Magnetic disk device

Abstract

The present disclosure provides a magnetic disk device capable of performing appropriate servo control. According to one embodiment, a magnetic disk device includes a magnetic head and a magnetic disk. In the magnetic disk, a plurality of servo regions, in which servo data including a plurality of data pieces are written, are arranged in the circumferential direction, respectively, and are arranged at equal intervals in the circumferential direction. At a plurality of continuous first radius positions, recording frequencies of the servo data differ for each of the first radius positions. In each of the plurality of servo regions, a first data piece among the plurality of data pieces is written to a first circumferential position at which the movement time of the magnetic head in the circumferential direction with reference to the timing at which the magnetic head passes through a reference position on the circumference coincides between the plurality of first radius positions.

Description

[0001] This application enjoys priority based on Japanese Patent Application No. 2024-157697 (filed on September 11, 2024). This application incorporates the entire contents of the basic application by reference to that basic application. Technical Field

[0002] Embodiments of the present invention relate to disk drives. Background Technology

[0003] Previously, servo data was written at a constant recording frequency regardless of the disk's radial position, or at a constant recording frequency in each of the multiple regions obtained by dividing the disk radially. In contrast, in recent years, the CDS (Constant Density Servo) method has been developed as a servo data recording method. According to the CDS method, the recording frequency varies gradually relative to the radial direction, with a higher recording frequency on the outer diameter side than on the inner diameter side. Therefore, compared to previous servo data recording methods, the area where servo data is written is reduced, while the area where user data can be written is increased.

[0004] However, from the perspective of servo control, there is room for improvement in the CDS method. Summary of the Invention

[0005] Embodiments of the present invention provide a disk device capable of performing appropriate servo control.

[0006] According to this embodiment, the disk drive includes a read / write head and a disk. On the disk, multiple servo regions, each containing multiple data slices, are arranged at equal intervals in the circumferential direction and are written with servo data in each circumferential direction. At a plurality of consecutive first radius positions, the recording frequency of the servo data varies according to each first radius position. In each of the plurality of servo regions, a first data slice of the plurality of data slices is written at a first circumferential position where the circumferential movement time of the read / write head, based on the timing of the read / write head passing a reference position on the circumference, is consistent among the plurality of first radius positions. Attached Figure Description

[0007] Figure 1 This is a diagram illustrating an example of the configuration of the disk drive according to the first embodiment.

[0008] Figure 2 This is a diagram illustrating an example of the configuration of the disk according to the first embodiment.

[0009] Figure 3 This is a diagram illustrating an example of the configuration of the servo data involved in the first embodiment.

[0010] Figure 4 This is a diagram showing an example of the reference position set by the disk in the first embodiment.

[0011] Figure 5 This is a diagram illustrating an example of the relationship between the radius position and the recording frequency of servo data according to the first embodiment.

[0012] Figure 6 This is a diagram used to illustrate the method for writing servo data according to the first embodiment.

[0013] Figure 7 This is a diagram illustrating an example of the method for writing servo data according to the second embodiment.

[0014] Figure 8 This is a diagram illustrating an example of the pulse train pattern writing method according to the third embodiment.

[0015] Figure 9 This is a diagram illustrating another example of the pulse train pattern writing method according to the third embodiment.

[0016] Figure 10 This is a diagram illustrating yet another example of the pulse train pattern writing method according to the third embodiment.

[0017] Figure 11 This is a diagram illustrating an example of the method for writing servo data according to the fourth embodiment.

[0018] Figure 12 This is a diagram illustrating another example of the shape of the servo region involved in the fifth embodiment.

[0019] Figure 13 This is a diagram illustrating an example of the method for writing servo data according to the fifth embodiment.

[0020] Figure 14 This is a diagram illustrating another example of the servo data writing method according to the fifth embodiment.

[0021] Figure 15 This is a diagram illustrating yet another example of the method for writing servo data according to the fifth embodiment.

[0022] Figure 16 This is a diagram illustrating yet another example of the method for writing servo data according to the fifth embodiment.

[0023] Figure 17 This is a diagram illustrating an example of the servo data writing method according to the sixth embodiment.

[0024] Figure 18This is a flowchart illustrating an example of the Sync Search operation according to the sixth embodiment.

[0025] Figure 19 This is a diagram illustrating an example of the length in the radial direction of the frequency-constant region involved in the sixth embodiment.

[0026] Figure 20 This is a diagram illustrating another example of the servo data writing method according to the sixth embodiment.

[0027] Figure 21 This is a diagram used to illustrate the timing of writing servo data in the comparative example.

[0028] Explanation of reference numerals in the attached figures

[0029] 1 Disk device, 2 Host, 11 Disk, 12 SPM, 13 Ramp, 15 Actuator arm, 16 VCM, 21 SVC, 22 Head, 22r Read head, 22w Write head, 23 HDC, 24 Preamplifier, 25 RWC, 26 Processor, 28 FROM, 29 DRAM, 41 Tracks, 50, 50a, 50b, 50c, 60, 60a, 60b, 60c, 70, 70a, 70b Areas, SV Servo Area. Detailed Implementation

[0030] Hereinafter, the disk device according to the embodiments will be described in detail with reference to the accompanying drawings. However, the invention is not limited by these embodiments.

[0031] (First Embodiment)

[0032] Figure 1 This is a diagram showing an example of the configuration of the disk device 1 according to the first embodiment.

[0033] Disk device 1 is connected to host 2. Disk device 1 can receive access commands such as write commands or read commands from host 2.

[0034] The disk device 1 includes a disk 11 with a magnetic layer formed on its surface. The disk device 1 performs access to the disk 11 according to access commands. The access includes writing data and reading data.

[0035] Data writing and reading are performed by the read / write head 22. Specifically, in addition to the disk 11, the disk device 1 also includes a spindle motor (SPM) 12, a ramp 13, an actuator arm 15, a voice coil motor (VCM) 16, a servo controller (SVC) 21, a read / write head 22, a hard disk controller (HDC) 23, a preamplifier 24, a read / write channel (RWC) 25, a processor 26, a FROM (Flash Read Only Memory) 28, and a DRAM (Dynamic Random Access Memory) 29.

[0036] The disk 11 rotates at a predetermined speed via the coaxially mounted SPM12.

[0037] SVC21 is an integrated circuit that functions as a driver for SPM12 and VCM16. Processor 26 controls the rotation of SPM12 and VCM16 via SVC21.

[0038] The read / write head 22 has a write head 22w and a read head 22r. The read / write head 22 writes data to the disk 11 using the write head 22w. The read / write head 22 reads data from the disk 11 using the read head 22r. The read / write head 22 is mounted at the front end of the actuator arm 15. The read / write head 22 moves in the radial direction of the disk 11 via the VCM 16 driven by the SVC 21. Furthermore, either or both of the write head 22w and read head 22r may be provided for a single read / write head 22, and multiple copies may be provided for each head 22.

[0039] When the disk 11 stops rotating, the read / write head 22 moves onto the ramp 13. The ramp 13 holds the read / write head 22 in a position separated from the disk 11.

[0040] The preamplifier 24 is an integrated circuit that performs data writing and reading via the read / write head 22. During a read operation, the preamplifier 24 amplifies and outputs the signal read from the disk 11 by the read / write head 22, supplying it to the read / write head 25. During a write operation, the preamplifier 24 amplifies the signal corresponding to the data to be written supplied from the read / write head 25, supplying it to the read / write head 22.

[0041] DRAM29 is used as a buffer for data transfer between the host 2 and the host 2. For example, DRAM29 is used to temporarily store data to be written or data read from disk 11.

[0042] In addition, DRAM29 is used by processor 26 as operating memory. DRAM29 is used as an area for loading firmware programs and temporarily storing various management data.

[0043] HDC23 controls the data transfer between the HDC23 and the host 2 via the I / F bus. HDC23 supplies write data received from the host 2 to RWC25 via DRAM29. HDC23 receives read data output from RWC25 via DRAM29 and sends the read data to the host 2.

[0044] RWC25 modulates the data of the write object supplied from HDC23 and supplies it to preamplifier 24. In addition, RWC25 performs demodulation including error correction on the signal read from disk 11 and supplied from preamplifier 24, and then outputs the signal as digital data to HDC23.

[0045] Processor 26 is, for example, a CPU (Central Processing Unit). FROM 28 and DRAM 29 are connected to processor 26.

[0046] The firmware program and various settings information are stored in FROM28. Alternatively, the firmware program can also be saved to disk 11.

[0047] The processor 26 performs overall control of the disk device 1 according to the firmware program stored in the FROM 28 or the disk 11. For example, the processor 26 loads the firmware program from the FROM 28 or the disk 11 into the DRAM 29, and executes the control of the SVC 21, the preamplifier 24, the RWC 25, the HDC 23, etc. according to the firmware program loaded into the DRAM 29.

[0048] In addition, some or all of the functions of the processor 26 can also be implemented by hardware circuits such as FPGA (Field-Programmable Gate Array) or ASIC (Application Specific Integrated Circuit).

[0049] HDC23, RWC25, and processor 26 constitute a System-On-a-Chip (SoC) 30 as an integrated circuit. In addition to these elements, SoC 30 may also include other elements (such as FROM 28 or DRAM 29).

[0050] Figure 2This is a diagram illustrating an example of the configuration of the disk 11 according to the first embodiment. Furthermore, this diagram shows an example of the rotation direction of the disk 11. The read / write head 22 moves relative to the disk 11 due to its rotation. Therefore, the write / read direction, that is, the direction in which data is written or read by the read / write head 22 along the circumferential direction, is the opposite direction to the rotation direction of the disk 11.

[0051] In the radial direction, the direction from the edge of disk 11 toward the center is the ID direction, and the direction from the center of disk 11 toward the edge is the OD direction.

[0052] During the manufacturing process, servo data for positioning the read / write head 22 is written to the disk 11, for example, via a servo writer or self-servo write (SSW). Figure 2 As an example of a configuration of servo regions where servo data is written, multiple servo regions SV are formed, arranged radially and at equal intervals in the circumferential direction. A data region DA is used between two consecutive servo regions SV in the circumferential direction for writing data.

[0053] Multiple concentric servo tracks 41 are arranged in the radial direction of the disk 11. Furthermore, multiple concentric data tracks are arranged in the area of ​​the disk 11 where the multiple servo tracks 41 are arranged. Multiple data sectors are arranged continuously in the circumferential direction within the area divided by the data region DA on each data track. Data can be written to each data sector. The data that can be written to each data sector includes user data received from the host 2, metadata (e.g., error correction codes) attached to the user data, system data, etc. The disk device 1 has a pre-set positional relationship between the multiple servo tracks 41 and the multiple data tracks. Based on the servo data written to the servo region SV, positioning control is performed to position the read / write head 22 on the target data track. Positioning control includes actions such as moving the read / write head 22 radially toward the target data track (seek action) and tracking actions to keep the read / write head 22 on the target data track.

[0054] Furthermore, the multiple servo tracks 41 can also be used as multiple data tracks. For simplicity, in the following description, the multiple servo tracks 41 will be referred to as multiple data tracks. The servo tracks 41 will be simply referred to as tracks 41. The servo region SV, defined by each track 41, is also called a servo sector.

[0055] The position along the radius is denoted as the radius position. The position along the circumference is denoted as the circumference position.

[0056] Figure 3 This is a diagram illustrating an example of the configuration of servo data according to the first embodiment.

[0057] Here, the expression of positional relationships is defined. In cases where there are two adjacent regions, a first region and a second region, along the write / read direction, and the read / write head 22 passes through the first region immediately before the second region, the second region is sometimes described as the region "after" the first region, and the first region as the region "before" the second region. Additionally, in the circumferential direction, the position in a region where the read / write head 22 first passes is sometimes referred to as the "beginning" of that region. Sometimes, the portion of data written to a region that begins in that region is referred to as the "beginning" of that data.

[0058] like Figure 3 As shown, the servo data contains multiple servo data slices. These servo data slices are preamble (PR), synchronization marker (SN), Gray code (GC), burst pattern (BP1), and burst pattern (BP2). In the servo region SV, the preamble (PR), synchronization marker (SN), Gray code (GC), burst pattern (BP1), and burst pattern (BP2) are arranged in this order in the write / read direction.

[0059] The preamble PR is a single-cycle pattern data that changes periodically in the circumferential direction. The frequency of the pattern data in the preamble PR corresponds to the recording frequency of the servo data. When the servo waveform read by the read head 22r is input into the RWC25 as sample data based on the servo clock, the preamble PR is used to adjust the amplitude, phase, and frequency of the sampled data. The servo clock generates the RWC25. In other words, the preamble PR is used to ensure that the servo clock corresponds to the recording frequency of the servo data.

[0060] The synchronization marker SN is patterned data used to determine the timing of servo data reads. The SoC30 determines the read timing of various servo data slices based on the detection timing of the synchronization marker SN and the count value of its own counter (not shown).

[0061] Gray code GC contains cylinder addresses for identifying each track 41 set on disk 11 and sector addresses for identifying servo sectors on track 41.

[0062] Pulse train patterns BP1 and BP2 are pattern data used to detect the amount of offset of the position of the read / write head 22 from the center of a certain servo track 41 (more precisely, track 41 represented by the cylinder address).

[0063] Each pulse train pattern is sampled into the RWC25 at servo clock-based sampling intervals. The RWC25 processes the waveforms of each sampled pulse train pattern, for example, by performing a Discrete Fourier Transform (DFT), thereby obtaining the phase and amplitude. Based on the phase and amplitude obtained by the RWC25, the SoC30 calculates the deviation of the head 22 from the center of track 41. The SoC30 (e.g., processor 26) estimates the radius position of the head 22 based on the cylinder address obtained from the Gray code GC and the deviation obtained from each pulse train pattern.

[0064] In addition, servo data can include any type of servo data slice. For example, servo data can also include a postcode representing a correction amount based on the position offset according to RRO (Repeatable Run Out).

[0065] On disk 11, a reference position is set at a point on the circumference. Multiple servo sectors arranged at equal intervals in the circumferential direction are assigned sector addresses with ascending numerical information based on the reference position.

[0066] Furthermore, a servo sector is the area demarcated from the servo region SV by track 41. Therefore, the servo addresses of all servo sectors contained within a servo region SV are shared. Hereinafter, the servo region SV consisting of servo sectors with sector address i will sometimes be denoted as servo region SV#i.

[0067] Figure 4 This is a diagram showing an example of a reference position set on the disk 11 according to the first embodiment.

[0068] exist Figure 4 In the example shown, a reference position line is set that extends straight along the radial direction. However, the shape of the reference position line does not necessarily have to be a straight line. For example, the reference position line can also have a curved shape depending on the path through which the magnetic head 22 moves via VCM16.

[0069] In the first embodiment, the servo data is recorded in a CDS (Cardboard Data Set) manner. According to the CDS method, such as... Figure 5 As shown, the recording frequency of servo data changes smoothly relative to the radial direction in such a way that the recording frequency of servo data increases on the outer peripheral side compared to the inner peripheral side.

[0070] As described above, the disk 11 is rotated at a constant speed. Therefore, the closer to the outer perimeter, the faster the relative movement speed of the read / write head 22 in the circumferential direction relative to the disk 11. Thus, assuming the recording frequency is constant in the radial direction, the closer to the outer perimeter, the longer the circumferential length of the servo sector.

[0071] In contrast, according to the ODS method, since the recording density of servo data is higher on the outer periphery compared to the inner periphery, it is possible to suppress the tendency for the servo sector to become longer in the circumferential direction closer to the outer periphery. Therefore, for example, like... Figure 2 As shown, the circumferential width of each servo region SV can be kept constant regardless of the radius position. Therefore, compared to the case where the recording frequency is constant in the radial direction, the area where user data can be recorded, i.e., the data region DA, is increased.

[0072] In addition, Figure 2 In the example shown, each servo region SV has a shape that extends straight from the inner periphery to the outer periphery. The shape of each servo region SV is not limited to this. Each servo region SV may also have a curved shape.

[0073] The techniques compared with the implementation method will be described. These techniques compared with the implementation method will be referred to as comparative examples. According to the comparative examples, servo data is written using the ODS method. The timing of writing the servo data is determined by counting a servo clock (or its divided clock) that is adjusted to a frequency corresponding to the recording frequency. Regardless of the radial position, servo data is recorded at a timing when the count value of the servo clock (or its divided clock) reaches a common value. This forms servo regions SV extending in the radial direction.

[0074] Figure 21 This is a diagram used to illustrate the write timing of servo data involved in the comparative example. In this diagram, the vertical axis represents the radius position, and the horizontal axis represents the time axis. In this specification, the time axis represents the elapsed time from when the read / write head passes the reference position. Furthermore, this diagram shows the write timing of servo data for a certain servo region SV at three radius positions.

[0075] The ODS method is used in the comparative example. Therefore, as... Figure 21 As shown, the closer to the outer perimeter, the shorter the length of the servo region SV on the time axis.

[0076] Furthermore, in the comparative example, regardless of the radius position, servo data is written to a servo region SV at a timing when the count value of the servo clock (or its divided clock) reaches a common value. Since the servo clock frequency is higher closer to the outer perimeter, therefore, as... Figure 21 As shown, the closer to the outer perimeter, the earlier the servo data is recorded.

[0077] Servo data reading is controlled by a servo strobe signal. The servo strobe signal indicates whether servo data reading is permitted. When the servo strobe signal is enabled, servo data reading is permitted. When the servo strobe signal is disabled, servo data reading is not permitted.

[0078] When the read / write head moves to the next region after passing through a certain servo region SV, the SoC determines the timing of servo strobe signal to enable servo data reading for the next servo region SV based on the time when the synchronization mark SN is detected in the servo region SV that the read / write head has passed through.

[0079] exist Figure 21 In the comparative example shown, the location where servo data is written on the time axis varies for each radius. Therefore, when moving the read / write head radially, the SoC needs to consider both the radius position of the head as it passes through a certain servo region SV and the radius position as it reaches the next servo region SV to determine the timing for activating the servo strobe signal. In other words, determining the timing for activating the servo strobe signal involves complex computations.

[0080] In the first embodiment, effort was put into determining the timing of enabling the servo strobe signal. The location of the servo data was carefully considered.

[0081] Figure 6 This is a diagram illustrating the method for writing servo data according to the first embodiment. In this diagram, the vertical axis represents the radial position, and the horizontal axis represents the time axis. Furthermore, the time axis represents the elapsed time from when the read / write head 22 passes the reference position. That is, the time axis can be considered as the circumferential movement time of the read / write head 22 based on the timing of its passage through the reference position. The movement time is the time during which the read / write head 22 moves relative to the disk 11. Hereinafter, the circumferential movement time of the read / write head 22 based on the timing of its passage through the reference position will sometimes be simply referred to as the position in time.

[0082] This figure shows the write timing of servo data for servo regions SV#i and servo region SV#(i+1) at three radius positions. Here, the three radius positions are the radius positions of track #N, track #(N+a), and track #(N+b), starting from the outer perimeter.

[0083] In the first embodiment, within the same servo region SV, the timing of writing the preamble PR is aligned across all radii. In other words, the preamble PR is written at a circumferential position where the movement time of the head 22 in the circumferential direction, based on the timing of the head 22 passing through a reference position on the circumference, is aligned across all radii. Thus, as... Figure 6 As shown, the radius positions of track #N, track #(N+a), and track #(N+b) are consistent in terms of the timing of writing the preamble PR.

[0084] By writing servo data as described above, the calculations required to determine the timing for enabling the servo strobe signal become easier compared to the comparative example.

[0085] As an example, consider the case where the read / write head 22 moves along track #N and passes through the servo region SV#i. In this case, if the SoC 30 activates the servo strobe signal SG after a time t1 elapsed since the synchronization marker SN was detected in the servo region SV#i, then regardless of the track 41 to which the read / write head 22 is headed, it can read the servo data written to the servo region SV#(i+1) from the beginning.

[0086] As another example, consider the case where the read / write head 22 moves along track #(N+a) through the servo region SV#i. In this case, if the SoC 30 activates the servo strobe signal SG after time t2 has elapsed since the synchronization marker SN was detected in the servo region SV#i, then regardless of the track 41 to which the read / write head 22 is headed, it can read the servo data written to the servo region SV#(i+1) from the beginning.

[0087] In this way, regardless of the radius of the moving destination, the SoC30 can determine the timing for activating the servo strobe signal based on the detected radius of the synchronization marker SN. In other words, the computation required to determine the timing for activating the servo strobe signal SG becomes easier compared to the comparative example.

[0088] (Second Implementation)

[0089] When the rotational speed of disk 11 changes, the detection time interval of the synchronization mark SN changes. SoC 30 sometimes has the following function: when the detection time of the synchronization mark SN deviates from the ideal detection time, the frequency of the servo clock is corrected based on the deviation of the detection time of the synchronization mark SN. This function is referred to as the rotational variation tracking function. The ideal detection time is the detection time of the synchronization mark SN when disk 11 rotates at a set rotational speed. According to the rotational variation tracking function, the frequency of the servo clock can follow the rotational variation of disk 11.

[0090] According to the comparative example, the detection time of the synchronization mark SN deviates based on the radial position. Therefore, even if the disk rotation speed remains constant, the interval of the synchronization mark SN detection time will vary depending on the radial movement of the read / write head. Thus, it is conceivable that with the aforementioned rotational variation tracking function installed, even if the disk rotation speed remains constant, unexpected servo clock corrections will occur, leading to servo control malfunctions. For example, it may be difficult to activate the servo strobe signal at the correct timing.

[0091] In the second embodiment, efforts are made to control the writing position of the servo data so that if there is no change in the rotation speed of the disk 11, the detection time interval of the synchronization mark SN will not change regardless of the radius position.

[0092] Figure 7 This is a diagram illustrating an example of the servo data writing method according to the second embodiment. In this diagram, the vertical axis represents the radius position, and the horizontal axis represents the time axis.

[0093] like Figure 7 As shown, within the same servo region SV, the position of the time-written synchronization mark SN is consistent across all radius positions. With this configuration, the detection interval of the synchronization mark SN is designed to be constant at time t3 regardless of the radius position. Therefore, even as the read / write head 22 moves in the radial direction, as long as the rotational speed of the disk 11 remains constant, the synchronization mark SN is detected at intervals of time t3. On the other hand, when the rotational speed of the disk 11 changes, the detection interval of the synchronization mark SN shifts from time t3.

[0094] In this way, even when the rotational variation tracking function is installed, it is possible to prevent unintended servo clock corrections.

[0095] (Third Implementation)

[0096] According to the comparative example, the temporal position corresponding to the circumferential position of the written pulse train pattern (pulse train patterns BP1, BP2) varies depending on the radius position. Consequently, the normal timing for demodulating the pulse train pattern is offset between adjacent tracks. Therefore, when the read / write head is positioned across the boundary of two tracks, a phase error occurs in the demodulation result of the pulse train pattern due to the offset in the normal timing for demodulating the pulse train pattern. When a phase pulse train is used as the pulse train pattern, this phase error leads to a deterioration in the accuracy of positioning control.

[0097] In the third embodiment, efforts are made to control the writing position of the pulse train pattern in order to suppress the control error of the pulse train gating and the phase error of the demodulation result of the pulse train pattern.

[0098] Figure 8 This is a diagram illustrating an example of the pulse train pattern writing method according to the third embodiment. In this diagram, the vertical axis represents the radius position, and the horizontal axis represents the time axis.

[0099] like Figure 8As shown, the time positions of the pulse train patterns BP1 and BP2 are consistent across all radius positions. Therefore, the timing offset of the normal pulse train pattern demodulation is significantly suppressed. Consequently, the degradation of positioning control accuracy can be significantly suppressed.

[0100] Furthermore, according to the SoC30 specifications, it is sometimes difficult to adjust the write timing of the pulse train pattern with fine steps. In such cases, for example, it is also possible to... Figure 9 As shown, only the initial pulse train patterns in pulse train patterns BP1 and BP2, i.e., the position of pulse train pattern BP1 in time when it is written, are consistent across all radius positions. This suppresses the timing offset of the normal demodulation of the pulse train patterns. As a result, it is possible to suppress the deterioration of positioning control accuracy.

[0101] Furthermore, when only the timing of the initial pulse train pattern is consistent across the radial positions, the farther the pulse train pattern is from the initial pulse train pattern in the circumferential direction, the greater the offset in the normal timing of demodulating the pulse train pattern. Consequently, it may be less effective in suppressing the deterioration of positioning control accuracy. Therefore, it is also possible to... Figure 10 As shown, only the pulse train patterns other than the initial pulse train patterns in pulse train patterns BP1 and BP2, i.e., the pulse train pattern BP2, are written at the same time position across all radius positions.

[0102] (Fourth implementation)

[0103] In the first embodiment, the preamble PR, in the second embodiment, the synchronization marker SN, and in the third embodiment, the pulse train pattern are written at each radius position to a circular position that is consistent in time among all radius positions. Alternatively, any two of the preamble PR, synchronization marker SN, and pulse train pattern can be written to a circular position that is consistent in time among all radius positions.

[0104] Figure 11 This is a diagram illustrating an example of the servo data writing method according to the fourth embodiment. In this diagram, the vertical axis represents the radius position, and the horizontal axis represents the time axis.

[0105] exist Figure 11 In the example shown, within the same servo region SV, the timing of writing the preamble PR is consistent across all radius positions, and the timing of writing the synchronization marker SN is consistent across all radius positions.

[0106] With this configuration, if the SoC 30 activates the servo strobe signal SG after a time t5 has elapsed since the synchronization marker SN was detected, it can read and write servo data from the beginning to the next servo region SV regardless of the radius position of the read / write head 22 or the radius position of the detected synchronization marker SN. This further simplifies the computation required to determine the timing of activating the servo strobe signal SG.

[0107] Furthermore, similar to the second embodiment, the detection time interval of the synchronization mark SN is designed to be constant regardless of the radius position (here, constant is time t4). Thus, even when the rotation variation tracking function is installed, it is possible to prevent unintended correction of the servo clock.

[0108] Furthermore, the timing of writing the preamble PR is consistent across all radius positions, as is the timing of writing the synchronization flag SN. Therefore, the number of waveforms in one cycle contained in the preamble PR can vary depending on the radius position. Specifically, the closer to the outer perimeter, the more waveforms in one cycle the preamble PR will contain.

[0109] (Fifth Embodiment)

[0110] Figure 12 This figure shows another example of the shape of the servo region SV according to the fifth embodiment. In the example shown in this figure, the recording surface of the disk 11 is divided into two regions 50a and 50b arranged in the radial direction. Furthermore, in each of the two regions 50a and 50b, each servo region SV extends straight from the inner peripheral side to the outer peripheral side. However, at the boundary between region 50a and region 50b, each servo region SV is discontinuous.

[0111] For example, the following phenomenon may occur when writing servo data via SSW. In SSW, SoC30 writes servo data from the inner periphery to a certain radius position, and from the outer periphery to that radius position. As a result, the recording surface of disk 11 is divided into two regions 50a and 50b at that radius position.

[0112] Furthermore, the direction in which servo data is written to regions 50a and 50b is not limited to this. Additionally, the recording surface of disk 11 can be divided into three or more regions 50 arranged radially, and the servo regions SV at the boundaries of each region can be discontinuous. Furthermore, corresponding to the discontinuous servo region SV, the reference position can also be discontinuous.

[0113] When the recording surface of the disk 11 is divided into multiple regions 50 arranged in the radial direction, any one of the first, second, third and fourth embodiments can be applied to each region 50.

[0114] Figure 13 This is a diagram illustrating an example of the servo data writing method according to the fifth embodiment. In this diagram, the vertical axis represents the radius position, and the horizontal axis represents the time axis.

[0115] exist Figure 13 In the example of multiple regions 50, the write timing of servo data in regions 50a, 50b, and 50c is shown. As consecutive radius positions constituting region 50a, starting from the outer perimeter, the radius positions of track #(P-1), track #P, and track #(P+1) are shown. As consecutive radius positions constituting region 50b, starting from the outer perimeter, the radius positions of track #(Q-1), track #Q, and track #(Q+1) are shown. As consecutive radius positions constituting region 50c, starting from the outer perimeter, the radius positions of track #(R-1), track #R, and track #(R+1) are shown.

[0116] exist Figure 13 In the example shown, servo data is written in each of regions 50a, 50b, and 50c using the same method as in the first embodiment. That is, the timing of writing the preamble PR is consistent across all radius positions within region 50a, region 50b, and region 50c. With this configuration, the same effect as in the first embodiment can be obtained in each of regions 50a, 50b, and 50c.

[0117] Figure 14 This is a diagram illustrating another example of the servo data writing method according to the fifth embodiment. Furthermore, regarding... Figure 14 The example shown is for... Figure 13 Different matters will be explained.

[0118] exist Figure 14In the example shown, servo data is written in each of regions 50a, 50b, and 50c using the same method as in the second embodiment. That is, the timing of writing the synchronization marker SN is consistent across all radius positions within region 50a, region 50b, and region 50c. With this configuration, the same effect as in the second embodiment can be obtained in each of regions 50a, 50b, and 50c.

[0119] Figure 15 This is a diagram illustrating yet another example of the servo data writing method according to the fifth embodiment. Furthermore, regarding... Figure 15 The example shown is for... Figure 13 Different matters will be explained.

[0120] exist Figure 15 In the example shown, servo data is written in each of regions 50a, 50b, and 50c using the same method as in the fourth embodiment. That is, the timing of writing the preamble PR is consistent across all radius positions within region 50a. Furthermore, the timing of writing the synchronization flag SN is consistent across all radius positions within region 50a. Similarly, the timing of writing the preamble PR is consistent across all radius positions within region 50b. The timing of writing the synchronization flag SN is consistent across all radius positions within region 50c. With this configuration, the same effect as in the fourth embodiment can be obtained in each of regions 50a, 50b, and 50c.

[0121] Figure 16 This is a diagram illustrating yet another example of the servo data writing method according to the fifth embodiment. Furthermore, regarding... Figure 16 The example shown is for... Figure 13 Different matters will be explained.

[0122] exist Figure 16 In the example shown, servo data was written in each of regions 50a, 50b, and 50c using the same method as in the fourth embodiment. However, the timing of writing the synchronization marker SN was consistent across all radii within regions 50a, 50b, and 50c.

[0123] With this configuration, the detection interval of the synchronization mark SN is designed to be constant regardless of the radius position within regions 50a, 50b, and 50c. Therefore, even as the read / write head 22 moves radially within regions 50a, 50b, and 50c, the synchronization mark SN can be detected at the same interval as long as the rotational speed of the disk 11 remains unchanged.

[0124] (Sixth Embodiment)

[0125] In servo control, if the detection of the synchronization marker SN fails, the SoC30 performs a synchronization search operation to find the synchronization marker SN. When the synchronization search operation begins, the SoC30 sets the detection frequency for the RWC25 in order to achieve synchronization with the pattern of the preamble PR.

[0126] According to the comparative example, since the recording frequency varies depending on the radius position, the calculation of the frequency set for the RWC becomes complex when a synchronous search operation begins while the read / write head is moving at high speed in the radial direction. For example, the SoC predicts the radius position from which servo data will be read next based on the reading speed and time of the read / write head in the radial direction. Furthermore, the SoC sets the recording frequency for the predicted radius position on the RWC.

[0127] However, it is difficult to accurately predict the radius of the next servo data read. Therefore, it may be impossible to set the appropriate frequency for the RWC. Failure to set the appropriate frequency for the RWC may lead to malfunctions in seek control.

[0128] According to the sixth embodiment, the disk 11 is divided into multiple regions in the radial direction, including regions where the recording frequency of servo data is constant regardless of the position in the radial direction.

[0129] Figure 17 This is a diagram illustrating an example of the servo data writing method according to the sixth embodiment. In this diagram, the vertical axis represents the radius position, and the horizontal axis represents the time axis.

[0130] exist Figure 17 The diagram shows the write timing of servo data in regions 60a, 70a, 60b, 70b, and 60c. Regions 60a, 70a, 60b, 70b, and 60c are arranged in this order starting from the inner perimeter.

[0131] In regions 60a, 60b, and 60c, the recording frequency is gradually varied relative to the radial direction in a CDS manner, i.e., the recording frequency of servo data is higher on the outer periphery compared to the inner periphery. For regions 60a, 60b, and 60c, either the first, second, third, fourth, or fifth embodiment may be applied, or none of them may be applied.

[0132] Within regions 70a and 70b, the recording frequency of servo data remains constant regardless of the radius position. That is, within each of regions 70a and 70b, the recording frequency of servo data across multiple consecutive radius positions is a common value. However, in Figure 17 In the example shown, the recording frequency of servo data in region 70b is higher than that in region 70a. Each of regions 70a and 70b is designated as a constant frequency region.

[0133] Figure 18 This is a flowchart illustrating an example of the synchronous search operation involved in the sixth embodiment.

[0134] If the detection of the synchronization marker SN fails when the read / write head 22 passes through a certain servo region SV (S101), the SoC 30 begins a synchronization search operation. During the synchronization search operation, the SoC 30 begins counting the time since the position of the read / write head 22 was obtained based on servo data (S102). The time counted in S102 is recorded as the movement time of the read / write head 22 since its position was obtained based on servo data.

[0135] Based on the radial movement speed and movement time of the head 22, SoC30 determines the frequency constant region where the head 22 was most recently arrived (S103).

[0136] For example, if the detection of the synchronous marker SN fails to be detected during the movement of the head 22 along the OD direction in region 60b based on the moving speed and moving time of the head 22 in the radial direction, and the head 22 then reaches region 70b, the SoC 30 determines region 70b as a frequency constant region that was recently reached at the most recent timing.

[0137] Additionally, for example, if the detection of the synchronous marker SN is lost during the movement of the head 22 along the ID direction in region 60b based on the moving speed and moving time of the head 22 in the radial direction, and the head 22 subsequently reaches region 70a, the SoC 30 determines region 70a as a frequency constant region that was reached at the most recent timing.

[0138] SoC30 sets the recording frequency of servo data in the determined constant frequency region to RWC25 (S104). Thus, when the magnetic head 22 passes through the servo region SV in the determined constant frequency region, SoC30 can achieve synchronization with the pattern of the preamble PR of the servo region SV and can detect the synchronization mark SN.

[0139] If the synchronization marker is successfully detected (S105: No), the synchronization search operation ends. If the synchronization marker is successfully detected (S105: Yes), control moves to S103, and the SoC30 determines another constant frequency region.

[0140] In this way, a region 70 is set in each of the inner and outer periphery sides of the region 60 where servo data is recorded in CDS mode, where the recording frequency of servo data remains constant regardless of the radius position. Therefore, the detection frequency can be easily and appropriately set during synchronous search operations.

[0141] In addition, for example, it can also be like Figure 19 As shown, the radial length L of each region 70 is set to satisfy the following equation (1) so that the magnetic head 22 can reliably pass through the frequency-constant region determined by the processing of S103. Furthermore, T SV V is the time interval during which the read / write head 22 passes through the servo region SV. seekmax It is the maximum seek speed, which is the maximum value of the radial movement speed of the read / write head 22.

[0142] L≥T SV *V seekmax …(1)

[0143] In addition, there may be a region 70 where the relationship of equation (1) above is not applied.

[0144] Figure 20 This is a diagram illustrating another example of the servo data writing method according to the sixth embodiment. In this diagram, the vertical axis represents the radius position, and the horizontal axis represents the time axis.

[0145] exist Figure 20 In the example shown, the recording frequency of servo data in region 70a is equal to the recording frequency of servo data in region 70b. It is also possible to apply a common frequency as the servo data recording frequency in two or more regions 70 in this way. Therefore, it is possible to omit... Figure 18 The processing of S103 is shown.

[0146] (Summary)

[0147] According to embodiments 1 to 5, in the disk 11, the recording frequency of servo data is different at multiple consecutive radial positions (denoted as multiple first radial positions). In the example described above, the multiple first radial positions are the radial positions of multiple consecutive tracks 41 in the radial direction. In each servo region SV, a specific type of servo data slice (denoted as first data slice) is written into the servo data at the circumferential position (denoted as first circumferential position) of each first radial position where the circumferential position, i.e., the circumferential position of the head 22 based on the timing of the head 22 passing through the reference position on the circumference, is consistent among the multiple first radial positions.

[0148] In addition, the first data slice is a preamble PR, a synchronization marker SN, or a burst pattern (burst pattern BP1 or burst pattern BP2).

[0149] Since the timing of writing the first data slice is consistent at multiple first radius positions, proper servo control is possible. Specifically, for example, when the first data slice is a preamble (PR), as described in the first embodiment, the calculations required to determine the timing of activating the servo strobe signal become easier. For example, when the first data slice is a synchronization marker (SN), as described in the second embodiment, even when a rotational variation tracking function is installed, unintended servo clock corrections can be prevented. For example, when the first data slice is a pulse train pattern, as described in the third embodiment, the positioning control accuracy can be improved compared to the comparative example.

[0150] Furthermore, according to the fourth embodiment, on the disk 11, a servo data slice of a different type than the first data slice (denoted as the second data slice) is written to a circumferential position (denoted as the second circumferential position) that is consistent in time among a plurality of first radius positions and is different from the first circumferential position.

[0151] exist Figure 11 In the example shown, the first data slice is the preamble PR, and the second data slice is the synchronization marker SN. Furthermore, the number of waveforms in one cycle contained in the preamble PR, which is the first data slice, varies at each first radius position.

[0152] Therefore, the calculations required to determine the timing of enabling the servo strobe signal SG become easier. Even when the rotational variation tracking function is installed, unintended servo clock corrections can be prevented.

[0153] Furthermore, as described in the fourth embodiment, the first data chip and the second data chip are not limited to the examples described above.

[0154] Furthermore, according to the fifth embodiment, on the disk 11, at a plurality of consecutive second radius positions that are different from a plurality of consecutive first radius positions, the recording frequency of servo data varies according to each second radius position. In the specific configuration described in the fifth embodiment, for example, the plurality of consecutive first radius positions is one of regions 50a, 50b, and 50c, and the plurality of consecutive second radius positions is another of regions 50a, 50b, and 50c. In each of the plurality of servo regions SV, the circumferential position (denoted as the third circumferential position) at each second radius position that is consistent in time among the plurality of second radius positions is written to the first data slice.

[0155] In addition, Figure 13 and Figure 14 In the example shown, the first data slice is a preamble (PR) or a synchronization marker (SN). The first data slice can also be a burst pattern.

[0156] Furthermore, according to the fifth embodiment, in the disk 11, in each of the plurality of servo regions SV, a servo data slice (denoted as the third data slice) different from the first data slice is written to the circumferential position (denoted as the fourth circumferential position) at each of the first radius positions that are consistent in time among the plurality of first radius positions. The third data slice is written to the circumferential position (denoted as the fifth circumferential position) at each of the second radius positions that are consistent in time among the plurality of second radius positions.

[0157] exist Figure 15 and Figure 16 In the example shown, the first data slice is the preamble PR, and the third data slice is the synchronization tag SN. However, the first and second data slices are not limited to these.

[0158] In addition, according to Figure 16 The example shown has the same time position corresponding to the 4th circumference position, i.e., the time position at which the synchronization mark SN is written at multiple 1st radius positions, and the same time position corresponding to the 5th circumference position, i.e., the time position at which the synchronization mark SN is written at multiple 2nd radius positions.

[0159] Therefore, even if the read / write head 22 moves within a radius direction including multiple first radius positions and multiple second radius positions, as long as the rotational speed of the disk 11 does not change, the synchronization mark SN can be detected at the same interval.

[0160] Furthermore, according to the sixth embodiment, in the disk 11, the recording frequency of servo data at a plurality of consecutive radii (denoted as a plurality of first radii) varies for each first radii. At a plurality of consecutive radii closer to the inner periphery of the plurality of first radii (denoted as a plurality of second radii), the recording frequency of servo data is a common value (denoted as a first value). At a plurality of consecutive radii closer to the outer periphery of the plurality of first radii (denoted as a plurality of third radii), the recording frequency of servo data is a common value (denoted as a second value).

[0161] exist Figure 17 In the example shown, region 60b corresponds to multiple first-radius positions. With region 60b representing multiple first-radius positions, region 70a represents multiple second-radius positions, and region 70b represents multiple third-radius positions.

[0162] Therefore, it becomes easier to process the frequency set for the RWC25 during synchronous search operations. In other words, proper servo control can be performed.

[0163] Furthermore, according to the sixth embodiment, the length of the range in the radial direction formed by the plurality of second radius positions and the length of the range in the radial direction formed by the plurality of third radius positions are lengths or more obtained by multiplying the time interval of the magnetic head 22 passing through the servo region SV by the maximum seek speed.

[0164] Therefore, even when the magnetic head 22 moves at high speed (e.g., maximum seek speed) in the radial direction, it can reliably pass through multiple second radial positions or multiple third radial positions during synchronous search operations.

[0165] Alternatively, either the length of the range in the radial direction formed by the plurality of second radius positions or the length of the range in the radial direction formed by the plurality of third radius positions can be set to a length greater than or equal to the length obtained by multiplying the time interval of the magnetic head 22 passing through the servo region SV by the maximum seek speed.

[0166] Furthermore, according to the sixth embodiment, the recording frequency of the first value, i.e., the servo data at the plurality of second radius positions, is equal to the recording frequency of the second value, i.e., the servo data at the plurality of third radius positions.

[0167] Therefore, it becomes even easier to obtain the frequency set by RWC25 during synchronous search operations.

[0168] Furthermore, in the above description, multiple first radius positions are defined as positions of track 41. These multiple first radius positions can also represent the positions of two or more consecutive tracks 41. The same applies to each of the multiple second radius positions and each of the multiple third radius positions.

[0169] Several embodiments of the present invention have been described above, but these embodiments are merely illustrative and not intended to limit the scope of the invention. These new embodiments can be implemented in various other ways, and various omissions, substitutions, and modifications can be made without departing from the spirit of the invention. These embodiments and / or variations thereof are included in the scope and spirit of the invention, and are included in the scope of the invention as set forth in the claims and its equivalents.

Claims

1. A disk drive, comprising: Magnetic head; and The disk has multiple servo regions, each containing multiple data slices, arranged circumferentially and equally spaced in the circumferential direction. At a series of first radius positions, the recording frequency of the servo data varies according to each first radius position. In each of the multiple servo regions, the first data slice among the multiple data slices is written at a first circumferential position where the circumferential movement time of the read / write head is consistent between the multiple first radius positions, based on the timing of the read / write head passing through a reference position on the circumference.

2. The disk drive according to claim 1, The first data slice is a preamble, synchronization marker, or pulse train pattern.

3. The disk drive according to claim 1, In each of the plurality of servo regions on the disk, a second data slice, different from the first data slice, is written at a second circumferential position that is different from the first circumferential position that coincides with the movement time between the plurality of first radii positions.

4. The disk drive according to claim 3, The first data slice is a preamble, and the second data slice is a synchronization marker. The number of waveforms in one cycle contained in the preamble written at the first circumferential position varies among the plurality of first radius positions.

5. The disk drive according to claim 1, On the disk, at a plurality of second radius positions that are different from the plurality of consecutive first radius positions, the recording frequency varies according to each second radius position, and in each of the plurality of servo regions, the first data slice is written at a third circumferential position that is consistent between the plurality of second radius positions during the movement time.

6. The disk drive according to claim 5, The first data slice is a preamble or synchronization marker.

7. The disk drive according to claim 5, In each of the plurality of server regions on the disk, At a fourth circumferential position, which is different from the first circumferential position that coincides with the movement time among the plurality of first radii positions, a third data slice, which is different from the first data slice, is written among the plurality of data slices. The third data slice is written at a fifth circumferential position, which is different from the third circumferential position that is consistent with the movement time among the plurality of second radii positions.

8. The disk drive according to claim 7, The first data slice is a preamble, and the third data slice is a synchronization marker.

9. The disk drive according to claim 8, The movement time corresponding to the fourth circumferential position is equal to the movement time corresponding to the fifth circumferential position.

10. A disk drive, comprising: Magnetic head; and The disk has multiple servo regions, each containing multiple data slices, arranged circumferentially and equally spaced in the circumferential direction. At a series of consecutive first radius positions, the recording frequency of the servo data varies according to each first radius position. Between a series of consecutive second radius positions that are closer to the inner circumference of the series of first radius positions, the recording frequency is a common first value. Between a series of consecutive third radius positions that are closer to the outer circumference of the series of first radius positions, the recording frequency is a common second value.

11. The disk drive according to claim 10, The length of the range in the radial direction formed by the plurality of second radius positions or the length of the range in the radial direction formed by the plurality of third radius positions is greater than or equal to the length obtained by multiplying the time interval of the time the magnetic head passes through the plurality of servo regions by the maximum seek speed.

12. The disk drive according to claim 10, The first value is equal to the second value.

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