JPH04179023A - Impregnated cathode and its manufacturing method - Google Patents

Abstract

PURPOSE:To rigidly fix a cathode base body and a cup to each other by shaping the cathode base body into a truncated conic body of which top face is smaller than the bottom face, and fixing it at the upper part of the cup side surface. CONSTITUTION:A porus sintered body or a cathode base body 2 is press-shaped into a head-cut conic body (truncated conic body) of which top face is smaller than the bottom face by cutting its head. Then, after it is created by means of sintering, the cathode base body 2 is inserted in a cup 3 made of a high melting point metal and cramped by applying a mechanical external pressure locally on the upper part 5 of the cup side surface. Thus, it is constructed so that the cathode base body 2 can be mechanically fixed to the cup and the cathode base body 2 can not geometrically be removed upward off from the cup 3. Therefore, the cathode base body 2 and the cup 3 can be rigidly fixed to each other without causing decomposition of an electron emission substance which is dissolved and impregnated in manufacturing process.

Description

Detailed Description of the Invention [Industrial Application Field] The present invention provides at least a porous sintered body of a high melting point metal or a cathode substrate in which the sintered body is melted and impregnated with an electron emitting substance, and a cup made of a high melting point metal. An impregnated cathode comprising a sleeve made of a high melting point metal and a method for manufacturing the same,
In particular, the present invention relates to an impregnated cathode that can firmly fix the porous sintered body or cathode substrate and the cup using a simple method, and a method for manufacturing the same.

[Prior Art] An impregnated cathode used as a high current density cathode is a porous sintered body of a high-melting point metal such as tungsten (W) or molybdenum (MO) and barium-calcium-aluminate (BaO-Ca0- Equipped with a cathode substrate formed by melting and impregnating an electron emitting substance such as Al, O, ), a cup made of a high melting point metal such as tantalum (Ta) or MO, and a sleeve made of a high melting point metal such as Ta or Mo. This is what happens. In this regard, regarding the fixation of the cathode base and the cup, the outer diameter of the cylindrical cathode base and the inner diameter of the cylindrical cup have been made almost the same, and after the cathode base is press-fitted into the cup, the side surface of the cup is fixed. The method of fixing by caulking has been adopted.

However, when an impregnated cathode having such a configuration is mounted in an electron tube and operated, a phenomenon may occur in which the cutoff voltage changes significantly during the life of the electron tube. When such electron tubes were disassembled and investigated, it was found that the cathode base often fell off with a slight force, that is, the adhesion between the cathode base and the cup was insufficient in some cases.

In order to deal with the above problems, 1, for example,
As described in Japanese Patent Application Laid-open No. 9-108233, a welding material is interposed between the cathode base and the cup, or a recess is formed in the side wall of the cathode base as described in JP-A-59-111222. A method has been proposed in which the cathode substrate is fixed to the cup by fixing the concave portion to the protruding portion of the cup obtained by irradiating a laser beam to the cup portion corresponding to the concave portion and melting the cup portion.

[Problems to be Solved by the Invention] However, none of the above solutions has been a complete solution to the problem. That is, JP-A-59-10
The method described in JP-A No. 8233 still does not provide a sufficiently strong fixation, and the method described in JP-A-59-111222 has difficulty in machining porous sintered bodies; However, when the upper part of the cup is melted to form the protrusion, there is also the problem that part of the electron-emitting material impregnated into the porous body decomposes at the same time.

An object of the present invention is to solve the above-mentioned problems of the prior art and to provide an impregnated cathode that can firmly fix a porous sintered body or a cathode substrate and a cup in a simple manner, and a method for manufacturing the same. Our goal is to provide the following.

[Means for Solving the Problems] The above object is to provide at least a porous sintered body of a high melting point metal or a cathode substrate in which the sintered body is molten and impregnated with an electron emitting substance, a cup made of a high melting point metal, and a cup made of a high melting point metal. In the production of an impregnated cathode comprising a sleeve, the porous sintered body or cathode substrate is press-shaped into a truncated cone (truncated cone) with the top surface smaller than the bottom surface, and then sintered. This can be achieved by manufacturing the cup by inserting it into the cup made of high-melting point metal, applying external mechanical pressure locally to the upper side of the cup, and caulking and fixing the cup.

[Function] By making the impregnated cathode into a cathode having the above structure, the cathode base is mechanically fixed to the cup, and furthermore, the cathode base is geometrically detached upward from the cup. Because of this unique structure, it is possible to firmly fix the cathode substrate and the cup without causing decomposition of the electron-emitting material melted and impregnated during manufacture.

[Example] The impregnated cathode of the present invention and the method for manufacturing the same will be explained in detail below using Examples.

FIG. 1 is a front cross-sectional view of a truncated conical W porous sintered body 1 according to the present invention, and the sintered body 1 is made of W powder, and the outer diameter of the top surface is approximately % smaller than the outer diameter of the bottom surface. It was created by press shaping into a truncated conical shape and sintering in a reducing atmosphere.

An impregnated cathode using this sintered body 1 was formed as follows. That is, first, BaO is added to the sintered body 1.
After melting and impregnating an electron-emitting substance consisting of :CaO:AI, O, and 4:l:l and removing the excess electron-emitting substance remaining on the surface to form a cathode substrate, the second front cross-sectional view shows As shown, the cathode substrate 2 is placed in a Mo cup 3.
Then, at the upper part of the outer surface of the cup 3, caulking was performed at the same time using a three-point needle-like caulking jig 4 at an equal angle of 120°, and the finished product was obtained by fixing. In this case, as shown in FIGS. 2 and 3 (horizontal sectional view taken along line X-X in FIG. 2), the pressing force is adjusted so that the cup inner wall protrusion 5 comes into contact with the cathode base 2. Caulking pressure was applied.

The adhesion strength (pulling strength) between the cup 3 and the cathode base 2 of the impregnated cathode formed in this way is twice as high as that of the conventional cathode in which a cylindrical cathode base is press-fitted into the cup. (approximately L8 kg) or more was obtained. Further, as a result of performing a forced heat run test with the second impregnated cathode mounted in an electron tube, it was confirmed that the cathode base 2 did not deform or fall off.

In the above example, a case was explained in which a cathode base made of a W porous sintered body melted and impregnated with an electron-emitting substance was inserted into a cup, and then caulked. However, exactly the same results were obtained with an impregnated cathode in which an electron-emitting material was melted and impregnated after caulking.

[Effects of the Invention] As described above, by providing the impregnated cathode having the structure of the present invention and the method for manufacturing the same, the problems of the prior art can be solved and the porous sintered body or cathode substrate can be It was possible to provide an impregnated cathode that can be firmly fixed to a cup using a simple method, and a method for manufacturing the same.

[Brief explanation of the drawing]

FIG. 1 is a front cross-sectional view of a frusto-conical W porous sintered body according to the present invention, FIG. 2 is a front cross-sectional view of an impregnated cathode according to the present invention, and FIG. FIG. ■...Fruncto-conical W porous sintered body, 2...Cathode base, 3...Cup, 4...
・3-point needle-shaped caulking jig, 5...cup inner wall protrusion.

Claims (1)

[Claims] 1. A cathode substrate comprising at least a porous sintered body of a high melting point metal or a cathode substrate made of a porous sintered body made of a high melting point metal and melted and impregnated with an electron emitting substance, a cup made of a high melting point metal, and a sleeve made of a high melting point metal. In the impregnated cathode, the porous sintered body or the cathode base is made of a truncated cone with a top surface smaller than the bottom surface, and the porous sintered body or the cathode base is fixed at the upper part of the side surface of the cup. An impregnated cathode characterized by: 2. An impregnated cathode comprising at least a porous sintered body of a high melting point metal or a cathode substrate in which the sintered body is melted and impregnated with an electron emitting substance, a cup made of a high melting point metal, and a sleeve made of a high melting point metal. In manufacturing, the porous sintered body or cathode substrate is press-shaped into a truncated conical shape with a top surface smaller than the bottom surface, sintered, and then inserted into the high melting point metal cup. A method for manufacturing an impregnated cathode, characterized by fixing the cup by caulking the upper side of the cup.