Dynamic magnetic information storage or retrieval – Fluid bearing head support – Disk record
Reexamination Certificate
2000-04-13
2003-02-04
Renner, Craig A. (Department: 2652)
Dynamic magnetic information storage or retrieval
Fluid bearing head support
Disk record
C360S235800, C360S236000, C360S236100, C360S236200, C360S236300
Reexamination Certificate
active
06515831
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to disc drive data storage systems and, more particularly, to a disc drive data storage system having a slider, which reduces stiction with the disc surface while providing sufficient bearing stiffness.
Disc drives of the “Winchester” and optical types are well known in the industry. Such drives use rigid discs, which are coated with a magnetizable medium for storage of digital information in a plurality of circular, concentric data tracks. The discs are mounted on a spindle motor, which causes the discs to spin and the surfaces of the discs to pass under respective hydrodynamic (e.g. air) bearing disc head sliders. The sliders carry transducers, which write information to and read information from the disc surfaces.
An actuator mechanism moves the sliders from track-to-track across the surfaces of the discs under control of electronic circuitry. The actuator mechanism includes a track accessing arm and a suspension for each head gimbal assembly. The suspension includes a load beam and a gimbal. The load beam provides a load force which forces the slider toward the disc surface. The gimbal is positioned between the slider and the load beam, or is integrated in the load beam, to provide a resilient connection that allows the slider to pitch and roll while following the topography of the disc.
The slider includes a bearing surface, which faces the disc surface. As the disc rotates, the disc drags air under the slider and along the bearing surface in a direction approximately parallel to the tangential velocity of the disc. As the air passes beneath the bearing surface, air compression along the air flow path causes the air pressure between the disc and the bearing surface to increase, which creates a hydrodynamic lifting force that counteracts the load force and causes the slider to lift and fly above or in close proximity to the disc surface.
One type of slider is a “self-loading” air bearing slider, which includes a leading taper (or stepped-taper), a pair of raised side rails, a cavity dam and a subambient pressure cavity. The leading taper is typically lapped or etched onto the end of the slider that is opposite to the recording head. The leading taper pressurizes the air as the air is dragged under the slider by the disc surface. An additional effect of the leading taper is that the pressure distribution under the slider has a first peak near the taper end or “leading edge” due to a high compression angle of the taper or step, and a second peak near the recording end or “trailing edge” due to a low bearing clearance for efficient magnetic recording. This dual-peak pressure distribution results in a bearing with a high pitch stiffness.
The bearing clearance between the slider and the disc surface at the recording head is an important parameter to disc drive performance. Slider bearings in computer hard drives have three degrees of freedom, including vertical motion, pitch rotation and roll rotation. The three degrees of freedom are associated with three vibration modes. As in any mechanical system, these three vibration modes have respective natural, or “resonant”, frequencies, which depend on the mass and stiffness of the respective degree of freedom. When a slider is subjected to an external vibration source having a frequency that resides in the vicinity of one or more of the bearing's natural frequencies, the slider sustains vibrations, which often result in significant modulation of the head-media spacing. Modulation of the head-media spacing degrades the head's read and write performance and can cause intermittent contact between the head and the disc surface.
As bearing clearances continue to decrease to achieve greater recording densities, micro-waviness in the disc surface has been observed to be an increasing source of vibration excitation for sliders, especially at flying heights below 0.5 microinches. Since micro-waviness is a broadband frequency type of excitation, it is often impossible to de-couple the bearing's natural frequency with the frequency of the excitation source by changes to the design of the bearing surface.
A slider is desired, which dampens head-media separation modulation in response to dynamic excitation induced by media micro-waviness at flying heights below 0.5 microinches.
SUMMARY OF THE INVENTION
One aspect of the present invention relates to a disc head slider, which includes a leading slider edge, a cavity dam, a subambient pressure cavity, which trails the cavity dam and has a cavity floor, and first and second rails disposed about the subambient pressure cavity. Each rail has a rail width, which is measured from an inner rail edge to an outer rail edge, a leading bearing surface, a trailing bearing surface, and a recessed surface extending between the leading and trailing bearing surfaces. The recessed surface is recessed from the bearing surfaces and raised from the cavity floor, across the rail width. First and second recessed leading channels are positioned near the leading slider edge. each leading channel has a leading channel end open to fluid flow from the leading slider edge, non-divergent channel side walls, and a trailing channel end closed to the fluid flow from the leading slider edge. A trailing channel is recessed within each of the trailing bearing surfaces. Each trailing channel has a leading channel end open to fluid flow from the respective recessed surface, non-divergent channel side walls, and a trailing channel end closed to the fluid flow from the respective recessed surface.
Another aspect of the present invention relates to a disc head slider, which includes a leading slider edge, a trailing slider edge, first and second laterally spaced leading bearing surfaces, and first and second laterally spaced trailing bearing surfaces positioned between the first and second leading bearing surfaces and the trailing slider edge. A convergent channel is recessed within each of the leading and trailing bearing surfaces. Each channel has a leading channel end open to fluid flow from the leading slider edge, non-divergent channel side walls, a trailing channel end closed to the fluid flow, a channel width and a channel length. The trailing channel end is positioned forward of a localized pressure gradient region on the respective bearing surface, downstream of the channel. The channel width is measured between the channel side walls, and the channel length is measured between the leading and trailing channel ends and is at least twice the channel width. The localized pressure gradient region has a length, which is at least as long as the channel width.
Yet another aspect of the present invention relates to a disc drive assembly, which includes a disc and a slider bearing. The disc is rotatable about a central axis and has a recording surface with a circumferential waviness characteristic. The slider bearing supports a transducer over the recording surface at a flying height of 0.5 microinches or less during rotation of the disc and generates vibration dampening pressure gradients of at least 20 Giga-Pascals per meter between the bearing surface and the disc, at multiple locations along the bearing surface.
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Boutaghou Zine-Eddine
Hanchi Jorge V.
Sannino Anthony P.
Renner Craig A.
Seagate Technology LLC
Westman Champlin & Kelly
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