MXPA99005754A - A saddle shaped deflection winding having winding spaces in the rear - Google Patents

Abstract

A deflection yoke for a color cathode ray tube includes a saddle shaped vertical deflection coil and a saddle shaped horizontal deflection coil (3). The horizontal deflection coil (3) includes winding turns forming a pair of side portions (120, 120', 121, 121'), a front end portion (29), close to a screen of the tube, and a rear end portion (19), close to an electron gun of the tube. The side portions form a winding window (18) free of conductor wires therebetween extending between the front end turn portion and the rear end turn portion. Each one of the side portions has first, second and third winding spaces. The first, second and third spaces extend into longitudinal coordinates that are closer to an electron gun of the tube than an end portion of the window established by the end turn portion.

Description

A DEFLECTION COIL IN THE FORM OF DEPRESSION THAT HAS EMBROIDERED SPACES IN THE BACK The invention relates to a deflection yoke for a color cathode ray tube (CRT) of a video display apparatus.

BACKGROUND A cathode ray tube for generating color images usually contains an electron gun that emits three coplanar electron beams (electron beams R, G, and B), to excite a luminescent material of a given red color on a screen. , green, and blue, respectively. The deflection yoke is mounted on the neck of the tube to produce deflection fields created by the horizontal and vertical deflection coils. A ring or core of ferromagnetic material surrounds, in a conventional manner, the deflection coils. It is required that the three generated beams converge on the screen to avoid a landing error of the beam called convergence error that otherwise would produce an error when transmitting the colors. In order to provide convergence, it is known to use astigmatic deflection fields termed auto-convergent. In a self-converging deflection coil, the non-uniformity of the field that is illustrated by the flow lines generated by the horizontal deflection coil, generally has a pincushion shape in a portion of the coil located in the front part, closer to the screen. A distortion of geometry referred to as pincushion distortion occurs in part due to the non-spherical shape of the screen surface. The distortion of the image, referred to as North-South at the top and bottom, and East-West at the sides of the image, is stronger as the radius of curvature of the screen is greater. A coma error occurs due to the beams R and B, which penetrate into the deviation zone at a small angle in relation to the longitudinal axis of the tube, undergo a complementary deviation with respect to that of the central beam G. With respect to the horizontal deviation field, the comma is usually corrected by producing a barrel-shaped horizontal deflection field in the region or area of entry of the deviation yoke beam, behind the aforementioned pincushion field that is used for the error correction of convergence. A combo parabola distortion is manifested in a vertical line on the image side, by a gradual horizontal directional change of the green image relative to the midpoint between the red and blue images, as the line is followed from the center to the corner of the screen. If the change is made to the exterior or to the side of the image, this coma parabola error is conventionally referred to as positive; if it is done inwards or towards the center of the image, the coma parabola error is referred to as negative. It is a common practice to divide the field of deviation into three successive action zones along the longitudinal axis of the tube: the rear or rear zone, closest to the electron gun, the intermediate zone, and the frontal zone closest to the screen. The comma error is corrected by controlling the field in the back zone. The geometry error is corrected by controlling the field in the frontal zone. The convergence error is corrected in the posterior and intermediate zones, and is less affected in the frontal zone. In the deviation yoke of the prior art of the Figure 2, permanent magnets 240, 241, 242 are placed in front of the deflection yoke, to reduce the geometry distortions. Other magnets 142 and field configurators are inserted between the horizontal and vertical deflection coils, to locally modify the field in order to reduce the comma, the parabola coma, and the convergence errors. When the screen has a relatively large radius of curvature greater than IR, such as 1.5R or greater, for example, it becomes increasingly difficult to resolve the previously described beam landing errors, without using magnetic auxiliaries, such as shunts or permanent magnets. It may be desirable to reduce the error, such as the coma parabola error, the comma error, or the convergence error, by controlling the coil distributions of the deflection coils without using magnetic auxiliaries, such as shunts or magnets permanent The elimination of shunts or permanent magnets is desirable because, in an inconvenient manner, these additional components can produce a heating problem in the yoke, related to the higher horizontal frequency, particularly when the horizontal frequency is 32 kHz or 64 kHz and higher. These additional components also, undesirably, can increase the variations between the yokes produced in a way that degrades the geometry, comma, parabola, and convergence error corrections.

COMPENDI A video display deviation apparatus, incorporating a feature of the invention, includes a deflection yoke. The deflection yoke includes a first deflection coil in the form of a depression to produce a deflection field in order to sweep an electron beam along a first axis of a visual display screen of a cathode ray tube. The first deflection coil includes coil turns that form a pair of side portions, a front end portion, close to the screen, and a rear end portion, close to an electron gun of the tube. The side portions form a free coil window of conductive wires therebetween, having a first end portion established by the rear end turn portion and a second end portion established by the front end turn portion. At least one of the side portions has first, second, and third winding spaces that extend to the longitudinal coordinates that are closer to the electron gun than the longitudinal coordinates of the first end portion. The first winding space has a portion that extends to the longitudinal coordinates that are included inside the window. A second deflection coil is used to sweep the electron beam along a second axis of the screen to form a grid. A magnetically permeable core cooperates with the first and second deflection coils to form the deflection yoke. In a convenient manner, the cooperation between the three winding spaces reduces the horizontal coma error. By extending one of the three winding spaces to the longitudinal coordinates that are inside the window, the convergence error and the coma parabola error are also reduced.

BRIEF DESCRIPTION OF THE DRAWINGS In the Drawings: Figure 1 illustrates a deflection yoke, according to a configuration of the invention, mounted on a cathode ray tube. Figure 2 illustrates a front view separated into parts of a deflection yoke according to the prior art. Figures 3a and 3b represent a side view and a top view, respectively, of a horizontal deflection coil according to a configuration of the invention. Figures 4a, 4b, and 4c show the variation, along the main axis Z of the tube, of the distribution function coefficients of the horizontal deflection field generated by the coil of Figures 3a and 3b, and the effects of the winding spaces formed in the coil.

DESCRIPTION OF THE PREFERRED MODALITIES As illustrated in Figure 1, a self-converging color visual display device includes a cathode ray tube (CRT) having an evacuated glass envelope 6, and a phosphorus or luminescent element configuration which represent the three primary colors R, G, and B, configured in one of the ends of the envelope, forming a visual display screen 9. Electron guns 7 are configured in a second end of the casing. The set of electron guns 7 is configured to produce three electron beams 12 aligned horizontally, in order to excite the corresponding luminescent color elements. The electron beams sweep the surface of the screen by operating the deflection yoke 1 mounted on a neck 8 of the tube. Deviation yoke 1 includes a pair of horizontal deflection coils 3, a pair of vertical deflection coils 4, isolated from each other by a separator 2, and a core of ferromagnetic material 5 provided to improve the field of beam paths . Figures 3a and 3b illustrate, respectively, the side and top views of one of the pair of horizontal coils 3, having a depression shape in accordance with an aspect of the invention. Each loop of the coil is formed by a loop of a conductive wire. Each of the pair of horizontal deflection coils 3 has a rear end turn portion 19, near the electron gun 7 of Figure 1, and extending along the longitudinal axis or Z. A front end turn portion 29 of Figures 3a and 3b, disposed near the visual display screen, is curved moving away from the axis Z in a direction generally transverse to the axis Z. Each of the core 5 and the separator 2, conveniently, can be manufactured in the form of a single piece, instead of being assembled from two separate pieces. The lead wires of the front end turn portion 29 of the depression coil 3 of Figures 3a and 3b, are connected with the back end turn portion 19 by bundles of side wires 120, 120 ', which together form a side winding portion, along the Z axis, on one side of the X axis, and by bundles of side wires 121, 121 ', on the other side of the X axis. The side wire bundle portions 120, 120' and 121, 121 ', located near an outlet region of the bundle 23, form the front spaces 21, 21', and 21"of Figure 3a, The front spaces 21, 21 'and 21" affect or modify the distribution harmonic. of current, to correct, for example, the geometric distortions of the image formed on the screen, such as the North-South distortion. In the same way, the portions of the lateral wire bundles 120, 120 ', and 121, 121' located in an entrance region of the bundle 25 of the deflection coil 3, form rear spaces 22 and 22 '. Spaces 22 and 22 'have coil distributions selected to correct horizontal coma errors. The end turn portions 19 and 29, as well as the lateral wire bundles 120 and 121 ', define a main coil window 18. The region along the longitudinal axis Z of the end turn portion 29, defines the region or region of exit of the bundle 23 of the reel 3. The region along the longitudinal axis Z of the window 18, defines an intermediate region or region 24. The window 18 extends, at one end, from the axis coordinate Z of a corner portion 17 where the bundles of side wires 120 'and 121' join. The other end is defined by the turn of end 29. The region of the coil located in the rear part behind the window 18, which includes the rear end turn 19, is referred to as the region or area of entry of the beam 25. The vacuum coil of Figures 3a and 3b can be wrapped with a copper wire of small dimensions, covered with electrical insulation and with thermosetting adhesive. The winding is carried out in a coiling machine that cools the depression coil essentially in accordance with its final shape, and introduces the spaces 21, 21 ', 21", 22, 22' of Figures 3a and 3b during the winding process. The shapes and fittings of these spaces are determined by retractable bolts on the winding head, which limit the shapes that these spaces can assume.After winding, each depression coil is kept in a mold, and a pressure is applied to the object to obtain the required mechanical dimensions, a current passes through the wire in order to soften the thermoformable adhesive, which is then cooled again in order to adhere the wires to one another, and to form a vacuum coil that is self- The positioning of the space 21"formed in the intermediate region 24 is determined, during the winding process, by a bolt in a position 60 of Figure 3a located n the middle region of the intermediate region 24. The result is that a corner portion is formed at position 60 in space 21". The placement of a space 26 formed in the rear portion of the intermediate region 24 is determined, during the winding process, by a bolt at a position 42 located in the rear portion of the intermediate region 24. The result is that a corner portion at the position 42 of the space 26. Both spaces 21"and 26 are located in the lateral portion formed by the bundle of wires 120 and 120 'The pin in the position 60 is located near the center of the intermediate zone 24, and substantially further from the end coordinates of the window 18. The pin in position 42 is located in a rear portion of the intermediate zone 24, near the corner portion 17. The length of the intermediate zone 24 is equal to the difference between the coordinate of the limit Z-axis of the window 18 formed by the return end portion 29, and the coordinate of the Z-axis of the corner portion 17 of the window 18. Each bolt produces an abrupt change in the winding distribution, and forming a corresponding corner-shaped portion in the winding space, in a well-known manner. For example, on the side of the position 60 of Figure 3a that is closer to the entrance area, the closer it is to the corner position 60, the greater the concentration of the wires. On the other hand, on the side of the corner position 60 which is closer to the exit area, the concentration of the wires decreases, as the distance to the position 60 increases. Therefore, the concentration of the wires they are at a local maximum at position 60. The placement of the corresponding bolts associated with spaces 21"and 26, provides separate control parameters or degrees of freedom to correct convergence and residual coma error, while making it possible to minimize to an acceptable value the coma parabola error Conveniently, the use of the combination of the winding space 21", formed in the beam 120 in the intermediate region 24, and of a winding space formed in the region 25, such as the space 22 or 22 ', provides the required variations along the Z axis, in such a way that the use of local field configurators, such as derivations or manes Most geometry errors are corrected by a known configuration of wires in the output area 23. The comma errors are partially corrected by the winding spaces formed in the wires in the back end portion 19 of the zone of beam entry 25. In the configuration of Figures 3a and 3b, the convergence and residual coma errors are partially corrected by the operation of a portion of the wires in the intermediate zone established by the bolt at position 60, and by operating a portion of the wires in the intermediate zone established by the pin in position 42. Each of the corrections partially contributes to the reduction of the convergence and comma errors. Conveniently, the aforementioned convergence and coma error corrections, through the operations of the pins at positions 42 and 60, produce variations in the coma parabola errors in opposite directions to each other. Accordingly, conveniently, the coma parabola error can be minimized to an acceptable magnitude. In the example of Figures 3a and 3b, the deflection yoke is mounted on a tube of type A68SF, which has a screen of the aspheric type, and a radius of curvature of the order of 3.5R on the horizontal edges. The horizontal coil 3 has a total length along the Z axis that is equal to 81 millimeters. The horizontal coil has a region or area of exit of the beam or front 23, formed by the end turn wire of 7 millimeters in length along the axis Z. The horizontal coil 3 has the intermediate zone 24, which has the length of 52 millimeters, where the window 18 of Figure 3b extends. The horizontal coil 3 has the rear end turn wire 19, which extends to a length along the Z axis of 22 millimeters. The wires at the rear of the coil are wound in such a manner as to constitute several bundles or groups locally spaced from each other by wire-free spaces. As can be seen by examining the coil of Figures 3a and 3b along its plane of symmetry YZ, in the zone 24, the spaces 21"and 26 are created by inserting bolts in the locations 60 and 42 during the winding process, as indicated above.The bolt in the position 60 maintains the wire bundles 120 in approximately 94 percent of the number of coil wires The bolt at position 60 is located at a distance of 27 millimeters from the front of the coil, approximately in the middle of intermediate region 24, at an angular position in the plane XY of 31.5 degrees The bolt at location 42 maintains the bundle of wires 45 of Figure 3a at approximately 49 percent of the number of coil wires.The bolt at position 42 is set at 56 millimeters from the front of the coil. The coil, in an angular position in the XY plane that is equal to 33 degrees, Space 26 extends along the Z axis between 47 millimeters and 62 millimeters from the front of the deflection coil. r 17 of the window 18 defines the furthest coordinate on the Z axis from the front of the window coil 18. The corner portion 17 is positioned along the Z axis at a distance of 59 millimeters from the front of the coil. Conveniently, the Z-axis coordinate of the position 42 is selected within a range between a coordinate of the Z axis that is equal to that of the corner portion 17, located at one end of the window 18, and a coordinate of the Z axis that is closest to the screen, at a distance from the corner portion 17 of about 10 percent of the length of the intermediate zone 24. The length of the intermediate zone 24 is equal to the distance between the coordinate of the Z axis of the corner portion 17, at one end of the window 18, and the coordinate of the Z axis at the other end of the window 18, formed by the end turn portion 29. The selection of the coordinate of the Position 42 within the range of 10 percent of the length of the intermediate zone, provides an optimum coma parabola error correction. It also makes it possible to avoid the use of leads and magnets. In the embodiment of a feature of the invention, in addition to the aforementioned winding space 26, which extends to the zone 25, the pair of winding spaces 22 and 22 'are also formed in the zone 25. The winding spaces 22 and 22 'are formed by the insertion of bolts at locations 40 and 41, respectively, in the area 25 of the back end loop wire, during the winding process. The pin at location 40 of Figure 3a forms a bundle of wires 43, representing approximately 11 percent of the number of coil wires, and is set to 75 millimeters from the front of the coil, at an angular position in the XY plane corresponding to 16 degrees. The bolt at location 41 maintains beam 44, which represents 27 percent of the number of coil wires, and is set to 70 millimeters from the front of the coil at an angular position in the XY plane equal to 55 degrees. Accordingly, the corner portion of the winding space 22 ', located between the winding spaces 22 and 26, with respect to the axis Z, is in the angular position of 55 degrees. Conveniently, the corner portions of the winding spaces 22 and 26 are at smaller angular positions of 16 degrees and 33 degrees, respectively, than the angular position of 55 degrees of the bolt at location 41. By maintaining This order of angular position, the bolts make it possible to locally modify the higher order coefficients of the field, and in particular, reduce the comma error to a sufficiently low value. As shown in Figure 3b, the winding space 22 'extends free of conductive wires between the two sides of the plane of symmetry YZ including the longitudinal axis Z. Each of the winding spaces 22 or 22' can be extended. between the two sides of the YZ plane of symmetry, as shown in Figure 3b with respect to the pair of winding spaces 22 '. Alternatively, each of the winding spaces 22 or 22 'can be formed as a pair of separate winding spaces on the two sides of the plane of symmetry Yz, as shown in Figure 3b with respect to the pair of spaces FIG. 4a and 4b illustrate the influence of the winding spaces 22 and 22 'on the fundamental or zero-order coefficient HO and the higher order coefficients H2 and H4 of the field distribution function of the field horizontal deviation. This influence is manifested mainly in the back of the coil without influencing the zero-order and second-order coefficients HO and H2 of the field distribution function on the front of the deviation yoke. Figure 4c illustrates the influence of space 26 on the coefficient of zero order HO and the highest order coefficients H2 and H4 of the field distribution function of the horizontal deviation field. The influence of space 26 extends both to the front and to the back of the coil; modifies in particular at the front of the intermediate zone, the magnitude and the length along the Z axis on which a positive second order coefficient H2 of the field distribution function of the horizontal deviation field is applied. The second order coefficient H2 of the field distribution function of the horizontal deviation field affects the convergence of the beams and the geometry of the image. The following table shows the effects on the geometry, coma, and convergence errors provided by the inclusion of space 26 in the coil. The results can be compared with those obtained in a deflection yoke that does not include a winding space, such as space 26, and where the comma was corrected by the operation of spaces similar to spaces 22 and 22 ', and the convergence of the beams by the operation of spaces similar to spaces 21, 21 ', and 21. In the table, comma (horizontally and vertically) and convergence errors are measured in nine points, conventionally representative of a quadrant of The screen of the cathode ray tube The errors of North-South geometry are measured in relation to the horizontal edges of the image (North-South external geometry) and half the distance between one edge and the center of the screen (North-South internal geometry).

Comma Coma ConverGeometría Vertical Horizontal gencia N / S Without 0.06 -0.07 -0.1 0 0.71 1.89 0.42 0.41 1.22 Ext.- 0.11% window 0.11 0.06 0.11 0. 0.77 2.45 0.19 0.89 4.24 26 0 0 0 0 0.8 2.72 0 0.97 5.74 Int.- 0.25% With 0.01 -0.09 -0.1 0 0.03 0.11 0.4 0.19 0.49 Ext.- 0.39% window 0.1 0.06 -0.1 0 -0 0.01 0.17 0.28 0.65 26 0 0 0 0 -0 0.12 0. 0.14 0.93 Int.- 0.54% The table shows that the vertical comma error, already small, is not degraded by space 26. On the other hand, the horizontal comma error and the convergence error are significantly reduced, in particular on the vertical edges of the image. In the same way, the North-South geometry of the image is improved. Conveniently, when space 26 is used, the pin-shaped North-South geometry deviation from a straight line, measured on the screen, is closer to the desirable value of -1 percent than that obtained without using the space 26. A deviation of -1 percent indicates a pincushion pattern on the screen. This deviation is desirable because it is perceived as free of distortion of geometry by a viewer at a distance from the screen equal to five times the height of the image. According to the absolute and relative amplitude of the errors to be minimized, the relative percentage of the wires held by the pin at location 42 below a certain angular position in the XY plane can be modified, or the position in accordance with Z of the bolt, or the angular position of the bolt itself. The space 26 has an appropriate surface area and extends both in the rear 25 and in the intermediate zone 24 of the coil. In an implementation mode not shown, two windows can be formed on the side wires located according to the Z axis in the area near the end or corner portion 17 of the main window 18. These two windows are partially extended both up into zone 24 as well as into zone 25. By placing the bolts making these windows during the winding process in different angular positions, it is possible to create groups of wires, where the group of wires can vary in relative value that allows to vary the effect created on the field, and obtain a finer action on the coefficient of zero order HO, and the highest order coefficients of the field distribution function of the horizontal deviation field, in order to minimize the comma, geometry, and convergence errors. The implementation examples described above are not limiting; the insertion during the winding of a bolt located behind the intermediate zone of a coil, makes it possible to create a space that can be extended to both the intermediate zone and the posterior zone, and therefore, it can be applicable to modify a deviation field vertical, in order to minimize the residual errors of convergence, coma, and geometry.

Claims (8)

1. A video display deflection apparatus, which comprises: a first deflection coil in the form of a depression to produce a deflection field, for sweeping an electron beam along a first axis of a visual display screen of a cathode ray tube, including the first deflection coil a plurality of coil turns forming a pair of side portions, a front end portion, near the screen, and a rear end portion, near an electron gun of the tube, the side portions forming a winding window free of conductive wires therebetween, having a first end portion established by the rear end turn portion, and a second end portion established by the front end turn portion. , having at least one of the lateral portions, first, second, and third winding spaces to correct the landing error of the beam, each of the spaces extending to a corresponding longitudinal coordinate that is closer to the electron gun than a longitudinal coordinate of the first end portion; a second deflection coil for sweeping the electron beam along a second axis of the screen, to form a grid; and a magnetically permeable core for cooperating with the first and second deflection coils, to form a deflection yoke.

2. A video display deflection apparatus according to claim 1, wherein the first winding space extends mainly up to the longitudinal coordinates that are inside the window.

3. A video display deflection apparatus according to claim 1, wherein the first deflection coil comprises a horizontal deflection coil. A video display deflection apparatus according to claim 1, wherein the first, second, and third winding spaces are formed in each of the side portions, and wherein the second winding spaces, formed in the side portions, respectively, form the corresponding portions of a winding space extending between the side portions. A video display deflection apparatus according to claim 1, wherein each of the first, second, and third winding spaces, has a corresponding corner portion formed by a corresponding bolt, during its manufacture, in wherein the corner portion of the second winding space is located intermediate the corner portions of the first and third winding spaces, and wherein an angular position of the corner portion of the second winding space is greater than an angular position of each of the corner portions of the first and third winding spaces. 6. A video display deflection apparatus according to claim 1, wherein the first winding space has a portion extending to a longitudinal coordinate that is included within the longitudinal coordinate of the window. A deflection apparatus according to claim 1, which further includes the cathode ray tube, wherein this cathode ray tube has a radius of curvature greater than 1.5R. A deflection apparatus according to claim 1, wherein the cathode ray tube has a radius of curvature of the order of 3.5R on the horizontal edges.