JP2007115324A - Disk unit - Google Patents

Abstract

A disk device capable of reducing the influence of repeated fluctuations in the write width of a data track in a single write method.
A recording medium having a data track formed by being partially overwritten by adjacent inner or outer data tracks, a recording head for writing information to the recording medium, and a reproduction for reading information from the recording medium And a control device for controlling the position of the head assembly with respect to the recording medium. The control device detects repetitive fluctuations in the write width of the data track and corrects the repetitive fluctuations. The disk device determines a correction write current value and executes control of a write operation based on the correction write current value.
[Selection] Figure 1

Description

  The present invention relates to an improvement in a disk device such as a hard disk.

  In recent years, hard disks are mounted on various devices. For example, a hard disk is mounted on a portable music player, a car navigation system, and the like. Under such circumstances, as one of the technologies to increase the recording capacity of information while promoting miniaturization of the hard disk itself, for example, a part is overwritten by adjacent data tracks sequentially from the inner circumference to the outer circumference of the recording medium. However, there is a method of recording a data track like a shingled roof (hereinafter referred to as a single light method). As a result, a data track narrower than the recording width written by the actual magnetic head can be realized.

  By the way, in general, in a disk apparatus, there is a case where a head servo signal for performing head positioning control swells due to a phenomenon called repetitive run-out caused by eccentricity of the rotating shaft of the disk.

  In the single write type disk device, the repeated runout may cause repeated fluctuations in the data track writing width. FIG. 9 shows how the write width of the data track is repeatedly changed. In FIG. 9, in the head 10 that writes the data track 100a on the disk, the relative position with respect to the disk periodically changes in the radial direction of the magnetic disk as shown by the flow line 102a during the writing operation. Next, when the adjacent data track 100b is written while the head 10 partially overwrites the data track 100a, the relative position of the head 10 with respect to the disk fluctuates periodically as shown by the flow line 102b. For this reason, the track width of the data track 100a is shifted from the ideal track width indicated by the lines 104a and 104b. As a result, as shown in FIG. 9A, there is a portion where the track width of the data track 100a becomes narrow. When information is read from such a data track, there is a possibility that inconveniences such as leakage of information of an adjacent data track occur in a portion where the track width is narrow.

In contrast to the repetitive runout described above, in Patent Document 1 and Patent Document 2 described below, runout correction data is created by automatically measuring the rotation synchronization component of the runout synchronized with the rotation of the disk. A technique for correcting the position error is disclosed. Further, in Patent Document 3 below, the track and adjacent tracks are recorded with respect to the phenomenon of erasing information of the track (track squeeze) when the data of the adjacent track is recorded close to the track by repeated runout. Discloses a technique for calculating a squeeze profile based on the measurement result of the repeated runout and supplying the result to a servo control loop to correct the position error of the recording head.
Japanese Patent Laid-Open No. 11-353831 US Pat. No. 6,069,764 US Pat. No. 6,882,497

  However, since the above-mentioned conventional technique aims to correct the data track writing position so that it does not fluctuate due to repeated runouts, the single write method for forming the data track while partially overwriting the adjacent data track is adopted. Even if it is applied as it is, there is a problem that it cannot cope with the fluctuation of the write width of the data track. In addition, when obtaining correction data for repeated runouts, position information sampled by servo sectors provided at regular intervals is used, so the runout components between servo sectors are components within the frequency band of the servo control loop. There was a problem that only correction was possible.

  The present invention has been made in view of the above-described conventional problems, and its purpose is to exceed the frequency band regulated by the servo sector interval for the effect of repeated fluctuations in the write width of the data track in the single write method. It is to provide a disk device that can be reduced.

  In order to achieve the above object, the present invention is a disk device, which is a concentric or spiral data track formed by being partially overwritten by an adjacent inner or outer circumferential data track. A recording medium having a data track, a recording head that writes information to the recording medium, a head assembly that includes a reproducing head that reads information from the recording medium, and a writing operation of the head assembly to the recording medium is controlled. The control device detects a repetitive variation in the write width of the data track, determines a correction write current value for correcting the repetitive variation, and The writing operation is controlled based on a current value.

  In addition, on the data tracks sandwiched between the servo sectors on the recording medium, position error detection signals with different phases are recorded repeatedly in the track direction, shifted by the track pitch in the track width direction, and the control device Further, it is characterized in that repetitive fluctuations in the write width of the data track are detected based on the position error detection signal read by the reproducing head.

  Hereinafter, the best mode for carrying out the present invention (hereinafter referred to as an embodiment) will be described with reference to the drawings.

  FIG. 1 shows a block diagram of an embodiment of a disk device according to the present invention. In FIG. 1, the disk device is a hard disk based on, for example, an in-plane recording method, and includes a recording medium 12, a head unit 14, a head drive control unit 16, a read / write (RW) unit 18, a control unit 20, The storage unit 21 is included.

  The recording medium 12 is a disk-shaped magnetic recording medium. The recording medium 12 is rotatably supported and is fixed to the base of the casing. The recording medium 12 has data tracks formed concentrically or spirally, and includes data tracks formed by being partially overwritten by adjacent inner or outer circumferential data tracks. That is, at least a part of the data tracks is a single write type data track. Data is written in the data track in units of sectors, and the size of the data is 512 bytes.

  The head unit 14 includes at least one head assembly. As schematically shown in FIG. 2, the head assembly includes a head 10 corresponding to each recording surface of the recording medium 12 and an arm 22 that supports each head 10. The head 10 includes a recording head for writing information to the recording medium 12 and a reproducing head for reading information from the recording medium 12. The head unit 14 is supported so as to be rotatable about the rotation center of the voice coil motor.

  The head drive control unit 16 drives the voice coil motor in accordance with an instruction input from the control unit 20 and controls the position of the head 10 included in the head unit 14. The RW unit 18 performs predetermined processing such as decoding on the information read from the recording medium 12 by the reproducing head included in the head 10 and outputs the information to the control unit 20. The RW unit 18 performs a predetermined process such as encoding information to be recorded input from the control unit 20 and records the information on the recording medium 12 via the recording head included in the head 10.

  The control unit 20 is connected to a host computer or the like, and instructs the head drive control unit 16 to move the head 10 to a location where information is recorded in accordance with a reproduction request from the host side. The information output by is output to the host side. Further, in accordance with a recording request from the host side, the head drive control unit 16 is instructed to move the head 10 to a position where information is recorded, and information to be recorded is output to the RW unit 18. Further, the write width of the single write data track is also controlled. This control operation will be described later.

  The storage unit 21 is configured by a flash memory or the like, and stores a write current value and the like for writing a data track on the disk. The storage unit 21 may be formed on the disk. In this case, the write current value of the next track and the like are stored in a position where the reproducing head can read the track formed on the disk immediately before jumping to the next track. Thereby, before the track jump, the control unit 20 can acquire data necessary for writing the next track.

  The control unit 20 forms data tracks for recording information on the surface of the recording medium 12, for example, concentrically. At this time, the control unit 20 overwrites a part of the first side track which is either the inner side or the outer side of the recording medium 12 with the second side track which is the other side, and performs the single write. Do. In the following example, a case where a single write is performed by overwriting a part of the outer peripheral track as the first side with the adjacent inner peripheral track as the second side will be described as an example.

  The control unit 20 according to the present embodiment records position error detection signals each having a width of the data track in the data area of the data track group related to single writing, with portions not adjacent to each other in the radial direction. For example, in each data track, the data sector length is divided by 2N (N is 1/2 or an integer equal to or greater than 1) to obtain a recording length L, and one of the data tracks related to single writing is used as the target track. Then, a burst signal having a predetermined intensity is recorded from the head of any data sector on the track of interest for a recording length L, and the subsequent recording length L portion is repeatedly DC erased. A signal portion (position error detection signal) in which burst signal recording and DC erase are alternately performed for each recording length L in this way is recorded on the target track. That is, a position error detection signal corresponding to a C burst signal written in a so-called servo sector is repeatedly recorded on the track of interest.

  Next, with respect to the track adjacent to the track of interest, the operation of DC erasing the recording length L from the beginning of one of the data sectors and then recording a burst signal having a predetermined intensity in the subsequent recording length L is performed. Repeat. That is, a position error detection signal (corresponding to a so-called D burst signal written in a servo sector) that is 180 degrees out of phase with the position error detection signal recorded on the track of interest is repeated on a track adjacent to the track of interest. Record.

  In this manner, in the data track group related to the single write, as shown in FIG. 3, the burst signal (hatched portion) having a predetermined intensity and the DC erased portion (blank portion) are arranged in a checker pattern. The position error detection signals having different phases from each other are repeatedly recorded in the track direction, shifted by the track pitch in the track width direction. N position error signals are detected for one data sector (when N = 1/2, one position error signal is detected in two data sectors).

  Here, the recording length of the burst signal is determined in units of data sectors, but the present invention is not limited to this. For example, when two or more data sectors are arranged in the data area sandwiched between servo sectors, or when there is a split sector that straddles the servo sectors, the area between the servo sectors is The recording length of the burst signal may be determined as a unit.

  FIG. 4 shows recording patterns (b) and (e) for detecting a boundary position between a track (n) and a track (n + 1). Here, the recording pattern (b) represents the burst signal shown in FIG. 3, and the recording pattern (e) represents the DC erased portion shown in FIG. A number j in the figure indicates a pair of recording patterns (b) and (e) for detecting a position error of a certain data sector, and takes a value from 0 to N. A conceptual diagram of a signal waveform when the recording pattern is reproduced by the reproducing head is shown below. When the reproducing head passes the track boundary, the amplitude Cj of the C burst signal is equal to the amplitude Dj of the D burst signal (middle stage), and Cj> Dj (upper stage) when shifted to the outer circumferential side, and Cj <Dj when shifted to the inner circumferential side. Therefore, Cj−Dj is a position error signal that zero-crosses at the track boundary.

  In the above description, an example in which the position error detection signal is recorded over the width of the track has been described. However, two types of position error detection signals whose phases are shifted by 180 degrees are generated in the radial direction of the recording medium 1. As long as the track pitch is shifted, recording may be performed across two adjacent tracks. That is, it may correspond to an A burst signal and a B burst signal written in a so-called servo sector (see FIG. 5).

  The control unit 20 can measure the boundary of the data track related to the single write by tracking the point where Cj−Dj = 0. By this boundary measurement, in the present embodiment, it is possible to measure the repetitive variation in the write width of the data track related to the single write.

  FIG. 6 shows a flow of a procedure for measuring repetitive variation in the write width of the data track. In FIG. 6, first, m = 1 is set (S1). Here, m is a natural number.

  Next, the two data tracks are single-written. That is, the control unit 20 instructs the head drive control unit 16 and the RW unit 18 to form a track on the outermost peripheral side of the disk, and overwrites a part thereof with the inner track (S2). In this case, the position error detection signal shown in FIG. 3 is recorded in the entire area of the data sector.

  Next, the control unit 20 receives a signal when the position error detection signal is reproduced by the reproducing head from the RW unit 18, tracks the point where Cj−Dj = 0 from the amplitude, and measures the track boundary. (S3). Although not explicitly shown in the measurement flow, this measurement includes an averaging process that removes track boundary fluctuations that are not based on repeated runouts during playback. The number of repetitions is set to about 100, for example.

  The above steps S2 and S3 are repeated until the predetermined number M is reached. For example, the value of M is set to about 100 (S4). After that, the measured track boundary data is averaged (S5). By averaging the track boundary data, it is possible to remove the fluctuation in the write width of the data track that is not based on the repetitive runout, and to obtain the repetitive fluctuation in the write width of the track due to the repetitive runout. However, the repetitive fluctuation of the write width of the data track obtained by the above method includes a fluctuation at the time of recording the track and a fluctuation at the time of reproduction.

  By sequentially executing the steps S1 to S5 described above from the outermost circumference side to the inner circumference side of the disk, it is possible to obtain repeated fluctuations in the write width of all tracks on the disk. Note that the measurement may be performed from the innermost side to the outer side of the disk.

  The control unit 20 determines a correction write current value for adjusting the track write width in units of sectors, based on the repeated variation of the track write width obtained as described above.

  FIG. 7 shows an example of the correction write current value and a data track written using the correction write current value. In FIG. 7, the # number in the upper row is the number of each data sector formed on the disk.

  As described above, the write width of the data track fluctuates due to repeated runout. The variation in the writing width can be measured by the method shown in FIG. Therefore, the control unit 20 determines a correction write current value obtained by correcting the write current value so as to approximate the average write width for each data sector, creates a current table, and stores it in the storage unit 21. Store. The average write width is indicated by a broken line in the middle of FIG. 7, and is, for example, an average value of the write width of one round of each data track on the disk. Further, examples of the correction write current value are shown as Iw1 and Iw2 in the lower part of FIG. The write current value before correction is also indicated by a one-dot chain line.

  The data tracks 1 and 2 shown in the middle stage of FIG. 7 show the write widths after being corrected by the correction write current values Iw1 and Iw2. That is, when the value of Iw1 becomes higher than the write current value before correction, the write width of the data track 1 becomes wider and becomes narrower when it becomes lower. The same applies to the data track 2. In the example of the data track 1, the write current value for correction of the data sectors Nos. 1, 4, 5, and 7 is set higher than the write current value before correction, and the correction of the data sectors No. 2, 3, and 6 is performed. The write current value for use is set lower than the write current value before correction. In this example, the control unit 10 determines the correction write current values Iw1 and Iw2 for each data sector according to the magnitude of the change in the write width of the data track 1. The correction amount from the write current value before correction of Iw1 and Iw2 is determined according to the magnitude of the change in the write width for each data sector. As a result, the writing width of the data rack 1 partially overwritten by the data track 2 can be brought close to the average writing width indicated by the broken line, and adjacent to the portion where the track width becomes narrow when reading data. The influence of leaking data track information can be reduced. Even when the data track 2 is overwritten with the data track on the inner circumference side, the variation in the write width can be corrected in the same manner as the data track 1, and thereafter the variation in the write width of all the data tracks is similarly performed. Can be corrected.

  FIG. 8 shows another example of the correction write current value and a data track written using the correction write current value. In FIG. 8, the control unit 20 obtains the write width Twn for each data sector by the method of FIG. 6, and compares these values with a preset threshold value. The comparison result is shown in the middle part of FIG. In the middle part of FIG. 8, a case where Twn is larger than the threshold is indicated by a white circle, and a case where Twn is smaller than the threshold is indicated by a black circle. The control unit 20 sets a correction write current value Iw1 for writing the data track 1 for the data sector smaller than the threshold (the write width is narrow) by a current value (Δ larger than the write current value iw before correction). iw + Δ), and the correction write current value Iw2 for writing the data track 2 overwriting the data track 1 is set as a current value (iw−Δ) smaller than the write current value iw before correction. In this example, correction write current values are set for the first and fifth data sectors. As a result, it is possible to correct the portion where the writing width of the data track 1 is narrowed so as to increase the writing width, and it is possible to reduce the influence such as leakage of information of the adjacent data track. Further, the correction write current value is set only when the write width Twn is lower than the threshold value, and the correction amount is also constant Δ, which reduces the operation load of the control unit 20 at the time of data track writing. can do.

  In the above description, the 512-byte sector format used in a general hard disk is assumed. However, there is a chance that a sector format of 4 kilobytes will be adopted in the future. In this case, by setting N = 8, it is possible to correct the variation in the write width with the same accuracy as the 512-byte sector. Accordingly, the correction write current values Iw1 and Iw2 are determined according to the magnitude of the change in the write width for each segment obtained by dividing the data sector into eight.

  Further, as yet another example of reducing the influence of repeated fluctuations in the write width, error correction of ECC (Error Correcting Code) when reading information for a data sector whose write width Twn is smaller than the threshold shown in FIG. You may comprise so that capability may be made high. The ECC circuit can correct errors up to ½ the number of ECC symbols added for error correction. However, the correction of the maximum number of symbols is not necessary for a sector with a small variation in write width. In many cases, it is possible to read without error even without executing. Therefore, the burden on the ECC circuit can be reduced by setting the number of correction symbols to the maximum only for data sectors smaller than the threshold. Further, by detecting a change in the write width for each segment obtained by finely dividing the data sector, detailed position information smaller than the threshold value can be obtained. If this is used as an erasure pointer and erasure correction is applied, an error symbol of about twice the maximum number of correction symbols can be corrected. The erasure pointer may be registered in the storage unit 21 together with the address information of the sector. By increasing the error correction capability, the quality of the read information can be maintained high even when the information of the adjacent data track leaks in the portion where the writing width is narrowed.

It is a block diagram showing the outline | summary of the disk apparatus based on embodiment of this invention. It is a schematic diagram of the head unit concerning the embodiment of the present invention. It is explanatory drawing showing the example of a recording of the position error detection signal which concerns on embodiment of this invention. It is explanatory drawing showing the example of a recording of the position error detection signal which concerns on embodiment of this invention. It is explanatory drawing showing the example of a recording of the position error detection signal which concerns on embodiment of this invention. It is a flowchart of the procedure which measures the repetitive fluctuation | variation of the write width of a data track. It is a figure which shows the example of the write-in current value for correction | amendment, and the data track written using this. It is a figure which shows the other example of the write-in current value for correction | amendment, and the data track written using this. It is a figure which shows the mode of the repeated fluctuation | variation of the write width of a data track.

Explanation of symbols

  10 heads, 12 recording media, 14 head units, 16 head drive control units, 18 read / write units, 20 control units, 21 storage units, 22 arms.

Claims (9)

A recording medium having a concentric or spiral data track, the data track formed by being partially overwritten by the adjacent inner or outer data track;
A head assembly including a recording head for writing information to the recording medium, and a reproducing head for reading information from the recording medium;
A control device for controlling a writing operation of the head assembly to the recording medium;
Including
The control device detects repetitive fluctuations in the write width of the data track, determines a correction write current value for correcting the repetitive fluctuations, and performs the writing based on the correction write current value A disk device characterized by executing operation control.   2. The disk apparatus according to claim 1, wherein position error detection signals having different phases are recorded on the recording medium repeatedly in the track direction, shifted by a track pitch in the track width direction, and the control device performs the reproduction. 2. A disk apparatus, comprising: detecting a repetitive change in a write width of the data track based on the position error detection signal read by a head.   2. The disk device according to claim 1, wherein the correction write current value is determined for each data track for each data sector.   2. The disk device according to claim 1, wherein the correction write current value is determined for each data track for each segment obtained by dividing the data sector.   2. The disk device according to claim 1, wherein the correction write current value is determined only for a data sector in which a variation amount of the write width exceeds a predetermined threshold value.   5. The disk apparatus according to claim 4, wherein the write current value for correction is determined only for a segment in which the fluctuation amount of the write width exceeds a predetermined threshold value.   6. The disk device according to claim 5, wherein the control device increases the number of ECC correction symbols in addition to the determination of the correction write current value for a sector in which the fluctuation amount of the write width exceeds a predetermined threshold. A disk device characterized by the above.   7. The disk device according to claim 6, wherein the control device executes erasure correction in addition to determination of the correction write current value for a segment in which the variation amount of the write width exceeds a predetermined threshold value. A disk unit. 2. The disk apparatus according to claim 1, wherein the correction write current value is stored at a position of the track formed on the recording medium immediately before jumping to the next track.

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