JPS60163331A - Electron tube cathode structure - Google Patents

Abstract

PURPOSE:To improve the supporting accuracy of a center lead straight portion and the productivity by attaching a ring-shaped metal element on the spacer center hole penetrating part of the center lead and by soldering a filament to the upper and lower shields. CONSTITUTION:A center lead 4 is inserted through the center hole of a spacer 10, and this spacer 10 is fitted into the through-hole of a lower end shield 3. Right under the center hole of the spacer 10, an O-ring 12 made of a high melting point metal wire such as Mo or W wire is forcibly fitted on. A filament 1 is fixed to the lower end shield 3 and the upper end shield 2 by use of a soldering material 13. The O-ring, which is made of Mo or W wire and formed into a C- ring shape, becomes smooth in fitting by moving up and down along the center lead 4, and the positioning adjustment in the vertical direction can be easily made. With such a configuration, it is possible to support the straight portion of the center lead 4 with high accuracy and to improve the productivity.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to a low-cost electron tube cathode structure having a small lead wire diameter, high vibration resistance, and suitable for use in magnetrons and the like.

[Background of the invention]

Currently, helical filament cathodes using thorium tungsten are widely used in magnetrons. This thorium tungsten wire is used with its surface layer subjected to carbonization treatment in order to increase electron emission efficiency. The carbonized portion becomes brittle, and the center lead and side leads, which support the helical filament and are connected to the lower end shield, may resonate due to external vibrations, causing the filament to break. To prevent this, it is possible to increase the rigidity by increasing the diameter of the center lead and side leads, but these lead wires are made of expensive high-melting point metals such as W and MO. , which increases the cost. Therefore, it has been proposed to use relatively thin lead wires and construct the cathode structure as a whole, which consists of a center lead, side leads, etc., as shown in FIG. 1, so that it is relatively durable. That is, in the figure, upper and lower end shields 2.3 are fixedly supported at the ends of the center lead 41 and side leads 5, respectively, so as to sandwich the filament 1, and heat-resistant material such as alumina porcelain is inserted into the through hole of the lower end shield 3. Spacer 10 made of an insulator
is fitted with the center lead 4 inserted into its center hole. Here, a groove 4a is previously provided in the center lead 4, and a stopper 11 is fitted therein to prevent the spacer 10 from moving in the axial direction. With this structure, the center lead 4 and the side leads 5 appear to be integrated with each other via the spacer 10, and have a great vibration-proofing effect. In other words, with such a structure, even if a relatively thin lead wire is used, it will not be a problem.

In this structure, a groove 4a is provided in the center lead 4, and a stopper 11 is fitted into the groove 4a.What is extremely complicated is that the filament 1 and the upper and lower end shields 2, 3 are
If R[@M, alloy is used as the brazing material for connection with the spacer 10, the temperature must be raised to approximately 1950 to 2000°C for fusion, whereas the firing temperature of alumina porcelain, which is the material of the spacer 10, is approximately 1700°C. Since the temperature is ~1800℃, when brazing the filament 1 and the upper and lower end shields 2.3, lower the spacer 10 to the position shown by the dotted line in Figure 1 and lower it after the brazing is completed. end shield 3
The spacer 10 is fitted into the 0 through-hole, and the brazing is done so that the spacer 10 does not receive the high temperatures during operation. In FIG. 1, 6 is a terminal, 7 is a stem ceramic, and 8 is a seal component.

As a haze that has improved this problem, an electron tube cathode structure as shown in FIG. 2 has been proposed. That is, in the figure, a bent portion 4b is provided on the center lead 4 directly below the normal (in use) position of the spacer 10, and prevents the spacer 10 from moving in the axial direction. Also,
The filament 1 and the upper and lower end shields 2 and 3 are brazed using a brazing material such as PT, which has a melting point of about 1800°C or less, that is, the alumina porcelain firing temperature of the spacer 10 or less. This prevents the spacer from being adversely affected during work. In this way, when the groove 4a (see Figure 1) is provided in the center lead 4, when the stopper 11 (see Figure 1) is used, and when the spacer 10 is lowered, the brazing can be carried out after the brazing operation is completed. end shield 3
0 No need for work or parts such as fitting into the through hole.
Therefore, an electron tube cathode structure with sufficiently high vibration resistance can be obtained without requiring the above-mentioned complicated structure and process and using relatively thin lead wires as in the conventional case.

However, the electron tube cathode assembly constructed in this manner has the following drawbacks.

That is, (1) since the spacer 10 is supported by the bent portion 4b of the center lead 4, the length of the straight portion from the bent portion 4b of the center lead 4 toward the upper end shield 2 at the tip is shortened; As shown in the figure, center lead 4. Side lead 5. During so-called "stem assembly" in which the terminal 6° stem ceramic T and the seal component 8 are assembled together in advance, the accuracy of supporting the straight portion of the center lead 4 is reduced.

(2) Since the spacer 10 is slightly inserted tb into the bent portion 4b of the center lead 4, the spacer 10 tends to be inclined in a certain direction with respect to the bent portion 4b.

(2) Positional accuracy of the bent portion 4b of the center lead 4 is strictly required, and the shape of the bent portion 4b is also required to be made of metal with almost no curvature, so management of the metal is also important.

[Purpose of the invention]

Therefore, the present invention has been made in view of the above-mentioned drawbacks.The purpose of the present invention is to improve the support accuracy of the straight part of the center lead, and to improve productivity by eliminating problems in mass production management. It is an object of the present invention to provide an electron tube cathode structure which has the following characteristics.

[Summary of the invention]

In order to achieve such an object, the electron tube cathode structure according to the present invention prevents the spacer from moving in the axial direction by providing a ring-shaped metal body made of a high melting point metal in the part of the center lead through which the spacer center hole is inserted. The filament is then heated using a brazing filler metal whose melting point is below the melting temperature of the spacer.
Brazing is used to fix the lower end shield.

[Embodiments of the invention]

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

FIG. 3 is a cross-sectional view showing one embodiment of the electron tube cathode assembly according to the present invention), and the same parts as those in the previous figures are given the same reference numerals, and the explanation thereof will be omitted. In the same figure, there is an MO or W
An O-ring 12 made of a high melting point metal wire such as wire is forcibly fitted. The 00 ring 12 includes the filament 1, the upper end shield 2, and the filament 1 and the lower end shield 3, as shown in an enlarged sectional view of the main part in FIG. The center lead 4 as well as the joints between the lower end shield 3 and the side leads 5 are coated with a brazing material such as Ru-Mo-N1 or P which has a melting point lower than that of the ceramic.
It is fixed by a metal brazing material 13 such as T33 brazing material. In this case, the O-ring 12 is temporarily fixed in the fitted state after inserting the spacer 1° into the through hole of the lower end shield 30, and the above-mentioned joint parts are fused and fixed at the same time to the metal brazing material 13. let The O-ring 12 used here is formed by molding Mo or W wire into a C-ring shape as shown in FIG. As shown in the figure, the curved folded portions 12a and 12b are provided at both ends and formed by molding, so that the fitting with the center lead 4 can be made loose by holding both ends with a set of pins or the like. Moreover, the respective vertical positions can be easily adjusted.

According to this configuration, the support position of the spacer 1o to the center lead 4 is adjusted and fixed with little loosening relative to the lower end shield 3, so that the straight portion of the center lead 4 is supported with high precision. At the same time, high vibration resistance can be obtained. Further, as described above, the groove portion 4a of the center lead 4 shown in FIG. 1 is not required, and the support by the bent portion 4b shown in FIG. 2 is not required, so that productivity can be greatly improved.

FIG. 7 shows another embodiment of the present invention, in which a metal oxide layer 10a is formed on the outer peripheral surface of the spacer 10.
and 72-inch part 10b are provided, and the filament 1
During brazing, the spacer 10 is also fixed to the brazing material 13 at the same time.

According to such a configuration, since the spacer 10 is completely fixed to the lower end shield 3, the straight portion of the center lead 4 is supported with high precision, and the degree of freedom of vibration between the center lead 4 and the side leads 5 is reduced. is further restricted, and vibration resistance can be further improved. In addition, in this embodiment, the case where the flange portion 10b was provided as the shape of the spacer 10 was explained, but the present invention is not limited to this shape, and a cylindrical shape may also be used, and the flange portion 10b is shown in FIG. A similar effect can be obtained even if the structure is provided on the lower side as in the shape shown. However, by adopting the configuration shown in FIG. 7, there is no fear that the spacer 10 may sometimes fall downward when brazing the spacer 10.
There is no need to use special jigs, and therefore mass productivity can be improved.

In addition, as another embodiment, the O-ring 12 described above may have its surface plated with the brazing filler metal 13 in advance, or may be formed by applying the brazing filler metal 13 in the form of a base and firing it. You may do so. Of course, the O-ring 12 to which the brazing material 13 is not attached may be fitted onto the center lead 4, and the brazing material 13 may be applied before brazing.

〔Effect of the invention〕

As explained above, according to the present invention, it is possible to obtain an electron tube cathode structure with sufficient vibration resistance and assembly accuracy, easy mass production management, and high productivity while using relatively thin lead wires. have

Brief description of the drawings - Figures 1 and 2 are cross-sectional views showing an example of a conventional cathode structure;
FIG. 3 is a cross-sectional view showing one embodiment of the present invention, and FIG.
5 and 6 are plan views showing the Qlj ring, and FIG. 7 is an enlarged sectional view of the main parts showing another embodiment of the present invention.

1...Filament, 2...Top end shield, 3,000 end shield, 4. .

...Center lead, number 5...Side lead, 10-
-ψ・Spacer, 10aII・・Non metalized layer, 10
b-φ...7 rank part, 12...0 ring, 12a
, 12b...Folded part, 13. Fist 11Φ brazing material.

Figure 1 Figure 3 to

Claims (1)

[Claims] A helical filament that emits thermoelectrons is sandwiched between upper and lower end shields located at both ends of the filament, and the upper end shield is inserted into the center hole of a spacer made of a cylindrical heat-resistant insulator that fits into the lower end shield through hole. In the electron tube cathode structure, the lower end shield is fixedly supported at the end of the inserted center lead, and the lower end shield is fixedly supported at the end of the side lead at the outer periphery of the through hole. A ring-shaped metal body is provided to prevent the spacer from moving in the axial direction, and the filament is brazed to the upper and lower end shields using a brazing material whose melting point is lower than the melting temperature of the spacer. Electron tube cathode structure.