JP2006318649A - Magnetic disk drive system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a magnetic disk drive system which corrects a read or write position when writing or reading data onto or out of a magnetic disk to facilitate the position correction without being influenced by intrinsic problems in manufacturing of the magnetic head. <P>SOLUTION: A write head Hw and a read head Hr are movable on the rotating magnetic disk in a radial direction and arranged side by side with a distance. At specified write start timing t<SB>WG</SB>, the write head writes write information for measurement to a specified sector at 1st timing t<SB>W</SB>and then the read head reads the written information to detect specified position information included in the written information, thereby generating 2nd timing t<SB>DA</SB>. The interval between the 2nd timing and the write start timing is subtracted from the interval between the 1st timing and the 2nd timing to measure the head interval of the magnetic head along tracks. The head interval is used for correction control over magnetic head operation. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a magnetic disk drive system connected to a computer and capable of writing or reading data, and more particularly, writing data to a magnetic disk by correcting manufacturing errors with respect to the interval between the write head and the read head. The present invention relates to a magnetic disk drive system that can improve the format efficiency of the disk by adjusting the timing of the recording medium, and can further increase the track density by adjusting the head position for reading data from the magnetic disk.

  A magnetic disk drive system is indispensable for data processing for a computer, and is used for recording and reading / reproducing data as a hard disk drive (HDD) with the spread of personal computers. Recently, not only for personal computers but also for AV devices and in-vehicle devices, the application range has been expanded. In addition, the information handled by them varies widely, and the amount of data may become enormous, and the recording capacity of the magnetic disk drive system is being expanded.

  Accordingly, FIG. 23 shows a schematic system of a conventional magnetic disk device used as an HDD in a block configuration. The magnetic disk device 1 is roughly divided into two parts, and is composed of a disk enclosure unit 2 and a printed circuit board unit 3, and these two parts are usually provided in an integral casing. The magnetic disk device 1 is connected to a host system (HOST) 4 such as a personal computer.

  The disk enclosure unit 2 includes a magnetic disk 21, a magnetic head 22, a spindle motor (SPM) 24, a voice coil motor (VCM) 25, and a head IC (HIC) 26. The magnetic disk 21 includes a spindle motor 24. Is rotated at a high speed in a certain direction. The magnetic head 22 is fixed to the tip of a head arm 23 attached to the voice coil motor 25, and when the voice coil motor 25 is driven, the disk radial direction intersects with a track (or cylinder) on the magnetic disk 21. The desired track (or cylinder) on the rotating magnetic disk 21 can be scanned.

FIG. 24 shows a specific configuration of the magnetic head 22. Some magnetic heads used in magnetic disk devices perform writing and reading with the same head, but here, the case where writing and reading are performed with separate heads is shown. As shown in FIG. 24A, the head unit H is disposed at the tip of the magnetic head 22 attached to the tip of the head arm 23. The head unit H, includes a write head H _w and the read head H _r, they are arranged in relation as shown in FIG. 24 (b), at the tip of the head arm 23, a magnetic disk 21 above The tracks are juxtaposed and fixed in the circumferential direction. Although not shown, a ramp mechanism that normally engages the tip of the arm is provided to keep the magnetic head 21 away from the magnetic disk 21 when the magnetic head 21 is not scanned.

Here, with the recent increase in capacity of the magnetic disk device, an MR head corresponding to a high bit density is often used as the magnetic head 21. MR heads are characterized by having a separate write core as read core and write head H _w of the one head as a read head H _r, the magnetoresistive element in the read core and, using the inductive element to write core It is common.

As shown in FIG. 24 (b), the read head _{H r} is the track direction of thickness _{G r,} and the write head _{H w} has a thickness _{G w,} when viewed in the track direction, their core The centers are separated by a distance X between the centers, and the centers of the cores are shifted by a distance Y in the radial direction of the magnetic disk 21.

FIG. 25 shows an outline of the positional relationship between the magnetic disk 21 and the magnetic head 22. The magnetic disk 21 is rotated at a high speed in one direction around the SPM by the spindle motor 24. On the magnetic disk 21 rotating at high speed, the magnetism and the head 22 perform a seek operation by driving control of the voice coil motor 25. Here, when a seek operation is performed for data writing, the distance B between the write core center of the write head and the VCM center in the magnetic head 22 and the distance C between the SPM center and the VCM center are constant. There is a distance r between the write core center of the magnetic head 22 and the SPM center of the magnetic disk 21, and an angle formed by a line between the write core center of the magnetic head 22 and the SPM center of the magnetic disk 21 and the axis of the arm 23. θ ₂ changes according to the seek operation.

In the magnetic disk device 1 configured as described above, the read head H _r and the write head H _w are arranged separately and separated from each other by the distance X, and further, they are shifted by the distance Y. The head unit H itself is attached to the head arm 23 at an angle. Therefore, as shown in FIG. 26, a head unit H and the head arm 23, and the positional relationship changes between the track on the magnetic disk 21, in the read head H _r and the write head H _w timing of on-track magnetic It differs depending on the track position of the disk 21.

The state of the change is schematically shown in FIG. In the example, the head arm 23 is driven by the voice coil motor 25 and rotated around the VCM by a rotary method. The thick line in the figure represents the head unit H, and it is assumed that the read head _Hr and the write head _Hw are attached to both ends thereof. For example, when on-track to the intermediate peripheral track is a line connecting the centers of the read head H _r and the write head H _w in the head unit H is almost identical to the segment of the track on-track, between their head distance _{T 2} are becomes to correspond to the distance _{G 0} shown in FIG. 24 (b). Also, looking at the track with it from the outer periphery is also, or on the inner periphery, and that each of the read head H _r and the write head H _w is the timing with which to reach the same track. Therefore, in order to on-track each head to the outer or inner track from the position of the illustrated middle track, the rotational drive of the head arm 23 is adjusted according to the track position.

  The operation of the magnetic disk apparatus 1 shown in FIG. 23 will be described. The recording data read by the reading head Hr is sent to the head IC 26, and the head IC 26 amplifies and outputs the recording data as a reproduction signal. When a recording signal to the magnetic head 22 is supplied to the head IC 26, the head IC 26 sends recording data to the magnetic head 22 and records it at a write position of a predetermined track on the magnetic disk 21.

  On the other hand, the printed circuit board unit 3 includes an MPU 31, a hard disk controller (HDC) 32, a read / write channel unit (RDC) 33, a servo controller (SVC) 34, a flash ROM 35, and a data buffer memory (DBM) 36. These are attached to the substrate.

  The MPU 31 operates according to a program stored in the ROM 35 and controls the entire system of the magnetic disk device 1. The MPU 31 mainly controls positioning of the magnetic head 22, interface control, initialization and setting of each peripheral LSI, and defect management. And so on.

  The hard disk controller 32 has a built-in RAM and includes error correction, PLL clock generation, and the like, and serves as an interface for managing input / output with the host system 4. Further, the servo controller 34 operates to drive the spindle motor 24 and the voice coil motor 25, and in accordance with a command from the MPU 31, a driver for the spindle motor 24 and a driver for the voice coil motor 25 are respectively provided. Control.

  The read / write channel unit 33 modulates write data to the magnetic disk 21 supplied from the hard disk controller 32 and outputs the data to the head IC 36, or the head IC 36 read from the magnetic disk 21 by the magnetic head 22. The data is detected from the output signal and the code is demodulated and output to the hard disk controller 32.

The magnetic disk device 1 is configured as described above, and data is written on, recorded in, or recorded on concentric tracks on the magnetic disk 22 traced by the magnetic head 22. 22 is read and reproduced. For writing the data, the write head H _w provided in the magnetic head 22, and, for data read, also read head H _r is responsible, respectively.

  Here, a signal flow at the time of data writing will be described. A data write command and data to a certain logical block address are transferred from the host system 4 to the hard disk controller HDC 33. The HDC 32 determines the track number, head number, and sector number, which are physical addresses, from the logical block address, and passes the physical address information to be written to the MCU 31. The MCU 31 controls the servo controller SVC 34 that drives the head arm 23 to move the magnetic head 22 to a target track.

  The MCU 31 controls the preamplifier. Therefore, a physical head that is a target head is selected from a plurality of heads corresponding to a plurality of magnetic disks. The data once stored in the buffer memory 36 is sent to the RDC 33 via the HDC 32. At the same time, the HDC 32 creates a write gate (WG) at the timing of the target sector and sends it to the RDC 33 and the preamplifier. The RDC 33 modulates data for writing to the magnetic disk 21 and sends it to the preamplifier as write data. The preamplifier receives the write gate generated by the HDC 32, enters the write mode, and passes a write current corresponding to the write data to the write head Hw. Writing to the magnetic disk 21 is performed by this series of operations.

Next, the flow of signals when reading data will be described. A data read instruction at a certain logical block address is transferred from the host system 4 to the HDC 32. The HDC 32 determines the physical address from the logical block address and sends the physical address information to be read to the MCU 31 as in the writing. The MCU 31 controls the SVC 34 to move the magnetic head 22 to the target track. The HDC 32 opens a read gate (RG) for the target sector. In the magnetic resistance device according to the read head H _r, the resistance value by recorded magnetic flux on the magnetic disk 21 is changed at the time of writing, the preamplifier amplifies the voltage change based on the change in resistance, and transmits to the RDC 33. The RDC 33 demodulates data of the waveform of the signal received from the preamplifier and sends it to the HDC 32. Data once stored in the buffer memory 36 from the HDC 32 is transferred to the host system 4 via the HDC 32.

  Next, an example of medium information recorded on the magnetic disk 21 is shown with reference to FIG. The medium information shown is recorded in one of a plurality of sectors provided on the track of the magnetic disk 21, and the medium information is roughly divided into a servo part and a data part. For a plurality of tracks arranged concentrically on the magnetic disk 21, a plurality of servo section data are arranged in a radial signal pattern. By using this servo section data, highly accurate servo control of the magnetic disk 21 is performed, and the data density is increased.

  Here, the servo unit will be described. The servo preamble part SP is a preparation section for demodulating the servo signal, and the AGC circuit adjusts the amplitude in order to keep the head output constant. At the same time, the PLL circuit is adjusted so as to match the signal waveform and the phase of the servo decode circuit. Further, the sync mark portion SM indicates that the code after this is the Gray code GC. The SM plays a role of a reference timing for a positioning operation, a writing operation, a reading operation, and the like. In the gray code portion GC, track position information is recorded.

  Further, the position portion P includes amplitude information for positioning the magnetic head 22 on the track, and each data of burst A, burst B, burst C, and burst D is recorded. These burst data are written following the gray code portion GC and have relative position information of the magnetic head 22 with respect to the track. In general, burst data is composed of these four signal patterns, and these signal patterns are written so as to be sequentially arranged over two tracks adjacent to the track. The relative position between the center of the track and the position of the magnetic head 22 can be calculated from the amplitude of the signal obtained by reading the track with the magnetic head 22, and it is determined whether or not the on-track has been performed by the combination of the magnitudes of the burst amplitudes. Used to control the position of the magnetic head 22.

  Next, the data part will be described. Similar to the servo unit, the data preamble unit DP is a preparation section for enabling reading of the magnetic head output, and the AGC circuit adjusts the amplitude in order to keep the magnetic head output constant. At the same time, the PLL circuit is adjusted so that the signal waveform and the data demodulating circuit are in phase. The sync byte part SB (hereinafter referred to as SB) is data start position information for indicating that the subsequent data is data. The AGC circuit adjusts the amplitude, and at the same time, the PLL circuit adjusts the phase of the demodulation timing. After the optimum output and phase alignment are completed, the RDC 33 opens an SB window (hereinafter referred to as SBW) and enters an operation of searching for an SB. If the SB is found, the RDC 33 recognizes the subsequent data as data and demodulates the read data.

In the data part DA, data transmitted from the host system 4 is recorded. Subsequent to DA, an error correction unit ECC is arranged at the end of the data portion, and information for performing error correction is recorded. One pad portion is provided for each front end of the servo portion and between the servo portion and the data portion. This is a margin intervals for the variation amount of the writing position misalignment due to the distance error between the read head H _r and the write head H _w. In this example, there is one SB portion, but a format having a plurality of SBs may be used.

  The magnetic disk device as described above is used as a data storage device such as a computer. As described above, the MR head is used as the magnetic head of this magnetic disk apparatus. This MR head realizes high bit density recording by separately having a read head core and a write head core in one magnetic head.

  However, the read head core and the write head core used in the MR head are fine elements, and when incorporated as a magnetic head, the read head core and the write head core are separated as shown in FIG. It is arranged with. Due to these, there are manufacturing variations with respect to the relative positions of the read head core and the write head core. Specifically, for each magnetic head, an error occurs between the center of the read head core and the center distance of the write head core.

  In general, since a magnetic disk device uses a rotation mechanism for both the magnetic recording medium and the head carriage unit, as described with reference to FIG. 27, the angle between the axis of the magnetic head and the track depends on the position of the magnetic head. And the distance between the center of the read head core and the center of the write head core in the track direction changes with respect to the track. Further, since the distance between the write head core and the read head core varies for each magnetic head, the position actually written on the magnetic disk with respect to the positioning information read by the read head core varies depending on the magnetic head.

  Conventionally, a fixed interval that does not take into account the variation of the magnetic head from the design target distance or the average distance at the time of manufacture is provided, and the timing at the time of writing and reading is changed by that amount, and the margin for variation is the margin time on the format I had.

  However, when the positioning information read by the read head core is written at a certain timing, when actually written on the magnetic disk, the position written by the magnetic head is affected by the variation in the distance between the write head core and the read head core. Deviation occurs.

  When the writing position deviation becomes large, a phenomenon occurs in which the positioning servo information is overwritten and erased. Here, in order to prevent this overwriting phenomenon from occurring, it is necessary to allow sufficient time for formatting. When such a measure is adopted, the format efficiency is deteriorated by the time margin. Furthermore, in devices using magnetic disks, the increase in transfer speed in recent years and the increase in bit density increase the influence of the distance error between the write head core and read head core, and the deterioration in format efficiency cannot be ignored. I came.

  In this magnetic head, since the read head core and the write head core are separate, due to manufacturing variations, a deviation occurs between the center of the read head core and the center of the write head core. Since both use the rotation mechanism, the angle of the magnetic head axis and the track changes depending on the position of the magnetic head, and the shift amount between the center of the read head core and the center of the write head core changes with respect to the track. Due to this phenomenon, conventionally, the track position is changed and the off-track margin is measured, and the correction positions are corrected by connecting the correction positions with straight lines.

  However, even if such measures are taken, in recent years, the track density of the utilization device has been increased, and even the linear correction cannot be performed. For this reason, there is a problem that not only the error rate is lowered, but also a failure of erasing the recording data of the adjacent track occurs. If the error is to be reduced by linear correction, the number of measurement points must be increased. As a result, a large amount of time must be spent in measuring the offset margin at the time of shipment because the number of measurement points has increased, making it unsuitable for mass production. In addition, the increase in the number of measurement points increases the correction value, the amount of the table for storing the correction value increases, and there is a problem that the memory is compressed.

  Further, in this magnetic head, since the amount of deviation between the center of the read head core and the center of the write head core with respect to the track changes, the track position is changed to measure off-track merge and correct the amount of deviation of the magnetic head core. Therefore, in order to obtain the best positioning accuracy at the time of writing, the writing head core is positioned at the center of the target track at the time of writing, and at the time of reading, the deviation of the head core is offset to move the reading head core to the writing position. Control is in progress.

  Since this deviation information is a value unique to the magnetic head, it is stored in a specific sector of the magnetic disk in the utilization device. Conventionally, until the specific sector is read, the read operation is performed by searching for the specific sector by using the design target or the deviation correction amount of the manufacturing design average and rereading while changing the offset amount. It was.

  In some cases, the magnetic head specific deviation amount is recorded in a non-volatile memory such as a flash ROM. In that case, information is read from the non-volatile memory when the power is turned on, and an offset amount is added when reading a specific sector. I was trying to read it. However, in recent years, in order to increase the track density of the utilization device, the width of the write head core itself is reduced, and the amount of deviation from the track width is increased. In such a situation, when a read operation is performed using an initial value that uses a design target or manufacturing average, a number of offset restorations are required before searching for a specific sector in which the amount of deviation inherent in the magnetic head is stored. The number of readings is required. Depending on the case, a phenomenon that the data cannot be read normally occurs.

  In addition, when recording unique information in the nonvolatile memory, it is possible to easily read a specific sector when the power is turned on. However, since the nonvolatile memory must be mounted, the cost increases. Furthermore, in this case, since it is not easy to replace the printed circuit board on which the nonvolatile memory is mounted, the repair work when the printed circuit board is broken cannot be easily performed, and the repair process takes a long time. There is a point.

  Therefore, in the present invention, when a magnetic head having a read head and a write head is used, the read position or the write position is corrected when data is written to or read from the magnetic disk. It is an object of the present invention to provide a magnetic disk drive system that can avoid the influence of problems inherent to a magnetic head during manufacture and can simplify the means for position correction.

  In order to solve the above problems, in the present invention, a magnetic head capable of moving in the radial direction of a disk on a rotating magnetic disk has a write head and a read head juxtaposed at a distance, and data is stored in the magnetic disk. In the magnetic disk drive system that can read or write data from the magnetic disk, when the magnetic head is on-tracked to the measurement track, the measurement write information is written to the write head at a predetermined write start timing. Next, the magnetic head is offset from the on-track position by a predetermined offset amount in the radial direction of the disk, and the predetermined offset amount is subtracted from the offset position every rotation of the magnetic disk. Read information for measurement with a read head And a head interval measuring means for measuring the head interval in the radial direction of the magnetic disk based on the offset amount when the write information can be read, and the measured head interval information is stored. Storage means and control means for correcting the operation of the magnetic head based on the head interval information read from the storage means.

  The head interval measuring means performs the head interval measurement at a plurality of track positions on the magnetic disk, and further, based on the plurality of head intervals, calculates an n-order polynomial relating to the head interval with respect to the track positions. It was decided to generate.

  The head interval measuring means stores the order coefficient in the n-th order polynomial in the storage means, and the control means at a track position to be on-tracked based on the order coefficient when performing a read operation with the read head. The head interval is obtained, and an offset amount based on the head interval is added to the track position to perform read seek.

  In addition, when writing the specific information to the predetermined track position by the writing head, the control unit reads the head interval information corresponding to the predetermined track position from the storage unit, and generates correction information based on the head interval information. Then, after the magnetic head is on-tracked to the predetermined track position, the specific information is written by the write head at a position shifted from the predetermined track position by the correction information amount.

  According to the magnetic disk drive system of the present invention, the distance between the write head and the read head in the magnetic head is measured by using the actual magnetic head, so that the apparatus due to manufacturing variations, rotational fluctuations, etc. Specific information can be grasped, and control related to the timing of writing or reading by the magnetic head and the track position of the magnetic head can be accurately executed based on the apparatus specific information such as the amount of core deviation.

  Since the distance in the track direction between the write head and the read head is calculated, the write operation is performed at the timing according to this distance, so that not only the manufacturing error of the distance between the magnetic heads can be absorbed, but also the servo. Information and the like can be prevented from being overwritten, and the data write timing can be determined accurately. Therefore, it is not necessary to give time to the format of the magnetic disk, and the format efficiency can be improved in response to the higher bit density.

  Further, according to the magnetic disk drive system of the present invention, in the control of the track position in the disk radial direction related to the seek operation of the magnetic head, n is measured with respect to a plurality of measurement points at which the core misalignment between the write head and the read head is measured. By correcting the position of each track using a second-order polynomial, the error caused by the correction can be significantly reduced from the correction error due to the straight line correction, and is appropriately corrected for the amount of core deviation.

  Therefore, the spread of writing to adjacent tracks by the magnetic head can be suppressed, and the error rate can be improved. Moreover, since the number of measurement points of the core deviation amount is small and the error can be reduced, the correction value table amount can also be reduced and the storage memory is not compressed. And it is possible to produce efficiently without reducing the time in the test process in manufacturing the magnetic disk device.

  Furthermore, according to the magnetic disk drive system of the present invention, the measured core deviation amount in the disk radial direction between the write head and the read head is measured, and at the write position offset based on the core deviation amount and the initial offset value, When the device specific information including the amount of core deviation is written in a specific sector and the device specific information read command is received, the magnetic head is simply offset by adding the initial offset value to the on-track target value. The position can be matched to the light position. For this reason, when the power is turned on, there is no need to re-read the device-specific information by the reading head, and the apparatus can be instantly started.

  The initial offset value to be used is originally stored in the ROM, and the measured device specific information is written in a specific sector of the magnetic disk. Therefore, it is not necessary to use a specially prepared non-volatile memory, and the firmware can be made into a mask ROM, thereby reducing the cost.

Next, an embodiment of a magnetic disk drive system according to the present invention will be described with reference to the drawings. In the following, embodiments will be described separately according to the method of correcting the reading position or writing position when writing data to or reading data from the magnetic disk.
[First Embodiment]
In the first embodiment, for the write head and the read head in the magnetic head to be used, the distance between the heads in the track direction is measured, and the data write position is corrected based on the measured head distance. As a result, even if there is a manufacturing head specific error in head spacing, when writing data to each track, the influence of this error is eliminated, and the data writing start timing can be accurately taken It can be a system. The first embodiment will be described with reference to FIGS. 1 to 7.

  First, a method for measuring the spacing between the heads in the track direction for the write head and the read head in the magnetic head to be used will be described. In measuring the head interval, a specific track on the magnetic disk corresponding to the magnetic head to be used is selected, and measurement data is written to the specific track by the magnetic head. Thereafter, the measurement data written in the specific track is read by the magnetic head. Therefore, the head interval related to the magnetic head is obtained from the write timing and the read timing related to the measurement data. Here, an example of a method of using the sync byte unit SB in order to measure the track direction distance between the write head and the read head will be described. In this example, the case where the write head is arranged behind the read head is shown.

  FIG. 1 shows an example of medium information for measurement. The medium information for measurement has the same format as the medium information shown in FIG. FIG. 1 shows the timing of the writing operation by the magnetic head for the medium information for measurement.

First, the magnetic head is on-tracked to a specific track for measurement. Next, medium information for measurement is written in a sector at an appropriate position by using the magnetic head. At this time, based on the timing t _SM of the SM detection, plus the time T _a to the data portion starting on Fuomatto interval plus head distance T _b of further write-read in anticipation maximum variation (W / R) At _Tc , the write gate WG is generated. The WG at the timing _{t WG} to be opened, said data preamble part DP, the sync byte unit SB, the data unit DA, ECC unit and the like are sequentially written. However, since the timing t _WG is based on the read head H _r and the write head H _w is arranged behind the read head H _r , the actual start of writing is the start of WG from the timing _{t WG,} it is a timing _{t W} which is obtained by subtracting the W / R head real interval.

Next, the measurement data written in the sector on the specific track is read. The state of this reading operation is shown in FIG. The medium information in the figure is for measurement written on the specific track shown in FIG. Against SM, the timing _{t RG} time _{T a} to the data portion starting on Fuomatto, RG is generated. When the RG is opened, a signal waveform is input to the data reading circuit of the RDC 33.

In the position t _SBW of W / R maximum variation anticipation of time of the head interval T _b, open the sync byte window SBW for detecting the sync byte unit SB, performs the read operation of the data. If, in the first SBW1, if SB can not be detected, after the rotational delay round, again, to open the RG at the timing _{t RG,} open a SBW2 to spread than initially SBW width. This operation is repeated until SB can be detected. FIG. 2 shows that SB is detected at timing t _DA when SBW 3 is opened.

Therefore, as shown in FIG. 3, a timing t _DA, actually from the timing t _WG where the data writing, the time difference T _X between the write head H _w and the read head H _r is be calculated. Its formula is, SM / WG interval _T c, SM / RG interval _T a, RG / WG interval _T d, the the RG / SB detection interval and _{T e,
T X = (T c -T a} ) - {T e - (T DP + T SB)}
It becomes. The data time of the data preamble part DP is T _DP and the data time of the sync byte part SB is T _SB , which are known. _Here, since it is T _{d =} T c -T _a, equation representing the W / R head interval _{T X} is
_{T X = T d - (T} e -T DP -T SB)
It becomes.

  Since the influence of rotational fluctuation of the magnetic disk, jitter of signal timing, etc. can be considered, the SB position can be obtained more accurately by measuring the SB position by repeatedly writing and reading several times. It is possible to accurately determine the time between the heads.

  Next, FIG. 4 shows another example of the method for measuring the time between heads. In the above description, the method of increasing the window width of the SBW for each read operation is adopted for detecting the sync byte portion SB. However, in the method of FIG. 4, the window width is increased in the first sync byte window SBW. In addition, SB can be detected at one time.

As described above, the width at which the SBW is opened is not changed every time reading is performed, and the width at which the SBW is opened is always wide enough so that the SB falls within the width. As shown in FIG. 4, when the SBW 3 is opened, the SB detection signal is generated at the timing t _DA when the SB is detected. Therefore, the interval T _f from the RG to the SB detection signal is measured and used to calculate the head interval T _X. The calculation formula is
_{T X = T d - {T} f - (T DP + T SB)}
It becomes. In this equation, since T _d , T _DP and T _SB are known, the head interval T _X can be obtained if the interval T _f is measured.

As shown in FIG. 26, the relative distance between the track direction between the position error read head H _r and the write head H _w of manufacturing the magnetic head, but changes according to the track position, the magnetic head by previously measuring the inter-head distance T _X, it is possible to accurately determine the timing t _WG open the write gate WG for each track. In this case, the measured head distance T _X, so has to have been included positional error in manufacturing the read head H _r and the write head H _w, overwrite such as a servo information by the position error Thus, data writing can be executed reliably and accurately at a desired writing position in correspondence with each track. Here, even if the distance between the heads is not measured for all the tracks, the measurement is performed on several tracks on the magnetic disk, and the interpolated tracks are interpolated based on each measurement result. Thus, the measurement processing time can be shortened, writing can be performed at a more accurate position, and the magnetic disk can be used more effectively.

  In the examples described so far, the method for measuring the distance between the heads using SB is given as an example. However, the write head is based on the information that can specify the timing among the medium information written to the magnetic head. As long as the time interval between the reading heads can be measured, the method is not limited to this method.

  Next, FIGS. 5 and 6 show flowcharts of sequence examples when the measured head interval information is applied to the magnetic disk drive system.

  The flowchart of FIG. 5 shows a case where the head interval information for each track obtained based on the measured head-to-head distance is written as specific information on the magnetic disk in a specific sector on the magnetic disk.

  In this case, when the magnetic disk device 1 is powered on (step S101), the MCU 31 issues a read command to a specific sector in which head specific information is written on the magnetic disk 21 (step S102).

  Next, the SVC 34 performs a seek operation of the magnetic head to a specific sector in accordance with this read command (Step S103), and the RDC 33 performs a read operation from the read data transmitted from the HIC 26 (Step S104).

The information written as the head specific information is extracted based on the read data and stored in the data buffer memory DBM 36 (step S105). Here, an example of the head interval information included as the head specific information is shown in the following table format.
(Table) Track number Head 0 Head 1
0h ~ 100ns 200ns
1000h ~ 150ns 250ns
2000h ~ 200ns 300ns
3000h ~ 220ns 330ns
4000h ~ 250ns 360ns
5000h ~ 230ns 350ns
6000h ~ 210ns 330ns
7000h to Max 180ns 300ns
Here, the track number is expressed in hexadecimal, and the magnetic disk device 1 shows a case where two magnetic heads are provided. In this way, the head interval information is expanded corresponding to the track number. Then, the head interval value corresponding to the general track that needs data writing is read from this table and used to determine the write timing.

  The flowchart of FIG. 6 shows a case where the head specific information is not written in a specific sector on the magnetic disk but is stored in a nonvolatile memory in the magnetic disk device 1.

  In this case, first, when the magnetic disk device 1 is powered on (step S121), the MCU 31 issues a head interval information read command as head specific information (step S122).

  Next, the head interval information written in the nonvolatile memory as the head specific information is read and stored in the data buffer memory DBM 36 (step S123). The head interval information stored here is the same as the table described above.

  The method of using the head interval information stored in the DBM 36 is the same as in the case of FIG. 5, but in the case of FIG. 6, since the head interval information was originally stored in the nonvolatile memory, FIG. As in the case of, the seek operation for reading the head interval information is not required.

  The operations in the above flowchart are steps until the head interval information is acquired. Next, referring to the flowchart of FIG. 7, the timing of the write gate WG is determined based on the acquired head interval information. An operation for writing data will be described.

  First, a data write command is transmitted from the host system 4 as a host to the magnetic disk device 1 (step S131).

  The magnetic disk device 1 receives the data write command by the HDC 32 and, based on the command, calculates the physical head, track, and sector from the included logical address (step S132).

  If a plurality of magnetic heads are installed in the disk enclosure unit 2, the magnetic head according to the logical address is selected (step S133), and the magnetic head is sought to the determined target track (step S133). S134).

Therefore, the HDC 32 reads the W / R head interval value at the target track position from the table stored in the DBM 36 for the magnetic head to be used (step S135), and based on this head interval value, The creation timing _tWG is calculated (step S136). The timing t _WG is the gap T _a between the data portion starting on SM detection timing and format, is read from the table is calculated from the head interval value T _X, it is expressed by the following equation.
t _WG = T _a + T _X
Thus, to determine the timing t _WG by adding the head gap value TX in interval T _a is because the position of the write head H _w is assumed that is after the read head H _r, these if the head position relation reversed, the timing t _WG is calculated by subtracting the head interval value T _X from the interval T _a. Thus, according to the data write command, the timing for opening the write gate WG can be determined by calculation based on the corresponding head interval value read from the table (step S137). In step S134, since the magnetic head has already been sought to the target track, a WG can be generated and data can be written at a predetermined position in the target sector.

As described above, the actual head interval between the write head H _w and the read head H _w in the magnetic head to be used is measured, and the head interval value for each track is generated based on the measured head interval. According to the head interval value, the change in the head interval according to the track position can be corrected, and the start timing at which writing can be performed can be accurately obtained. Even if there is a variation in manufacturing the magnetic head, it is not affected by an error due to the variation.

In the first embodiment, as an example of correcting the head interval, an example in which the head interval value is corrected in a table format has been shown. Instead of storing in the table format, an n-order polynomial having a track number as a function is used. A correction method is also conceivable.
[Second Embodiment]
In the first embodiment, the change in the head interval in the circumferential direction of the magnetic disk, that is, in the track direction is mainly corrected. In the second embodiment, the radial direction of the magnetic disk, that is, in the adjacent track. Corrected misalignment.

  As described above, the MR head suitable for high bit density recording is used for the magnetic head 22 in the magnetic disk device 1 shown in FIG. Since this magnetic head has a read head core and a write head core separately, a deviation occurs between the center of the read head core and the center of the write head core due to manufacturing variations. In addition, since both the magnetic disk and the head carriage unit use a rotation mechanism, the angle θ between the head and the track changes depending on the position of the head as shown in FIGS. The amount of deviation Y between the center of the head core and the center of the writing head core changes.

  Due to this phenomenon, conventionally, the track position is changed and the off-track margin is measured, and the correction positions are corrected by connecting the correction positions with straight lines. Therefore, the amount of deviation from the magnetic head core will be described.

Since the magnetic disk 21 rotates, the track draws a circle around the axis of the spindle motor SPM 24. On the other hand, the magnetic head 22 is rotated in the head arm 23 by the voice coil motor VCM 25, moved in a direction crossing the track drawing a circle, and the track position is changed. The magnetic head 22 is attached to the head arm 23 with a certain angle. Then, the center of the read head core H _r and the write head core H _w is not a left-right symmetry. With the above arrangement state, the position of the read head H _r and the write head H _w with respect to the track is simply not constant difference.

Here, when the thickness of the read head H _r is G _r , the thickness of the write head H _w is G _w , and the distance between the read head H _r and the write head H _w is _GL , the thickness center of the read head H _r and the write are written. The distance X of the thickness center of the head H _w is
X = G _r / 2 + G _w / 2 + X (1)
It becomes. When the amount of deviation between a center of the write head H _w of the read head H _r and Y, the distance G ₀ between the centers of the write head H _w of the read head H _r is
G ₀ = (X ² + Y ² ) ^1/2 (2)
It becomes. Also, if the angle between X and G ₀ is θ ₁ ,
θ ₁ = cos ⁻¹ {(X ² + G ₀ ² −Y ² ) / (2 × X × G ₀ )} (3)
It becomes. When the distance from the VCM center to the head gap center is B, the distance from the VCM center to the SPM center is C, and the distance from the SPM center to the track center is r, the angle θ ₂ between the VCM center-head gap-SPM center is
θ ₂ = cos ⁻¹ {(B ² + r ² −C ² ) / (2 × B ² × r)} (4)
It becomes.

From these, the deviation E between the center of the read head Hr and the center of the write head Hw is E = r− {r ² + G ₀ ² + 2 × r × cos (θ ₁ + θ ₂ )} ^1/2 (5)
It can be expressed as. This equation (5) indicates that the deviation E between the read head H _r and the write head H _w can be expressed as a function of r (the distance from the SPM center to the on-track center). That is, it shows that the deviation amount E can be expressed as a function of the track number.

For example, when the data area is in the radial direction of 21 mm to 45 mm from the SPM center and each of the above parameters is set to the following values, the read head H _{r is} expressed as a function for r from Equations (1) to (5). and when shown by the offset amount E concerning the write head H _w in the graph is as shown in FIG.
G _r = 0.1 μm
G _w = 0.2 μm
G _L = 40 μm
A = 0.6μm
B = 50.0mm
C = 60.0mm
Here, for example, a case will be described in which the data area is equally divided into four parts, the off-track margin is measured at five tracks, and used for deviation amount correction. Conventionally, with respect to the curve shown in FIG. 8, five points are connected by straight lines, and the four straight lines are used as the amount of deviation. FIG. 9 is a graph showing the correction error for the r position in the case of this straight line. According to the figure, the correction error should be 0 [m] originally, but in reality, the error remains larger toward the inner circumference.

  To reduce the error by complementing the straight line, a method of increasing the number of measurement points is conceivable. However, if the number of measurement points is increased, the occupation time in the shipping test process increases, which is not suitable for mass production.

  Therefore, in the second embodiment, instead of increasing the number of measurement points, an nth order polynomial passing through the measurement points is obtained so that it can be approximated to the curve shown in FIG. 8, and correction is performed based on the obtained polynomials. I decided to use it. FIG. 10 is a graph showing the correction error when the same measurement point as that in the above-described five-point linear correction capable of compressing the error is corrected by a fourth-order polynomial. Referring to the correction error graph of FIG. 10, it can be seen that the correction error is greatly reduced as compared with the case of the linear correction shown in FIG.

In the n-th order polynomial used here, if n = 4, the fourth-order polynomial E is
E = a × r ⁴ + b × r ³ + c × r ² + d × r + e (6)
It is expressed. The order can be appropriately selected so that the correction error is as close to 0 as possible. Then, the track number of the measurement point is substituted for the variable r, and the parameters a to e are calculated from the simultaneous equations. These parameters are stored, and when performing a seek operation, a core deviation correction value is calculated based on each parameter.

  When the above deviation correction method using the nth order polynomial is applied to a magnetic disk apparatus, first, the off-track margin for each magnetic head at the correction track position is measured. Then, the amount of deviation between the read head core and the write head core at each track position is measured. Based on the result, parameters of the respective orders in the correction polynomial (in the case of Equation (6), parameters a, b, c, d, and e) are obtained, and each parameter is used as correction data to specify the magnetic disk in the correction table format. Record it in the sector. At the time of power throwing, each parameter is read from a specific sector, and the correction table is developed in the memory. When the read command is received, the correction table of the magnetic head is read from the memory, the amount of deviation from the track position is calculated, and the offset amount during on-track is determined.

  The operation when this method is applied to a magnetic disk device is shown in FIGS.

  The flowcharts of FIGS. 11 and 12 show the operation when measuring the off-track margin for each magnetic head at the correction track position. The flowchart in FIG. 11 shows a case where measurement is performed from the in side with respect to the correction track position when measuring the off-track margin, and the flowchart in FIG. 12 shows a case where measurement is performed from the outer side.

  In the flowchart of FIG. 11, first, the magnetic head to be measured is selected, and the magnetic head is sought to the measurement track (step S201). This measurement track is used only for measurement, and is overwritten with other data after the measurement is completed. Therefore, any track can be selected. For example, a track in which a specific sector is recorded can be used. The magnetic head is on-track on the measurement track or near the measurement track.

When the seek operation of the magnetic head is performed, writing the measurement data to the measuring track by the write head H _w (step S202).

  Next, in consideration of where the measurement data can be read at most by the magnetic head, the offset is added and the magnetic head is sought (step S203). Here, since measurement is performed from the in side, the track number is offset to the increasing side.

Therefore, setting the read count to 0 (step S204), and starts the read operation at the read head _{H r} (step S205).

  First, it is determined whether or not the measurement data can be read at that position (step S206). If the measurement data can be read (Yes), it is assumed that there is one read OK sector and the number of readings is determined. 1 is added (step S208).

  On the other hand, when the measurement data cannot be read (No), the offset amount is decremented by 1 so that the measurement data can be read (step S207). Read operation is performed at a position with a small offset amount. As described above, the reading operation is repeated until the measurement data can be read at a position offset by 1 for each rotation of the magnetic disk.

  In step S208, the number of read OK sectors is counted for each rotation of the magnetic disk at a specific offset position subtracted by one. It is determined whether or not the count value has reached the specified number of times of reading OK (step S209). This takes into account the fluctuation factors in the rotating mechanism such as a magnetic disk.

  Therefore, when the read count of the read OK sector has not reached the specified number of times (No), the process returns to step S205 to perform a read operation at a specific offset position, and the read operation is repeated until the specified number of times is reached. . If the number of times the read OK sector has reached the specified number (Yes), it is possible to read the measurement data on the inner side, and the specific offset amount at that time is stored in the memory (step S210). ).

  In the above off-track margin measurement, the offset amount was provided on the inner side, but the inner side may not be able to grasp the reading state of the measurement data, or by offsetting to the outer side When the off-track margin is measured, the offset width of the same error rate can be obtained. Therefore, the center of the width may be used as the offset value.

  The flowchart of FIG. 12 shows the off-track margin measurement operation offset to the outer side. The measurement operation of the off-track margin in the flowchart of FIG. 12 is performed following the operation according to the flowchart shown in FIG. 11, but in the basic processing procedure as compared with that according to the flowchart shown in FIG. It is the same.

  However, in the operation shown in FIG. 12, since the offset is performed not on the inner side but on the outer side, the track number is decremented on the outer side in step S211, and the offset amount is decremented by 1 in step S215. The only difference is the operation in step S201 and step S207 in FIG.

  Next, the operation of calculating the correction value using the n-th order polynomial of Equation (6) will be described with reference to the flowchart of FIG. FIG. 13 shows an example using a fourth-order polynomial with n = 4, and measurement is performed at five points within the width of the data area of all tracks.

  First, assuming that the calculation starts from a magnetic head close to the printed circuit board, the head 0 is selected (step S221).

Then, read the center position _{Y m} of head 0 for correcting the position _{r m} from the memory (step S222). m represents the number of measurement points, and m = 1 to 5.

Next, based on the read center positions Y _{1 to} Y ₅ , parameters a, b, c, d, and e included in the polynomial are calculated using the fourth-order polynomial represented by Expression (6) (step S223). The calculated parameters a, b, c, d and e are stored as correction data in a specific sector on the magnetic disk (step S224).

  Here, since each parameter for correction is stored with respect to the head 0, the parameter calculation for the head 0 is finished, and when another magnetic head is equipped, for example, when there is the head 1, the head For 1 as well, as in the case of head 0, parameter calculation is performed and the result is stored in a specific sector.

In the operation so far according to FIG. 13, the correction polynomial is specified for each magnetic head in order to obtain the core shift amount E between the read head H _r and the write head H _w in the radial direction of the magnetic disk. Therefore, an operation of executing correction based on the amount of core deviation by the correction polynomial in the magnetic disk device will be described.

  The flowchart shown in FIG. 14 shows an operation for executing correction when the magnetic disk device is turned on. First, when the power is turned on (step S231), the magnetic head is moved to a specific sector. The correction data a, b, c, d and e related to each magnetic head are read from the specific sector, and each correction data is developed in the memory in correspondence with each magnetic head.

  After that, each time the seek operation of the magnetic head is performed, each parameter related to the magnetic head is read from the memory, and the amount of core deviation is calculated using an nth-order polynomial based on each parameter. Perform position control.

  Here, the operation when the magnetic disk device 1 receives a read command from the host system 4 is shown in the flowchart of FIG.

  When the HDC 32 of the magnetic disk device 1 is in a command standby state (step S241), a read seek command is received from the host system 4 (step S242).

  Therefore, in accordance with the received command, it is determined which magnetic head to seek, and correction data a, b, c, d, and e are read from the memory as the determined correction data for the magnetic head (step S243). The MCU 31 obtains the amount of core deviation Y at the seek destination using an n-th order polynomial based on the read parameters (step S244).

  Then, the magnetic head is sought and further corrected by adding an offset amount corresponding to the core deviation amount Y (step S245). This completes the read seek of the magnetic head based on the read seek command (step S246).

  By the above operation processing, an equation for correction by the nth-order polynomial for the track position is created from the amount of core misalignment between the write head and the read head measured at a plurality of track positions on the magnetic disk, and the track position is determined for each seek operation of the magnetic head. Since the core misalignment of the magnetic head corresponding to the above can be corrected, the manufacturing error related to the misalignment between the write head and the read head unique to the magnetic head can be absorbed.

  By adopting an nth order polynomial as the correction method, the correction error can be reduced even when the number of off-track margin measurements is small, and the correction data stored in the memory can be reduced.

Note that it is also possible to have a deviation amount as a correction table and calculate the degree of the correction polynomial after power-on, seek, etc.
[Third Embodiment]
In the magnetic disk drive system according to the second embodiment, the amount of core misalignment of the magnetic head corresponding to the track position is corrected by a correction n-order polynomial based on the amount of core misalignment between the write head and the read head measured at a plurality of track positions. A manufacturing error related to the amount of deviation between the write head and the read head inherent to the magnetic head is absorbed.

  Therefore, in the third embodiment, in order to absorb a manufacturing error related to the deviation amount between the write head and the read head unique to the magnetic head, the core deviation amount between the measured write head and the read head is measured, and the data When writing, shifted by the amount of core shift.

  As described above, the MR head is suitable for high bit density recording. However, since the read head core and the write head core are separately arranged, the center of the read head core is shifted from the center of the write head core due to manufacturing variations. Will occur. In addition, since the magnetic disk drive uses a rotating mechanism, the angle between the magnetic head and the track changes depending on the position of the magnetic head, and the amount of deviation between the center of the read head core and the center of the write head core with respect to the track also varies. Change.

As shown in FIG. 24, MR head 22 has the read head core _{H r} and the write head core _{H w} separately. When using the magnetic head, the data is written position, to be moved a read head H _r, since reading is impossible, at the time of reading, the write head H _w and the read head H _r of deviation of Y Seek with offset. Since the magnetic head is very small, it is impossible in manufacturing to eliminate the variation in the amount of deviation Y.

  For this reason, conventionally, the track position is changed, the off-track margin is measured, and the shift amount between the cores is corrected. To achieve the best positioning accuracy during writing, write data by positioning the read head core at the center of the target track when writing, and offset the amount of misalignment of each core when reading, and hold the read head core at the write position. We are doing control.

  Here, with respect to the conventional shift amount correction, the operation at power-on is shown in the flowchart of FIG.

  When the power is turned on (step S301), a read command is issued to a specific sector in which the device specific information is stored (step S302). The MCU 31 discriminates the command (step S303), performs a seek operation, and moves the magnetic head to a track having a specific sector (step 304).

  The magnetic head enters the read operation to the sector, and the initial value held in the ROM is used as the offset amount at this time (step S305). This initial value is common to products, and the actual amount of core deviation varies among products. For this reason, when data cannot be read for the first time (No in steps S306 and S307), reading is performed while adding a predetermined offset amount (step S308), and an operation for searching for a specific sector is started.

Here, the operation of searching for a specific sector is shown in FIGS. In the figure, for simplicity of illustration, the write head _{H w} and the read head _{H r} Yes in the same _{size, H r1, H r2, H} r3, ... are 1 to read head _{H r} of the magnetic disk A position shifted by a predetermined offset amount for each rotation is shown.

In Figure 17, the write position of data written by the write head H _w, continue to move the read head H _r, at a position of H _r3, shows a state in which read the written by the write head H _w data . However, as shown in FIG. 18, when the width of the read head core H _r is small, it can not be positioned to a position written and may not be able to find a particular sector. Further, as shown in FIG. 19, it can be prevented by reducing the offset increment, but the number of re-reads is increased, and a long time is required from the power-on to the normal startup.

Therefore, in the third embodiment, the deviation amount Y of the write head H _w and the read head H _r is focused to a device-specific information including a manufacturing error, the amount of deviation Y, off-track margin The data was written by shifting the offset amount based on this measurement. The off-track margin measurement process is performed according to the procedure shown in the flowcharts of FIGS.

An outline of the magnetic head control method according to the present embodiment is shown in FIG. Here, the magnetic head 22 has a write head H _w and the read head H _r, they are spaced apart by amount of core deviation Y in the radial direction of the magnetic disk. This core misalignment amount Y is a value unique to the apparatus including manufacturing errors, is obtained by off-track margin measurement, and is stored in the magnetic disk apparatus.

The example shown in FIG. 20 is a case where the initial offset value Y ₀ for correcting the core deviation is stored in the ROM of the magnetic disk device at the time of product shipment, and the initial offset value Y ₀ is the read head H _The amount of deviation in the radial direction from the center of _r is represented. Therefore, the write offset amount Y _0w from the center of the read head H _r when data is written is obtained. The write offset value Y _0w is the difference between the measured amount of core deviation Y and the initial offset value Y _0, obtained by signed calculation by equation Y _{0w = Y} + Y _0.

When writing device-specific information to the corresponding track, the magnetic head is on-tracked to the corresponding track, and further offset from the position in the radial direction by the write offset value Y _0w . After this offset, writing the information by the write head H _w. The written write position the write head H _w, as shown by the broken line in FIG. 20.

Then, when reading the device-specific information written in the write position, the on-track magnetic head to the appropriate track, further offsetting the magnetic head only radial initial offset value Y _0. In After this offset, the radial position of the read head H _r Since coincides with the write position information is written, the data can be read.

  According to such a magnetic head position control method, it is written with an offset so that it can be read simply by shifting it to the initial offset value. Thus, even if there is a manufacturing variation in the magnetic head, the influence of the variation can be eliminated.

  Next, the writing operation of the device specific information according to the present embodiment is shown in the flowchart of FIG. First, when a device-specific information write command is issued (step S321), the amount of core deviation due to off-track margin measurement is read from the memory (step S322), and the initial offset value is read from the ROM of the device (step S323).

Therefore, in order to obtain the write offset value _Y0w , a signed addition of the core shift amount and the initial offset value is executed (step S324).

  Then, the magnetic head is caused to seek to a track of a specific sector (step S325), and the magnetic head is moved in the radial direction to a position where the obtained write offset value is added to the on-track target value (step S326).

  When the magnetic head is offset from the on-track target value to the position of the write offset value, the device specific information is written to the specific sector (step S327). When this writing is completed, the device specific information related to the magnetic head is written. The operation ends. If a plurality of magnetic heads are installed, the process proceeds to a writing operation of device-specific information related to the next magnetic head (step S328).

  Next, the reading operation of the device specific information when the power is turned on in the magnetic head position control system of this embodiment will be described with reference to the flowchart of FIG.

  First, when the power is turned on (step S331), the initial offset value is read from the ROM (step S332). Then, a read command to a specific sector on the magnetic disk in which the magnetic head unique information is stored is issued (step S333).

  In accordance with this read command, the magnetic head performs a seek operation using the track position where the specific sector exists as a target value (step S334). At this time, the read initial offset value is added to the on-track target value, and the magnetic head is offset (step S335).

Therefore, since the position of the read head H _r of the magnetic head is coincident with the write position by the write head H _w, reads the device-specific information in the specific sector in the read head H _r (step S336). Then, the read core deviation amount unique to the magnetic head is developed in a memory table (step S337).

  This completes the flowchart for reading the device-specific information when the power is turned on. However, after the amount of core deviation unique to the magnetic head has been developed in the table, this amount of core deviation is the position of the magnetic head. Used for control (step S338).

As described above, since the magnetic head position control method in the magnetic disk device is adopted, the write core width is reduced by increasing the track density, the core deviation is increased with respect to the track width, and the design target or manufacturing average is used. Even when the initial offset value is used, it is not necessary to re-read the offset before searching for a specific sector in which the core misalignment specific to the magnetic head is stored, and information on the specific sector can be read instantaneously at the time of startup. . Further, no special nonvolatile memory is required for storing the magnetic head specific information.
(Appendix 1)
A magnetic head capable of moving in the radial direction of a disk on a rotating magnetic disk has a write head and a read head juxtaposed at a distance, and data can be written to or read from the magnetic disk. A magnetic disk drive system capable of
Head interval measuring means for measuring head interval information between the write head and the read head;
Storage means for storing the measured head interval information;
A magnetic disk drive system comprising: control means for correcting the operation of the magnetic head based on the head interval information read from the storage means.
(Appendix 2)
The magnetic disk drive system according to appendix 1, wherein the head interval information is stored in a specific sector at a predetermined track position on the magnetic disk.
(Appendix 3)
2. The magnetic disk drive system according to appendix 1, wherein the head interval information is stored in a nonvolatile memory provided in the system.
(Appendix 4)
The head interval measuring means instructs writing of measurement write information at a first timing by the write head to a sector selected for measurement at a predetermined write start timing, and then writes the write information by the read head. 4. The magnetic disk drive system according to any one of appendices 1 to 3, wherein information is read and predetermined position information included in the write information is detected to generate a second timing.
(Appendix 5)
The head interval measuring means subtracts the interval between the second timing and the write start timing from the interval between the first timing and the second imming, and measures the head interval in the track direction related to the magnetic head. The magnetic disk drive system according to appendix 4, characterized by:
(Appendix 6)
The head interval measurement means detects the predetermined position information in a search window, and the search the head interval measurement means detects the predetermined position information in a search window, and the search 6. The magnetic disk drive system according to appendix 4 or 5, wherein the window width of the recording window increases every rotation of the magnetic disk.
(Appendix 7)
The head interval measuring means detects the predetermined position information with a search window, and the window width of the search window is larger than the second timing. 5. The magnetic disk drive system according to 5.
(Appendix 8)
8. The magnetic disk drive system according to any one of appendices 1 to 7, wherein the head interval measurement unit performs head interval measurement at a plurality of track positions on the magnetic disk.
(Appendix 9)
9. The magnetic disk drive system according to claim 8, wherein the head interval measuring means performs a process of interpolating a head interval relating to a track position that is not measured based on the plurality of head intervals having different track positions. .
(Appendix 10)
The magnetic disk drive system according to appendix 9, wherein the interpolation processing is performed by an nth order polynomial.
(Appendix 11)
11. The magnetic disk drive system according to any one of appendices 1 to 10, wherein the head interval measuring unit performs head interval measurement when the system power is turned on.
(Appendix 12)
The control unit reads the head interval stored in the storage unit when writing the data, and determines a corrected writing start timing based on the head interval. The magnetic disk drive system according to item.
(Appendix 13)
The head interval measurement means instructs the write head to write measurement information when the magnetic head is on-tracked on a measurement track, and then moves the magnetic head from the on-track position to the radius of the disk. When the information is read from the offset position by reading the measurement information with the read head while subtracting the predetermined offset amount for each rotation of the magnetic disk from the offset position. The magnetic disk drive system according to any one of appendices 1 to 3, wherein the head interval in the radial direction of the magnetic disk is measured based on the offset amount.
(Appendix 14)
The head interval measuring means offsets the magnetic head from the on-side or the outer side by the predetermined offset amount with respect to the on-track position, and performs the head interval measurement from both sides. 14. The magnetic disk drive system according to 13.
(Appendix 15)
15. The magnetic disk drive system according to appendix 13 or 14, wherein the head interval measuring means performs the head interval measurement at a plurality of track positions on the magnetic disk.
(Appendix 16)
16. The magnetic disk drive system according to appendix 15, wherein the head interval measuring means interpolates a head interval related to an unmeasured track position based on the plurality of head intervals having different track positions.
(Appendix 17)
17. The magnetic disk drive system according to appendix 16, wherein the head interval measuring means generates an nth order polynomial related to the head interval with respect to the track position based on the plurality of head intervals.
(Appendix 18)
The head interval measuring means stores the order coefficient in the n-th order polynomial in the storage means, and the control means at a track position to be on-tracked based on the order coefficient when performing a read operation with the read head. 18. The magnetic disk drive system according to appendix 17, wherein a head interval is obtained and read seek is performed by adding an offset amount based on the head interval to the track position.
(Appendix 19)
The magnetic disk drive system according to any one of appendices 13 to 18, wherein the head interval measuring means performs head interval measurement when the system power is turned on.
(Appendix 20)
The control means reads the head interval information corresponding to the predetermined track position from the storage means when writing the specific information to the predetermined track position by the write head, generates correction information based on the head interval information, 14. The magnetic disk according to appendix 13, wherein the specific information is written by the write head at a position shifted from the predetermined track position by the correction information amount after the magnetic head is on-track to the predetermined track position. Drive system.
(Appendix 21)
The magnetic disk drive system according to appendix 19, wherein the correction information is obtained by a signed calculation based on the head interval and the initial offset stored in the storage means.
(Appendix 22)
The magnetic disk drive system according to appendix 19 or 20, wherein the specific information includes device-specific information and is written in a specific sector on the magnetic disk.
(Appendix 23)
The control means reads the initial offset value stored in the storage means when reading the specific information by the read head, and then on-tracks the magnetic head to the predetermined track, 22. The magnetic disk drive system according to appendix 20 or 21, wherein the specific information is read by a read head in the previous period after being shifted by the initial offset value.

It is a time chart explaining the operation | movement which writes the medium information for a measurement in a specific track. It is a time chart explaining the operation | movement which reads the medium information for a measurement written in the specific track. It is a time chart explaining the method of calculating a W / R head space | interval from the read medium information for a measurement. It is a time chart explaining another method for calculating the W / R head interval from the read medium information for measurement. It is a flowchart explaining the operation | movement which reads the W / R head space | interval written in the specific sector. It is a flowchart explaining the operation | movement which reads the W / R head space | interval stored in the non-volatile memory. It is a flowchart explaining the operation | movement which determines data write timing based on the read W / R head space | interval. 7 is a graph showing how the amount of core deviation in the disk radial direction between the write head core center and the read head core center changes according to the track position. FIG. 9 is a graph showing a correction error in a disk radial direction when linear correction is performed at five points with respect to a change in the amount of core deviation shown in FIG. 8. FIG. 9 is a graph showing a correction error in a disk radial direction when a fourth-order polynomial correction is performed by five-point measurement with respect to a change in the amount of core deviation shown in FIG. 8. It is a flowchart which shows the procedure of the operation | movement process which measures the off-track margin of a magnetic head. 12 is a flowchart illustrating a procedure of an operation process for measuring an off-track margin subsequent to FIG. 11. It is a flowchart explaining the processing flow of correction value calculation in the case of the 4th-order polynomial correction by five-point measurement. It is a flowchart explaining the processing flow at the time of power activation in the case of using 4th-order polynomial correction by 5-point measurement. It is a flowchart explaining the processing flow at the time of read command reception in the case of using 4th-order polynomial correction by 5-point measurement. It is a flowchart explaining the operation | movement process of offset re-reading by the magnetic head at the time of power activation. It is a figure explaining the operation state of offset re-read by a magnetic head. It is a figure explaining the state where offset re-read cannot be performed when the core width of a magnetic head is small. It is a figure explaining the state where offset re-read was completed when the core width of a magnetic head was small and the amount of offset was made small. It is a figure explaining the write-in and read-out operation according to the magnetic head position control system with respect to the magnetic disc by this embodiment. FIG. 21 is a flowchart illustrating an operation process for writing device-specific information in accordance with the magnetic head position control method shown in FIG. 20. FIG. FIG. 21 is a flowchart for explaining an operation process for reading device-specific information when the power is turned on according to the magnetic head position control method shown in FIG. 20. FIG. It is a figure which shows the schematic block structure of the conventional magnetic disk apparatus. It is a figure which shows the arrangement configuration of a magnetic head. It is a figure which shows the arrangement configuration of a magnetic disk and a magnetic head. It is a figure explaining the change of the magnetic head space | interval corresponding to the track position on a magnetic disc. It is a figure which shows the example of a format of the medium information recorded on a magnetic disc.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Magnetic disk apparatus 2 Disk enclosure unit 21 Magnetic disk 22 Magnetic head 23 Head arm 24 Spindle motor 25 Voice coil motor 26 Head IC
3 Printed circuit board unit 31 MCU
32 Hard disk controller 33 Read / write channel section 34 Servo controller 35 ROM
36 Data buffer memory 4 Host system H _r read head H _w write head

Claims (5)

A magnetic head capable of moving in the radial direction of a disk on a rotating magnetic disk has a write head and a read head juxtaposed at a distance, and data can be written to or read from the magnetic disk. A magnetic disk drive system capable of
When the magnetic head is on-tracked to the measurement track, the write head is instructed to write measurement write information at a predetermined write start timing, and then the magnetic head is moved from the on-track position to the disk. The reading information is read by the reading head while the reading head is offset by a predetermined offset amount in the radial direction and the predetermined offset amount is subtracted every rotation of the magnetic disk from the offset position. A head interval measuring means for measuring a head interval in the radial direction of the magnetic disk based on the offset amount when it is made;
Storage means for storing the measured head interval information;
And a control unit that corrects the operation of the magnetic head based on the head interval information read from the storage unit.   2. The magnetic disk drive system according to claim 1, wherein the head interval measurement unit performs the head interval measurement at a plurality of track positions on the magnetic disk.   3. The magnetic disk drive system according to claim 2, wherein the head interval measuring means generates an nth order polynomial related to the head interval with respect to the track position based on the plurality of head intervals. The head interval measuring means stores the order coefficient in the n-th order polynomial in the storage means,
When the control means performs a read operation with the read head, a head interval at an on-track position is obtained based on the order coefficient, and an offset amount based on the head interval is added to the track position to obtain a read seek. The magnetic disk drive system according to claim 3, wherein:   The control means reads the head interval information corresponding to the predetermined track position from the storage means when writing the specific information to the predetermined track position by the write head, generates correction information based on the head interval information, 2. The magnetic information according to claim 1, wherein after the on-track of the magnetic head to the predetermined track position, the specific information is written by the write head at a position shifted from the predetermined track position by the correction information amount. Disk drive system.

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