JPH0474816B2 - - Google Patents

Description

[Detailed Description of the Invention] (Technical Field of the Invention) The present invention relates to a fast-acting cathode assembly for an electron tube, and more particularly to a fast-acting cathode assembly for an electron tube suitable for color cathode ray tubes, display cathode ray tubes, image pickup tubes, etc. It is.

(Technical background of the invention) An example of a conventional cathode structure for a fast-acting electron tube is shown in the first example.
To explain with the diagram and Fig. 2, the plate thickness is approximately 40 μm.
The heaters 2, 2 are installed inside the cathode cylinder 1 mainly made of nickel as shown below, and are formed on the top surface of the electron emissive oxide layer 3, and the heaters 2, 2 have a wire diameter of 20 μm to 30 μm. It consists of a heater coil 4 made of a tungsten wire formed into a coil, and an insulating layer 5 of sintered alumina that hardens the heater coil 4 from both the inside and outside, the outer peripheral surface of which is in close contact with a part of the cathode cylinder 1, And it is almost completely surrounded by this part. Such a cathode cylinder 1 is initially
As shown by reference numeral 11 in the figure, it is formed into a cylindrical shape with a rectangular cross section, and its internal space is filled with heaters 2, 2.
It is designed to be large enough to still leave a considerable gap even if inserted. In the compression process, the shaping tables 6, 6 are moved in the direction of the arrow in FIG. 2, so that the above-mentioned relationship is established between the heaters 2, 2.

In such a cathode structure for an electron tube, a part of the cathode cylinder forms an overlapping part due to the compression process applied to the cathode cylinder, and the other part is in close contact with the outer peripheral surface of the heater, and the heater is used as a core. Since the entire cathode cylinder is deformed, 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 harmful effects caused by relative positional deviations between the elements, but also improves heating efficiency, and is particularly effective as a thermionic emission source for small cathode ray tubes. On the other hand, the cathode structure for an electron tube has a fatal drawback as described below.

(1) Since it is supported only at the end of the heater, the structure is weak against vibrations and shocks. Furthermore, considering the thermal deformation characteristics of the heater coil, the distance between the electron-emitting oxide layer and the grid electrode facing it (G ₁ -K distance) is not constant, and therefore the cut-off voltage of the grid electrode fluctuates. However, in a three-electron gun type color picture tube, the white balance becomes poor.

(2) When heating the heater, the heater may break due to differences in thermal expansion between the tungsten, alumina oxide coating, and the nickel-based cathode cylinder that make up the heater, or the heater may peel off due to the coating material peeling off. Accidents of touching the cathode cylinder are likely to occur.

(3) A step in which the heater is inserted into the cathode cylinder having a rectangular cross section, and then the cathode cylinder is brought into close contact with the outer peripheral surface of the insulating layer of the heater through a compression process, and an overlapping part is formed in a part of the cathode cylinder, The process of inserting and compressing the heater is extremely difficult due to the fragility of the heater materials tungsten and alumina.

(4) W+A ₂ O ₃ →W _n O _o +A between tungsten and alumina, which are materials used as a heater
(where m and n are positive integers) reaction occurs, and this
Thickness of oxygen in W _n O _o mainly made of nickel
A so-called gas dove phenomenon occurs in which the crystal grain boundaries of the cathode structure with a diameter of 40 μm or less are diffused and the composition of the upper oxide layer is changed, thereby extremely shortening the life of the cathode.

A second conventional example is shown in FIGS. 3 to 5. Third
Figures 5 to 5 show the main parts of the cathode structure for an electron tube,
3 is a perspective view thereof, FIG. 4 is a plan view thereof, and FIG. 5 is a sectional view of FIG. 4 taken along line A-A'.

That is, the cathode assembly 20 for an electron tube includes cylindrical bodies 22, 22 which are welded and fixed such that at least one end is in contact with the inner surface of the circular part of a first cathode support cylinder 21 formed in an elliptical shape, for example, and the cylinders 22, 22 which are welded and fixed. cylinder body 2
A cathode support cylinder formed by passing heater conductive support members 23, 23 through 2, 22 and then fixing them with an insulator such as adhesive glass 24, 24, and a pair of support pieces 26, 26 that support the cathode structure. , this support piece 26,
The contact points 28, 28 are arranged perpendicularly and parallel to the electron gun axis Z via one ends 27, 27 of the electron gun 26, and the cross-sectional shape of the welded contact points 28, 28 is approximately circular, and the inner and outer surfaces are blackened. Two cathode sleeves 29, 29 made of a nickel-chromium-tungsten alloy with a diameter of 15 μm, a diameter of 0.8 mm, and a length of 3 mm are arranged along the ridgeline of these cathode sleeves 29, 29 so as to center around the electron gun axis. At the same time, welding points 30, 30, 3 are attached to the cathode sleeves 29, 29, respectively.
For example, thickness 40μm, fixed through 0,30
Base metal 31 mainly made of nickel with a diameter of 1.4 mm
, an oxide layer 32 that emits thermoelectrons and is adhesively formed on the base metal 31, and cathode sleeves 29, 2.
Alumina 34 is sintered on the inner and outer surfaces of a heater coil wound in a coil shape that can be inserted through the openings in the same direction of 9, and welding points 35 are attached near both ends to the heater conductive support members 23, 23, respectively. 35
The heater 36 and the cathode assembly 2 welded together through
The other end portions of the support pieces 26, 26 supporting the cathode 0 are welded to the first cathode support tube 21.

The drawbacks of the cathode structures shown in FIGS. 3-5 are shown in FIG. 6a. FIG. 6 shows the temperature rise curve of the cathode sleeve and base metal from immediately after the heater is ignited until the cathode operates normally. Before explaining Fig. 6a, the parts of the two cathode sleeves 29, 29 will be explained with Fig. 6b.
The front position at 90° is designated as 29a, and the central side surface of the sleeve is designated as 29b. Centering on this 29b, 29
The opposite side of a-29b is designated as 29c. Also, the corresponding points on the opposite sleeve are 29a', 29b', 29
Let it be c′. The center of the base metal is 31d.

If temperature is shown on the vertical axis of Figure 6a, points 29a and 2
Since 9c' has a support piece, heat escapes by conduction, and the rising curve and stable temperature are low. or,
29c and 29a' do not allow heat to escape through conduction, so the temperature rises quickly, but the stable temperature is also higher than that at the center 31d of the base metal. Also, the central side surfaces 29b, 29b' of the cathode sleeve are higher than each part of the sleeve and the base metal. These phenomena occur because the heaters are arranged equally with respect to the cathode sleeve 29, and because the support piece 26 is connected and the amount of heat is lost due to heat conduction. Therefore, the parts that require quick action are the base metal, and the cathode sleeves 29c, 29a', 29
It is undesirable for b, 29b' to overheat. Also, even if the heater windings are concentrated only in the center, 29b, 2
Overheating of 9b' and a decrease in the temperature raising ability of 29a and 29c' are unavoidable.

As a countermeasure to this problem, it is possible to change the welding points indicated by the x marks to one point each in the center of the length of the sleeve.
1.0mm, and the effective diameter of the electron emitting surface is 0.6mm. The effective diameter of the electron emitting surface needs to be large enough to take into account the misalignment between the electron gun axis and the electron emitting surface and the life span, so the welding point cannot be changed to the center in the length direction of the sleeve.

(Objective of the Invention) An object of the present invention is to improve the above-mentioned drawbacks and to provide a cathode structure with excellent rapidity.

(Summary of the Invention) The present invention provides two cylindrical sleeves that are arranged adjacent to each other in parallel on a plane at right angles to the electron gun axis, and two cylindrical sleeves that are placed so as to be in contact with the ridgelines of the two cylindrical sleeves and that are arranged on the ridgeline. In a fast-acting cathode structure for an electron tube, the cathode assembly includes a base metal having fixing points at the base metal, and a heater installed in each of the two cylindrical sleeves, wherein the two cylindrical sleeves have a predetermined dimension in the length direction. This fast-acting cathode structure for an electron tube is characterized in that the sleeves are fixed by being shifted from each other, and the fixing point is located approximately at the center of each sleeve in the length direction.

The plan view of the fast-acting cathode structure according to the present invention is shown in FIG.
As shown in the figure. Parts that are the same as in the past are designated by the same reference numerals. 40 welds the cathode sleeves of the cathode bodies 41 and 42 at points 43 and 43. This cathode sleeve is made of a nickel-chromium alloy or a nickel-chromium tungsten alloy, and its surface is blackened in a moisture-added hydrogen furnace. In the figure, 31 is a base metal, on which is an electron emitting material (BaSrCa)
Coated with Co ₃ 32. 26 is a support piece attached to the cathode sleeves 41, 42 near their respective ends 27, 2.
It is welded at 7. Reference numerals 45 and 46 denote heaters, and the longitudinal centers 41a and 42a of the cathode sleeves are made to substantially coincide with the center of the longitudinal heat generating portion of the heaters.
Moreover, the longitudinal centers 41a and 42a of the cathode sleeves
The flange-like portion of the base metal 31 is welded. By doing this, the center of the heat generating part of the heater and the center of the cathode sleeve in the length direction can be made to coincide with each other, thereby making it possible to match the heat generating center part with the center part of the cathode sleeve. Also, 4 is centered on the center line that crosses the center point 31d of the cathode base metal 31 in the radial direction of the cathode sleeve.
Welding to the cathode base body may be additionally performed at portions 41b and 42b where the ridgeline of the cathode sleeve and the flanged portion of the basic metal contact 1a and 42a.

(Example of the Invention) Example 1 will be described with reference to FIG. 7.
Cathode sleeves 41 and 42 have an outer diameter of 0.8 mm and a thickness
It is 15 μm and 3 mm long. The thickness of the cathode substrate is 40μm,
The outer diameter is 1.4mm, and the center 1.0mm is molded into a cap shape. The center line of this cap-shaped base metal flange-like portion has a diameter of 1.2 mm. The point where the center line of the flange-shaped center line of the cap-shaped base metal (1.2 mm in diameter) and the ridgeline of the two sleeves with a diameter of 0.8 mm touch is the axis of the sleeve from a line that passes through the center point 31d of the cap-shaped base metal and crosses at right angles to the sleeve axis. The points 41a and 42a, which are shifted 0.45 mm toward the supporter 26 in the direction, are the first connection points. This first connection point is calculated as the center point in the longitudinal direction of the cathode sleeve, and 41 and 42 are arranged. That is, the ends of the two sleeves were shifted by about 0.9 mm.

The heaters 45 and 46 are made by winding a tungsten rhenium alloy wire with a diameter of 36 μm around a molybdenum wire with a diameter of 86 μm to form a primary coil, which is then formed into a variable pitch with a dense center on a secondary mandrel with a diameter of 178 μm. The effective length of the tungsten rhenium alloy wire is 42 mm, and Ef3.15V per heater.
If 140mA is used, and if two are used in parallel, if 280mA is used, the temperature of the cathode base metal can be heated to 800℃.

It is also possible to provide the second bonding portions 41b, 42b on the opposite side of the cap-shaped base metal 41a, 42a across the center line of the cap-shaped base metal. This joint 4
1b and 42b allow heat to flow through the cap-shaped base metal, so that the temperature rises more quickly.

By aligning the center of the cathode sleeve with the center of the heater and joining it to the cap-shaped base metal at this center, and allowing the flow of heat immediately after the heater ignition to flow through the cap-shaped base metal, an indirectly heated cathode can be created. However, it is possible to achieve a temperature rise that is almost the same as that of a directly heated cathode.

Figure 8a shows the temperature increase curve.
Figure b shows the connection point between the cap-shaped base metal and the cathode sleeve. A curve 41a shows how the temperature increases at points 41a and 42a. Curve 41b is point 4
The temperature rise of 1b and 42b is shown by curve 41e.
shows the temperature rise at points 41c and 42c.

As can be seen from this figure, the temperature rise rate of the curve 41a is extremely fast and the temperature is stable quickly. The curve 41b rises later than the curve 41a, but when stable, the difference from the center point 31d of the cap-shaped base metal is small. Since the curve 41c is connected to the support piece, the temperature rise is slow and the temperature reached is low.

Here, when comparing the temperature at the center point 31d of the base metal between the cathode of the present invention and the conventional cathode using FIG. 8a and FIG. 6a, for example, the temperature 2 seconds after switching on is as follows. The temperature of the cathode is 370°C, whereas the temperature of the conventional cathode is 280°C, which is 90 degrees higher in the present invention. This is extremely advantageous in shortening the image output time, and means that if the image output time is kept constant, heater power can be saved.

The cathode body 40 is held by a support 26 connected to a cathode support cylinder 21 formed in an elliptical shape as shown in FIGS. 3 to 5. The heater is also welded to the heater conductive support member 23. The heater conductive support member 23 is fixed to the cylindrical body 22 via an insulator 24, and the cylindrical body 22 is welded to the cathode support cylinder 21. In this structure, the cathode structure is individually molded, and is completed as an electron gun through the first to sixth gratings embedded in the bead glass and the cathode support cylinder (not shown).

A color cathode ray tube obtained using the cathode structure of Example 1 by a predetermined manufacturing method had an image output time of 1.5 seconds. In contrast, the conventional cathode structure shown in FIG. 4, which was manufactured at the same time, took 2.0 seconds, confirming that the cathode structure of the present invention is superior.

The cathode structure of Example 1 was intended to be used in a color electron gun, so an elliptical cathode support member was used. A holding method may be used in which supports are embedded in a circular ceramic substrate.

Example 2 will be described with reference to FIG. 9.

50 is a cathode assembly main body, and cathode sleeves 51, 5
2 are placed in parallel, and the first connection point between the cap-shaped base metal 31 and the cathode sleeve is shifted toward the supporter 57 as described in the first embodiment, and this point is set as the center in the length direction of the cathode sleeve. Similarly, it is also possible to provide a second bonding point on the opposite side of the first bonding point with respect to the center line of the base metal 31 as a boundary. An electron radioactive substance 32 is placed on the top surface of the base metal 31.
Place.

The cathode body support is constructed by inserting a heater conductive support member 56 and a cathode support member 55 into a through hole provided in the ceramic substrate 54 and fixing them with a binder 58 such as glass. A support element 57 is attached to the cathode support member 55 and tied to the cathode sleeve.
The heater 53 differs from the first embodiment in that the coiled coil is bent into a hairpin shape, resulting in Ef6.3V If140mA. Both ends of the heater are connected to heater conductive support members 56, -
56. The heat generating portion of the heater 53 has the secondary coil densely arranged in the center to concentrate the heat generating portion, as in the first embodiment, and the first bonding point between the cathode sleeve and the base metal is aligned with the center of the heater heat generating portion. A display cathode ray tube obtained using the cathode structure of Example 2 by a predetermined manufacturing method had an image output time of 1.6 seconds. On the other hand, the conventional example shown in Fig. 6, which was manufactured in the same way, is
It was confirmed that the cathode structure of the present invention is excellent.

(Effects of the Invention) According to the present invention, an efficient temperature increase can be obtained,
A fast-acting cathode structure for an electron tube with excellent fast-acting properties can be realized.

[Brief explanation of the drawing]

1 to 5 are diagrams showing the schematic structure of a conventional cathode structure, FIGS. 6 and 8 are diagrams showing the temperature rise of each part of the cathode body in the conventional cathode structure and the cathode structure of the present invention, respectively. The figure is a plan view showing one embodiment of the cathode assembly of the present invention, and FIG. 9 is a perspective view showing another embodiment of the cathode assembly of the present invention. 29, 41, 42, 51, 52... Cylindrical sleeve, 31... Base metal, 36, 45, 46, 5
3... Heater.

Claims (1)

[Claims] Two cylindrical sleeves arranged adjacent to each other in parallel on a plane at right angles to the electron gun axis, and a fixing point placed on the ridge line and placed in contact with the ridge line of the two cylindrical sleeves. In the fast-acting cathode assembly for an electron tube, the two cylindrical sleeves are shifted by a predetermined dimension in the longitudinal direction, and the two cylindrical sleeves are shifted by a predetermined dimension in the longitudinal direction. A fast-acting cathode assembly for an electron tube, wherein the fastening point is located approximately at the center of each sleeve in the length direction.