Figure 3a is a diagram of the upper end shield of the same embodiment, and Figure b is a diagram of the lower end of the same embodiment. Diagram of the shield, Figure c is a diagram of the upper end shield used in another embodiment of the invention, Figure d
is a diagram of the lower end shield of the embodiment. 1...Helical filament, 10,10'...
...Upper end shield according to the present invention, 11,1
1'...Short cylindrical convex part, 12...Threaded slope part, 1
2'... Threaded uneven portion, 13, 13'... Lower end shield according to the present invention, 14, 14'... Short cylindrical recessed portion, 15... Threaded sloped portion, 15'... Threaded uneven portion .

Claims (1)

[Claims] 1 a helical filament, and an upper part that supports this helical filament at its upper and lower ends, respectively;
In a magnetron cathode structure having a lower end shield, and a center support and a side support that serve as supporting and conductive members for these end shields, the upper end shield is formed with male thread-shaped unevenness corresponding to the helix of the filament. , the lower end shield is formed with a female thread-like unevenness corresponding to the helix of the filament, and the end of the filament is screwed into engagement with the upper end shield and the lower end shield. Further, in the two engaging portions, the filament and the upper portion are fixed by brazing or welding.