JP2539452B2 - Helical scan type magnetic tape storage device - Google Patents

Description

The present invention relates to a helical scan type magnetic tape storage device suitable for storing digital data.

[Conventional technology]

The helical scan type magnetic tape device has a higher recording density than that of the fixed head type magnetic tape device, and is therefore widely used in a field requiring a large amount of information such as a VTR. Also, with the recent development of VTR technology, a large number of household VTRs are produced at low cost, and their spread is remarkable. Further, there is an R-DAT (digital audio tape recorder system) for recording / reproducing musical sound PCM signals on a tape stored in a cassette case. This DAT is for recording digital signals, and if the diameter of the cylinder on which the magnetic head is mounted is 30 mm, the tape is wound around the rotating drum at a small angle of 90 degrees, so there is little damage to the tape, and at high speed. It has the function of playing and accessing the tape while it is running, making it suitable as a storage device for computers.
By using this DAT technology, a large-capacity and inexpensive magnetic tape storage device can be realized. Explaining the DAT, FIG. 10 is a schematic configuration diagram of the tape running system, in which 1 is a rotating drum, 2a and 2b are magnetic heads attached to the drum 1 and having different azimuth angles of ± 20 degrees, 3 is a magnetic tape, Reference numerals 4a, 4b and 4c denote tape running means composed of guide posts, capstans and pinch rollers for winding the tape 3 around the drum 1 for running, and
Is a tape cassette. Tape 3 is 3.81 mm wide and 13 thick
μm. According to the standard, the sampling frequency of A conversion,
There are several modes depending on the number of bits in one word, the number of channels, etc. Explaining the standard mode, tape 3 has a running speed of 8.15 mm, capstan 4b, pinch roller.
Driven by 4c. The drum 1 is rotating at 2000 rpm, and the tape 3 is diagonally wound 90 degrees at a lead angle of 6 degrees and 22 minutes by the running means 4a, and the magnetic head is fed.
Signals are recorded or reproduced on the tape with 2a and 2b. FIG. 11 shows the pattern of recording tracks recorded on the tape as described above. In FIG. 11, 6 is a track recorded by the magnetic head 2a, and 7 is a track recorded by the magnetic head 2b. The track pitch P is 13.6 μm, the track length L is 23.501 mm, and the recording width W is 2.613 mm. Figure 12 shows the recording format on the magnetic tape.
The 16-bit PCM signal is divided into 8 bit units (symbols) and recorded. As shown in Fig. 12b, one block is composed of 32 symbols of data and a synchronization signal (SYN
C), ID code, block address, and parity for detecting errors in ID code and block address. The ID code is a signal for identifying the sampling frequency and the number of channels of the PCM signal. In the I track, 128 blocks of PCM signal is about 60 at the center.
There are areas for recording the ATF signal for tracking control on both sides thereof, and further, 16 blocks of sub-code areas of 8 blocks are arranged on both sides thereof. The order of programs, time, etc. are recorded in the subcode area, and the configuration of this block is the same as that of the PCM signal area.

By the way, as a storage device of a computer, data reliability is a very important factor. Therefore, in the case of recording data in a flexible disk device or a fixed magnetic disk device, first, the data to be recorded is recorded on the magnetic disk, and then the data is reproduced to check whether the data is correctly recorded, If there is an abnormality, the verify operation is performed by re-recording or recording in the alternative sector. Also, DAT and PCM recorders use error correction codes in order to improve the reliability of data. In the case of audio signals, even if an uncorrectable error occurs about once every 30 minutes, it cannot be said to be a fatal error.
It is not necessary to confirm the recorded data. However, when used as an external storage device of a computer, any small error can be fatal, so it is necessary to confirm whether it is recorded normally to avoid erroneous recording due to defects in the magnetic tape or intrusion of foreign matter. necessary. Further, it is necessary to have a function of partially modifying already recorded data and rewriting it in the same place again, or connecting and recording later. Japanese Patent Laid-Open No. Sho 58-58 is an example of checking whether recording is properly performed in the helical scan type and an example of after-recording.
-122606, JP-A-61-39909, and JP-A-59-195306.

[Problems to be solved by the invention]

In the helical scan type, the magnetic tape runs at a constant speed, and the recording track is a combination of the speed vectors of the rotating drum and the tape. Therefore, in the conventional magnetic head configuration, the magnetic head automatically moves to the next track, and the recorded data cannot be reproduced and confirmed. When the running of the magnetic tape is stopped, since the recording track is determined by the relative position of the rotating magnetic head and the running magnetic tape, the magnetic head is displaced from the track and the signal cannot be correctly reproduced. Further, intermittently driving the tape not only places a great burden on the tape drive control device, but also requires start-up and stop time, which is not preferable.
Further, in order to reproduce and confirm the recorded data once, it is possible to rewind the magnetic tape and then run the tape again to reproduce the data, but it takes a long time to rewind the tape and restart the running. It takes time and confirmation of this type of data is not practical. In order to realize the verify function, it is sufficient to reproduce immediately after recording and match the recorded content with the reproduced content, but it is difficult to reproduce while recording because the reproduction signal is weak.
Therefore, the angle between the recording head and the reproducing head must be equal to or larger than the recording angle (corresponding to the winding angle) on the tape. In DAT, azimuth recording is performed in which recording is performed alternately without providing a guard band, and the recording width of the magnetic head is usually larger than the track pitch. At the time of reproduction, the off-track amount is detected by the above-mentioned ATF signal, and the negative feedback closed loop is configured so that the center of the reproducing head in the width direction comes to the center of the recording track to control the tape running. Since the gap width is larger than the track pitch, when one track is written, the tracks before and after that are deleted, and it is difficult to rewrite only one track or only one part of one track after recording once. Is. This problem can be solved by constructing one block with a plurality of tracks as a unit and rewriting it in block units. However, if the ATF signal area for tracking control is also rewritten, it is caused by a difference in temperature difference between the tape speed and the cylinder rotation speed. There is a problem that there is a risk of eroding adjacent blocks due to the influence of expansion and the like while rewriting many times. It is an object of the present invention to provide a highly reliable magnetic tape storage device that solves such problems.

[Means for solving problems]

The purpose is to set a tape winding angle to the rotating cylinder and a recording angle to 90 degrees, and a first pair of magnetic heads having different azimuth angles and arranged at 180 degree intervals on the rotating cylinder, and perpendicular to the pair. A second pair of magnetic heads having different azimuth angles, which are mounted and displaced by a half of the scanning track width of the second magnetic head in the height direction of the cylinder, and a plurality of tracks are used as a unit. When one block is configured and data is written and read in units of blocks and one block is rewritten, the AT reproduced by the second magnetic head is used.
While the tracking control is performed by the tracking control signal obtained from the F signal, AT is performed by the first magnetic head.
It is achieved by rewriting only the data area excluding the F area.

[Action]

When newly recording, recording is performed by one of the first magnetic heads, then by the second magnetic head having the same azimuth angle, the immediately preceding recording track is reproduced, and the first recording head is sequentially confirmed while confirming whether or not the recording is correctly performed. Recording is performed with the magnetic head of 1. Since the gap width of the magnetic head is larger than the track pitch, the recorded width is overwritten by the amount corresponding to the difference between the gap width and the pitch when recording the next track. The second magnetic head has a gap width of the second magnetic head that is 2
Since it is attached by being shifted by a factor of 1 in the height direction of the rotary cylinder, the center of the gap of the second magnetic head and the recording track previously recorded by the first magnetic head are recorded next. The center of the recording track remaining after overwriting by the head will coincide, and the gap with the gap center of the first magnetic head to be recorded next is the gap width W of the first magnetic head.
If 1 and the track pitch is P, it becomes (W1 + P) / 2.

At the time of reproduction, the gap center of the second reproducing magnetic head is aligned with the center of the recording track by returning to the rotation control of the capstan motor that drives the tape based on the signal indicating the off-track amount obtained from the ATF area. Tracking control. When a certain block is rewritten, the second magnetic head reproduces the data for tracking control, and the subsequent first magnetic head does not perform the tracking control and records only the data area excluding the ATF area. The second magnetic head is positioned at the center of the recording track by tracking control, and the distance between the second magnetic head and the gap center of the succeeding first magnetic head is expressed by the above equation, so that the recording after rewriting is performed. The track matches the ATF area that has not been rewritten, and the center of the rewritten recording track and the track center obtained from the ATF signal match.

〔Example〕

 Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 shows an operation at the time of so-called after-recording for rewriting already recorded data, 101 is a recording track train, 102 is an area in which a signal for tracking control is recorded, 203A, 203B, 203C, 203D are The gap of the rotating magnetic head is shown, and the trace order is 203A → 203C → 203B → 203D.
→ 203A ……. As shown in the first embodiment of FIG. 1B, while reproducing with the reproducing rotary magnetic heads 203C and 203D and applying the tracking servo, a portion corresponding to the data area is delayed by 90 degrees from the reproduced signal. Recording is performed by the recording rotary magnetic heads 203A and 203B. The gaps 203C and 203D of the reproducing rotary magnetic head are positioned at the center of the recording track by the tracking servo, and the left ends of the gaps 203A and 203B of the recording magnetic head coincide with the left end of the recording track. FIG. 1C shows another embodiment, in which the recording / reproducing magnetic head 20 is reproduced by reproducing with the reproducing rotary magnetic heads 203C and 203D and applying the tracking servo.
It reproduces by 3A and 203B, detects the end of the tracking control signal area, and records only the data area. The details will be described below.

FIG. 2 is a side half view showing the structure of a drum on which a magnetic head is mounted, and FIGS. 3 and 4 are a plan view and a side view showing the structure of a rotary drum on which a magnetic head is mounted. 201 is a fixed drum, 202 is a rotary drum 203 is a magnetic head fixed to the rotary drum 202, 204 and 205 are rotary transformers, 206
Is a rotating shaft, 207 is a magnet which is a motor rotor, 208 is a motor stator coil, 209 is a coil for detecting the number of rotations of the motor, a hall element for detecting the rotation phase of the rotor 207, and one for one rotation of the motor. A detection substrate 210 provided with a Hall element for detecting a pulse signal (hereinafter referred to as a tack pulse) is a lead for helically winding a magnetic tape on the fixed drum 201. Rotating drum 202
Is fixed to the rotary shaft 206. Magnetic head 203a, 203
b, 203c, 203d are arranged by dividing them by 90 degrees, and 203a and 2
03c, 203b and 203d have the same azimuth of ± 20 degrees. Tape running speed is μ (m / sec), magnetic head rotation speed (≒ drum peripheral speed) is υ (m / sec), drum rotation speed is n
(Rpm), the lead angle is α (degrees), and the division angle of the magnetic head is β (degrees), the track angle θ (degrees), the relative speed V between the magnetic head and the tape, and the track pitch P are expressed by the following equations. It

The magnetic heads 203c and 203d are mounted on the rotary drum 202 with a spacer 211 interposed therebetween, and the indexing angle of each head is 90 degrees, so there is no step between the magnetic heads 203a and 203b and the magnetic heads 203c and 203d. When the magnetic head 203
The c and 204d are displaced from the recording tracks of the magnetic heads 203a and 203b by a half track pitch for scanning.
Since the step and the scanning track pitch shift correspond to each other on a one-to-one basis, the magnetic heads 203c and 203d can be attached to the magnetic heads 203c and 203b by shifting the magnetic heads 203a and 203b downward by a half of the scanning gap width. The magnetic head 20 which is the center of the gap and the track previously recorded by the magnetic head 203a is the next recording head.
The center of the recording track that remains after being overwritten by 3b will match, and the distance from the gap center of the magnetic head 203b to be recorded next will be the same as that of the magnetic head 203b.
When the gap width of a and 203b is W1 and the track pitch is P, it becomes (W1 + P) / 2. FIG. 5 shows magnetic heads 203a, 203b, 20
3C and 203d show the scanning track positional relationship.

FIG. 6 is a system block diagram of the apparatus in the first embodiment. The host computer (not shown) is connected by SCSI 401 (small size computer system interface). RAM controller 402 controlled by system microcomputer 412 during recording
Stores the data sent from the host in the RAM 403 once, reads it again, and the signal processing circuit 404 causes the error correction circuit 405 to generate an error correction code, and stores the data signal and the error correction code in the RAM 406. Here, the error correction code is the conventional DA
Like T, it is a dual Reed-Solomon code. Next, this data signal and error correction code and subcode processing
The subcode data generated in 411 is read according to the recording format, is subjected to predetermined modulation, and the ATF generation circuit 408
The tracking control signal and the synchronization signal generated in step 409 are added by the multiplexer 409, and the magnetic tapes 413 are transmitted from the magnetic heads 3A and 3B through the recording amplifier 410 and the rotary transformer.
To record. The recording format is based on the conventional DAT recording format shown in FIG.
Data is recorded in the signal area, and block numbers, frame numbers, etc. are recorded in the subcode area.
The rotation speed of the rotary drum 2 is detected and the speed is controlled, and the phase is controlled so that the tack pulse is synchronized with the reference signal and the drum control circuit 433 controls the rotation of the rotary drum 2 at a constant speed. The magnetic head is driven at a constant speed by a capstan motor 434 whose rotation is controlled by a circuit 432 at a constant speed, and the tack pulse is used as a reference.
Recorded by 203a and 203b. At this time, verify circuit 4
Reference numeral 29 reproduces the data recorded by the magnetic heads 203c and 203d immediately afterward to verify whether or not the data is correctly recorded. The unit of verification is performed in units of blocks to be described later, but the description is omitted because it is not directly related to the present invention.

At the time of reproduction, an AT for tracking control recorded by being arranged at both ends of the data signal by the magnetic heads 203c and 203d.
The F signal is fed back to the capstan motor to perform tracking servo and reproduce the signal.
The reproduction signal is amplified by the reproduction amplifier 420, and the waveform equalization circuit 421
After the characteristic deterioration of the magnetic head and the magnetic tape in the short wavelength region is compensated by, the data is input to the data strobe circuit 422, and the data and the clock are obtained. From this signal, the synchronization signal detection circuit 423 and the timing generation circuit 424 generate the synchronization signal detection and timing signal, and the demodulation circuit
Data is demodulated at 425, the signal processing circuit 426 performs an error detection and correction operation by the error correction circuit 427,
After the corrected data signal is stored in RAM403, SCSI
It is sent to the host computer via the interface. The operation of the tracking servo is similar to that of the conventional DAT, so detailed description will be omitted.

FIG. 7 shows the configuration of blocks, and in this embodiment, 2
A track is one frame, and 32 frames form one block. All zeros are recorded in the data areas of the first 6 tracks and the second 2 tracks of each block. This is a gap for absorbing post-recording on a block-by-block basis and absorbing disturbance in alignment between blocks that occurs when continuous recording is performed. Next, the case of rewriting a certain block of the tape which has already been recorded will be described. FIG. 8 is an operation explanatory diagram when searching for a desired block, showing the tape speed and the reproduction signals of the magnetic heads 203c and 203d.
The reproduced block number is shown. The search operation is performed while the tape is running at a high speed while the relative speed between the tape and the head is controlled to be equal to that during normal reproduction, but the description thereof is omitted because it is not directly related to the present invention. The reproduction operation is started from a block at least one before the desired block, and the pull-in operation of the tracking servo is completed by the time it reaches the block immediately before the target block. The synchronization signal detection circuit 423 is used for the magnetic head 203.
For example, the head of SUB-1 in the subcode area is detected from the signal obtained by reproduction with C and 203D, and based on the detected signal, the timing generation circuit 424 causes the signal processing circuit 404 to detect the signal processing circuit 426. In contrast, the distance between the recording / playback head is 90.
The operation timing is controlled to be delayed by a degree. When the desired block is reached, recording is started at the portion corresponding to the rear end of the IBG of ATF1 in the ATF area of the recording format shown in FIG.
Only the data area is overwritten and rewritten, and the verify operation described above is performed at this time as well. Tracking control is performed by the magnetic heads 203c and 203d, and the tracking error signal is held during recording. The winding angle of the tape on the drum is 90 degrees, and the indexing angle of the magnetic head is also 90 degrees, so it is very short time that two magnetic heads contact the tape at the same time.
Crosstalk is not a problem. Since the scanning track of each magnetic head is as shown in FIG. 5, for example, when the magnetic head 203c is on-track by the tracking control, the gap edge of the succeeding magnetic head 203b is the recording track already recorded. Thus, the track center of the rewritten data area and the track center obtained from the ATF signal match. In the last track of the block, the scanning track width of the magnetic head is larger than the track pitch, so that the next recording track is deleted. However, since this track is a gap track, it is also possible to reproduce it later. It does not hinder. Further, in the first track to be rewritten, there is a case where the unerased portion of the previous recording track may occur, but it is clear that this is not a problem because it is a gap track.

FIG. 9 shows an embodiment of the rotary transformer of this apparatus. As described above, the magnetic heads 203a and 203b are for recording only, and the magnetic heads 203c and 203d are for reproduction only. One channel of the rotary transformer is connected in series. If a 4-channel rotary transformer is housed in a drum with a diameter of 30 mm, the transmission efficiency of the transformer is reduced, the SN ratio of the reproduced signal is deteriorated, and the reproduced signal quality is deteriorated. According to the present embodiment, since the rotary transformer requires only three channels, it is possible to minimize the reduction in the transmission efficiency of the rotary transformer due to the increase in the number of heads.

In the second embodiment shown in FIG. 1C, the timing generation circuit 424 detects the start point of the data area from the reproduction signals of the magnetic heads 203a and 203b, and the data area is rewritten. In this case, since the starting point of the data area is detected while reproducing the track itself to be rewritten, there is an effect that the deviation of the area can be reduced.

〔The invention's effect〕

As described above, according to the present embodiment, in the after-recording on the already-recorded portion, the tracking control remains the operation during reproduction, and the track center indicated by the tracking control signal and the rewritten recording track center match. Since the data signal area can be rewritten as described above, the tracking signal area that has not been rewritten matches the track, and the rewritten data can be written correctly across multiple blocks without lowering the reproduction level of the data signal. Can be played. Also, after recording, the verify operation can be performed as in normal recording, so
The reliability during after-recording can be improved. Furthermore, when the two pairs of magnetic heads are used exclusively for recording and reproduction, respectively, the gap length of the magnetic heads can be optimized, and high quality recording and reproduction can be performed and reliability can be improved.

Further, since the reproducing head traces after the recording (or recording / reproducing) head, verification is possible, and since the winding angle and the angular interval of the head are both 90 degrees, crosstalk can be avoided. That is, the recording operation and the verify operation are alternately performed according to the rotation of the drum, and a recording signal which is a relatively large signal does not flow during the verify operation. Therefore, the verification is not disturbed by the interference of the recording signals.

Further, by adopting a configuration in which recording and reproduction are performed by dedicated heads respectively, it is possible to optimize the structure of each head and rotary transformer.

Further, in the present invention, azimuth recording is performed without providing a guard band. However, unerased recorded data may be left unrecorded on the track at the beginning of the post-record, or the last track of the post-record may be recorded on the next track. become. Therefore, normal reading and writing cannot be performed in these parts. However, according to the present invention, after-recording is performed in units of blocks, and the track at the start of the after-recording and the last track are not used for storing valid data as gap tracks that are invalid data. Even if it goes, all valid data can be read normally.

Further, the structure is such that recording and reproduction are performed by dedicated heads, and the gap length of each head is optimized for recording and reproduction, so that highly reliable recording and reproduction becomes possible.

[Brief description of drawings]

FIG. 1 is an operation explanatory view during after-recording, FIG. 2 is a side half sectional view showing a structure of a drum, FIG. 3 is a plan view showing a magnetic head mounted on a rotary drum, and FIG. FIG. 3 is a side view of FIG. 3, FIG. 5 is a track scanning explanatory diagram of each magnetic head, FIG. 6 is a system block diagram of the apparatus, and FIG.
Block diagram, FIG. 8 is an operation diagram at the time of after-recording, FIG. 9 is a connection diagram showing an embodiment of a rotary transformer and a magnetic head, FIG. 10 is a tape traveling system path diagram of a conventional DAT, FIG. 11 is a recording track pattern diagram of a conventional DAT, and FIG. 12 is a recording format diagram of a conventional DAT. 101 …… Magnetic track 203a, 203b, 203c, 203d …… Magnetic head

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Toru Sampei 292 Yoshida-cho, Totsuka-ku, Yokohama-shi, Kanagawa Inside Home Appliances Research Laboratory, Hitachi, Ltd. (56) Reference JP-A-58-139318 (JP, A) JP-A-SHO 63-2107 (JP, A)

Claims (3)

(57) [Claims] 1. A first pair of rotary magnetic heads having different azimuth angles arranged on a rotary drum at an angular interval of 180 degrees, and an angular interval of 180 degrees arranged substantially orthogonal to the first rotary magnetic head. And a second pair of rotary magnetic heads having different azimuth angles arranged on a plane different from that of the first pair of rotary magnetic heads on the rotary drum, and a magnetic tape is helically wound around the rotary drum. In a circular shape, the first pair of rotary magnetic heads are provided with a recording gap width wider than the track pitch, and the magnetic tape is sequentially scanned diagonally to provide a guard band. Without performing azimuth recording, an inclined track is formed, and at least a data signal and a tracking control signal for tracking control during reproduction are respectively formed on the inclined track. When recording and forming new data on the magnetic tape by rear division, recording the data signal and the tracking control signal by the first pair of rotary magnetic heads, and recording by the second pair of rotary magnetic heads. In a helical scan type magnetic tape device having a verify function for sequentially reproducing an inclined track immediately after, the first and second pair of rotating magnetic heads are for recording and reproducing, respectively, and the second pair of rotating magnetic heads. The magnetic head is attached to a plane that is half the reproduction gap width of the second pair of rotary magnetic heads below the plane of attachment of the first pair of rotary magnetic heads to the rotary drum. It has an after-recording function of rewriting the portion of the data signal without rewriting the tracking control signal, and constitutes one block with a plurality of inclined tracks as a unit. The helical scan type magnetic tape storage device is provided with signal processing means for reading and writing recorded data in units of this block, and for making the data signals at the beginning and the rear of the constituent blocks invalid data. . 2. The helical scan according to claim 1, wherein the first pair of rotary magnetic heads and the second pair of rotary magnetic heads have different head gap lengths. Method magnetic tape storage device. 3. A first pair of rotary magnetic heads having different azimuth angles arranged on a rotary drum at an angular interval of 180 degrees, and an angular interval of 180 degrees arranged substantially orthogonal to the first rotary magnetic head. And a second pair of rotary magnetic heads having different azimuth angles arranged on a plane different from that of the first pair of rotary magnetic heads on the rotary drum, and a magnetic tape is helically wound around the rotary drum. In a circular shape, the first pair of rotary magnetic heads are provided with a recording gap width wider than the track pitch, and the magnetic tape is sequentially scanned diagonally to provide a guard band. Without performing azimuth recording, an inclined track is formed, and at least a data signal and a tracking control signal for tracking control during reproduction are respectively formed on the inclined track. When recording and forming new data on the magnetic tape by rear division, recording the data signal and the tracking control signal by the first pair of rotary magnetic heads, and recording by the second pair of rotary magnetic heads. In a helical scan type magnetic tape device having a verify function for sequentially reproducing the immediately following inclined track and an after-recording function for rewriting a portion of a data signal without rewriting the tracking control signal, the first pair of rotary magnetic heads include: The second pair of rotary magnetic heads are also used for recording and reproduction, and the second pair of rotary magnetic heads are for reproduction, and the second pair of rotary magnetic heads are planes for mounting the first pair of rotary magnetic heads on the rotary drum. On the other hand, the tracking control is mounted on a plane that is ½ of the reproduction gap width of the second pair of rotary magnetic heads. It has an after-recording function of rewriting a portion of a data signal without rewriting a signal, and constitutes one block with a plurality of inclined tracks as a unit, and provided with a signal processing means for reading and writing recording data by this block as a unit. A helical scan type magnetic tape storage device characterized by the above.