JPH10269713A - Magnetic disk medium and magnetic disk device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To satisfactorily reproduce an identifier signal to perform the recording/reproducing operation even when off-track of a reproducing head to the identifier signal during intrinsic offset adjustment of an MR head by recording an error correctable error correction code to an identifier area of the servo information to be recorded to a magnetic disk for burying servo. SOLUTION: A track code 34 and error correction codes ECCA35, ECCB36 are recorded to a servo area identifier of a magnetic disk medium. The error correcting code area 35 of odd number tracks is recorded in the doubled track width in the same phase as the odd number tracks, while the error correcting code area 36 of even number tracks is recorded in the doubled track width in the same phase as the even number tracks. Thereby, the track position can be recognized satisfactorily even when the intrinsic offset adjustment of the MR head is performed, making it possible to attain a highly reliable hard disk apparatus.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic disk, and more particularly to a disk medium on which a servo pattern of an embedded servo system of a hard disk is recorded, and an apparatus for recording and reproducing data on and from the disk medium.

[0002]

2. Description of the Related Art In recent years, the use of MR heads has significantly increased the recording density of hard disk drives.

An example of the above-described conventional hard disk device will be described below with reference to the drawings.

FIG. 5 shows a configuration of a conventional hard disk drive. In FIG. 5, reference numeral 1 denotes a magnetic disk medium. Reference numeral 2 denotes a data area for recording and reproducing user data. 3 is a servo area and 4 is a sector. Reference numeral 5 denotes an actuator, and reference numeral 6 denotes a head member for recording and reproducing data.

The operation of the hard disk device configured as described above will be described below.

First, the magnetic disk medium 1 is rotating at a constant rotational speed in the counterclockwise direction as shown in the figure. The magnetic disk medium 1 is divided into a servo area 3 in which servo information for positioning the head member 6 is recorded and a data area 2 in which data is recorded and reproduced. The servo information recorded on the magnetic disk medium 1 is reproduced as a sample by the head member 6 with the rotation of the disk medium 1, and a control current is supplied to the actuator 5 by performing a control operation and positioning using the reproduced signal. The head member 6 is positioned on a track (not shown). Actuator 5
As shown in the figure, a swing arm system that moves in a radial direction in a rotational manner is generally used. Since the signal recorded in the servo area 3 is recorded in an in-line system in which bits are aligned in the radial direction, the signal follows a locus in the radial direction of the actuator as shown in the figure.

FIG. 6 is an explanatory diagram of servo information included in the servo area 3. The preamble 31, the sync 32, the identifier 3
3, a burst 37 area. Since the preamble 31 has a different recording frequency between the data area 2 and the servo area 3, the filter setting value for reducing high-frequency noise is switched in order to ensure data reproduction quality, and the amplitude is kept constant with respect to fluctuations in the reproduction amplitude. It is provided for the processing time in the AGC circuit. The sink 32 is an area provided for recognizing the starting point of the servo signal, and aims to generate the demodulation timing of the identifier 33 and the burst 37 following the area.

The identifier 33 is provided for recognizing a so-called physical position, and includes a code for recognizing a track, an index signal indicating a starting point of rotation, a sector code indicating a rotation angle from the index, and a disk. Generally, the number of the surface is recorded. In a hard disk drive equipped with an inductive head,
In many cases, the identifier 33 is recorded with an index signal and a simple track code capable of recognizing a track in a range of several tens of tracks. At the time of actual recording / reproduction, another identifier is provided in the data area 2, and this identifier is reproduced to confirm whether or not it is a target position, and recording / reproduction is performed.

In a hard disk drive equipped with an MR head, the identifier of the data area 2 is omitted and the position is confirmed by the identifier 33 of the servo area 3 because of a head offset (described later) which is a problem unique to the MR head. The recording / reproducing operation is being performed. In such a case, if an error occurs in the identifier 33 of the servo area 3, it will be recorded in the wrong place, and the data will be destroyed. Therefore, the reliability of the reproduced data of the identifier 33 becomes important. I have. In addition, tracks on the entire disk surface must be recognizable. For a 3.5 inch hard disk,
Since there are approximately 5,000 tracks, codes of 13 bits or more are required, and the code length tends to increase as the recording density advances in the future, and the error occurrence rate also increases.

In the identifier area 33, a track may be moved or an off-track may occur. Therefore, a gray code which changes only one bit from an adjacent track is often used.

The burst 37 is an area provided for positioning the head member 6 on a track. In FIG. 6, four types of burst signals are shown, but three types of bursts may be employed. A in the area of the burst 37 is recorded on the even-numbered track at the same phase as the track in the radial direction. B is recorded on an odd track in the same phase as the track in the radial direction. C,
D is arranged at a position shifted from the phases of A and B by 90 degrees in the radial direction, with one cycle being twice the track interval.

When the head member 6 passes through the servo area 3, each signal is reproduced, and the head positioning means (not shown)
First, the track code of the identifier area 33 is confirmed, and then the track deviation information is obtained from the difference between the reproduction amplitudes of the burst signals C and D, and the head is positioned at the target track.

FIG. 7 is a structural view of the MR head. 11
Is a coil for writing, 10 is an MR element for reproduction,
A recording gap 12 for performing a recording operation generates a recording magnetic field in accordance with a current flowing through the coil 11 to record data on the magnetic disk medium 1. As shown in the figure, the MR head has a reproducing MR element and a writing inductive head arranged at positions shifted from each other in the rotational direction. The width of the recording gap 12 in the track direction is set to be slightly wider than the width of the reproducing MR element 10, so that it is difficult to reproduce a noise signal from an adjacent track even when off-tracking.

As described above, when the recording gap 12 and the MR reproducing element 10 coincide with each other in the rotational direction as shown in the figure, there is no deviation between the recording gap 12 and the MR reproducing element 10 in the track direction. As described above, the actuator 5 pivotally moves in the radial direction, so that the head member 6 and the rotation direction have a predetermined angle depending on the radius (track). This angle is determined by the distance between the rotation center of the disk medium 1 at the center of rotation of the actuator 5 and the distance from the center of rotation of the actuator 5 to the head gap, and is approximately 1
There are about 5 degrees. The distance between the MR reproducing element 10 and the recording gap 12 is about 2 (um).

FIG. 8 shows the center deviation of the recording / reproducing head. FIG. 8A is an explanatory diagram of the head position shift when the position is not corrected. Burst C in FIG.
And the burst D are reproduced by the MR reproducing element 10, and the head member 6 is positioned at a position where the difference becomes zero. Therefore, the head member 6 is positioned at a position where the boundary between the burst C and the burst D and the center of the MR reproducing element in the track direction match. At this time, the head member 6 is rotationally moved in the radial direction by the actuator 5, so that the radial center of the recording gap 12 is off-track as shown in the figure. If recording is performed in such an off-track state, the center of the data track will be shifted, so that data cannot be reproduced properly. This amount is about 0.5 (um), which is the current track interval of about 5 (u).
Even with m), the amount is not negligible, and it is an important solution for high track density in the future.

Therefore, in the conventional hard disk drive, the signal obtained by taking the difference between burst C and burst D is shown in FIG.
The head member 6 is positioned on the basis of a signal obtained by adding an offset signal corresponding to the off-track amount shown in FIG. This makes it possible to align the recording gap 12 with the track center as shown in FIG. 8B. However, even in this case, after the offset adjustment, the MR reproducing element 10 goes off-track with respect to the identifier signal as shown in the figure, so that the reliability of the identifier signal is reduced, and the recording / reproducing place cannot be confirmed. There is a problem that the reproduction operation cannot be performed. In this case, the conventional hard disk drive returns to the state of FIG. 8A, which is an offset state, and confirms the identifier.
The recording operation was performed in the state of (B). in this case,
Since the movement of the head member 6 accompanies, the access performance is greatly deteriorated.

In this description, the offset adjustment is performed during the recording operation. However, there is a case where the offset adjustment is performed during the reproducing operation and the offset adjustment is not performed during the recording operation. However, the same effect can be obtained.

FIG. 9 shows a locus of movement of the head member 6 during a seek operation (track moving operation).
At the time of track movement, the head member 6 normally passes over two tracks, so that the sample position of the signal of the identifier 33 cannot be specified and an error of one track in width occurs. In the seek control, speed control is performed by differentiating the identifier signal, so that the stability of the control system is impaired. In addition, as the track density increases and the speed of the actuator increases in the future, this problem will increase in the future because the vehicle passes over a plurality of tracks.

[0019]

However, in the above configuration, when the offset adjustment unique to the MR head is performed, the reproducing head goes off-track with respect to the identifier signal. There is a problem that the position and the sector position cannot be confirmed, and the recording / reproducing operation cannot be performed.

In addition, since the head passes over the identifier area during the seek operation, an error in the reproduced track position occurs and the seek control system becomes unstable.

The present invention has been made in view of the above-mentioned problems, and it has been found that even when the reproducing head is off-track with respect to the identifier signal when the offset adjustment unique to the MR head is performed, the identifier signal is reproduced well to perform the recording / reproducing operation. It is intended to provide a hard disk device that can be used.

It is another object of the present invention to provide a hard disk drive in which an error in a reproduced track position does not occur even when a head passes over an identifier area during a seek operation.

[0023]

In order to solve the above-mentioned problems, a hard disk drive and a magnetic disk medium according to the present invention use an error correction code capable of correcting an error in an identifier area of servo information recorded on a magnetic disk for embedded servo. Is recorded.

[0024]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of a hard disk drive and a magnetic disk medium according to the present invention will be described below with reference to the drawings.

FIG. 2 shows a servo area of the magnetic disk medium of the present invention. In FIG. 2, reference numeral 2 denotes a data area, and 3 denotes a servo area. In the servo area 3, a preamble 31, a sync 32, an identifier 33, and a burst 37 are recorded. Codes ECCA35 and ECC
B36 is recorded.

The operation of the servo area of the magnetic disk medium configured as described above will be described below with reference to FIGS.

When the head member 6 enters the servo area 3 from the data area 2, the preamble area 31 is first switched to an analog processing circuit optimized for the recording frequency of the servo area 3. Hereinafter, this operation will be specifically described.

The recording frequency is set lower in the servo area 3 than in the normal data area 2 in order to detect data more reliably. Therefore, the setting value of the low-pass filter is switched to a lower frequency than in the data area 2 in order to reduce high-frequency noise and improve reproduction quality. Next, AGC (auto gain control) is performed to keep a constant amplitude even if the reproduced signal fluctuates, and when the amplitude is stabilized, the gain of the AGC circuit is held. The area length of the preamble 31 is set for the time necessary to perform the above processing.

When the head member 6 passes through the preamble 31, the sink 32 is reproduced. The sink 32 is normally a DC
Also called an erase pattern, the servo area 3 is identified at a long recording interval that is not present in the data area, and is used as a starting point for generating a timing signal for detecting the next identifier 33 and burst 37.

In the identifier 33, a track code 34, ECCA 35 and ECCB 36 for error correction are recorded. In the track code 34, a code for identifying a data track on the entire surface of the disk is recorded.
Further, as the track code, a gray code that is different from an adjacent track by one bit is recorded. Although a reproduction synchronization signal for detecting a gray code is written in the drawing, the reproduction synchronization signal may be omitted if the gray code can be reproduced properly. Further, an index code indicating the starting point of the rotation angle or a sector code indicating the rotation angle from the starting point of the rotation angle may be recorded in the track code 34. Since the index code and the sector code are the same in the adjacent tracks in the same servo area 3, the track code is different by one bit in the adjacent track.

In the ECCA 35 and ECCB 36, codes capable of error correction are recorded. Track code 34
Since only one bit changes in the adjacent track, if the error correction capability is one bit, a code error due to the offset of the MR head can be corrected. To realize 1-bit error correction, even if a code capable of recognizing about 8000 tracks is inserted in the track code 34, the BCH
If a code is used, it can be realized with 5 bits. Also, considering the effects of noise in the playback signal and errors due to scratches on the media, it is better to have a large correction capability, but set an appropriate correction capability because the number of bits of the error correction code increases and the data storage area decreases. There is a need to. There are several types of error correction coding, but correction in units of several bits is sufficient, and can be realized by using a BCH code or a fire code which is a bit correction method.

The track code 34 differs by only one bit in the adjacent track, but the error correction code generated by the gray code differs by several bits in the adjacent track. Therefore, when the MR is offset, the error correction code itself causes an error. Error correction cannot be performed. Therefore, the error correction code is changed to the ECC of the odd track.
A35 and an ECB 36 of even-numbered tracks are recorded. Further, in each of the ECC areas 35 and 36, recording is performed with a width larger than the track width in the radial direction so that good reproduction is possible even if the MR head is offset.

Reference numeral 37 denotes a burst signal, and A is recorded on the even-numbered track in the same direction as the data track in the radial direction. B is recorded on the odd-numbered track in the same direction as the track in the radial direction. C and D are twice the track interval as 1
As the period, the phase is arranged at a position shifted from the positive and negative 90 degrees A and B in the radial direction. The head member 6 reproduces the signal of the burst 37 with the rotation of the disk, obtains the difference between the signal amplitudes of the burst C and the burst D, and is positioned at a position where the value becomes zero.

FIG. 1 illustrates an embodiment of the invention described above. FIG. 1 shows the servo area 3 shown in FIG.
The preamble area 31 and the sync area 32 are omitted. The error correction code area 35 of the odd track in FIG. 1 is recorded in the same phase as the odd track and with a double track width.

Error correction code area 36 of even track
Are recorded in the same phase as that of the even-numbered track with a double track width. By arranging the error correction code in this way, for example, when reproducing the track 1, the head member 6 is positive or negative 1
Even if an error occurs in the track code 34 even if the track code 34 is off track, the signal of the ECCA 35 can be correctly detected, so that the track code of the track 1 can be reproduced.

Consider the case where the head has passed an arbitrary position in the radial direction. Since the reproducing head width is smaller than the track width, an incorrect track code and at least one of the ECCA 35 and the ECCB 36 can be reproduced accurately. You can know the track code. At this time, to know which track the head member 9 is actually on, it is important to determine which of the error correction codes 35 and 36 is correct.

FIG. 3 shows an embodiment of a method for determining an accurate error correction code. FIG. 3 (A)
Based on the reproduced signal 41 reproduced by the head member 6, the burst A
The amplitudes of the A and B bursts are detected by the amplitude detection means 42 and the burst B amplitude detection means 43. Further, a track code is detected from the reproduced signal 41 by a track code detecting means 47, and the ECCA detecting means 45
The CCB detection means 46 detects each error correction code. A,
The respective amplitudes of the B burst are compared by the comparing means 44, and the error correction code detected by the ECC detecting means 45 and 46 is selected based on the comparison result.

In FIG. 1, when the A burst signal is larger than the B burst signal, it indicates that the MR reproducing element 10 is near the A burst, that is, it is understood that the MR reproducing element 10 is on an even track. Therefore, it can be determined that the ECCB 36, which is the error correction code of the even track, has been correctly reproduced, so that the ECCB detection means 46 may be selected. The track code detected by the track code detecting means 47 and the selected error correction code are sent to the error correcting means 49 to obtain a track code signal 50 which is a signal in which a data error has been corrected.

Further, when the MR head is offset, the track code signal 50 can be obtained more accurately by setting the amplitude corresponding to the offset amount by the offset setting means 56.

In this embodiment, the burst signals are A, B,
4 bursts of C and D have been described, but FIG.
As shown in (B), instead of the amplitude of the burst B, the amplitude setting means 51 compares the switching amplitude setting value with the comparing means 4.
If a value of 4 is input, a similar effect can be obtained.

In this embodiment, the error correction is performed. However, since the error correction code can detect an error, it is possible to confirm whether or not the reproduction data of the track code 34 has been reproduced correctly. However, since the data is recorded in a place other than the target track and the data is not erroneously destroyed, a highly reliable hard disk drive can be provided. Particularly, in a device that performs offset adjustment during reproduction without performing offset adjustment of the MR head during recording, an error correction code is used as a detection code during recording, and when used as an error correction code during reproduction, data is erroneously corrected as described above. A magnetic disk capable of high-speed reproduction can be provided without being destroyed and being able to promptly correct even if a track code error occurs during reproduction.

FIG. 4 shows an embodiment of a seek control system according to the present invention. The servo signal is applied to the servo area 3 as shown in FIG.
4 passes through the head member 6 at a prescribed cycle,
From the reproduction signal 41 shown in FIG.
1 is sampled and detected. The track code signal detecting means 51 outputs the track code signal 50 having the error corrected by the configuration shown in FIG. The subtraction means 53 obtains the speed signal 55 by taking the track code signal 50 and a signal obtained by delaying the track code signal 50 by the delay means 52. The control means 54 calculates a control amount for the actuator 5 based on the speed signal 55. The actuator 5 moves the head member 6 to a target track based on a command from the control means 54.

At the time of seek control, as described with reference to FIG. 9, the head member 6 moves over a plurality of tracks, so that it is usually possible to determine only one of the track codes. According to this, even when the head member 6 moves over two tracks,
Either of the error correction codes 35 and 36 can be reliably detected, and which is correct can be determined by the burst signal 37, so that an accurate track position can be obtained. Therefore,
The signal quality of the speed signal 55 in FIG. 4 is improved, and a stable seek can be realized. The speed is further increased, and the track code can be detected stably if the error correction capability is increased even when the track code extends over three or more tracks.

As described above, according to the present embodiment, accurate track position information can be obtained by providing an error correction code capable of error correction in the identifier area of the servo information of the magnetic disk for embedded servo. A high-speed and high-speed magnetic disk device can be provided.

In this embodiment, the magnetic disk medium 1 is a hard disk medium, but may be a flexible magnetic disk as long as the pattern recorded on the medium is the same.

[0046]

As described above, according to the present invention, the error correction code recorded in the identifier area with a width wider than the track width is provided in the servo area so that the track position can be satisfactorily adjusted even when the offset adjustment unique to the MR head is performed. Therefore, a highly reliable hard disk drive can be provided.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram of a signal recorded in an identifier area according to the present invention.

FIG. 2 is an explanatory diagram of a signal recorded in a servo area of the magnetic disk medium of the present invention.

FIG. 3 is an explanatory diagram of an error correction method according to the present invention.

FIG. 4 is an explanatory diagram of a seek control method according to the present invention.

FIG. 5 is an explanatory diagram of a conventional disk medium.

FIG. 6 is an explanatory diagram of signals in a servo area recorded on a conventional disk medium.

FIG. 7 is a structural diagram of an MR head.

FIG. 8 is a diagram showing a center shift of a recording / reproducing head.

FIG. 9 is a diagram showing a movement locus of the head member 6 during a seek operation.

[Explanation of symbols]

 6 Head member 33 Identifier 34 Track code 37 Burst 35 ECCA 36 ECCB

Claims (14)

[Claims] 1. A plurality of concentric tracks recorded on a magnetic disk medium, a sector obtained by dividing the track into W at substantially equal angles in the circumferential direction (W is an integer of 1 or more), and Embeds a servo area and a data area at a predetermined angular width in the direction, and includes at least an identifier area for identifying the track and a burst signal area for positioning a magnetic head for recording and reproducing data in the servo area. A magnetic disk for servo, wherein an error correction code capable of correcting an error is recorded in the identifier area. 2. The identifier area according to claim 1, wherein a track code recorded by a code that differs by one bit in adjacent tracks and an error correction code enabling at least one bit to be corrected are recorded. The magnetic disk medium according to the above. 3. An identifier area wherein an area for recording an error correction code for an even track and an area for recording an error correction code for an odd track are provided separately in a circumferential direction. Item 3. The magnetic disk medium according to item 1 or 2. 4. The magnetic disk medium according to claim 3, wherein the error correction code is recorded with a width larger than a track pitch in a radial direction. 5. The magnetic disk medium according to claim 3, wherein the error correction code is recorded with a width twice as large as a track pitch in a radial direction. 6. The magnetic disk medium according to claim 3, wherein the error correction code has a width twice as large as a track pitch in a radial direction and a center is recorded at a center of the track. 7. The magnetic disk medium according to claim 1, wherein the error correction code is a BCH code. 8. The magnetic disk medium according to claim 1, wherein the error correction code is a fire code. 9. A burst signal area includes an on-track mark recorded in one of an even-numbered track and an odd-numbered track in the radial direction in the same phase as a track, and an on-track mark in an area deviated in a rotational direction at a track interval. 4. The magnetic disk medium according to claim 3, further comprising: a signal area in which off-track marks having phases shifted by 90 with twice as one cycle are recorded. 10. In a burst signal area, on-track marks are arranged in an even track and an odd track in the rotational direction, respectively, in the radial direction in the same phase as the tracks, and are shifted in the rotational direction from the on-track marks. 4. The magnetic disk medium according to claim 3, wherein off-track marks having positive and negative phases shifted by two times the track interval as one cycle are arranged in the areas shifted in the rotation direction. 11. A method for demodulating an error correction code recorded on a magnetic disk medium according to claim 9, comprising: a reproduction signal detecting means for detecting an on-track reproduction amplitude; and an on-track mark reproduction signal amplitude. And a demodulating means for selecting an error correction code for even-numbered tracks and an error correction code for odd-numbered tracks and performing error correction to demodulate an identifier. 12. A method for demodulating an error correction code recorded on a magnetic disk medium according to claim 10, wherein said reproduction signal detecting means detects on-track reproduction amplitudes of even and odd tracks, and said even signal. Comparing means for comparing the amplitude of the reproduced signal of the track-on-track mark with the amplitude of the reproduced signal of the odd-track-on-track mark; An error correction method comprising demodulating means for selecting a correction code, executing error correction, and demodulating an identifier. 13. An apparatus for recording and reproducing data on and from a magnetic disk medium according to claim 1, wherein a head member integrally formed with an inductive head for recording data and an MR head for reproducing data. A swing arm actuator that rotationally moves the head member in a radial direction; a position error detection unit that reproduces a burst signal to generate a position error signal indicating a deviation between the reproduction head and a track; Control means for positioning the head member on the track by using a signal; and selectively instructing the control means on a center deviation of the write head and the reproduction head in the track direction caused by rotation of the swing arm actuator. Correction means for performing correction by reproducing the identifier area recorded on the magnetic disk medium. Identifier reproducing means, error correction demodulating means for performing error correction using an error-correctable code included in the identifier area, and error correction for performing error detection using the error-correctable code included in the identifier area. A magnetic disk drive, comprising: a detection unit; and a selection unit that selects an error correction unit when the correction unit performs the correction, and selects an error detection unit when the correction is not performed. 14. A magnetic disk drive having the error correction system according to claim 12, wherein a head member for recording / reproducing data, an actuator for moving the head member in a radial direction, and the error correction unit. Speed detecting means for obtaining the speed of the head member from a track position obtained from the identifier corrected by the correction method; andcontrol means for performing seek control of the actuator using the speed obtained by the speed detecting means. A magnetic disk device characterized by the above-mentioned.