JPH06162916A - Impregnation type cathode structural body and manufacture thereof - Google Patents

Abstract

PURPOSE:To provide an impregnation type cathode structural body of high reliability of tungsten pellet fixture and a favorable heat efficiency of a structure in which a tungsten pellet in which electron radiating agent is impregnated is welded and fixed on a cap sleeve. CONSTITUTION:A welded surface of a tungsten pellet 8 is covered with tungsten metal, and a mechanical polishing method is used as a means. As the welded surface of the tungsten pellet is polished mechanically, the whole body of the welded surface is covered with flowing tunsten because of favorable expansion property, so weld performance is improved extremely. An impregnation type cathode structural body of favorable reliability of mechanical fixture after welding and of favorable heat efficiency can thus be realized.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an impregnated cathode used in a CRT or the like, and more particularly to a structure for fixing a tungsten pellet and a cap sleeve of the impregnated cathode.

[0002]

2. Description of the Related Art Conventionally, the manufacturing process of this type of impregnated cathode has been shown in FIG. (A)-(d) shows a manufacturing process sequence.

In FIG. 2, 21 is a tungsten powder sintered pellet, 22 is a melted electron emitting agent, 23 is an electron emitting agent residue, 9 is a cap, 10 is a sleeve, and 11 and 1.
1'is a welding electrode.

The outline of the manufacturing process will be described. Tungsten powder is formed into pellets and sintered in a hydrogen furnace to obtain tungsten powder sintered pellets 21 (FIG. 2A).

When the pellet 21 and the electron emitting agent 22 are put into a high melting point container and heated, the electron emitting agent 22 is melted and penetrates into the pellet 21 (FIG. 2 (b)).

When the pellet 21 is taken out from the electron emitting agent 22 and cooled, an impregnating agent residue 23 adheres to the surface of the pellet 21 (FIG. 2 (c)).

However, since the pellets 21 are very small (diameter 1 mm, thickness 0.4 mm) and are difficult to handle, and the impregnating agent residue 23 is firmly stuck and difficult to remove easily, it remains insufficiently removed. Cap the pellets 21,
It was fixed to the sleeve 10. After that, the heater 12 is inserted from the side opposite to the pellet 21 of the sleeve 10, and the pellet 21 is heated by the heater 12 to emit thermoelectrons.

[0008]

By the way, in the above-mentioned conventional impregnated cathode, the impregnating agent residue of the electron emissive agent adheres to the entire surface of the tungsten pellet including the surface to be welded. Since the residue of the impregnating agent of the electron emitting agent is an oxide of barium, calcium or aluminum, it cannot be welded to the metallic cap and sleeve at all. For this reason, the weldability between the cap and the sleeve is very poor, and even if the tungsten pellet and the cap sleeve or the tungsten pellet and the sleeve are welded, a considerable amount of unwelded portion remains.

Therefore, there are drawbacks that the mechanical fixing of the tungsten pellets is insufficient and thus the reliability is low, and that the heat conduction from the heater to the tungsten pellets is insufficient and the thermal efficiency is lowered.

In view of the above-mentioned drawbacks of conventional products, an object of the present invention is to impregnate tungsten pellets with perfect mechanical fixing, high reliability, sufficient heat conduction from the heater to the tungsten pellets, and high thermal efficiency. Type cathode structure.

[0011]

The impregnated cathode of the present invention comprises: (1) covering the surface of the tungsten pellet to be welded with tungsten metal; and (2) the means of (1) above, where the tungsten pellet is welded. The surface is mechanically polished so that only the tungsten in the tungsten pellet is spread on the surface to be welded.

[0012]

[Function] Since tungsten metal is highly spreadable, when the surface of the tungsten pellet is ground with a grindstone, the surface of the tungsten pellet where the electron emissive agent was exposed before polishing is covered with the spread tungsten metal. .

According to the above structure, the welded surface of the tungsten pellet is covered with the tungsten metal, and the tungsten is easily welded to the cap and the sleeve, so that the weldability of the tungsten pellet is improved. This provides good welding of the tungsten pellet and cap sleeve or the tungsten pellet and sleeve. As a result, the mechanical fixation of the tungsten pellets will be sufficient and reliability will be obtained, and since there will be no gap between the tungsten pellets and the cap / sleeve, the heat conduction from the heater to the tungsten pellets will be good and the thermal efficiency will be improved. A good cathode is obtained.

[0014]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to the drawings.

FIG. 1 is a manufacturing process diagram of an embodiment of the present invention. (A)-(h) shows a manufacturing process sequence.

Regarding the point of using HIP discharge (hot isostatic pressing method) in the sintering step (b) of the tungsten powder and the electron emissive agent in this Example, JP-A-3-557.
It is published in No. 39.

In FIG. 1, 1 is a molded product obtained by mixing and molding tungsten powder and an electron emitting agent, and 2 is a HI molded product.
Sintered body formed by P treatment, 3 is a state in which the sintered body is cut into square rods, 4 is the square rods, 5 is a round rod obtained by mechanically polishing the square rods, and 6 is a machine. Grinding stone for dynamic polishing, 7 is a state in which a round bar is cut into pellets, 8 is a pellet, 9 is a cap, 10
Is a sleeve, and 11 and 11 'are welding electrodes.

In FIG. 1E, the tungsten square rod 4
The periphery is mechanically polished by a grindstone 6 and processed into a round bar 5. Since the tungsten square rod 4 is a mixture of tungsten powder and an electron emitting agent in a volume ratio of about 7: 3, about 30% of its surface is the electron emitting agent, and this portion is welded to the cap sleeve as it is. I don't get it. However, when the square bar 4 is mechanically polished by the grindstone 6, since tungsten has good spreadability, the polished surface of the round bar 5 is completely covered with the flowing tungsten film, and the exposed portion of the electron emitting agent is eliminated. Therefore, the side surface of the pellet 8 made of the round bar 5 has weldability as good as that of pure tungsten. Therefore, when the pellet 8 is fitted into the cap 9 and the sleeve 10 and resistance welding is performed as shown in FIG. 1 (h), the pellet 8 and the cap 9 and the sleeve 10 are well welded, and mechanical fixation is sufficiently strong. In addition, an impregnated cathode having high reliability and thermal efficiency with no heat conduction loss is realized.

In the above description, the welding method is resistance welding, but the welding method is not limited to this, and the same effect can be exhibited by laser welding, electron beam welding or the like.

Further, the grain size of the grindstone 6 is around 600 to 800, and a suitable roughness is 10 nm or more.
If the number is 00 or more, the tungsten is too fine to spread and the weldability is not improved. On the other hand, if the grain size is 400 or less, the surface of the tungsten pellet is too rough and welding with the cap and sleeve is not successful. As for the composition of the grindstone 6, any of ordinary ones such as SiC, Al ₂ O ₃ and CBN can be used.

[0021]

As described above, according to the present invention, the welded surface of the tungsten pellet is covered with the tungsten metal to improve the weldability, so that the welding of the tungsten pellet and the cap or the sleeve becomes good. Therefore, there is an effect that an impregnated cathode having high mechanical fixation reliability and thermal efficiency can be realized.

[Brief description of drawings]

FIG. 1 is a manufacturing process drawing of an embodiment of an impregnated cathode of the present invention.

FIG. 2 is a manufacturing process diagram of a conventional impregnated cathode.

[Explanation of symbols]

1 molded body in which tungsten powder and electron emissive agent are mixed and molded 2 sintered body made by HIP treatment 3 state where the sintered body is cut into square rods 4 square rods 5 round rods 6 polishing whetstone 7 round rods into pellets Cut state 8 Pellet 9 Cap 10 Sleeve 11, 11 'Welding electrode 12 Heater 21 Tungsten powder sintering pellet 22 Molten electron emissive agent 23 Electron emissive residue

Claims (3)

[Claims] 1. An impregnated cathode assembly having a structure in which a tungsten pellet impregnated with electron radiation is fitted into a cap and a sleeve or a sleeve alone and the tungsten pellet / cap / sleeve or the tungsten pellet / sleeve is fixed by welding. An impregnated-type cathode assembly in which the weldability of the welded surface is improved by covering the welded surface of the tungsten pellet with tungsten metal. 2. An impregnated cathode characterized in that only tungsten in the tungsten pellet is spread on the welded surface by using mechanical polishing as a means for covering the welded surface of the tungsten pellet with tungsten metal. Structure manufacturing method. 3. A cathode ray tube (CRT) using the impregnated cathode structure.