KR100728773B1 - Inner shield for cathode ray tube - Google Patents

Abstract

The present invention relates to an inner shield for a cathode ray tube that can minimize the amount of change in landing of an electron beam caused by a magnetic field in the N-S direction by varying the distribution of the magnetic field around the inner shield.

A flange portion fixed to the mask frame, a pair of long side body portions and a short side body portion having a predetermined inclination such that the gap between the flange portion toward the electron gun is gradually narrowed, and an upper surface opening facing the electron gun; In addition, the two short sides of the upper opening is formed with a notch having at least two or more cutouts concave toward the flange portion to provide an inner shield for the cathode ray tube for changing the distribution of the geomagnetic field in the direction of reducing the horizontal force applied to the electron beam.

Cathode ray tube, inner shield, magnetic shield, mask frame, electron gun, notch, double unnotch, electron beam movement

Description

Inner shield for cathode ray tube {Inner shield for cathode ray tube}

1 is a side cross-sectional view of a cathode ray tube equipped with an inner shield according to the present invention.

2 is a schematic view for explaining the basic axis of the cathode ray tube.

3 is a perspective view of the inner shield according to the present invention;

4 is a perspective view of an inner shield according to another embodiment of the present invention.

5 is a graph showing the change of the geomagnetic field distribution in the prior art and the present invention.

6A and 6B are schematic diagrams for explaining the N-S movement amount and the E-W movement amount.

7 is a perspective view of an inner shield according to the prior art;

The present invention relates to an inner shield for a cathode ray tube, and more particularly, to an inner shield for a cathode ray tube capable of minimizing a change in landing of an electron beam by a geomagnetic field by changing a distribution of a geomagnetic field around an inner shield.

In general, a cathode ray tube is a display device that implements a predetermined screen by scanning a fluorescent film screen with three-stage electron beams emitted from an electron gun. In this case, the electron beam path is subjected to a geomagnetic field generated by the earth's north and south poles. Changes are influenced by purity characteristics, raster position, and convergence characteristics.

These geomagnetic fields are divided into vertical components perpendicular to the ground (vertical geomagnetic field) and horizontal components parallel to the ground (horizontal geomagnetic field), and represent different values depending on the place on the earth. The electron beam movement can be explained by dividing the NS movement amount and the EW movement amount according to the direction in which the cathode ray tube is directed.

That is, as shown in Figs. 6A and 6B, the NS movement amount means the electron beam movement amount by a component that matches the tube axis zz of the cathode ray tube in the horizontal geomagnetic field, and the EW movement amount is the same as the tube axis of the cathode ray tube in the horizontal geomagnetic field. Means the amount of electron beam movement by the vertical component.

On the other hand, the landing change amount of the electron beam appearing on the screen under the influence of the geomagnetic field can be analyzed by dividing it into a horizontal component and a vertical component.

At this time, in both the shadow mask which is mainly applied to the commercial cathode ray tube and has a long slot in the vertical direction, and the shadow mask which is mainly applied to the industrial cathode ray tube and has a dot-shaped hole, the horizontal moving component of the electron beam is defined as the electron beam. Because of the distance away from the slot or hole, suppressing this horizontal shift component is an important task.

Therefore, the inner shield is mounted inside the cathode ray tube for the purpose of reducing the amount of change in the landing of the electron beam caused by the geomagnetic field. FIG. 7 is a perspective view of the inner shield according to the prior art, and the inner shield 1 mainly has a high permeability and a low coercive force. It is made of a metal material and is fixedly installed behind the mask frame 3 so as to surround the electron beam path.

As a result, the inner shield 1 becomes a kind of magnetic material during driving of the cathode ray tube, and serves to change the distribution of the surrounding magnetic field in a direction to reduce the amount of change in landing of the electron beam while canceling or constructive interference with the geomagnetic field around the electron beam.

However, most inner shields, including the above structure, do not have good shielding effect against the NS magnetic field, and thus the amount of NS movement is reduced. In particular, the inner shield has a suppression effect on the horizontal motion component of the electron beam, which greatly affects the screen characteristics. It is weak and has a limitation that practical earth magnetic shielding function is not excellent.

Therefore, the present invention is designed to solve the above problems, an object of the present invention is to effectively reduce the NS movement amount, in particular the cathode ray beam which can improve the screen quality by reducing the horizontal movement amount of the electron beam which has a great effect on the screen characteristics To provide a tolerance inner shield.

In order to achieve the above object, the present invention,

A flange portion fixed to the mask frame, a pair of long side body portions and a short side body portion having a predetermined inclination such that the gap between the flange portion toward the electron gun is gradually narrowed, and an upper surface opening facing the electron gun; ,

The two short sides of the upper opening are formed with notches having at least two or more cutouts concave toward the flange to provide an inner shield for cathode ray tubes that changes the distribution of the geomagnetic field in a direction that reduces the horizontal force applied to the electron beam. .

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings.

1 is a side cross-sectional view of a cathode ray tube equipped with an inner shield according to the present embodiment, and FIG. 2 is a schematic view for explaining a basic axis of the cathode ray tube.

As shown in the drawing, the cathode ray tube combines the face panel 2, the funnel 4, and the neck portion 6 integrally to form a vacuum bulb 8, and a plurality of R, G on the inner surface of the face panel 2. And a fluorescent screen 10 formed of a B fluorescent film, and a deflection yoke 12 and an electron gun 14 are integrally mounted to the outer circumferential surface of the funnel 4 and the inner circumferential surface of the neck portion 6, respectively.

A shadow mask 16 having a plurality of beam passing apertures 16a formed therein is fixed to the mask frame 18 and installed inside the cathode ray tube so as to face the fluorescent screen 10, and one end of the inner shield 20. It is fixed to the mask frame 18 and mounted to surround the electron beam path.

According to the above-described configuration, when the electron gun 14 emits a three-stage electron beam corresponding to the screen signal, the electron beam is deflected by the magnetic field in which the deflection yoke 12 is generated to form a raster on the screen. By the R, G, B fluorescent film is separated by the correct color and the screen is implemented.

As such, the electron beam must move along the designated path, forming a raster specified by the deflection magnetic field, and the three-stripe electron beam matches exactly at one beam passing aperture 16a (i.e., achieves good convergence characteristics). Accurate screen can be realized.                     

Thus, the inner shield 20 surrounding the electron beam path serves to shield the geomagnetic field affecting the electron beam movement to a certain level. In particular, the present embodiment effectively reduces the horizontal movement amount of the electron beam by the geomagnetic field in the NS direction. Provides a new configuration of inner shield.

3 is a perspective view of the inner shield according to the present embodiment, wherein the inner shield 20 is connected to each other toward a flange portion 22 fixed to the mask frame 18 and an electron gun not shown in the flange portion 22. It consists of a pair of long side body portion 24 and short side body portion 26 having a predetermined inclination so that the gap is gradually narrowed, and two short sides of the upper side opening 28 concave toward the flange portion 22. It consists of a notch 30 having a shape.

As the notch part 30 has two cutouts concave toward the flange part 22, the center part of each notch part 30 is closer to the electron gun than the cutting part, and the angles forming the notch part 30 are different. The incision shapes can be symmetrical to each other.

In addition, each cutout shape of the notch part 30 may be formed in a shape that is gently concave in an ellipse shape toward the flange part 22 as shown.

In addition, as shown in FIG. 4 as another embodiment of the present invention, each cutout shape of the notch part 30 may have a sharply concave shape in a V shape toward the flange part 22.

In both of the above embodiments, the notches 30 which are provided at two short sides of the upper surface opening 28 and have two cutout shapes in the direction of reducing the horizontal force received by the electron beam by the geomagnetic field in the NS direction. It changes the distribution of the geomagnetic field around the inner shield 20 to reduce the horizontal movement of the electron beam.

That is, the horizontal force Fx (N) applied by the external geomagnetic field to the electron beam can be expressed by the following equation (1).

Fx = -e (VyBz-VzBy)

Here, e (C) is the charge amount, Vy and Vz (m / s) are the y- and z-direction velocities of the electron beam, and By and Bz (T) are the magnitudes of the y- and z-direction geomagnetic field components, respectively.

As described above, the force in the horizontal direction defined by Equation 1 is determined by the magnitude of the geomagnetic field formed around the electron beam, that is, By and Bz values, in a state where the speed of the electron beam is constant.

Accordingly, the present embodiment reduces the absolute value of Fx by changing the distribution of the geomagnetic field around the inner shield 20, that is, By and Bz, by using the notch 30 described above. Is a graph showing the distribution change of the NS geomagnetic field with respect to the electron beam landing on the screen diagonal portion in the inner shield and the inner shield according to the present embodiment.

Here, the inner shield according to the prior art is a configuration in which notches are formed at two short sides of the upper opening as shown in FIG. 7, and in the prior art and the present embodiment, a pair of long side and short side body parts have the same size as the same material. The produced one was used.

As a result, the By 'and Bz' distribution when the inner shield is mounted according to the prior art and the By and Bz distribution when the inner shield is mounted according to the present embodiment are measured and illustrated in the graph, and the horizontal axis of the graph is an electron gun 14. ) Refers to the distance on the tube axis (z-axis in the figure) to the fluorescent film screen 10, the vertical axis represents the intensity of the magnetic field.

In particular, the reference line (R / L) on the horizontal axis represents a point on the tube axis at which the angle formed between the straight line and the tube axis is the maximum deflection angle when the straight line is drawn on the tube axis in the diagonal axis of the face panel. Denotes the starting point of deflection of the electron beam.

In addition, the 0.0 point on the horizontal axis means the starting point of the inner shield where the upper opening 28 of the inner shield 20 is located, and the intensity of the magnetic field having a negative value indicates that the arrow tip of the three axes shown in FIG. This means that the magnetic field is distributed in the opposite direction to the plus direction.

Therefore, when looking at the change in the distribution of the geomagnetic field shown in the graph, in the structure according to the present embodiment, By represents an increased value of the conventional By 'over the entire section from R / L to the fluorescent screen.

In the structure according to the present embodiment, Bz shows a pattern of repeated decrease and increase as compared with the conventional Bz 'from R / L to the fluorescent screen. As a result, when comparing the sum of them throughout the geomagnetic field measurement interval, Bz according to the present embodiment shows a value that is similar to or less than that of the conventional Bz '.

Accordingly, when Bz decreases and By increases over the cathode ray tube tube axis, Bz decreases, and the difference between these Bz and By decreases, and the absolute value of Fx defined in Equation 1 decreases. This can reduce the absolute value of Fx even when Bz increases than the existing Bz ', if By increases more than Bz.                     

The reason why the By component is increased in the inner shield of the present embodiment is because the long shield and the short side body portion of the inner shield are made of a high investment material, and the magnetic field concentrates at a high magnetic permeability. This is because, when formed, Bz flowing along the tube axis is concentrated on the long side and changes in the y-axis direction.

Therefore, this embodiment effectively reduces the horizontal force on the electron beam by reducing the difference between Bz and By. The following Table 1 shows the intensity of each magnetic field throughout the geomagnetic field measurement intervals in this embodiment and the prior art. S is compared with the size of Fx.

Bz sum (G) By sum (G) Bz-By (G) Fx (N) Example 43 1.08 41.9 3.05 × 10 ^-14 Comparative example 42.9 -1.38 44.3 3.31 × 10 ^-14

Here, Fx is calculated by substituting Vy and Vz mentioned in Equation 1 at 0.460 × 10 ⁸ m / s and 0.675 × 10 ⁸ m / s, respectively.

Thus, it can be seen that the present embodiment in which the notches 30 are formed at two short sides of the upper opening 28 effectively reduces the horizontal force applied to the electron beam by the N-S geomagnetic field as compared with the prior art.

Although the preferred embodiments of the present invention have been described above, the present invention is not limited thereto, and various modifications and changes can be made within the scope of the claims and the detailed description of the invention and the accompanying drawings. Naturally, it belongs to the range of.

As described above, the present invention can effectively reduce the horizontal force applied to the electron beam by the N-S geomagnetic field by forming a W-shaped notch at two short sides of the upper opening facing the electron gun. Therefore, it is possible to prevent the deterioration of screen characteristics such as other color invasion by reducing the amount of horizontal movement of the electron beam, and to improve the screen quality by improving the purity and convergence characteristics and realizing the accurate raster by guaranteeing a more accurate electron beam path. Has an advantage.

Claims (4)

An inner shield for cathode ray tubes located between the mask frame and the electron gun in a cathode ray tube including a shadow mask spaced apart from the fluorescent screen, a mask frame for supporting the shadow mask, and an electron gun for emitting an electron beam toward the fluorescent screen In A flange portion fixed to the mask frame, a pair of long side body portions and a short side body portion having a predetermined inclination such that the interval between the flange portions toward the electron gun is gradually narrowed, and an upper surface opening facing the electron gun; Include, The inner shield for the cathode ray tube for changing the distribution of the geomagnetic field in a direction of reducing the horizontal force applied to the electron beam, consisting of a notch having at least two cutouts concave toward the flange portion of the upper opening. The method of claim 1, An inner shield for a cathode ray tube comprising two cutouts in which the notches are symmetric to each other. The method of claim 2, An inner shield for cathode ray tubes, wherein each cutout shape constituting the notch portion is concave in an elliptical shape toward the flange portion. The method of claim 2, An inner shield for cathode ray tubes, wherein each cutout shape constituting the notch portion is concave in a V-shape toward the flange portion.

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