JP2006221729A - Linear tape driving device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To raise a servo control performance while obtaining a sufficient SN ratio to narrowed track pitches, and also secure compatibility with linear tapes of two or more generations, relating to a device which has 1st and 2nd servo tracks of a predetermined width formed alternately, and performs reproduction except burst signals A, B each of which is intermittently recorded in the longitudinal direction of the servo tracks, and performs tracking servo control based on a difference between the respective reproduced signals. <P>SOLUTION: A 1st servo read head S1 is disposed so that a width-directional intermediate position may counter with the borderline of the 1st servo track and the 2nd servo track, and a 2nd read head S2 is disposed on the burst A side shifted from the servo read head S1, for example, by a half track pitch. The servo read heads S1, S2 are changed over in order of (1), (8), (3), (10), and (5) as shown so as to use signal parts having good linearity of the difference signal between the bursts A, B. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention provides a linear tape in which a servo band having a plurality of servo tracks along the longitudinal direction of the magnetic tape and a data band having a plurality of recording tracks along the longitudinal direction of the magnetic tape are alternately formed in the tape width direction. The present invention relates to a linear tape drive device to be used.

  In LTO (Linear Tape Open) drives, which are typical linear tape products, servo heads are arranged so as to sandwich both sides of the multi-data head for tracking position control. This means that the distance from the servo head on one side to the furthest channel of the data head is about 2700 μm, and considering the change in temperature and humidity of the tape is about 1200 ppm, the worst track deviation of 3.2 μm will occur.

  In order to reduce this effect, servo heads are placed on both sides of the multi-data head, and servo control is performed to balance the two servo heads on both sides, thereby halving the effects of tape temperature and humidity changes. It is possible to make it.

  FIG. 4 shows the relationship between the linear tape described above and the multi-channel magnetic head portion of the linear tape drive apparatus. The magnetic tape T has a servo band having a plurality of servo tracks along the longitudinal direction of the tape. The SB and the data band DB having a plurality of recording tracks are alternately formed in the tape width direction.

  In the servo band SB, servo data for tracking servo is written in advance at a factory by a servo pattern writing device called a servo track writer (STW) and shipped to a user. Reference numeral 1 denotes a multi-channel magnetic head unit which is arranged opposite to the magnetic tape T and performs recording and reproduction, and a plurality of magnetic head elements are arranged.

  FIG. 5 shows an example of the configuration of the surface of the magnetic head unit 1 that faces the magnetic tape T, and only the magnetic band of one data band DB and the portion that is disposed opposite to the upper and lower servo bands sandwiching it. This represents the arrangement of the heads.

  In the magnetic head portion 1, first and second magnetic head stack portions 11 and 12 in which magnetic head elements are arranged are juxtaposed. In a portion facing the data band of the first and second magnetic head stack portions 11 and 12, the recording magnetic head element 1W and the reproduction magnetic field are formed on the tracks whose centers are indicated by CT1, CT2, CT3. The head elements 1P are linearly arranged with a predetermined magnetic gap. 1S is a servo signal reproducing magnetic head element arranged at a position facing the servo band.

  For example, in the traveling path of the magnetic tape, a data signal is recorded by each recording magnetic head element 1W in the first stack section 11, and this recording is performed in the other second stack section 12 juxtaposed with each magnetic head element 1W. Reproduction is performed by the reproduction magnetic head element 1P, and for example, a recording state is monitored.

  Further, for example, on the return path of the magnetic tape traveling, data signal recording is performed by each recording magnetic head element 1W in the second stack section 12, and this recording is reproduced by the reproducing magnetic head element 1P in the first stack section 11.

  Tracking with respect to the data track of the magnetic head element in the recording / reproducing is performed by reading the servo data signal for head position control recorded in the servo bands arranged on both sides of the target data band DB.

  The LTO drive uses a timing-based servo system (Timing Based Servo system) that detects track position information by detecting a phase difference, and a C-shaped pattern is written on the tape as a servo signal. As a merit of this method, since the signal on the straight line with an inclination of 6 ° is written to full servo band, it becomes possible to change the track pitch steplessly, and the flexibility when considering generation compatibility is increased. I can take it. For this purpose, it is possible to eliminate the need for capital investment of the servo track writer (STW) of the servo pattern writing device for writing the servo signal at every generation change.

  However, there is a strict requirement for time axis resolution for phase difference detection. For example, as described in Patent Document 1, a multi-phase clock is used so as not to increase the reference clock frequency as much as possible. Yes.

  As the tape speed increases in order to increase the data transfer rate in the future, the reference clock for phase detection will be on the order of 1 GHz, and the clock wiring delay (Skew) and application specific integrated circuit (ASIC; user) In reality, it is facing the limit of the processing capability of ICs that can be designed (application-specific integrated circuits), and the resolution cannot be improved in the future.

In addition, there are concerns about the problem of heat generation of the IC due to higher clock speeds, and there will be secondary problems such as cost increase due to the addition of cooling mechanism and increase in drive size.
JP 2000-123335 A

  As another typical servo system, the amplitude reference servo system that has been used for a long time in HDD etc. for the timing reference servo system represented by the above-mentioned LTO, and has been used for 9840, 9940 etc. even in linear tape format ( Amplitude Based Servo method).

  For example, as shown in FIG. 6, a servo signal arranged in a checkered pattern is detected, and track position information is detected from a signal difference between adjacent servo signals. FIG. 6A shows a part of a plurality of servo tracks formed in one servo band. For example, a first servo track and a second servo track having a track width (track pitch) of 10 microns are shown. A plurality of lines are alternately formed in the tape width direction.

  A burst signal of burst A is intermittently formed in the tape longitudinal direction of the first servo track, and burst B is intermittently formed in the tape longitudinal direction of the second servo track adjacent to the first servo track. A burst signal is formed (in FIG. 6A, only one burst A and one burst B are shown, but a plurality of these bursts A and B are intermittently provided in the longitudinal direction of the tape. Are formed to form a servo pattern).

  Then, the servo read head (servo signal reproducing magnetic head; for example, the servo signal reproducing magnetic head element 1S in FIG. 5) reproduces each burst signal so as to straddle the two burst signals (A, B) (FIG. 6). (B) shows the transition of the reproduction signal level of the servo read head).

  At this time, the difference (A−B) between the reproduction signal level of the burst A and the reproduction signal level of the burst B is compared (takes a deviation), and the difference becomes 0 ((1), (3), (5) is the track center. In other words, the head actuator applies servo so that the difference (A−B) is always zero, and feedback control is performed so as not to off-track. This series of operations is also called track following.

  The bursts A and B may be formed by writing a signal in the non-signal portion or conversely forming a tone signal that is uniformly written in the servo band.

  In general, the width (Width-R) of a servo read head for linear tape that does not perform azimuth (diagonal) recording is designed to be slightly narrower than the widths (Width-A, B) of bursts A and B. If Width-R becomes larger than Width-A, B due to manufacturing variation, etc., two adjacent bursts A (or burst B) are read at the same time, and the output difference comparison is performed normally. This is because things cannot be done.

  On the contrary, when Width-R is narrower than Width-A and B, a dead zone is generated as a position detection signal as shown in the ranges of (2) and (4) in the figure.

  That is, in the amplitude comparison using simple two bursts, the range in which the gain linearity is just balanced is good, but there is a disadvantage that it is greatly shifted in either direction and becomes worse in the range where the burst signal on one side is minimized. This occurs because the read width is designed to be slightly smaller than the burst write width in order to avoid crosstalk between adjacent bursts.

  For this reason, when entering the dead zone, it is necessary to forcibly move in either direction so as to return to the range shown in (1) or (3). It is good that there is as little dead zone as possible in these illustrations (2) and (4), but if not, the vicinity of the apex of the triangle will be the boundary between illustrations (1) and (3). This is a difficult range for the servo, and the same control is required.

  Now, in the servo read head 1S and servo pattern shown in FIG. 6, when considering a next-generation machine with a narrower track pitch, the widths Width-A and B of bursts A and B are narrowed, and the servo read head is similarly configured. The width Width-R of 1S needs to be reduced.

  And as the market requirement practice of data storage devices, it is necessary to have at least backward compatibility with the previous generation, so when considering this backward compatibility, the amplitude reference servo pattern (Amplitude Based Servo Pattern) requires the track pitch to be reduced to 1/2, 1/4 and a multiple of two.

  In that case, the servo track writer of the servo pattern writing device needs to write Width-A, B more narrowly and accurately, and there is the influence of side fringing (Side Fringing). It becomes difficult to improve the accuracy of the servo track writer head.

  Further, even if a servo track writer head with improved accuracy is manufactured, the cost becomes considerably high, which causes a significant pressure on the media manufacturing cost.

  The corresponding Width-R must also be narrowed, and the reproduction output also decreases from the narrowing, and the S / N ratio of the signal reproduction output that can be said to be the resolution of servo control (S / N ratio when comparing the amplitude) Will go down. These were the problems of amplitude based servo (Amplitude Based Servo) when further increasing the TPI (track pitch / inch).

  On the other hand, the timing-based servo pattern (Timing Based Servo Pattern) represented by LTO selects an arbitrary track pitch such as 1.3 times while using the same servo pattern without increasing the track pitch suddenly. The ability to do so is a great advantage, but the timing reference servo system is also limited by the fourth generation level of LTO scheduled by IBM because of time resolution limitations.

  The present invention has been made in view of the above points, and an object of the present invention is to obtain a sufficient S / N ratio with respect to a narrow track pitch to improve servo control performance and to deal with a plurality of generations of linear tape having different track pitches. An object of the present invention is to provide a linear tape drive device that ensures compatibility.

  In order to solve the above problems, a linear tape drive device according to the present invention comprises a servo band having a plurality of servo tracks along the longitudinal direction of the magnetic tape and a data band having a plurality of recording tracks along the longitudinal direction of the magnetic tape. In the linear tape drive apparatus using linear tapes alternately formed in the tape width direction, the plurality of servo tracks include a first servo track and a second servo track having a predetermined width in the tape width direction as a track width. Are alternately arranged and reproduced across the first and second servo signals intermittently recorded in the longitudinal direction of the tape of the first and second servo tracks, and the difference between the reproduced signals. A linear tape drive device that performs tracking servo control based on the first servo track in the width direction intermediate position. And a first servo head disposed so as to face the boundary line between the first servo track and the second servo track, and shifted by a distance of a fraction of a track width in the tape width direction from the first servo head. One or a plurality of second servo heads are provided.

  In the first servo head, the intermediate positions in the width direction are opposed to the boundary lines of the first servo track and the second servo track on the upper and lower servo bands, respectively, across a predetermined data band. The second servo head is arranged so as to be shifted from the first servo head to the data band side sandwiched between the upper and lower servo bands. .

  That is, for example, the second servo head is arranged so as to be shifted from the first servo head to the second servo track side in the upper servo band sandwiching the data band, and the lower servo band sandwiching the data band. In FIG. 2, the first servo head is disposed so as to be shifted to the first servo track side.

  In the linear tape drive device of the present invention, tracking control is performed by switching to the servo head on the side where the linearity of the difference signal between the first and second servo signals is good among the first and second servo heads. It is characterized by performing.

More specific features of the linear tape drive device of the present invention are as follows:
(1) A structure having a plurality of servo heads separated by a predetermined distance of about a fraction of the track pitch on the servo head side without changing the servo pattern written on the medium.
(2) A structure having a plurality of servo heads per servo band is provided.
(3) Even if the track pitch is narrowed, the servo pattern and the read width of the servo read head do not have to be narrowed, thereby enabling high-precision servo control without lowering the S / N of the servo signal. .
(4) Either a servo head that uses only one servo band (one servo head) or a structure that can use either two servo bands (two servo heads) is used.
(5) In the case where two servo bands are used, the structure is such that the same function as that provided for a plurality of servo heads on one side is obtained by shifting the position of the servo head on the opposite side.
(6) By switching and using the multi-servo head on one side, the configuration can cope with the signal lines corresponding to the increase in the servo channel.
(7) Only the portion with good linearity of the difference amount of the output comparison that becomes the servo control signal is used by switching with the multi-servo head.

(1) According to the first to fourth aspects of the present invention, even if the track pitch of the linear tape to be used is changed (for example, narrowed), the servo that records intermittently on the first and second servo tracks. It is not necessary to change the reproduction width of the signal pattern and servo signal reproduction magnetic head.

  That is, since the intermediate position in the width direction of the first servo head is arranged so as to coincide with the boundary line between the first and second servo tracks having a predetermined track width (the linear tape of the generation having the predetermined track pitch). Tracking control is performed based on the difference between the signals reproduced by the first servo head. Since the second servo head is arranged at a distance of a fraction of a positive number of the track width, for example 1/2, in the tape width direction from the first servo head, the servo track of the second servo head is changed by generational change, for example. When the track pitch is reduced to, for example, 1/2, the intermediate position in the width direction of the first servo head matches the boundary line of the first and second servo tracks, and the intermediate position in the width direction of the second servo head. The position of the first and second servo tracks is opposite to the center of the track that is shifted from the first servo head.

  Therefore, tracking control can be performed based on the difference between the reproduction signals of the first servo head and the reproduction signal of the second servo head without changing the servo signal pattern and the reproduction width of the servo head. . As a result, sufficient track following performance and compatibility with a plurality of generations of magnetic tapes having different track pitches can be ensured.

That is,
(1-1) In order to avoid reducing the reproducing width of the magnetic head for servo reproduction, it is necessary to ensure a sufficient S / N ratio when comparing the amplitude of servo signals of an amplitude reference (amplitude base) servo system. It is possible to improve servo control performance.

  (1-2) The backward compatibility of the second generation and the third generation can be secured with the original servo pattern.

  (1-3) Since several generations are possible with the original servo pattern as described above, the investment of the servo pattern writing device can be drastically reduced.

  (1-4) Since it is not necessary to make the track pitch of the servo track writer head of the servo pattern writing device narrower than the original, the cost of the servo track writer head can be reduced. In addition, since it can be used for several generations for a long time, the design and development costs can be fully recovered.

  (1-5) The running cost for periodic replacement of the servo track writer head can be reduced.

(1-6) By setting the arrangement distance (deviation distance) between the first servo head and the second servo head to an arbitrary distance that is a fraction of the track width, Since it is not necessary to double the density in terms of inches, the design flexibility of the entire format is increased.
(2) According to the invention described in claim 2, it is not necessary to increase the number of second servo heads in the lower servo band while sandwiching the data band, and the number of servo reproducing heads as a whole Can be suppressed.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings, but the present invention is not limited to the following embodiments. In the present embodiment example, while using a checkered amplitude based servo pattern (Amplitude Based Pattern), even if the track pitch becomes 1/2, for example, the servo pattern is not changed and the 1 / of the distance of the original track pitch is changed. By having the servo playback head shifted by 2 pitches, the head width (Width-R) is not narrowed, ensuring a sufficient S / N ratio for narrow track pitch and improving servo control performance. did.

  FIG. 1 shows the principle. FIG. 1 shows a part of a plurality of servo tracks formed in one servo band as in FIG. 6, for example, a first servo track and a second servo having a track width (track pitch) of 10 microns. A plurality of tracks are alternately formed in the tape width direction.

  A burst signal of burst A is intermittently formed in the tape longitudinal direction of the first servo track, and burst B is intermittently formed in the tape longitudinal direction of the second servo track adjacent to the first servo track. Burst signals are formed (in FIG. 1 (a), only one burst A and one burst B are shown, but each of these bursts A and B is intermittently provided in the longitudinal direction of the tape). Are formed to form a servo pattern).

  In one servo band shown in FIG. 1A, two servo read heads S1 and S2 are arranged with a 1/2 pitch shift from the original track pitch. That is, S1 is a servo read head (first servo head) disposed so that the intermediate position in the width direction faces the boundary between the first servo track and the second servo track, and S2 is the servo read head. This is a servo read head (second servo head) disposed with a 1/2 pitch shift from the head S1 in the tape width direction.

The interval between the servo read heads S1 and S2 in the tape longitudinal direction is set in a range in which the reproduction signals of both heads do not interfere with each other.
Signals reproduced from the bursts A and B by the servo read heads S1 and S2 are as shown in FIG. The reproduction signal of the head S2, which is arranged with a 1/2 track pitch shifted from the head S1 in the tape width direction, is reproduced as shown in FIG. 1B when the tape fluctuates in the width direction. Represents that.

 In the servo read head S1, the portion (1) shown in the figure (in the case of bursts A and B), which is the original track pitch center, comes to the portion with good linearity of the differential signal (AB), and the servo is applied without any problem. It is possible.

  Next, the middle of the burst B is the track center at the double density, but this portion is in a range including a dead zone in the servo read head S1 and cannot be used. However, the servo read head S2 shown in FIG. 8 is a portion with good linearity, and if this signal is used, the servo can be applied without any problem.

  Similarly, while switching the servo read head to be used alternately with (3) of the servo read head S1, (10) of the servo read head S2, and (5) of the servo read head S1, only the portion with good linearity is used. Servo can be applied with high accuracy.

  FIG. 2 shows three servo read heads for one servo band, which are shifted by 1/3 pitch. That is, the servo read head S1 disposed so that the intermediate position in the width direction faces the boundary line between the first servo track and the second servo track is shifted by 1/3 pitch on one side, for example, the upper side in the tape width direction. Servo read head S2a (second servo head) is disposed, and servo read head S2b (second servo head) is disposed with a shift of 1/3 pitch on the other side in the tape width direction, for example, the lower side. .

The intervals in the tape longitudinal direction of the servo read heads S1, S2a, S2b are set in a range in which the reproduction signals of these heads do not interfere with each other.
Signals reproduced by these servo read heads S1, S2a and S2b from bursts A and B are as shown in FIG. Incidentally, the reproduction signals of the heads S2a and S2b, which are arranged with a shift of 1/3 track pitch in the tape width direction from the head S1, are reproduced as shown in FIG. 2B when the tape fluctuates in the width direction. Represents that
In the servo read head S1, the portion (1) shown in the figure (in the case of bursts A and B), which is the original track pitch center, comes to the portion with good linearity of the differential signal (AB), and the servo is applied without any problem. It is possible.

  Next, the position of 1/3 in the tape width direction of burst B is the track center, but this portion is in a range including dead zones ((2) and (7) in the figure) in servo read heads S1 and S2a. I can not use it. However, the servo read head S2b shown in FIG. 11 has a good linearity, and if this signal is used, the servo can be applied without any problem.

  Similarly, (8) of the servo read head S2a, (3) of the servo read head S1, (13) of the servo read head S2b, (10) of the servo read head S2a, (5) of the servo read head S1 in order. While switching the servo read head to be used, it is possible to apply the servo with high accuracy using only the portion with good linearity.

  As a result, 1.33 times TPI can be realized without changing the servo pattern and servo signal S / N without having to increase the TPI (track pitch / inch) twice as shown in Fig. 1. It becomes. This is a great advantage from the viewpoint of increasing the degree of freedom of TPI migration, and greatly contributes to making the format migration realistic up to the fourth generation.

  Next, although only one servo band has been described in FIGS. 1 and 2, the servo heads are actually arranged so as to sandwich the data head group from both sides. And the servo is applied aiming at the middle of the difference signal of both servo heads on both sides. This is because, as described above, the tape has temperature and humidity change characteristics and expands and contracts, so that the influence is halved by taking the middle of the two servo heads on both sides.

  The description of FIG. 1, FIG. 2, and FIG. 6 is basically the case where the same servo read head arrangement is present in both servo bands sandwiching the data band. This is to reduce the influence of the. However, the change speed of expansion and contraction in the width direction of the tape is a unit of several tens of minutes to several hours, and it is unlikely that it will change greatly in several minutes. Then, two servo read heads read from the servo patterns of the two servo bands at the same time, and it is not necessary to perform correction at all times. If correction is made once every few minutes, it is sufficiently practical. Control is possible. FIG. 3 shows an embodiment invented based on this idea.

  In FIG. 3, servo read heads S1a and S2b are arranged on the servo band #n side, and servo read heads S1b and S2a are arranged on the servo band # n + 1 (or n-1). That is, in the servo read head S1a (first servo head), the intermediate position in the width direction is opposed to the boundary line between the first and second servo tracks of the upper servo band of two servo bands sandwiching the predetermined data band. The servo read head S1b (first servo head) is located at the intermediate position in the width direction, and the first and second servos of the lower servo band of the two servo bands sandwiching the predetermined data band. It is arranged so as to face the boundary line of the track.

  The servo read head S2b (second servo head) is shifted from the servo head S1a of the upper servo band to the 1/3 pitch, burst B side, and the servo read head S2a (second servo head) is arranged. ) Is shifted from the servo head S1b of the lower servo band to the burst A side by 1/3 pitch.

  The interval between the servo read heads S1a and S2b and the interval between the servo heads S2a and S1b are set in a range in which the reproduction signals of the heads do not interfere with each other.

  The signals reproduced from the bursts A and B by the servo read heads S1a, S1b, S2a and S2b are as shown in FIG. 3B, which are the servo read heads S1, S2a and S2b shown in FIG. Similar to the reproduction signal.

  For this reason, the servo read heads S1, S2a, S2b of FIG. 2 are arranged in two lower servo bands with a data band interposed therebetween, and a total of six servo heads (servo read heads S1, S2a, S2b) are used. It can be seen that the same servo control can be performed in the case of performing.

  The point in FIG. 3 is that the servo read heads S1a and S1b are in the same positional relationship between the upper and lower servo bands. While the correction can be performed and the servo read heads S2a and S2b are used, the position control is performed by the servo signal only on one side, but the offset amount at the time of the servo read heads S1a and S1b performed most recently Can be used to perform large (and dominant) tape width expansion / contraction correction. The number of servo read heads can be reduced from six to four, which is advantageous in terms of cost and reliability. If this theory is applied, even in the case of a quarter pitch, it is possible to carry out in the same manner as described above without extremely increasing the number of servo read heads.

  The servo read heads S1, S2, S1a, S1b, S2a, and S2b can be arranged, for example, in the magnetic head stack portion of FIG. 5, or may be arranged in other magnetic head portions. .

1A and 1B are diagrams illustrating an embodiment of the present invention, in which FIG. 1A is a schematic diagram illustrating a positional relationship between a servo head and a servo pattern according to the present invention, and FIG. 4A and 4B show another embodiment of the present invention, in which FIG. 4A is a schematic diagram showing a positional relationship between a servo head and a servo pattern of the present invention, and FIG. 4A and 4B show another embodiment of the present invention, in which FIG. 4A is a schematic diagram showing a positional relationship between a servo head and a servo pattern of the present invention, and FIG. Schematic diagram of the servo band method generally used in the linear tape format. The principal part front view which shows an example of the magnetic head part used with a linear tape drive apparatus. An example of a conventional amplitude reference servo system is shown, (a) is a schematic diagram showing a positional relationship between a servo head and a servo pattern, and (b) is an explanatory diagram showing a reproduction signal of the servo head.

Explanation of symbols

  A, B ... burst signal, DB ... data band, SB ... servo band, S1, S2, S1a, S1b, S2a, S2b ... servo read head, T ... magnetic tape.

Claims (4)

Linear tape drive using linear tape in which a servo band having a plurality of servo tracks along the longitudinal direction of the magnetic tape and a data band having a plurality of recording tracks along the longitudinal direction of the magnetic tape are alternately formed in the tape width direction In the device
The plurality of servo tracks are formed by alternately arranging first servo tracks and second servo tracks having a predetermined width in the tape width direction as track widths. A linear tape drive device that reproduces the first and second servo signals recorded intermittently in the longitudinal direction of the tape and performs tracking servo control based on the difference between the reproduced signals,
A first servo head disposed so that an intermediate position in the width direction faces a boundary line between the first servo track and the second servo track;
A linear tape drive apparatus comprising: one or a plurality of second servo heads arranged at a distance of a positive fraction of a track width in the tape width direction from the first servo head. . In the first servo head, an intermediate position in the width direction is opposed to a boundary line between the first servo track and the second servo track in each of the upper and lower servo bands across a predetermined data band. Arranged so that
2. The linear servo according to claim 1, wherein the second servo head is disposed so as to be shifted from the first servo head toward a data band sandwiched between upper and lower servo bands. Tape drive device.   2. The tracking control is performed by switching to a servo head having a good linearity of a difference signal between the first and second servo signals among the first and second servo heads. A linear tape drive device according to 1.   3. The tracking control is performed by switching to a servo head having a good linearity of a difference signal between the first and second servo signals among the first and second servo heads. A linear tape drive device according to 1.