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
  • G11B5/48—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
  • G11B5/60—Fluid-dynamic spacing of heads from record-carriers
  • G11B5/6005—Specially adapted for spacing from a rotating disc using a fluid cushion

Definitions

• Disk drives are commonly used in workstations, personal computers, laptops and other computer systems to store large amounts of data that are readily available to a user.
• a disk drive comprises a magnetic disk that is rotated by a spindle motor.
• the surface of the disk is divided into a series of data tracks that extend circumferentially around the disk. Each data track can store data in the form of magnetic transitions on the disk surface.
• the head is mounted by a rotary actuator and is selectively positioned by the actuator over a preselected data track of the disk to enable the transducer to either read data from or write data to the preselected data track of the disk, as the disk rotates below the transducer.
• the head includes a slider forming an air bearing surface that causes the transducer to fly above the data tracks of the disk surface due to fluid currents caused by rotation of the disk. Thus, the transducer does not physically contact the disk surface during normal operation of the disk drive.
• the amount of distance that the transducer flies above the disk surface is referred to as the "fly height.”
• One advantageous type of head structure that operates at a fly height over the disk surface is a Transverse Pressure Contour (TPC) head.
• TPC Transverse Pressure Contour
• Current disk drive designs using a TPC head seek to limit the fly height to approximately 2 ⁇ inches above the disk surface. Any contact between the head and the disk surface may result in damage to the disk or head. Accordingly, it is important to maintain an adequate fly height whenever the actuator positions the transducer over data tracks while the disk is rotating.
• fly height varies over the various tracks of the disk, as a function of the radial position of the actuator.
• the fly height is greater than at other data tracks. Accordingly, the data signal is not as strong as possible at all data tracks.
• Several designs have been proposed to improve the stability of fly height of the slider.
• recesses are provided in the face of the slider facing the rotating disk to provide for sub-ambient pressure (i.e., less than 1 atm of pressure) between portions of the slider and the disk causing the slider to be pulled toward the rotating disk during operation.
• sub-ambient pressure i.e., less than 1 atm of pressure
• the sub-ambient pressure effects counteract, to some extent, the operation of the slider tending to lift the head from the disk surface.
• the net result is a tighter, stiff control over the fly height, that ideally resists changes in fly height.
• Each of the first and second rails includes a thigh region extending at an angle from the leading edge to a lateral side of the slider, a foot region extending at an angle from the lateral side of the slider toward the trailing edge of the slider, and a knee region at the lateral side of the slider coupling the foot region to the thigh region.
• First and second thigh recesses are located towards the lateral side of each of the respective thigh regions of the first and second rails.
• First and second foot recesses are located on the bottom side of the slider towards the lateral side of each respective foot region of the first and second rails.
• a central recess is located on the bottom side of the slider between the thigh, knee, and foot regions of the first and second rails.
• the first and second rails can have an approximately equal, uniform height, while the first and second thigh recesses, first and second foot recesses, and the central recess can have an approximately equal, uniform depth.
• a taper can be provided at a leading edge of the slider for channeling air flow to the bottom side of the slider.
• a front section can be provided which extends from one lateral side of the slider to the opposing, lateral side of the slider.
• the front section and one or more tails can have a uniform height equal to that of the first and second rails.
• a central recess for the slider is fabricated having an approximately uniform depth.
• the uniform depth of the central recess is chosen such that a flying height of the slider over the tracks of the rotating disk is most insensitive to fluctuations in the chosen uniform depth.
• This uniform depth can be chosen so that the flying height as a function of recess depth is approximately at a minimum for all tracks of the rotating disk.
• the slider design of the present invention provides for a more uniform flying height across the tracks of the disk.
• the addition of the one or more tails allows for a better control of the roll of the slider.
• Fig. lc shows a top view of a conventional catamaran slider having one and two tails, respectively, to control flying height and roll angle according to an embodiment of the present invention.
• Fig. 3 is a overhead view of an assembly for positioning a slider over the innermost track of a disk.
• Fig. 4 is a overhead view of an assembly for positioning a slider over the middle track of a disk.
• Fig. 5 is a overhead view of an assembly for positioning a slider over the outermost track of a disk.
• Fig. 6 is a graph of flying height versus recess depth of a slider.
• the slider 1 includes a taper 3 at the leading edge of the slider 1 which channels air flow underneath the slider 1.
• the width of the slider 1 and the taper 3 is 60 mils (i.e., 0.06 inches) while the length and depth of the taper 3 is 8 mils.
• the taper 3 can lead into a front section 4.
• two rails 5, 7 are provided that vary significantly from the catamaran design known in the art.
• Each rail 5, 7 includes three major sections: a thigh section 5a, 7a; a knee section 5b, 7b; and a foot section 5c, 7c.
• the front section 4 and all sections 5a-c, 7a-c of the rails 5, 7 of the slider 1 are at the same height (e.g., in this embodiment, the height of the slider is 17 mils) .
• a magnetic head (not shown specifically in Figs. 1-2 is coupled at the rear of the slider 1, proximate to the foot region 5c (denoted “ACTIVE RAIL” in Fig. 1) .
• the slider 1 is shown mounted to an arm 19 and an actuator 21, which positions the slider 1 and magnetic head over a desired track.
• the slider 1 is positioned proximately to the innermost track of the disk 17.
• the thigh regions 5a, 7a of the first and second rails 5, 7 extend from the front, middle part of the slider 1 outward to two opposing sides of the slider where the knee sections 5b, 7b meet the sides of the slider.
• the angle that the thigh regions 5a, 7a make with the forward region 4 is designed to be approximately the same as the slider skew angle when the slider is present at the innermost track.
• the innermost track is also known as the contact start- stop (CSS) zone.
• the disk surface velocity is at its lowest.
• the orientation of the thigh regions 5a, 7a assists in preventing pressure underneath the first and second rails 5, 7 from leaking to the sides of the slider 1 (thus causing the slider to fly at a lower than desired height) .
• the slider 1 is positioned approximately at the middle track (i.e., the track at a mean distance between the inner and outer tracks) .
• the middle track i.e., the track at a mean distance between the inner and outer tracks
• the skew angle is approximately zero. Because of the design of the thigh regions 5a, 7a of the slider 1, pressure leakage to the sides of these regions is greater. The loss of pressure due to leakage at the thigh regions 5a, 7a is compensated by the increase in surface velocity of the disk 17.
• the flying height of the slider 1 would be at its greatest at the middle track except for the action of the foot recesses 14, 15, which act to reduce the area of pressurization for the slider 1 and, thus, reducing the lift force generated at the foot sections 5c, 7c of the first and second rails 5, 7.
• the slider l and magnetic head are placed over the outermost track (hereinafter referred to the outer diameter or "OD") .
• the large skew angle at the OD causes a greater amount of pressure to leak to the sides of the rails 5, 7. Because of the design of the thigh regions 5a, 7a of the slider l, very little pressure is generated at these regions because of the relatively small pad length. Most of the pressure under the slider is generated under the knee regions 5b, 7b of the slider 1. Although, the pad area below the knee is small, the large disk surface velocity at the OD gives generates enough pressure to under the rails 5, 7 of the slider 1 to maintain a constant flying height.
• the recess regions 11-15 generate sub-ambient pressure that pulls the slider towards the disk surface.
• the majority of the sub-ambient pressure is formed at the central recess 11.
• the thigh recesses 12, 13 provide extra roll stiffness for the slider l.
• the foot recesses 14, 15 reduce the effective pressurization area at the foot of the slider 1 so that it will not fly too high above the disk surface at a near zero skew angle.
• the foot recesses 14, 15 reshape the foot regions 5c, 7c, of the rails 5, 7 so that these regions are parallel to the incoming air when the slider 1 is at an outer track.
• the flying height of the outer rail i.e., rail 5
• the shape of the inner rail i.e., rail 7
• tail(s) 2 By optimizing the length and orientation of the tail(s) 2, the effect of suction force on the roll angle of the slider 1 can be controlled.
• the dashed lines in Figs, la and lb show possible orientations and lengths for the tails (s) 2. Also, the use of tail(s) 2 prevents the coupling of the flying height of one rail to the change in the dimension of the other.
• a conventional catamaran slider is shown having tails 4 as described above.
• the depth of the central recess 11 can have a substantial effect on flying height over all tracks of a disk. In high altitude environments, the change in pressure and the mean-free path of air can also have an effect on flying height.
• the range of flying height values i.e., the difference between the maximum and minimum flying height of the head over all tracks of a disk
• the range of flying height values can be substantially smaller than with typical catamaran- ype sliders. Referring to Fig. 6, a graph is shown having flying height along the Y-axis and recess depth along the X-axis for the ID, middle diameter ("MD"), and OD (i.e., flying height is shown as a function of recess depth) .
• the flying height for the slider will fall along steep slopes of the ID, MD, and OD curves. This will cause greater flying height sensitivity depending on the recess depth chosen and the altitude at which the slider is used. If a recess depth is chosen when the slopes of the ID, MD, and OD curves are at a minimum (i.e., the uniform depth is chosen such that the flying height as a function of recess depth is approximately at a minimum for all tracks of the rotating disk -- in the 110-150 microinches range) , the sensitivity of the slider to recess depth variations due to tolerances and operating altitude is minimized. Another advantage of choosing the recess using the aforementioned technique is that the air- bearing stiffness is maximized which helps in reducing the flying height sensitivity further.

Landscapes

• Adjustment Of The Magnetic Head Position Track Following On Tapes (AREA)

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Citations (3)

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• 1995
  • 1995-12-18 JP JP8519891A patent/JPH11500558A/ja not_active Ceased
  • 1995-12-18 CN CN95196685A patent/CN1076500C/zh not_active Expired - Fee Related
  • 1995-12-18 DE DE69527085T patent/DE69527085T2/de not_active Expired - Fee Related
  • 1995-12-18 WO PCT/US1995/016272 patent/WO1996019801A1/en not_active Ceased
  • 1995-12-18 KR KR1019970704183A patent/KR100366673B1/ko not_active Expired - Fee Related
  • 1995-12-18 EP EP95944105A patent/EP0799477B1/en not_active Expired - Lifetime
• 1996
  • 1996-09-04 US US08/707,827 patent/US5739981A/en not_active Expired - Fee Related

Patent Citations (3)

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