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WO1998016922A1 - Systeme asservi pour lecteur de disques utilisant des signaux thermiques - Google Patents

Systeme asservi pour lecteur de disques utilisant des signaux thermiques Download PDF

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Publication number
WO1998016922A1
WO1998016922A1 PCT/US1997/018325 US9718325W WO9816922A1 WO 1998016922 A1 WO1998016922 A1 WO 1998016922A1 US 9718325 W US9718325 W US 9718325W WO 9816922 A1 WO9816922 A1 WO 9816922A1
Authority
WO
WIPO (PCT)
Prior art keywords
disc
servo
magnetoresistive element
user data
regions
Prior art date
Application number
PCT/US1997/018325
Other languages
English (en)
Inventor
Dallas W. Meyer
Subrahmanyan Nagarajan
Original Assignee
Seagate Technology, Inc.
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Priority claimed from US08/793,327 external-priority patent/US5999360A/en
Application filed by Seagate Technology, Inc. filed Critical Seagate Technology, Inc.
Priority to JP51846498A priority Critical patent/JP2001524244A/ja
Priority to DE19782063T priority patent/DE19782063T1/de
Priority to GB9906721A priority patent/GB2333176B/en
Publication of WO1998016922A1 publication Critical patent/WO1998016922A1/fr
Priority to HK99105877A priority patent/HK1021241A1/xx

Links

Classifications

    • G—PHYSICS
    • G11—INFORMATION STORAGE
    • G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
    • G11B5/00—Recording by magnetisation or demagnetisation of a record carrier; Reproducing by magnetic means; Record carriers therefor
    • G11B5/012—Recording on, or reproducing or erasing from, magnetic disks
    • G—PHYSICS
    • G11—INFORMATION STORAGE
    • G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
    • G11B5/00—Recording by magnetisation or demagnetisation of a record carrier; Reproducing by magnetic means; Record carriers therefor
    • G11B5/48—Disposition or mounting of heads or head supports relative to record carriers ; arrangements of heads, e.g. for scanning the record carrier to increase the relative speed
    • G11B5/54—Disposition or mounting of heads or head supports relative to record carriers ; arrangements of heads, e.g. for scanning the record carrier to increase the relative speed with provision for moving the head into or out of its operative position or across tracks
    • G11B5/55—Track change, selection or acquisition by displacement of the head
    • G11B5/5521—Track change, selection or acquisition by displacement of the head across disk tracks
    • G11B5/5526—Control therefor; circuits, track configurations or relative disposition of servo-information transducers and servo-information tracks for control thereof
    • G—PHYSICS
    • G11—INFORMATION STORAGE
    • G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
    • G11B5/00—Recording by magnetisation or demagnetisation of a record carrier; Reproducing by magnetic means; Record carriers therefor
    • G11B5/48—Disposition or mounting of heads or head supports relative to record carriers ; arrangements of heads, e.g. for scanning the record carrier to increase the relative speed
    • G11B5/58—Disposition or mounting of heads or head supports relative to record carriers ; arrangements of heads, e.g. for scanning the record carrier to increase the relative speed with provision for moving the head for the purpose of maintaining alignment of the head relative to the record carrier during transducing operation, e.g. to compensate for surface irregularities of the latter or for track following
    • G11B5/596—Disposition or mounting of heads or head supports relative to record carriers ; arrangements of heads, e.g. for scanning the record carrier to increase the relative speed with provision for moving the head for the purpose of maintaining alignment of the head relative to the record carrier during transducing operation, e.g. to compensate for surface irregularities of the latter or for track following for track following on disks
    • G11B5/59627—Aligning for runout, eccentricity or offset compensation
    • G—PHYSICS
    • G11—INFORMATION STORAGE
    • G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
    • G11B5/00—Recording by magnetisation or demagnetisation of a record carrier; Reproducing by magnetic means; Record carriers therefor
    • G11B5/48—Disposition or mounting of heads or head supports relative to record carriers ; arrangements of heads, e.g. for scanning the record carrier to increase the relative speed
    • G11B5/58—Disposition or mounting of heads or head supports relative to record carriers ; arrangements of heads, e.g. for scanning the record carrier to increase the relative speed with provision for moving the head for the purpose of maintaining alignment of the head relative to the record carrier during transducing operation, e.g. to compensate for surface irregularities of the latter or for track following
    • G11B5/596—Disposition or mounting of heads or head supports relative to record carriers ; arrangements of heads, e.g. for scanning the record carrier to increase the relative speed with provision for moving the head for the purpose of maintaining alignment of the head relative to the record carrier during transducing operation, e.g. to compensate for surface irregularities of the latter or for track following for track following on disks
    • G11B5/59633—Servo formatting
    • G—PHYSICS
    • G11—INFORMATION STORAGE
    • G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
    • G11B5/00—Recording by magnetisation or demagnetisation of a record carrier; Reproducing by magnetic means; Record carriers therefor
    • G11B5/48—Disposition or mounting of heads or head supports relative to record carriers ; arrangements of heads, e.g. for scanning the record carrier to increase the relative speed
    • G11B5/58—Disposition or mounting of heads or head supports relative to record carriers ; arrangements of heads, e.g. for scanning the record carrier to increase the relative speed with provision for moving the head for the purpose of maintaining alignment of the head relative to the record carrier during transducing operation, e.g. to compensate for surface irregularities of the latter or for track following
    • G11B5/596—Disposition or mounting of heads or head supports relative to record carriers ; arrangements of heads, e.g. for scanning the record carrier to increase the relative speed with provision for moving the head for the purpose of maintaining alignment of the head relative to the record carrier during transducing operation, e.g. to compensate for surface irregularities of the latter or for track following for track following on disks
    • G11B5/59683—Disposition or mounting of heads or head supports relative to record carriers ; arrangements of heads, e.g. for scanning the record carrier to increase the relative speed with provision for moving the head for the purpose of maintaining alignment of the head relative to the record carrier during transducing operation, e.g. to compensate for surface irregularities of the latter or for track following for track following on disks for magnetoresistive heads
    • G—PHYSICS
    • G11—INFORMATION STORAGE
    • G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
    • G11B5/00—Recording by magnetisation or demagnetisation of a record carrier; Reproducing by magnetic means; Record carriers therefor
    • G11B5/74—Record carriers characterised by the form, e.g. sheet shaped to wrap around a drum
    • G11B5/82—Disk carriers
    • G—PHYSICS
    • G11—INFORMATION STORAGE
    • G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
    • G11B5/00—Recording by magnetisation or demagnetisation of a record carrier; Reproducing by magnetic means; Record carriers therefor
    • G11B2005/0002—Special dispositions or recording techniques
    • G11B2005/0005—Arrangements, methods or circuits
    • G11B2005/0021—Thermally assisted recording using an auxiliary energy source for heating the recording layer locally to assist the magnetization reversal

Definitions

  • the resistance of the MR element is also dependent on a number of other factors, including temperature.
  • the bias current also generates about 10 to 100 mW power in the form of heat within the element.
  • the heat thermally dissipates into the head as well as across the interface into the recording disc.
  • the amount of heat dissipated across the interface into the disc is a function of disc spacing between the disc and MR element. At small head/disc spacings (low flying heights), more heat is dissipated to the disc than when the spacing is large (high flying heights).
  • the resistance of the MR element is a function of magnetic field strength, as well as thermal dissipation due to a function of disc/head spacing.
  • data are recorded on concentric tracks of magnetic discs, and the
  • a dedicated servo system employing six discs (twelve disc surfaces) with one of the surfaces dedicated to the servo data, more than 8% of the total area of all disc surfaces is dedicated to servo data.
  • servo data may comprise 8 to 15% of the length of a track, and as much as 12% of the entire area of a disc. Because the servo data represents such a significant area of the disc, it is desirable to reduce that area without adversely affecting the operation of the disc drive.
  • Servo data are ordinarily recorded at significant lower frequencies than user data.
  • user data may be in the MegaHertz range (e.g., 20 MHz and higher)
  • servo data is ordinarily in the KiloHertz range (typically below about 20 KHz).
  • data both servo and user data
  • the present invention is directed to a servo system for a disc drive in which the servo data are recorded as contour elements arranged in a pattern along at least one of the concentric tracks and having a height from the surface of the disc so that the spacing between the magnetoresistive element and the contour elements is different from a nominal spacing of the magnetoresistive element and the surface of the recording disc.
  • Variations in head/disc spacing caused by the undulating contour of the disc surface affects the thermal dissipation characteristics of the MR read head, thereby altering the resistance of the MR element in accordance with the pattern of the contour elements representing servo data.
  • the resistance of the MR element is altered due to changing magnetic field strength from user data recorded on the moving disc.
  • the resistance of the magnetoresistive element has a first component based on the magnetic state confronting the magnetoresistive element and a second component based on the temperature of the magnetoresistive element.
  • a bias current through the magnetoresistive element provides a signal based on the resistance of the magnetoresistive element.
  • a demodulator responds to the signal from the magnetoresistive element to provide a user data signal and a separate servo signal.
  • the contour elements are bumps or pits extending above or into the nominal disc surface.
  • the contour elements are formed as dipoles along the track length, each dipole having a bump and a pit. In other embodiments, the contour elements are centered along the track center, or are positioned between track.
  • FIG. 1 is a diagram of a disc drive illustrating the physical relationship between the actuator arm, head and rotating disc.
  • FIG. 2 is a plan view illustrating one embodiment of a patterned configuration on a disc for servo control in accordance with the present invention.
  • FIG. 3 is section view taken at line 3-3 in FIG. 2.
  • FIGS. 4 A and 4B are waveforms illustrating the servo signal achieved with the embodiment illustrated in FIGS. 2 and 3.
  • FIGS. 7 A and 7B are waveforms illustrating the servo signal achieved with the embodiment illustrated in FIGS. 5 and 6.
  • FIG. 10 is a plan view illustrating another embodiment of a patterned configuration on a disc for servo control in accordance with the present invention.
  • FIG. 12 is a plan view illustrating yet another embodiment of a patterned configuration on a disc for servo control in accordance with the present invention.
  • the resistance of the MR element due to temperature is directly proportional to the spacing of the MR element from the adjacent magnetic disc. More particularly, the resistance due to temperature can be expressed by the following equation:
  • the signal recovered from the MR head includes a component at user data frequency representing user data and a component at servo data frequency representing servo data.
  • a demodulator may separate user data from servo data.
  • the first and second regions are in the form of contour elements of different heights, wherein changes in the spacing between the magnetoresistive head and the contour elements causes changes in the thermal conductivity of the heat dissipation path through the disc.
  • the contour elements may be in the form of dipoles represented by bumps and pits in a nominal surface of the disc, or may be in the form of bumps or pits alone in the nominal surface of the disc.
  • each of these dipole contour elements 50 are centered along the center of each track 40, 42 on the disc so that head 26 flying adjacent the track containing the contour elements first crosses a pit 54 and then a bump 52.
  • Figs. 4 A and 4B are waveforms illustrating the time-varying electrical resistance of the MR element of head 26 due to temperature as the head crosses contour elements 50. More particularly, the bias current through the MR element of head 26 generates heat which is in part dissipated along the path that includes the space between head 26 and the surface of disc 32 confronting the head. Since the bias current is constant, the quantity of heat generated by the MR head is also constant.
  • Fig. 5 illustrates a configuration of contour elements comprising individual bumps 52 and individual pits 54.
  • the bumps 52 and pits 54 along each side of tracks 40, 42, with a concentric row of bumps 52 on one side of track center and a concentric row of pits 54 on the other side of track center.
  • the bumps and pits are radially positioned such that a bump is radially between two pits and a pit is radially between two bumps, and so on.
  • the pits and bumps are positioned along the track length such that each pit or bump is offset from track center and the track centerline passes between radially aligned contiguous elements 52 and 54.
  • signals resulting from heat retained in the head will be constant, as shown by waveform 62 in Fig. 7 A.
  • the head is off track center, heat will dissipate unequally at the bumps and pits, resulting in a series of signals, resembling half sinusoidal signals 64, as shown in Fig. 7B.
  • a series of positive signals will result, as shown in Fig. 7B, the magnitude of which is representative of the amount of offset of the head from track center.
  • a series of negative signals will result whose magnitude represents the amount of offset of the head from track center.
  • Figs. 8 and 9 illustrate yet different configurations of a contour element in which the bumps 52 and pits 54 are cylindrical cavities into or posts rising from the nominal surface 56 of the disc.
  • Figs. 10 and 11 illustrate yet a different shape for the contour elements wherein the contour elements are elongated along the track length at the servo frequency so that each transition between a peak 52 and a pit 54 is at the servo frequency.
  • the pits 54 are conveniently formed by laser machining or other suitable etching technique, leaving the bumps 52 at the nominal surface 56 of the disc.
  • the servo contour elements have thus far been described as being arranged on or directly off track center, it is understood that the servo contour elements may also straddle the disc center.
  • the dipole elements such as shown in greater detail in Fig. 2 and 3, are radially offset one-half track so that the track center line 40 intersects all of the dipole contour elements equally, midway between the center and an edge of each bump 52 or pit 54. It would be appreciated that a head that is directly on track center will read each of the dipole elements equally producing a balanced signal, similar to that illustrated in Fig.
  • the servo contour elements have thus far been described as a series of evenly spaced bumps and/or pits arranged at the servo frequency, it will be appreciated that the bumps and/or pits may be arranged to convey yet additional information, such as sector, track (cylinder), and disc (head) identification. Further, the bumps and pits may be selectively arranged to convey the information. As already described, the contour elements are arranged to provide track position error information for track centering purposes. In any case, the contour elements are arranged so that when the disc is rotated at its predetermined or design rotational velocity, the information contained in the contour elements is recovered at the design servo frequency, different from user data frequency.
  • the magnetic head reading the disc having contour elements as herein described produces a signal represented in Figs. 4 or 7, comprising low frequency servo data frequency modulated with the high frequency user data, as shown in Fig. 13 A and 13B (which illustrate user data signal 66 modulated with the on-track servo signals of Figs. 4A and 7 A, respectively).
  • the signal thus produced from the head is amplified by pre-amplifier 70 and separated by demodulator 72.
  • the user data is recovered at significantly higher frequencies (20 - 100 MHz) than servo data (5 - 20 KHz).
  • Demodulator 72 demodulates the signal from preamplifier 70 to separate the low frequency servo data to output 74 from the higher frequency user data to output 76 for processing in a manner well-known in the art.
  • the contour elements cause changes in the spacing between the recording surface of the magnetic disc and the read head, resulting in changes of the distance between the recorded magnetic information on the disc and the read head confronting the disc, the peak-to-peak value of the data signals only slightly varies as a result of the changes of spacing. Hence, amplitude modulation of the magnetic signal is negligible.
  • the bumps and pits forming the contour elements are formed of the high thermal conductivity magnetic material forming the disc. Heat reaching the disc is dissipated through the high thermally conductive material.
  • the different spacings of the contour elements from the magnetoresistive element also provide thermal dissipation paths of different thermal conductivity, due to the different air gap between the different contour elements on the disc and the magnetoresistive element.
  • the thermal dissipation path formed between the disc and the head is in parallel with the thermal dissipation path from the head to the head support and the air surrounding the head.
  • the amount of heat dissipated from the head depends, in part, on the thermal conductivity of the dissipation path through the disc, which in turn depends on the contour elements on the disc.
  • FIGS. 15 A, 15B and 15C illustrate contour elements 52 and 54, as in FIGS. 3, 8 and 9 having a layer 80 of low thermally conductive (high thermal insulation) material over at least the pits 54 and preferably also over the nominal surface 56 of the disc.

Landscapes

  • Moving Of The Head To Find And Align With The Track (AREA)
  • Magnetic Heads (AREA)
  • Adjustment Of The Magnetic Head Position Track Following On Tapes (AREA)

Abstract

L'invention concerne un lecteur de disques magnétiques, qui a un élément (26) magnétorésistant servant à lire des données utilisateur sur des pistes concentriques d'un disque (32) d'enregistrement magnétique rotatif. La résistance de l'élément magnétorésistant dépend d'un champ magnétique provenant des données utilisateur et de la température de l'élément magnétorésistant. La chaleur générée par le courant de polarisation et transmise par la tête est en partie dissipée à travers le disque, la quantité de chaleur dissipée étant représentative de l'espacement disque/tête. La surface du disque d'enregistrement a des éléments (50, 52, 54) de contour qui sont disposés selon un motif représentant des données d'asservissement, les éléments de contour ayant une hauteur telle que l'espacement entre l'élément magnétorésistant et les éléments de contour est différent de l'espacement entre l'élément magnétorésistant et une surface nominale du disque d'enregistrement. En conséquence, un signal (66) modulé provenant de la tête contient une composante représentative de données utilisateur et une composante représentative de données d'asservissement.
PCT/US1997/018325 1996-10-15 1997-10-10 Systeme asservi pour lecteur de disques utilisant des signaux thermiques WO1998016922A1 (fr)

Priority Applications (4)

Application Number Priority Date Filing Date Title
JP51846498A JP2001524244A (ja) 1996-10-15 1997-10-10 熱信号を採用したディスクドライブサーボシステム
DE19782063T DE19782063T1 (de) 1996-10-15 1997-10-10 Servosystem für Plattenlaufwerke unter Verwendung von thermischen Signalen
GB9906721A GB2333176B (en) 1996-10-15 1997-10-10 Disc drive servo system employing thermal signals
HK99105877A HK1021241A1 (en) 1996-10-15 1999-12-14 Disc drive servo system employing thermal signals

Applications Claiming Priority (4)

Application Number Priority Date Filing Date Title
US2837196P 1996-10-15 1996-10-15
US60/028,371 1996-10-15
US08/793,327 1997-03-14
US08/793,327 US5999360A (en) 1996-10-15 1997-03-14 Disc drive servo system employing thermal signals

Publications (1)

Publication Number Publication Date
WO1998016922A1 true WO1998016922A1 (fr) 1998-04-23

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ID=26703615

Family Applications (1)

Application Number Title Priority Date Filing Date
PCT/US1997/018325 WO1998016922A1 (fr) 1996-10-15 1997-10-10 Systeme asservi pour lecteur de disques utilisant des signaux thermiques

Country Status (5)

Country Link
JP (1) JP2001524244A (fr)
DE (1) DE19782063T1 (fr)
GB (1) GB2333176B (fr)
HK (1) HK1021241A1 (fr)
WO (1) WO1998016922A1 (fr)

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US8665549B2 (en) 2011-09-29 2014-03-04 HGST Netherlands B.V. Method for creating burst magnitude servo patterns with unipolar bits on a magnetic media of a magnetic data recording system

Citations (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5527110A (en) * 1993-04-30 1996-06-18 International Business Machines Corporation Method and apparatus for detecting asperities on magnetic disks using thermal proximity imaging

Family Cites Families (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPH02232803A (ja) * 1989-03-06 1990-09-14 Nec Corp 磁気ヘッド

Patent Citations (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5527110A (en) * 1993-04-30 1996-06-18 International Business Machines Corporation Method and apparatus for detecting asperities on magnetic disks using thermal proximity imaging

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US8665549B2 (en) 2011-09-29 2014-03-04 HGST Netherlands B.V. Method for creating burst magnitude servo patterns with unipolar bits on a magnetic media of a magnetic data recording system

Also Published As

Publication number Publication date
HK1021241A1 (en) 2000-06-02
GB9906721D0 (en) 1999-05-19
JP2001524244A (ja) 2001-11-27
GB2333176B (en) 2000-12-20
GB2333176A (en) 1999-07-14
DE19782063T1 (de) 1999-10-14

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