JPH0581961B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION <Field of Industrial Application> The present invention relates to an erasing device in magnetic recording.
The present invention particularly relates to erasing information recorded on concentric tracks on a magnetic recording medium track by track using a narrow gap magnetic head with a gap width of 1.35 μm or less for recording or reproduction. This device is designed to effectively erase wideband, high-frequency recording signals such as modulated video signals, and eliminates the need for a relay to switch the magnetic head between recording, playback, and erasing. It is.

<Prior Art> The AC erasing method is well known as a method for erasing information recorded on a magnetic recording medium such as a magnetic tape or a magnetic disk. This is a magnetic recording medium.
As shown in FIG. 17, this is a method of applying an alternating magnetic field so that it gradually decreases from the saturation level. Due to this gradually decreasing alternating magnetic field, the hysteresis loop of the magnetization of the magnetic recording medium gradually becomes smaller, and eventually the magnetization becomes zero. In other words, once the magnetic flux is saturated, it draws a loop and converges to the magnetic neutral point, thereby eliminating residual magnetism. In FIG. 17, 100 indicates an alternating magnetic field, 101 indicates a hysteresis loop, and 102 indicates a change in magnetic flux.

For AC erasing, there are generally two methods: (1) using a bulk eraser and (2) using a magnetic head dedicated to erasing. In a method using a bulk eraser, the amplitude of the alternating current magnetic field generated by the bulk eraser itself is usually attenuated gradually. On the other hand, in a method using a magnetic head dedicated to erasing, the amplitude of the magnetic head does not need to change, but the magnetic field generated by the magnetic head changes during the time that any point on the magnetic recording medium passes over the gap of the magnetic head. The polarity of the signal must alternate many times. Therefore, the gap of the erase-only magnetic head is extremely wide, for example, on the order of several tens of micrometers. In other words, taking longitudinal recording as an example, as shown in FIG.
It is maximum at the center of the gap and gradually attenuates as you move away from the center of the gap. Therefore, if the magnetism of the magnetic field is alternated many times during the time that an arbitrary point on the magnetic recording medium 104 passes over the gap 105, the magnetic field received by that point will be 100 as shown in FIG.
It becomes an alternating magnetic field that gradually decreases in the same way as the waveform shown in
Once the magnetic flux is saturated near the gap center, as it moves away from the gap center, it draws a loop and converges to the magnetic neutral point, and residual magnetism disappears. As a result, AC cancellation is performed.

However, in the bulk eraser method (1), all tracks of the magnetic recording medium are erased, so it cannot be used for erasing each track.

On the other hand, according to the method (2) using a magnetic head dedicated to erasing, erasing can be performed on a track-by-track basis. However, since a magnetic head separate from the recording or reproducing head is required, the cost of the magnetic recording or reproducing apparatus increases and miniaturization of the apparatus is hindered. In particular, recently developed electronic still cameras and recording devices that use small magnetic disks of about 47 mm diameter to record video signals on concentric tracks are impractical because it is difficult to secure installation space for a magnetic head dedicated to erasing. .

<Problems to be Solved by the Invention> Therefore, it would be convenient if erasing as described in (2) above could be performed using a recording or reproducing magnetic head. However, while this is not a major problem with devices that record or play back signals in a relatively low frequency band, such as audio tape recorders, it is not a problem with devices that record or play back signals in a high frequency band, such as magnetic disk electronic still cameras. Since the gap of the recording or reproducing magnetic head is on the order of 0.1 μm, AC erasing is virtually impossible. For example, a 47mmφ magnetic disk is rotated 60 times per second, and a video signal is sent to a concentric track using a low carrier wave.
In an electronic still camera system that records one field per track using the FM method, the gap of the video head for recording or playback is 0.25 to 0.25 so that high frequency signals of about 10MHz can be recorded.
It is 0.35 μm. Therefore, in order to perform erasing as described in (2) above using a video head with such a narrow gap, it is necessary to
This means that it is necessary to generate a magnetic field with an extremely high frequency that far exceeds the upper limit of recording or reproducing frequencies such as 100 MHz, and with a sufficiently large amplitude. However, with current technology, it is not easy to make a recording or reproducing video head that can generate such an ultra-high frequency magnetic field, and it is also extremely expensive. Moreover, even if an ultra-high frequency magnetic field is generated, because it is an ultra-high frequency, the magnetic field will only reach the extremely shallow surface layer of the magnetic recording medium, and low-frequency signals of about 1 MHz or less are recorded even in the deep layers. remains without being erased. For the reasons mentioned above, AC erasure using a video head has not been put to practical use.

As a method for erasing each track using a magnetic head, there is a method in which a relatively high single frequency signal within the recording or reproduction frequency band is recorded over the track to be erased. Even with this method, the previously recorded signal is erased to some extent, but since a large amount of the subsequently recorded signal remains as a matter of course, it cannot be said that erasure has actually taken place. Furthermore, when the previously recorded signal has a wide frequency band, such as a video signal, there is a drawback that a considerably large amount of low frequency components remains.

Regarding the various problems and limitations that arise in the above-mentioned method of erasing by applying a high-frequency magnetic field to a magnetic recording medium using a recording or reproducing magnetic head, it is possible to solve
In a system in which scanning can be repeated many times with a single magnetic head, it is known that a method of erasing by applying a DC current pulse is effective. For example, Tokko Sho No. 47-19378, Tokko Sho No.
See No. 51-1409 and JP-A-48-66414. In all of the erasing methods disclosed in each publication, the erasing current is a combination of a plurality of rectangular current pulses that change the current direction and gradually decrease the level. The polarity of the rectangular current pulse changes every time it takes for one rotation of the magnetic disk. According to these erasing methods, the low frequency components of the previously recorded signals are not erased and remain without being erased, while the magnetic disk remains at its normal rotational speed, as explained in the bulk eraser method. Effects similar to AC cancellation can be expected in single track cancellation.

However, in the erasing method using DC current pulses, it is necessary in principle to apply a DC current whose polarity is reversed to the coil of the magnetic head. For example, it is not possible to switch between the erase signal circuit and the recording or reproduction signal circuit on the secondary side (amplifier side) of a step-up transformer.
On the primary side of a step-up transformer, that is, where weak signals are handled, it is necessary to switch between erasing and recording or reproducing. It is inappropriate to employ a relay circuit or the like for this switching because it would complicate the mounting circuit, given the demand for more compact devices. For this reason, it has not been possible to obtain a practical erasing device having a switching circuit between erasing and recording or reproducing with high operational reliability.

In view of the problems of the prior art described above, the present invention
The aim is to realize a new magnetic incineration device that eliminates various drawbacks and restrictions.

In other words, the purpose of the present invention is to erase data from each concentric recording track by changing the gap width for recording or reproduction.
When using a magnetic head with a narrow gap of 0.35 μm or less, it basically guarantees an erase effect comparable to that of a bulk eraser, and the mechanism for switching between erase mode and recording or playback mode is simple, highly reliable, and compact. The purpose is to provide a magnetic erasing device suitable for.

<Means for Solving the Problems> A magnetic erasing device according to a first invention that achieves the above-mentioned object has a gap width for recording or reproducing that scans concentric tracks of a magnetic recording medium.
A transformer having a narrow gap magnetic head of 0.35 μm or less, a first coil connected to a recording or reproducing amplifier, and a second coil electrically insulated from the first coil, and the narrow gap magnetic head. and a second coil of a transformer connected in series, and two DC constant current sources of the same polarity whose current value can be controlled and whose output terminals are respectively connected to both ends of this series circuit. , two semiconductor switches are respectively connected between both ends of the series circuit and the return path of the DC constant current source, both semiconductor switches are kept on during recording or reproduction, and both semiconductor switches are tracked during erasing. A switch control circuit that alternately controls on/off at intervals equal to or longer than one scanning period, and a switch control circuit that maintains the current value of both DC constant current sources at zero during recording or reproduction, and maintains the current value of both DC constant current sources at zero during erasing. and a current control circuit that changes the current values of both DC constant current sources so that the magnitude of the magnetic field that any point on the track receives from the narrow gap magnetic head decreases each time the semiconductor switch is switched. be.

Further, the magnetic erasing device according to the second invention includes a plurality of narrow gap magnetic heads for recording or reproducing that scan concentric tracks of a magnetic recording medium and having a gap width of 0.35 μm or less, and connected to an amplifier for recording or reproducing. a plurality of trans A series circuit consisting of multiple unit circuits connected in series, and two DC constant currents of the same polarity that can control the current value, with output terminals connected to each end of this series circuit. a plurality of semiconductor switches connected respectively between the source, the connection between both ends of the series circuit and the unit circuit, and the return path of the DC constant current source, and keeping the plurality of semiconductor switches on during recording or reproduction; ,
During erasing, two semiconductor switches connected to both ends of the series circuit are turned on and off alternately for periods equal to or longer than the scanning period of one track revolution.
A switch control circuit that performs OFF control and keeps other semiconductor switches OFF, and maintains the current value of both DC constant current sources at zero during recording or reproduction, and when erasing, any point on the track is set to the narrow gap magnetic field. The device further includes a current control circuit that changes the current values of both of the DC constant current sources so that the magnitude of the magnetic field received from the head decreases each time the semiconductor switch is switched.

Furthermore, a magnetic erasing device according to a third aspect of the present invention includes a plurality of narrow gap magnetic heads for recording or reproducing scanning concentric tracks of a magnetic recording medium and having a gap width of 0.35 μm or less, and connected to an amplifier for recording or reproducing. a plurality of trans Current value control is possible with multiple unit circuits consisting of multiple unit circuits, a series circuit consisting of multiple unit circuits connected in series, and output terminals connected to both ends of this series circuit and the connection between arbitrary unit circuits. A plurality of DC constant current sources of the same polarity, a plurality of semiconductor switches respectively connected between both ends of the series circuit, all unit circuit connections, and a return path of the DC constant current source; All of the plurality of semiconductor switches are kept on, and during erasing, the two semiconductor switches connected to both ends of the series circuit are alternately turned on for a period equal to or longer than the scanning period of one track cycle as the first erase mode. /off control and keep the other semiconductor switches off, and as a second erase mode, the semiconductor switch connected to the connection between one unit circuit to which the output terminal of the DC constant current source is connected and the other DC constant A switch control circuit that alternately controls on/off of a semiconductor switch connected to a current source at intervals equal to or longer than the scanning period of one track rotation and keeps other semiconductor switches off; In , the current values of all DC constant current sources are kept at zero, and in erasing, the current values of two DC constant current sources whose output terminals are connected to two semiconductor switches controlled on/off are kept at zero. a current control circuit that changes the magnitude of the magnetic field received from the narrow gap magnetic head at any point on the track to be detected so as to decrease with each switching of the semiconductor switch, and maintains the current value of the other DC constant current source at zero; It is equipped with the following.

<Function> Let us now consider a recording apparatus in which a magnetic disk 1 is rotated by a motor 2 and a magnetic head 3 is connected to the magnetic disk 1 for recording or reproduction as shown in FIGS. 2 and 3. In FIG. 2, 4 is a coil of the magnetic head 3. Further, FIG. 3 is a plan view of FIG. 2, where 5 is a concentric track and 6 is a direction of rotation of the disk. Here, the period during which the magnetic head 3 scans the track 5 once is assumed to be Ts (for example, Ts=1/60 sec). Assume that an erasing current 7 whose polarity alternates at intervals of Tp and whose amplitude gradually decreases exponentially as shown in FIG. 5 is passed through the coil 4 of the magnetic head 3. However, Tp≧Ts. Then, Tp≧Ts
Therefore, at any point on track 5,
According to the rotation of disk 1, as shown in Fig. 6,
Magnetic field 8 whose polarity alternates and whose amplitude gradually decreases every Tp
acts. In this case, the minimum value I ₁ of the erase current 7 during the first constant polarity period is a value that can generate a magnetic field that magnetizes the magnetic disk 1 to the saturation level. As a result, once the magnetic flux is saturated at any point on the track 5, it converges in a loop to the magnetic neutral point, resulting in residual magnetism. Note that it is desirable that the amplitude of the erase current 7 attenuates as slowly as possible in a region close to zero. The waveform of the erasing current may be a waveform 9 whose amplitude attenuates in steps at every Tp as shown in Fig. 7, since it is sufficient that the magnetic field 8 as shown in Fig. 6 acts on any point on the track. anything is fine.

In the present invention, by alternately turning on and off two semiconductor switches between the output terminals of two DC constant current sources and their return paths, an arbitrary point on the track is transmitted every Tp as shown in FIG. so that a magnetic field 8 of alternating polarity and gradually decreasing amplitude acts on the
An erase current having a waveform as illustrated in FIGS. 5 and 7 flows through the magnetic head between the output terminals of the two constant current sources. Tp is determined by the switch control circuit, and the amplitude change is determined by the current control circuit. In this case, the load on the DC power supply changes depending on whether the semiconductor switch is turned on or off, but since it is a constant current source, the output current of the DC power supply remains at a value determined by the current control circuit regardless of load fluctuations.

The transformer galvanically isolates the recording or reproducing amplifier from the magnetic head. When all the semiconductor switches are turned on, the coil of the magnetic head and the second coil of the transformer form a closed loop through the two semiconductor switches in the circuit connected in series, allowing the recording current to flow through the transformer to the coil of the magnetic head. In addition, the reproduced signal generated in the coil of the magnetic head can be taken out from the transformer. During recording or reproduction, by setting the current values of all DC constant current sources to zero, DC noise on the recording current or reproduction signal is reduced.

<Embodiments> Hereinafter, embodiments of the magnetic erasing device according to the present invention will be described with reference to the drawings.

FIG. 1 shows an embodiment of the first invention. In the figure,
3 is a magnetic head for recording or reproducing, 4 is a coil of the magnetic head 3, 10 is a step-up transformer, 11 is a first coil thereof, 12 is a second coil that is galvanically insulated from the first coil, 13 14 and 15 are DC constant current sources of the same polarity that can each control the current value, 16 and 17 are semiconductor switches, 18 is a switch control circuit, 19 is a current control circuit, 20 is a command switch, 18a and 1
8b is a switch control signal, and 19a is a current control signal.

In FIG. 1, the coil 4 of the magnetic head and the second coil 12 of the transformer form a series circuit 21,
The output terminals of DC constant current sources 14 and 15 are connected to both ends of this series circuit 21, respectively. Further, both ends of the series circuit 21 are connected to the semiconductor switch 1, respectively.
It is grounded via 6 and 17.

The operation of the magnetic erasing device shown in FIG. 1 will be explained with reference to FIGS. 4a to 4e. Erase command 22 as shown in Figure 4a
, a gradually decreasing current 23 that attenuates from a predetermined value to zero as shown in FIG. As shown in d, under the control of the switch control circuit 18, the two semiconductor switches 16 and 17 are alternately turned on and off every Tp.
However, Tp≧Ts, and Ts is the scanning period of one track revolution. As a result, the same erasing current 7 as shown in FIG. 5 flows through the coil 4 of the magnetic head 3, as shown in FIG.
It is sufficient that the erase current becomes zero after 10 to 100 polarity changes. On the other hand, when the recording or reproducing command 24 is issued after erasing, the two semiconductor switches 16 and 17 are activated while the output currents of the DC constant current sources 14 and 15 have already attenuated to zero as shown in FIG. As shown in c and d of the figure, both are turned on under the control of the switch control circuit 18. This results in
No erasing current flows, and recording or reproduction becomes possible.

Note that in order to obtain the erase current 9 shown in FIG.
The current control circuit 19 may be controlled so that the output currents of the two DC constant current sources 14 and 15 are attenuated stepwise each time the semiconductor switches 16 and 17 are switched.

FIG. 8 shows a specific circuit example of the device shown in FIG. The device shown in FIG. 8 consists of a DC constant current source made up of a current mirror circuit. The emitter of the NPN transistor TR1 is grounded through a resistor R1.
The base and collector of a PNP transistor TR2 connected through the transistor TR2 are connected to each other. The base of this transistor TR2 is connected to two PNP transistors TR3 and TR4 whose emitters are connected to the positive terminal of the DC power supply through resistors R3 and R4, respectively.
The base is connected. The collectors of these transistors TR3 and TR4 are connected to the coil 4 of the magnetic head 3 and the second coil 12 of the transformer 10, respectively.
are connected to both ends of the series circuit 20, and two further
NPN type switching transistor TR5, TR
6 collector. The emitters of the two switching transistors TR5 and TR6 are directly grounded. The bases of the two switching transistors TR5 and TR6 each have an NPN
The emitters of drive transistors TR7 and TR8 are connected. two transistors TR7
The collectors of TR8 and TR8 are connected to the positive terminal of the DC power supply through resistors R7 and R8, respectively. The base of transistor TR7 is connected to the Q terminal of flip-flop 25 through resistor R9, and the base of transistor TR8 is connected to the output terminal of OR gate 26 through resistor R10. The PR terminal of the flip-flop 25 is selectively connected to a low potential and a high potential through a command switch 20.
CL terminal is grounded. In addition, the CP terminal of the flip-flop 25 has a pulse 27 generated every scanning period Ts of one track cycle, such as a PG pulse and a VD pulse.
is being input, and the terminal and the D terminal are short-circuited. Two input terminals of OR gate 26 are connected to a terminal of flip-flop 25 and a PR terminal, respectively.

The operation shown in FIG. 8 will be explained. Attenuation voltage generation circuit 2
8 to the attenuated voltage of the specified waveform to the transistor TR1.
When applied to the base of the attenuation voltage, the attenuation voltage is converted into an attenuation current having a waveform similar to this, and attenuation currents I ₁ , I ₂ , I ₃ having the same waveform flow through the three transistors TR2 to TR4 due to the current mirror effect. Emitter resistance R2, R of each transistor TR2 to TR4
3 and R4 maintain I ₁ =I ₂ =I ₃ due to negative feedback action.
These attenuating currents I ₁ to _{I 3} are caused by the transistor TR1
is a constant current determined by the attenuated voltage applied to the base of Therefore, when the command switch 20 is turned to the erase side and the PR terminal of the flip-flop 25 is set to a low potential, the input pulse 27 of the CP terminal is frequency-divided.
Two switching transistors TR5 and TR6
and is alternately turned on and off every time the pulse 27 is input, that is, every time Tp (here, Tp=Ts).
As a result, an erase current 7 shown in FIG. 4e flows.
On the other hand, when the command switch 20 is turned on to the recording or reproducing side and the PR terminal is set to high potential, the Q terminal and the OR
Both output terminals of the gate 26 become high potential,
Two switching transistors TR5 and TR6
Both are turned on. The decay currents I ₁ , I ₂ , I ₃ have already become zero, and recording or reproduction is possible.

In the specific circuit example shown in FIG. 8, the CP terminal of the flip-flop 25 is
A pulse 27 generated every Ts is input, and the polarity of the erase current 7 is reversed every period Tp when Tp=Ts. When Tp>Ts, a pulse may be applied to the CP terminal of the flip-flop 25 every period Tp such that Tp>Ts. Examples of circuits that provide such pulses are shown in FIGS. 9 and 10. In FIG. 9, the oscillator 50 includes a frequency generator (FG) 51 that generates a frequency signal proportional to the number of rotations of a magnetic disk (numeral 1 in FIG. 2), a waveform shaping amplifier 52, and a 1/N A frequency divider 53 is provided. As mentioned above, since Ts is the period during which the magnetic head scans the circular track on the magnetic disk once, the frequency generator (FG) 51 has a frequency of f=K×1/Ts (where K≫ 1). If a signal 51a is to be generated, the frequency divider 53 divides the input signal under the condition of 1/N<1/K, thereby obtaining a signal 53a having a period Tp longer than Ts. That is, Tp=N/f=N/K·Ts>Ts. To give a specific example, if a frequency generator (FG) 51 with f=16×1/Ts is used, a pulse signal 52a whose waveform has been shaped as shown in FIG. Since input, N
By dividing the frequency as =17, a pulse signal 53a with Tp=(1+1/16)Ts as shown in FIG. 10b is obtained. Here, when N=18, Tp=(1+2/16Ts, and when N=19, Tp=(1+3/16Ts). By choosing K and N appropriately, Tp and
The relationship of Ts can be set to any value,
The output pulse 53a of the frequency divider 53 may be input to the CP terminal of the flip-flop 25 shown in FIG.

Next, an embodiment of the second invention will be described with reference to FIG. FIG. 11 shows an example of a two-channel magnetic head. 3-1 and 3-2 are magnetic heads for recording or reproducing, respectively; 4-1 and 4;
-2 is the coil of each magnetic head, 10-1 and 10
-2 are step-up transformers, 11-1 and 11, respectively.
-2 is the first coil of each transformer, 12-1 and 1
2-2 is the second coil of each transformer, 13-1 and 13-2 are recording or playback amplifiers, 1
4 and 15 are DC constant current sources of the same polarity that can control the current value, 6, 17, and 29 are semiconductor switches, 18 is a switch control circuit, and 19
is a current control circuit, 20 is a command switch, 18a,
18b and 18c are switch control signals, and 19a is a current control signal.

In FIG. 11, the coil of one magnetic head and the second coil of one transformer are connected in series to form one unit circuit, and two unit circuits 30
-1 and 30-2 further form a series circuit 31. The output terminals of DC constant current sources 14 and 15 are connected to both ends of the series circuit 31, respectively, and the semiconductor switches 16 and 15 are connected to both ends of the series circuit 31, respectively.
It is grounded through 17. Further, the inter-unit circuit connection section 32 is grounded through the semiconductor switch 29.

The operation of the magnetic erasing device shown in FIG. 11 will be explained with reference to FIGS. 12a to 12f. When the erase command 22 is issued as shown in FIG. 12a by operating the command switch 20,
A gradually decreasing current 23 that attenuates from a predetermined value to zero as shown in FIG. At the same time, as shown in c and d of the figure, two semiconductor switches 16 and 17 connected to both ends of the series circuit 31 are turned on and off alternately at each Tp under the control of the switch control circuit 18. However, Tp≧Ts, Ts is the operation period of one track revolution. The semiconductor switch 29 connected to the connection between unit circuits is shown in FIG. 12e.
As shown in FIG. 3, the switch is turned off under the control of the switch control circuit 18. As a result, as shown in FIG.
An erase current 7 having the same waveform as that shown in FIG. 5 flows through the tracks 1 and 4-2, and the two tracks are erased at the same time. It is sufficient that the erase current becomes zero after 10 to 100 polarity changes.

On the other hand, when the command switch 20 is operated after erasing and the recording or reproduction command 24 is issued as shown in FIG. 12a, the output currents of the DC constant current sources 14 and 15 are
In a state where the attenuation is already zero as shown in FIG. 2, all the semiconductor switches 16, 17 and 29 are turned on under the control of the switch control circuit 18 as shown in FIGS. As a result, no erasing current flows, and each magnetic head 3-1, 3-2 can perform recording or reproduction.

Next, an embodiment of the third invention will be described with reference to FIG. FIG. 13 shows an example of a two-channel magnetic head. 3-1 and 3-2 are recording or reproducing magnetic heads, 4-1 and 4-2 are coils of each magnetic head, 10-1 and 10-2 are step-up transformers, and 11-1 and 11-2 are respectively The first coil of each transformer, 12-1 and 12-2 are the second coils of each transformer, 13-1 and 13-2 are recording or playback amplifiers, and 14, 15, and 40 are each capable of controlling the current value. DC constant current sources of the same polarity, 16, 17 and 29 are semiconductor switches, 18 is a switch control circuit, 19 is a current control circuit, 41 is a command switch, 18a, 1
8b and 18c are switch control signals, 19a is a current control signal, and 19b, 19c and 19d are current cutoff signals.

In FIG. 13, the coil of one magnetic head and the second coil of one transformer are connected in series to form one unit circuit, and two unit circuits 30
-1 and 30-2 further form a series circuit 31. The output terminals of DC constant current sources 14 and 15 are connected to both ends of the series circuit 31, respectively, and the semiconductor switches 16 and 15 are connected to both ends of the series circuit 31, respectively.
It is grounded through 17. Further, the output terminal of a direct current constant current source 40 is connected to the unit circuit connection part 32, and this unit circuit connection part 32 is grounded through the semiconductor switch 29.

1 with reference to Figures 14, 15, and 16.
The operation of the magnetic erasing device shown in FIG. 3 will be explained.

First, referring to FIGS. 14a to 14f, the operation when two magnetic heads 3-1 and 3-2 are used for erasing and two tracks are simultaneously erased will be described. 2 as shown in FIG. 14a by operating the command switch 41.
When the two-track erase command 42 is issued by the two magnetic heads 3-1 and 3-2, under the control of the current control circuit 19, only the two DC constant current sources 14 and 15 connected to both ends of the series circuit 31 are used. As shown in FIG. 5B, a gradually decreasing current 23 that attenuates from a predetermined value to zero is output, and the output current of the DC constant current source 40 connected to the unit circuit connection section 32 is made zero. This is controlled by the current control signal 19a, which direct current constant current source 1
4, 15, and 40 are also operated to output the same gradually decreasing current, but only the current cutoff signal 19c for the DC constant current source 40 is activated. At the same time, as shown in FIG. 14c and d, two semiconductor switches 16 and 17 connected to both ends of the series circuit 31 under the control of the switch control circuit 18
Turn on/off alternately. However, Tp≧Ts, Ts
is the scanning period of one track revolution. The semiconductor switch 29 connected to the unit circuit connection part 32 is the first
As shown in FIG. 4e, the switch is turned off under the control of the switch control circuit 18. As a result, as shown in FIG. 14f, the erasing current 7 having the same waveform as that in FIG. 5 flows through each coil 4-1 and 4-2 of the two magnetic heads, and the two tracks are simultaneously erased. It is sufficient that the erase current becomes zero after 10 to 100 polarity changes. On the other hand, after erasing, the command switch 4
1 to issue a recording or reproduction command 43 as shown in FIG.
With the output current of 5 and 40 also becoming zero,
All semiconductor switches 16, 17 and 29 are turned on as shown in c, d and e of the figure. As a result, no erase current flows and each magnetic head 3-1, 3-2
can be recorded or erased by

Next, referring to FIGS. 15a to 15f, an explanation will be given of the operation when one of the two magnetic heads, 3-1, is used for erasing and only one track is erased. 15a by operating the command switch 41.
When one track erase command 44 is issued by one of the magnetic heads 3-1 as shown in FIG. Only the DC constant current source 40 connected to the series circuit 32 outputs a gradually decreasing current 23 that attenuates from a predetermined value to zero as shown in FIG. The current is brought to zero. This is controlled by the current control signal 19a, which direct current constant current source 1
4, 15, and 40 are also operated to output the same gradually decreasing current, but only the current cutoff signal 19d for the DC constant current source 15 is activated. At the same time, as shown in FIG. 15c and d, under the control of the switch control circuit 18, two
The two semiconductor switches 16 and 29 are alternately turned on and off every Tp. However, Tp≧Ts, Ts is the scanning period of one track revolution. The semiconductor switch 17 connected to the other end of the series circuit 31 is controlled by a switch control circuit 18 as shown in FIG. 15e.
It's off. As a result, as shown in FIG. 15f, the coil 4-1 of one magnetic head 3-1
An erasing current 7 having the same waveform as in FIG. 5 flows only through 1,
Only one track will be erased. Erasing current is 10
It is good if it becomes zero after ~100 polarity changes. On the other hand, after erasing, operate the command switch 41 to
When the recording or playback command 43 is issued as shown in Figure 5a,
With the output currents of all DC constant current sources 14, 15, and 40 being zero, all semiconductor switches 16, 17, and 29 are turned on as shown in c, d, and e of the figure. As a result, no erasing current flows, and each magnetic head 3-1, 3-2 can perform recording or erasing.

Next, referring to FIGS. 16a to 16f, the operation when the other of the two magnetic heads 3-2 is used for erasing and only the other track is erased will be explained. 16a by operating the command switch 41.
When the one-track erase command 45 is issued by the other magnetic head 3-2 as shown in FIG. Only the DC constant current source 40 connected to the series circuit 32 outputs a gradually decreasing current 23 that attenuates from a predetermined value to zero as shown in FIG. is set to zero. This is controlled by the current control signal 19a, which direct current constant current source 1
4, 15, and 40 are also operated to output the same gradually decreasing current, but only the current cutoff signal 19b for the DC constant current source 14 is activated. At the same time, as shown in FIG. 16c and d, under the control of the switch control circuit 18, two
The two semiconductor switches 17 and 29 are alternately turned on and off every Tp. However, Tp≧Ts, Ts is the scanning period of one track revolution. The semiconductor switch 16 connected to one end of the series circuit 31 is under the control of the switch control circuit 18, as shown in FIG. 16e.
It's off. As a result, as shown in FIG. 16f, the coil 4-2 of the other magnetic head 3-2
An erase current 7 having the same waveform as in FIG. 5 flows only through 2,
Only the other track is erased. Erasing current is 10
It is good if it becomes zero after ~100 polarity changes. On the other hand, after erasing, operate the command switch 41 to
When a recording or reproducing command 43 is issued as shown in Figure 6a,
With the output currents of all DC constant current sources 14, 15, and 40 being zero, all semiconductor switches 16, 17, and 29 are turned on as shown in c, d, and e of the figure. As a result, no erasing current flows, and each magnetic head 3-1, 3-2 can perform recording or erasing.

However, in the magnetic erasing device shown in FIG. 13, erasing can be performed independently by either of the two magnetic heads 3-1 and 3-2, but if only one of the magnetic heads 3-1, for example, In some cases, it is sufficient that the data can be erased independently.
In such a case, the current control circuit 1 in FIG.
It is sufficient to remove the current cutoff signal 19b that 9 gives to one DC constant current source 14.

<Effects of the Invention> According to the present invention, the magnetic head is switched between recording, playback, and erasing by turning on/off the semiconductor switch and controlling the DC constant current source, so the circuit configuration is simple and miniaturization is easy. and is highly reliable.
That is, an extremely simple constant current source may be used, and current control is also easy. (1) According to the circuit configuration of the present invention, in order to obtain an erase current that attenuates in both positive and negative polarities, it is sufficient to create one type of attenuation current, and in the case of a one-channel head system, one constant current control is required. It can be controlled by line, and it can also be controlled by 2
This is because even in the case of a channel head system, it is possible to add a constant current control line with one transistor. In addition, (2) polarity switching control for changing the attenuation current to a reversal current in the magnetic head can be achieved by only on/off control of two semiconductor switches in the case of a one-channel head system. be.

Further, according to the present invention, an erasing device suitable for realizing switching control between erasing mode and recording or reproducing mode in a system using a plurality of magnetic heads can be obtained.

Further, according to the present invention, erasing can be performed on each concentric track using a recording or reproducing magnetic head at a residual erasing level comparable to that of a bulk eraser.

Further, according to the present invention, the polarity of the erase current may be reversed every period that coincides with the scanning period of one track revolution, or may be reversed every period longer than the scanning period of one track revolution. Even in this case, high-performance erasing comparable to that of a bulk eraser can be performed for each concentric track.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of an embodiment of a magnetic erasing device according to the first invention, FIG. 2 is a side view showing the relationship between a magnetic disk and a magnetic head, and FIG.
4 is an explanatory diagram of the operation of the device in FIG. 1, FIG. 5 is a diagram showing an example of the erasing current waveform, and FIG.
The figure is a diagram explaining the principle of erasure, Figure 7 is a diagram showing other waveform examples of the erase current, Figure 8 is a circuit diagram showing a specific example of the device in Figure 1, and Figure 9 is a pulse for Tp>Ts. A diagram showing an example of a generating circuit, FIG. 10 is a timing chart of its operation, FIG. 11 is a block configuration diagram of an embodiment of the magnetic erasing device according to the second invention, and FIG. 12 is an explanation of the operation of the device of FIG. 11. 13 is a block diagram of an embodiment of the magnetic erasing device according to the third invention, FIGS. 14, 15, and 16 are explanatory diagrams of the operation of the device shown in FIG. 13, and FIG. FIG. 18, which is an explanatory diagram of the principle of AC erasing, is an explanatory diagram of the magnetic field that a magnetic head exerts on a magnetic recording medium. In the drawings, 1 is a magnetic disk, 3, 3-1, 3-
2 is a magnetic head for recording or reproducing, 4, 4-1,
4-2 is the coil of the magnetic head, 7 and 9 are the erasing currents, 8 is the magnetic field that any point on the track receives, 1
0, 10-1, 10-2 are step-up transformers, 11,
11-1, 11-2 are step-up transformer coils, 1
2, 12-1, 12-2 are step-up transformer coils, 13, 13-1, 13-2 are recording or reproducing amplifiers, 14, 15, 40 are DC constant current sources, 1
6, 17, 29 are semiconductor switches, 18 is a switch control circuit, 19 is a current control circuit, 21, 31 is a series circuit, 23 is a gradually decreasing current, 30-1, 30-2
3 is a unit circuit, and 32 is a connection section between unit circuits.

Claims (1)

[Scope of Claims] 1. A narrow gap magnetic head with a gap width of 0.35 μm or less for recording or reproducing that scans concentric tracks of a magnetic recording medium, a first coil connected to an amplifier for recording or reproducing, and a first coil and a first coil connected to an amplifier for recording or reproducing. a transformer having a second coil that is galvanically insulated from the first coil; a series circuit in which the coil of the narrow gap magnetic head and the second coil of the transformer are connected in series; Two DC constant current sources of the same polarity capable of controlling current values, each having an output terminal connected to each end thereof, and two semiconductor switches each connected between both ends of the series circuit and a return path of the DC constant current sources. and switch control that keeps both semiconductor switches on during recording or playback, and alternately turns on and off both semiconductor switches during erasing at intervals equal to or longer than the scanning period of one track revolution. During recording or reproduction, the current value of both DC constant current sources is kept at zero, and during erasing, the magnitude of the magnetic field that any point on the track receives from the narrow gap magnetic head is controlled every time the semiconductor switch is switched. and a current control circuit that changes the current value of both DC constant current sources so that the current value decreases. 2 Multiple gaps for recording or reproducing scanning concentric tracks of a magnetic recording medium have a width of 0.35 μm
a narrow gap magnetic head; a plurality of transformers each having a first coil connected to a recording or reproducing amplifier; and a second coil electrically insulated from the first coil; a plurality of unit circuits in which a head coil and a second coil of a transformer are connected in series; a series circuit in which a plurality of unit circuits are connected in series;
Two DC constant current sources of the same polarity whose output terminals are connected to both ends of the series circuit and whose current value can be controlled, a connection between both ends of the series circuit and the unit circuit, and a return path of the DC constant current sources. During recording or reproduction, the plurality of semiconductor switches are kept on, and during erasing, two semiconductor switches connected to both ends of the series circuit are kept on during the scanning period of one track revolution. a switch control circuit that alternately performs on/off control at equal or longer intervals and keeps other semiconductor switches off; and a switch control circuit that maintains the current value of both of the DC constant current sources at zero during recording or reproduction; In erasing, the present invention includes a current control circuit that changes the current values of both of the DC constant current sources so that the magnitude of the magnetic field that any point on the track receives from the narrow gap magnetic head decreases each time the semiconductor switch is switched. magnetic eraser. 3 The width of multiple gaps for recording or reproducing scanning concentric tracks of a magnetic recording medium is 0.35 μm.
a narrow gap magnetic head; a plurality of transformers each having a first coil connected to a recording or reproducing amplifier; and a second coil electrically insulated from the first coil; a plurality of unit circuits in which a head coil and a second coil of a transformer are connected in series; a series circuit in which a plurality of unit circuits are connected in series;
A plurality of DC constant current sources of the same polarity capable of controlling the current value, each having an output terminal connected to both ends of the series circuit and a connection between arbitrary unit circuits, and a connection between both ends of the series circuit and all the unit circuits. A plurality of semiconductor switches are connected between the main unit and the return path of the DC constant current source, and during recording or reproduction, all of the plurality of semiconductor switches are kept on, and during erasing, as a first erasing mode, the semiconductor switches are connected to both ends of the series circuit. Track 1 of the two connected semiconductor switches
One unit to which the output terminal of the DC constant current source is connected as a second erasing mode, alternately controlling on/off at intervals equal to or longer than the scanning period of the cycle, and keeping other semiconductor switches off. The semiconductor switch connected to the inter-circuit connection part and the semiconductor switch connected to one other direct current constant current source are alternately controlled on/off at intervals equal to or longer than the scanning period of one track revolution. In addition, there is a switch control circuit that keeps other semiconductor switches off, and output terminals for two semiconductor switches that keep the current values of all DC constant current sources at zero during recording or playback, and are controlled on/off during erasing. The current values of two DC constant current sources connected to the track are varied in such a way that the magnitude of the magnetic field that any point on the track to be erased receives from the narrow gap magnetic head decreases with each switching of the semiconductor switch. and a current control circuit that maintains the current value of another DC constant current source at zero.