JP2002230706A - Demagnetizing device for magnetic tape - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a demagnetizing device for the magnetic tape of a high coercive force designed to record digital data at a high density, capable of performing good demagnetization even when there is slight variance in magnetic characteristics, and obtaining a specified demagnetization characteristic even in a small recording track width. SOLUTION: First and second eraser heads 3 and 4, a recording head 5 and a reproducing head 6 are arrayed from an upstream side along the traveling direction of a magnetic tape 1. The first eraser head 3 magnetizes the magnetic tape 1 in a first direction. The second eraser head 4 magnetizes the magnetic tape 1 in a second direction. The recording head 5 records a testing signal. The reproducing head 6 reproduces the recorded testing signal. An erasing current control circuit 8 controls a current flowing to the second eraser head 4 according to the reproduced testing signal.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic tape degaussing device for demagnetizing a magnetic tape by applying a magnetic field to a running magnetic tape.

[0002]

2. Description of the Related Art Magnetic tapes are widely used as media for recording data in computers and the like. this is,
This is because a magnetic tape is a medium suitable for recording a large amount of data. Various magnetic materials are used for the magnetic tape depending on required recording characteristics, and each magnetic tape has a unique magnetic characteristic. In particular, magnetic tapes designed for high-density digital recording require a higher coercive force than magnetic tapes for recording analog signals.

In general, information is recorded and reproduced on a magnetic tape by a magnetic tape device connected to a computer. The magnetic tape used in the magnetic tape device needs to be supplied in a demagnetized state at an early stage. The demagnetized state is a state in which the magnetic material applied or deposited on the magnetic tape is not magnetized in a specific direction. If the magnetic tape is magnetized in a specific direction when used in a magnetic tape device, a failure may occur when recording or reproducing data with the magnetic tape device.
On the other hand, at the stage of manufacturing the magnetic tape, the magnetic tape may not be in the demagnetized state due to a process such as an orientation for aligning the direction of the magnetic substance applied or deposited on the magnetic tape, or various other factors. Therefore, the manufacturer of the magnetic tape must include a step of demagnetizing the magnetic tape in the step of manufacturing the magnetic tape.

[0004] The step of demagnetizing the magnetic tape is selected from several means depending on whether the coercive force of the magnetic tape is low, medium or high. In the case where the coercive force is low (a magnetic tape having a low coercive force), such as a magnetic tape for analog recording, a demagnetized state can be realized by various methods. The most typical degaussing method is to pass a magnetic tape in an alternating magnetic field while it is wound on a reel at the stage of producing the magnetic tape. In this case, demagnetization can be performed collectively in a short time without running the magnetic tape. However, when the coercive force of the magnetic tape is high, it is necessary to generate a strong magnetic field, and it is difficult to completely erase the magnetic tape.

When the coercive force is so high that complete erasure cannot be performed even when the magnetic tape is passed through a magnetic field while being wound on a reel (a magnetic tape having a medium coercive force), the magnetic tape is actually run and the erasing head is used. Degauss. In this case, a high-frequency current is applied to the erase head to perform so-called AC erasing.
However, when the coercive force of the magnetic tape is higher (a magnetic tape having a high coercive force), AC erasing by the erasing head causes a problem. A magnetic material such as ferrite constituting a magnetic head has a property that the magnetic permeability decreases as the frequency increases.
Therefore, in order to obtain an erasing magnetic field strong enough to demagnetize a magnetic tape having a high coercive force, it is necessary to supply a large high-frequency current to the erasing head. Then, the temperature of the erasing head rises, and it becomes impossible to actually contact the magnetic tape.

Therefore, various techniques have been developed to demagnetize a magnetic tape having a high coercive force.
For example, Japanese Utility Model Publication No. 58-39541 (G11B 5/0)
0) shows a technique of arranging three magnetic heads along the running direction of a magnetic tape. The technique shown here is based on the first head being direct current, the second head being direct current,
Are erased by alternating current. The first head causes the magnetic material of the magnetic tape to be strongly DC-magnetized in the first direction and saturates, the second head weakly DC-magnetizes in the second direction, and performs AC erasing by the third head. Degaussing completely. By doing so, the magnetic tape that has passed through the second head can be expected to be in a state close to a demagnetized state, and the AC current that flows through the third head can be reduced. According to the technology described herein, since the current flowing through the first and second heads may be DC, the problem of heat generation of the head itself does not occur, and the AC current flowing through the third erasing head is also reduced. Therefore, the problem of heat generation of the head is considered to be reduced.

In the technique disclosed in Japanese Utility Model Publication No. 54-4972, a first DC erasing head and a second DC head are arranged in a running direction of a magnetic tape. Assuming that the width of the recording track of the signal on the magnetic tape is 1, the erasing width of the first erasing head is 1, the erasing width of the second erasing head is と し, and the magnetization directions of the two erasing heads are Is reversed. In this way, as long as the data is recorded and reproduced by the recording head or the reproducing head having the track width of 1, the same effect as when the magnetic tape is completely demagnetized can be obtained. According to the technology described here, since the current flowing to the erasing head may be DC, even if a large current flows, it is considered that there is almost no problem of heat generation.

If the above-mentioned conventional technology is used, a demagnetized state can be realized even with a magnetic tape having a high coercive force to some extent, but it becomes difficult to realize as the coercive force increases. First, in the first example described above, it is particularly difficult to select a numerical value of the current flowing through the second head. The reason for this is that the magnetic properties of magnetic tapes are subject to manufacturing variations, and the magnetic properties of magnetic materials for magnetic tapes designed for digital recording are different from those for analog tapes. This is because a so-called BH curve becomes a curve close to a rectangle. For this reason, it is difficult to set the current flowing through the second magnetic head. In the second example, a magnetic tape designed for high-density recording has a very narrow track width, which makes it difficult to manufacture the erase head itself.

[0009]

SUMMARY OF THE INVENTION The present invention relates to a magnetic tape having a high coercive force, capable of performing good degaussing even if there is a variation in magnetization characteristics, and providing a predetermined tape even if the width of a recording track is minute. Provided is a degaussing device capable of obtaining degaussing characteristics.

[0010]

According to the present invention, there is provided a first erasing head and a second erasing head provided downstream of the first erasing head from the upstream side along the running direction of the magnetic tape. A recording head provided downstream of the second erasing head; a reproducing head provided further downstream of the recording head; a DC power supply circuit for supplying a DC current to the first erasing head; A test signal generating circuit for supplying a test signal; and an erase current control circuit for supplying a DC current to the second erase head based on the reproduced signal reproduced by the read head. Supplies a DC current so that the magnetic tape is magnetized in a first direction, and supplies a DC current to the second erasing head so that the magnetic tape is magnetized in a second direction; H By supplying a test signal to the magnetic tape, a test signal is recorded on the magnetic tape, a test signal recorded on the magnetic tape is reproduced by the reproduction head, and the test signal reproduced by the reproduction head is 2 is a magnetic tape degaussing apparatus characterized in that the value of the current flowing through the erasing head is determined.

The erase current control circuit adjusts a current flowing through the second erase head so that a peak voltage of a signal in a positive direction and a peak voltage in a negative direction of a signal reproduced from the reproduction head are equal. And a demagnetizing device for a magnetic tape.

Further, the erasing current control circuit controls a current flowing through the second erasing head so that the amplitude of a signal reproduced from the reproducing head is maximized. It is what it was.

[0013]

FIG. 1 is a block diagram showing an embodiment of the present invention. 1 is a magnetic tape. The magnetic tape 1 runs in the direction shown by the arrow 2. 3 is a first erasing head, 4 is a second erasing head, 5 is a recording head, and 6 is a reproducing head. The magnetic tape 2 first contacts the first erasing head 3, then contacts the second erasing head 4, then the recording head 5, and then the reproducing head 6. First erase head 3 and second erase head 4
May be a magnetic head designed for DC erasing with one or more gaps. The recording head 5 may be a recording head having one gap. The reproducing head 6 may be a reproducing head having one gap for detecting a change in magnetism by using a coil or a magnetoresistive element (MR).

Reference numeral 7 denotes a DC power supply. The power supply 7 supplies a direct current to the first erase head. The magnitude of the current is such that the magnetic tape 1 is completely magnetized in one direction. 8
Denotes an erase current control circuit. The erase current control circuit 8 supplies a DC current to the second erase head 4. Magnetic tape 1
, The directions of the magnetic fields of the first erasing head 3 and the second erasing head 4 are opposite. The magnitude of the current flowing through the second erasing head 4 is such that the magnetic tape 1 is demagnetized.
The current flowing through the second erase head 4 is controlled by taking measures described later.

Reference numeral 9 denotes a test signal generation circuit. FIG.
(A) is an example of a test signal generated by the test signal generation circuit 9. In the test signal shown in FIG. 2A, the vertical axis represents current, and the horizontal axis represents time. The current indicated by 0 is 0 amps. The test signal generated from the test signal generating circuit 9 may be a square wave having a constant period with a positive / negative symmetry about 0 ampere and a constant period. However, as described later, the waveform of the test signal generated by the test signal generation circuit is not limited to a square wave, and may be another waveform.

FIG. 2B, FIG. 2C and FIG.
7 is a waveform reproduced by the reproducing head 6. Each playback waveform is shown in FIG.
The test signal shown in FIG. The vertical axis indicates the voltage of the signal reproduced by the reproducing head 6, and the horizontal axis indicates time. FIG.
FIG. 3B shows a state in which the current flowing through the second erase head 4 shown in FIG. 1 is optimal. FIG. 2C shows a case where the current flowing through the second erase head 4 is excessive, and FIG. 2D shows a case where the current flowing through the second erase head 4 is too small. As shown in FIG. 2B, if the current flowing through the second erase head 4 is appropriate, the voltage on the vertical axis is centered on 0 volt,
The maximum amplitude of the signal is almost the same as the positive and negative. On the other hand, FIG.
As shown in FIG. 2D, when the current flowing through the second erasing head 4 is not appropriate, the sign becomes asymmetric. This is because the recording state of the test signal is biased when the magnetic tape 1 is magnetized in either direction at the recording head 5.

FIG. 3 is a block diagram showing a configuration of the erase current control circuit 8. As shown in FIG. 10 is an input terminal, and 11 is an output terminal. The output of the reproducing head 6 is connected to the input terminal 10, and the second erasing head 4 is connected to the output terminal 11. 12 is an amplifier circuit. Reference numerals 13 and 14 are peak detection circuits. 13 detects the positive peak voltage of the signal output from the amplifier circuit 12, and 14 detects
Detects the negative peak voltage. Peak detection circuit 13, 1
4 may be a normal integration circuit. Reference numeral 15 denotes a polarity inversion circuit, and reference numeral 16 denotes a comparison circuit. The comparison circuit 16 compares the outputs of the peak detection circuits 13 and 14. 17 is a current control circuit. The current control circuit 17 controls the second erase head 4
To control the current flowing through the second erase head so that the absolute value of the output of the comparison circuit 16 is minimized.

FIG. 4 is a block diagram showing the configuration of the erase current control circuit 8, showing another configuration. As shown in FIGS. 2B, 2C and 2D, the signal reproduced by the reproducing head 6 is detected as the sum of the absolute values of both positive and negative peaks, that is, the magnitude of the signal amplitude. Is also possible. As shown in FIGS. 2B, 2C, and 2D, when the DC current flowing through the second erasing head 4 is appropriate, the amplitude of the signal output from the reproducing head 6 becomes maximum. In FIG. 4, reference numeral 18 denotes an input terminal;
Is an output terminal. The input terminal 18 is connected to the reproducing head 6, and the output terminal 19 is connected to the second erasing head 4. Reference numeral 20 denotes a signal amplification circuit, and reference numeral 21 denotes a rectification circuit. 22 is a sample and hold circuit. The rectifier circuit 21 rectifies the signal of the amplifier circuit 20 and converts the signal into a DC signal. The sample hold circuit 22 maintains the peak voltage of the output signal of the rectifier circuit 21. The sample hold circuit 22 outputs a signal corresponding to the amplitude of the signal output from the reproducing head 6. 23 is a current control circuit. The current control circuit 23 controls the DC current flowing through the second erase head 6 so that the output of the sample hold circuit 22 becomes maximum.

Further, as another embodiment of the present invention,
First erase head 3 and second erase head 4 shown in FIG.
Can be considered as one. That is, as shown in FIG. 5, the same effect can be obtained even when the integrated erase head 24 is used. The erase head 24 shown in FIG. 5 has a first gap 25 and a second gap 26. 27 is a first coil, and 28 is a second coil. First
The gap 25 and the first coil 27 of FIG.
Corresponding to the erase head 3. Also, the second gap 26
And the second coil 28 are connected to the second erase head 4 shown in FIG.
Is equivalent to Therefore, the first coil 27 is connected to the DC power supply circuit 7, and the second coil 28 is connected to the erase current control circuit 8. Thus, the integrated erase head 2
No. 4 is useful when downsizing the entire magnetic tape degaussing device.

Further, as another embodiment, the recording head 5 and the reproducing head 6 shown in FIG. 1 can be considered as one recording and reproducing head. The recording head 5 and the reproducing head 6 can have substantially the same structure.
Therefore, it is also possible to adopt a configuration in which one head is used first as a recording head, and then the magnetic tape is run in the opposite direction and used as a reproducing head. This makes it possible to reduce the size of the entire magnetic tape degaussing device.

As described above, according to the magnetic tape degaussing apparatus embodying the present invention, good degaussing can be performed even if the magnetic properties of the magnetic tape vary.

[0022]

The present invention relates to a magnetic tape having a high coercive force,
There is an effect that a good degaussing can be performed even if the magnetization characteristics vary, and a degaussing device that can obtain predetermined degaussing characteristics even when the width of the recording track is minute can be realized.

[Brief description of the drawings]

FIG. 1 is a block diagram showing an embodiment.

FIG. 2 is a diagram showing waveforms of a test signal and a reproduction signal from a reproduction head.

FIG. 3 is a block diagram showing a configuration of an erase current control circuit.

FIG. 4 is a block diagram showing another configuration of the erase current control circuit.

FIG. 5 is a configuration diagram showing another configuration of the erasing head.

[Explanation of symbols]

 Reference Signs List 1 magnetic tape 3 first erasing head 4 second erasing head 5 recording head 6 reproducing head 8 erasing current control circuit 9 test signal generation circuit

Claims (3)

[Claims] 1. A first erasing head, a second erasing head provided downstream of the first erasing head, and a second erasing head from an upstream side along a running direction of a magnetic tape. , A read head provided further downstream of the write head, a DC power supply circuit for supplying a DC current to the first erase head, and a test signal generator for supplying a test signal to the write head And a erasing current control circuit for supplying a DC current to the second erasing head based on a reproduction signal reproduced by the reproducing head. A direct current so that the magnetic tape is magnetized in a second direction; and supplying a test signal to the recording head. A test signal is recorded on the magnetic tape, a test signal recorded on the magnetic tape is reproduced by the reproducing head, and a current flowing through the second erasing head is generated by the test signal reproduced by the reproducing head. Degaussing device for magnetic tape, characterized by determining the value of 2. The erasing current control circuit adjusts a current flowing through the second erasing head so that a peak voltage of a signal in a positive direction and a peak voltage in a negative direction of a signal reproduced from the reproducing head are equal. 2. The method according to claim 1, wherein
Magnetic tape degaussing device 3. The erase current control circuit according to claim 1, wherein the erase current control circuit controls a current flowing through the second erase head so that an amplitude of a signal reproduced from the read head is maximized. Magnetic tape degaussing device