JPH03203071A - Servo signal writing method in magnetic disk device and servo disk medium - Google Patents

Abstract

PURPOSE:To realize high recording density, and to prevent the occurrence of an error at the time of recording and reproducing by writing a signal as changing a track pitch continuously so that the track pitch becomes narrow at the inner side of a disk medium and becomes wide at the outer side of it. CONSTITUTION:In the case a positioning servo signal is written in the servo surface 1s of a magnetic disk 1 by a servo head hs, a carriage 7 is moved by controlling a drive circuit 9 by a head carriage positioning servo circuit 8. Simultaneously with this, the movement of the carriage 7 is measured by a laser length measurement circuit 10, and when the movement reaches the prescribed movement, the servo signal is written. A track pitch linear correction circuit 13 is installed between a track counter 12 and the carriage positioning servo circuit 8, and corrects the track pitch so that it becomes larger as the track comes nearer to the outer side. As the result, TPI margins between the data surface and the outer side and between the data surface and the inner side can be made constant.

Description

[Detailed Description of the Invention] [Summary] Regarding the method of writing servo signals on the servo surface, which serves as a reference for positioning the data head, and the servo disk medium, a method is provided to make the TPT margin the same on both the inner side and the outer side of the magnetic disk. The purpose of this is to narrow the track pitch and prevent errors from occurring during recording/playback. The magnetic disk is configured to write by continuously changing the track pitch so that the pitch becomes narrower on the inner side of the magnetic disk and wider on the outer side.

[Industrial Application Field] When recording/reproducing information on the data surface with a data head in a magnetic disk device, in order to seek and position the data head to the target cylinder, a servo signal is read from the servo surface and the cylinder A track-following method is used to detect the position. The present invention relates to a method for writing a servo signal on a servo surface that serves as a reference for positioning a data head, and to a servo disk medium.

[Conventional technology]

In order to increase the recording density in a magnetic disk device, it is required to narrow the track pitch, but the track pitch on the outer side of the magnetic disk is limited, and as a result, it is difficult to narrow the track pitch.

FIG. 5 is a plan view showing a magnetic disk surface on which head positioning is performed using a conventional servo surface and information is recorded. Reference numeral 1 denotes a magnetic disk, and data is written on the data surface 2 at a constant track pitch from the inner side i to the outer side 0.

3.4 is a waveform showing the output level when pre-written information is read, 3 is the output waveform on the inner side, and 4 is the output waveform on the outer side.

To measure this output level, DC erase the entire area around the trunk to be measured on the magnetic disk, write data to the on-track position, and then move the read head in a direction across the track to be measured. This is done by reading out the output level while FIG. 6 shows the results. On the outer side, as shown by the solid line, the output level is high and the spread in the direction across the track is also large. On the other hand, on the inner side, as shown by the broken line, the output level is low and the spread in the direction across the track is also narrow.

The reason why the outer tracks have a higher output level and a wider spread is due to the fact that the peripheral speed of the outer magnetic disk is faster.

(Problem B to be solved by the invention) The inner track and the outer trunk of a magnetic disk have different lengths of one circumference, which are trajectories on the disk, but the maximum frequency of written data is The same is true. Therefore, since the outer output level is higher and the spread is wider, the BPI (maximum information recording density per inch on the circumference) is inversely proportional to the radius of the disk.

When the BPI changes in this way, the margin against track deviation, that is, the TPI margin also changes.

FIG. 7 is a diagram showing a method for measuring the TPI margin.

First, tracks N and N-1 to be measured on the magnetic disk
, N+1 are all DC erased.

Next, as shown in (1), data is recorded on N tracks, and then noise data is recorded on N-1) racks as shown in (2). Next, as in (3), the data on the N trunk is played back to check for errors. Assuming that no error has occurred as a result, the N-1 track is slightly off-trunked toward the N track as shown in (4), and then noise data is recorded.

Then, in the same way as in the above case, in step (5), the data of N tracks is reproduced to check whether there are any errors.

Assuming that no error occurred at this time, (6
In step (7), the N-1 track is further slightly off-track and noise data is recorded, and in step (7), the data of the N track is reproduced to check for errors.

As a result of repeating such work, if an error occurs during data reproduction on the N track after the third off-track as shown in (9), the limit of the TPI margin is the second off-track. up to the amount.

Such TPI margin measurement is also performed between the N+1 track and the N track.

In this way, when measuring the limit that allows accurate recording/reproduction even when adjacent tracks gradually approach each other, that is, the TPI margin, the TPI margin becomes narrower in the outer track where the write spread is larger, as described above.

That is, since the trunk spacing is constant on all surfaces of the magnetic disk, on the outer side where the output level spreads widely, interference is likely to occur between adjacent tracks, so the margin against track misalignment becomes narrower. On the inner side, on the other hand, the spread of the output level is narrow and interference with adjacent trunks is less likely, so the TPI margin can be increased accordingly.

Incidentally, as the recording density of magnetic disk devices increases, the number of tracks increases, but this results in a decrease in the track pitch, and the margin for positioning accuracy and track misalignment due to thermal off trunks also decreases. This is a bottleneck in improving performance.

However, as mentioned above, since the TPI margin is narrow on the outer side of the magnetic disk, it is necessary to set the full track pitch to the same pitch as the outer side track, and as a result, the inner track has a narrow TPI margin. !
There is too much room in the margin, which goes against the goal of increasing recording density.

The technical problem of the present invention is to focus on the fact that the track pitch cannot be narrowed because the TPI margins are different, and to make the TPI margins the same on both the inner and outer sides of the magnetic disk. The object of the present invention is to make it possible to narrow the track pitch and prevent errors from occurring during recording/reproduction.

[Means to solve the problem]

FIG. 1 is a diagram explaining the servo signal writing method in a magnetic disk device and the basic principle of a servo disk medium according to the present invention. In the figure, the horizontal axis is the track direction on the servo surface, the left end i is the inner side, and the right end 0
is on the outer side.

The vertical axis is the track pitch. In this figure, a solid line 5 is the track pitch written on the servo surface according to the present invention, and the track pitch of the outermost track 0 is po, and the track pitch of the innermost track i is pn. Then, pn<p(1).In other words, as is clear from the solid line 5, according to the present invention, when writing the positioning servo signal on the servo surface with the servo head, the track pitch is It becomes narrower on the side and wider on the outer side.
Moreover, the track pitch is changed linearly for writing.

[Function] The broken line 6 indicates the track pitch when a servo signal for positioning is written on the servo surface using the conventional method, and the track pitch is the same on both the inner and outer sides of the servo surface.

In contrast, in the servo disk medium of the present invention, the track pitch on the inner side is narrow, and the track pitch on the outer side is wide. The track pitch changes continuously between the inner side and the outer side.

In this way, the track pitch is narrowed on the inner side,
By making the outer side wider, the TPI margin will be equal across the entire trunk.

When servo signals are written at a constant track pitch as in the conventional method, the TPI margin is narrow on the outer side, as described above. For example, as shown in Fig. 2(a), assuming that the TPI margin of the outer track is ±4 μm and that of the inner track is ±8 μm, then T
1 to make the PI margin uniform across all trunks
, as shown by the solid line 5, the track pitch on the outer side may be widened by 2 μm, and the track pitch on the inner side may be narrowed by 2 μm. As a result, as shown in FIG. 2(b), the TPI margin of the outer track becomes ±6 μm, which is 2 μm more than before. In addition, the TPI margin of the inner track has been reduced by 2 μm compared to the conventional one, and is ±6
It becomes μm. In the end, the TPI margin is constant over all tracks from the inner side to the outer side, and the outer side, where the TPI margin was the narrowest, has a margin of 2 μm compared to the conventional one. Therefore, assuming that the TPI margin on the outer side is 4 .mu.m as before, the trunk pinch can be reduced by 2 .mu.m, and the recording density can be significantly improved. Therefore, since the TPI margin is constant at ±4 μm over all trunks, there is no risk of causing errors during recording/reproduction.

〔Example〕

Next, examples will be used to explain how the servo signal writing method and servo disk medium in a magnetic disk device according to the present invention are actually implemented. FIG. 3 is a block diagram illustrating a servo trunk writer for writing servo signals to a servo surface in the method of the present invention. 1 is a magnetic disk, and one surface 1s is a servo surface. h... is a data head, and hs is a servo head. To record/reproduce data on the data surface or write servo signals on the servo surface, each head is simultaneously sought in the radial direction of the magnetic disk 1 by the carriage 7.

When writing a servo signal, the carriage positioning servo circuit 8 controls the carriage drive circuit 9 to move the carriage 7.

At the same time, the laser length measuring circuit 10 measures the amount of movement of the carriage 7, and when a predetermined amount of movement is reached, a servo signal is written.

To move the carriage 7 from the outer side to the inner side or vice versa, the track counter 12 controlled by the CPU 11 counts the number of tracks and moves the carriage 7 by a predetermined amount. A control signal is sent to the positioning servo circuit 8. At this time, in the present invention, a track pitch linear correction circuit 13 is provided between the track counter 12 and the carriage positioning servo circuit 8 to correct the track pitch according to the track position. That is,
As explained in FIGS. 1 and 2, correction is performed so that the track pitch of the outer track gradually increases. As a result, in a magnetic disk device in which a servo signal is written on the servo surface Is using this device, the TPI margin between the outer side and the inner side of the data surface is constant.

FIG. 4 is a diagram showing a data surface on which a data head is positioned using a servo surface on which a servo signal is written with the track pitch corrected in this manner, and data is written thereon.

The track pitch is narrow on the inner side (left side) and wide on the outer side (right side). That is,
pn<pn-,<...<pt<Pl<po
It becomes. On the other hand, when the output level is measured as explained in Fig. 7, the height and spread of the output level are small in the inner track, while the height and spread of the output level are small in the outer track. big. In this way, the track pitch is large in a track with a large spread of output levels, and the track pitch is narrow in a trunk with a narrow spread, so the TPI margin is constant over all tracks.

In this embodiment, the case where the track pitch is corrected linearly has been described, but it may be curved.

〔Effect of the invention〕

As described above, according to the present invention, when writing a servo signal on the servo surface, by adding a function to the servo track writer to continuously change the track pitch, the outer track width can be increased. I have to. Therefore, when recording/reproducing data, the track pitch becomes larger on the outer side of the data surface, and as a result, the TPI margin becomes constant across all tracks, making it possible to narrow the overall track pitch and achieve higher recording density. Moreover, there is no risk of causing errors during recording/reproduction. Furthermore, since it is sufficient to add a function to continuously change the track pitch to the servo track writer, it can be realized easily and inexpensively.

[Brief explanation of drawings]

FIG. 1 is a diagram explaining the servo signal writing method in a magnetic disk device according to the present invention and the basic principle of the servo disk medium. FIG. 2 is a diagram comparing the TPI margin between the conventional method and the method of the present invention. 4 is a block diagram showing an embodiment of an apparatus for writing servo signals using the method of the present invention; FIG. FIG. 5 is a diagram showing the reproduction output level on the conventional data side, FIG. 6 is a diagram showing the reproduction output level, and FIG. 7 is a diagram showing a method for measuring the TPI margin. In the figure, 1 is the magnetic disk, IS is the servo surface, 2 is the data surface, i is the inner side of the disk, O is the outer side of the disk, 3 is the playback output level of the inner track, and 4 is the playback output of the outer track. Level 5 indicates the track pitch according to the present invention, and 6 indicates the conventional track pitch.

Claims (1)

[Claims] 1. When a servo head writes a positioning servo signal to the servo surface of a magnetic disk device, the track pitch is continuously narrowed on the inner side of the magnetic disk and widened on the outer side. A servo signal writing method in a magnetic disk device characterized by writing by changing the track pitch. 2. A servo disk medium installed in a magnetic disk device, in which writing is performed by continuously changing the track pitch so that the track pitch becomes narrower on the inner side of the disk medium and wider on the outer side of the disk medium. A servo disk medium in a magnetic disk device characterized by: