JPH0450643B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a magnetic recording device suitable for application to, for example, a rotating head type PCM tape recorder, a video tape recorder, and the like.

BACKGROUND TECHNOLOGY AND PROBLEMS It is known that in conventional rotary head type PCM tape recorders, for example, when recording a new signal on a magnetic tape that has already been recorded, the previous signal is overwritten without being erased. ing.
In this case, if clogging occurs in the magnetic head during recording (magnetic powder etc. adheres to the head, the magnetic tape rises above the magnetic head, spacing loss increases and recording becomes impossible), the previously recorded signal is erased. During playback, this will be played back and cause abnormal noise.

For example, as shown in FIG. 1, consider a case where recording signals are alternately supplied to rotating magnetic heads _H1 and _H2 arranged at different azimuth angles, and recording tracks are alternately formed on the magnetic tape 1. think.

In FIG. 1, 2 is a tape guide drum.

Assume that the previously formed track pattern is as shown in FIG. T ₁ ' and T ₂ ' are recording tracks formed by magnetic heads H ₁ and H ₂ , respectively.

Here, if clocking occurs in magnetic head _H1 , if the track pitch deviates by one pitch from the previous track pitch during overwriting, the track pattern will be as shown in Figure 3, and the track pitch before the overwriting will change. In the same case, the track pattern as shown in FIG. 4 will be obtained. In FIGS. 3 and 4, _T2 is a recording track newly formed by magnetic head _H2 .

In this way, the previously formed recording track T ₁ ′,
T ₂ ′ remains without being erased, and signals are also reproduced from these during playback, causing abnormal noise.

In addition, the magnetic head scans the magnetic tape completely without tracking.
A method has been proposed in which a correct reproduction signal is obtained by signal processing a reproduction signal obtained from a magnetic head. In this case, if clogging occurs in the magnetic head during recording, previously recorded signals will also be reproduced during reproduction, making it impossible to obtain a correct reproduced signal.

It is desirable to detect such clogging during recording and take appropriate countermeasures, but this has conventionally been impossible except for simultaneous recording/playback machines (technically quite difficult).

OBJECTS OF THE INVENTION The present invention has been made in view of the above-mentioned problems, and it is an object of the present invention to easily detect clocking during recording and to immediately take countermeasures against this clocking.

SUMMARY OF THE INVENTION In order to achieve the above object, the present invention provides first and second rotating magnetic heads having different azimuth angles, which are provided at a predetermined angular interval with respect to the rotational direction, and wherein the first and second magnetic heads is rotated at a predetermined speed with the first magnetic head scanning the magnetic tape in advance, a recording signal is supplied to the first and second magnetic heads, and the first magnetic head is placed on the magnetic tape. and in which recording tracks are alternately formed by the second magnetic head, after the recording tracks are formed by the first magnetic head, the second magnetic head is brought into a reproducing state, and the recording tracks from the second magnetic head are The recording state of the first magnetic head is detected based on the reproduced signal.

Embodiment Hereinafter, an embodiment of the present invention will be described with reference to FIG. 5 and subsequent figures. This example is an example applied to a rotating head type PCM tape recorder.

FIG. 5 shows the rotary head device in this example. In the figure, 3 is a tape guide drum. A magnetic tape 4 is run diagonally along this tape guide drum 3 over an angular range of, for example, 180°. Further, H _A and H _B are rotating magnetic heads for recording/reproducing, respectively. Magnetic head H _A and
H _B has a predetermined angular interval θ ₁ with respect to the rotation direction x,
And the magnetic head H _A is installed in front. Also, the azimuth angle of magnetic heads H _A and H _B (the angle of inclination of the gap with respect to the direction perpendicular to the scanning direction)
are made to be different from each other. Also, magnetic heads
The scanning trajectories of H _A and H _B on the magnetic tape 4 are made to match. For example, if the magnetic head H _A is 1
It is lowered in the rotational axis direction than the magnetic head H _B by track pitch x θ ₁ /360°. Also magnetic head
H _A and H _B are rotated in the x direction at, for example, 60 revolutions/second.

During recording, each time the magnetic heads H _A and H _B rotate once and scan the magnetic tape 4, a recording signal S _REC is generated.
are sequentially supplied, and when the recording signal _SREC is supplied to the magnetic head H _B , the erasing signal S _ELASE is supplied to the magnetic head H _A. Further, after the recording track is formed by the magnetic head H _A , the magnetic head H _B is put into the reproducing state, and the recording state of the magnetic head H _A is detected from the reproduction signal from now on.

In FIG. 6, an analog signal, for example an audio signal, is supplied to the input terminal 5, and this audio signal is converted into an audio signal by an A-D converter 6.
This signal is converted into a PCM signal and is supplied to the encoder 7. In this encoder 7, a synchronization signal,
Addition of an error correction code and error detection code, and compression of the time axis are performed. FIG. 7 shows the code structure of recording data obtained from the output of the encoder. A synchronization signal, a block address signal, and a CRC code for error detection are added to data consisting of a plurality of samples of audio PCM signals or error correction codes. As the error correction code, a parity code, an adjacent code, etc. can be used, and interleaving may also be used. The block address signal is the TBC (time base collector) as described below.
This is for individually distinguishing blocks in a series of reproduced data input to the memory, and a simple incremental code signal, a combination of multiple types of addresses, etc. can be used. The CRC code is designed to detect the presence or absence of errors in both the block address signal and data.
The output of the encoder 7 is then supplied to the modulator 8, where it is modulated using a modulation method such as NRZI, 3PM, or MFM. On the output side of this modulator 8, as shown in FIG.
As shown in FIG. 2, the magnetic heads H _A and H _B scan the magnetic tape 4, and a recording signal S _REC is obtained that exists in a range of, for example, 180 degrees.

This recording signal S _REC is supplied to the A side terminal of the changeover switch 9. In addition, 10 is the erasing signal S _ELASE
For example, a signal with a frequency that is twice or more the highest frequency of the recording signal _SREC is generated as the erasing signal _SELASE . This erasing signal
For example, the level of S _ELASE is the level of the recording signal S _REC .
It is said to be 1.2 to 3 times more. This erasing signal S _ELASE is supplied to the B side terminal of the changeover switch 9. Moreover, the intermediate terminal M of this changeover switch 9 is grounded. For example, the changeover switch 9 is connected to the intermediate terminal M when the changeover control signal supplied thereto is at 0 level, is switched to the A side when it is at a positive level, and is switched to the B side when it is at a negative level. This changeover switch 9
A signal _S1 as shown in FIG. 8B is supplied from the system control circuit 11 as a switching control signal.

From the changeover switch 9 _, as shown in FIG _. (not shown) to the magnetic head H _A.
The recording/reproducing switch 13 is supplied with a switching control signal _S3 from the system control circuit 11. During recording, the signal _S3 is as shown in FIG. 8D,
When this signal _S3 is at a high level "1" (corresponding to the recording signal S _REC and the erasing signal S _ELASE shown in FIG. 8C), the recording/reproducing switch 13 is switched to the R side, and the magnetic head H _A is in the recording state. On the other hand, when this signal _S3 is at a low level "0", the recording/reproducing switch 13 is switched to the P side, and the magnetic head H _A is placed in the reproducing state. Further, during reproduction, the signal _S3 is set to a low level "0", and the magnetic head _HA is placed in the reproduction state.

Further, the recording signal S _REC from the modulator 8 is supplied to the A side terminal of the changeover switch 14 . In addition, the B side terminal of this changeover switch 14 and the intermediate terminal M
is husband grounded. This changeover switch 14 also operates in the same manner as the changeover switch 9 described above, and a signal _S2 as shown in FIG. 8E is supplied to this changeover switch 14 as a changeover control signal.

A recording signal S _REC is obtained from the changeover switch 14 as shown in FIG.
5. Connect the magnetic head to the recording side terminal R of the recording/reproducing switch 16 and the rotary transformer (not shown).
Supplied to H _B. This recording/playback switch 16 has
Switching control signal from system control circuit 11
_S4 is supplied. During recording, signal S ₄ is shown in Figure 8G.
The signal _S4 is set to high level “1” as shown in
(corresponding to the recording signal S _REC shown in FIG. 8F), the recording/reproducing switch 16 is switched to the R side, and the magnetic head
H _B is put into a recording state, and when this signal _S4 is at a low level "0", the recording/reproducing switch 16 is switched to the P side, and the magnetic head H _B is put into a reproducing state. Also,
During reproduction, the signal _S4 is set to a low level "0", and the magnetic head H _B is placed in the reproduction state.

In addition, in FIG. 6, the reproduction signal _SPB from the magnetic head H _A is transferred to a rotary transformer (not shown), a reproduction side terminal P of the recording/reproduction switch 13, and a reproduction amplifier 17.
A is supplied to the detector 18A through A. The detector 18A shapes the waveform of the reproduced signal _SPB into a pulse signal. The output of this detector 18A is supplied to a clock extraction circuit 19A, and a clock pulse synchronized with the reproduced data is extracted. The output of this clock extraction circuit 19A is the output of the demodulation circuit 20.
A, and reproduced data having the same code structure as the recorded data is obtained.

This reproduced data is supplied to a delay circuit 21A, a synchronous separation circuit 22A, and a CRC checker 23A.
The CRC checker 23A uses a synchronization signal to detect the presence or absence of an error in each block of reproduced data and block address signals using a CRC code, and outputs an error flag indicating the presence or absence of an error in each block. is generated and this is TBC
24. The error flag is, for example, a high level "1" when an error is detected, and a low level "0" when no error is detected. The delay circuit 21A
The reproduced data and block address signal are delayed by the time required for error detection by the checker 23A. This delayed reproduction data and block address signal are supplied to the TBC 24.

In addition, the reproduction signal _SPB from the magnetic head _HB is transferred to a rotary transformer (not shown) and a recording/playback switch 16.
The signal is supplied to the detector 18B through the reproduction side terminal P of and the reproduction amplifier 17B. Detector 18B,
The clock extraction circuit 19B, demodulation circuit 20B, delay circuit 21B, synchronization separation circuit 22B, and CRC checker 23B are composed of the above-mentioned detector 18A, clock extraction circuit 19A, demodulation circuit 20A, and delay circuit 2.
1A, synchronous separation circuit 22A, CRC checker 23
It is configured similarly to A. Therefore, an error flag is generated in the CRC checker 23B, and this
24. In addition, the reproduced data and block address signal delayed by the delay circuit 21B are
It is supplied to TBC24.

The TBC 24 is composed of a memory (RAM) and its peripheral circuits.Basically, data is written using a clock synchronized with reproduced data, and data is written from the memory using a reference clock from the timing generation circuit 25. is read out and the time axis fluctuation is removed. This TBC
Writing to the memory No. 24 is performed using an address based on a block address signal, and writing of data determined to have an error by the error flag is prohibited. As aforementioned,
Since the error flag indicates not only the data but also the presence or absence of an error in the block address signal, when there is an error, writing is prohibited to prevent writing to an erroneous address. Also, if writing is prohibited, the corresponding address will be
Since previously written data remains, an error flag indicating that the data at that address is error data is written to prevent it from being read as correct data. This error flag is written immediately after reading correct data. To read the memory of TBC24,
This is performed sequentially in a predetermined order, and the output includes a data series and an error flag indicating the presence or absence of an error for each block.
6.

The decoder 26 corrects data determined to have an error using an error correction code, and performs correction by replacing uncorrectable data with interpolated data. The interpolated data is, for example, the average value of correct data located before and after. Output data from this decoder 26 is supplied to a D/A converter 27, and a reproduced audio signal is taken out at an output terminal 28.

Further, in FIG. 6, a signal _S5 as shown in FIG. 8H is supplied from the recording system control circuit 11 to the CRC checker 23B.

Since the magnetic heads H _A and H _B are arranged with an angular spacing of θ ₁ as described above, the magnetic heads H _B
scans the same position as the magnetic head H _A with a delay of an angle θ ₁ (distance: l=θ ₁ /360°×2πR, R: radius of drum 3). Therefore, the magnetic head H _B is
After recording by the magnetic head H _A is completed, the recording track formed by the magnetic head H _A is scanned by a distance l. The signal S ₅ is
The high level is “1” during the period of scanning distance,
During other periods, the low level is "0".

The CRC checker 23B extracts the error flag during this high level "1" period,
This is supplied to the system control circuit 11.

The system control circuit 11 generates a signal _S6 in response to the error flag supplied during this period. When the error flag is at a high level "1" (when an error is detected), the signal _S6 is
For example, it is set to a low level "0", and when the error flag is set to a low level "0" (when no error is detected), it is set to a high level "1".

This example is configured as described above, and during recording, the magnetic heads H _A and H _B scan the magnetic tape 4.
Since the recording signal S _REC is sequentially and alternately supplied to each angular range of 180°, recording tracks T _A and T _B are formed on the magnetic tape 4 to the magnetic heads H _A and H _B as shown in FIG. They are formed one after the other. Also, in response to the recording signal S _REC being supplied to the magnetic head H _B ,
Since the erasing signal S _ELASE is supplied to the magnetic head H _A , the previously formed recording track _T0 , for example, is erased by the magnetic head H _A before the recording track is formed by the magnetic head H _B. be done. Here, as mentioned above, magnetic head H _B scans the same location as magnetic head H _A , and magnetic head _{H B} scans at an angle of θ ₁ (distance: l=
Scanning is performed with a delay of θ ₁ /360°×2πR, R; radius of drum 3).

During this recording, if clogging occurs in the magnetic head H _A , the recording signal S _REC will no longer be recorded by the magnetic head H _A. Therefore, the previously formed recording track T ₀ remains where the recording track T _A should originally be formed. In this case, after the magnetic head H A finishes recording, the magnetic head H _B scans the recording track formed by the magnetic head _{H A by} a distance l (the high level of the signal S ₅ is "1"). (period) A signal is reproduced from the recording track _T0 previously formed by the magnetic head H _B. Therefore, during this period, the error flag is set to a low level "0", and the signal _S6 from the system control circuit 11 is set to a high level "1", and it is detected that clogging has occurred in the magnetic head H _A.

On the other hand, when the magnetic head H _A is in a normal state in which no clogging occurs, the recording signal S _REC is recorded by the magnetic head H _A and a recording track T _A is formed. In this case, since the azimuth angle is different from that of the magnetic head H _B , after the recording by the magnetic head H _A is completed, the magnetic head H _B moves l on the recording track formed by the magnetic head H _A. During the period of scanning the distance (the period of high level "1" of the signal _S5 ), no signal is reproduced from the recording track _TA by the magnetic head _HB .
Therefore, during this period, the error flag is at a high level "1" and the signal _S6 from the system control circuit 11 is at a low level "0", causing the magnetic head to
It can be seen that no clotting occurs in H _A.

In this way, the state of the signal _S6 changes depending on whether or not clogging is occurring in the magnetic head H _A , so this signal _S6 can be used to indicate, for example, that clogging is occurring, or, for example, It is also possible to clean the magnetic head H _A by bringing felt into contact with it for a certain period of time.

In this example, during reproduction, the recording/reproducing switches 13 and 16 are switched to the reproduction side terminal P. Therefore, the playback signal _SPB from the magnetic heads H _A and H _B obtained by scanning the recording tracks T _A and T _B formed on the magnetic tape 4 is processed, and the playback audio signal is sent to the output terminal 28 . A signal is extracted.

In this way, according to this example, when recording, the magnetic head
If clogging occurs in H _A , it can be easily detected. Then, countermeasures against this clogging can be taken immediately.

By the way, in this example, if clogging occurs in magnetic head H _B , it cannot be detected, but the signal previously recorded in magnetic head H _A is erased before recording is performed in magnetic head H _B. Therefore, although the amount of data is reduced, it does not cause abnormal noise, and there are fewer problems than with magnetic heads H _A.

In the above-mentioned embodiment, clogging is detected using the signal from the CRC checker 23B, but the following configuration is also possible, for example.

As shown in FIG. 6, the output of the detector 18B is supplied to, for example, a positive terminal of a comparator 30 via a clear current circuit 29, and a reference voltage is supplied to the negative terminal of the comparator 30. And comparator 30
From the output side of the magnetic head H _B , the reproduced signal S _PB
When the signal is satisfactorily obtained, a high level "1" signal is obtained, and in other cases, a low level "0" signal is obtained. The output signal of this comparator 30 is then supplied to a detection circuit 32 via a gate circuit 31.
A signal S ₅ (shown in FIG. 8H) is supplied from the system control circuit 11 to this gate circuit 31 as a gate signal, and the gate is opened at the high level "1" portion. When the output signal of the comparator 30 is at a high level "1", a signal _S7 is obtained from the detection circuit 32, which has a high level "1" and a low level "0", for example.

During recording, if clogging occurs in the magnetic head H _A , the magnetic head H _B
During the period when the recording track formed by the magnetic head H _A is scanned by a distance l (corresponding to the high level "1" part of the signal _S5 ), the recording track previously formed by the magnetic head H _B is scanned. The signal is reproduced from T ₀ . Therefore, during this period, the output of the comparator 30 is at a high level "1", and the signal S ₇ from the detection circuit 32 is
becomes a high level "1", and it is detected that clogging has occurred in the magnetic head H _A.

On the other hand, when the magnetic head H _A is _{in a normal state with no clogging occurring, as described above, after the recording by the magnetic head H A is} completed, the magnetic head H _B A period of scanning the formed recording track by a distance l (corresponding to the high level "1" part of the signal _S5 ),
No signal is reproduced from the recording track _TA by the magnetic head _HB . Therefore, during this period, the comparator 30
The output of the magnetic head becomes low level "0", and the signal _S7 from the detection circuit 32 becomes low level "0".
It can be seen that no clotting occurs in H _A.

In this way, the state of the signal _S7 changes depending on whether or not clogging occurs in the magnetic head _HA .
A signal similar to the signal _S6 in the embodiment described above is obtained.

Effects of the Invention According to the present invention described above, if clogging occurs during recording, it can be easily detected and countermeasures against clogging can be taken immediately.

[Brief explanation of the drawing]

FIGS. 1 to 4 are diagrams for explaining a conventional magnetic recording device, FIGS. 5 and 6 are configuration diagrams showing an embodiment of the present invention, and FIGS. 7 to 9 are diagrams for explaining a conventional magnetic recording device, respectively. It is a figure for the explanation. 3 is a tape guide drum, 4 is a magnetic tape, 11
is a system control circuit, and H _A and H _B are rotating magnetic heads, respectively.

Claims (1)

[Claims] 1. First and second rotating magnetic heads having different azimuth angles are provided at a predetermined angular interval with respect to the rotational direction, and the first and second magnetic heads are arranged so that the first magnetic head moves over the magnetic tape. The magnetic tape is rotated at a predetermined speed while scanning in advance, and recording signals are supplied to the first and second magnetic heads, so that recording tracks by the first and second magnetic heads are alternately recorded on the magnetic tape. After the first magnetic head forms the recording track, the second magnetic head is placed in a reproducing state, and the reproducing signal from the second magnetic head causes the first magnetic head to perform recording. A magnetic recording device characterized in that a state is detected.