JPH0125406Y2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a cathode assembly for an electron tube, and more particularly to a cathode assembly for an electron tube of an ultra-fast motion type suitable for use in an electron gun of a color picture tube.

An example of a conventional cathode structure for an ultra-fast-acting electron tube will be explained with reference to FIGS. A sintered alumina insulating layer 4 is deposited over almost the entire area except for both end lines 2 and 3, forming a heating body 5. This heating body 5 is a flat cathode tube 6 with a rectangular cross section.
An electron emitting oxide layer 7 is attached to the upper surface of the cathode tube 6. Further, a metal wire 8 for supporting the cathode is attached to the lower surface. As this metal wire 8, in order to support the cathode almost exclusively by this metal wire, a heat-resistant material such as tungsten having a wire diameter 2.0 times or more of the tungsten wire diameter of the coil heater 1 is used. It is disposed in a direction perpendicular to the axis of the gun, and one end is welded to the stem lead wire 9. The other end is a free end, and the cathode cylinder 6
is welded to the bottom surface of the The coil heater 1 is connected to the stem lead wire 1 through bent wires 2 and 3 at both ends.
0 and 11, and these end lines 2 and 3 have a structure in which almost no load from the cathode is applied.

In such an electron tube cathode structure, the cathode receives almost no supporting action from the heater and is supported only by the metal wire, which is disposed perpendicular to the electron gun axis. In addition, since the side to which the cathode is fixed is a free end, even if this elongation occurs due to heating, the cathode will only be displaced within a plane perpendicular to the electron gun axis, and the cathode and control grid will be There is no change in the gap between
Moreover, stress is not applied to each welding point due to elongation, and it is said that a cathode ray tube with stable characteristics can be obtained at low cost.

However, the cathode assembly for an electron tube having such a structure has the following drawbacks.

(1) Since the cathode is placed and fixed on the free end of a metal wire, considering the thermal deformation characteristics and mechanical properties of this metal wire, the oxide layer and the grid electrode opposite it The gap (G-K gap) is difficult to be constant, and therefore the cut-off voltage of the grid electrode fluctuates, resulting in poor white balance in a color picture tube.

(2) W+ between the coiled tungsten filament that forms the heater and the alumina.
Al ₂ O ₃ →WmOn+Al (where m and n are positive integers)
This reaction occurs, and the so-called gas doping phenomenon occurs in which the oxygen (O) in WmOn diffuses through the grain boundaries of the extremely thin nickel-based material that forms the cathode tube, changing the composition of the upper oxide layer. occurs, extremely shortening its life as a cathode.

(3) Others The present invention was developed in view of the various drawbacks of the conventional technology mentioned above.It is a super-fast moving type, does not change the G-K gap, is easy to manufacture, and has a long life and high reliability. The object of the present invention is to provide a cathode structure for an electron tube.

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 14. Figure 3 shows three sets of cathode structures for electron tubes arranged side by side on a single insulating substrate for use in color picture tubes, and Figures 4 and 5 each show one of the cathode structures in Figure 3.
FIG. 2 is a plan view and a front view showing essential parts of a cathode assembly for an electron tube.

That is, the cathode structure for an electron tube includes a pair of conductors 22, 22 for filaments, which are implanted through an insulating substrate 21 made of ceramics, a pair of supports 23, 23, which support the cathode structure, and the supports. A cathode sleeve 25 having a substantially circular cross-sectional shape, which lies on a plane substantially perpendicular to the electron gun axis Z, is attached to the cathode sleeve 25 through support pieces 24 and 23, and the cathode sleeve 25 has a cathode sleeve 25 which is perpendicular to the electron gun axis Z. Rectangular plane part 2
After _press punching, the base metal plate 26 is placed and fixed approximately in the center of the metal plate 26, with the circular center part ₂₆₁ as the top separated from the cathode sleeve 25, and having a raised part ₂₆₂ and a fixing part ₂₆₃ on both sides. After fixing the fixed part 26 ₃ and the flat part 25 ₁ of the base metal plate 26 by welding or the like, an electron emitting oxide layer 27 and a cathode sleeve 2 are deposited on the central part 26 ₁ .
It is wound into a coil shape that can be inserted from one end of 5,
Furthermore, alumina 29 is sintered on the inside and outside of a filament 28 wound in a helical shape, and the heater 31 is connected near both ends to conductors 22, 22 through welding points 30, 30, respectively. .

Next, a method of manufacturing such a cathode assembly for an electron tube will be explained with reference to FIGS. 8 to 13.

First, as shown in FIG. 8, a cylindrical cathode sleeve 25 with a diameter of about 3 mm and made of a nickel-chromium-tungsten alloy with a thickness of 15 μm is formed, and a rectangular and substantially planar portion 25 is formed in the axial direction of the cathode sleeve 25.
form ₁ . Next, as shown in FIG.
As shown in FIGS. ₆ and 7, a rising portion 26 ₂ and a fixed portion 26 ₃ are formed approximately in the center of the circular central portion 26 ₁ from a member mainly made of nickel with a thickness of approximately 0.04 mm. Place the formed base metal plate 26,
The fixing part 26 ₃ is fixed to the flat part 25 ₁ , and the center of the central part 26 _{1 is located near the open end edge of the outer wall of the cathode sleeve 25, which is substantially perpendicular to the flat part 25 1 .}
That is, the thickness is 0.05 mm and the width is axially symmetrical with respect to the electron gun axis Z.
A pair of support pieces 24 made of amber alloy of about 0.5 mm,
Weld 24.

Next, such a semi-finished product is heated in a wet hydrogen furnace to blacken the inner and outer surfaces of the cathode sleeve 25, and then the support piece 24 is formed into a substantially L-shape as shown in FIG. , Ba, Sr, which becomes the oxide layer 27 in the aging process on the central part ₂₆₁ .
Apply Ca carbonate. Next, as shown in FIG. 11, among the pair of supports 23, 23 and conductors 22, 22, which have been implanted in advance through an insulating substrate 21 such as ceramics, support pieces 24, 24 are attached to the supports 23, 23. The oxide layer 27 formed on the center portion ₂₆₁ is fixed by welding so that the main surface thereof is perpendicular to the electron gun axis Z. Next, in a separate process, a heater 31 with alumina 29 sintered on the inside and outside of the filament 28 which has been wound into a coil shape as shown in FIG. The exposed part of the filament 28 is connected to the conductor 2
2 and 22 to complete an electron tube cathode structure as shown in FIG.

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

(1) The cathode sleeve is blackened and made of thin material, so it is fast-acting. That is, in the embodiment, since the base metal plate is provided approximately at the center of the flat surface of the cathode sleeve, this base metal plate is located at approximately the center of the heater, that is, the position corresponding to the position where the temperature of the heater increases quickly. As a result of experiments, we were able to obtain an image output characteristic of nearly 1.2 seconds.

The reason why the temperature in 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 escapes from the cathode sleeve to the support piece, and secondly, because both ends of the cathode sleeve are open. This is because the heat from the heater escapes from both ends of the cathode sleeve, lowering the temperature of this part.

(2) The heater and base metal plate have a non-contact structure;
Spattered matter from the heater adheres to the cathode sleeve, but not to the base metal plate. Therefore, impurities do not diffuse into the base metal plate, and there is no emission of thermoelectrons from the oxide layer deposited on the base metal plate, that is, no deterioration of emission.

(3) The cathode sleeve is made of a metal containing chromium, tungsten, etc., and if oxygen, etc. generated by the reaction between chromium, tungsten, tungsten, and alumina diffuses into the base metal plate, it may cause emission deterioration. However, in the case of this embodiment, the center of the base metal plate is separated from the cathode sleeve, and the length of the rising part that determines the distance is usually 0.1 to 0.5 mm, and it is fixed only at the fixed part, preventing electron emission. Since the structure is such that the diffusion is carried out only from this central part, diffusion of impurities into this central part is extremely small, which is advantageous in terms of emission and has a long life. For example, when the length of the rising part was set to 0.3 mm, the lifespan could be increased by about 1.5 times compared to conventional products.

In comparison, in the conventional case, the cathode sleeve is used as the base metal, so impurities often diffuse into the electron emitting material deposited on top of the cathode sleeve, which is disadvantageous in terms of emission and has a short lifespan. .

(4) Since the support structure is provided in a pair axially symmetrically with respect to the electron gun axis, the structure is such that thermal deformation of each component can be avoided by rotation around the electron gun axis;
Dimensional changes during life (mainly G-K gap changes)
There is also little dimensional change due to mechanical impact.

In comparison, the conventional one is cantilever supported by metal wires, is weak against mechanical shock, and is G-K
Parallelism and gap changes between the two are also likely to occur.

(5) Normally, as shown in FIG. 14, the opposing grid electrode 41 has a ring-shaped groove (bead) 41 ₂ that protrudes toward the cathode side so as to surround the hole 41 ₁ . 41 In relation to ₂ ,
Since the rising portion ₂₆₂ is provided, it is possible to prevent the so-called G-K touch between the cathode and the grid electrode.

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

That is, in this embodiment, the cathode sleeve 25 does not have a flat part, but has a recessed part ₂₅₂ in the center in the axial direction.
A base metal plate 56 is formed into a circular or non-circular shape and placed so as to span the recess 25 ₂ , and only the vicinity of the edge of the base metal plate 56 is covered with the cathode sleeve 25 .
It is fixed to the outside wall.

By adopting such a structure, the recess 25 ₂
Since the metal plate 56 is closer to the heater (not shown) and the temperature rises more quickly, the speed of operation can be further improved. By depositing the electron emitting material layer except for the edge portions, it is possible to obtain a cathode structure for an electron tube that is free from diffusion of impurities and has good emission characteristics.

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 28 corresponding to approximately the center in the axial direction of the cathode sleeve 25, that is, the position where the base metal plate 26 is placed, is wound more closely than other parts, that is, it is made into a variable pitch, and the pitch of the cathode sleeve in this part is Raise the temperature more rapidly than others,
It is designed to improve speed. In this case, it goes without saying that the helical shape may be made into a variable pitch.

The above embodiment is a typical example of the present invention, and the cross-sectional shape of the cathode sleeve may be changed, or at least one of the inner and outer surfaces of the cathode sleeve may be blackened, or may not be blackened. For example, the base body 21 is made of a metal plate instead of an insulator, and the supports 23,
23. The conductors 22, 22 may be provided in the eyelets via an insulator, the shape of the heater may be changed to a straight line or other form, or the heater may be shaped into a U-shape that can be inserted into the support tube of a conventional indirectly heated cathode structure. There is no need to explain that it can be done. In addition, instead of providing a flat part or a recessed part in the cathode sleeve, by providing a protrusion at a position corresponding to the vicinity of the edge of the base metal plate, or by fixing the vicinity of the edge without providing anything, Since the center of the base metal plate can be separated from the cathode sleeve to some extent, the emission is better than that of the conventional one. Furthermore, the supporting piece is not limited to an L-shape; it is possible to maintain a uniform G-K gap by making the supporting piece into a shape that can rotate around the electron gun axis when each component thermally expands. Of course.

[Brief explanation of the drawing]

1 and 2 are diagrams showing an example of a conventional cathode assembly for an electron tube, in which FIG. 1 is a plan view, FIG. 2 is a perspective view, and FIGS. Fig. 3 is a perspective view, Fig. 4 is a plan view of the main part, Fig. 5 is a front view of the main part, Fig. 6 is a plan view of the base metal plate after pressing, and Fig. 7 is a diagram showing the embodiment. is a side view of the base metal plate after molding, FIGS. 8 to 13 are explanatory diagrams showing the main parts of an example of the manufacturing process of the first embodiment in order of process, and FIG. 14 is a side view of the base metal plate after forming. An explanatory diagram showing the relationship with the opposing grid electrodes, FIG. 15 is a perspective view for explaining the main part of the second embodiment of the present invention, and FIG. 16 is a simplified filament suitable for another embodiment of the present invention. It is an explanatory diagram. 2, 28... Filament, 5, 31... Heater, 7, 27... Oxide layer, 6, 25... Cathode sleeve, 21... Insulating substrate, 22... Conductor, 2
3... Support body, 24... Support piece, 26, 56...
Base metal plate.

Claims (1)

[Claims for Utility Model Registration] (1) A cylindrical cathode sleeve, a fixed part fixed to the outer wall of the cathode sleeve, a rising part from this fixed part, and a central part formed through this rising part. a base metal plate, the center of which is separated from the outer wall of the cathode sleeve by the rising portion and arranged perpendicularly to the electron gun axis; an oxide layer deposited on the center of the plate; a support piece disposed near an edge of the outer wall of the cathode sleeve axially symmetrically with respect to the electron gun axis; and a support piece inserted into the cathode sleeve. 1. A cathode assembly for an electron tube, comprising: a heater; (2) The cathode assembly for an electron tube according to claim 1, wherein at least one of the inner and outer surfaces of the cathode sleeve is treated with a black finish. (3) The electronic device according to claim 1 of the utility model registration, characterized in that the heater is made of a coiled filament with a variable pitch, and is tightly wound around a portion corresponding to the center of the base metal plate. Cathode structure for tubes. (4) The cathode assembly for an electron tube according to claim 1 or 3, wherein the heater is formed in a U-shape or a helical shape.