JPH0746565B2 - Magnetron - Google Patents

Description

The present invention relates to a cathode for a magnetron, and more particularly to a filament structure.

[Background of the Invention] In a conventional magnetron cathode, a filament 1 which emits thermoelectrons is formed by spirally winding a single wire of thorium-tungsten as shown in FIG. 6 to prevent the thermoelectrons from deviating in the axial direction. It is fixedly supported by the end shield 2 and the lower end shield 3. Further, a center lead 4 and a side lead 5 for conducting a cathode current are connected to the upper end shield 2 and the lower end shield 3, and a terminal 6 is silver-brazed together with a stem ceramic 7 at the lower end of these. A sealing component 8 is brazed to the ceramic 7 by silver brazing. In addition, a spacer 9 made of an insulating material is inserted into the center lead 4 and the side lead 5 to prevent the spacer 9 from being displaced.
10 is fixed by welding.

In such a configuration, the filament 1 is carbonized on its surface in order to increase the thermoelectron emission efficiency, but the filament 1 is embrittled by this, and the center lead is caused by, for example, vibration or impact applied from the outside of the magnetron. The shape of the filament 1 may be deformed due to the vibration of the wire 4 and the side lead 5, and the filament 1 may be broken depending on its size. Therefore, in order to compensate for this problem, the diameters of the center lead 4 and the side leads 5 are increased to increase the rigidity, and the spacers 9 are connected to each other to enhance the vibration-proof effect. No. 138743 gazette) has been applied in the past, but there were problems such as high cost.

On the other hand, in order to improve the strength of the filament 1 itself, in JP-A-55-68049, 0.5 to 4.0% thorium oxide,
A cathode assembly for an electron tube has been proposed which uses a tungsten wire to which rhenium is added in an amount of 1.0 to 10.0% to improve the wire strength.

However, in such a structure, the wires themselves are alloyed, and there is a difficulty in metallurgical treatment, and the electric resistance value of the wires changes (direction in which the resistance value increases). If the same size as the tungsten wire, the filament voltage fluctuates and there is a problem such as incompatibility.

[Object of the Invention]

Therefore, the present invention has been made in view of the above-mentioned conventional problems, and its purpose is to prevent disconnection of filaments, and to improve reliability by having a stable constant electric resistance value. The object is to provide a magnetron cathode that can reduce costs.

[Outline of Invention]

In order to achieve such an object, the present invention is constructed by combining a filament wire containing thorium and a tungsten wire containing rhenium.

Example of Invention

 Next, embodiments of the present invention will be described in detail with reference to the drawings.

FIG. 1 is a sectional view showing an embodiment of a magnetron cathode according to the present invention, and the same parts as those in the above-mentioned drawings are designated by the same reference numerals. In the figure, the filament 11 has a rhenium tungsten wire 11a containing rhenium in the central portion and nine thorium tungsten fine wires 11b containing thorium on its outer peripheral surface as shown in FIG. It is composed by bundling. In this case, the rhenium content of the rhenium tungsten wire 11a is not particularly limited, but 0.5
The range of up to 10% is sufficient, and particularly when it is 3% or more, the recrystallization temperature of the filament wire is remarkably increased, which is practical.

In such a structure, the filament 11 has a high recrystallization temperature in the central part thereof, the toughness of the filament 1 itself becomes large, and the outer peripheral surface thereof is coated with nine thorium tungsten fine wires 11b, so that the strength is improved. The rhenium-tungsten wire 11a that is in charge of this is hard to be carbonized and is prevented from becoming brittle.
11b also has an increased surface area per unit length compared to the single wire filament 1 in Fig. 6, and the radiation efficiency of thermionic electrons is also greatly improved. In addition, nine thorium tungsten fine wires 11b covering the outer peripheral surface of the rhenium tungsten wire 11a.
It is convenient to cover the stranded wire as it is easier to handle in assembling the cathode.

2 to 5 are sectional views showing another embodiment of the filament 11 relating to the magnetron cathode according to the present invention. In these figures, Fig. 2 shows the filament 11 by completely covering the entire outer peripheral surface of the rhenium tungsten wire 11a with an annular thorium tungsten fine wire 11b ', and Fig. 3 shows a square rhenium tungsten wire 11a'. The filament-shaped thin thorium tungsten wire 11b ″ is bonded and bonded to both outer surfaces of the filament to form the filament 11. FIG. The filament 11 is formed by adhering. In FIG. 5, the same effect as described above can be obtained even if the filament 11 is formed by adhering one rhenium tungsten wire 11a and two thorium tungsten wires 11b in combination. .

〔The invention's effect〕

As described above, according to the present invention, the filament is configured by combining the thorium-containing tungsten wire and the rhenium-containing dungsten wire, whereby the filament mechanical strength can be improved, and a stable constant electric resistance value can be obtained. As a result, the reliability can be improved and the surface area can be increased to collect more thermoelectrons,
The emission characteristics can be improved. In addition, along with this, it becomes possible to reduce the wire diameters of the expensive center lead and side leads and to omit the reinforcing spacers, so that it is possible to obtain an inexpensive magnetron, which is extremely effective.

[Brief description of drawings]

FIG. 1 is a sectional view showing an embodiment of a cathode for a magnetron according to the present invention, FIGS. 2 to 5 are sectional views showing another embodiment of a filament according to the present invention, and FIG. 6 is a conventional magnetron. It is sectional drawing which shows a cathode. 2 ... upper end shield, 3 ... lower end shield, 4
...... Center lead, 5 ...... Side lead, 6 ...... Terminal, 7 …… Stem ceramic, 8 …… Seal parts, 9 ・ ・ ・
… Spacer, 10 …… Sleeve, 11 …… Filament, 11
a, 11a '... Rhenium tungsten wire, 11b ... Thorium tungsten fine wire, 11b' ... Torus thorium tungsten wire, 11b ″ ... Square-shaped thorium tungsten wire, 11b ... U-shaped thorium tungsten wire .

Claims (1)

[Claims] 1. A filament for emitting thermoelectrons, an upper end shield and a lower end shield fixed to the upper and lower ends of the filament, a center lead fixed to the upper end shield, and a lower end shield fixed to the lower end shield. And a side lead, wherein the filament is composed of a tungsten wire containing rhenium as a core and a tungsten wire containing thorium so as to surround the filament.