The present invention relates to deflection yoke devices for use in the picture tubes of video display devices such as color television devices.
Color television devices of the projection type for projecting video images on a screen in front of the device are provided with three video display devices for R (red), G (green) and B (blue). These display devices are arranged as directed toward the screen in front of the devices.
Each of the video display devices comprises a picture tube 2 and a deflection yoke device 10 as shown in FIG. 6. The picture tube 2 comprises a cone portion 21, a neck portion 22 projecting from a small-diameter end of the cone portion 21, and a face plate 23 formed at a large-diameter end of the cone portion 21, these components being joined into an integral assembly. The neck portion 22 has an electron gun 3 housed therein. The deflection yoke device 10 extends from part of the cone portion 21 of the tube 2 to the neck portion 22 thereof, as provided around these portions. In the drawings to be referred to hereinafter, the horizontal direction and the vertical direction of the picture tube 2 are represented by the X-axis and the Y-axis, respectively, and the direction toward which an electron beam is emitted from the electron gun 3 is represented by the Z-axis.
With reference to
The main yoke portion 4 comprises a main yoke horizontal coil 6 provided along the inner peripheral surface of a conical bobbin 80, a core 8 provided around the outer peripheral surface of the bobbin 80, and a main yoke vertical coil 7 wound around the core 8. By passing current through the main yoke horizontal coil 6, a horizontal magnetic field is produced inside the picture tube 2. A vertical magnetic field is set up inside the picture tube 2 by passing current through the main yoke vertical coil 7. The electron beam emitted by the electron gun 3 is deflected horizontally and vertically by these magnetic fields.
When a periodic sawtooth current is passed through the main yoke horizontal coil 6 and the main yoke vertical coil 7, the electron beam scans the face plate 23 of the picture tube 2 in a horizontal direction and a vertical direction, thereby producing images on the face plate 23. R, G, B images produced by the three video display devices are projected as enlarged on the screen in front, and the images are superimposed to display color images on the screen. In digital color television devices of recent years, a sawtooth current having a frequency of 31.5 KHz is used for horizontal scanning, and like current with a frequency of 60.0 Hz for vertical scanning.
With reference to
When current is passed through the convergence horizontal coil 51 in a direction indicated by arrows in the drawing, a magnetic field is produced in the interior space S0 of the picture tube 2, the magnetic field pointing from above downward as indicated by solid-line arrows in FIG. 9. An electron beam 9 emanating from the electron gun 3 toward the viewer of the drawing perpendicular to the plane of the drawing is deflected by the magnetic field toward the right in the drawing. Further when current is passed through the convergence vertical coil 52 in a direction indicated by arrows in the drawing, a magnetic field pointing from the right toward the left is produced in the upper half of the interior space S0 and a magnetic field pointing from the left toward the right is produced in the lower half thereof as indicated by broken-line arrows in the drawing. The electron beam 9 is deflected by the magnetic fields downward in the drawing.
Accordingly, RGB three electron beams, even if deflected in any direction, can be converged toward one point on the face plate of the picture tube by adjusting the currents to be passed through the convergence horizontal coils 51 and the convergence vertical coils 52 of the R, G, B video display devices, whereby RGB three images can be perfectly superimposed on the screen.
When a current having a horizontal scanning frequency is passed through the main yoke horizontal coil 6 shown in
Thus with the deflection yoke device 10 shown in
An object of the present invention is to provide a deflection yoke device of simple construction which is adapted to effectively suppress the induction voltage to be produced in a convergence yoke portion due to a leakage magnetic field from a main yoke portion without providing a removal circuit or like special circuit.
The present invention provides a deflection yoke device comprising a main yoke portion for deflecting an electron beam emitted by an electron gun, and a convergence yoke portion for adjusting the convergence of the electron beam, the main yoke portion and the convergence yoke portion being coaxially arranged as positioned in proximity to each other, the convergence yoke portion being provided with a coil having short-circuited opposite ends.
With the deflection yoke device of the invention, the convergence yoke portion is provided with a short-circuited coil, so that even if a fluctuation magnetic field leaks from the main yoke portion and ingresses into the convergence yoke portion, the short-circuited coil generates a magnetic field in such a direction as to offset the leakage magnetic field. This greatly lessens the influence of the leakage field to be exerted on the convergence yoke portion, effectively suppressing the induction voltage generated in the convergence yoke portion due to the leakage field.
Stated specifically, the convergence yoke portion comprises an annular convergence core, a convergence horizontal coil wound around both of left and right two regions of the core which intersect a horizontal axis, and a convergence vertical coil wound around both of upper and lower two regions of the core which intersect a vertical axis, the short-circuited coil being provided around each of the left and right two regions of the convergence core.
With this specific construction, a leakage magnetic field from the main yoke portion will act mainly on the left and right two regions of the convergence core having the convergence horizontal coil wound therearound, whereas these regions are each provided with the short-circuited coil, which induces a magnetic field of opposite direction to the leakage field. Consequently, the induction voltage produced in the convergence yoke portion by the leakage field from the main yoke portion is almost completely suppressed. However, since no short-circuited coil is wound around the regions provided with the convergence vertical coil, the convergence correcting magnetic field to be produced by the convergence vertical coil is free of any influence.
As described above, the deflection yoke device of the present invention is capable of suppressing the induction voltage to be generated in the convergence yoke portion by a simple construction wherein a short-circuited coil only is provided on the convergence yoke portion, without providing a special circuit, such as a circuit for removing the fluctuation magnetic field from the main yoke portion. This ensures more accurate convergence correction than is conventionally made.
FIG. 4(a) is a graph showing the result obtained by measuring the voltage across the terminals of a convergence vertical coil of a conventional deflection yoke device;
FIG. 4(b) is a graph showing the result obtained by measuring the voltage across the terminals of a convergence vertical coil of the deflection yoke device of the invention;
The present invention as embodied into video display devices for a color television device of the projection type will be described below in detail with reference to the drawings.
With reference to
The main yoke portion 4 comprises a main yoke horizontal coil 6 provided along the inner peripheral surface of a conical bobbin 80, a core 8 provided around the outer peripheral surface of the bobbin 80, and a main yoke vertical coil 7 wound around the core 8.
With reference to
The convergence core 53 further has short-circuited coils 54, 54 each having one to several turns and wound respectively around left and right two portions of the core 53 which intersect the X-axis. Each coil 54 has opposite ends which are short-circuited.
When current is passed through the convergence horizontal coil 51 of the convergence yoke portion 5 shown in
In the deflection yoke device 1 of the present invention, the convergence yoke portion 5 is positioned in the vicinity of the base portion 60 of the main yoke horizontal coil 6 as shown in
Since no short-circuited coil 54 is wound around the regions provided with the convergence vertical coil 52, the convergence correcting magnetic field to be produced by the convergence vertical coil 52 is free of any influence.
FIG. 4(a) shows the result achieved by the conventional deflection yoke device 10 and obtained by measuring the voltage across the terminals of the convergence vertical coil 52, with the main yoke portion 4 in operation. FIG. 4(b) shows the result achieved by the deflection yoke device 1 of the invention and obtained by measuring the voltage across the terminals of the convergence vertical coil 52, with the main yoke portion 4 in operation. The graphs reveal that the variations in the voltage across the terminals of the convergence vertical coil 52 have the same waveform regardless of the presence or absence of the pair of short-circuited coils 54, 54. This indicates that accurate convergence can be effected by the convergence vertical coil 52 despite the presence of the short-circuited coils 54, 54.
As described above, the deflection yoke device 1 of the present invention is capable of effectively suppressing the induction voltage to be generated in the convergence horizontal coil 51 by offsetting a magnetic field leaking from the main yoke portion 4 and acting on this horizontal coil 51, using a simple construction wherein short-circuited coils 54, 54 only are provided on the convergence yoke portion 5, without providing a special circuit, such as a circuit for removing the fluctuation magnetic field from the main yoke portion 4. This ensures more accurate horizontal convergence correction than is conventionally possible.
The device of the present invention is not limited to the foregoing embodiments in construction but can be modified variously by one skilled in the art without departing from the spirit of the invention as set forth in the appended claims. For example as shown in
Number | Date | Country | Kind |
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2002-211680 | Jul 2002 | JP | national |
Number | Name | Date | Kind |
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5172035 | Sakurai et al. | Dec 1992 | A |
5430351 | Yokota | Jul 1995 | A |
6737818 | Sakurai et al. | May 2004 | B2 |
Number | Date | Country | |
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20040017145 A1 | Jan 2004 | US |