JP4816484B2 - Magnetic tape device and servo pattern write-back method thereof - Google Patents

Description

  The present invention relates to a magnetic tape device that performs read / write operations using servo information of a magnetic tape, and that can automatically restore the failure location when a servo band fails, and its servo pattern It relates to the write-back method.

  In a serpentine type single reel magnetic tape device, a cartridge having only one reel (file reel) is loaded, and in response to servo information with a take-up machine reel provided on the magnetic tape device side. Record and play back digital data by running the magnetic tape. At this time, reading / writing is performed by reciprocating the magnetic tape a plurality of times between the file reel and the machine reel while sequentially moving the magnetic track at the beginning and end of the magnetic tape. The magnetic tape is configured to move while meandering in the longitudinal direction of the magnetic tape with respect to a magnetic head assay (magnetic head assembly) having a plurality of pairs of read / write heads corresponding to a plurality of magnetic tracks. .

  In the above-described conventional magnetic tape device, if the servo signal becomes insufficiently output due to the failure of the servo band in which the servo information is recorded, the magnetic head on the magnetic head assay can track the data track. As a result, it became impossible to normally read and write data on the magnetic tape.

  On the other hand, in Patent Document 1, the first guide rollers 5, 6 and the second guide rollers 7, which are inclined in directions opposite to each other with respect to the traveling direction of the magnetic tape 1 with a rotating drum provided with a magnetic head interposed therebetween. 8 and tilting the lower ends of the rotation shafts of the first guide rollers 5 and 6 to the upstream side, the upper edges of the magnetic tape 1 are brought into contact with the upper flanges 9 and 10, and the second guide rollers 7 and 7 By tilting the lower end of the rotary shaft 8 toward the downstream side and bringing the lower edge of the magnetic tape 1 into contact with the lower flanges 11 and 12, the position of the magnetic tape 1 can be regulated with respect to the magnetic head. A magnetic tape recording / reproducing apparatus is disclosed.

  As described above, in the technique described in Patent Document 1, by restricting the position of the magnetic tape running with respect to the magnetic head, the characteristics at the time of recording / reproducing of the magnetic tape can be achieved without damaging the edge of the magnetic tape. However, it is impossible to read or write data on the magnetic tape because the magnetic head cannot track the data track due to the occurrence of a failure in the servo band for controlling the running of the magnetic tape. In this case, there is no description about a technique that enables data recording and reproduction by rewriting servo data to recover a servo band failure.

  In Patent Document 2, the head displacement obtained by the head displacement detector 15 is stored as an absolute position 23 from the reference position in the memory 18 in the positioning controller 8, and the track position on the tape is stored as the absolute position. 23, even when the servo head 12 cannot read the servo track 11, the deviation between the track position and the head position is calculated to generate a drive command signal for the actuator 7. When a servo signal can be obtained from the servo track 11, a magnetic tape device and a control method of the magnetic tape device are disclosed in which a signal switching unit 47 switches to control by a servo signal and performs high-precision positioning.

  As described above, in the technique described in Patent Document 2, in the magnetic tape device, the influence of friction between the tape and the head is eliminated, and positioning in the head width direction is possible with high speed and high accuracy even when the servo track cannot be read. However, due to the occurrence of a failure in the servo band that controls the running of the magnetic tape, the magnetic head cannot track the data track, making it impossible to read or write data on the magnetic tape. In this case, there is no description about a technique that enables data recording and reproduction by rewriting servo data to recover a servo band failure.

  Further, in Patent Document 3, a reference track recording element pair for writing a reference track in addition to a data recording / reproducing element and a reference track reproducing element pair for converting the reference track into a position signal are provided on a magnetic head. I have. The reference track reproducing element pair is arranged so as to be shifted by the data track pitch in the tape width direction, and using this, positioning is performed on a reference track having a width twice the data track pitch. The reference track recording element pair is arranged on the magnetic head so that a reference track can be generated while recording data in cooperation with the reference track reproducing element pair. The effective width of each reference track recording element is the same as the reference track. A magnetic tape device that is the same is disclosed.

As described above, the technique described in Patent Document 3 describes that in a magnetic tape device, data can be recorded while self-generating a reference track for positioning a magnetic head, but for controlling the traveling of the magnetic tape. When the magnetic head cannot track the data track due to the occurrence of a failure in the servo band, and when it becomes impossible to read / write data on the magnetic tape, the servo band is written back to recover the failure of the servo band. There is no description of any technology that enables data recording and playback.
Japanese Patent Laid-Open No. 2002-312995 (FIGS. 6 (a), (b), [0003]) JP 08-255326 A ([0096] to [0098]) Japanese Patent Laid-Open No. 11-203640 (FIG. 2, [0007])

In the conventional magnetic tape apparatus, when the servo band becomes an obstacle, the data cannot be reproduced because the magnetic head on the magnetic head assay cannot track the data track.
The present invention has been made in view of the above circumstances, and by writing back a broken servo pattern at the time of a servo band failure, the failed servo band is repaired and data can be reproduced. An object of the present invention is to provide a magnetic tape device and a servo pattern writing back method thereof.

  In order to solve the above-mentioned problems, a first aspect of the present invention relates to a magnetic tape device, wherein the magnetic tape is guided by a first guide roller and a second guide roller and is arranged between the two guide rollers. And driving the magnetic tape according to the servo data read from the servo band on the magnetic tape by the servo head disposed on the magnetic head assay surface, and the magnetic head In a magnetic tape device that reads / writes a plurality of data tracks in a data band by means of a read / write head arranged on the assay surface, a servo write-back head corresponding to the servo band is provided on the magnetic head assay. Servo with the servo write-back head when the servo band fails Rewriting the data is characterized by being configured to restore the fault servo band.

  According to a second aspect of the present invention, in the magnetic tape device according to the first aspect, when the servo data is written back, the rotation shafts of the first guide roller and the second guide roller are inclined in the same direction. In this way, the relative position between the magnetic head assay and the magnetic tape can be determined and stably run by pressing the edge of the magnetic tape against the flange provided on each guide roller. It is characterized by being.

  According to a third aspect of the invention, there is provided the magnetic tape device according to the second aspect, wherein the flange pressing the edge of the magnetic tape is a flange at the lower end of each guide roller.

  According to a fourth aspect of the present invention, there is provided the magnetic tape device according to any one of the first to third aspects, wherein the servo bands are arranged above and below the data band and are used for servo on the magnetic head assay. The head is composed of upper and lower two corresponding to the servo band, the data band is composed of a plurality of data tracks arranged between the upper and lower servo bands, and the read / write head on the magnetic head assay is It is characterized by comprising a plurality of pairs corresponding to a plurality of data tracks.

  According to a fifth aspect of the present invention, there is provided the magnetic tape device according to the fourth aspect, wherein a plurality of the servo bands are arranged on the magnetic tape, and two adjacent upper and lower servo bands are provided. Each magnetic band has a data band, and the magnetic head assay moves in the vertical direction, so that the upper and lower servo heads on the magnetic head assay are arranged at positions corresponding to the upper and lower two servo bands of either set. The plurality of pairs of read / write heads are configured to be arranged at positions respectively corresponding to a plurality of data tracks in a data band provided between the two upper and lower servo bands. Yes.

  According to a sixth aspect of the invention, there is provided the magnetic tape device according to the fifth aspect, wherein the plurality of pairs of read / write heads are paired according to a traveling direction of the magnetic tape. A read operation is performed, and the other head is configured to perform a write operation.

  According to a seventh aspect of the invention, there is provided the magnetic tape device according to any one of the first to sixth aspects, wherein the magnetic tape device is a serpentine single reel magnetic tape device.

  The invention according to claim 8 relates to a servo pattern writing back method of the magnetic tape device, and the magnetic tape device according to any one of claims 1 to 7, wherein the magnetic tape is driven during a read / write operation on the magnetic tape. If a servo system error occurs and the servo system error cannot be recovered by retry processing, specify the error location and error type. If the error is due to insufficient servo signal output, the servo at the error location A pattern write-back process is performed, and in the case of other servo system errors, an abnormal end based on the occurrence of an error is displayed and the read / write operation is abnormally terminated.

  According to a ninth aspect of the present invention, there is provided the servo pattern write-back method for the magnetic tape device according to the eighth aspect, wherein when a servo system error occurs due to insufficient servo signal output, one of the servo bands above and below the data band is detected. If the servo pattern can be read, write back the faulty servo pattern with reference to the servo pattern that can be read normally, and if both the upper and lower servo bands of the data band cannot be read, tilt the guide roller to tilt the edge of the magnetic tape. With the relative position between the magnetic head assay and the magnetic tape determined by pressing against either the upper or lower flange, the magnetic tape is running stably, referring to the servo pattern before and after the failed part of the above data band. It is characterized by writing back the servo pattern.

  According to a tenth aspect of the present invention, there is provided the servo pattern writing back method of the magnetic tape device according to the ninth aspect, wherein the flange for pressing the edge of the magnetic tape is a flange at the lower end of each guide roller. It is said.

In the magnetic tape device and servo pattern write-back method of the present invention, when the servo band is faulty, either the upper or lower servo band can be normally read by the upper and lower servo write-back heads provided in the magnetic head assay. Can restore the failed servo band by writing back the broken servo pattern based on the servo pattern of the readable servo band.
If both the upper and lower servo bands are broken, the relative position between the magnetic head assay and the magnetic tape is determined by tilting the guide roller with the actuator and pressing the tape edge against the flange above or below the guide roller. By writing back the broken servo pattern based on the servo patterns before and after the failed part in a state where the magnetic tape is running stably, the failed servo band can be recovered.

  Thus, in the magnetic tape device and the servo pattern write-back method of the present invention, the failed servo band can be self-repaired, so that the risk of losing data in the data band can be reduced.

  The magnetic tape is guided by the first guide roller and the second guide roller to run on the surface of the magnetic head assay arranged between the two guide rollers, and the servo head arranged on the surface of the magnetic head assay is used. The drive of the magnetic tape is controlled according to the servo data read from the servo band on the magnetic tape, and a plurality of data tracks in the data band are read / written by the read / write head disposed on the magnetic head assay surface. In the magnetic tape device that performs the servo head, the servo write back head corresponding to the servo band is provided on the magnetic head assay, and when the servo band fails, the servo write back head writes back the servo data to restore the failed servo band. Configure as you can.

  FIG. 1 is a perspective view showing an overall configuration of a serpentine type single reel magnetic tape apparatus according to an embodiment of the present invention, FIG. 2 is a top view showing a state where a cartridge is inserted into the magnetic tape apparatus, and FIG. FIG. 4 is a diagram showing the configuration of the head provided on the magnetic tape contact surface of the magnetic head assay, and FIG. 5 is a diagram showing the magnetic relationship between the roller, the magnetic tape, and the magnetic head assay. FIG. 6 is a diagram illustrating the arrangement of servo information tracks and data recording tracks on the tape, FIG. 6 is a diagram for explaining positioning of the data band by the servo band, and FIG. 7 is a diagram of the magnetic tape device of the present embodiment. It is a flowchart which shows the processing method of the servo system error which generate | occur | produced at the time of read / write.

FIG. 1 is a perspective view showing the entire configuration of a serpentine type single reel magnetic tape device (hereinafter simply referred to as a magnetic tape device) of this example.
The magnetic tape device 11 of this example is schematically constituted by a machine reel 12, guide rollers 13a and 13b, and a threading arm 14. During the operation of the magnetic tape device 11, a cartridge 15 containing a file reel (described later) is loaded into the cartridge insertion portion 16 of the magnetic tape device 11.

  The machine reel 12 is used for temporarily storing file reel data and writing the stored data to the file reel. The guide rollers 13a and 13b have a function of running a magnetic tape (described later) between them. A magnetic head assay (described later) is provided between the guide rollers 13a and 13b, and a plurality of pairs of read / write heads (described later) arranged on the surface come into contact with the magnetic tape to read / write data. Is done. When the magnetic tape device 11 is operated, the threading arm 14 holds the head of the magnetic tape wound around the file reel built in the cartridge 15 and passes it to the machine reel 12 through the guide rollers 13a and 13b.

FIG. 2 is a top view showing a state where the cartridge is inserted into the magnetic tape device. The machine reel 12, the guide rollers 13a and 13b, the cartridge 15, the magnetic head assay 21, and the inside of the cartridge 15 are shown. A file reel 22 and a magnetic tape 23 are shown.
The magnetic tape 23 travels back and forth between the file reel 22 and the machine reel 12 while being rewound from one reel and wound around the other reel while being guided by the guide rollers 13a and 13b. It can be done. The magnetic head assay 21 is placed between the guide rollers 13a and 13b so that a magnetic head (described later) disposed on the surface of the guide roller 13a and 13b contacts the surface of the traveling magnetic tape 23.

FIG. 3 is an elevation view showing the positional relationship among the guide roller, the magnetic tape, and the magnetic head assay. The guide rollers 13a and 13b, the magnetic head assay 21, the magnetic tape 23, It is shown.
The guide rollers 13a and 13b rotate in the same direction to run the magnetic tape 23, but the running direction of the magnetic tape 23 is opposite between reading and writing. The magnetic head assay 21 moves in the vertical direction as indicated by the arrows so that the upper servo head and the lower servo head (described later) are located on either side of the magnetic tape 23. In addition to tracking servo bands (described later), a plurality of read / write heads (described later) provided in the magnetic head assay 21 constitute a data band (described later) provided between two adjacent upper and lower servo bands. It is possible to read and write by tracking a plurality of tracks.

FIG. 4 shows the configuration of the head provided on the magnetic tape contact surface of the magnetic head assay, where (a) shows the magnetic tape contact surface of the magnetic head assay 21, and (b) shows (a). The arrangement | positioning of the magnetic head provided in the A part of the magnetic tape contact surface shown in FIG.
Servo heads 1, 41, 2, 42, a plurality of pairs of read / write heads 43, and servo write-back heads 1, 44, 2, 45 are provided on the magnetic tape contact surface of the magnetic head assay 21. It has been.
The servo heads 1 and 41 provided in the upper part and the servo heads 2 and 42 provided in the lower part are driven and controlled from two adjacent upper and lower servo bands on the magnetic tape 23 (described later). Read the servo information necessary for A plurality of pairs of read / write heads 43 provided between the servo heads 1, 41, 2, 42 read and write data to a plurality of corresponding data bands (described later) on the magnetic tape. The read / write head 43 is a pair of heads arranged on the left and right, and performs a read operation according to the tape running direction in order to perform a verify read (confirmation read) after writing. The head is determined. The servo write-back heads 1 and 44 provided at the upper part and the servo write-back heads 1 and 44 provided at the lower part write back servo information to two adjacent upper and lower servo bands on the magnetic tape 23. I do.

FIG. 5 shows the arrangement of servo information tracks and data information tracks on the magnetic tape 23.
On the magnetic tape, for example, as shown in the figure, servo bands 0 · 55 to 4 · 59 and data bands 0 · 51 to 3 · 54 arranged between two adjacent upper and lower servo bands are provided. Yes.
The tracking of the magnetic head assay 21 with respect to the track on the magnetic tape is performed by two upper and lower servo heads 1, 41, 2 and 42, and two adjacent upper and lower servo bands (for example, servo bands 0 · 55 and 1 · 56). The servo information is used. At this time, the data band to be read / written is an intermediate data band between two adjacent upper and lower servo bands. In the above example, the data band to be read / written is the servo band 0. Data bands 0 and 51 sandwiched between 55, 1 and 56 are obtained.

FIG. 6 explains the selection (positioning) of the data band by the servo band, and the servo band is composed of an array of servo tracks made up of the magnetization pattern 61 as shown.
The servo track provides information for acquiring the position of the read / write head, the speed of the magnetic tape 23, and the position in the vertical direction in the corresponding data track. For the data track shown, the head position is obtained by measuring the pulse times indicated by A1, B1, A2, B2, A3, B3, A4, B4, A5, B5, and the tape speed is determined by four timing signals. The data tracks 0 · 62 to 5 · 63, which are obtained by measuring A1, C1, A2, C2, A3, C3, A4, and C4 and read / write, are indicated in the vertical direction indicated by the intersecting servo tracks. It depends on the position.
Accordingly, the servo control is performed so that the target value and the value actually obtained as described above coincide with each other with respect to the A: B ratio shown in FIG. Is possible. Here, A is a value of A1 and B1, for example, and B is a value of A1 and C1.

  A signal processing unit (not shown) for restoring data from a recording signal on the magnetic tape in the magnetic tape device is a read / write head on which data read / write operation is performed on the magnetic head assay 21. These input / output signals are connected to an external device other than the magnetic tape device through which an external input / output terminal (not shown) is to read / write data from / to the magnetic tape. Thus, when the external device needs to read / write data from / to the magnetic tape, the external device receives read data from the data track on which the read operation is performed, and write data to the data track on which the write operation is performed. Can be sent.

FIG. 7 is a flowchart showing a processing method when a servo system error occurs during read / write in the magnetic tape apparatus of this example.
If a servo error has occurred during the read / write operation (82) after the operation start (81) of the magnetic tape device, but can be recovered by normal retry (83), normal retry processing is performed (84), When the read / write is completed normally (85), the normal end (86) is made. If the read / write is not completed normally (85), the process returns to the read / write operation (82) to check again.
Note that a servo system error is determined according to the type of error, such as a servo signal that cannot be detected at a correct cycle or a weak servo signal output.

If a servo system error has occurred but cannot be recovered by normal retry (83), the peripheral servo area where the error has occurred is analyzed to identify the type of error and the error location (87). If the error is due to insufficient servo signal output (88), the servo pattern is written back (described later) (89), the process ends normally (8A), and if the error is not due to insufficient servo signal output (88). Then, an error occurs in the read / write, the user is informed that the processing has ended abnormally (8B), and ends abnormally (8C).
The error location is specified by position information in the tape running direction (longitudinal direction) embedded in the servo track.

  As described above, according to the magnetic tape device and the servo pattern writing back method of this example, when a failure occurs in the servo band, it can be self-repaired by writing back the servo pattern. In the tape device, the risk of losing data recorded in the data band of the magnetic tape can be reduced.

  FIG. 8 is a diagram showing a configuration for regulating the position of the magnetic tape in the magnetic tape device according to the second embodiment of the present invention, and FIG. 9 is generated at the time of reading / writing in the magnetic tape device of the present embodiment. 5 is a flowchart showing a method for processing a servo system error.

  FIG. 8 shows a configuration for enabling the magnetic tape to run as stably as possible when the magnetic tape passes the magnetic head assay in order to accurately read and write data. A top view, (b) is an elevation view, and (c) is a side view. Other configurations of the magnetic tape device are the same as those in the first embodiment.

As shown in the drawing, when the magnetic tape 23 passes between the guide rollers 13a and 13b, the positions of the upper and lower edges thereof are limited by the upper flange 71 and the lower flange 72 provided on the guide rollers 13a and 13b. It is configured to be.
However, in order to allow the magnetic tape 23 to pass smoothly between the guide rollers 13a and 13b, the width limited by the upper flange 71 and the lower flange 72 is the width of the magnetic tape 23. On the other hand, it is necessary to have a certain margin.
For this reason, while the magnetic tape 23 is traveling, there may be slight fluctuations in the vertical position within the range limited by the upper flange 71 and the lower flange 72. There may be a positional deviation with the read / write head on the head assay 21, and it may not be possible to correctly read / write.

In order to prevent such misalignment, actuators (not shown) are provided for the guide rollers 13a and 13b, and the rotation shafts of the guide rollers 13a and 13b are slightly in the same direction as the direction of travel of the magnetic tape 23. By tilting, the data track on the magnetic tape 23 and the magnetic head assay 21 are moved by running the magnetic tape 23 with the edge of the magnetic tape 23 pressed against either of the upper and lower flanges of the guide roller. It is possible to prevent the occurrence of misalignment with the read / write head.
In this case, either the upper flange 71 or the lower flange 72 may be pressed against the edge of the magnetic tape 23. However, when the weight of the magnetic tape 23 is taken into consideration, it is preferable to press the edge against the lower flange 72 side. It is.

The magnetic tape device 1 is a removable device, and any cartridge 15 of the same standard must be able to read / write. However, if the compatibility between the magnetic tape device and the cartridge is insufficient, the magnetic tape device 1 There may also be combinations where running is not stable.
However, even in such a case, the magnetic tape can be stably run by tilting the guide rollers 13a and 13b and determining the relative position between the magnetic tape 1 and the magnetic head assay 21.

FIG. 9 is a flowchart showing a processing method when a servo system error occurs during read / write in the magnetic tape apparatus of this example.
When either one of the upper and lower servo bands can be read (91) after the operation start of the magnetic tape device (90), the broken servo pattern is written back with reference to the servo pattern that can be read normally (92) ). When the upper and lower servo bands can be read normally (93), the process ends normally (94), and when the upper and lower servo bands cannot be read normally (93), the process returns to step 91. Check again.
At this time, as a method of referring to the servo pattern that can be read normally, the servo patterns of the upper and lower servo bands are the same, so use the servo pattern that can be read normally and break it. You only have to repair the servo band you are on.

When both the upper and lower servo bands cannot be read (91), the magnetic head assay 21 and the magnetic head assay 21 can be obtained by inclining the rotation axes of the guide rollers 13a and 13b and pressing the edge of the magnetic tape 23 against the lower flange 72, for example. In a state where the relative position with respect to the magnetic tape 23 is fixed (95) and stable running is performed, the broken servo pattern is repaired with reference to the servo patterns before and after the error occurrence location (96). When the upper and lower servo bands can be read normally (93), the process ends normally (94). When the upper and lower two servo bands cannot be read normally (93), both servo bands are read. If the number of times that reading is not normal is not more than the prescribed number (97), the process returns to step 91 to check again. If the number of times both cannot be read normally is more than the prescribed number (97), the process ends abnormally (98).
At this time, as a method of referring to the servo pattern before and after the error occurrence location, specifically, since the same pattern is repeatedly recorded, the servo pattern that is broken and the servo pattern before and after the servo pattern are recorded. Can be read repeatedly to restore the servo pattern at the location where the error occurred from the normal servo pattern before and after, and repair the broken servo band. In this case, if the servo pattern in a long section is continuously broken, it may be difficult to repair.

  As described above, according to the magnetic tape device and the servo pattern writing back method of this example, when a failure occurs in the servo band, the guide roller 13a can be used for self-repair by writing back the servo pattern. By tilting the rotation axis of the magnetic tape 23 and pressing the edge of the magnetic tape 23 against the flange, the relative positional relationship between the magnetic head assay and the magnetic tape when the magnetic tape is running is stabilized. Therefore, in the magnetic tape device, the risk of losing data recorded in the data band of the magnetic tape can be reduced.

  The present invention is suitable for application to a serpentine type single reel magnetic tape device. However, the present invention is not limited to this, and a magnetic head is supported so as to be movable up and down between two guide rollers for guiding the magnetic tape. Any magnetic tape device can be used.

1 is a perspective view showing an overall configuration of a serpentine single reel magnetic tape device according to an embodiment of the present invention. It is a top view which shows the state which inserted the cartridge into the magnetic tape apparatus. It is an elevational view showing the mutual positional relationship between the guide roller, the magnetic tape, and the magnetic head assay. It is a figure which shows the structure of the head provided in the magnetic tape contact surface of the magnetic head assay. It is a figure which shows arrangement | positioning of the track for servo information and the track for data recording in a magnetic tape. It is a figure for demonstrating positioning of the data band by a servo band. 3 is a flowchart showing a method for processing a servo system error that occurs during read / write in the magnetic tape device of the same embodiment. It is a figure which shows the structure for regulating the position of a magnetic tape in the magnetic tape apparatus which is 2nd Example of this invention. 3 is a flowchart showing a method for processing a servo system error that occurs during read / write in the magnetic tape device of the same embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 11 Magnetic tape apparatus 12 Machine reel 13a, 13b Guide roller 15 Cartridge 16 Cartridge insertion part 21 Magnetic head assay 22 File reel 23 Magnetic tape 41 Servo head 1
42 Servo head 2
43 read / write head 44 write back head 1
45 Write-back head 2
51 Data band 0
52 Data Band 1
53 Data Band 2
54 Data Band 3
55 Servo Band 0
56 Servo Band 1
57 Servo Band 2
58 Servo Band 3
59 Servo Band 4
61 Magnetization pattern 62 Data track 0
63 Data track 5

Claims (10)

A magnetic tape is guided by a first guide roller and a second guide roller and travels on the surface of a magnetic head assay arranged between the two guide rollers, and the servo head is arranged on the surface of the magnetic head assay. A plurality of data tracks in the data band by controlling the driving of the magnetic tape according to servo data read from the servo band on the magnetic tape by the read / write head disposed on the surface of the magnetic head assay. In a magnetic tape device that reads / writes
A servo write-back head corresponding to the servo band is provided on the magnetic head assay so that when the servo band fails, the servo write-back head can write back servo data and restore the failed servo band. A magnetic tape device characterized by being configured.   When writing back the servo data, the edges of the magnetic tape are pressed against the flanges provided on the respective guide rollers by tilting the rotation axes of the first guide roller and the second guide roller in the same direction. 2. The magnetic tape device according to claim 1, wherein the magnetic head device is configured so that the relative position between the magnetic head assay and the magnetic tape can be determined and stably run.   3. The magnetic tape device according to claim 2, wherein the flange for pressing the edge of the magnetic tape is a flange at the lower end of each guide roller.   The servo bands are arranged above and below the data band, and the servo head on the magnetic head assay consists of two upper and lower parts corresponding to the servo band, and the data band is between the upper and lower servo bands. 4. The read / write head on the magnetic head assay includes a plurality of pairs corresponding to the plurality of data tracks. 5. Magnetic tape unit.   A plurality of servo bands are arranged on the magnetic tape, and each has a data band between two adjacent upper and lower servo bands, and the magnetic head assay moves in the vertical direction, thereby The upper and lower servo heads on the magnetic head assay are arranged at positions corresponding to the upper and lower two servo bands of either set, and the plurality of pairs of read / write heads are located between the upper and lower servo bands. 5. The magnetic tape device according to claim 4, wherein the magnetic tape device is configured to be arranged at a position corresponding to each of a plurality of data tracks in a provided data band.   The plurality of pairs of read / write heads are configured such that one of the heads in a pair performs a read operation and the other head performs a write operation according to the traveling direction of the magnetic tape. 6. The magnetic tape device according to claim 5, wherein:   The magnetic tape device according to any one of claims 1 to 6, wherein the magnetic tape device is a serpentine single reel magnetic tape device.   8. The magnetic tape device according to claim 1, wherein an error occurs in a servo system that drives the magnetic tape during a read / write operation on the magnetic tape, and the servo system error cannot be recovered by retry processing. , Specify the error location and error type, and if the error is due to insufficient servo signal output, write back the servo pattern at the error location, and for other servo system errors, based on the error occurrence A servo pattern write-back method for a magnetic tape device, wherein abnormal read is displayed and the read / write operation is abnormally terminated.   When a servo system error occurs due to insufficient servo signal output, if one of the servo bands above and below the data band can be read, the servo pattern that failed is written back with reference to the servo pattern that can be read normally, and the data If both the upper and lower servo bands cannot be read, tilt the guide roller and press the edge of the magnetic tape against one of the upper and lower flanges to fix the relative position between the magnetic head assay and the magnetic tape. 9. The servo pattern write-back of the magnetic tape device according to claim 8, wherein the servo pattern having a fault is written back with reference to servo patterns before and after the faulty part of the data band in a state where the tape is stably run. Method.   10. A servo pattern writing back method for a magnetic tape device according to claim 9, wherein the flange pressing the edge of the magnetic tape is a flange at the lower end of each guide roller.

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