JP2007287252A - Erasure method of disk recording surface - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To reduce an area that cannot be erased when performing erasure of a recording surface with a head by reading servo data on the recording surface and positioning the head. <P>SOLUTION: An HDC/MPU 23 uses an allowable range defined by XPES when writing normal user data, and data writing is prohibited at head positions of 115e and 115f. In AC erasure processing, the HDC/MPU 23 uses an allowable range defined by (X+y) PES, and only writing of an AC pattern is prohibited at a head position of 115f. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a method of erasing a recording surface of a disk, and more particularly to a method of reading servo data recorded on a recording surface with a head and erasing with the head.

  As a disk drive device, a device that uses media of various modes such as an optical disk, a magneto-optical disk, or a flexible magnetic disk is known. Among them, a hard disk drive (HDD) is a computer. It is one of the storage devices indispensable in the current computer system. Furthermore, applications of HDDs such as a removable memory used in a moving image recording / reproducing apparatus, a car navigation system, a digital camera, etc. are expanding more and more due to its excellent characteristics.

  An HDD that records and reproduces data by a head element unit performs positioning control of the head element unit based on servo data formed on a magnetic disk. Each of the tracks formed concentrically on the magnetic disk has a plurality of servo sectors, and each servo sector is composed of servo data and user data.

  Increasing the data storage capacity of an HDD is one of the important development goals. As a technique for improving the recording density of a magnetic disk, a perpendicular magnetic recording system has been proposed. In the perpendicular magnetic recording system, recording is performed with the recording magnetization oriented in the direction perpendicular to the recording surface. In perpendicular magnetic recording, unlike in-plane magnetic recording in which the recording magnetization direction is parallel to the recording surface, the demagnetizing field due to adjacent magnetic domains decreases as the recording density increases, so that high recording stability can be realized at high recording density. .

  However, in perpendicular magnetic recording, it is known that a DC erase region (DC magnetization region) on a recording surface adversely affects data reading by a read element. The magnetic field in the DC erase region becomes a disturbance to the read element, and the SER (Soft Error Ratio) of the read signal is greatly reduced. For this reason, Patent Document 1 proposes AC erasing the entire user area including the area between data tracks.

If a DC erase area exists between the data tracks, the magnetic field from this area becomes a disturbance to the read element, and the SER is greatly reduced. Therefore, specifically, it is proposed that this area is subjected to AC erasure (AC magnetization) by a servo writer before writing servo data or in the process of writing servo data to the recording surface.
JP 2002-230734 A

  However, when the servo write process uses self-servo write, AC erase may not be performed before the servo write or in the servo write process. In the self-servo write, a pattern is written by the head element portion of the HDD, and a new pattern writing is performed by measuring the positioning and timing of the head element portion while reading the pattern by the head element portion.

  In the self-servo write, a timing pulse serving as a reference for measuring the write timing is written on the recording surface, but this pattern may not be accurately detected due to the surrounding magnetization where the AC is erased. Further, not only the servo write method but also the case where the recording surface is subjected to the AC erase process after the servo data has been written on the recording surface, it is required that the area not subjected to the AC erase is left as much as possible.

  In the erase method for a disk recording surface according to one aspect of the present invention, the head is positioned with respect to the target servo address using the servo address read from the recording surface by the head. Further, erasing by the head is performed on condition that the servo address read by the head is within the permitted range from the target servo address. The permitted range in the erase is wider than the permitted range in normal writing of user data to the recording surface. By making the permitted range for erasing wider than that for normal writing of user data, it is possible to reduce areas that are not erased.

  The allowable range for retrying the erase process in which the error has occurred may be set as described above. Alternatively, the head is sequentially moved with respect to each target servo address, the erase is sequentially performed in a state in which the head is positioned at the target servo address, the recording surface is erased, and in each erase, It is preferable that the permitted range is wider than the permitted range in normal writing of user data. As a result, the area that is not erased can be reduced, the possibility of error occurrence can be reduced, and the processing time can be shortened.

  The interval between the first and second target servo addresses adjacent to each other, the width of the permitted range on the second target servo address side of the first target servo address, and the second target servo It is preferable that the sum of the widths of the permitted range on the first target servo address side of the address is not more than the write width of the head. As a result, the possibility or area of occurrence of the non-erasing region can be reduced.

  Preferably, in the erase in the state where the servo is positioned at the target servo address, when the head moves out of the permitted range, the erase corresponding to the target servo address is stopped, and the retry for the stopped erase is performed. If it is not erased due to an error in the retry, the user data area corresponding to the target servo address is registered as an unused area. This avoids the use of defective servo data in user data access.

  An erase method for a disk recording surface according to another aspect of the present invention uses a servo data read from a recording surface by a head to position the head with respect to a target servo address, and the servo read by the head・ Erase with the head on condition that the address is within the permitted range from the target servo address, and the head moved out of the permitted range during erasing in the state positioned at the target servo address. In this case, the erase corresponding to the target servo address is stopped, and in the retry for the stopped erase, the target servo address is offset with respect to the target servo address in the stopped erase. In retrying for erasing, by offsetting the target servo address with respect to the target servo address in the stopped erasing, it is possible to increase the possibility of erasing and to prevent the non-erasing area from remaining.

  It is preferable that the sum of the interval between target servo addresses adjacent to each other in normal erase and the offset amount in the retry is equal to or less than the write width of the head. Further, the sum of the interval between the target servo addresses adjacent to each other in normal erase, the width of the permitted range on the opposite side of each of the adjacent target servo addresses, and the offset amount in the retry, It is preferable that the width be equal to or smaller than the write width of the head. As a result, the possibility or the area of the non-erasing region can be reduced.

  The write current in the retry is preferably larger than the write current in the stopped erase. As a result, the possibility or area of occurrence of a non-erasing region due to offset can be reduced.

  In the erase method of the disk recording surface according to another aspect of the present invention, the head is positioned with respect to the target servo address using the servo address read from the recording surface by the head. Further, in a state where the head is positioned with respect to the target servo address, the recording surface is erased by the head. The write current in the erase is larger than the write current in normal writing of user data to the recording surface at the same environmental temperature. A large write current can reduce the possibility or area of occurrence of a non-erase region. The erase by the head may be a retry to the erase process in which an error has occurred.

  According to the present invention, when the servo data on the recording surface is read and the head is positioned and the recording surface is erased by the head, the area that is not erased can be reduced.

  Hereinafter, embodiments to which the present invention can be applied will be described. For clarity of explanation, the following description and drawings are omitted and simplified as appropriate. Moreover, in each drawing, the same code | symbol is attached | subjected to the same element and the duplication description is abbreviate | omitted as needed for clarification of description.

  In the following, embodiments of the present invention will be described by taking a hard disk drive (HDD) as an example of a disk drive device as an example. The HDD according to the present embodiment performs head positioning with servo data on the magnetic disk and erases the user data area. The erase of this embodiment is characterized by setting an allowable range for a deviation from the target, retry in erase, or a write current thereof.

  In order to facilitate understanding of the feature points of this embodiment, first, an outline of the entire configuration of the HDD will be described. FIG. 1 is a block diagram schematically showing the configuration of the HDD 1 according to the present embodiment. As shown in FIG. 1, an HDD 1 includes a sealed enclosure 10 and a magnetic disk 11 as an example of a recording disk, a head element unit 12 as an example of a head, an arm electronic circuit (AE: Arm Electronics) 13, a spindle. A motor (SPM) 14, a voice coil motor (VCM) 15, and an actuator 16 are provided.

  The HDD 1 further includes a circuit board 20 fixed to the outside of the enclosure 10. On the circuit board 20, each IC such as a read / write channel (RW channel) 21, a motor driver unit 22, a hard disk controller (HDC) and an MPU integrated circuit (hereinafter referred to as HDC / MPU) 23, and a RAM 24. It has. Each circuit configuration can be integrated into one IC, or can be divided into a plurality of ICs.

  The magnetic disk 11 of this embodiment is a perpendicular magnetic recording type magnetic disk, and records the recording magnetization in the direction perpendicular to the recording surface. The magnetic disk 11 is fixed to the SPM 14. The SPM 14 rotates the magnetic disk 11 at a predetermined angular velocity. The motor driver unit 22 drives the SPM 14 in accordance with control data from the HDC / MPU 23 which is an example of a controller. Each head element unit 12 is fixed to a slider (not shown). The slider is fixed to the tip of the actuator 16. The actuator 16 is connected to the VCM 15 and moves in the radial direction on the magnetic disk 11 rotating the head element unit 12 (and the slider) by rotating about the rotation axis. The motor driver unit 22 drives the VCM 15 according to control data (referred to as DACOUT in this specification) from the HDC / MPU 23.

  The head element unit 12 includes a write element that converts an electric signal into a magnetic field according to recording data (write data) to the magnetic disk 11, and a read element that converts a magnetic field from the magnetic disk 11 into an electric signal. Yes. One or more magnetic disks 11 may be provided, and the recording surface can be formed on one side or both sides of the magnetic disk 11.

  The AE 13 selects one head element unit 12 that accesses the magnetic disk 11 from among the plurality of head element units 12, and amplifies a reproduction signal reproduced by the selected head element unit 12 with a constant gain ( Preamplifier) and send to the RW channel 21. Further, the recording signal from the RW channel 21 is sent to the selected head element unit 12. The RW channel 21 amplifies the read signal supplied from the AE 13 to have a constant amplitude, extracts data from the acquired read signal, and performs a decoding process. Data to be read out includes user data and servo data. The decoded user data is supplied to the HDC / MPU 23. The RW channel 21 code-modulates the write data supplied from the HDC / MPU 23, converts the code-modulated write data into a write signal, and supplies it to the AE 13.

  In the HDC / MPU 23, the MPU operates according to the code loaded in the RAM 24. Along with the activation of the HDD 1, the RAM 24 is loaded with data necessary for control and data processing from the magnetic disk 11 or ROM (not shown) in addition to the code operating on the MPU. The HDC / MPU 23 performs necessary processing related to data processing such as read / write processing control, command execution order management, positioning control (servo control) of the head element unit 12 using a servo signal, interface control, defect management, etc. The entire control of the HDD 1 is executed. The HDC / MPU 23 of this embodiment executes an erase process for each recording surface of the magnetic disk 11. This will be described in detail later.

  The recording data on the magnetic disk 11 will be described with reference to FIG. As shown in FIG. 2, the recording surface of the magnetic disk 11 has a plurality of adjacent servo areas 111 extending radially from the center of the magnetic disk 11 and spaced apart by a predetermined angle. A data area 112 is formed between the two servo areas 111. Servo data for controlling the positioning of the head element unit 12 is recorded in each servo area 111.

  The data area 112 has a user data area for storing user data and a management area for storing control data of the HDD 1. A plurality of data tracks 113 having a predetermined width in the radial direction and concentrically formed are formed on the recording surface of the magnetic disk 11. User data is recorded along the data track. One data track has a plurality of data sectors (user data recording units).

  The data tracks are grouped into a plurality of zones 114 a to 114 c according to the radial position of the magnetic disk 11. In FIG. 2, three zones 114a-114c are illustrated. The recording frequency is different for each zone, and the number of data sectors included in one data track is set for each zone. Similarly, the magnetic disk 11 has a plurality of servo tracks having a predetermined width in the radial direction and formed concentrically. Each servo track is composed of a plurality of servo data separated in the data area 112.

  FIG. 3 schematically shows a part of the data area 112 and the servo area 111. The magnetic disk 11 of this embodiment records data according to an adaptive format in which the data track pitch and the servo track pitch are different. The magnitude relationship between the data track pitch and the servo track pitch changes depending on the design of the HDD 1 and can be changed for each magnetic disk in the same HDD 1.

  FIG. 3 schematically shows the positions of the write element 121 and the read element 121 during data reading and data writing. In this example, when the head element unit 12 is positioned on the magnetic disk 11, the write element and the read element are at different positions in the radial direction. This difference (distance) in the radial direction between the write element and the read element is called a read / write offset.

  In FIG. 3, a write element position 121a and a read element position 122a indicate a head position at the time of data reading, and a write element position 121b and a read element position 122b indicate a head position at the time of data writing. Also, the rectangular radial dimensions 121 and 122 correspond to the write width and the read width, respectively. The write width is a radial dimension of a region where the write element 121 writes data, and the read width is a radial dimension of a region where the read element 122 reads data.

  In FIG. 3, the read element 122a is positioned at a position for reading the data track DTr_m. On the other hand, the read element 122b is positioned at a position where the write element 121b writes user data to the data track DTr_m-2. In both the reading of the data track DTr_m and the writing of the data track DTr_m-2, the target servo address is on the servo track STr_n, and the position in the servo track STr_n is different.

  As described above, when the data track pitch and the servo track pitch are different, the target position of the head element unit 12 is not always the center of the servo track, and the position in the servo track depends on the target position. Different. Therefore, it is necessary to use different bursts according to the target position for positioning control of the head element unit 12. In addition, FIG. 3 shows each element typically, and each dimension and positional relationship do not reflect the thing of an actual product correctly.

  The HDD 1 according to this embodiment executes an erasing process for each recording surface of the magnetic disk 11. In a perpendicular magnetic recording type HDD, the DC erase area on the recording surface adversely affects data reading by the read element 122. The magnetic field in the DC erase region becomes a disturbance to the read element 122, and the SER of the read signal is greatly reduced.

  In particular, self-servo writing, in which servo data is written to the magnetic disk 11 by using a mechanical mechanism inside the HDD, is typically performed by DC erasing the recording surface, which is a problem in a perpendicular recording type HDD. . Therefore, the HDD 1 of this embodiment converts the DC erase area into the AC erase area by performing the AC erase process on the recording surface by the head element unit 12. In AC erase, a pattern having a predetermined frequency is written on the recording surface. Typically, the frequency is constant, and the highest frequency at which the head element unit can write is selected.

  It is important that the HDD 1 performs AC erase as much as possible on the area where user data is recorded. Here, as shown in FIG. 3, the data track pitch is larger than the write width of the write element 121. As a result, it is possible to prevent squeeze from occurring due to shaking in positioning of the head element portion 12. However, even if the write element 121 is positioned at the center of the data track, a DC erase area remains between the data tracks. In order to improve the SER in the read process, it is required to AC erase the area between the data tracks in addition to each data track.

  The HDD 1 of this embodiment sequentially positions the head element unit 12 with the servo track as a reference, and performs erasure by the write element 121 at the positioned position. A target position is designated by a servo address, and the head element unit 12 is moved to that position. In a state where the head element unit 12 follows the target position, the recording surface is erased (generation of an erase track). When erasing of one round at the target position is completed, the next target position is designated by a servo address, and the head element unit 12 is moved there. This process is repeated. Specifically, as shown in FIG. 4A, the HDD 1 sequentially seeks the head element unit 12 (read element 122) to the target position at a half servo track pitch, and the head element unit 12 at the target position. In the state where the (read element 122) is positioned, the write element 121 is erased for one round of the magnetic disk.

  Since the write width is larger than the half servo track pitch, the above process is repeated, whereby the entire area for recording the user data including all data tracks and between the data tracks can be AC erased. In order to reliably and efficiently perform AC erase, it is preferable to sequentially move the head element unit 12 in the same radial direction at a half servo track pitch. However, since the interval between adjacent target positions is equal to or less than the write width, In addition, the unerased area in the radial direction can be eliminated. Further, the head element unit 12 may be moved at a pitch smaller than the half servo track pitch.

  In the example of FIG. 4A, the read element 122 sequentially moves by half servo track pitch from the outer periphery (OD) side to the inner periphery (ID) side, and as a result, the write element 121 is substantially the same. Move to. Since the movement is a half servo track pitch, the read element 122 makes two rounds at different positions in the same servo track. In order to seek accurately with a half servo track pitch, the HDD 1 designates a target by a servo address. The servo address is represented by a servo track ID (servo track number), a servo sector ID (servo sector number), and a PES (Position Error Signal). The servo address in the radial direction of the magnetic disk 11 is specified by the servo track ID and the PES.

  The servo address will be described. As shown in FIG. 4A, each servo data is composed of a servo AGC (Auto Gain Control: AGC), a servo address mark (SAM), a gray code, and a servo track ID for specifying a servo track. (SERVO TRACK), servo sector ID (SERVO SECTOR) for specifying a servo sector in the servo track, and a burst pattern for fine position control.

  The HDD 1 determines the gain value of AGC using the read amplitude of the servo AGC. The SAM provides timing for the RW channel 21 to process servo data. The servo track number specifies each servo track, and the servo sector ID specifies each servo sector in the servo track.

  The burst pattern is composed of four bursts A, B, C, and D having different circumferential positions and radial positions. Each burst is arranged from the inner circumference side in the order of bursts A, B, C, and D. The relative position in the servo track can be determined by the amplitude of the reproduction signal of each burst. As shown in FIG. 4B, in this example, the position in the servo track is represented by a PES value divided into 256 in the radial direction. That is, the position in the radial direction is represented by the servo track ID and the PES value.

  In the example of FIG. 4B, the inner circumference (ID) side end is PES0 and the outer circumference (OD) side end is PES255 in the servo track. The positions of adjacent servo tracks PES0 and PES256 are the same. The center of each servo track is PES128. The PES is determined by the burst pattern. Specifically, the HDD 1 of the present embodiment controls the positioning of the main PES (MPES) calculated using the burst A and the burst B and the secondary PES (SPES) calculated using the burst C and the burst D. Used in.

  MPES is calculated using | A−B | / (A + B). The SPES is calculated using | C−D | / (C + D). Here, each alphabet represents a read amplitude value of each burst. The HDC / MPU 23 changes the PES used according to the head position. Specifically, the HDC / MPU 23 uses MPES when the target servo address read by the head element unit 12 is between PES64 and PES192. When the read servo address is in the other area, the HDD 1 uses SPES.

  Although bursts used in 64 PES and 192 PES are switched, the relationship between the PES and the physical movement amount is different from that in other regions, and there is a distortion of the relationship. Specifically, in the vicinity of 64 PES and 192 PES, the rate of change of the physical movement amount with respect to the PES change amount increases, and the positioning stability decreases. For this reason, in this example, in each servo track, the head element unit 12 is sequentially moved using 32 PES and 160 PES separated from these PES values as target servo addresses. The interval between 32 PES and 160 PES is 128 PES, which matches the half servo track width.

  The HDD 1 according to the present embodiment uses a permitted range wider than the permitted range in the normal write process in the AC erase process. The head element unit 12 writes user data or an AC erase pattern on condition that it is within the permitted range from the target position. When the head element unit 12 is out of the permitted range, the HDC / MPU 23 stops writing user data or an AC erase pattern.

  This permission range will be described with reference to FIG. FIG. 5 shows a permitted range in the normal write process and a permitted range in the AC erase process. The permitted range is defined by two boundary PES values (write inhibit values) on the inner and outer peripheral sides of the target servo address. The permitted range in normal user data writing is defined by the normal write inhibit value (NORMAL WRITE INHIBIT). On the other hand, the permitted range in AC erase is defined by the AC ERASE WRITE INHIBIT value.

  In the example of FIG. 5, the write inhibit value for normal user data writing is XPES (X is a positive integer) on the inner and outer peripheral sides from the target position (TARGET). The write-inhibit value of the permitted range in the AC erase is (X + y) PES (y is a positive integer) on the inner peripheral side and the outer peripheral side. For example, X is set to 30 PES and y is set to 15 PES.

  Each circle 115a-115f in FIG. 5 represents a head position (servo address) calculated from each servo data sequentially read by the head element unit 12 (read element 122). In normal user data writing, the HDC / MPU 23 uses a permission range defined by XPES, and the head positions 115e and 115f are prohibited from writing data. In the AC erase process, the HDC / MPU 23 uses a permission range defined by (X + y) PES, and only the head position 115f is prohibited from writing an AC pattern.

  As described above, when the PES value read by the head element unit 12 is more than the write inhibit value on the inner circumference or outer circumference side from the target servo address, the HDC / MPU 23 writes the user data or the AC erase pattern. Absent. That is, if it is before writing, the HDC / MPU 23 does not start writing, but stops it if writing is in progress. Thus, the write condition is that the PES value is within the write inhibit value with the target servo address as a reference.

  In normal user data writing, writing is prohibited / permitted using a write inhibit value to prevent data writing (squeeze writing) to an adjacent data track. If the head position is not stable even after a plurality of retries, the data track corresponding to this servo data is registered as an unused area.

  On the other hand, in the AC erase, it is not necessary to consider the squeeze of the adjacent erase track. It is preferable to AC erase the user data area as much as possible. If the read servo address is out of the permitted range from the target servo address and erasing is skipped at the position where AC erasing is stopped, an area that is not AC erased remains in the user data area.

  However, not specifying the permitted range in AC erase causes another problem. If the head position is not stable with respect to the target position, it is often defective in the servo data. If the head element 12 is forced to follow the defective servo data, the actuator 16 will run away and the servo data will be AC erased, or the head element 12 and the magnetic disk 11 will be damaged. There is a possibility to give. As described above, the HDD 1 according to the present embodiment performs AC erase using a wider permission range than the normal write process. As a result, the above problem can be avoided and the possibility that an area that is not AC erased remains can be reduced.

  The allowable range in AC erase is preferably set so as to suppress the occurrence of an area that is not AC erased as much as possible. As described above, in the AC erase process of this embodiment, the interval between adjacent target positions is equal to or less than the write width. However, it is important to consider the fluctuation of the head element unit 12 within the permitted range in order to more surely prevent the area that is not AC erased. Even if the head position fluctuates within the allowable range, it is preferable that the erase regions at the adjacent target positions overlap. In other words, it is preferable to set the allowable range so that the ends of the AC erase area overlap each other even when the head position is shifted to the opposite side in each of the adjacent target servo addresses.

  FIG. 6 shows a preferable example of two adjacent target positions and a permission range corresponding to each target position. The write element position 121c shows a state in which the light element position 121c is positioned without deviation from the outer peripheral side target position (TARGET_N). The write element position 121e shows a state in which the write element position 121e is positioned without deviation from the inner peripheral target position (TARGET_N + 1).

  The write element position 121e indicates a state in which the head element unit 12 is most shifted to the opposite side (outer peripheral side) of the inner peripheral target position in a state where the write element position 121e is positioned at the outer peripheral target position. In addition, the write element position 121f indicates a state in which the head element unit 12 is most shifted to the opposite side (inner peripheral side) of the outer peripheral target position in a state where the write element position 121f is positioned at the inner peripheral target position. Each of the write element positions 121c to 121f in the figure corresponds to a region AC-erased by the write element 121, and the dimension in the radial direction is the write width.

  In FIG. 6, there is no gap in the radial direction of the magnetic disk 11 between the write element position 121e and the write element position 121f. Therefore, the entire data area is AC erased by the write element 121 between the outer target position and the inner target position. In order to realize this state, it is necessary to satisfy the following conditions.

  The write width of the write element 121 is W, the write inhibit value on the outer peripheral side with respect to the outer target position (TARGET_N) is (AC ERASE INHIBIT_N), and the write inhibit value on the inner peripheral side with respect to the inner target position (TARGET_N + 1). (AC ERASE INHIBIT_N + 1) is defined as an interval L between the outer peripheral side target position and the inner peripheral side target position. In addition, these can be represented by a PES value, for example.

  When the relationship of W ≧ L + (AC ERASE INHIBIT_N) + (AC ERASE INHIBIT_N + 1) is established between these four values, the entire area between the targets may be AC erased regardless of the head position fluctuation. it can. When the adjacent target position in the AC erase process satisfies the above relationship, the occurrence of a gap between the AC erase tracks can be more reliably suppressed.

  In addition, from the viewpoint of facilitating control, it is preferable that the permitted range at each target position is the same, but it can be changed depending on the target position. Similarly, the write inhibit values on the inner peripheral side and the outer peripheral side are preferably the same, but different values may be set for these.

  FIG. 7 is a block diagram schematically showing components related to the erase processing of the present embodiment. The AC erase process control unit 231 controls the erase process for each recording surface of the magnetic disk 11. The AC erase processing control unit 231 is implemented as a logical component of the HDC / MPU 23, and functions as the AC erase processing control unit 231 when the MPU of the HDC / MPU 23 operates according to the code. Alternatively, the AC erase processing control unit 231 can be configured by a part of the hardware configuration of the HDC / MPU 23 and the MPU that operates according to the code.

  The RW processing control unit 232 is a logical component that executes and controls normal read and write processing in the HDD 1. In the present embodiment, the RW processing control unit 232 controls the execution of the positioning control of the head element unit 12 and the actual erasing of the recording surface in the erasing process of the present embodiment in accordance with the instruction of the AC erase processing control unit 231. . The RW processing control unit 232 includes a part of the hardware configuration of the HDC / MPU 23 and an MPU that operates according to a code.

  In the initial setting of the AC erase process, the AC erase process control unit 231 sets a write inhibit value (WRITE INHIBIT) in the RW process control unit 232. The RW process control unit 232 controls AC erase according to the set write inhibit value in the AC erase process.

  The AC erase process control unit 231 designates a servo address (SERVO TARGET) as a target to the RW process control unit 232 and instructs AC erase at the target position. The RW processing control unit 232 uses the servo address (SERVO DATA) acquired from the head element unit 12 via the AE 13 and the RW channel 21 to seek the head element unit 12 to the target servo address. Specifically, the value of the VCM current (VCM CURRENT) to be passed to the VCM 15 is determined from the target servo address and the acquired current servo address, and control data (DACOUT) indicating the value is supplied to the motor driver unit. 22 to output.

  In a state where the head element unit 12 is positioned at the target position, the RW processing control unit 232 instructs the RW channel 21 to perform AC erase at that position by a control signal (CONTROL SIGNALS). The RW channel 21 outputs an AC erase signal to the AE 13 while instructed by the RW processing control unit 232.

  When erasing of one round of the magnetic disk 11 at the target position is completed, as described with reference to FIG. 4B, the AC erase processing control unit moves the head element unit 12 by a half servo track pitch. . Thereafter, seek, positioning and erasing of the head element unit 12 are repeatedly executed, and erasing in the user data area is advanced.

  In a state where the head element unit 12 is positioned at the target position, if the servo address value read by the head element unit 12 is out of the permitted range, the RW processing control unit 232 instructs the RW channel 21 to stop AC erase. . Further, the RW processing control unit 232 executes the AC erase retry that has been stopped. This retry will be described in detail later. If AC erase cannot be completed at the target position even after retrying a predetermined number of steps, the RW process control unit 232 notifies the AC erase process control unit 231 of the result.

  The AC erase processing control unit 231 registers the data track corresponding to the servo address in which an error has occurred in the defect management table 241 as an unused area. The RW processing control unit 232 does not use the data track registered in the defect management table 241 for recording user data. The data track to be registered includes the corresponding data track in the write. If defective servo data is used in writing, other user data may be overwritten. By registering as a non-use area in this way, it is possible to prevent the servo data having a defect from being used and writing user data.

  In addition to the data track corresponding to the write, it is preferable to include the data track corresponding to the read. Accordingly, it is possible to prevent in advance that user data cannot be read due to servo data having a defect. Further, in addition to the data track to be registered corresponding to the servo address in which an error has occurred, it is preferable to register one or a plurality of data tracks adjacent on the inner and outer peripheral sides as unused areas. . This is because if there is a defect in the servo data, there is a high possibility that the servo data adjacent thereto is also defective.

  The data track corresponding to the write can be, for example, the data track whose target servo address used in writing the user data is closest to the servo address in which the error occurred. Similarly, the data track corresponding to the read can be the data track whose target servo address used for reading the user data is closest to the servo address where the error occurred. Alternatively, the servo address can be divided by the number of data tracks, and a servo address area including the target servo address can be associated with each data track in advance.

  The AC erase processing control unit 231 needs to specify the corresponding data track number in writing and reading from the servo address. The AC erase processing control unit 231 according to the present embodiment converts the servo address into a data track number by using a function that the RW processing control unit 232 has as a normal function. In reading and writing user data, the RW processing control unit 232 calculates a servo address corresponding to the data track designated by the host 51 from the data designated. The AC erase processing control unit 231 uses this function to specify the data track number from the servo address.

  Specifically, the AC erase processing control unit 231 designates a preset data track number and passes a seek command for writing or reading to the RW processing control unit 232. The RW processing control unit 232 calculates a corresponding servo address from the data track number, and returns the servo address to the AC erase processing control unit 231. The AC erase processing control unit 231 compares the acquired servo address with the servo address in which an error has occurred, and confirms the difference.

  If the difference is within the preset range, the AC erase processing control unit 231 identifies the data track as the corresponding data track. If the difference exceeds a preset value, the AC erase processing control unit 231 determines a new data track number to be passed to the RW processing control unit 232 from the magnitude relationship and the difference between the two servo addresses. The servo address has a monotonically increasing or monotonically decreasing relationship with the data track number, and the AC erase processing control unit 231 determines the data address to be passed next so that it approaches the servo address that caused the error. can do.

  As described above, when the servo address read by the head element unit 12 is out of the permitted range from the target, the RW processing control unit 232 stops erasing. Receiving the stop notification, the AC erase process control unit 231 executes a retry process for the stopped erase. The erase retry process includes a plurality of different retry steps. One of them is an erase retry step under the same conditions.

  The retry in this embodiment further includes a retry step for offsetting the target position. In normal write processing, it is not desirable to shift the target position in order to avoid squeezing of adjacent tracks, but there is no problem of squeezing in AC erasing, and AC erasing is performed as much as possible to reduce the area that is not erased. It is important to.

  In the retry with the target position offset, the offset amount is important. When the offset is large, the erase areas corresponding to the adjacent target positions are separated without overlapping. Then, an area that is not AC erased remains, or an area that is not AC erased becomes large.

  FIG. 8 shows an example of the write element position when an error occurs during erasing at the first target position (TARGET_N) and a retry is performed. The write element position 121g corresponds to the erase at the target position (TARGET_N), and the write element position 121i corresponds to the erase at the target position (OFFSET) in the retry. In the retry, the write element is offset by the offset amount F on the outer peripheral side.

  As shown in FIG. 8, the interval between the adjacent target position on the inner peripheral side (TARGET_N + 1) and the outer peripheral side target position (TARGET_N) before retrying is represented by L. The sum (F + L) of the interval L and the offset amount F is preferably equal to or less than the write width (W) of the head element portion 12. That is, it is preferable that the write element position 121i and the write element position 121h overlap in the radial direction.

  When the above condition is satisfied, if the offset is not offset in the erase of the adjacent target position (TARGET_N + 1), even if the target position is offset in the retry, if the head element unit 12 is on the target, the adjacent erase area There is no space between them. In this way, the offset amount (F) of the target position (OFFSET) in the retry is the side (OD side in the example of FIG. 8) that is offset from the target position (TARGET_N) before the retry (ID in the example of FIG. 8). The value (F + L) obtained by adding the distance (L) to the adjacent target position (TARGET_N + 1) on the side) is equal to or smaller than the write width (W) of the head element unit 12, It is possible to prevent a region that is not erased from being widened and greatly affect the read operation.

  Here, also in the retry, the HDD 1 executes AC erase on the condition that the servo address read by the head element unit 12 is within the permitted range from the servo address of the target. Therefore, the position of the head element unit 12 (the write element 121) in the radial direction fluctuates within the permitted range. In an HDD in which a slight DC erase area is also a problem, it is preferable that no gap exists between adjacent erase areas even if the head position fluctuates within this permitted range.

  In FIG. 8, a write element position 121j shows a state in which the head element unit 12 is most shifted to the outer peripheral side during erase at the offset target position (OFFSET). The write element position 121k shows a state in which the head element unit 12 is most displaced to the inner peripheral side during erasure at the inner peripheral target position (TARGET_N + 1).

  As shown in FIG. 8, the outer peripheral inhibit value (AC ERASE INHIBIT_N) of the outer peripheral target servo address (TARGET_N) and the inner peripheral inhibit value of the inner peripheral target servo address (TARGET_N + 1) (TARGET_N + 1) A value obtained by further adding (AC ERASE INHIBIT_N + 1) to the above (F + L) is preferably equal to or less than the write width (W) of the head element portion 12. That is, it is preferable to satisfy the relationship of W ≧ (F + L) + (AC ERASE INHIBIT_N) + (AC ERASE INHIBIT_N + 1). As a result, even if the light element position fluctuates in the radial direction within the permitted range,

  In the example described above, the retry is executed only at one of the adjacent target positions. However, both adjacent target positions may retry. In this case, if the offset direction is the same, it can be dealt with in the previous examples. However, when the offset direction is offset in a different direction, the interval between the erase regions is further increased. Therefore, different considerations are necessary for the offset amount and the inhibit value.

  FIG. 9 shows an example of offsets in opposite directions at both adjacent target positions. The write element position 121l corresponds to the erase at the outer peripheral side target position (TARGET_N), and the write element position 121n corresponds to the erase at the target position (OFFSET_N) in the retry. In the retry, the write element is offset by the offset amount F_N on the outer peripheral side. The write element position 121p indicates a state in which the head element unit 12 is most shifted to the outer peripheral side during erase at the offset target position (OFFSET_N). The outer side inhibit value is AC ERASE INHIBIT_N.

  The write element position 121m corresponds to the erase at the inner periphery side target position (TARGET_N + 1), and the write element position 121o corresponds to the erase at the target position (OFFSET_N + 1) in the retry. In the retry, the write element is offset by the offset amount F_N + 1 on the outer peripheral side. The write element position 121q indicates a state in which the head element unit 12 is most shifted to the inner peripheral side in the erase at the offset target position (OFFSET_N + 1). The inner circumference inhibit value is AC ERASE INHIBIT_N + 1.

  The interval between the adjacent target position (TARGET_N + 1) on the inner peripheral side and the outer target side position (TARGET_N) before retrying is represented by L. The sum (L + (F_N) + (F_N + 1)) of the interval L and the offset amounts F_N and F_N + 1 of each target position is preferably equal to or less than the write width (W) of the head element unit 12. That is, it is preferable that the write element position 121n and the write element position 121o overlap in the radial direction.

  In consideration of the fluctuation of the head position within the allowable range, (L + (F_N) + (F_N + 1) + (AC ERASE INHIBIT_N) + (AC ERASE INHIBIT_N + 1)) is the write width of the head element portion 12 ( W) More preferably, it is the following. Thus, retry is performed by offsetting in the opposite direction at the adjacent target position, and even if the head position fluctuates within the permitted range, the entire area between the target positions can be reliably AC erased.

  In the AC erase retry, when the target position is offset, increasing the write current is one of the preferable modes. By offsetting, the interval between adjacent target positions is widened. However, since an increase in write current leads to an increase in write width, it is possible to prevent the occurrence of an area that is not AC erased or to narrow the area. As shown in FIG. 7, the AC erase processing control unit 231 sets a write current value (WRITE CURRENT VALUE) in the AE 13.

  In a normal AC erase process that is sequentially executed, the AC erase processing control unit 231 sets a predetermined current value. At the start of the retry process, the AC erase process control unit 231 sets a predetermined current value that is larger than the write current value in the normal erase process. When the AC erase retry is completed, the AC erase processing control unit 231 sets the write current value in the normal AC erase process to the AE 13 again. Note that the AC erase processing control unit 231 can change the write current value according to the temperature. Specifically, the HDD 1 includes a temperature detector (not shown), and the AC erase processing control unit 231 changes the write current according to the detected temperature.

  In addition, it is preferable that the AC erase process control unit 231 perform AC erase using a write current larger than the write current in the user data write process under the same conditions in the AC erase process. That is, not only the AC erase retry but also a normal AC erase process uses a value larger than the current value in the user data write process.

  The HDD 1 may change the write current value in the user data write process according to the temperature. In this case, the AC erase processing control unit 231 executes AC erase using a write current higher than the write current of user data at the same temperature. Continuing to use a large current induces device deterioration and may generate noise in reading servo data. From this point, it is preferable to increase the write current so as to compensate the offset in the retry as described above.

  As mentioned above, although the preferable form of this invention was demonstrated, this invention is not limited only to embodiment mentioned above, A various change is possible in the range which does not deviate from the summary of this invention. For example, the present invention is suitable for an HDD, but can be applied to a disk drive device using another recording disk. Further, as described above, the present invention is particularly useful for AC erase of perpendicular magnetic recording, but does not prevent application to DC erase processing in in-plane recording.

  The present invention is particularly useful for erasing a disc recorded in an adaptive format, but the present invention can be applied to erasing a recording surface of a different format. In addition, the present invention may be applied to erasing a part of the user data area. The head element portion is preferably moved sequentially in the same direction in the radial direction, but other moving methods may be employed. As mentioned above, it is preferable to position the head by directly specifying the servo address of the target position. However, the setting of the permission range and the setting of the write current are applicable to the erase process using other head position control. can do.

In this embodiment, it is a block diagram which shows typically the whole structure of a hard-disk drive. In this embodiment, it is a figure which shows typically the state of the recording data of the recording surface of a magnetic disc. In this embodiment, it is a figure which shows typically the position of the write element at the time of data reading and data writing, and a read element. In this embodiment, it is a figure which shows typically the data format of servo data, and the movement method of the read element (head element part) in an erase process. In this embodiment, it is a figure which shows typically the relationship of the permission range in the value of the servo address sequentially read by the head element part, the writing range of normal user data, and the AC erase process. In this embodiment, it is a figure which shows typically the relationship between the adjacent target position in AC erase processing, each permission range, and write width. In this embodiment, it is a block diagram which shows typically the logic structure relevant to AC erase process. In this embodiment, when offsetting one target position in a retry, it is a figure which shows typically the relationship between an offset position, a permission range, and a write width. In this embodiment, it is a figure which shows typically the relationship between an offset position, a permission range, and a write width in the case of offsetting two adjacent target positions in the reverse direction.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Hard disk drive, 10 Enclosure, 11 Magnetic disk 12 Head element part, 13 Arm electronics, 14 Spindle motor 15 Voice coil motor, 16 Actuator, 20 Circuit board 21 RW channel, 22 Motor driver unit 23 Hard disk Controller / MPU, 24 RAM, 51 Host 111 Servo area, 112 Data area, 113 Data track 114a-114c Zone, 115a-115f Head position 121 Write element position, 122 Read element position 231 AC erase processing controller, 232 RW Processing control unit

Claims (11)

Using the servo address read from the recording surface by the head, position the head relative to the target servo address,
On the condition that the servo address read by the head is within the permitted range from the target servo address, erase by the head is performed,
The permitted range in the erase is wider than the permitted range in normal writing of user data to the recording surface,
Erase method for the disk recording surface. The head is sequentially moved with respect to each target servo address, the erase is sequentially performed in a state where the head is positioned at the target servo address, and the recording surface is erased.
In each erase, the permitted range is wider than the permitted range for normal writing of user data.
The method of claim 1. Erase by the head is a retry to the erase process in which an error has occurred.
The method of claim 1. The interval between the first and second target servo addresses adjacent to each other, the width of the permitted range on the second target servo address side of the first target servo address, and the second target servo The sum of the allowed range width of the address on the first target servo address side is less than or equal to the write width of the head;
The method of claim 1. In erasing in the state positioned at the target servo address, when the head moves out of the permitted range, the erase corresponding to the target servo address is stopped,
Execute retry for the stopped erase,
If not erased due to an error in the retry, register the user data area corresponding to the target servo address as an unused area.
The method of claim 1. Use the servo data read from the recording surface by the head to position the head relative to the target servo address,
On the condition that the servo address read by the head is within the permitted range from the target servo address, erase by the head is performed,
In erasing in the state positioned at the target servo address, when the head moves out of the permitted range, the erase corresponding to the target servo address is stopped,
In retry for the stopped erase, offset the target servo address with respect to the target servo address in the stopped erase;
Erase method for the disk recording surface. The sum of the interval between target servo addresses adjacent to each other in normal erase and the offset amount in the retry is equal to or less than the write width of the head.
The method of claim 6. The sum of the interval between target servo addresses adjacent to each other in normal erase, the width of the permitted range on the opposite side of each adjacent target servo address, and the offset amount in the retry is the head. Less than or equal to the light width of
The method of claim 6. The write current in the retry is larger than the write current in the stopped erase.
The method of claim 6. Using the servo address that the head reads from the recording surface, position the head relative to the target servo address,
In a state where the head is positioned with respect to the target servo address, the recording surface is erased by the head,
The write current in the erase is larger than the write current in normal writing of user data to the recording surface at the same environmental temperature.
Erase method for the disk recording surface. Erase by the head is a retry to the erase process in which an error has occurred.
The method of claim 10.

Images