JPS58176845A - Production method of electron tube cathode heater - Google Patents

Abstract

PURPOSE:To obtain a cathode with a low heater operating temperature by forming the first film of aluminum oxide and the second film of metallic powder selected from molybdenum and aluminum powder around a core wire and by burning them in the non-oxidation, oxidation, and non-oxidation atmospheres in sequence. CONSTITUTION:A suspension with aluminum oxide powder dispersed in an organic solvent is coated on a core wire 20 to form an aluminum oxide film layer 21 and it is fully dried. Next, tungsten powder and aluminum oxide powder are suspended and mixed in an organic solvent, which is then coated on the layer 21 and dried to form a film 22 uniformly. A cathode heater 23 with the film 22 fully dried is burnt for about 5min at 1,700 deg.C in the non-oxidation atmosphere. Next, the heater 23 is burnt for about 5min at 700 deg.C in the atmosphere. The heater 23 is further burnt in the non-oxidation atmosphere again. Accordingly, the degree of blackening of the film 22 is improved, and in addition, the tungsten powder is refined. Thereby, a cathode with a highly efficient thermal radiation coefficient and a low heater operating temperature can be obtained.

Description

TECHNICAL FIELD OF THE INVENTION The present invention relates to a method of manufacturing an electron tube cathode heater, and more particularly to a method of manufacturing a black heater used for an indirectly heated cathode.

Technical background of the invention and its problems Hereinafter, the indirectly heated wrinkled cathode of an electron tube will be explained with reference to FIG. 131. T is attached to one end 11i1 of the cylindrical cathode sleeve (1).
An s-pole base metal (2) is fixed, and an electron emitting material (3) is applied on top of it. This cathode sleeve (1)C
) inside (a Ni heater (4) is inserted and fixed. This heater (4) is made of, for example, a core wire made of tungsten (
401) Aluminum oxide powder is coated on top 42 for the purpose of electrical insulation. By heating the heater (4), the cathode sleeve (1) is heated by radiation from the surface of the heater (4), and at the same time the cathode base metal is heated. ) emits thermoelectrons. At this time, the heating efficiency of indirect heating type Kuma & ■ and the core i
In order to achieve the purpose of increasing the lifespan of the heater (4) by lowering the temperature of the heater (401), the heat generated by the heater (4) (2) must be efficiently transferred to the cathode sleeve (1) and the cathode base metal (3). As a means of achieving this objective, it is necessary to improve the heat conduction in vacuum between the negative electrode sleeve (1) and the heater (4), that is, the negative electrode sleeve (
It is said that it is good to improve the thermal emissivity of 1) etc. However, in this case, there was a problem in that the aluminum oxide skin of the heater (4) appeared white and the heat radiation rate was poor. In order to solve this problem, for example,
X report (second is the surface of the aluminum oxide layer of the heater (4)
An indirectly heated cathode heater coated with a material having high bithermal emissivity, namely powdered metal tungsten, mixed with aluminum oxide is disclosed.

However, as a recent trend, there is a demand for indirectly heated cathodes (5) that are smaller and consume less power.
As the Nihita (4) becomes smaller, the core (401) material itself tends to become thinner. For this reason, the above-mentioned special public service
When the indirectly heated cathode heater disclosed in Japanese Patent No. 3864 is thinned, the heater (4) becomes brittle at the conventional heater temperature.
and aluminum oxide as an insulating material and core wire (401
) Due to the stress generated between C2 and C2, there is a problem that the disconnection of the Ni heater (4) is noticeable (2).

Purpose of the Invention The present invention has been made in view of the above points, and an object of the present invention is to provide a method for manufacturing an electron tube cathode heater that eliminates the above-mentioned drawbacks, has a highly efficient thermal emissivity, has a low heater operating temperature, and has a long life. purpose.

Summary of the Invention In the present invention, an aluminum oxide coating is formed on a core wire, and on the coating, at least one metal powder selected from tungsten and molybdenum and aluminum oxide powder are formed as a second coating. The core wire on which this film has been formed is fired in a non-oxidizing atmosphere, then fired in a dioxide atmosphere to oxidize the metal powder of the 20th film. This is an electron tube cathode heater that effectively improves thermal emissivity and lowers the heater operating temperature by forming the metal powder in the second coating layer into finer particles, thereby increasing the lifespan of the electron tube cathode heater.

Examples of the invention Hereinafter, one embodiment of the present invention will be described with reference to FIG.

The electron tube implicit system applied to the present invention has the same structure as that shown in FIG. A suspension of aluminum oxide powder dispersed in four organic agents is applied by spraying or coating (secondly, it is applied to the core wire to form an aluminum oxide coating layer and thoroughly dried. Next, tungsten powder and Aluminum oxide powder is suspended and mixed in a suitable dispersion medium, such as an organic solvent, and this suspension is applied by means such as spraying or coating. , to form a uniform film. After drying this film to the base metal, an electron tube heater (hereinafter referred to as the heater) (c) is fired in a non-fermenting atmosphere. In this example, , and fired in a hydrogen atmosphere.What kind of metal powder is used other than the aluminum oxide powder mixed in the coating? It is sufficient to perform firing at substantially (=1700'O) for 5 minutes.Aluminum oxide layer (!υ) is layered well on the core yeast, and then the coating Q-shi and the aluminum oxide-coated J-shi υ
and effectively combine 42.

Aluminum dioxide coating JfIG! In the first step of forming υ, whether or not firing is performed to form a fermented aluminum coating layer, after forming the coating layer, the second step of baking in a hydrogen atmosphere ( From the second point, its role is to play the role of light (2).
is fired in an oxidizing atmosphere, for example in the air, to oxidize the tungsten powder mixed with the coating C2. In the case of this step, if the firing temperature is too high, the tungsten powder, which is an additional material of the coating (2), will penetrate into the aluminum oxide coating layer Cυ (second) and reduce the insulation ability of the heater (c). , the firing conditions for this step are coating +2
When tungsten powder was used as the additional material in step 3, it was effective to sinter it for 5 minutes at 600-700°C.Furthermore, sinter the heater (c) again in a non-oxidizing atmosphere. In this example, it was confirmed that the tungsten powder of T&V3 to be subjected to reduction treatment in an aqueous atmosphere could be made into fine particles to form a wide surface area of the coating +23.

FIG. 3 shows the relationship between the black heater temperature and the heater input voltage for the heater apricot of this embodiment and the conventional black heater. Condolence 3
Figure (According to Yu, the temperature characteristics of the heater and the song f of this example
i (31b) is the song of the conventional black heater ii characteristic, d
(31a) It is clear that the temperature of the heater operating as an electron tube cathode is low even if the same heater input pressure is applied to all the heaters. This clearly shows that the heater of this embodiment operates at a lower temperature than the conventional black heater. The degree of blackening of the coating I24 containing tungsten powder is improved, and furthermore, the tungsten powder has a large thermal radiation area to form fine particles (=
There are two encircles.

Further, in this example, an example is shown in which tungsten powder is used as an additional material for the coating, but the same effect as in the above example can be obtained by using molybdenum or a mixture thereof.

Effects of the Invention (As described above) According to the present invention, the heat radiation rate from the heater can be improved without deteriorating the insulation properties of the aluminum oxide insulating layer, and the operating temperature of the heater is lowered, resulting in a long life and high performance. A high quality magnetron tube cathode heater can be obtained.

[Brief explanation of the drawing]

FIG. 1 is a sectional view showing the schematic structure of the indirectly heated cathode of the electron tube.
FIG. 2 is a sectional view showing a schematic configuration of an electron tube cathode heater according to the present invention, and FIG. 3 is a characteristic diagram showing the relationship between input voltage and heater temperature. (4)...Heater (to), (401)
... Core wire υ ... Aluminum oxide coating J-

Claims (1)

[Claims] a step of applying a coating solution containing core wire aluminum dioxide powder; A step of applying a liquid to form a core Miζ film, a step of firing the film in a non-oxidizing atmosphere, a step of firing the fired film in an oxidizing atmosphere, and a step of firing the film in an oxidizing atmosphere. A method for manufacturing an electron tube cathode heater, comprising the step of removing the film and firing it in a non-oxidizing atmosphere.