JPS6055941B2 - magnetron cathode structure - Google Patents

Description

[Detailed description of the invention] The present invention relates to a magnetron cathode assembly.

As shown in FIG. 1, the magnetron is a cavity resonator group consisting of two magnetic pole pieces 2 and 3 soldered to both open ends of a cathode cylinder 1 and a plurality of vanes formed on the inner surface of an anode cylinder 1. 4, a cathode 5 disposed at the center of the anode cylinder 1, an insulator 11 such as ceramic for insulating and holding the cathode 5 from the anode 1, and the cathode 5 being fixed to the insulator 11. The microwave energy generated in the input section and the cavity resonator group 4 is transferred to the outside of the tube. In order to propagate the signal, an antenna conductor 9 formed from a copper plate is connected to a part of the cavity resonator group and extends upward, and an antenna conductor 9 is fixed to one end of a cylindrical insulator 7 made of ceramic or the like, and the other is connected to a cylindrical insulator 7 made of ceramic or the like. It has an output section consisting of a cup-shaped metal 6 whose end is fixed to the magnetic pole piece 2, an exhaust pipe 8, etc., which is brazed to the other end of the insulator 7, and an antenna conductor 9 is pressure-welded inside. . FIG. 2 shows details of the cathode assembly 5.

In the figure, reference numeral 50 denotes a filament made of a thorium-containing tungsten wire formed into a spiral shape, and when energized, it generates heat and emits electrons. End shields 51 and 52 made of molybdenum are arranged at both ends of the filament 50 in the axial direction. The end shields 51 and 52 regulate the range of electron emission, and are connected to the filament 50 by a brazing material 54 made of a high melting point metal such as Pt or Ru-MO alloy.
is made of an MO rod and is brazed to a support 55 through which the filament 50 passes in a non-contact manner. However, the magnetron cathode assembly having the above configuration has the following drawbacks.

(1) The wire diameter of the filament 50 cannot be made small because it is necessary for the filament 50 to withstand external impact applied to the magnetron itself.

Furthermore, due to high-temperature operation, the wire is easily deformed by its own weight, and for this reason as well, the wire diameter cannot be reduced. If the wire diameter of the filament 50 is large, bending, surface peeling, or cracking may occur when forming the filament 50 into a spiral shape, resulting in a significant decrease in reliability. (2) As is well known, due to the intermittent operation of the cathode, the internal stress of the carbonized layer formed on the filament surface destroys this layer and reduces electron radioactivity.
The internal stress of the carbonized layer increases as the filament wire diameter increases, and for this reason, the life of the conventional type is shortened.

For this reason, in the conventional cathode structure, when output control of a microwave oven is performed in an intermittent manner, it is necessary to have a long intermittent cycle. (3) Since an expensive brazing material is required to fix the filament 50, the cost increases.

(4) Since the wire diameter of the filament 50 is large, the temperature distribution of the filament 50 becomes poor due to the end cooling effect.

(5) Warm-up time is long because the filament 50 has a large heat capacity.

Therefore, in order to eliminate the above-mentioned drawbacks, a structure that uses a filament with a small wire diameter by forming it from a mesh type cathode has recently been developed (Japanese Patent No. 227147).
has been proposed, but this structure has the disadvantage that the manufacturing method is complicated and expensive.

Therefore, an object of the present invention is to provide a magnetron cathode structure which eliminates the drawbacks listed in (1) to (5) above, and which is easy to manufacture and inexpensive.

In order to eliminate such drawbacks, the gist of the present invention is to construct a cathode structure by spirally winding thin filaments around a plurality of supports (hereinafter referred to as supports) arranged approximately in parallel. This will be explained in detail below using examples.

FIG. 3a is a simplified configuration diagram showing one embodiment of a magnetron cathode structure according to the present invention, and FIG. 3b is a cross-sectional view along line A-A. In the same figure, 55a and 55b are supports made of molybdenum. These are arranged parallel to each other and fixed to a stem (not shown).

Reference numerals 56 and 57 denote end shields made of molybdenum plates, and both ends of one support 55b pass through the small holes 58b of each end shield 56 and 57 in pressure contact, and both ends of the support 55a pass through the large hole 58a. penetrates without contact.

Reference numeral 59 denotes a filament wound spirally around both supports 55a and 55b, and its diameter is extremely small compared to conventional filaments, for example, about 0.1φ to 0.05φ, as shown in FIGS. Supports 55a and 55b in the manner shown in
Fixed.

That is, as shown in FIG. 4a, the supports 55a, 55
A cutter is used to form grooves 60 at a constant pitch in b, and the filament 59 is spirally wound and inserted into the grooves 60 as shown in b of the same figure. The corresponding portion is pressed and deformed, thereby embedding the filament 59. As a method for fixing the filament 59 to the supports 55a, 55b, there is another method for fixing the filament 59 to the supports 55a, 55b as shown in FIG.
After winding the filament 59, fine MO powder 6 is applied to the contact area between the filament 59 and the supports 55a and 55b.
2 is applied with a binder and fixed by sintering,
Alternatively, as shown in FIG. 6, after winding the filament 59 around the supports 55a and 55b, resistance welding is performed using a welding electrode to fix the filament 59. These, the fourth
According to the method shown in FIG.
This has the effect that little mechanical stress is applied to the support, making it difficult for the support to deform. Next, the above supports 55a, 5
The cross-sectional shape of 5b may be a perfect circle as shown in FIG. 7a, or may be keyhole-shaped, triangular, or square as shown in FIGS. 7b to 7d.

In this way, when the apex portion is brought into contact with the filament 59, this contact state can be maintained constant even if there are variations in the fixed state shown in FIGS. 4 to 6, or even if external stress is applied. can. FIG. 8 shows the support structure of supports 55a and 55b, and in the same figure, 63
64 is a spacer made of an insulating material such as ceramic placed on the filament 59 side of the end shield 56, and 64 is a spacer placed on the opposite side of the end shield 57 from the filament 59. Two through holes 63a, 64a through which 55a, 55b penetrate
The spacers 63 and 64 can hold and fix both supports 55a and 55b in a parallel state.

According to this configuration, the filament 59 is supported and fixed by the spacers 63 and 64 and attached to the two integrated supports 55a and 55b, so that the filament 59 as a whole can sufficiently resist external impact force and vibration. This makes it possible to have extremely high strength. In addition, in FIG. 8, it goes without saying that either one of the spacers 63 and 64 may be omitted. However, adding the spacer 63 greatly improves the impact resistance. FIG. 9 shows a magnetron cathode structure according to the present invention in which end shields 56, 57 and spacers 63, 64 are integrated. In the figure, 63, 64 are spacers made of an insulator;
Supports 55a and 55b are fixed at the upper and lower ends of the filament 59.

65 and 66 are stoppers, and 67 and 68 are the spacers 6.
This is a metallized layer obtained by metallizing the surfaces of Nos. 3 and 64, and can function as an end shield.

The metallized layers 67 and 68 are formed as follows. That is, as shown in FIGS. 10A and 10B, the peripheries of the through holes A and b of the disc-shaped spacers 63 and 64 are made to protrude, and MO fine powder is applied to the front and back surfaces other than the protrusions x, and then sintered. Alternatively, as shown in Figure c, the peripheries of the through holes A and b are recessed, and MO fine powder is applied to the surfaces other than the recesses y.
Formed by sintering. Further, as shown in FIGS. 11A and 11b, a groove m is formed across the center of the spacers 63 and 64 to separate the through holes x and y, and MO fine powder is applied to the surface other than the groove m. It can also be formed by sintering. Note that as the method for applying the MO, either a transfer method or a printing method may be used. In the case of FIGS. 10A and 10b, the MO layer may be deposited over the entire surface and then only the MO layer on the surface of the convex portion x may be scraped off. According to the above configuration, the metallized layers 67 and 68 support the supports 55a and 55.
b without electrically shorting the metallized layer 67.
, 68 can function as an end shield, and manufacturing is relatively easy. FIG. 12 shows another embodiment of the magnetron cathode assembly according to the invention.

In the same figure, 56 and 57 are end shields provided at the upper and lower ends of the filament 59, and both ends of one support 55b penetrate through the small holes 58b of each end shield 56 and 57 in a press-contact state. Both ends of the support 55a pass through the hole 58a in a non-contact manner. A cylindrical stopper 69 has a flange 69a and is made of an insulating material such as ceramic.

The outer diameter side of the stopper 69 is inserted into the large hole 58a in a pressed state, and the support 55a passes through the inner diameter side in a pressed state. Note that the directions of both stoppers 69 are the directions in which the flanges 69a face each other. According to such a configuration, both supports 55a and 55b can be maintained in an insulated state, and the mechanical strength of the whole can be greatly improved.
In addition, supports 55a, 55b or metallized layer 6
7 and 68 are not limited to being formed from MO, but may be formed from other metals. In addition, supports 55a and 55b
is not limited to two, but may be three.

As explained above, the magnetron cathode structure according to the present invention mainly consists of a plurality of supports made of a conductive material and arranged approximately in parallel, and a fine wire filament wound around these supports. 11
The number of turns is 2 or less, and the thin filament itself does not undergo deformation at high temperatures, external vibrations, or breakage due to impact force, and the temperature distribution at the upper and lower ends of the cathode is uniform.

Further, since the filament is a thin wire, even if intense intermittent heating is performed, electron radiation deterioration due to damage to the carbonized layer is reduced, resulting in a long life. Furthermore, since the two supports extend to the upper end of the cathode and can be integrated with a spacer, the cathode is extremely strong against external shocks and vibrations. In addition, since the filament can be continuously wound and fixed on at least two supports, it is excellent for mass production, and there is no need to use expensive platinum or Ru-MO alloys, making it easy to manufacture and therefore inexpensive. It has the great effect of eliminating the problems all at once.

[Brief explanation of the drawing]

Figure 1 is a sectional view showing an example of a conventional magnetron, Figure 2 is a cross-sectional view showing an example of a conventional magnetron.
The figure is a cross-sectional view showing an example of a conventional magnetron cathode structure.
Figure 3 A, bl Figure 4 A, b, Cl Figure 5, Figure 6, Figure 7 A, b, c, dl Figure 8, Figure 9, Figure 10 A, b
, cl FIGS. 11 and 12 are simplified configuration diagrams showing an embodiment of a magnetron cathode structure according to the present invention. 55a, 55b... Support, 56, 57...
...End shield, 58a, 58b...
Hole, 59...Filament, 60...
Groove, 61... Hammer, 62... Fine powder, 63, 64... Spacer, 65, 66, 6
9... Stopper, 67, 68... Metallized layer.

Claims (1)

[Scope of Claims] 1. At least two electrically conductive pillars arranged substantially parallel to each other, a thin wire filament wound circularly around the pillars, and the above-mentioned wire filament located at both ends of the filament. The filament is provided with an end shield that extends in a direction perpendicular to the pillars and restricts electron radiation, and the filament is fixed to the two pillars at the point of contact with the two pillars, and the current between the pillars is A magnetron cathode assembly characterized in that the filament is supplied with heat to cause the filament itself to emit electrons. 2. The magnetron cathode assembly according to claim 1, wherein the filament is embedded in the pillar and fixed by welding or sintering. 3. In the magnetron cathode structure according to claim 1, metal plates located at both ends of the filament and extending in a direction perpendicular to the support columns are fixed to one of the support columns. A magnetron cathode structure, characterized in that a spacer made of an insulator is provided around the hole passing through the other support without contacting the metal plate, or in parallel to the metal plate. 4. In the magnetron cathode assembly as set forth in claim 1 above, the cross-sectional shape of the strut is such that the portion that contacts the filament protrudes, and the filament is fixed to this protruding portion. Magnetron cathode structure. 5. The magnetron cathode assembly according to claim 3, wherein a metallized layer is provided on at least the surface of the spacer on the filament side.