JPH10290468A - Degaussing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a degaussing device for the magnetism on a magnetized object such as a cathode ray tube and a television receiver in a short time efficiently. SOLUTION: An AC degaussing voltage V2 outputted from a switching section 18 of an AC switching regulator 15 is applied to a degaussing coil 12, a pulse width modulation section 21 conducts pulse width modulation in response to a signal level of an output waveform signal S1 depending on a capacitor discharge characteristic outputted from a CR time constant circuit section 17, and the switching section 18 is operated by a high frequency pulse signal P1 outputted from the pulse width modulation section 21 to attenuate the AC degaussing voltage V2.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a degaussing device for demagnetizing magnetism of a magnetized object. For example, in the manufacturing process of a cathode ray tube or a television receiver, the cathode ray tube or the television receiver is unnecessarily magnetized. The present invention relates to a degaussing device for degaussing generated magnetism.

[0002]

2. Description of the Prior Art Unnecessary magnetism is magnetized in a cathode ray tube or a television receiver during the manufacturing process, which causes problems such as a reduction in the sharpness of a screen and a screen with a lot of color unevenness. For this reason, various types of demagnetizing means are used to demagnetize the magnetization.

One type of degaussing means utilizes a magnetic force due to a change in distance by gradually moving a degaussing coil to which a constant AC degaussing voltage is applied from a cathode ray tube or a television receiver. The degaussing means may be performed manually or mechanically.

Further, there is a type in which a positive characteristic thermistor is connected in series to a degaussing coil for applying an AC degaussing voltage, and the magnetic force is changed by using the resistance change of the thermistor to degauss. In addition, there is a method in which the voltage value of the AC demagnetizing voltage supplied to the degaussing coil is demagnetized by changing the voltage value using phase control by a thermistor. The degaussing means for changing the voltage of the degaussing coil by using a thermistor or a thyristor
A degaussing coil is fixedly installed near a CRT or a television receiver.

[0005]

The degaussing means for gradually moving the degaussing coil away from the cathode ray tube or the television receiver by hand requires a relatively long degaussing time, causes variations in the degaussing result, and also requires the operator More effort.

The degaussing means for mechanically separating the degaussing coil has no variation in the degaussing result, but requires a long degaussing time and requires a large degaussing device.

The demagnetizing means using the resistance change of the thermistor has a small power amount, so that when the magnetization is large, the demagnetizing state is insufficient. The degaussing means using the thyristor phase control can increase the amount of electric power, but cannot finely control the AC degaussing voltage applied to the degaussing coil.

In view of the above circumstances, the present invention provides a degaussing apparatus that can efficiently demagnetize magnetized magnetized objects such as cathode ray tubes and television receivers in a short time, and can automate the degaussing. The purpose is to provide.

[0009]

According to the present invention, there is provided a degaussing apparatus for supplying an AC degaussing voltage to a degaussing coil and degaussing a magnetized object by a magnetic force generated in the degaussing coil. Means for gradually attenuating the AC degaussing voltage supplied to the AC degaussing voltage from a predetermined voltage value, and reducing each instantaneous voltage of the AC degaussing voltage at the same decay rate as compared to the immediately preceding instantaneous voltage. A degaussing device with features is proposed.

[0010]

This degaussing device gradually attenuates the AC degaussing voltage supplied to the degaussing coil, and this attenuation reduces each instantaneous voltage at the same decay rate as compared to the immediately preceding instantaneous voltage.

Therefore, during the decay of the AC demagnetizing voltage, the succeeding instantaneous voltage decreases more than necessary in comparison with the preceding instantaneous voltage, and conversely, the succeeding instantaneous voltage increases in comparison with the preceding instantaneous voltage. Nothing to do. For this reason, the magnetic force of the degaussing coil effectively demagnetizes the magnetism of the magnetized object, and ensures that unnecessary magnetism is demagnetized.

[0012]

Next, an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a perspective view showing a degaussing device for demagnetizing unnecessary magnetism magnetized on the cathode ray tube during the production process of the cathode ray tube.

As shown, the degaussing device includes a degaussing voltage output device 11 and a degaussing coil 12. The degaussing coil 12 is formed by winding a conductive wire by 150 to 250 turns to form a frame-shaped coil. The degaussing coil 12 is provided at a predetermined position facing the cathode ray tube 14 sent by the belt conveyor 13 at a small interval.

The degaussing coil 12 has a frequency of 5
An AC degaussing voltage of 0 Hz or 60 Hz is supplied from the degaussing voltage output unit 11, and the AC degaussing voltage is configured to attenuate from a predetermined voltage (for example, 85 volts) to several millivolts.

In this embodiment, when one of the cathode ray tubes 14 sent by the belt conveyor 13 is sent to a position facing the degaussing coil 12, the belt conveyor 1
3 is temporarily stopped, and the degaussing voltage output unit 11 is operated in conjunction with the stop, and the AC degaussing voltage is supplied to the degaussing coil 12.

Thus, the magnetization of the cathode ray tube 14 facing the degaussing coil 12 is demagnetized by the magnetic force of the degaussing coil 12. After the degaussing operation is completed, the belt conveyor 13
Is started again, the CRT 14 to be sent next is demagnetized in the same manner as described above, and thereafter, the CRT 14 sequentially sent is demagnetized.

FIG. 2 is a block diagram showing an example of a circuit of the demagnetizing voltage output device 11. The outer dotted line indicates the demagnetizing voltage output device 11.
The inner dotted lines indicate the AC switching regulators 15, respectively, and the control unit 16 and the CR time constant circuit unit 17
Represents an output waveform signal portion.

The AC switching regulator 15 comprises a switching section 18 including a filter circuit, an output voltage detecting section 19 including an AC / DC conversion circuit, a comparing and amplifying section 20, and a pulse width modulating section 21.

The switching unit 18 receives an AC voltage V1 having a frequency of 50 Hz or 60 Hz from the AC power supply 22, switches the AC voltage in accordance with the high-frequency pulse signal P1, and supplies an AC degaussing voltage V2 to the degaussing coil 12.

More specifically, the switching section 18 receives an AC voltage V1 as shown in FIG. 3A, and converts the AC voltage V1 according to the high-frequency pulse signal P1.
Switching is performed as shown in FIG. The AC demagnetizing voltage V whose amplitude is changed as shown in FIG.
2 is output.

The output voltage detecting section 19 includes the switching section 1
8 detects the AC demagnetizing voltage V2, and sends the detection signal S0 to the comparison amplifier 20. Specifically, the AC demagnetizing voltage V2 output from the switching unit 18 becomes an attenuation voltage as shown in FIG. 4A, and the output voltage detecting unit 19 receives the AC demagnetizing voltage V2 and performs rectification and smoothing. This is an AC / DC conversion circuit that outputs the detection signal S0 shown in FIG.

The comparison amplifying section 20 outputs the detection signal S0
Is input to the first input terminal, the output waveform signal S1 is input to the second input terminal, the output waveform signal S1 is compared and amplified, and the amplified signal S3 shown in FIG. 4D is output. The output waveform signal S1 is output from the CR time constant circuit section 17, and this signal S1 is
As shown in FIG. 4 (c), this is for determining the above-described attenuation characteristic of the AC demagnetizing voltage V2.
1 is a constant voltage signal, and after time T1 is an attenuated voltage signal according to the discharge characteristics of the capacitor.

The pulse width modulation section 21 receives the amplified signal S3, converts the amplified signal S3 into pulses, performs pulse width modulation, and sends the output high frequency pulse signal P1 to the switching section 18. The pulse width modulation performed here is a width modulation in which the higher the level of the amplified signal S3, the wider the pulse width, and the lower the level, the narrower the pulse width. A high-frequency pulse signal P1 as shown is output.

On the other hand, the CR time constant circuit section 17 is controlled by the control section 16 to output the output waveform signal S1.
Is output. The control unit 16 includes a timer circuit, and the CR time constant circuit unit 1 is controlled according to the timer time.
7 controls the output waveform signal S1 to start outputting and the output waveform signal S1 to transition to the attenuation voltage signal.

FIG. 5 is a discharge type circuit example of the CR time constant circuit section 17, and FIG. 6 is a time chart showing the operation thereof. The switch 23 is controlled by the control unit 16 at time T.
The switch is turned on at 0 and turned off at time T1 when the timer time elapses. Note that the switch 23 can be configured as a semiconductor switch.

The capacitor 24 is connected to the switch 23
Is turned on by the DC power supply DC / V via the current limiting resistor 25, and when the switch 23 is turned off, the electric charge is discharged via the discharge resistor 26 to output an attenuated voltage signal of the output waveform signal S1.

FIG. 7 is an example of a charging type circuit of the CR time constant circuit section 17, and FIG. 8 is a time chart showing the operation thereof. In this circuit example, the switch 27 is turned off by the control unit 16 at the time T0 when the output of the output waveform signal S1 starts, and turned on at the time T1 when the output of the signal S1 starts to decay.
And an operational amplifier 28 that inverts the charging voltage of the capacitor 24 and outputs the output waveform signal S1.

The degaussing voltage output device 11 configured as described above
Outputs an AC demagnetizing voltage V2 shown in FIG. 9A, and supplies the AC demagnetizing voltage V2 to the degaussing coil 12. And
The AC demagnetizing voltage V2 is a constant voltage at times T0 to T1 and an attenuated voltage after time T1, and the AC demagnetizing voltage V2 is, as shown in FIG.
V2 + 2, V2 + 3, V2 + 4, V2 + 5 ...
And decreases at the same decay rate as compared to the instantaneous voltage immediately before.

That is, the attenuation rate = V2 + 2 / V2 + 1 = V
2 + 3 / V2 + 2 = V2 + 4 / V2 + 3 = V2 + 5 / V
2 + 4..., And each instantaneous voltage decreases at the same decay rate, and finally decreases to almost zero voltage.
As a result, the magnetized cathode ray tube 14 is very effectively demagnetized by the magnetic force of the degaussing coil 12.

According to the experimental results, when the AC power supply 22 of 50 Hz and 100 V is used, the maximum output voltage of the AC demagnetizing voltage V2 is about 85 V, the final voltage is several millivolts, and the demagnetization time is about 3.5 seconds. Was confirmed to be able to be reliably demagnetized.

Although the preferred embodiment has been described above, the switching unit 18 has a duty ratio of 0 to 100%.
Can be controlled, the variable range of the output AC demagnetizing voltage V2 can be widened, and the use of the switching section 18 reduces power loss and increases the output voltage.

If a capacitor is connected in parallel with the degaussing coil 12, the reactive current of the degaussing coil 12 is canceled out, so that the degaussing coil 12 can be enlarged accordingly.
Further, the AC degaussing current V2 supplied to the degaussing coil 12 becomes a sine wave having positive and negative symmetry in the entire range, and attenuates from the maximum output voltage to the minimum output voltage with a voltage curve ideal for degaussing.

[0033]

As described above, the degaussing device according to the present invention supplies the degaussing coil with an AC degaussing voltage in which each instantaneous voltage decreases at the same decay rate as compared to the immediately preceding instantaneous voltage. Since the magnetized object that is unnecessarily magnetized is demagnetized by the generated magnetic force, the demagnetizing effect is high and the demagnetization can be reliably performed in a short time.

Further, this degaussing device has a simple configuration and can be automated, so that it is a practically excellent degaussing device.

[Brief description of the drawings]

FIG. 1 is a perspective view of a degaussing device showing a state in which magnetism magnetized on a cathode ray tube is degaussed.

FIG. 2 is a block diagram illustrating a circuit example of a degaussing voltage output device provided in the degaussing device.

FIG. 3 is a waveform diagram for explaining an operation of a switching unit provided in the demagnetizing voltage output device described above.

FIG. 4 is a waveform diagram showing an output waveform of the degaussing voltage output device and a signal waveform of each section of the circuit of the degaussing voltage output device.

FIG. 5 is a diagram showing a circuit example of a CR time constant circuit unit provided in the degaussing voltage output device.

FIG. 6 is a time chart showing the operation of the CR time constant circuit section of FIG. 5;

FIG. 7 is a diagram showing another circuit example of the CR time constant circuit section.

8 is a time chart showing the operation of the CR time constant circuit section shown in FIG.

FIG. 9 is a waveform diagram showing an AC degaussing voltage output from the degaussing voltage output device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 11 Degaussing voltage output device 12 Degaussing coil 15 AC switching regulator 16 Control part 17 CR time constant circuit part 18 Switching part 19 Output voltage detecting part 20 Comparative amplification part 21 Pulse width modulation part 22 AC power supply

Claims (1)

[Claims] In a degaussing device for supplying an AC degaussing voltage to a degaussing coil and degaussing a magnetized object by a magnetic force generated in the degaussing coil, the AC degaussing voltage supplied to the degaussing coil is gradually attenuated from a predetermined voltage value. And a means for reducing each instantaneous voltage of the AC demagnetizing voltage at the same decay rate as compared to the immediately preceding instantaneous voltage.