JPS601724A - Magnetron cathode structure - Google Patents

Abstract

PURPOSE:To make a cathode structure to well stand severe operation by providing a highly pure ceramic spacer between a center support supporting a filament and an electrode member adjacent to said center support. CONSTITUTION:An almost ring-shaped, highly pure aluminous ceramic spacer 9a, through which the center lead 4 passes, is inserted into a round hole 3a of the lower end shield 3. Thereby, the end having the smaller diameter of said spacer 9a is inserted into the round hole 3a of the lower end shield 3, while the end having the larger diameter of said spacer 9a is stopped hanging on the bent part 4a of the center lead 4 so as to lose directivity for the vibrations in the dierction A-A' and the direction at a right angle thereto thus to obtain higher vibrationproof efficiency and accordingly to be able to use the center lead 4 and the side lead 5 having the small diameter.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to a magnetron cathode assembly, and particularly to a magnetron cathode assembly in which the vibration resistance of a filament is improved.

[Background of the invention]

FIG. 1 is a cross-sectional configuration diagram of essential parts showing an example of a cathode structure of a magnetron. In the figure, a filament 1 that emits thermoelectrons is arranged concentrically with the tube axis of the magnetron, and is fixedly supported by an upper end shield 2 and a lower end shield 3 that prevent the thermoelectrons from deviating in the axial direction. and,
The upper end shield 2 is fixed to the upper end of the center lead 4 on the tube axis, and the lower end shield 3 is fixed to the upper end of the center lead 4 on the tube axis.
Side lead 5 so that center lead 4 passes through the center of
is fixed at the top of the Furthermore, a terminal 6 is soldered with silver copper to the lower ends of the center lead 4 and the side leads 5 together with a stem ceramic 7, and a seal component 8 is soldered with silver copper to the stem ceramic 7.

Further, the center lead 4 and the side leads 5 are each fitted into a through hole of a spacer 9.
The sleeve 10 is fixed by welding to prevent displacement.

In the cathode structure having such a configuration, the center lead 4 and the side leads 5 have different resonance points due to external vibration due to the difference in length, etc., and this can be prevented by connecting them with the spacer 9. This produces a vibration effect, which has the effect of increasing the vibration resistance of the cathode structure as a whole.

However, in the cathode structure having such a configuration, the vibration-proofing effect of the spacer 9 is greater in the direction perpendicular to the arrow A-A (direction perpendicular to the plane of the paper) than in the direction of the arrow A-1 shown in the figure. ) has a problem in that its vibration-proofing effect is small.

[Purpose of the invention]

Therefore, the present invention has been made in view of the above-mentioned conventional problems, and its purpose is to provide a magnetron cathode structure with improved vibration resistance against vibrations applied from all directions. There is a particular thing.

[Summary of the invention]

In order to achieve this object, the magnetron cathode assembly according to the present invention has a high purity alumina ceramic spacer interposed between a center lead and an electrode member adjacent to the center lead.

[Embodiments of the invention]

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

FIG. 2 is a sectional view of a main part corresponding to FIG. 1 showing one embodiment of a magnetron cathode assembly according to the present invention, and the same parts as in FIG. 1 are given the same reference numerals. In the figure, a substantially ring-shaped spacer 9a through which the center lead 4 is passed is inserted into the circular hole 3a of the lower end shield 30.

According to such a configuration, the small diameter end of the spacer 9& is inserted into the circular hole 3a of the lower end shield 3, and the large diameter end is locked to the bent portion 4a of the center lead 4. As shown in the same figure, there is no directionality with respect to vibrations in the A-λ direction and the direction perpendicular to this direction, and a higher vibration damping effect can be obtained. A center lead 4 and a side lead 5 having a smaller diameter can be used.

3(a) and 3(b) are main part sectional configuration diagrams corresponding to FIG. 1 showing another embodiment of the magnetron cathode structure according to the present invention, and the same parts as in FIG. . In these figures, spacers 9b and 9c are attached to the tip of the center lead 4 (see (a) in the figure) or the outer periphery of the upper end shield 2 (see (b) in the figure) so as to directly suppress the vibration of the center lead 4. ), and the outer diameter side surrounds the cathode through the magnetic pole 110 through hole 11a or the anode 1.
2 is fitted.

According to such a configuration, it is possible to suppress the vibration of the long and flexible center lead 4 and also to prevent the fragile filament 1 from breaking.

In the cathode structure constructed as described above, the spacers 9.9at9b+9e must all be made of an insulating material that does not emit harmful gases when the temperature rises within the vacuum tube. Therefore, 4-alumina ceramic is generally widely used for these spacers 9, 9a, 9b, and 9e. As for this alumina ceramic, its alumina content (AL
, o8) depending on the purity of high purity alumina (Aj20,9
There are low purity aluminas (8% or higher) and lower purity aluminas, and the higher the alumina purity, the higher the firing temperature. The temperature at which the spacer is used during operation of the magnetron is approximately 700°C for the type shown in Figure 1, and approximately 10°C for the types shown in Figures 2 and 3.
00°C, and even low-purity alumina can be used simply from the viewpoint of heat resistance.

However, when a spacer made of low-purity alumina is used in a magnetron of practical use, especially when the microwave reflection generated during operation is large, that is, when used in a no-load state, the cathode of the type shown in Figure 1 Although no abnormality occurred in the structure, in the case of the cathode structures shown in FIGS. 2 and 3, sparks were generated in each spacer 9a, 9b, and 9e by microwaves, and the spacers were locally melted at that time. It was found that gas was generated and a so-called emission slump occurred. Therefore, spacers 9a and 9b of the cathode structure shown in FIGS. 2 and 3.

When high-purity alumina was used in 9c, the above-mentioned phenomenon did not occur. The reason for this was investigated by examining the relationship between -δ characteristics and temperature, which relate to microwave loss in ceramics, and it was found that there is a relationship as shown in FIG. 4. In other words, when we look at the relationship between temperature and -δ using the purity of At2OB as a parameter, we find that for low-purity alumina (At20a 85 to 96 inches) in the region shown by characteristic I, the operating temperature is as shown in Figure 1. Since it is about 700℃,
-δ is about 30X10", but in the case of Figures 2 and 3, -δ is 80X10" to raise the temperature to about 1000℃.
It can be inferred that localized heat generation occurs without causing a loss that is approximately three times larger than that of the conventional one. Therefore, in the same figure, the characteristic ■
High purity alumina in the range shown (11208981 or higher)
If so, it can be seen that -δ does not become large even if the operating temperature is about 1000°C. Therefore, FIG.

The materials of the spacers 9a, 9b, 9c used in FIG.
By using high purity alumina containing 98 or more of 20B, it is possible to completely eliminate the generation of sparks due to the increase in high frequency loss as described above.

FIG. 5 shows a cross-sectional configuration of main parts corresponding to FIG. 1 showing still another embodiment of the magnetron cathode structure according to the present invention.
The same parts as in the previous figures are given the same reference numerals. In the same figure,
The difference from FIG. 2 is that, as shown in the enlarged cross-sectional view in FIG. 6, a binder such as carpitol acetate or isobutyl methacrylate is added to the small-diameter inner and outer walls of the approximately ring-shaped spacer 9a. M0 powder paste 13 made into a paste is applied and inserted into the circular hole 3a of the lower end shield 30 through the center lead 4 as shown in FIG. If you perform the same brazing as heating and melting Ru'Mo solder, the heating at that time will melt Mo with a high melting point.
Instead of melting and flowing out like a brazing material, the surface of the spacer 9& is solidified as if a Mo metallized film was formed, and is well adapted to and fixed to the lower end shield 3 and center lead 50M0 base material. As a result, the spacer 9a is brought into close contact with the center lead 4 and the lower end shield 3, and a strong fitted state is obtained. In this case, M is attached to the spacer 9a. Instead of applying the powder paste 13, the inner wall of the lower end shield 3 and the center lead 4
Needless to say, the same effect can be obtained even if it is applied to the outer periphery of the .

According to such a configuration, the spacer 9a is fixed to the center lead 4° and the lower end shield 3, and there is no slippage between the spacer 9a, the center lead, and the lower end shield, and the center lead 4° and the side lead 5 are secured to the outside. The brittle filament 1 is not deformed even when vibrated by excitation from the source, and a strong cathode structure can be formed. Therefore, the wire diameters of both leads 4 and 5 can be made thinner, resulting in high reliability and An inexpensive cathode structure can be obtained.

FIG. 7 is a cross-sectional configuration diagram of main parts corresponding to FIG. 1 showing another embodiment of the magnetron cathode assembly according to the present invention (1), and the same parts as in the previous figures are given the same reference numerals.

The difference between this figure and FIG. 2 is that upper and lower end shields 2 and 3 and filament 1 are heated at the small diameter end of the approximately ring-shaped spacer 9m, as shown in the enlarged cross-sectional view in FIG. M0 powder brazing filler metal 14, which is the same as the melting brazing filler metal
Ru' of the spacer 9a is applied and inserted through the center lined 4 into the circular hole 3a of the lower end shield 3 as shown in FIG. In the vicinity of the application of the Mo filler material 14, the particles diffuse into the alumina that is the material of the spacer 9a, causing expansion and deformation, and as shown in FIG.
The smaller diameter part has a smaller diameter. As a result, the spacer 9a is brought into close contact with the center lead 4 and the lower end shield 3, and a firmly fitted state is achieved.

In this case, the function of the spacer 9a as an insulator is that the alumina ceramic impregnated with heat has sufficient voltage resistance characteristics against the voltage of 3V applied to the filament 1.

According to this configuration, the spacer 9a is connected to the center lead 4. It is fixed to the lower end shield 3, and the spacer 9a
There is no slippage between the center lead 4 and the lower end shield 3, and even if both leads 4.5 vibrate due to external vibrations, the fragile filament 1 is not deformed, resulting in a strong cathode structure. Therefore, the wire diameters of both leads 4 and 5 can be made much thinner, and a highly reliable and inexpensive magnetron can be obtained.

FIG. 9 is a sectional view of a main part corresponding to FIG. 1 showing still another embodiment of the magnetron cathode structure according to the present invention, and the same parts as in the previous drawings are given the same reference numerals. In the figure, the spacer 15 has a hollow part 15a through which the center lead 4 passes, and a substantially ring-shaped cylindrical part 15b which fits into the circular hole 3a of the lower end shield 3, as shown in an enlarged perspective view in FIG. and three leg portions 15e that fit into the inner wall surface of the through hole 16a of the magnetic pole 16, and are made of a ceramic material with an alumina purity of 98 degrees or higher. The spacer 15 is fitted between the circular hole 3a of the lower end shield 3 and the through hole 16a of the magnetic pole 160 by passing the center lead 4 through the cavity 1Sa.
As a result, the lower end shield 3 is completely suppressed. Therefore, the vibration of the center lead 4 can also be completely suppressed through the spacer 15. Also, this spacer 1
5 is a hollow part 15 through which the center lead 4 passes and a cylindrical part 15
Since the outer circumferential portion is small (both are provided with leg portions 15e formed by dividing into three parts), it is possible to avoid the side leads 5 and fit into the magnetic pole 16, and the magnetic pole 16 has an anode potential. The capacitive component generated between the lower end shield 3 and the lower end shield 3, which has a cathode potential, is reduced, and the high frequency loss occurring in the spacer 15 can be reduced. Placing the cathode filament 1 as coaxially as possible at the center of the tube axis will reduce the reactive current (dark current) that does not contribute to oscillation when the magnetron oscillates, thereby increasing output efficiency and operational stability. Therefore, even in the above-mentioned magnetron with a cathode structure, centering is performed using a jig during assembly, but the cathode leads 4 and 5 are flexible and elastic, and the center axis may be misaligned when assembled. According to this embodiment, since the spacer 15 also has the function of serving as a centering guide, it is possible to forcibly center the cathode.

Even in such a configuration, a highly reliable, inexpensive, and high-performance magnetron can be obtained by preventing breakage of the fragile filament 1 and allowing natural positioning of the cathode.

〔Effect of the invention〕

As explained above, according to the magnetron cathode assembly according to the present invention, the high purity ceramic spacer is provided between the center support that supports the filament and the electrode member adjacent to this center support, so that the cathode assembly can be easily damaged. This has the extremely excellent effect of making it possible to withstand operation, making it possible to make the expensive molybdenum center lead thinner without reducing the strength of the filament, and to obtain a cheaper magnetron.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional configuration diagram of essential parts showing an example of a conventional magnetron cathode assembly, FIG. (b) is a cross-sectional configuration diagram of main parts showing another embodiment of the magnetron cathode structure according to the present invention;
The figure shows the characteristics showing the relationship of −δ with respect to the operating temperature of the magnetron using alumina purity as a parameter, FIG. FIG. 7 is an enlarged sectional view of the spacer shown in FIG. 7; FIG. 7 is a sectional configuration diagram of main parts showing another embodiment of the magnetron cathode structure according to the present invention; FIG. 8 is an enlarged sectional view of the spacer shown in FIG. 7; FIG. 10 is a cross-sectional configuration diagram of main parts showing another embodiment of the magnetron cathode assembly according to the present invention, and FIG. 10 is a perspective view of the spacer shown in FIG. 9. 1...Filament, 2...Top end shield, 3...Bottom end shield, 3a...Circular hole, 4...Center lead, 5...Side lead, 6 ...Terminal, 7...Stem ceramic, 8.
... Seal parts, 9°9a, 9b, 9e ... Spacer, 10 ... Sleeve, 11 ... Magnetic pole, 11
&...Through hole, 12...Anode, 13...M
0 powder paste, 14...Ru-Mo powder brazing filler metal, 1
5...Spacer, 1Sa...Cavity part, 15b...
... Cylinder part, 15e ... Leg part, 16 ... Magnetic pole, 16a ... Through hole. 15- Figure 3 to) Tbl Figure 4 Temperature ("C1 Figure 5 Figure 7 Figure 6 Figure 8 Figure 9. $10 Figure 6 112- vf- and

Claims (1)

[Claims] 10. A filament that emits thermoelectrons, an upper end shield and a lower end shield fixedly arranged at the upper and lower ends of the filament, a center lead fixed to the upper end shield, and a side lead fixed to the lower end shield. 1. A magnetron cathode assembly comprising: a high-purity alumina ceramic spacer disposed between the center lead and an electrode member disposed close to the center lead. 2. The magnetron cathode structure according to claim 1, wherein the high-purity alumina ceramic spacer has an alumina purity of 98 or higher.