JPH0552011B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to an electron tube cathode assembly, and more particularly to the structure of an end shield that supports both ends of a helically wound thermionic emission filament.

[Background of the Invention] FIG. 1 is a sectional view showing an example of a cathode assembly of a magnetron, for example, as a conventionally used electron tube cathode assembly. In the figure, a helical filament 1 that emits thermionic electrons is placed concentrically with the tube axis of the magnetron, and is placed between an upper end shield 2 and a lower end shield 3 that prevent thermionic electrons from deviating toward the tube axis. Support is fixed. and,
The upper end shield 2 and the lower end shield 3 are supported and fixed to a center support 4 and a side support 5, which respectively support the end shields 2 and 3 and supply a predetermined current to the filament 1. In this case, the upper end shield 2 is fixed to the upper end of the center support 4 on the tube axis,
The lower end shield 3 is fixed to the upper end of the side support 5 so that the center support 4 passes through the center of the circular hole 3a. Normally, during magnetron operation, approximately
1800℃, approximately at the joint with end shields 2 and 3
Because the temperature is as high as 1200°C, high melting point metals such as molybdenum and tungsten are used for the end shields 2 and 3, center support 4, and side support 5, respectively, and for the mechanical and electrical connections of each joint. The brazing material used is
In the past, platinum was used, but because it is extremely expensive, eutectic alloys of ruthenium and molybdenum have recently come to be used. A power supply terminal 6 is silver soldered to the other ends of the center support 4 and side supports 5 together with a stem ceramic 7, and a sealing part 8 is fixed to the stem ceramic 7 by silver soldering. In addition, between the center support 4 and the side supports 5, the filament 1 and the end shields 2 and 3 are exposed to vibrations and shocks from the outside.
An insulating spacer 9 is inserted to prevent displacement of the
Metal ring 1 that prevents displacement in the tube axis direction
0 is brazed and fixed to the side support 5 to form a magnetron cathode structure.

However, in the magnetron cathode structure having the above-mentioned configuration, the lower end sides of the center support 4 and the side supports 5 are supported and fixed to the stem ceramic 7, and the tip end side is a helical filament between the upper and lower end shields 2 and 3 facing each other. The filament 1 is formed by, for example, forming a thorium tungsten wire into a spiral shape and carbonizing its surface to increase the efficiency of emitting thermoelectrons. Therefore, the distance between the center support 4 and the side supports 5 is maintained constant by the insulating spacer 9, but the filament 1 may break due to external vibration or impact that causes rotational movement in the circumferential direction relative to the tube axis. I had a problem with it.

As a solution to this problem, the second
A magnetron cathode structure as shown in the figure has been proposed. That is, in the same figure, the circular hole 3a of the lower end shield 3 has a center support 4 at the center.
A ceramic spacer 11 made of alumina or the like is inserted so as to pass through the center support 4. A groove 4a is provided in the center support 4, and a metal E-ring 12 for preventing displacement in the tube axis direction is inserted into the groove 4a.
The ceramic spacer 11 is held and fixed to prevent the fragile filament 1 from breaking due to vibration or impact caused by the circumferential rotational movement from the outside.

However, the magnetron cathode structure with the above-mentioned configuration has a large number of assembly parts, and also has mechanical and
Since there are many electrical connection points, the number of assembly steps increases, productivity decreases, and manufacturing costs increase. Furthermore, since the E-ring locking groove 4a for holding the ceramic spacer 11 is formed in the center support 4, the center support 4 tends to break easily, resulting in a reduction in vibration resistance.

[Purpose of the invention]

Therefore, the present invention has been made to eliminate the above-mentioned conventional drawbacks, and its purpose is to provide an electron tube that reduces the cost of assembly parts and the number of assembly steps, and improves vibration resistance. The object of the present invention is to provide a cathode structure.

[Summary of the invention]

In order to achieve such an object, the present invention comprises a lower end shield that supports one end side of a helical filament made of a ceramic material, and a metallized layer is formed on the surface of this ceramic lower end shield. The filament and side support are bonded and fixed to the.

[Embodiments of the invention]

Next, embodiments of the present invention will be described in detail using the drawings.

FIGS. 3 and 4 are cross-sectional views showing an embodiment in which the electron tube cathode assembly according to the present invention is applied to a magnetron cathode assembly, and the same parts as those in the previous figures are given the same reference numerals and the explanation thereof will be omitted. In both figures,
3' is a ceramic lower end shield made of, for example, alumina, and a metallized layer 13 made of molybdenum is provided on the surface of this lower end shield 3' facing the upper end shield 2 and on the inner circumferential surface of the helical filament 1. It is formed by adhesion. Further, the center support 4 is inserted into the circular hole 3a of the ceramic lower end shield 3' to such a degree that the outer diameters of the center support 4 are in contact with each other. Further, a circular hole 3b is formed on the peripheral end side of the ceramic lower end shield 3', and the tip of the side support 5 is inserted into this circular hole 3b. Then, a ternary alloy (Ru-Mo-Ni) brazing material 14 made of ruthenium, molybdenum, and nickel is applied on this metallized layer 13.
The filament 1 and the side support 5 are fixedly fixed to the metallized layer 13 by firing.

According to such a structure, the ceramic lower end shield 3' and the spacers 9, 11 described above (see FIGS. 1 and 2) are integrated, so that the fixing metal as described above is used. Since the ring 10 and the E-ring 12 are not required, the number of parts is reduced and the configuration is simplified, so assembly costs can be reduced. Furthermore, by constructing the lower end shield 3' from a ceramic molded body such as alumina, the filament 1, center support 4, and side supports 5 can be assembled with extremely good dimensional fit, resulting in high assembly accuracy. ,
In addition to obtaining stable and uniform electrical characteristics,
High efficiency and high yield production is possible. Further, along with this, vibration resistance and impact resistance can be improved.

FIG. 5 is a cross-sectional configuration diagram of main parts showing another embodiment of the magnetron cathode structure according to the present invention, and FIG.
The same parts as those in FIG. This figure differs from FIG. 4 in that a ring-shaped recess 3c is formed on the upper end shield 2 side of the circular hole 3a for inserting the center support 4 in the ceramic lower end shield 3'.

Even in such a configuration, the same effect as described above can be obtained, and by providing the ring-shaped recess 3c, it is possible to prevent a decrease in insulation properties due to deposition of evaporated matter (fine metal powder) from the filament 1. can.

FIG. 6 is a sectional view of a main part showing still another embodiment of the magnetron cathode assembly according to the present invention, and the same parts as those in the previous figure are given the same reference numerals, and the explanation thereof will be omitted. In this figure, the difference from Figure 4 is as follows.
A metallized layer 1 is formed only on the flat surface of the ceramic lower end shield 3' that faces the upper end shield 2.
3 is formed.

In such a configuration, the same effect as described above can be obtained, and the convex portion 3d of the ceramic lower end shield 3' can contribute to positioning the filament 1, and moreover, it can prevent electric field concentration at the end of the metallized layer 13. Effective insulation effect can be obtained.

FIG. 7 is a sectional view showing another embodiment of the lower end shield constituting the magnetron cathode assembly according to the present invention. In the figure, the ceramic lower end shield 3' is constructed by forming a metallized layer 13 on the whole by dipping, and then polishing or grinding only the upper and lower end surfaces to form insulating parts. Even if the lower end shield 3' having such a configuration is used, the same effect as described above can be obtained.

It goes without saying that even if the ceramic lower end shield 3' is configured to have a concave cross section as shown in FIGS. 8 and 9, the same effect as described above can be obtained.

Furthermore, in the embodiments shown in FIGS. 6, 7, 8, and 9, a fifth hole is provided on the upper end shield 2 side of the circular hole 3a for inserting the center support 4 of the ceramic lower end shield 3'. Of course, by forming the ring-shaped recess 3c as shown in FIG.

〔Effect of the invention〕

As explained above, according to the present invention, it is possible to reduce the cost of assembly parts and the number of assembly steps, and
This has the extremely excellent effect of providing an electron tube cathode structure with high vibration resistance and impact resistance.

[Brief explanation of drawings]

FIG. 1 is a cross-sectional view showing an example of a conventional magnetron cathode structure, FIG. 2 is a cross-sectional view showing an example of a magnetron cathode structure proposed in recent years, and FIG. 3 is a cross-sectional view showing an example of an electron tube cathode structure according to the present invention. FIG. 4 is an enlarged sectional view of the main part of FIG. 3, and FIGS. 5 to 9 are enlarged main parts of the magnetron cathode structure showing other embodiments of the electron tube cathode structure according to the present invention. FIG. 1...Filament, 2...Upper end shield, 3'...Ceramic lower end shield, 3a,
3b... Circular hole, 3c... Recess, 4... Center support, 5... Side support, 6... Power supply terminal, 7... Stem ceramic, 8... Seal component, 13... Metallized layer, 14... Ternary alloy filler metal.

Claims (1)

[Claims] 1 A filament that emits thermoelectrons, upper and lower end shields that support the upper and lower ends of the filament, and a tube shaft that supports the upper and lower end shields and supplies a predetermined current to the filament. In an electron tube cathode structure including at least a center support disposed along the tube axis, and a side support disposed parallel to the tube axis at a position offset from the tube axis, the lower end shield is formed of ceramic, and the lower end A recess into which the filament is inserted is provided in the center of the surface of the shield with a diameter approximately equal to the outer diameter of the filament, a metallized layer is provided on the surface of the lower end shield including this recess, and the filament is inserted into the recess. An electron tube cathode structure characterized in that the filament and the side support are brazed to the metallized layer at each joint to mechanically fix them and at the same time electrically connect them.