Deflection system

A deflection system for a cathode-ray tube including a horizontal deflection core, a magnetic coil, and a vertical deflection coil toroidally wound on the magnetic core. The vertical deflection coil has a plurality of superimposed winding layers arranged with respect to a vertical axis of the deflection system with at least one of the layers of the vertical deflection coil being disposed asymmetrically with respect to the vertical axis or disposed symmetrically with respect to the vertical axis and having winding portions delimiting at least one gap along an extent thereof at a position other than the vertical axis. In this manner, an induced voltage in the at least one of the layers is substantially equal to an induced voltage in each of another of the layers at least in the region of the vertical axis, whereby ringing is substantially prevented.

BACKGROUND OF THE INVENTION 
The present invention relates to a deflection system for a cathode-ray 
tube, particularly to a deflection system for enabling a decrease of 
ringing. 
According to conventional devices of this type, as described in Japanese 
Patent Laid Open No. 34549/83, first and second resistors are respectively 
connected between a central connection point of a deflecting coil wound in 
a toroidal fashion around a core between winding start and end points of 
the coil, and the resonance of a resonance circuit formed by a deflection 
system and a floating capacity induced between lines of winding layers of 
the toroidally wound deflecting coil is damped to reduce ringing which 
causes light and dark stripes in a reproduced image reproduced on a 
cathode-ray tube simultaneously with the above resonance. 
Referring to FIG. 1, there is illustrated a conventional winding method for 
a conventional vertical deflecting coil, in which the ordinate represents 
the number of each winding layer, while the abscissa represents the angle 
.theta. of each winding. In the figure, 1 represents a first layer, a 
second layer, 2 . . . and 5 a fifth layer. A vertical axis 6 extends 
through the center of the vertical deflecting coil. According to the 
winding method shown in FIG. 1, the winding for layer 1 starts from a 
winding start point 10 at a -70.degree. point and ends at +70.degree. 
point with return being made to the -70.degree. point using a return line 
12 (indicated by a dotted line). The second-layer 2 winding starts from 
the -70.degree. point and ends at the +70.degree. point with a return 
being made to a -50.degree. point. Then a third-layer 3 winding starts 
from the -50.degree. point and ends at the +50.degree. point, with return 
being made to the -50.degree. point. The fourth-layer 4 winding also 
starts from the -50.degree. point and ends at the +50.degree. point with 
return being made to a -30.degree. point; and a fifth-layer 5 winding 
starts from the 30.degree. point and ends at a winding end point 14 at a 
+30.degree. point. Thus, in the winding method shown in FIG. 1, all the 
winding layers are approximately symmetric with respect to the vertical 
axis 6. 
FIG. 2 illustrates the distribution of induced voltages from a horizontal 
deflecting coil relative to the vertical deflecting coil wound according 
to the winding method shown in FIG. 1. In FIG. 2, a normalized induced 
voltage distribution curve of the first and second layers 1 and 2 exhibits 
an increase from 0.degree. at the -70.degree. point with respect to the 
vertical axis 6 and reaches a maximum at the 0.degree. point, and after 
passing the 0.degree. point, exhibits a decrease until becoming 0.degree. 
at +70.degree. point. The reason why a change is made from increase to 
decrease at the 0.degree. point is because the voltage induced in the coil 
of a small number of windings is inverted in polarity between positive and 
negative sides of angle .theta. with respect to 0.degree. as a boundary. 
An induced voltage distribution of the third and fourth layers 3 and 4 
increases from 0.degree. at the -50.degree. point and reaches a maximum at 
the 0.degree. point, then after passing the 0.degree. point, it decreases 
until it becomes 0.degree. at the +50.degree. point. The induced voltage 
distribution of the fifth layer 5 increases from 0.degree. at the 
-30.degree. point and reaches a maximum at the 0.degree. point, then after 
passing the 0.degree. point, it decreases until it becomes 0.degree. at 
the +30.degree. point. 
In FIG. 2, the induced voltage at the winding start point of the coil is 
assumed to be 0.degree. and differences are developed in the following 
relation among the induced voltage of the first and second layers, induced 
voltage of the third and fourth layers, and induced voltage of the fifth 
layer: (1st and 2nd layer induced voltage)&gt;(3rd and 4th layer induced 
voltage)&gt;(5th layer induced voltage). This relation is valid on the 
condition that the winding pitch (rad/turn) is constant and that all the 
winding layers are approximately symmetric with respect to the vertical 
axis 6. 
In the winding method shown in FIG. 1, as mentioned above, there is 
developed a voltage difference of [(1st and 2nd layer induced 
voltage)-(3rd and 4th layer induced voltage)], i.e., an inter-layer 
voltage difference 8. 
On the other hand, FIG. 3 is an electrical equivalent circuit diagram of a 
deflection system related to a ringing phenomenon which ringing is 
generated in the deflection system. In FIG. 3, there is shown a deflection 
system 1 including a horizontal deflection coil 2 supplied with power from 
a horizontal deflection circuit 2' and a vertical deflection coil 3 
magnetically coupled with the horizontal deflection coil. Only half of the 
upper and lower portions of the vertical deflection coil is illustrated in 
FIG. 3, and a connection circuit to a vertical deflection circuit is 
omitted because it has nothing to do with the occurrence of ringing. The 
vertical deflection coil 3 is divided into a negative-side coil 3a and a 
positive-side coil 3b, with angle .theta., on both sides of the vertical 
axis 6. The coils 3a and 3b are magnetically coupled to the horizontal 
deflection coil 2 (supplied with electric power from the horizontal 
deflection circuit 2') so as to be opposite in polarity to each other. 
Since the winding layers of the vertical deflecting coil 3 are stacked 
successively, an inter-layer floating capacity 9 is present between 
adjacent winding layers. Between the winding layers which are different in 
winding start angle from each other, there occurs the inter-layer 
potential difference 8 corresponding to only an induced voltage which 
varies in such angular range. Consequently, a voltage corresponding to the 
inter-layer potential difference 8 is developed relative to the 
inter-layer floating capacity 9 developed between adjacent winding layers 
of the vertical deflecting coil 3, thus causing resonance, and hence the 
occurrence of ringing. As to the ringing phenomenon generated in the 
deflection system, ringing caused by the inter-layer floating capacity 9 
of the vertical deflection coil is more predominant than ringing caused by 
an inter-line floating capacity of the winding layers. Heretofore, no 
consideration has been given to decreasing the ringing caused by the 
inter-layer floating capacity 9. Additionally, a satisfactory ringing 
diminishing effect is not obtained in the case of a high horizontal 
deflection frequency. In the prior art, moreover, since a damping resistor 
is used, the working efficiency is poor and the manufacturing cost 
increases. 
SUMMARY OF THE INVENTION 
It is the object of the present invention to provide a deflection system 
for reducing an inter-layer potential difference of the voltage induced in 
a vertical deflection coil by a horizontal deflection magnetic field, and 
thereby diminish ringing without using a damping resistor. 
According to a feature of the present invention, there is provided a 
deflection system having a vertical deflection coil wound in a toroidal 
fashion, the vertical deflection coil having at least one winding layer 
which is asymmetric in winding density distribution with respect to an 
axis of symmetry, a winding end position of the at least one winding layer 
and a winding start position of the adjacent winding layer being 
approximately symmetric with respect to the axis of symmetry. 
According to another feature of the present invention, a deflection system 
has a vertical deflection coil wound in a toroidal form approximately 
symmetrically with respect to an axis of symmetry, wherein the vertical 
deflecting coil has at least one winding layer including a hollow portion 
not containing the axis of symmetry. 
By the formation of a winding layer which is asymmetric with respect to the 
axis of symmetry or by the formation of a winding layer which has a hollow 
portion not containing the axis of symmetry, there can be realized a 
winding distribution which diminishes an inter-layer potential difference 
of voltage induced in the vertical deflection coil by a horizontal 
deflection magnetic field of high frequency, whereby the resonance caused 
by an inter-layer floating capacity can be prevented and therewith obtain 
a reduction of ringing. 
These and further objects, features and advantages of the present invention 
will become more obvious from the following description when taken in 
connection with the accompanying drawings which show for purposes of 
illustration only, several embodiments in accordance with the present 
invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS 
FIG. 4 illustrates an embodiment of the present invention, in which FIG. 
4(a) is a perspective view, FIG. 4(b) is a front view of a principal 
portion and FIG. 4(c) is an explanatory view of a winding method. In these 
figures, there is shown a deflection system 1 for a cathode ray tube 16 
(shown in dashed line), a horizontal deflection coil 2 and a vertical 
deflection coil 3, a magnetic core 4 formed of a magnetic material, and a 
separator 5 formed of an insulating material. The vertical axis 6 passes 
through the center of the vertical deflection coil 3. There is also shown 
a winding start position 10, a winding return line 12, and a winding end 
position 14. 
As shown in FIG. 4(a), the deflection system 1 includes the horizontal 
deflection coil 2 which is in the shape of a saddle, the vertical 
deflection coil 3 which is wound in a toroidal form on the magnetic core 
4, and the separator 5. When the angle to the vertical axis 6 is .theta. 
as shown in FIG. 4(b), the winding method for the vertical deflection coil 
3 is set as shown in FIG. 4(c) In FIG. 4(c), 1 represents a first winding 
layer of the deflection coil, 2 represents a second winding layer, . . . 
and 6 to a sixth winding layer. The first winding layer starts from the 
vertical axis 6 and ends at a +70.degree. point and then shifts by one of 
the return lines 12 to a -70.degree. point. The second layer starts from 
the -70.degree. point and ends at the +70.degree. point with return being 
made to the -70.degree. point. The third layer starts from the -70.degree. 
point and ends at a +50.degree. point with return being made to a 
-50.degree. point. The fourth layer starts from the -50.degree. point and 
ends at the +50.degree. point with return being made to the and ends at a 
+30.degree. point with return being made to a -30.degree. point, and the 
sixth layer starts from the - 30.degree. point and ends at a 0.degree. 
point, i.e., the vertical axis 6. In the vertical deflection coil 3 which 
is wound on the magnetic core 4, the winding layers are stacked or 
superimposed on the core 4 successively in the order of the winding. A 
winding density distribution (turn/.degree.) in the entire vertical 
deflection coil of FIG. 4(c) which influences the shape of a magnetic 
field created and the performance of the deflecting system 1 is symmetric 
with respect to the vertical axis 6, as shown in FIG. 5. 
As described above, a winding layer asymmetric relative to the vertical 
axis 6 is formed, and a winding end position of this winding layer and a 
winding start position of the next winding layer are symmetric with 
respect to the vertical axis 6. This symmetric relation is expressed as 
follows: 
EQU .theta.2, i=-.theta.1, i+l (1) 
where 
.theta.2, i: winding end angle of the 1th layer, 
.theta.1, i+1: winding start angle of the i+1th layer. 
On the other hand, the voltage, Ei, induced in the 1th layer of the 
vertical deflection coil by a horizontal deflection magnetic field can be 
approximated by the following equation because the interlinkage magnetic 
flux density of the horizontal deflection magnetic field for one turn of 
the coil positioned at the angle .theta. is substantially proportional ti 
sin .theta.: 
##EQU1## 
where, E.sub.1, i: winding start potential of the 1th layer, 
ni(.theta.): winding density distribution of the 1th layer (turn/rad), 
K1: constant, 
K.sub.2 : constant (constant winding pitch without hollow portion), 
.theta.1,i: winding start angle of the 1th layer. 
FIG. 6 illustrates a distribution of normalized values obtained by dividing 
induced voltages in the vertical deflection coil by K2. If the induced 
voltage at the start of winding in the normalized induced voltage 
distribution curve in FIG. 6 is 0, the induced voltage of the first layer 
decreases from 0 because a winding starts from the vertical axis 6 and 
becomes minimum (-0.66) at a +70.degree. point with return being made to a 
-70.degree. point. The induced voltage of the second layer increases from 
the -70.degree. point and becomes a maximum (0) at a 0.degree. point, and 
after passing the 0.degree. point, it decreases until reaching a minimum 
(31 0.66) at the +70.degree. point with return being made to -70.degree. 
point. The induced voltage of the third layer increases from the 
-70.degree. point and becomes the maximum (0) at the 0.degree. point, then 
after passing the 0.degree. point, it decreases until reaching a minimum 
(-0.36) at a +50.degree. point and return being made to a -50.degree. 
point. The induced voltage of the fourth layer increases from the 
-50.degree. point and becomes the maximum (0) at the 0.degree. point, and 
after passing the 0.degree. point, it decreases until reaching the minimum 
(-0.36) at the +50.degree. point with return being made to a -50.degree. 
point. The induced voltage of the fifth layer increases from the 
-50.degree. point and becomes the maximum (0) at the 0.degree. point, and 
after passing the 0.degree. point, it decreases until reaching a minimum 
(-0.13) at a +30.degree. point with return being made to a -30.degree. 
point. The induced voltage of the sixth layer increases from the 
-30.degree. point and becomes the maximum the (0) at the 0.degree. point. 
Thus, the induced voltage curves of the winding layers overlap each other 
as a single curve, as shown in FIG. 6, and the inter-layer potential 
difference 8 is 0. Therefore, resonance does not occur, even in the 
presence of an inter-layer floating capacity 9, whereby ringing can be 
diminished. 
Another embodiment of the present invention is illustrated in FIG. 7, which 
is an explanatory view of a winding method for the vertical deflection 
coil 3. In FIG. 7, hollow portion feed line 13 connects winding portions 
of the layer delimiting a hollow portion 11 of the winding layer. The 
entire vertical deflecting coil in this embodiment is formed so that a 
winding density distribution is symmetric with respect to a vertical line 
(.theta.=0.degree.), and with the hollow portion 11 being formed, as shown 
in FIG. 8. According to the winding method of this embodiment, as shown in 
FIG. 7, the first layer starts from a -40.degree. point with respect to 
the vertical axis 6 and ends a +70.degree. point with return being made to 
a -70.degree. point. The second layer starts from the -70.degree. point, 
passes the 0.degree. point and ends at the +70.degree. point with return 
being made to the -70.degree. point. The third layer starts from the 
-70.degree. point and ends at a +60.degree. point with return being made 
to a -60.degree. point. The fourth layer starts from the -60.degree. point 
and ends at a +60.degree. point with return being made to the -60.degree. 
point. The fifth layer includes a winding portion starting from the 
-60.degree. point and ending at a -10.degree. point, which portion is 
connected by the hollow portion feed line 13 to a +10.degree. point so 
that a hollow portion is provided from the 31 10.degree. point to the 
+10.degree. point. Then another winding portion of the fifth layer starts 
from the +10.degree. point and ends at the +50.degree. point with return 
being made to a -50.degree. point. The sixth layer includes a winding 
portion starting from the -50.degree. point and ending at a -20.degree. 
point which is then fed up to a +20.degree. point so that a hollow portion 
is provided from the -20.degree. point to a +20.degree. point with another 
winding portion of the sixth layer starting from the +20.degree. point and 
ending at a +40.degree. point. Thus, a winding end position of one winding 
layer and a winding start position of the next winding layer are 
approximately symmetric with respect to the vertical axis and the first, 
third, fifth and sixth winding layers are asymmetric with respect to the 
vertical axis 6. 
FIG. 9 shows a distribution of normalized values obtained by dividing 
induced voltages Ei by K2, shown in the foregoing equation (2), for the 
winding of FIG. 7. According to a distribution curve of the normalized 
induced voltages shown in FIG. 9, if the induced voltage at the start of 
winding is 0, the induced voltage of the first layer increases from 0 at a 
-40.degree. point with respect to the vertical axis and becomes a maximum 
at a 0.degree. point, and after passing the 0.degree. point, it decreases 
and becomes minimum at a +70.degree. point with return being made to a 
-70.degree. point. The induced voltage of the second layer increases from 
the -70.degree. point and becomes a maximum at the 0.degree. point, and 
after passing the 0.degree. point, it decreases and becomes a minimum at 
+70.degree. point. The induced voltage of the third layer increases from 
the -70.degree. point and becomes a maximum at the 0.degree. point and 
after passing the 0.degree. point, it decreases and becomes a minimum at a 
+60.degree. point. The induced voltage of the fourth layer increases from 
the -60.degree. point and becomes a maximum at the 0.degree. point, and 
after passing the 0.degree. point, it decreases and becomes a minimum at 
the +60.degree. point. The induced voltage of the fifth layer increases 
from the -60.degree. point and becomes a maximum at a -10.degree. point 
and the voltage is maintained up to the +10.degree. point, from which 
point it decreases, and becomes a minimum at a +50.degree. point. The 
induced voltage of the sixth layer increases from a -50.degree. point and 
becomes maximum at a -20.degree. point, and the voltage is maintained up 
to a +20.degree. point, from which point it decreases, and becomes a 
minimum at a +40.degree. point. As shown in FIG. 9, the inter-layer 
potential difference becomes 0 and resonance does not occur, even in the 
presence of the inter-layer floating capacity as 9 shown in FIG. 3, so it 
is possible to diminish ringing. 
A further embodiment of the present invention is illustrated in FIG. 10, 
which is an explanatory view of another winding method for the vertical 
deflection coil 3. In the figure, the first winding layer includes a 
portion starting from a -70.degree. point with respect to the vertical 
axis 6 and ending at a -65.3.degree. point which winding portion is then 
fed from the -65.3.degree. point up to a -50.degree. point so as to 
provide a hollow portion between the points -65.3.degree. and -50.degree.. 
Another winding portion of the first layer starts from the -50.degree. 
point and ends at a +50.degree. point, which winding portion is then fed 
from the +50.degree. point up to a 65.3.degree. point so that a hollow 
portion is provided between the points +50.degree. and +65.30. A further 
winding portion of the first layer starts from +65.30 point and ends at a 
+70.degree. point return being made to -70.degree. point. The second layer 
is wound in the same way as in the first layer. The third layer includes 
portion starting from the -65.3.degree. point and ending at a 
-44.2.degree. point, which winding portion is fed from the -44.2.degree. 
point to a -30.degree. point so that a hollow portion is provided between 
the points -44.2.degree. and -30.degree.. Another winding portion of the 
third layer starts from the -30.degree. point and ends at a +30.degree. 
point, which portion is then fed from the +30.degree. point to the 
+44.2.degree. point so that a hollow portion is provided between the 
points +30.degree. and +44.2.degree.. A further winding portion of the 
third layer starts from a +44.2.degree. point and ends at a +65.3.degree. 
point with return being made to the -65.3.degree. point. The fourth layer 
includes a winding portion starting from the -65.3.degree. point and 
ending at a -55.5.degree. point, which portion is fed from the 
-55.5.degree. point to a -44.2.degree. point so that a hollow portion is 
provided between the points -55.5.degree. and -44.2.degree.. Another 
winding portion of the fourth layer starts from the -44.2.degree. point 
and ends at +44.2.degree. point, which portion is fed from the 
+44.2.degree. point to the +55.5.degree. point so that a hollow portion is 
provided between the points +44.2.degree. and +55.5.degree.. A further 
winding portion of the fourth layer starts from the +55.5.degree. point 
and ends at a +65.3.degree. point with return being made to the 
-55.5.degree. point. The fifth layer starts from the -55.5.degree. point 
and ends at the +55.5.degree. point. 
In the entirety of the vertical deflection coil in this embodiment of FIG. 
10, the winding density distribution is symmetric with respect to the 
vertical axis 6, in a manner as shown in FIG. 5. According to the winding 
method of this embodiment, the winding layers are weighted in induced 
voltage so that the winding layers are of the same potential in the 
vicinity of 0.degree. as .theta., to keep the balance of turns. To this 
end, the winding density distribution is characterized by at least one 
winding layer having a hollow portion formed in a position not containing 
the vertical axis 6. As a result, normalized values obtained by dividing 
the induced voltage Ei by K2, shown in the foregoing equation (2), are 
distributed as shown in FIG. 11. In the distribution curve of normalized 
induced voltages shown in FIG. 11, if the induced voltage at the start of 
winding is assumed to be 0, since the winding starts from the -70.degree. 
point with respect to the vertical axis 6, the induced voltage of the 
first layer increases from 0 at the -70.degree. point and becomes 0.08 at 
-65.3.degree. and then the voltage remains as it is up to the -50.degree. 
point. The voltage then increases from the -50.degree. point and becomes a 
maximum (0.43) at the 0.degree. point and after passing the 0.degree. 
point, it decreases. Then at the +50.degree. point, the voltage becomes 
0.08, and from the +50.degree. point to the +65.3 point, the voltage 
remains as it is since a hollow portion is provided between the two 
points. Then from +65.3.degree. point, the voltage decreases and becomes a 
minimum (0) at the +70.degree. point. The induced voltage curve of the 
second layer is the same as that of the first layer. 
The induced voltage of the third layer increases from the -65.3.degree. 
point and becomes 0.30 at the -44.2.degree. point. Then from the 
-44.2.degree. point to the -30.degree. point, the voltage does not change 
since a hollow portion is provided between the two points. Then the 
voltage increases from the -30.degree. point and becomes a maximum (0.43) 
at the 0.degree. point, and after passing the 0.degree. point, the voltage 
decreases and becomes 0.30 at the +30.degree. point. Then from the 
+30.degree. point to the +44.2.degree. point, the voltage does not change 
since a hollow portion is provided between the two points. Then from the 
+44.2.degree. point the voltage further decreases and becomes a minimum at 
the +65.3.degree. point. 
The induced voltage of the fourth layer increases from the -65.3.degree. 
point and becomes 0.15 at the -55.5.degree. point. Then from the 
-55.5.degree. point to the -44.2.degree. point, the voltage does not 
change since a hollow portion is provided between the two points. Then 
from the -44.2.degree. point the voltage increases and becomes a maximum 
(0.43) at the 0.degree. point, and after passing the 0.degree. point, the 
voltage decreases and becomes 0.15 at the +44.2.degree. point. Then from 
the +44.2.degree. point to the +55.5.degree. point, the voltage does not 
change since a hollow portion is provided between the two points, and from 
the +55.5.degree. point, the voltage decreases and becomes a minimum at 
+65.3.degree. point. 
The induced voltage of the fifth layer, which does not contain any hollow 
portions, increases from the -55.5.degree. point and becomes a maximum at 
the 0.degree. point. After passing the 0.degree. point, the voltage 
decreases and becomes minimum at the +55.5.degree. point. 
As is apparent from FIG. 11, while the embodiment of FIG. 10 results in an 
inter-layer potential difference 8 such inter-layer potential difference 8 
can be greatly decreased as compared with that in the conventional winding 
method shown in FIG. 2, and the resonance based on the inter-layer 
floating capacity 9 shown in FIG. 3 can also be diminished. Consequently, 
it is possible with the aforementioned embodiment to diminish ringing 
which is caused by such resonance. 
In accordance with the present invention, by merely changing the winding 
method for the vertical deflection coil, the inter-layer potential 
difference of the voltage induced in the vertical deflection coil by a 
horizontal deflection magnetic field can be made 0 or greatly decreased. 
As a result, the resonance based on the inter-layer floating capacity of 
the vertical deflection coil can be substantially prevented, so as to 
enable diminishing of ringing. Therefore, it is no longer required to use 
a damping resistor which has heretofore been used to diminish ringing, and 
it is possible to improve the working efficiency and decrease the 
manufacturing cost. 
While we have shown and described several embodiments in accordance with 
the present invention, it is understood that the same is not limited 
thereto but is susceptible of numerous changes and modifications as known 
to those skilled in the art and we therefore do not wish to be limited to 
the details shown and described herein but intend to cover all such 
changes and modifications as are encompassed by the scope of the appended 
claims.