Deflection yoke

Details Deflection yoke Deflection yoke

2001-03-02

2004-08-24

Lee, Michael H. (Department: 2614)

Television

Video display

Cathode-ray tube

C335S213000, C313S440000

Reexamination Certificate

active

06781639

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a deflection yoke utilized for a picture displaying apparatus such as a television receiver and a displaying device, which is equipped with a color picture tube, particularly, relates to a deflection yoke being improved on a saddle shaped horizontal deflection coil.
2. Description of the Related Art
In a picture displaying apparatus utilizing a color picture tube of an inline three electron gun type, there existed one method, which utilizes a deflection yoke of self-convergence system, out of several methods for converging three electron beams emitted from three electron guns on a screen or a picture excellently. Such a deflection yoke of self-convergence system is usually composed of a pair of upper and lower saddle shaped horizontal deflection coils and a pair of right and left saddle shaped vertical deflection coils, and then an excellent convergence characteristic can be obtained.
However, a deflection yoke, which was generally mass-produced, generates miss-convergence by reason of scattering of a characteristic of a horizontal or vertical deflection coil and by reason of shifting of a coil allocation when the coil is installed. Accordingly, convergence of almost all deflection coils is adjusted by installing a magnetic piece on an adequate position of a coil, or compensated by a correction circuit.
FIGS.
5
(
a
) and
5
(
b
) show statuses of horizontal deflection magnetic fields unbalanced in right and left.
FIGS.
6
(
a
) and
6
(
b
) show miss-convergence patterns, which generate when a magnetic field is in the statuses shown in FIGS.
5
(
a
) and
5
(
b
). Further, FIGS.
5
(
a
) and
5
(
b
) are cross sectional views of a neck portion
100
of a color picture tube with viewing from a screen side of the color picture tube. In FIGS.
5
(
a
) and
5
(
b
), circled letters “R”, “G”, and “B” represent a cross section of an electron beam of red, green, and blue respectively, curves in a broken line represent magnetic fields, and an arrow “X” represents the horizontal direction of the screen. In FIGS.
6
(
a
) and
6
(
b
), letters “R” and “B” show bright lines drawn by the “R” and “B” electron beams respectively.
As shown in FIG.
5
(
a
), when a distribution of horizontal deflection magnetic field is unbalanced in right and left, in other words, when a pin cushion of magnetic field for the “R” beam is strengthened and a pin cushion of magnetic field for the “B” beam is weakened, a miss-convergence happens such that a bright line of the “R” shown in a solid line is allocated outside a bright line of the “B” shown in a broken line in both the edge areas of the screen in the horizontal direction as shown in FIG.
6
(
a
). On the other hand, as shown in FIG.
5
(
b
), when a pin cushion of magnetic field for the “R” beam is weakened and a pin cushion of magnetic field for the “B” beam is strengthened, a miss-convergence happens such that a bright line of the “R” shown in a solid line is allocated inside a bright line of the “B” shown in a broken line in both the edge areas of the screen in the horizontal direction as shown in FIG.
6
(
b
). Such a miss-convergence is called an H-shift miss-convergence.
FIG. 7
is a perspective view of a deflection coil utilized for a deflection yoke of the prior art.
In order to compensate such the miss-convergence mentioned above in a deflection yoke, as shown in
FIG. 7
, a magnetic piece
26
is allocated on an end surface (toward an electron gun) of each smaller diameter flange
20
A (toward an end of neck of a color picture tube) of each horizontal deflection coils
20
. It is not mentioned that the magnetic piece
26
is directly adhered on the end surface of each small diameter flange
2
A. Generally, the magnetic piece
26
is mounted on a separator. In a case that a magnetic field affecting the “R” beam is strong as shown in FIG.
5
(
a
), the magnetic piece
26
is allocated on the left side of the end surface of the smaller diameter flange
20
A with viewing from the smaller diameter flange
20
A side as shown in FIG.
7
. The magnetic piece
26
is magnetized by a magnetic field generated by the smaller diameter flange
20
A. Accordingly, the magnetic piece
26
generates a magnetic field of compensating the H-shift miss-convergence.
With referring to
FIG. 8
, an effect of the magnetic piece
26
will be explained.
FIG. 8
is a cross sectional view of a neck portion
100
of a color picture tube with viewing from a screen side of the color picture tube. In
FIG. 8
, circled letters “R”, “G”, and “B” represent a cross section of an electron beam of red, green, and blue respectively, curves in a broken line represent magnetic fields, and an arrows “X” and “Y” represent the horizontal direction and the vertical direction of the screen respectively. In a case of being deflected toward the left side of the screen, for example, a direction of current flowing through the smaller diameter flange
20
A of the horizontal deflection coil
20
is shown by an arrow
210
. The magnetic piece
26
, which is allocated closer to the electron gun than the smaller diameter flange
20
A, is magnetized with being oriented to an arrow
230
by a magnetic field generated by the smaller diameter flange
20
A within a range of broken line
220
.
A magnetic field generated by the magnetic piece
26
, as a result of being magnetized, is oriented toward a direction of canceling a main deflection magnetic field generated by the horizontal deflection coil
20
, that is, toward a direction of weakening the magnetic field in the right side of the neck portion
100
and unbalanced magnetic field in right and left is solved. Accordingly, the magnetic piece
26
is magnetized by the magnetic field in the “Y” direction generated by the smaller diameter flange
20
A, and then the H-shift miss-convergence is compensated by the magnetic field generated by the magnetic piece
26
being magnetized.
A degree of influence on a convergence characteristic caused by variations of the horizontal deflection coil
20
and dislocation of the horizontal deflection coil
20
during installation is increasing in response to recent trend toward a larger screen of a displaying device. Further, demand for decreasing a deflection power of a deflection yoke is increasing for the purpose of power saving of a displaying device. In order to match the trend and demand, as disclosed in the Japanese Patent Laid-open Publication No. 8-153477, for example, the smaller diameter flange
20
A of the horizontal deflection coil
20
tends to be miniaturized. The magnetic field of the smaller diameter flange
20
A, which magnetizes the magnetic piece
26
, decreases as a result of a miniaturized smaller diameter flange. Accordingly, an effect of compensating the H-shift miss-convergence is deteriorated.
In order to increase the effect of compensating the H-shift miss-convergence, dimensions of the magnetic piece
26
shall be enlarged. However, the magnetic piece
26
is generally made of formed ferrite, so that a manufacturing cost of the magnetic piece
26
increases if the dimension is enlarged. Further, since a coil for compensating coma is mounted on a smaller diameter flange of a separator for a deflection yoke and some components such as a fastening band for fastening a cylindrical neck portion provided on the smaller diameter flange to a neck portion of a color picture tube are mounted on the cylindrical neck portion, enlarging the dimensions of the magnetic piece
26
is inevitably limited by a mounting construction and a mounting allocation.
SUMMARY OF THE INVENTION
Accordingly, in consideration of the above-mentioned problems of the prior art, an object of the present invention is to provide a deflection yoke, which can effectively compensate the H-shift miss-convergence without enlarging dimensions of a magnetic piece for compensating the H-shift miss-convergence.
In order to achieve the above object, the present invention provides, according to an aspect thereof, a deflection yoke being mounted on a

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