JPH0278135A - Inline-type electron gun - Google Patents

Abstract

PURPOSE:To negate diamagnetic field due to generation of eddy current so as to lower misconvergence by running an electric current of a conductor loope in the direction so as to intensify the change of a magnetic field in a near area of a center beam passing hole. CONSTITUTION:Conductive wire 21 is brought to cross in two points and each side loope 40a, 40c is formed upside of a side beam passing hole and a center loope 40b is formed upside of a center beam passing hole. When horizontal deflecting magnetic field 30 is increased, eddy current 31a, 31b runs in the side plane of a shield cup 8 so as to inhibit the change. A diamagnetic field 32 is thus formed and a deflecting magnetic field weakens in a near area to a center beam passing hole 15b as compared to side beam passing holes 15a, 15c. On the other hand, due to the change of the magnetic field 30, electromotive force is generated in each loope, the change of magnetic fluxes passing the closed curved plane 40a, 40c become larger than that passing the closed curved plane 40b, an electric current 23 starts running in the whole of the loopes, and a magnetic field 22b in the direction to intensify the magnetic field 30 in a near area of the hole 15b is generated. As a result, the magnetic field in the near area to the hole 15b is prevented from weakening.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to an in-line electron gun for a color cathode ray tube, and is particularly suitable for reducing misconvergence (beam shift) caused by the generation of eddy currents during high-speed deflection. Regarding inline type electron guns.

[Conventional technology]

The in-line electron gun of a color cathode ray tube generates three electron beams, and each electron boom is focused on a - point on a phosphorescent surface (actually on a shadow mask, but for simplicity, it is called phosphorescent surface). , corresponding to each beam, red, green,
It emits blue phosphor. That is, an in-line electron gun generally includes a cathode with three electron beam generation sources in a horizontal line, a group of electrodes that focus and accelerate the electron boom,
electrically connected to the highest potential electrode of the electrode group;
A shield cup for shielding an electric field is provided, and the electrode group and the shield cup have three openings on each opposing surface, consisting of one center beam passage hole and two side beam passage holes through which the electron beam passes. The electron beam is deflected by a deflection yoke which forms a deflection magnetic field and scans the fluorescent surface.

Conventionally, the deflection frequency of the horizontal deflection magnetic field formed by the deflection yoke was about 15.7 kHz, but as cathode ray tubes have become larger and more precise in recent years, horizontal deflection magnetic fields with a deflection frequency of about several times this frequency have been used. It's starting to look like this. As a result, an eddy current is generated in the shield cup, which is a conductor, and a problem has arisen in that the center beam (green beam) shifts to the right on the phosphor surface. This situation is shown in Figures 10 and 11.
This will be explained using figures.

That is, as shown in FIG. 10, if the horizontal deflection magnetic field 30 changes to increase in the direction of the arrow in the figure, an eddy current 3 is installed on the side surface of the shield cup 8 to prevent this change.
1a and 31b flow in the direction shown by the arrow in the figure. As a result, a demagnetizing field 32 is generated in the direction of the arrow shown by the dotted line in FIG. A problem arises in that the beam is shifted to the right on the screen compared to the side beam.

In order to solve such problems, Japanese Patent Application Laid-open No. 61-7723
Publication No. 7 has a slit at the top of the shield cup,
A method for preventing the generation of eddy currents is described. However, this method has the problem that the structure of the shield cup becomes weak.

Furthermore, in Japanese Patent Application Laid-Open No. 61-91835, auxiliary members made of a non-magnetic good conductor are installed above and below the side beam passage hole of the shield cup, and by generating eddy current in this auxiliary member, the side beam and center A method for reducing beam shear is described. in this way,
Since the raster (beam trajectory) on the screen is entirely shifted to the right, it is necessary to correct this by other means.

[Problem to be solved by the invention]

As mentioned above, conventional structures devised to reduce center beam deviation caused by eddy currents have disadvantages such as weakening of the shield cup and the need for auxiliary means. There have been problems in that it becomes difficult to support the electron gun when the electron beam is deflected, and that the correction indigo by the correction means must be changed for each deflection frequency.

An object of the present invention is to provide an in-line electron gun that can reduce misconvergence by canceling the demagnetizing field caused by the generation of eddy currents without weakening the strength of the shield cup or requiring auxiliary means. .

[Means to solve the problem]

The above purpose is to generate a current due to temporal changes in the deflection magnetic field at a location other than the vicinity of the center beam passage hole inside the shield cup, and to conduct this current through a conductor wire near the center beam passage hole in a direction that strengthens the change in the magnetic field in that area. This is achieved by arranging means.

[Effect]

When the magnetic flux passing through a closed curved surface surrounded by a loop of conducting wire changes, an electromotive force is generated in the loop in the direction that prevents changes in the internal magnetic flux, and current flows. Therefore, the conductor means of the present invention can cancel the demagnetizing field caused by the eddy current flowing in the shield cup by drawing this current out of the loop with a conductor and flowing it in a direction that strengthens the change in the magnetic field near the center beam passage hole. is constructed based on this principle. Here, the magnitude of the magnetic field near the center beam passage hole is proportional to the demagnetizing field generated by the eddy current flowing in the shield cup even if the deflection frequency is changed, and since the direction is opposite, the demagnetizing field can always be canceled. Further, even if the loop is provided, the structure of the shield cup will not be weakened.

〔Example〕

Hereinafter, one embodiment of the present invention will be explained with reference to FIGS.
This is applied to a U-type electron gun.

In the color cathode ray tube 10 shown in FIG. 3, the in-line electron gun 9 has a cathode 1 that generates three electron beams 14, and a cathode tf! The first grating electrode 2 and the second grating electrode 3 which together with t constitute the triode part, the third grating ti4, the fourth grating electrode 5, the first grating electrode 6 and the sixth grating electrode which constitute the main lens part
It includes a grid electrode 7 and a shield cup 8. Inside the electron gun, the electron beam 14 is focused and accelerated by the electrode group constituting the above-mentioned three-pole section, enters the shield cup 8 connected to the sixth grid tlff17, which is the maximum potential electrode, and enters the shield cup 8. In the electron beam 14, the side beams 14a and 14c are concentrated and focused in a direction approaching the center beam 14b, pass through the shadow mask 11, and reach the fluorescent surface 12. Further, the deflection yoke 13 deflects the electron beam 14 to scan the fluorescent surface 12.

FIG. 1 shows the inside of the shield cup 8. Electron beam passing hole 15a, 1 of shield cup 8
Above and below 5b and 15c, flat plate-shaped insulating supports 20 made of an insulator are provided approximately parallel to the plane where the three beams are lined up, and three loops are formed by conducting wires 21 on each insulating support 20. The intersections of the two conductive wires formed are coated with an insulating film to prevent them from being electrically connected to each other. An enlarged view of this conducting wire portion is shown in FIG.

In FIG. 2, a single conductor wire is crossed at two points to form a total of three loops: two side loops above the side beam passage hole and one center loop above the center beam passage hole.

In such a configuration, if the horizontal deflection magnetic field 30 changes so as to increase in the direction of the arrow in the figure as shown in FIG. 2, the side surface of the shield cup 8 is provided with a structure shown in FIG. As shown, eddy currents 31a and 31b flow in the directions shown by the arrows in the figure. As a result, a demagnetizing field 32 is generated in the direction of the arrow indicated by the dotted line in FIG. 11, and the deflection magnetic field is weaker near the center beam passage hole 15b than near the side beam passage holes 15a and 15c.

On the other hand, when the horizontal deflection magnetic field 30 changes in the direction of the arrow in FIG. 2, an electromotive force is generated in each loop of the conducting wire 21 in a direction that can prevent this change. The magnitude of the electromotive force is the closed curved surface 40a surrounded by each loop.

It is proportional to the magnetic flux change passing through 40b, 40c.

In this embodiment, the closed curved surfaces 40a, 40b, and 40 have approximately the same area. Therefore, the change in magnetic flux passing through the closed curved surfaces 40a and 40c surrounded by the loops on both sides is larger than the change in the magnetic flux passing through the closed curved surface 40b surrounded by the center loop, and in the entire loop, the current 23 flows in the direction of the electromotive force generated in the side loop. As a result, a magnetic field 22b is generated in a direction that strengthens the deflection magnetic field 30 near the center beam passage hole 15b.

That is, a magnetic field 22b is generated in a direction that cancels the demagnetizing field 32 caused by the eddy currents 31a and 31b. Therefore, the deflection magnetic field 30 is prevented from becoming weak near the center beam passage hole 15b, and misconvergence in which the center beam shifts to the right on the screen compared to the side beams can be reduced.

A second embodiment of the present invention will be described with reference to FIG. In FIG. 4, on the insulating support 20 there is a conductor &! 24 is wired by etching, and the conductive wire 24 runs along the side surface of the insulating support 20 from the front to the back of the insulating support 20 to form a continuous loop.

Also in this embodiment, since the conductor 24 is topologically the same as the conductor 21 described in the first embodiment,
In the center beam passage hole, changes in magnetic field can be strengthened by changes in magnetic flux above or below the side beam passage hole, and demagnetizing fields caused by eddy currents can be canceled. Further, according to this embodiment, since the conductive wires do not directly cross each other, there is no need to worry about insulation at the contact portion.

A third embodiment of the present invention will be explained with reference to FIG.

In FIG. 5, the conductive wire 25 is a thin conductive wire wound several times to form one loop, which is adhered onto the insulating support 20. In FIG.

Let us now examine the relationship between the number of turns of the conducting wire and the area of the closed curved surface and the magnitude of the magnetic field generated in the center loop. The electromotive force generated in one loop is proportional to the product of the number of turns of the conductor and the area of the closed surface surrounded by the conductor.

For simplicity, the areas of the side loops and the center loop are assumed to be the same S, and the numbers of turns are assumed to be Ns and NC, respectively. Since the change in magnetic flux passing through the closed curved surface created by the loop is proportional to (2Ns-Nc), the current flowing through the loop is also proportional to (2Ns-Nc). Therefore, the magnetic field generated in the center loose is (2Ns
-Nc) Proportional to Nc, if Ns is fixed, Ns = N
It is maximum at c.

Similarly, if the number of turns of the side loop and center loose are the same N, and the areas are SS and Sc, respectively, the change in magnetic flux penetrating the closed curved surface created by the loop is proportional to (2Ss-3c), so the magnetic field generated in the center loop (2Ss
-3c) Proportional to Sc, fixing SS, ss = s
It can be seen that it is maximum when c. Therefore, in order to obtain a large effect with a small amount of material, it is sufficient to make the number of turns and area of the side loop and center loop the same.

A fourth embodiment of the present invention will be described with reference to FIG. In FIG. 4, the conductive wires 26a and 26b independently form two side loops, and portions 27a and 27b of the loops are shaped so as to surround the magnetic field passing through the center beam passage hole.

In this embodiment, a current according to the change in magnetic flux flows through each side loop independently, and as a result, a magnetic field is generated near the center beam passage hole by the portions 27a and 27b of the loops, and a demagnetizing field is generated by the eddy current. cancel.

This embodiment has the advantage that there is no need to consider insulation at the intersection, and the configuration is simple.

Next, fifth and sixth embodiments of the present invention will be described with reference to FIGS. 7 and 8.

In the embodiment shown in FIGS. 7 and 8, side loops and side beam passage holes 15 are used as insulating supports for supporting conductors.
The plate members 20A and 20B are bent so that the distance between the center loop and the center beam passage hole 15b is longer than the distance between the center loop and the center beam passage hole 15b.

According to this embodiment, by providing the side loops, there is a possibility that the magnetic field near the side beam passage holes 15a, 15c may be affected, and this can be prevented.

A seventh embodiment of the present invention will be described with reference to FIG.

In FIG. 9, the conductive wire 28 is made of an electroconductive material. Further, the conductive wire 28 is constructed so as to connect two loops of the fourth embodiment shown in FIG.

In this embodiment as well, the center beam passage hole has a diameter of 28 mm.
A magnetic field is generated in the direction of increasing magnetic flux change by the Ω-shaped portion indicated by a, and the magnetic field caused by the eddy current can be canceled. In addition, in this example, since an electrostatic material is used, the wiring must be made sufficiently thin so as not to affect the normal static magnetic field component, but since the resistance of the conductor is 0, it is difficult to change the deflection magnetic field. The current flowing accordingly can be sufficiently large, and less heat is generated.

Although an embodiment in which the present invention is applied to a B-U type electron gun has been described above, the present invention is not limited to the B-U type electron gun, but can be applied to other electron guns such as unipotential type and pipotential type. It can also be applied to

〔Effect of the invention〕

According to the present invention, the demagnetizing field caused by the generation of eddy currents can be canceled out in accordance with changes in the deflection magnetic field that causes the eddy currents, so that unlike conventional structures, the structure becomes weaker and correction means is required. Misconvergence associated with this can be reduced without any problems.

[Brief explanation of the drawing]

FIG. 1 is a perspective view showing the inside of a shield cup in an in-line electron gun according to an embodiment of the present invention, FIG. 2 is a diagram showing the shape of a conducting wire provided in the shield cup, and FIG. FIG. 4 is a sectional view showing the entire color cathode ray tube equipped with an in-line electron gun, and FIG.
FIG. 5 is a perspective view of a conducting wire portion according to a third embodiment of the present invention, and FIG. 6 is a plan view of a conducting wire portion according to a fourth embodiment of the present invention. 7 is a diagram showing the shape of a plate member supporting a conducting wire according to a fifth embodiment of the present invention, and FIG. 8 is a diagram showing a plate member supporting a conducting wire according to a sixth embodiment of the present invention. is a diagram showing the shape of
FIG. 9 is a plan view of a conductor according to a seventh embodiment of the present invention, FIG. 10 is a diagram showing eddy currents flowing in a shield cup in a conventional in-line electron gun, and FIG. 11 is a diagram showing eddy currents caused by eddy currents. FIG. 3 is a diagram showing a generated demagnetizing field. Explanation of symbols 1... Cathode 2-7... Electrode group 8...
- Shield cup 9...Electron gun 13...Deflection yoke 14a, 14c...Side beam 14b...Center beam 15a, 15c...Side beam passage hole 15b...
Center beam passage hole 20; 20A: 20B...insulating support body 21;
24; 25; 26a, 26b; 28...
・Conductor wires 27a, 27b...part of side loop 28a
...Ω-shaped part 30... Deflection magnetic field 31a, 31
b...Eddy current 32...Diamagnetic field Applicant: Hitachi, Ltd. Representative Patent attorney Yuzuru Kasuga Figure 1 Figure 7 Figure 8

Claims (1)

[Scope of Claims] (1) A cathode having three electron beam generation sources arranged in a horizontal line, an electrode group for focusing and accelerating the electron boom, and an electrode having the highest potential among the electrode groups electrically connected to each other. a shield cup for connecting and shielding an electric field, and each of the electrode group and the shield cup has one center beam passage hole through which the electron beam passes and two side beam passage holes on opposing surfaces thereof. In an in-line electron gun in which an electron beam is scanned by a deflection yoke that is provided with three openings and forms a deflection magnetic field, a temporal change in the deflection magnetic field at a location other than near the center beam passage hole inside the shield cup. An in-line electron gun characterized in that a conductive wire means is provided to generate a current and to flow this current near a center beam passage hole in a direction that intensifies changes in the magnetic field in that part. (2) The conducting wire means has one center wire that intersects at two points at least above or below the three electron beam passing holes such that the winding direction is different between the center beam passing hole portion and the side beam passing hole portion. 2. The in-line electron gun according to claim 1, comprising a continuous conducting wire forming a loop and two side loops. (3) The in-line electron gun according to claim 2, wherein the sum of the two side loops is larger than the product of the area of the closed curved surface surrounded by the center loop and the number of turns. (4) The in-line electron gun according to claim 2, wherein the product of the area of the closed surface surrounded by the center loop and the number of turns is the same as that of each of the two side loops. (5) The conductor means forms two closed and independent side loops at least above or below the two side beam passage holes, and guides a current near the center beam passage hole through a part of the loops. 2. The in-line electron gun according to claim 1, wherein the in-line electron gun comprises two conductive wires. (6) The conductive wire means is composed of a continuous conductive wire that does not intersect at least in the upper or lower part of the three electron beam passage holes, and that a portion of the loop forms an Ω-shape at the center beam passage hole. The in-line electron gun according to claim 1, characterized in that: (7) The in-line type according to claim 1, wherein the conducting wire means is arranged such that the distance from the side beam passage hole is greater than the distance from the center beam passage hole. electron gun. (8) The in-line electron gun according to claim 1, wherein the conductive wire means is printed on an insulating support by etching. (9) The in-line electron gun according to claim 1, wherein the conducting wire means is an insulated conducting wire forming a loop made of multiple windings. (10) The in-line electron gun according to claim 1, wherein the conducting wire means is made of a superconductor. (11) A color cathode ray tube equipped with the in-line electron gun according to claim 1.