JPH0139615B2 - - Google Patents

Description

[Detailed Description of the Invention] [Object of the Invention] (Industrial Field of Application) The present invention relates to a cathode assembly for an electron tube, and particularly to a cathode assembly for an ultra-fast-acting electron tube suitable for use in an electron gun of a color picture tube. It is related to.

[Technical background of the invention and its problems]

An example of a conventional cathode structure for an ultra-fast-acting electron tube is explained with reference to FIGS. 1 and 2. The plate thickness is approximately 40 μm.
The heaters 2, 2 are installed inside the cathode cylinder 1 mainly made of nickel with a diameter of less than m, and an electron emissive oxide layer 3 is attached to the top surface. The heaters 2, 2 are composed of a filament 4 made of a coiled tungsten wire with a wire diameter of 20 to 30 μm, and a sintered alumina insulating layer 5 that hardens the filament 4 from both the inside and outside. 1 and is almost completely surrounded by the cylinder. Such a cathode cylinder 1 is initially formed into a cylindrical shape with a rectangular cross section as shown by the reference numeral 11 in FIG.
The internal space is designed to have a size that will still leave a considerable gap even after the heaters 2, 2 are inserted. In the compression process, by moving the shaping tables 6, 6 in the direction of the arrow in FIG.
It is formed by processing so as to have the above-mentioned relationship between them.

Such a cathode structure for an electron tube has an overlapping part formed in a part of the cathode cylinder by compression processing applied to the cathode cylinder, and the other part is in close contact with the outer peripheral surface of the heater.
Since the entire cathode cylinder is deformed around this heater, the degree of mechanical and thermal coupling between the heater and the cathode cylinder is extremely high.
It is said that it not only eliminates various problems caused by relative positional deviations between the tubes, but also improves the heating effect, and is particularly effective as a thermionic emission source for small cathode ray tubes. However, on the other hand, it has the following fatal drawbacks as a cathode structure for an electron tube.

(1) Since the cathode structure is supported only by the end of the filament, considering the thermal deformation characteristics of the filament, the electric distance (G ₁ −K distance) between the electron-emitting oxide layer and the grid electrode placed opposite it is is not constant, and therefore the cut-off voltage of the grid electrode varies, resulting in poor white balance in color picture tubes.

(2) When heating the heater, the difference in thermal expansion between the filament, the alumina coating material, and the nickel-based cathode barrel may cause the filament to break or the coating material to peel off, resulting in accidents between the heater and the cathode barrel. Easy to occur.

(3) Since the heater is inserted into the cathode cylinder with a rectangular cross section and the cathode cylinder is brought into close contact with the outer circumferential surface of the insulating layer of the heater by compression processing, manufacturing of this cathode cylinder takes into account the brittleness of the filament and alumina. It is extremely difficult considering this.

(4) The most serious drawback is that W+Al ₂ O ₃ →W _n O _o +Al (however, m,
(n is a positive integer) reaction occurs, and the oxygen in this W _n O _o diffuses through the grain boundaries of the cathode cylinder of 40 μm or less, which is mainly made of nickel, and forms the oxide layer on the cathode cylinder. A so-called gas dove phenomenon occurs that changes the composition, significantly shortening the life of the cathode.

[Purpose of the invention]

The present invention is an ultra-fast acting type developed in view of the various drawbacks of the conventional ones mentioned above, which does not change the G ₁ -K interval, is easy to manufacture, and has a long life and high reliability for electron tubes. The purpose is to provide a cathode structure.

[Summary of the invention]

The present invention has two cathode sleeves fixed directly or through a connecting piece, and the two cathode sleeves are fixed by welding the peripheral edges of the two cathode sleeves to approximately the center in the length direction. A base metal having an electron-emitting oxide layer fixed therebetween with a space formed therebetween, and a heater provided in the two cathode sleeves that heats the base metal by thermal conduction and radiant heat. This is a cathode structure for an electron tube characterized by the following.

[Embodiments of the invention]

Next, a first embodiment of the cathode assembly for an electron tube according to the present invention will be described with reference to FIGS. 3 to 5. Figure 3 shows three sets of cathode assemblies for electron tubes arranged side by side on one insulating substrate for use in color picture tubes, and Figures 4 and 5 respectively show the three sets of cathode assemblies for electron tubes. FIG. 2 is a plan view and a front view showing essential parts of one cathode assembly for an electron tube. In this embodiment, two cathode sleeves 26, 26 are used as heat transfer metal bodies.
is used.

That is, the cathode structure for an electron tube of this embodiment includes supports 23, 23 for supporting conductors 22, 22 for filaments and the cathode structure, which are implanted through an insulating substrate 21 made of ceramics, etc.
3 and 23 through support pieces 24 and 24, and the electron gun axis Z
The cross-sectional shape obtained by welding the contact points at two points 25 and 25 is approximately circular, and the inner and outer surfaces are blackened, for example, in thickness.
Two cathode sleeves 26, 26 made of a nickel-chromium-tungsten alloy with a diameter of 15 μm, a diameter of 1.3 mm, and a length of 3 mm are placed along the envelope top surfaces of these cathode sleeves 26, 26, centered on the electron gun axis. A base metal 28 mainly made of nickel and having a thickness of 0.05 mm and a diameter of 1.5 mm is fixed to each cathode sleeve 26, 26 at welding points 27, 27, and Alumina 31 is sintered on the inside and outside of the oxide layer 29 that emits thermoelectrons and the filament 30 wound into a coil, and is inserted through the openings in the same direction of the cathode sleeves 26 and 26, respectively. The heater 36 is formed into a possible U-shape, and the heater 36 is connected to the conductors 22, 22 at welding points 32, 32 near both ends, respectively. Therefore, in this cathode structure, there is a space 3 between the cathode sleeves 26, 26 and the base metal 28.
4 is formed.

Next, the main points of the method for manufacturing such a cathode assembly for an electron tube will be explained with reference to FIGS. 6 to 12.

First, as shown in Figure 6, the thickness is 15 μm and the diameter is 1.3
Two nickel-chromium-tungsten cathode sleeves 26, 26 with a length of 3 mm and a length of 3 mm are arranged in parallel.
The contact portions are fixed at welding points 25, 25. Next, as shown in FIG. 7, the thickness is adjusted between the top surfaces of the two cathode sleeves 26, 26 at approximately the center in the longitudinal direction, that is, along the envelope top surface, with the electron gun axis Z at the center. The vicinity of the periphery of a disc-shaped base metal 28 mainly made of nickel with a diameter of 0.05 mm and a diameter of 1.5 mm is welded and fixed at welding points 27, 27. Next, as shown in FIG. 8, the two cathode sleeves 26, 26 are made of amber alloy with a thickness of 0.05 mm and a width of 0.5 mm, axially symmetrical with respect to the electron gun axis Z, on the outside of both ends in the longitudinal direction. A pair of supporting pieces 24, 24 are welded at a welding point 24 ₁ ,
24 Fix at ₁ .

Next, such a semi-finished product is subjected to a blackening treatment on the inner and outer surfaces of the cathode sleeves 26, 26 in a wet hydrogen furnace, and then the supporting pieces 24, 24 are formed into an L-shape as shown in FIG. , Ba, Sr, which is then formed into an oxide layer 29 on the base metal 28 in an aging process
Apply Ca carbonate. Next, as shown in FIG. 10, among a pair of supports 23, 23 and conductors 22, 22, which are implanted in advance through an insulating base 21 such as ceramics, a support piece 24, 24 are welded and fixed at welding points 23 ₁ , 23 ₁ so that the cathode sleeves 26 , 26 and the base metal 28 are perpendicular to the electron gun axis Z. Next, in a separate step, as shown in FIG. 11, the filament 30 wound into a coil is bent into a U-shape, coated with alumina, and sintered to form a heater 36 as shown in FIG. The conductor 22 is inserted into the cathode sleeves 26, 26 in the direction of the arrow, and is implanted through the exposed portion of the filament 30 near both ends into the insulating substrate 21.
22 at welding points 32, 32 to complete the electron tube cathode assembly.

Next, a second embodiment of the present invention will be described with reference to FIG. In the drawings, the same parts as in the first embodiment are designated by the same reference numerals and will not be particularly described.

In this embodiment, two cathode sleeves 26,
Connecting pieces 37, 37 without directly welding 26
..., and the cathode sleeves 26, 26 are connected by welding connecting pieces 37, 37 to the top and/or bottom surfaces at welding points 38, 38, with the cathode sleeves 26, 26 separated by a desired distance. Therefore, in the cathode assembly of this example, the base metal 28 has fixing pieces 28 ₁ protruding from both sides, for example, as shown in the drawings, and these fixing pieces 28 ₁ are fixed to the top surfaces of the cathode sleeves 26 , 26 . By adopting such a structure, it is possible to reduce the deformation of the cathode sleeves 26, 26, and it is possible to further reduce the diffusion of impurities such as molybdenum, tungsten, oxygen, and copper into the center of the base metal 28. I can do it.

Next, a third embodiment of the present invention will be described with reference to FIG. 14. In the drawings, the same reference numerals as in the first embodiment indicate the same parts, and no particular explanation will be given.

In this embodiment, the support pieces 24, 24 are provided at an acute angle with respect to the cathode sleeves 26, 26, which makes it possible to improve rotation during cathode operation. .

Next, a filament adapted to another embodiment of the present invention will be explained with reference to FIG. That is, the pitch of the coiled filament 30 corresponding to the base metal 28 placed along the envelope top surface of the cathode sleeve 26 so as to be approximately centered on the electron gun axis is made into a variable pitch that is more tightly wound than other parts. The temperature of the cathode sleeve in this part is raised more rapidly than in other parts to improve speed.

The above-mentioned embodiments are typical examples of the present invention. In addition, the cross-sectional shape of the cathode sleeve may be changed, only the outer surface may be blackened, or may not be blackened, or the shape of the base metal may be changed to a circular shape instead of a circular one. It may be a non-circular shape such as a circle or a square, or the substrate may be a metal plate instead of an insulator, and a support or conductor may be provided at the eyelet via an insulator, or a U-shaped heater may be used instead of a U-shaped heater. Needless to say, a linear heater may be inserted into each of the cathodes, or the cathode may be shaped so that it can be inserted into a support cylinder of a conventional indirectly heated cathode.

〔Effect of the invention〕

Next, the characteristics of the electron tube cathode assembly completed in this manner will be described.

(1) The base metal is a fast-acting type because it is rapidly heated by heat conduction and heat radiation from the cathode sleeve, which is a heat transfer metal body. That is, in this embodiment, the base metal is placed approximately at the longitudinal center of the cathode sleeve, that is, centered on the electron gun axis, and the base metal is located approximately at the center of the heater.

Therefore, in this case, when we examine the temperature rise process of the heater when a voltage is applied to the heater, we find that the temperature rises from the center in the length direction of the heater, and as a result of the experiment, an image output characteristic of 1.5 seconds is obtained. was completed.

The reason why the temperature at the center of the cathode sleeve is the highest is because firstly, the heat dissipated from the heater is transmitted to the cathode sleeve and then escapes from the cathode sleeve to the support pieces welded to the outside of both ends. This is because both ends of the cathode sleeve are open, so the heat from the heater escapes from both ends of the cathode sleeve, resulting in lower temperatures at both ends than at the center.

(2) Structure where the heater and base metal are non-contact (space part 3)
4), and the debris from the heater adheres to the cathode sleeve but not to the base metal. Therefore, impurities do not diffuse into the base metal, and there is no deterioration in emission of thermoelectrons from the oxide layer deposited on the base metal.

(3) The cathode sleeve is made of metal containing chromium, tungsten, etc., and if oxygen, etc. generated by the reaction between chromium, tungsten, or tungsten and alumina diffuses into the base metal, it will cause emission deterioration. In this example, it is fixed to the cathode sleeve at two points near the periphery, and a space is formed in the center, creating a non-contact structure, so that the diffusion of chromium, tungsten, oxygen, etc. can be almost ignored. It can be done. Even if they spread,
In the case of an electron gun for an electron tube, the hole diameter of the opposing grid electrode is smaller than the diameter of the electron emitting part of the cathode, and the structure is such that electron emission is performed only from the central part, so this poses little problem. In other words, in the case of this embodiment, the diffusion of impurities is extremely small, which is advantageous in terms of emission, and the life span is also extended.

(4) Since the base metal and the cathode sleeve are fixed near the periphery of the base metal, even if welding electrode material, such as copper, is attached, it is only near the periphery.

(5) The manufacturing method is very simple, as there is no need to insert the heater and then perform compression processing as in the conventional case, and there is no need to compress the heater, so there is no need to break the filament in the heater. , the chances of contact between the filament and the cathode sleeve are extremely small, and the reliability of the cathode structure is high.

(6) Since the support structure is axially symmetrical with respect to the electron gun axis, the structure is such that thermal deformation of each component can be avoided by rotation, and dimensional changes (for example, G ₁ -K distance changes) during the life are small.

[Brief explanation of drawings]

1 and 2 are diagrams showing an example of a conventional cathode assembly for an electron tube, in which FIG. 1 is a perspective view, FIG. 2 is an explanatory diagram showing an intermediate process, and FIGS. 3 to 5 are views of the present invention. FIG. 3 is a perspective view, FIG. 4 is an enlarged plan view of the main part, FIG. 5 is an enlarged side view of the main part, and FIGS. 6 to 12 are views showing the first embodiment. 13 is a plan view showing the second embodiment of the present invention; FIG. 14 is a plan view showing the third embodiment of the present invention; FIG. The figure is a simplified illustration of a filament adapted to another embodiment of the invention. 2, 31... filament, 3, 29... oxide layer, 21... insulating substrate, 22... conductor, 23
... Support body, 24 ... Support piece, 26 ... Cathode sleeve, 38 ... Base metal, 34 ... Space part, 36
……heater.

Claims (1)

[Scope of Claims] 1. Two cathode sleeves fixed directly or through a connecting piece, and a peripheral edge of the two cathode sleeves being welded to approximately the center in the longitudinal direction of the two cathode sleeves. a base metal having an electron emissive oxide layer fixed with a space formed between the two cathode sleeves; and a heater provided in the two cathode sleeves that heats the base metal by thermal conduction and radiant heat. A cathode structure for an electron tube, comprising: 2. The cathode assembly for an electron tube according to claim 1, wherein the base metal is welded and held at a position where the temperature distribution of the two cathode sleeves caused by heat generation from the heater is relatively high. . 3. The cathode assembly for an electron tube according to claim 1, wherein the inner and outer surfaces of the cathode sleeve are blackened. 4. The heater according to claim 1, characterized in that the heater is made of a variable pitch coiled filament that is a combination of tightly wound and loosely wound filaments, and the portion near the portion corresponding to the base metal is tightly wound. Cathode structure for electron tube.