JPH01154425A - Potted-type cathode - Google Patents

Abstract

PURPOSE:To reduce the thermal capacity of a whole cathode and to improve the rapid operation property by providing a potting material only between the cathode and heaters. CONSTITUTION:To reduce the thermal capacity of a cathode 6 including heater parts, a potting material 4 is furnished only between heaters 1-3 and the cathode 6. As the potting material 4, the sinter of a metal powder with a high thermal conductive coefficient is used. And to suppress a crack owing to the heat cycle, coarse particles of alumina is used on the surface of the cathode 6 or a cathode holding tube 5 facing the heaters. In such a composition, the heat from the heaters can be transmitted in a large quantity, and, since the thermal capacity of the cathode 6 part including the heaters can be reduced, the cathode 6 including the heaters can be heated rapidly up to the operational temperature.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a pottet-shaped cathode used in an electron tube.

[Conventional technology]

Conventionally, as a cathode for an electron tube, a heater is placed near the cathode, and the cathode is heated by radiant heat from the heater.The heater is an indirectly heated cathode, and the entire heater is buried in alumina powder and bonded to the cathode, so that the conduction heat from the heater is absorbed. There is a pottet-shaped cathode that heats the cathode.

[Problem that the invention seeks to solve]

In the above-mentioned conventional indirectly heated cathode that heats the cathode using radiant heat, the beater is heated to a temperature 400 to 500 degrees Celsius higher than the temperature at which the cathode must be heated, that is, the cathode operating temperature, due to the heat transfer between the cathode and the heater. Must.

Generally, tungsten, which is a low vapor pressure, high melting point metal, is used for heaters. However, due to the nature of tungsten,
It cannot be heated above 600°C. Therefore, indirect heating type heaters have the disadvantage that even at the time of starting, it is difficult to input more power than during steady operation, and the interlocking performance is lacking.

On the other hand, in pottery type poles in which the heater is embedded and bonded to the cathode using alumina powder, the difference between the heater operating temperature and the cathode operating temperature is 100 to 200°C, so it is necessary to input more power than during normal operation at startup. is possible. However, the cathode constituent metal and the potting material alumina (Ae)
The difference in the coefficient of thermal expansion of z 03 ) was large, and cracks were likely to occur at the joint surface with the cathode when heat cycles were applied. Furthermore, alumina has low thermal conductivity, and since the entire heater is buried, the heat capacity becomes large, so that it has not been able to exhibit sufficient performance as a fast-acting cathode.

[Means for solving problems]

The potted cathode of the present invention is characterized by having a potting material only between the heater and the cathode in order to reduce the heat capacity of the cathode including the heater portion. A metal powder sintered body with a high heat transfer coefficient is used as the potting material. Also,
In order to suppress cracks caused by heat cycles, the surface of the cathode or cathode support tube facing the heater has irregularities ranging from several microns to several tens of microns, and the surface of the heater insulating layer has coarse-grained alumina. .

〔Example〕

Next, the present invention will be explained with reference to the drawings.

FIG. 1 is a longitudinal sectional view of a first embodiment of the invention. 1 is a heater coil made of tungsten or 3% rhenium.
It is made of high melting point metal such as tungsten alloy. 2 and 3 are alumina insulating layers, and 2 is composed of alumina powder of 2000 mesh or less, and 3 is composed of alumina powder of 900 mesh or more. These are deposited by electrophoresis or spraying, with a concentration of 1600 to 1 in a hydrogen atmosphere.
Heat to 700°C and sinter. 4 is a potting material, which is a sintered body made by mixing tungsten powder with an average particle size of 10 microns to several tens of microns and nickel powder with an average particle size of 1 micron to several microns in a ratio of 20:1. These are 11
It is sintered in a hydrogen atmosphere at 50°C. Note that the powder mixture constituting the sintered body is not limited to the above example as long as it is composed of a large amount of high melting point metal powder and a small amount of low melting point metal powder. Reference numeral 5 denotes a cathode support cylinder made of tungsten, the inner surface of which is plasted with alumina of 150 to 320 mesh, and has an uneven surface of 10 μm on average. 6 is a cathode. In this embodiment, the potting material 4 is provided only between the cathode support cylinder 5 and the heater coil 1, rather than filling the entire space as shown. Therefore, the heat capacity of the entire cathode can be reduced and the interlocking performance is excellent.

FIG. 2 is a longitudinal sectional view of a second embodiment of the invention. 11
1 is a heater coil, and 12 is an alumina insulating layer. 12 is composed of two alumina layers having different particle sizes as in the first embodiment. 13 is a potting material made by mixing molybdenum powder with an average particle size of 10 microns to several tens of microns and nickel powder of 1 micron to several microns in a ratio of 10:1.
This is a sintered body sintered in a hydrogen atmosphere at 0°C. 14 is a cathode. In this embodiment as well, the potting material 13 is provided only between the heater coil 11 and the cathode 14, so the heat capacity is small.

〔Effect of the invention〕

As explained above, the present invention has the potting material of the metal powder sintered body only between the cathode and the heater.
Since a large amount of heat from the heater can be transmitted quickly and the heat capacity of the cathode portion including the heater can be reduced, there is an effect that the cathode can be quickly heated to the operating temperature. In addition, metal powder has a small difference in coefficient of thermal expansion from the cathode or cathode support, and the alumina insulating layer of the heater and the surface of the cathode or cathode support tube facing the heater have appropriate unevenness, so the metal powder sintered body It is effective in preventing cracks from occurring due to heat cycles.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of a first embodiment of the invention, and FIG. 2 is a sectional view of a second embodiment of the invention. 1.11... Heater coil, 2, 3.12... Alumina insulation layer, 4.13... Potting material, 5...
Cathode support cylinder, 6.14... cathode.

Claims (4)

[Claims] (1) A pottet-shaped cathode in which a heater is disposed within the cathode and the heater is embedded with a potting material, and the pottet-shaped cathode is characterized in that the potting material is provided only between the cathode and the heater. (2) A potted cathode according to claim (1), wherein the potting material is a metal powder. (3) The potted cathode according to claim (1), wherein the surface of the cathode or the cathode support cylinder facing the heater has irregularities ranging from several microns to several tens of microns. (4) The pottery cathode according to claim (1), which has an alumina insulating layer of fine particles on the outer periphery of the heater coil and an alumina insulating layer of coarse particles around the outer periphery of the heater coil.