This application is based upon and claims the benefit of priority from Japanese Patent Application No. 2010-148320, filed Jun. 29, 2010; the entire contents of which are incorporated herein by reference.
Embodiments described herein relate generally to a magnetic recording medium which records servo data, and to a disk device.
Magnetic disks as recording media used for magnetic disk devices each comprise a data recording area and a servo data area. The data recording area includes data tracks which are formed coaxially. Servo data for each of the data tracks is recorded in advance in the servo data area.
In general, a multi-stack-servo write schema and a self-servo write schema are employed in servo data recording onto a magnetic disk. According to the multi-stack-servo write schema, servo data is written to pluial magnetic disks all at once, with the magnetic disks stacked on a spindle. According to the self-servo write schema, a magnetic disk is built in a magnetic disk device in which servo data is written to the magnetic disk by a magnetic head of the device itself inside the device. In any of the foregoing schemas, a magnetization direction in servo data writing has an angle corresponding to a skew angle of a head, depending on a radial position of a magnetic disk. The magnetic disk to which servo data has thus been written has a magnetization direction which is substantially equal to the skew angle of the head used in the magnetic disk device. An angle (azimuth angle) between the magnetization direction and the head is small. Therefore, the servo data can be read excellently, and the output from the head decreases little.
Another known recording schema for servo data is a magnetic-transfer recording schema in which servo data is recorded on a magnetic disk by transferring magnetic data to the magnetic disk from a master magnetic recording disk. In this magnetic-transfer recording schema, servo data is not written by a magnetic head which is compatible with an actual disk device during servo data recording but the magnetic disk is magnetized by a master magnetic recording disk. At this time, if the magnetization direction is an in-plane direction, the magnetization direction of the servo data becomes a constant direction which is vertical to a radial direction, independently from radial positions on the magnetic disk. According to the magnetic-transfer recording schema, magnetic disks can be manufactured at lower costs in a shorter time than according to the multi-stack-servo write schema and self-servo write schema.
However, when a magnetic disk to which servo data has been written by the magnetic-transfer recording schema as described above is used in a magnetic disk device, an azimuth angle is formed between a magnetization direction of the servo data and a magnetic head, due to a head skew angle in the device. If the azimuth angle is large, an output obtained from the magnetic head which has read magnetic data decreases, thereby decreasing the signal-to-noise ratio of the servo data. This phenomenon causes a reduction in positioning accuracy and data reading accuracy of the magnetic head with respect to data tracks of the magnetic disk.
Particularly in the magnetic-transfer recording method in which data is magnetically written to a magnetic disk by horizontally applying a magnetic field in a circumferential direction of the disk, magnetization efficiency is maximum at a direction vertical to a magnetic field direction, i.e., by a magnetization pattern parallel to a radial direction. When an azimuth angle is formed in a magnetization direction or particularly when a phase pattern is used, the signal-to-noise ratio of a reproduced signal from a magnetization pattern decreases conspicuously. Such a decrease of signal-to-noise ratio of a reproduced signal is a factor which reduces the positioning accuracy required for a large-volume magnetic disk device.
A general architecture that implements the various features of the embodiments will now be described with reference to the drawings. The drawings and the associated descriptions are provided to illustrate the embodiments and not to limit the scope of the invention.
Various embodiments will be described hereinafter with reference to the accompanying drawings.
In general, according to one embodiment, a magnetic recording medium on which servo data is recorded by magnetic transfer recording, the medium comprises a data recording area in which data is recorded on a plurality of data tracks extending in form of concentric circles; and a servo area comprising the servo data corresponding to the data tracks. The servo data comprises a plurality of burst patterns for tracking detection, which are arranged in a circumferential direction of the data tracks, and the burst patterns comprise a number of recording crests which differs depending on a radial position on the magnetic recording medium.
Hereinafter, descriptions will be made of a magnetic recording medium and a magnetic disk device comprising the recording medium according to each of the embodiments.
As shown in
The recording layers 56 forming recording areas are each formed in a ring shape which is coaxial to the substrate. The recording layers 56 are formed of a ferromagnetic material, e.g., CoCrPt. Each of the recording areas of the magnetic disk 50 comprises or, in other words, is roughly divided into a data recording area 58 and plural servo areas 60.
As shown in
As shown in
As shown in
The magnetic disk 50 is constituted as a magnetic-transfer recording type. That is, magnetic data including servo data is recorded by transferring the magnetic data onto the recording layers 56 of the magnetic disk 50 from an original magnetic recording disk (or a master disk). A magnetization direction of the servo data is a constant direction which is vertical to the radial directions, independently from radial positions of the magnetic disk 50.
Next, a servo pattern for the servo areas 60 will be described in details below.
The servo data pattern is constituted by or, in other words, roughly divided into a preamble part 71, an address part 72, and a burst part 74 for detecting a tracking deviation, which are arranged in the circumferential direction.
The preamble part 71 is provided for performing PLL processing and AGC processing. The PLL processing is to synchronize a servo signal reproduction clock with a time offset caused by rotational deviation of the magnetic disk 50. The AGC processing is to properly maintain a reproduced signal amplitude. The preamble part 71 continues at least in a substantially arcuate radial direction of the recording layer 56, and is formed as a repetitive pattern area where the magnetization direction is repeatedly inverted along the circumferential direction of the substrate.
In the address part 72, a servo index mark and a servo address mark (SIM/SAM) which are called servo marks, sector data, and cylinder data are formed at the same pitch as the circumferential pitch of the preamble part 71 by Manchester code. A SIM/SAM pattern thereof varies between the inner peripheral area 53a, intermediate peripheral area 53b, and outer peripheral area 53c, depending on radial positions on the magnetic disk 50, as will be described later.
The cylinder data is a pattern, data of which varies for each data track. Therefore, code conversion to Grey code, which minimizes variation from an adjacent track, is performed and is then recorded as Manchester code, in order to reduce the influence of address read errors during a head seek operation.
The burst part 74 is a tracking detection area for detecting an off-track amount of the cylinder address from an on-track state thereof, and comprises four area servo patterns, which are referred to as bursts A, B, C, and D. The area servo patterns are according to an amplitude detection schema, and are also called amplitude servo patterns. Bursts A, B, C, and D are formed, arranged in the circumferential direction, and shifted in the radial directions by a half track pitch from each other, in relation to the data tracks 62. Bursts A, B, C, and D have equal lengths L1 in the circumferential direction.
Each of bursts A, B, C, and D is formed in a pattern which has a predetermined number of crests in the circumferential direction. The number of crests implies a number of signals which are included in each of bursts A, B, C, and D and have substantially equal cycles. Patterns of bursts A, B, C, and D are formed at the same pitch cycle as the pattern of the preamble part 71. A radial cycle is proportional to a variation cycle of an address pattern, or in other words, at a cycle proportional to a data track cycle. In the present embodiment, the patterns of bursts A, B, C, and D each comprise a number of crests which differs depending on radial positions on the magnetic disk 50. Here, the number of crests in each of the patterns differs between the inner peripheral area 53a, intermediate peripheral area 53b, and outer peripheral area 53c.
The preamble part 71, address part 72, and burst part 74 are formed in the same manner as in the servo data pattern in the intermediate peripheral area 53b as described previously. However, SIM/SAM patterns differ between the inner peripheral area 53a, intermediate peripheral area 53b, and outer peripheral area 53c. In the inner peripheral area 53a, bursts A, B, C, and D in the burst part 74 have substantially equal lengths L2 which are greater than lengths L1 of the bursts in the intermediate peripheral area 53b (L2>L1).
The patterns of bursts A, B, C, and D each are formed to have a greater number of recording crests than the patterns in the intermediate peripheral area 53b. In the inner peripheral area 53a, the number of recording crests in each burst pattern is increased from the number of recording crests in the intermediate peripheral area 53b, as a reference, in a manner that positioning accuracy and signal-to-noise ratio which are substantially equivalent to those of the intermediate peripheral area are obtained. The number of recording crests in the pattern of each of bursts A, B, C, and D in the inner peripheral area 53a is set to 1.2 to 1.5 times greater than that of the pattern of each of bursts A, B, C, and D in the intermediate peripheral area 53b.
A servo data pattern in the outer peripheral area 53c of the magnetic disk 50 is formed in the same manner as the servo data pattern in the inner peripheral area 53a as shown in
The patterns of bursts A, B, C, and D each are formed to have a greater number of recording crests than the burst patterns in the intermediate peripheral area 53b. In the outer peripheral area 53c, the number of recording crests in each burst pattern is increased from the number of recording crests in the intermediate peripheral area 53b, as a reference, in a manner that positioning accuracy and the signal-to-noise ratio which are substantially equivalent to those of the intermediate peripheral area are obtained. The number of recording crests in the pattern of each of bursts A, B, C, and D in the outer peripheral area 53a is set to 1.2 to 1.5 times greater than that of the pattern of each of bursts A, B, C, and D in the intermediate peripheral area 53b.
As shown in
In contrast, as shown in
In the embodiment described above, the bursts in the servo data patterns of the magnetic disk are constituted as area-type servo patterns. However, the bursts are not limited to this configuration but may be constituted as phase-type servo patterns.
As shown in
The preamble part 71 and address part 72 are formed in the same manner as in the first embodiment described above. The burst part 74 comprises four bursts A, B, C, and D which are arranged continuously in the circumferential direction. Each of bursts A, B, C, and D is formed as a phase servo pattern constituted by oblique lines, and continues in a substantially arcuate radial direction of the magnetic disk 50. Bursts A, B, C, and D have equal lengths L1 in the circumferential direction. Each of bursts A, B, C, and D is formed in a pattern in which a predetermined number of recording crests are formed, for example, at the same pitch cycle in the circumferential direction as in the preamble part. The patterns of bursts A, B, C, and D each have a number of recording crests which differs depending on radial positions on the magnetic disk 50. Here, the number of crests in each of the patterns differs between the inner peripheral area 53a, intermediate peripheral area 53b, and outer peripheral area 53c.
The preamble part 71, address part 72, and burst part 74 are formed in the same manner as in the servo data pattern in the intermediate peripheral area 53b as described previously. However, SIM/SAM patterns differ between the inner peripheral area 53a, intermediate peripheral area 53b, and outer peripheral area 53c.
As shown in
The patterns of bursts A, B, C, and D each are formed to have a greater number of recording crests than the patterns in the intermediate peripheral area 53b. In the inner peripheral area 53a, the number of recording crests in each burst pattern is increased from the number of recording crests in the intermediate peripheral area 53b, as a reference, in a manner that positioning accuracy and signal-to-noise ratio which are substantially equivalent to those of the intermediate peripheral area are obtained. The number of recording crests in the pattern of each of bursts A, B, C, and D in the inner peripheral area 53a is set to 1.2 to 1.5 times greater than that of the pattern of each of bursts A, B, C, and D in the intermediate peripheral area 53b.
A servo data pattern in the outer peripheral area 53c of the magnetic disk 50 is formed in the same manner as the servo data pattern in the inner peripheral area 53a as shown in
The patterns of bursts A, B, C, and D each are formed to have a greater number of recording crests than the bursts in the intermediate peripheral area 53b. In the outer peripheral area 53c, the number of recording crests in each burst pattern is increased from the number of recording crests in the intermediate peripheral area 53b, as a reference, in a manner that positioning accuracy and signal-to-noise ratio which are substantially equivalent to those of the intermediate peripheral area are obtained. The number of recording crests in the pattern of each of bursts A, B, C, and D in the outer peripheral area 53a is set to 1.2 to 1.5 times greater than that of the pattern of each of bursts A, B, C, and D in the intermediate peripheral area 53b.
In the second embodiment except for features as described above, the magnetic disk has the same configuration as in the first embodiment described above. Also according to the second embodiment, the same operation and effects as the first embodiment can be obtained.
Next, an embodiment of a hard disk drive (HDD) comprising any of the magnetic disks 50 described above will be specifically described as a magnetic disk device.
As shown in
Provided on the base 12 are the magnetic disk 50 described above, a spindle motor 15, plural magnetic heads 33, a head actuator 14, and a voice coil motor (VCM) 16. The spindle motor 15 supports and rotates the magnetic disk. The plural magnetic heads 33 record/reproduce data onto/from the magnetic disk. The head actuator 14 supports the magnetic heads 33 to be freely movable in relation to the magnetic disk 50. The VCM 50 pivots and positions the head actuator 14. Also provided on the base 12 are a ramp load mechanism 18, an inertial latch mechanism 20, and a flexible printed-circuit board unit (hereinafter FPC unit) 17. The ramp load mechanism 18 maintains the magnetic heads 33 at a position apart from the magnetic disk when the magnetic heads 33 are moved to outermost periphery of the magnetic disk 50. The inertial latch mechanism 20 maintains the head actuator 14 at a retracted position. The FPC unit 17 is equipped with circuit components such as a preamplifier, etc.
As described previously, the magnetic disk 50 is a magnetic recording medium on which magnetic data is written according to the magnetic-transfer recording schema. For example, the magnetic disk 50 is formed to have a diameter of 1.8 or 2.5 inches. The magnetic disk 50 is engaged coaxially with an unillustrated hub of the spindle motor 15, and is secured to the hub by a clamp spring 21. The magnetic disk 50 is supported by the spindle motor 15 as a drive section, and is rotated at a predetermined speed in an arrow direction B.
The head actuator 14 comprises a bearing part 24, two arms 27, and suspensions 30. The bearing part 24 is secured to the bottom wall of the base 12. The two arms 27 are attached to a bearing assembly of the bearing part 24. The suspensions 30 respectively extend from the arms. The magnetic heads 33 are supported at distal ends of the suspensions 30. The arms 27, suspensions 30, and magnetic heads 33 are supported to freely rotate about the bearing part 24. The magnetic heads 33 are respectively provided with a down head and an up head. The down head faces a top-surface recording layer of the magnetic disk 50. The up head faces a back-surface recording layer. Each of the magnetic heads 33 comprises a slider and a magnetic head element which comprises a read element (GMR element) and a write element and is formed on the slider.
The VCM 16 comprises a voice coil, a pair of yokes 38, and an unillustrated magnet. The voice coil is provided on the head actuator 14. The pair of yokes 38 are secured to the base 12 and face the voice coil. The magnet is secured to one of the yokes. The VCM 16 generates rotational torque on an arm 27 about a bearing part 24, and moves the magnetic heads 33 in a radial direction of the magnetic disk 50.
The FPC unit 17 comprises a rectangular substrate body 34 secured to a bottom wall of the base 12. Plural electronic components and connectors are mounted on the substrate body. The FPC unit 17 comprises a main flexible-printed-circuit board 36 having a band shape. Each of the magnetic heads 33 supported by the head actuator 14 is electrically connected to the FPC unit 17 through an unillustrated relay FPC provided on the arms 27 and through the main flexible-printed-circuit board 36.
The magnetic disk 50 is built in the base 12 in a manner that the top and back surfaces of the disk are aligned in a direction along which a locus of movement of each magnetic head 33 of the HDD 10 substantially corresponds to the arcuate shape of each servo area 60. Specifications of the magnetic disk 50 comply with outer and inner diameters and recording/reproducing characteristics which are adequate for the HDD 10.
The spindle motor 15, VCM 16, and printed-circuit board (PCB) 40 are secured to an outer surface of the bottom wall of the base 12 through the FPC unit 17, and face the bottom wall of the base.
As shown in
The MPU 43 is a controller for a drive system of the drive, and is configured to comprise a ROM, a RAM, a CPU, and a logic processor which constitute a head positioning control system according to the present embodiment. The logic processor is an operation processing section constituted by a hardware circuit and is used for high-speed operation processing. Operating software (firmware) is stored in the ROM, and the MPU controls the drive in accordance with the firmware.
The HDC 41 is an interface section in the HDD 10, which interfaces between the disk drive and a host system such as a personal computer, and exchanges data with the MPU 43, read/write channel IC 42, and motor driver IC 44. Thus, the HDC 41 controls the whole HDD 10.
The read/write channel IC 42 is a head signal processor relating to reading/writing, and is constituted by a circuit which switches channels of a head amplifier IC and processes recorded and reproduced signals in reading/writing. The motor driver IC 44 is a driver for driving the VCM 16 and spindle motor 15. The motor driver IC 44 controls driving of the spindle motor 15 so as to rotate constantly, and supplies the VCM with a VCM operation amount as a current value from the MPU 43, to drive the head actuator 14. The magnetic heads 33 read servo data from the magnetic disk 50, and provides the CPU 43 with the data.
A cylinder number or a radial position range which changes a read setting for a number of recording crests per burst, depending on radial positions on the magnetic disk 50, can be arbitrarily determined. The cylinder number or radial position range for switching a read setting for a number of recording crests per burst may be changed in a manner as follows. That is, plural SIM/SAM patterns are associated in advance with numbers of recording crests in burst patterns. A SIM/SAM pattern is determined by the magnetic heads 33, and a number of recording crests is changed to an associated number of recording crests. Data for switching a read setting for the number of recording crest per burst may be stored in the ROM or recorded on a system area of the magnetic disk 50. The read setting may be changed by reading such data at an arbitrary timing.
According to the present embodiment, data which associates SIM/SAM patterns for the magnetic disk 50 respectively with corresponding numbers of recording crests in burst patterns is stored as setting change data in the ROM. The MPU 43 detects a read output of servo data from the magnetic heads 33, and changes a read setting for the number of recording crests per burst, depending on radial positions of the magnetic disk 50, e.g., an inner peripheral area, an intermediate peripheral area, and an outer peripheral area.
For example, as shown in
Alternatively, the MPU 43 may control the number of recording crests to read according to a schema as shown in
According to the HDD configured as described above, even when a magnetic disk of the magnetic transfer type is used, loss of servo data due to a low signal-to-noise ratio caused by an azimuth angle can be compensated for. Accordingly, reduction of magnetic head positioning accuracy caused by decreased head output can be suppressed. In this manner, head positioning accuracy increases, and there is provided a magnetic disk device capable of increasing a recording volume.
While certain embodiments have been described, these embodiments have been presented by way of example only, and are not intended to limit the scope of the inventions. Indeed, the novel embodiments described herein may be embodied in a variety of other forms; furthermore, various omissions, substitutions and changes in the form of the embodiments described herein may be made without departing from the spirit of the inventions. The accompanying claims and their equivalents are intended to cover such forms or modifications as would fall within the scope and spirit of the inventions.
Although the above embodiments employ a magnetic disk of a vertical-magnetic recording type, the present invention is not limited to this type but is applicable also to a magnetic recording medium of a horizontal (in-plane) magnetic recording type. The invention is also applicable to a magnetic recording medium of a discrete track recording (DTR) type. Bursts of servo data are not limited to area patterns and phase patterns but may be other burst patterns such as Null patterns. Furthermore, a number of magnetic disks built into an HDD is not limited to one but may be increased according to necessity.
Number | Date | Country | Kind |
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2010-148320 | Jun 2010 | JP | national |