JP2002042696A - Deflection yoke and display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent upper and lower pin cushion distortion caused by the temperature rise. SOLUTION: This deflection yoke comprises a pair of vertical deflection coils 17, 17 adapted to form a vertical deflection magnetic field, a correction coil 21 adapted to form a correction magnetic field to deflect vertically an electron beams on the rear end of the deflection yoke, a current supply means adapted to supply a correction current Ih with serrate waves corresponding to a vertical deflection period for the correction coil 21 and a thermistor Tm having characteristics to lower resistance by the temperature rise for acting such that the correction current Ih flowing in the correction coil 21 increases by the temperature rise when the vertical deflection magnetic field by the pair of vertical deflection coils 17, 17 and the correction magnetic field by the correction coil 21 are formed in the same direction within the vertical deflection period and for acting such that the correction current Ih flowing in the correction coil 21 decreases by the temperature rise when the vertical deflection magnetic field and the correction magnetic field are formed in the opposite directions within the vertical deflection period.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a cathode ray tube (CR)
The present invention relates to a display device such as a television receiver or a computer display using T), and in particular, to a deflection yoke (Deflection Yoke;
DY).

[0002]

2. Description of the Related Art Generally, a display device using a cathode ray tube is:
A deflection yoke deflects the electron beam emitted from the electron gun up, down, left, and right. The deflection yoke has a horizontal deflection coil and a vertical deflection coil, and is used by being mounted on a cathode ray tube. The horizontal deflection coil forms a horizontal deflection magnetic field that deflects the electron beam left and right (horizontal direction), and the vertical deflection coil shifts the electron beam up and down (vertical direction).
A vertical deflection magnetic field is formed to deflect the light into a vertical direction.

By the way, the distance from the center of deflection of the fluorescent screen of the cathode ray tube to which the electron beam is radiated becomes larger as it goes to the periphery, and when the electron beam is deflected, deflection occurs at the four corners (corners of the screen) where the distance is greatest. The shake is the largest. As a result, the raster image formed by the horizontal and vertical scanning of the electron beam is distorted into a pincushion shape (peg shape). Such pincushion type image distortion,
It is divided into left and right pincushion distortions that appear as curved vertical lines on the screen, and upper and lower pincushion distortions that appear as curved horizontal lines on the screen, and are individually corrected.

Among them, a pair of upper and lower ferrite magnets (bar-shaped permanent magnets) are arranged at the front end side (closer to the fluorescent screen) of the deflection yoke as a means for correcting the upper and lower pincushion distortion. There is known a technique for correcting upper and lower pincushion distortion by the action of a magnetic field.

[0005]

However, in the correction technique using the pair of ferrite magnets, for example, there is a variation in the winding distribution of the vertical deflection coil,
If the characteristics of the ferrite magnet itself vary, the amount of correction for the upper and lower pincushion distortions may be excessive or insufficient. As a result, if the correction amount is too small, a pincushion-shaped image distortion in which the horizontal line curves inward on the screen remains, and if the correction amount is too large, the barrel-shaped image distortion in which the horizontal line curves outward on the screen. Image distortion remains. Hereinafter, pincushion-type and barrel-type image distortion in which horizontal lines are curved on the screen will be referred to as “vertical image curvature distortion”.

As a countermeasure, a correction coil is attached to the rear end side (closer to the electron gun) of the deflection yoke, and a correction current corresponding to the vertical deflection cycle is supplied to the correction coil to reduce vertical image bending distortion. Techniques for eliminating this have been proposed.

Here, the principle of correcting the vertical image distortion using the correction coil will be described with reference to FIG. In FIG. 7, a core 31 and a vertical deflection coil 32 are provided on a deflection yoke 30, and an electron beam emitted from an electron gun (not shown) is vertically deflected and drawn on a phosphor screen 33 along a predetermined orbit. It has become. A correction coil 34 is disposed on the electron gun side of the core 31 and the vertical deflection coil 32, that is, on the rear end side of the deflection yoke 30.

Now, it is assumed that the electron beam follows the trajectory of K0 and enters the fluorescent screen 33 when no correction current of the vertical deflection period is supplied to the correction coil 34 and no correction magnetic field is generated. On the other hand, when a correction current corresponding to the vertical deflection period is supplied to the correction coil 34, the trajectory of the electron beam changes as follows according to the direction of the correction magnetic field generated by the correction current. That is, when the correction magnetic field is generated in the same direction as the vertical deflection magnetic field by the vertical deflection coil 32, the electron beam enters the fluorescent screen 33 along the trajectory of K1, and generates the correction magnetic field in the opposite direction to the vertical deflection magnetic field. When you do
The electron beam enters the phosphor screen 33 along the path of K2.

When the trajectory of the electron beam changes due to the correction magnetic field generated by the correction coil 34, the incident angle θ of the electron beam to the phosphor screen 33 changes accordingly. Specifically, the incident angle θ becomes relatively small in the order of the electron beam tracing the trajectory of K1, the trajectory of K0, and the trajectory of K2.

On the other hand, of the vertical image bending distortion,
The pincushion-type image distortion tends to decrease when the incident angle θ of the electron beam with respect to the phosphor screen 33 becomes relatively large, and conversely tends to increase when the incident angle θ becomes relatively small. Therefore, when pincushion-shaped image distortion occurs, the amount of distortion can be reduced by changing the trajectory of the electron beam from K0 to K1 by the correction magnetic field by the correction coil 34. When barrel-shaped image distortion occurs, the trajectory of the electron beam is changed by K by the correction magnetic field by the correction coil 34.
By changing from 0 to K2, the amount of distortion can be reduced. Further, by controlling the amount of current flowing through the correction coil 34 to adjust the strength of the correction magnetic field, it is possible to appropriately correct both the pincushion-type and barrel-type image distortions.

However, even if the distortion of the upper and lower images is corrected by using the correction coil 34, the temperature of the surroundings may be reduced due to the heat generated by the operation of the deflection yoke or the heat radiated from the heating element (such as a circuit board) in the display device. Rises, the magnetic field of the pair of ferrite magnets described above weakens. for that reason,
In the initial state where the display device is started, even if the raster 1 is formed without distortion as shown in FIG.
When the temperature rises, as shown in FIG.
Is distorted into a pincushion shape.

As a countermeasure, an attempt has been made to correct by attaching a ferrite to the deflection yoke. However, this method has not been able to reliably prevent the occurrence of upper and lower pincushion distortion due to temperature rise.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and an object of the present invention is to provide a deflection yoke and a display device capable of reliably preventing the occurrence of upper and lower pincushion distortions due to a temperature rise. To provide.

[0014]

In a deflection yoke according to the present invention, a pair of vertical deflection coils for forming a vertical deflection magnetic field and a correction for forming a correction magnetic field for vertically deflecting an electron beam at a rear end side of the deflection yoke. A coil, current supply means for supplying a correction current of a sawtooth wave corresponding to the vertical deflection period to the correction coil, and a pair of vertical deflection coils having a characteristic in which a resistance value changes due to a temperature rise. When the vertical deflection magnetic field generated by the correction coil and the correction magnetic field generated by the correction coil are formed in the same direction, the amount of the correction current flowing through the correction coil operates so as to increase as the temperature rises. Is formed in the opposite direction, a temperature compensating element that operates so that the amount of the correction current flowing through the correction coil decreases due to the temperature rise. Further, the display device according to the present invention uses the deflection yoke having the above configuration.

In the deflection yoke having the above structure and the display device using the same, when the vertical deflection magnetic field by the pair of vertical deflection coils and the correction magnetic field by the correction coil are formed in the same direction within the vertical deflection cycle, the temperature rises. As a result, the amount of the correction current flowing through the correction coil increases due to the change in the resistance value of the temperature compensating element, thereby increasing the correction magnetic field. When the vertical deflection magnetic field and the correction magnetic field are formed in opposite directions within the vertical deflection period, the amount of the correction current flowing through the correction coil decreases due to a change in the resistance value of the temperature compensating element due to the temperature rise. Is weakened. As a result, when the resistance value of the temperature compensation element changes due to a temperature rise, the intensity of the correction magnetic field by the correction coil changes in a direction in which the incident angle of the electron beam on the phosphor screen becomes relatively large.

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of the present invention when applied to, for example, a display device having an in-line cathode ray tube and a deflection yoke used in the display device will be described in detail with reference to the drawings. .

FIG. 1 is a schematic perspective view showing an overall image of a cathode ray tube according to the present invention. In FIG. 1, a cathode ray tube bulb (cathode ray tube main body) 10 includes a panel section 11, a funnel section 12, and a neck section 13. On the inner surface of the panel section 11, a phosphor screen (not shown) in which red, blue, and green phosphors are arranged in a pattern is formed. On the other hand, an electron gun 14 serving as an emission source of an electron beam is provided in the neck portion 13. A deflection yoke 15 for deflecting the electron beam is mounted on a cone portion extending from the neck portion 13 to the funnel portion 12. The deflection yoke 15 is mounted and adjusted so that the center axis of the yoke 15 coincides with the center axis of the cathode ray tube bulb 10.

The cathode ray tube having the above-described structure is incorporated in a casing (not shown) together with various accessories necessary for reproducing a color image (or a black and white image) on the phosphor screen on the inner surface of the panel section 11, thereby providing a television. A display device such as a receiver or a display for a computer is configured.

FIG. 2 is a side view including a partially broken cross section of the deflection yoke according to the present invention. In FIG. 2, the deflection yoke 15
Are equipped with components such as a horizontal deflection coil 16, a vertical deflection coil 17, a separator 18, a DY core 19, and a ring magnet 20. The horizontal deflection coil 16 is incorporated on the inner peripheral side of the separator 18, and the vertical deflection coil 17 is incorporated on the outer peripheral side of the separator 18. The separator 18 is made of an insulating material such as a resin, and has a substantially trumpet shape as a whole.

The horizontal deflection coil 16 is connected to the deflection yoke 1.
The vertical deflection coil 17 is wound in a pair on the left and right sides of the deflection yoke 15 in a saddle shape. Then, on the trajectory of the electron beam emitted from the electron gun 14, the horizontal deflection coil 16 generates a magnetic field (horizontal deflection magnetic field) for deflecting the electron beam left and right (horizontally), and the vertical deflection coil 17 converts the electron beam. A magnetic field (vertical deflection magnetic field) that deflects vertically (vertically) is generated. The vertical deflection coil 17 may be wound around the DY core 19 in a toroidal shape.

The DY core 19 is made of a magnetic material such as ferrite, and is formed in a substantially conical cylindrical shape with one opening in the direction of the center axis of the yoke larger than the other. This DY
The core 19 includes a horizontal deflection coil 16 and a vertical deflection coil 1.
In order to enhance the effect of the magnetic field generated by the, the deflecting coils 16 and 17 are mounted so as to cover them. The ring magnet 20 is used to correct the deflection yoke 1 in order to correct the trajectory shift of the electron beam due to an assembly error of the electron gun 14 or the like.
5 at the rear end.

Further, on the rear end side of the deflection yoke 15, there is provided a correction coil 21 for correcting a vertical image bending distortion. As shown in FIG. 3, the correction coil section 21 forms a correction magnetic field (described later) for vertically deflecting the three electron beams B, G, and R traveling inside the neck section 13 of the cathode ray tube. It is composed of two coils L1 to L6.

The six coils L1 to L6 are formed by a pair of C-shaped magnetic members 22A, 22A disposed outside the neck portion 13.
B and a pair of T-shaped magnetic bodies 23A and 23B. The pair of C-shaped magnetic bodies 22A and 22B are arranged so as to be opposed to each other on the Y axis (up and down) which is the vertical axis of the deflection yoke 15. A pair of T-shaped magnetic bodies 23A, 23
B are arranged so as to face each other on the X axis (left and right) which is the horizontal axis of the deflection yoke 15.

On the other hand, the coil L1 is a T-shaped magnetic body 2
The end of 3A, the coil L2 is one end (left side of the figure) of the C-shaped magnetic body 22B, the coil L3 is the end of the other side (right side of the figure) of the C-shaped magnetic body 22B, and the coil L4 is a T-shaped magnetic body. The end of 23B, the coil L5 is wound around one end (right side in the figure) of the C-shaped magnetic body 22A, and the coil L6 is wound around the other end (left side in the figure) of the C-shaped magnetic body 22A. .

The shape of the magnetic body around which the coils L1 to L6 are wound is not limited to the above-mentioned C-shape and T-shape. In addition, without using a magnetic material serving as a magnetic core,
It is also possible to configure the coils L1 to L6 with air-core coils.

FIG. 4 is a circuit diagram showing a coil connection state according to the embodiment of the present invention. In FIG. 4, a pair of vertical deflection coils 17, 17 are connected in series with each other. To this pair of vertical deflection coils 17, 17, a sawtooth current Iv corresponding to the vertical deflection cycle is supplied from a vertical deflection circuit (not shown). The sawtooth wave current Iv is a current supplied to the pair of vertical deflection coils 17, 17 in synchronization with the vertical deflection cycle, that is, a vertical deflection current. The vertical deflection current Iv is, for example, a positive (positive) value in the first half of the vertical deflection cycle (in other words, a period during which the electron beam is deflected to the upper side of the screen), and the latter half (in other words, the electron beam is shifted below the screen). (A period during which the light is deflected to the side) takes a negative (negative) value.

A correction circuit 24 forming a bridge circuit is connected in series to the pair of vertical deflection coils 17 and 17. In the correction circuit 24, a fixed resistor R1 is connected between the input terminal T1 and the output terminal T2, and a fixed resistor R2 is connected between the output terminal T2 and another input terminal T3. Also, two input terminals T1, T
3, a fixed resistor R3, a variable resistor VR and a fixed resistor R
4 are connected in series. Among them, the fixed resistor R3
Is connected between the input terminal T1 and the variable resistor VR, and the fixed resistor R4 is connected between the other input terminal T3 and the variable resistor VR.

Further, between the input terminal T1 and the slider S of the variable resistor VR, a correction coil 21 formed by connecting six coils L1 to L6 in series with each other is connected. A bridge circuit is formed with the position of the other output terminal. A thermistor Tm is connected between the slider S of the variable resistor VR and the input terminal T1 so as to be connected in parallel with the fixed resistor R3. This thermistor Tm
Is equivalent to the temperature compensating element of the present invention, and has a characteristic that the temperature coefficient of the resistance takes a negative value, that is, has a characteristic that the resistance value decreases as the temperature rises.

Here, the resistance values of the fixed resistors R1 and R2 are set substantially equal. In addition, 1 / variable resistor VR
The combined resistance of two resistors, the fixed resistor R3 and the thermistor Tm, and the combined resistance of one half of the variable resistor VR and the fixed resistor R4 are set substantially equal. Furthermore, the combined resistance value of the fixed resistors R1 and R2 is set substantially equal to the combined resistance value of the variable resistor VR and the two fixed resistors R3 and R4. Accordingly, in the correction circuit 24 forming the bridge circuit, the variable resistor VR
It is configured so that the bridge can be balanced at the center position.

In such a circuit configuration, a vertical deflection current Iv supplied from a vertical deflection circuit (not shown) is supplied to a pair of vertical deflection coils 17, 17 in the first half of the vertical deflection cycle.
Flows in the direction of the arrow. The vertical deflection current Iv is also supplied to the correction circuit 24 via the pair of vertical deflection coils 17, 17.

At this time, if the slider S of the variable resistor VR is at the center position, the bridge of the correction circuit 24 is in a balanced state, so that half of the vertical deflection current Iv flowing from the input terminal T1 is reduced by the fixed resistor R1. , R2, and the other half flows into the thermistor Tm and the fixed resistor R3, and then shunts to the variable resistor VR and the fixed resistor R3.
4 and flows out of another input terminal T3. for that reason,
No current flows through the correction coil 21.

On the other hand, when the slider S of the variable resistor VR is moved from the center position to one side (the fixed resistor R3 side), the bridge balance of the correction circuit 24 is broken, whereby the correction coil 21 A saw-tooth wave current (hereinafter, referred to as a correction current) Ih flows in the direction. This correction current Ih
Can be adjusted by moving the slider S of the variable resistor VR at one end (the left end in the figure).
It increases as it approaches.

When the slider S of the variable resistor VR is moved from the center position to the other side (fixed resistor R4 side), the correction coil 2 is displaced due to the collapse of the bridge balance as described above.
Although the correction current Ih flows through 1, the direction of the current is opposite to that in the previous case (the direction of the arrow shown in FIG. 4). The amount of the correction current Ih increases as the slider S of the variable resistor VR approaches the other end (the right end in the figure).

As described above, in the circuit configuration of this embodiment, the amount and direction of the correction current Ih flowing through the correction coil 21 can be arbitrarily adjusted by moving the position of the slider S of the variable resistor VR. It has become.

Next, a correction magnetic field formed when the correction current Ih flows through the correction coil 21 will be described with reference to FIGS. 5 and 6 both show a state in which the neck portion 13 of the cathode ray tube is viewed from the panel side.

First, as shown in FIG.
Four coils L wound around the magnetic members 22A and 22B
When a correction current Ih flows in the directions of arrows in L2, L3, L5, and L6, a pair of C-shaped magnetic bodies 22 are formed on the orbits of the three electron beams B, G, and R emitted in an in-line arrangement.
A quadrupole magnetic field φ1 having magnetic poles (N pole and S pole) at both ends of A and 22B is formed.

The quadrupole magnetic field φ1 is a pincushion-type magnetic field in which one end of each of the pair of C-shaped magnetic bodies 22A and 22B has an N pole and the other end has an S pole. Therefore, a quadrupole magnetic field φ1 acts on the three electron beams B, G, and R in such a manner that they are vertically deflected upward. Further, since the quadrupole magnetic field φ1 has a pincushion shape, a magnetic field acts more strongly on the center beam G at the center than on the side beams B and R on both sides.

On the other hand, as shown in FIG.
Two coils L wound around the magnetic members 23A and 23B
When the correction current Ih flows in the direction of the arrow in L1 and L4, the ends of the pair of T-shaped magnetic bodies 23A and 23B are respectively connected to the magnetic poles (N) on the orbits of the three electron beams B, G and R.
(Pole, south pole).

The dipole magnetic field φ2 is a barrel-shaped magnetic field in which the end of one T-shaped magnetic body 23A is an S pole and the end of the other T-shaped magnetic body 23B is an N pole. Therefore, a dipole magnetic field φ2 acts on the three electron beams B, G, and R in such a manner that they are vertically deflected upward. Also, 2
Since the dipole magnetic field φ2 has a barrel shape, a stronger magnetic field acts on the side beams B and R on both sides as compared with the center beam G at the center.

However, in an actual circuit operation, since the correction current Ih flows simultaneously through the six coils L1 to L6, the correction magnetic field formed by the correction coil 21 is the same as the quadrupole magnetic field φ1 and the dipole magnetic field φ2. The result is a composite. Of these, the quadrupole magnetic field φ1 is in the form of a pincushion and the dipole magnetic field φ2 is in the form of a barrel, so that the combined magnetic field is such that each of the magnetic fields φ1, φ2 has three electron beams B,
It complements the strength of the action on G and R.

As a result, the correction magnetic field by the correction coil 21 becomes a substantially uniform magnetic field φ3 for vertically deflecting the three electron beams B, G, R upward as shown in FIG. The correction magnetic field φ3 is such that three magnetic poles near one side beam R are N poles and three magnetic poles near the other side beam B are S poles.
And a hexapole magnetic field.

On the other hand, when the direction of the correction current Ih flowing through the correction coil 21 is reversed, the coils L2, L2
3, L5, L6 is a quadrupole magnetic field (pin cushion type) opposite to the quadrupole magnetic field φ1 shown in FIG. 5A, and the magnetic field formed by the coils L1, L4 is as shown in FIG. 2 opposite to the dipole magnetic field φ2 shown in FIG.
It becomes a dipole magnetic field (barrel type). Therefore, the correction magnetic field formed by the correction coil 21 is a hexapole magnetic field (substantially uniform magnetic field) opposite to the correction magnetic field φ3 shown in FIG.
The three electron beams B, G, and R are vertically deflected downward by the action of the magnetic field.

For this reason, for example, in the circuit configuration shown in FIG. 4, if the vertical image bending distortion occurs when the slider S of the variable resistor VR is at the center position, the distortion shape is a pincushion type. Or the barrel type, the slider S of the variable resistor VR is appropriately moved.

Specifically, when the vertical image bending distortion generated on the screen is a pincushion type image distortion, the slider S of the variable resistor VR is moved to one side (the fixed resistor R3 side). . Then, in the first half of the vertical deflection cycle, the correction current Ih flows through the correction coil 21 in the direction of the arrow, and in the second half of the vertical deflection cycle, the correction current Ih flows through the correction coil 21 in the direction opposite to the direction of the arrow. At this time, since the direction of the correction magnetic field φ3 formed by the correction coil 21 is the same as the direction of the vertical deflection magnetic field by the pair of vertical deflection coils 17, 17, the incident angle of the electron beam on the phosphor screen becomes relatively large. . Therefore, by adjusting the position of the slider S of the variable resistor VR (the amount of the correction current Ih flowing through the correction coil 21) in accordance with the degree of the pincushion-type image distortion, the pincushion-type image distortion is appropriately reduced. It becomes possible to correct.

On the other hand, when the vertical image bending distortion generated on the screen is a barrel-shaped image distortion, the slider S of the variable resistor VR is moved to the other side (the fixed resistor R4 side). Then, in the first half of the vertical deflection cycle, the correction current Ih flows through the correction coil 21 in a direction opposite to the direction of the arrow, and in the second half of the vertical deflection cycle, the correction current Ih flows through the correction coil 21 in the direction of the arrow. At this time, since the direction of the correction magnetic field φ3 formed by the correction coil 21 is opposite to the direction of the vertical deflection magnetic field generated by the pair of vertical deflection coils 17, 17, the incident angle of the electron beam on the phosphor screen becomes relatively small. . Therefore, the position of the slider S of the variable resistor VR (the correction coil 2) is adjusted according to the degree of the barrel-shaped image distortion.
By adjusting the amount of the correction current Ih flowing in
It is possible to appropriately correct barrel-shaped image distortion.

In the state where the pincushion-type image distortion has been corrected as described above, the thermistor T
m decreases, the fixed resistance R3 of the variable resistor VR decreases.
The combined resistance of the fixed resistor R3 and the thermistor Tm decreases due to the resistance on the side, and the amount of the correction current Ih flowing through the correction coil 21 increases. On the other hand, with the barrel-shaped image distortion corrected as described above, thermistor T
m decreases, the fixed resistance R3 of the variable resistor VR decreases.
The combined resistance of the fixed resistor R3 and the thermistor Tm decreases by the amount of the resistor on the side, and the amount of the correction current Ih flowing through the correction coil 21 decreases.

As described above, in the present embodiment, the vertical deflection magnetic field generated by the pair of vertical deflection coils 17 and 17 and the correction magnetic field generated by the correction coil 21 are formed in the same direction within the vertical deflection period (ie, the pincushion type). In the case where the slider S of the variable resistor VR is moved to the fixed resistor R3 side from the center position to correct the image distortion described above, the thermistor Tm increases the amount of the correction current Ih flowing through the correction coil 21. Operates. When the vertical deflection magnetic field and the correction magnetic field are formed in opposite directions within the vertical deflection period (ie, in order to correct barrel-shaped image distortion, the slider S of the variable resistor VR is set at a fixed resistance R4 higher than the center position. Side), the thermistor Tm operates so that the amount of the correction current Ih flowing through the correction coil 21 decreases.

Thus, in the state where the pincushion-type image distortion is corrected, the resistance value of the thermistor Tm decreases due to the temperature rise, and the correction magnetic field φ3 of the correction coil 21 formed in the same direction as the vertical deflection magnetic field. Will be strengthened. Further, in a state where the barrel-shaped image distortion is corrected, the thermistor T is caused by the temperature rise.
As the resistance value of m decreases, the correction magnetic field φ3 of the correction coil 21 formed in the direction opposite to the vertical deflection magnetic field is weakened.

Therefore, when the resistance value of the thermistor Tm decreases due to the temperature rise, the incident angle of the electron beam on the phosphor screen becomes relatively large (the direction in which the amount of vertical pincushion distortion decreases). Thus, the intensity of the correction magnetic field φ3 by the correction coil 21 changes. Therefore, even if the magnetic field of the pair of ferrite magnets weakens due to a temperature rise, the strength of the correction magnetic field φ3 changes in a manner that complements the weakening, so that the occurrence of upper and lower pincushion distortion can be reliably prevented. .

In this embodiment, among the six coils L1 to L6 constituting the correction coil 21, the coils L2, L3, L5 and L6 form a pincushion-type four coil.
While the quadrupole magnetic field φ1 is formed, the barrel-shaped double pole magnetic field φ2 is formed by the coils L1 and L2, thereby obtaining a substantially uniform correction magnetic field (six-pole magnetic field) φ3. Three emitted electron beams B,
The correction magnetic field φ3 can be uniformly applied to G and R, respectively. As a result, it is possible to correct the vertical image distortion without changing the convergence.

In the above-described embodiment, the thermistor Tm having the characteristic that the resistance value decreases as the temperature rises.
However, the present invention is not limited to this, and it is also possible to use a thermistor having a characteristic in which the resistance value increases with an increase in temperature, that is, a thermistor whose resistance has a positive temperature coefficient. However, when such a configuration is adopted, when the slider S of the variable resistor VR is moved from the center position to one side (the fixed resistor R3 side to which the thermistor Tm is connected in parallel) and the balance of the bridge is lost. It is necessary to set the correction magnetic field φ3 of the correction coil 21 in a direction opposite to the vertical deflection magnetic field generated by the pair of vertical deflection coils 17, 17.

The reason is that the operating principle of the thermistor Tm serving as a temperature compensating element is that the vertical deflection magnetic field by the pair of vertical deflection coils 17 and 17 and the correction magnetic field by the correction coil 21 are formed in the same direction within the vertical deflection period. In this case, the amount of the correction current Ih flowing through the correction coil 21 operates so as to increase as the temperature rises. If the vertical deflection magnetic field and the correction magnetic field are formed in the reverse direction within the vertical deflection cycle, the correction current Ih flows through the correction coil 21. This is because it is necessary to operate such that the amount of the correction current Ih decreases with an increase in temperature. The principle of operation of the thermistor Tm is commonly applied to the correction coil 21 regardless of the manner in which the thermistor Tm is connected.

In the above-described embodiment, the correction circuit 24 is connected in series to the pair of vertical deflection coils 17, 17, so that the correction current Ih is supplied to the correction coil 21 using the vertical deflection circuit as a common current source. However, the present invention is not limited to this, and a configuration in which the correction current Ih is supplied to the correction coil 21 by current supply means different from the vertical deflection circuit may be used.

Further, in the above-described embodiment, a substantially uniform magnetic field is obtained by using the correction magnetic field φ3 of the correction coil 21 as a hexapole. By increasing the number, octupole and 10-pole magnetic fields may be employed, thereby making it possible to realize a correction magnetic field close to perfect uniformity. However, in order to obtain a substantially uniform magnetic field by combining (synthesizing) a pincushion-type magnetic field and a barrel-type magnetic field, the hexapole has the minimum number of poles.
From the viewpoint of simplifying the circuit configuration, it is desirable to employ a hexapole.

Further, a pair of C-shaped magnetic bodies 22A and 22B
By winding one coil in place of the coils L2 and L3 and one coil in place of the coils L5 and L6 on each intermediate portion (on the Y-axis), the total number of coils is reduced. A uniform correction magnetic field (six-pole magnetic field) can be formed. In this case, the number of coils constituting the correction coil 21 is four in total.

[0056]

As described above, according to the present invention, when the vertical deflection magnetic field by the pair of vertical deflection coils and the correction magnetic field by the correction coil are formed in the same direction within the vertical deflection period, the temperature due to the temperature rise is increased. The amount of correction current flowing through the correction coil is increased by a change in the resistance value of the compensating element. If the vertical deflection magnetic field and the correction magnetic field are formed in opposite directions within the vertical deflection cycle, the resistance value of the temperature compensating element due to temperature rise By reducing the amount of the correction current flowing through the correction coil due to the change, the intensity of the correction magnetic field is increased in a direction in which the angle of incidence of the electron beam on the phosphor screen becomes relatively large (a direction in which the amount of vertical pincushion distortion decreases). Can be changed. As a result, even when the magnetic field of the pair of ferrite magnets weakens due to the temperature rise, the magnetic field strength of the correction coil changes in a manner that complements the weakening, so that the occurrence of upper and lower pincushion distortion due to the temperature rise is reliably prevented. It becomes possible.

[Brief description of the drawings]

FIG. 1 is a schematic perspective view showing an overall image of a cathode ray tube according to the present invention.

FIG. 2 is a side view including a partially broken surface of the deflection yoke according to the present invention.

FIG. 3 is a diagram illustrating an arrangement state of a correction coil according to the embodiment of the present invention.

FIG. 4 is a circuit diagram showing a coil connection state in the embodiment of the present invention.

FIG. 5 is a diagram illustrating a pincushion type and a barrel type magnetic field formed by a correction coil.

FIG. 6 is a diagram illustrating a correction magnetic field formed by a correction coil.

FIG. 7 is a diagram for explaining a principle of correcting a vertical image bending distortion by a correction coil.

FIG. 8 is a diagram illustrating a defect of a display image due to a temperature rise.

[Explanation of symbols]

15: deflection yoke, 17: vertical deflection coil, 21: correction coil, 22A, 22B: C-shaped magnetic body, 23A, 23B
... T-shaped magnetic material, 24 ... correction circuit, L1 to L6 ... coil,
R1 to R4: fixed resistance, Tm: thermistor, VR: variable resistance

Claims (4)

[Claims] A pair of vertical deflection coils for forming a vertical deflection magnetic field; a correction coil for forming a correction magnetic field for vertically deflecting an electron beam at a rear end side of a deflection yoke; Current supply means for supplying a correction current of a sawtooth wave; a characteristic having a characteristic in which a resistance value changes according to a temperature rise; and a vertical deflection magnetic field by the pair of vertical deflection coils and a correction magnetic field by the correction coil within the vertical deflection period. Are formed in the same direction, the operation is performed so that the amount of the correction current flowing through the correction coil increases with an increase in temperature, and the vertical deflection magnetic field and the correction magnetic field are formed in opposite directions within the vertical deflection cycle. A temperature compensating element that operates so that the amount of the correction current flowing through the correction coil decreases with an increase in temperature. H. 2. The deflection yoke according to claim 1, further comprising current adjusting means for adjusting the amount and direction of the correction current flowing through the correction coil. 3. A coil for forming a pincushion-type magnetic field for vertically deflecting an electron beam;
2. A coil for forming a barrel-shaped magnetic field for vertically deflecting an electron beam.
A deflection yoke as described. 4. A pair of vertical deflection coils for forming a vertical deflection magnetic field, a correction coil for forming a correction magnetic field for vertically deflecting an electron beam at a rear end side of a deflection yoke, and a vertical deflection period corresponding to the correction coil. Current supply means for supplying a correction current of a sawtooth wave; a characteristic having a characteristic in which a resistance value changes according to a temperature rise; and a vertical deflection magnetic field by the pair of vertical deflection coils and a correction magnetic field by the correction coil within the vertical deflection period. Are formed in the same direction, the operation is performed so that the amount of the correction current flowing through the correction coil increases with an increase in temperature, and the vertical deflection magnetic field and the correction magnetic field are formed in opposite directions within the vertical deflection cycle. And a temperature compensation element that operates so that the amount of the correction current flowing through the correction coil decreases with a rise in temperature. Characteristic display device.