JPH02244533A - Impregnation type cathode structure for electron tube - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] [Industrial Field of Application] The present invention provides a method for connecting and assembling each member with a simple press-fitting operation.
Moreover, the present invention relates to an impregnated cathode assembly for an electron tube that has good thermal efficiency.

[Prior Art] Impregnated cathodes for electron tubes can contain a large amount of electron-emitting material, and have long been seen as promising as high-performance cathodes that can maintain high-density electron current emission over long periods of time. . However, sufficient electron emission cannot be obtained unless the temperature is much higher than that of a normal indirectly heated oxide cathode, which limits the material of the components, and it is quite difficult to obtain good thermal efficiency. Due to things etc.

The reality is that it has not yet become widely used.

An impregnated cathode used as a high electron current density cathode consists of a cathode base made of a porous sintered body of a high-melting point metal such as tungsten or molybdenum impregnated with an electron-emitting substance such as barium calcium aluminate, and A cup made of a high-melting point metal such as tantalum or molybdenum that stores the heat exchanger, and a sleeve made of a high-melting point metal such as tantalum or molybdenum that houses the heater through an opening at the other end. It is equipped with conventionally,
The cathode substrate is inserted into the cup, which is further inserted into the end of the sleeve, and laser light is irradiated from the side.

It was fixed by welding.

The cathode substrate is usually made of tungsten with a melting point of <337°C, and the cup and sleeve are made of tantalum with a melting point of 2940°C or molybdenum with a melting point of 2617°C. It is necessary to heat the metal to at least the melting point of the metal. However, there is a problem in that the cathode substrate is impregnated with an electron-emitting substance, and this electron-emitting substance may melt and evaporate during laser welding, creating a hole in the metal wall at the welding location.

When such an impregnated cathode was incorporated into an electron tube and a life test was conducted, a phenomenon in which the cutoff voltage changed significantly was observed. Also, when this electric f/tube was disassembled and investigated, it was found that the cathode base fell off from the cup with a slight force.

In order to deal with the above-mentioned problems, for example,
No. 108233 discloses that a solution phase is interposed between the cathode substrate and the cup, and Japanese Patent Application Laid-Open No. 111222/1983 discloses that a solution phase is interposed between the cathode substrate and the cup.
According to the publication, four parts are formed on the side wall of the cathode base, and the protruding parts of the cup obtained by irradiating and melting the parts of the cup corresponding to the four parts with a laser beam are engaged and fixed in the marked recesses of the cathode base. It is disclosed that the cathode substrate is fixed using a method of fixing the cathode substrate.

[Problems to be Solved by the Invention] All of the above-mentioned conventional techniques propose an improvement over the difficulty in directly welding a cup to a cathode base made of porous tungsten impregnated with an electron-emitting substance. However, the former could not be firmly fixed, and the latter had problems with workability.

The present invention includes a cathode substrate, a cup, and a sleeve.

An object of the present invention is to provide an impregnated cathode structure for an electron tube that can be assembled and fixed in place.

[Means for Solving the Problems] In order to achieve the above object, in the present invention, a porous sintered body of a high melting point metal or a cathode substrate is shaped like a truncated right cone (the cross section is a trapezoid with a short L side and a long bottom side). ), and place it into a bottomed cylindrical cup with an opening diameter approximately equal to the small diameter of the two parts of the truncated right circular cone, with the lower large diameter side first in the coaxial direction. The large-diameter surface of the cup was force-fitted until it reached the bottom surface of the cup, and then the bottom surface was inserted into a hole smaller than the outer diameter of the bottom surface of the cup, which had been previously drilled in the bottom surface of the bottomed cylindrical sleeve, from the outside on the side opposite to the sleeve opening. First, we decided to assemble the cathode structure by forcibly press-fitting the cup in the coaxial direction until it reached the periphery of the hole in the bottom of the sleeve, thereby fixing it to the porous sintered body or cathode substrate through the cup to the sleeve. .

[Effect] The bond between the cathode base, cup, and sleeve is fixed.

In the present invention, this is carried out mechanically by the elastic stress of the component metal plate material due to the trapezoidal cross-sectional shape of the cathode substrate and the hole diameter of the sleeve fitting portion.

[Example] The figure shows a cathode substrate according to an embodiment of the present invention, in which a tungsten porous sintered body in the shape of a truncated right cone is impregnated with an electron-emitting substance] , is a side view of.

FIG. 2 is a sectional view of a molybdenum cup 2 of the same embodiment, the inner diameter of which is approximately equal to the bottom diameter of the cathode substrate 1, and which has a flange around the opening.

FIG. 33 shows that the cathode substrate 1 is force-fitted into the cup 2, and then it is force-fitted from the outside in the direction opposite to the opening into a hole slightly smaller than the outside diameter of the cup on the bottom surface of the bottomed cylindrical sleeve 3. Assembly of the impregnated cathode structure for an electron tube according to the invention is completed! FIG. The heater not shown is
Then open the sleeve (insert from the -1 side).

When assembling, first the 13-pole substrate 1 is made with a wall thickness of 50 μm.
Using a jig in a molybdenum cup, apply a pressure of 0.5 to
1. Forcibly press-fit in the coaxial direction with kg g. This allows the bottom of the cup to sag somewhat. The assembled cup is forcibly inserted into the hole at the top (bottom) of a molybdenum sleeve with a wall thickness of 100 μm using a pressure of 1 kg until the flange of the cup reaches the surface around the hole in the sleeve, and the assembly is completed.

In the cathode structure assembled in this way, the cup is fixed to the sleeve by the force that tightens the lower surface of the flange of the cup around the hole at the top of the sleeve, and the cathode base is firmly fixed to the cup by having a trapezoidal cross section. has been done.

When the cathode structure of this example was incorporated into an electron tube and investigated, it was confirmed that it had good thermal efficiency and that it did not deform or fall off even after conducting a life test equivalent to long-term actual use using a forced heat run. Ta.

[Effect of the invention] As explained above, according to the present invention, there is provided a cathode substrate.

Since the cup and sleeve are bonded and fixed by one mechanical method, the manufacturing process is shortened, and the bottom of the cup is directly inserted into the sleeve, resulting in good thermal efficiency.

[Brief explanation of drawings]

FIG. 1 is a side view of a cathode substrate of one embodiment, FIG. 2 is a side sectional view of a cup of the same embodiment, and FIG. 3 is a side sectional view of the cathode assembly of the same embodiment after assembly. 1... Cathode substrate, 2... Cup, 3...
sleeve. Part 1 New Part 2 Figure Ichishoko No. 1-1 to Toga 2-Totsu 3-zu I)-

Claims (1)

[Claims] 1. A porous sintered body of a high-melting point metal or a cathode substrate made of a porous sintered body impregnated with an electron-emitting substance is housed in a cup made of a high-melting point metal, and this cup is placed in a high-temperature chamber in which a heater is housed inside. In an impregnated cathode structure for an electron tube attached to the end of a sleeve made of a melting point metal, the porous sintered body or cathode substrate is formed into a truncated right cone shape, and the opening diameter is a small diameter at the top of the truncated right cone. Into a bottomed cylindrical cup with flanges around the opening, the lower large diameter side is force-fitted coaxially until the large diameter side reaches the bottom of the cup, and then the bottom of the bottomed cylindrical sleeve is inserted. By force-fitting the cup into a pre-drilled hole smaller than the outer diameter of the bottom surface of the cup from the outside on the opposite side to the sleeve opening, the bottom surface first coaxially until the flange of the cup reaches around the hole in the bottom surface of the sleeve. An impregnated cathode structure for an electron tube, characterized in that it is assembled by fixing a porous sintered body or a cathode substrate to a sleeve via a cup.