JP3569136B2 - CRT magnetic shield device - Google Patents

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a magnetic shield device of a cathode ray tube (cathode ray tube or CRT) used for a display device such as a general television receiver and a display of a personal computer, and particularly to a one-dimensional to three-dimensional external magnetic field from a power facility or the like. The present invention relates to a magnetic shield device for reducing an image fluctuation disturbance caused by an influence.
[0002]
[Prior art]
Generally, a cathode ray tube of an electrostatic focusing and electromagnetic deflection type is used as a cathode ray tube used for a display device such as a television receiver and a display of a personal computer. This cathode ray tube emits an electron beam at a high speed from an electron gun housed in a narrow neck in the latter half of the bulb against a screen (fluorescent surface) with a fluorescent film inside the front of a vacuum vessel (glass bulb). An electron tube that projects an image on the fluorescent surface by bending the electron beam up and down and left and right by the magnetic field created by the current flowing through a deflection coil placed at the base of the neck.
[0003]
In general, a magnetic shield encloses its target space or object in a container of magnetic material so that an external magnetic field does not reach the space therein or that the magnetic field inside the container does not affect the outside. Magnetic shielding means. However, as described above, it is very difficult to completely shield electromagnetic induction using a current component as an induction source.
[0004]
[Problems to be solved by the invention]
For example, television receivers and personal computer display devices placed in private houses and offices near power facilities such as distribution substations and distribution lines are affected by magnetic fields that use power facilities as induction sources. May cause sway disorder. In this case, it is an induction obstacle due to electric power of a commercial frequency of 50 Hz or 60 Hz. Since the frequency of the external magnetic field is low, the material of the housing is made of a high-permeability magnetic material. They are made thicker, layered, and reshaped. Then, in order to obtain a higher shielding effect, the shielding plates attached to the housing are joined together without any gap. Such a magnetic shield structure has the drawback that it is complicated and expensive, and poses a problem in appearance.
[0005]
Moreover, even if the conventional magnetic shield is strengthened, the fluorescent surface of the cathode ray tube cannot be covered with a magnetic material for the purpose of using the cathode ray tube of the display device. However, there remains a problem that the magnetic shielding effect against an external magnetic field incident in the axial direction (before and after) is insufficient, thereby causing an image fluctuation disturbance.
[0006]
An object of the present invention is to provide a simple structure without being restricted by the magnetic flux density and direction of a low-frequency external magnetic field from a power facility incident on a cathode ray tube of a display device, and without covering the fluorescent surface with a magnetic material. It is an object of the present invention to provide a magnetic shield device capable of attenuating an external magnetic field incident on the magnetic field and avoiding image fluctuation disturbance.
[0007]
[Means for Solving the Problems]
A CRT magnetic shield device according to a first aspect of the present invention includes a cathode ray tube housed in a housing such that a fluorescent surface is positioned in front of a display device, and disposed outside or inside four upper, lower, left, and right surfaces of the housing. And a current supply source for supplying a current to the compensation coil, wherein two of the four compensation coils arranged on the upper and lower surfaces of the housing are respectively connected to first to 4, the first to fourth winding portions all pass through the peripheral portion on the back side of the upper or lower surface of the housing, and extend in the depth direction of the first to fourth winding portions. Along the left and right peripheral portions of the upper surface or lower surface of the housing, the rear surface is configured to be sequentially different from the fluorescent surface, and two of the four compensation coils disposed on the left and right surfaces of the housing. Each of the compensation coils has a first to fourth windings The first to fourth winding portions all pass through the peripheral portion on the rear side of the housing left side surface or the right side surface, and the depth direction length of the first to fourth winding portions. Are configured so as to be sequentially different from the rear surface to the fluorescent surface along the upper and lower peripheral portions of the housing left side surface or the right side surface, respectively, and the current flowing from the current supply source to the four compensation coils is passed through the cathode ray tube. Adjusts to generate magnetic field lines with almost the same magnetic flux density in the direction opposite to the direction of the magnetic field lines of the incident external magnetic field in the depth direction, canceling the external magnetic field in the depth direction inside the cathode ray tube, and causing image fluctuation disturbance due to the external magnetic field in the depth direction. Is to be avoided.
A CRT magnetic shield device according to a second invention of the present application is a cathode-ray tube housed in a housing such that a fluorescent surface is positioned in front of a display device, and disposed opposite to each other outside or inside the top and bottom surfaces of the housing. Two compensation coils and a current supply source for supplying a current to the two compensation coils, each of the two compensation coils having a plurality of windings arranged along the periphery of the top or bottom surface of the housing. And a second winding continuous with the first winding and having a similar shape with the same center, small dimensions, and one-third the number of turns of the first winding. The current flowing from the current supply source to the two compensation coils is adjusted so as to generate magnetic force lines having substantially the same magnetic flux density in the direction opposite to the magnetic field lines of the external magnetic field in the vertical direction incident on the cathode ray tube. Up and down inside the CRT Offset the magnetic field, in which so as to avoid image shaking failure due vertical direction of the external magnetic field.
A CRT magnetic shield device according to a third aspect of the present invention is a cathode-ray tube housed in a housing such that a fluorescent surface is located in front of a display device, and is disposed on the outside or inside of the left and right sides of the housing. Provided, and a current supply source for supplying a current to the two compensation coils, and each of the two compensation coils is disposed along a peripheral edge of a left side surface or a right side surface of the housing, respectively. A first winding having a plurality of windings, a second winding continuing from the first winding, having a similar shape having the same center and small dimensions, and having a number of turns equal to 1/3 of the first winding; And adjusting the current flowing from the current supply source to the two compensation coils so as to generate magnetic force lines having substantially the same magnetic flux density in the direction opposite to the magnetic field lines of the external magnetic field in the horizontal direction incident on the cathode ray tube. Then left and right inside the CRT Offset the external magnetic field, in which so as to avoid image shaking failure due lateral direction of the external magnetic field.
[0008]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, a specific example illustrating an embodiment of the present invention will be described.
FIG. 1 is a schematic diagram illustrating a first embodiment of the present invention. The first embodiment is an example in which an image fluctuation disturbance due to an external magnetic field in the Z-axis direction perpendicular to the fluorescent surface is reduced. In the drawing, reference numeral 1 denotes a fluorescent screen (screen) of a CRT (not shown), 2 denotes a first compensation coil disposed on the upper surface of the CRT, and 3 and 4 denote input / output terminals of a current I of the first compensation coil 2. is there. Reference numeral 5 denotes a second compensation coil disposed on the left side surface of the cathode ray tube, and reference numerals 6 and 7 denote input / output terminals of the current I of the second compensation coil 5. Reference numeral 8 denotes a third compensation coil disposed on the bottom surface of the cathode ray tube, and reference numerals 9 and 10 denote input / output terminals of the current I of the third compensation coil 8. Reference numeral 11 denotes a fourth compensation coil disposed on the right side surface of the cathode ray tube, and reference numerals 12 and 13 denote input / output terminals of the current I of the fourth compensation coil 11. a is the maximum value of the outer width of the housing of the display device that accommodates the CRT, the length in the X-axis direction (left-right direction); b is the maximum value of the height of the housing that accommodates the CRT, and is the Y-axis direction (up and down). C) is the maximum value of the depth in the axial direction (front and rear) of the housing accommodating the cathode ray tube, and is the length in the Z-axis direction.
[0009]
In the first embodiment, the first to fourth compensating coils 2, 5, 8, and 11 are provided in opposite directions to cancel and cancel an external magnetic field in the Z-axis direction from a current supply source (not shown). The current I for generating the magnetic field Bz is passed to reduce the image fluctuation disturbance of the cathode ray tube. The current I is changed by manually operating a variable resistor or the like while observing the fluctuation state of the image, and the fluctuation is adjusted so as to minimize the fluctuation.
[0010]
As described above, the magnetic shield device of the present invention is not a conventional magnetic shield method that uses a shield plate or a container made of a magnetic material to block the incidence of the magnetic field lines of the external magnetic field. The shield effect is enhanced by generating an opposite magnetic field to cancel the incident magnetic flux.
[0011]
The first to fourth compensation coils 2, 5, 8, and 11 have substantially the same configuration, and the first compensation coil 2 includes a first winding ( The single winding or the multiple windings) has a depth and a width along the periphery of the upper surface of the housing accommodating the CRT, and a second winding following the first winding has the same width. The depth is 40% of the length of the first winding, and further successively the third winding is of the same width and the depth is about 25% of the length of the first winding; The next successive fourth winding has the same width and a depth of about 10% of the first winding and is connected to terminal 4. Actually, (0.38 to 0.42) c, (0.24 to 0.26) c, and (0.09 to 0.11) c are preferable.
In this manner, the compensation coil of the present invention makes the rear sides of the casings of the first to fourth windings substantially coincide with each other, and has the same width and a depth ratio of 20: 8: 5: It is configured to be 2.
[0012]
The compensation coils having such a shape are arranged on four sides (up, down, left, and right toward the screen) around the Z-axis direction (the direction of the depth) of the housing of the display device housing the cathode ray tube. Adjustment of the current strength between the terminals 3 and 4, 6 and 7, 9 and 10, and 12 and 13 of the four compensation coils 2, 5, 8, and 11 independently or in common. Although there is a current supply source having means, it is not shown. Actually, since the influence differs depending on the distance of the induction source from the substation, the current is adjusted while watching the screen to obtain an optimum value.
[0013]
FIG. 2 is an external perspective view of a television receiver showing a specific example of the first embodiment of FIG.
For example, when an external magnetic field of 10 μT acts on the 21-inch television in the Z-axis direction (depth direction) to cause image fluctuation, the maximum values a, b, and c of width, height, and depth are each about 50 cm. The first to fourth compensation coils 2, 5, 8, and 11 each having a single winding are arranged along the periphery of the housing, and a current I of 4.5 A is supplied to each of the coils to reduce image fluctuation disturbance. I was able to. For example, if the number of turns is two, the current may be a half, that is, 2.25A.
[0014]
FIG. 3 is a schematic diagram for explaining a second embodiment of the present invention, and is an example in which an image fluctuation disturbance due to an external magnetic field in the vertical direction, that is, in the Y-axis direction of a housing accommodating a CRT is reduced. In the figure, the maximum values a, b, and c of the lengths of the sides of the screen 1 and the housing of the CRT are the same as in the first embodiment of FIG. Reference numeral 21 denotes a fifth compensation coil disposed on the top surface of the housing, and reference numeral 22 denotes a sixth compensation coil disposed on the bottom surface of the housing.
[0015]
The fifth and sixth compensation coils 21 and 22 have substantially the same configuration, and have a plurality of first windings (large coil) along the periphery of the top and bottom surfaces of the housing that houses the CRT. ) And successively, a similar shape having the same center and a depth of about 80% of the large coil and a width of about 80% of the large coil, and one third of the first winding. And a second winding (small coil) having a number.
That is, concentric compensating coils 21.22 composed of a large coil and a small coil having a turn ratio of 3: 1 are arranged opposite to the upper and lower surfaces of a housing accommodating a CRT, and a current flows through the compensating coils. , A magnetic field By which is opposite to the external magnetic field in the vertical direction.
[0016]
For example, when an external magnetic field of 10 μT acts in the Y-axis direction (vertical direction) of a 21-inch television having the same size as that of the specific example of the first embodiment described above, and the image fluctuates, three turns are required. A fifth compensating coil 21 and a sixth compensating coil 22 each composed of a large coil and a small coil wound once are opposed to each other on the upper and lower surfaces, and a current I of 1.7 A is applied to each of them so as to reduce image fluctuation disturbance. We were able to. Also in this case, if the number of turns is six and two, the current may be 0.85 A, which is a half.
[0017]
FIG. 4 is a schematic diagram for explaining a third embodiment of the present invention, and is an example in which an image fluctuation obstruction caused by an external magnetic field in the left-right direction, that is, the X-axis direction of a housing accommodating a CRT is reduced. In the figure, the maximum values a, b, and c of the lengths of the sides of the screen 1 and the housing of the CRT are the same as in the first embodiment of FIG. Reference numeral 23 denotes a seventh compensation coil disposed on the right side of the housing, and reference numeral 24 denotes an eighth compensation coil disposed on the left side of the housing.
[0018]
The seventh and eighth compensation coils 23 and 24 have substantially the same configuration, and have a plurality of first windings (large coils) along the peripheral edge of the side surface of the housing that houses the CRT. , Successively, with the same center, a height of about 80% of the large coil, a depth of about 80% of the large coil, a similar shape, and one-third the number of turns of the first winding It is formed with the second winding (small coil).
That is, a compensation coil 23.24 composed of a large coil and a small coil having the same center and a turn ratio of 3: 1 is disposed opposite to the left and right surfaces of the housing containing the cathode ray tube, and a current is supplied to the compensation coil. And a magnetic field Bx in the opposite direction to the left and right external magnetic field is generated and canceled.
[0019]
FIG. 5 is an external perspective view of a television receiver showing a specific example of the third embodiment of the present invention.
For example, when an external magnetic field of 10 μT acts in the X-axis direction (left-right direction) of a 21-inch television, which is the same as the specific example of the first embodiment and the above-described embodiment, a large three-turn coil is used. A seventh compensating coil 23 and an eighth compensating coil 24 each composed of a small coil wound once are disposed on the left and right sides to face each other, and a current I of 1.5 A is applied to each of them to reduce the image fluctuation disturbance. did it. Also in this case, if the number of turns is 6 turns and 2 turns, the current may be reduced to half, that is, 0.75A.
[0020]
It is needless to say that the above-described CRT magnetic shield device of the present invention adjusts the current flowing through the compensating coil in accordance with the change in the magnetic flux density of the external magnetic field. An external magnetic field can be canceled out, and if any two embodiments are implemented, a two-dimensional external magnetic field can be canceled out. Therefore, for a three-dimensional external magnetic field, by arranging a plurality of the compensation coils of the first to third embodiments and operating them at the same time, the image of the cathode ray tube due to the external magnetic fields having different magnetic flux densities in all directions is obtained. Clearly, the sway obstacle can be avoided.
[0021]
Furthermore, the magnetic shield device for a cathode ray tube of the present invention can be installed along the shape of the outer box of the display device that accommodates the cathode ray tube, and two or four components arranged on two or four sides on the exterior or inside of the housing. Since it is not necessary to connect two compensating coils to one, it is possible to avoid the image fluctuation disturbance of the CRT without being noticeable in appearance.
[0022]
【The invention's effect】
As described above, by practicing the present invention, it is possible to perform a simple operation without disturbing the external shape of a display device such as a television and without being restricted by the magnetic flux density and direction of an external magnetic field incident on a cathode ray tube. With the structure, it is possible to avoid the image fluctuation disturbance of the cathode ray tube due to the external magnetic field, so that there is an extremely excellent effect in practical use.
[Brief description of the drawings]
FIG. 1 is a schematic diagram illustrating a first embodiment of the present invention.
FIG. 2 is an external view showing a specific example of the first embodiment of the present invention.
FIG. 3 is a schematic diagram illustrating a second embodiment of the present invention.
FIG. 4 is a schematic diagram illustrating a third embodiment of the present invention.
FIG. 5 is an external view showing a specific example of a third embodiment of the present invention.
[Explanation of symbols]
1 Screen 2, 5, 8, 11 Compensation coil 3, 4, 6, 7, 9, 10, 12, 13 Current input / output terminal a Maximum value of the length (width) in the Z-axis direction of the housing containing the cathode ray tube b Maximum value of the length (height) in the Y-axis direction of the housing accommodating the CRT c Maximum value of the length (depth) in the X-axis direction of the housing accommodating the CRT I Current Bz External magnetic field in the Z-axis direction Magnetic fields 21 and 22 generated from the compensation coil that cancels the magnetic field Compensation coil By The magnetic fields 23 and 24 generated from the compensation coil that cancels the external magnetic field in the Y-axis direction Compensation coil Bx The magnetic field generated from the compensation coil that cancels the external magnetic field in the X-axis direction

Claims (3)

A cathode-ray tube housed in a housing such that a fluorescent surface is located in front of the display device, a compensation coil disposed outside or inside the four sides of the housing, and a current flowing through the compensation coil With a source,
Of the four compensation coils, each of the two compensation coils arranged on the upper and lower surfaces of the housing is formed of continuous first to fourth winding portions, and the first to fourth winding portions are All pass through the peripheral portion on the rear side of the upper surface or lower surface of the housing, and the length in the depth direction of the first to fourth winding portions is along the left or right peripheral portion of the upper surface or lower surface of the housing, from the rear side. It is configured so that it sequentially changes to the fluorescent surface,
Of the four compensation coils, each of the two compensation coils arranged on the left and right surfaces of the housing is formed of continuous first to fourth winding portions, and the first to fourth winding portions are All pass through the peripheral portion on the back side of the housing left side or right side, and the length in the depth direction of the first to fourth winding portions is along the upper and lower peripheral portions of the housing left side or right side. , Is configured to be sequentially different from the back side to the fluorescent surface,
The current flowing from the current supply source to the four compensation coils is adjusted so as to generate magnetic field lines having almost the same magnetic flux density in the direction opposite to the direction of the magnetic field lines of the external magnetic field in the depth direction incident on the cathode ray tube, and A magnetic shield device for a cathode ray tube, wherein an external magnetic field in a direction is canceled to prevent image fluctuation disturbance due to an external magnetic field in a depth direction . A cathode-ray tube housed in a housing such that a fluorescent surface is located in front of the display device, two compensation coils disposed to face outside or inside the top and bottom surfaces of the housing , and two compensation coils. A current supply source for flowing a current,
Each of the two compensation coils has a first winding having a plurality of turns arranged along a peripheral edge of a top surface or a bottom surface of the housing, and a plurality of first windings having the same size as the first winding and having the same center. Is formed of a small analogous shape, the number of turns is 1/3 of the first winding and a second winding,
The current flowing from the current supply source to the two compensation coils is adjusted so as to generate magnetic field lines having almost the same magnetic flux density in the direction opposite to the magnetic field lines of the external magnetic field in the vertical direction incident on the cathode ray tube, and A magnetic shield device for a cathode ray tube, wherein an external magnetic field in a vertical direction is canceled out to prevent image fluctuation disturbance due to an external magnetic field in a vertical direction . A cathode-ray tube housed in a housing such that a fluorescent surface is located in front of the display device, two compensation coils disposed outside or inside the left and right side surfaces of the housing , and two compensation coils. A current supply source for flowing a current,
Each of the two compensation coils has a first winding having a plurality of turns arranged along the periphery of the left side surface or the right side surface of the housing, and a center which is continuous with the first winding and has the same center. Formed with a second winding having a small size and a similar number of turns and one third of the number of the first winding;
The current flowing from the current supply source to the two compensating coils is adjusted so as to generate magnetic lines of force having substantially the same magnetic flux density in a direction opposite to that of the magnetic field lines of the external magnetic field in the left and right directions incident on the cathode ray tube. A magnetic shield device for a cathode ray tube, wherein the external magnetic field in the horizontal direction is canceled out to prevent image fluctuation disturbance due to the external magnetic field in the horizontal direction .

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