JPS6226744A - Magnetron cathode structure and its manufacture - Google Patents

Abstract

PURPOSE:To fix the brazing position, when brazing the end section of filament to the innercircumferential wall of end hat, by forming a step section at the innercircumferntial section of the endface of end hat and providing plural projections specifically at the inside. CONSTITUTION:Magnetron cathode structure is formed by connecting a spiral filament 16 between pair of end hats 11. Here, the end hat 11 is formed such that a step section 13 is formed at the innercircumferential section of the endface while plural projections 31 are arranged in circle at the step section 13 while maintaining an interval (l) longer than 2mm from the innercircumferential wall 17. A brazing material rings is secured in the step section 13 while a filament 16 is arranged then heated through high frequency heating to flow the fused brazing material through a gap 17a to the innercircumferential wall 17 and to joint through brazing material layer 32. Consequently, the projection 31 will never be jointed directly to the filament 16 resulting in uniform effective length of filament.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a magnetron cathode assembly and a method for manufacturing the same.

[Technical Background of the Invention and Problems Therewith] For example, in a magnetron for a microwave oven, a cathode structure for electron emission is provided at the inner center of an anode structure forming a resonant cavity. This cathode structure has a configuration in which a spirally wound directly heated filament is electrically connected between a pair of end hats, and these end hats are supported by a pair of support rods.

The connection between the end hat and the filament is generally brazed with a high melting point brazing material such as ruthenium (Ru)-molybdenum (Mo). The present inventor previously proposed a soldering method having the configuration shown in FIGS. 8 and 9. A step part 13 and a plurality of protrusions 14, 14, etc. are integrally molded on the upper end surface 12 of the end hat 11, a ring-shaped solid brazing material 15 is fixed to the outer periphery of these protrusions, and a filament 16 is fixed. The filament is inserted into the inner circumferential wall 17 of the end hat and heated, and the end hat and the filament are soldered together using a brazing material flowing from the gap 18 between the protrusions. In addition, the reference numeral 18 in the figure is the central through hole of the end hat, and 19
is the center rod, and 20 is the side rod.

According to this, the flow of the solder to the filament end is reliable and stable, and a good soldering state can be obtained. On the other hand, if each protrusion is formed on the inner peripheral edge of the stepped part, there is a risk that the electrical connection points between the helical filament and the end hat, especially these protrusions, may become irregular, and there is room for improvement. That is, the extreme end of the soldered portion between the helical filament and the protrusion is at position A or at position B, as shown in FIG. As a result, the effective length of the filament becomes slightly uneven. This has the disadvantage that the current value and operating temperature of the filament vary.

(Objective of the Invention) The present invention provides a magnetron cathode assembly which eliminates the above-mentioned disadvantages, has excellent assembly and soldering properties, and can uniformly control the filament effective length, and a method for manufacturing the same. .

[Summary of the invention]

The present invention includes integrally molding a plurality of protrusions in a circular shape on the inner circumferential stepped portion of the end face of the end hat at predetermined distances apart from the inner circumferential edge of the stepped portion, and a ring-shaped protruding portion on the outer periphery of these protruding portions. With the brazing material fixed, the end of the filament is inserted into the inner circumferential wall of the end hat, and these are heated to melt the brazing material. A magnetron cathode structure whose end is soldered to an end hat, and its manufacturing method.

As a result, the protruding portion is not directly joined to the filament, so that the electrical connection position between the filament and the end hat is constant even in mass production, and the effective length of the filament is uniform.

(Embodiments of the invention) Examples thereof will be described below with reference to the drawings. Identical parts are designated by the same reference numerals. -'・ As shown in Fig. 1, the end hat 11 made of a sintered body of Mo has
The stepped portion 13 is provided with a predetermined interval (/
), a plurality of protrusions 31, 31... are integrally formed. This interval (f) shall be 0.2 mm or more. The end hat 11 and the filament 16 are soldered and fixed by a brazing material layer 32 disposed at the stepped portion, heated and melted, and flowing from the gap between the protruding portions to the inner circumferential wall.

That is, in the end hat 11, as shown in FIGS. 2 and 3, three or more, for example, six, protrusions 31, 31, . and the fourth
The ring-shaped solid Ru-Mo brazing filler metal 15 shown in the figure was
As shown in the figure and M6 figure, it is tightly fitted and fixed to the outer periphery of each protrusion 31. This fixing method involves, for example, placing a somewhat large-diameter pre-sintered or pre-sintered ring-shaped filler metal around the outer periphery of these protrusions of the end hat, heating it to a high temperature to sinter it, and then cooling it. This can be achieved by a method in which the brazing filler metal contracts and is mechanically hardened. Alternatively, only the ring-shaped brazing material 15 may be heated to enlarge its diameter, placed around the outer periphery of the protrusion, and fixed by shrinkage due to cooling.

Then, as shown in FIG. 7, the support rods 19, 20 and the helical filament 16 are arranged, and the ring-shaped brazing filler metal 15 disposed on the stepped portion 13 is heated and melted, for example, by high-frequency heating. The molten solder fills the gap 1 between each protrusion from the stepped part.
The filament 16 flows to reach the inner circumferential wall 17 through the filament 7a, and the filament 16 is soldered to the end hat. And none of the protrusions come into direct contact with the filament.

In this way, a soldered structure as shown in FIG. 1 is obtained.

(Effects of the Invention) The magnetron cathode structure and the manufacturing method thereof of the present invention are as follows:
As explained above, since the protrusion is not directly joined to the filament, the electrical connection position between the filament and the end hat is constant even in mass production, and the effective length of the filament is uniform. Furthermore, the brazing filler metal can be fixed easily and reliably, and it is also effective for mass production and automation.

[Brief explanation of the drawing]

Fig. 1 is a vertical cross-sectional view of a main part showing an embodiment of the present invention, Figs. 2 and 3 are enlarged longitudinal cross-sectional views and top views of the parts, Fig. 4 is a cross-sectional view showing the brazing material, and Fig. 5 6 is a cross-sectional view and a top view of the assembled structure, FIG. 7 is a structural view of the soldering area, and FIG. 8 is a vertical sectional view of the main part of the prior art.
FIG. 9 is a cross-sectional view taken at 9-9 in FIG. 8. DESCRIPTION OF SYMBOLS 11... End hat, 12... Upper end surface, 13... Step part, 15... Brazing metal, 16... Filament, 17... Inner peripheral wall, 17a... Inner peripheral edge, 31... -Protruding portion, 32...brazing material layer.

Claims (2)

[Claims] (1) In a magnetron cathode structure in which the end of a helical filament is soldered and fixed to the inner circumferential wall of a ring-shaped end hat, the end hat has a step formed on the inner circumference of its end surface, and an inner wall of the end hat is formed inside the step. A plurality of protrusions are integrally molded in a circular shape at predetermined intervals outward from the periphery, and the filament is formed by a layer of brazing material that flows from the stepped part of the end hat to the inner circumferential wall through the gaps between the protrusions. A magnetron cathode structure characterized in that an end portion is fixed to the end hat by soldering. (2) In a method for manufacturing a magnetron cathode structure in which the end of a helical filament is soldered and fixed to the inner wall of a ring-shaped end hat, a step is formed in advance on the inner circumference of the end surface of the end hat, and an inner wall of the step is formed in advance. A plurality of protrusions are integrally molded into a circular shape at predetermined intervals outward from the periphery, a ring-shaped brazing material is fixed to the outer periphery of these protrusions, and the filament end is attached to the inner peripheral wall of the end hat. A magnetron characterized in that the end of the filament is fixed to the end hat by the soldering material which is inserted into the end hat, heated and melted, and flows from the end hat stepped portion to the inner circumferential wall through the gap between each protrusion. A method for manufacturing a cathode structure.