JPS6026438Y2 - Cathode structure for electron tube - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a cathode assembly for an electron tube having an impregnated cathode substrate.

It is known that an impregnated type cathode is used as a cathode structure for an electron tube with high output, and a cathode structure for an electron tube made of such an impregnated cathode has an electron emitting substance in a high melting point porous metal base such as tungsten. A heater housing chamber filled with an insulating material is provided on the back side of the cathode substrate.

In general, a cathode assembly for an electron tube made of such an impregnated cathode can generate a high output current of about 2 A/all, but its operating temperature is also higher than that of a cathode assembly for an electron tube, even if it is made of an oxide cathode, and is approximately 1000 The temperature is between 1200°C and 1200°C.

There are various structures of cathode structures for electron tubes made of such impregnated cathodes, and a typical example will be explained with reference to FIG.

That is, the cathode structure for an electron tube has a cylindrical shape in which a molybdenum heater housing chamber is formed on the back side of a cathode substrate 1 which is made by impregnating a porous metal substrate with a high melting point such as tungsten with an electron emitting substance and processing it into a predetermined shape. Ru with side wall 2 not shown
- A heater 3 which is fixed with a high melting point brazing material such as Mo and is wound in a ring shape is provided inside the housing chamber.

In this case, as mentioned above, the operating temperature of the cathode is high, and the heater 3 that heats the cathode substrate 1 having a high melting point also has a temperature of 1500°C to 16°C.
Because the temperature is as high as 00°C, the heater 3 is usually filled in the heater housing chamber together with an insulator 4 made of alumina or the like, and a structure is adopted that takes into consideration the improvement of heat transfer efficiency, thereby extending the life of the heater 3. It is becoming more and more popular.

This insulator 4 is sintered at a high temperature and effectively transfers the heat generated by the heater 3 to the cathode base 1.

The heater lead 3a of the heater 3 integrated with the insulator 4 is electrically insulated from a pair of through holes 5 formed in the bottom wall 6 of the storage chamber made of molybdenum or the like via an insulator (not shown). It's being pulled out.

The bottom wall 6 of this heater storage chamber is fixed together with the side wall 2 to a support cylinder 7 which serves as a path for taking out the cathode current by edge arcing or the like.

In such a structure, the heat from the heater 3 not only heats the cathode substrate 1, but also is directly bonded to the side wall 2 and bottom wall of the heater housing chamber made of molybdenum or the like to the same extent by thermal conduction. Much of the energy is transmitted to the support cylinder 7.

In order to suppress such heat loss, it is conceivable to form the support cylinder 7, which also serves as a path for the cathode current, to be as thin as possible.

However, the support cylinder 7 includes the cathode substrate 1, the heater 3,
Insulator 4, side wall 2 and bottom wall 6 forming a heater housing chamber
It is necessary to stably support the heater 3 and to prevent undesirable deformation due to thermal strain caused by repeated power on and off to the heater 3.

For this reason, the supporting cylinder 7 must be made thick to some extent, and heat conduction to the supporting cylinder 7 increases.

Moreover, because of this and the fact that the disk-shaped cathode substrate 1 is heated by the ring-shaped heater 3, the substrate 1
The temperature distribution is high in the center and low in the periphery, resulting in thermal imbalance.

This invention eliminates the disadvantages of the conventional structure as described above,
An object of the present invention is to provide an impregnated cathode structure for an electron tube that can improve thermal efficiency and uniformity of temperature distribution of a cathode substrate.

Examples thereof will be described below with reference to the drawings.

Identical parts are designated by the same symbols.

The cathode structure of the embodiment shown in FIG. 2 has an impregnated layer cathode base 11 in which a high melting point porous metal is impregnated with an electron emitting substance,
The upper surface is formed as a concave electron emitting surface 11a,
A cylindrical storage chamber side wall 12 made of molybdenum or the like is provided on the back side of the outer periphery, and a long central support cylinder 18 with a small diameter is provided on the back side of the center portion.
The upper ends 18a of each are soldered and fixed by a high melting point solder material such as Ru--Mo.

The inner space formed by these side walls 12 and the central support cylinder 18 is filled with a heat-resistant insulator 14 such as alumina or itria, and is wound in a ring shape within this insulator and has extended heater leads 13a at both ends. However, part 13 is buried.

A bottom wall 16 also made of an annular molybdenum plate is fixed to the lower end of the cylindrical side wall 12 by edge arc welding or the like.

Therefore, a through hole is formed in the center of the bottom wall 16, and the central support tube 18 is inserted through this through hole with an extremely small gap g maintained.

This gap g facilitates the fitting and assembly of the center support tube 18 and the bottom wall 16, and also makes the heat transfer from the bottom wall to the center support tube 18 almost negligible compared to the case where the two are directly welded. This is to make it as small as possible.

In this way, the back surface of the cathode substrate 11, the side wall 12, the bottom wall 16, and the central support cylinder 18 constitute a heater housing chamber 15 that is substantially sealed.

Note that the heater lead 13a is drawn out downward from a through hole formed in a part of the bottom wall 16.

A disk-shaped intermediate holding plate 1
9 is fixed by edge arc welding.

A through hole 20 is also formed at a predetermined position in this holding plate 19 to allow the heater lead to pass therethrough in an insulative manner.

The lower end 21b of the intermediate support tube 21, which is coaxially arranged inside the outer support tube 17, is fixed to the outer peripheral edge of the holding plate 19 by edge arc welding.

The outermost support cylinder 17 coaxially surrounds the cathode base 11 and the cylindrical side wall 12, and has an upper end 17a.
is extended to the vicinity of the cathode substrate 11.

The upper end 21a of the intermediate support cylinder 21 is fitted inside the upper end 17a of the support cylinder 17, and fixed at the position X by edge arc welding.

Most of the intermediate support cylinder 21 is disposed between the outer support cylinder 17 and the cathode base and side wall 12 so as to be spaced apart from them.

In this way, the cathode substrate 11 and the heater housing chamber member are mechanically supported and electrically connected to the upper end of the outer support cylinder 17 via the central support cylinder 18, intermediate holding plate 19, and intermediate support cylinder 21. has been done.

Inside the support cylinder 17, further below the intermediate holding plate 19, two heat shielding plates 22 and 23 are arranged at a distance.

To assemble this cathode structure into an electron tube, the lower end of the outer support cylinder 17 is fixed to the stem (not shown) of the electron tube.

According to the above-described cathode structure of the embodiment of the present invention, the heat generated by the heater is not easily conducted to the outer support cylinder, and the intermediate support faces the cathode base and the side walls and bottom wall forming the heater housing chamber. Since the cylinder and intermediate holding plate exhibit a heat reflecting function, the cathode substrate is effectively heated.

In particular, since a central support cylinder is fixed to the back side of the central part of the cathode substrate, and the cathode substrate is mechanically supported by the central support cylinder to the outer support cylinder, the heater wound in a ring shape can keep the temperature relatively high. The heat in the central part, which is prone to heat dissipation, is conducted to this central support tube, which suppresses the rise in temperature in the central part of the cathode.On the other hand, the side and bottom walls of the heater housing chamber, which are joined to the outer periphery of the cathode and easily dissipate heat, are directly supported in the central support tube. Since the gap g is formed without being joined to the cylinder, heat dissipation from these side walls and the bottom wall to the support cylinder is suppressed, and the synergistic effect of these effects equalizes the temperature distribution of the disc-shaped cathode substrate and achieves thermal equilibrium.

As described above, according to the present invention, it is possible to obtain an impregnated cathode structure with excellent heating efficiency and balance of temperature distribution of the cathode substrate.

In the embodiment shown in FIG.
The lower end portion 21b of the tapered portion is directly fixed to the lower end portion 18b of the central support cylinder 18 by welding.

A through hole 20 is bored in a predetermined position of the intermediate support tube 18 to allow the heater lead 13a to pass therethrough without contact.

The cathode assembly of this embodiment has the same effects as those of the previous embodiment, and also has fewer parts and a simpler structure.

As explained above, according to the present invention, it is possible to obtain an impregnated cathode assembly for an electron tube that has excellent heating efficiency and excellent balance of temperature distribution in the cathode substrate.

[Brief explanation of the drawing]

FIG. 1 is a vertical cross-sectional view of a main part showing a conventional structure, FIG. 2 is a vertical cross-sectional view of a main part showing an embodiment of the present invention, and FIG. 3 is a longitudinal cross-sectional view of another embodiment of the present invention. . 11... Cathode base, lla... Electron emission surface, 12... Outer wall of heater housing chamber, 13...
... Heater, 14 ... Insulator, 15.
... Heater storage chamber, 16 ... Bottom wall, 17
......Outer support cylinder, 18...Central support cylinder, 19...Intermediate holding plate, 21...Intermediate support cylinder.

Claims (1)

[Claims for Utility Model Registration] On the back side of the disc-shaped impregnated cathode substrate 11, a part of an annular heater accommodating chamber 15 for accommodating a ring-shaped heater 13 and an insulator 14 is formed. The side wall 12 and the bottom wall 16 are joined, and a supporting cylinder 17 is disposed around the outer periphery of the cathode base 11 and the side wall 12 to hold them coaxially and spaced apart and to serve as a current path for the cathode base 11. In the tube cathode structure, one end 18a of a small-diameter central support tube 18 is fixed to the back side of the central portion of the impregnated cathode substrate 11, and the other end 18b is slightly inserted into the central through hole formed in the bottom wall 16 of the storage chamber. gap g
The central support cylinder 18, the storage chamber side wall 12, and the bottom wall 16 constitute the annular storage chamber that accommodates the heater 13 and the insulator 14, and the upper end 17a of the support cylinder 17 is a cathode. It extends to the vicinity of the outer circumference of the base body 11, and an intermediate support tube 21 is coaxially disposed inside the base body 11, and an upper end portion 21a of this intermediate support tube 21 is fixed to an upper end portion 17a of the outer support tube body 17. , this intermediate support cylinder 21
A cathode assembly for an electron tube, characterized in that a lower end portion 21b is fixed to a lower end portion 18b of the central support cylinder 18.