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High Volumetric Density Hard Disk Drive

IP.com Disclosure Number: IPCOM000108559D
Original Publication Date: 1992-Jun-01
Included in the Prior Art Database: 2005-Mar-22
Document File: 5 page(s) / 198K

Publishing Venue

IBM

Related People

Estry, RH: AUTHOR [+6]

Abstract

A series of hard disk drives, with disk diameters and external dimensions proportionally smaller and conforming to a specific scaling methodology, is described here. Disk pitch, the vertical distance between centers of two overlying disks within the disk stack, is minimized, resulting in a maximum number of disks per vertical drive height, as well as a maximum storage capacity at a given areal density. This data storage capacity per volume of the hard disk drive is the volumetric density and is a maximum for a well-designed drive.

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This is the abbreviated version, containing approximately 52% of the total text.

High Volumetric Density Hard Disk Drive

       A series of hard disk drives, with disk diameters and
external dimensions proportionally smaller and conforming to a
specific scaling methodology, is described here.  Disk pitch, the
vertical distance between centers of two overlying disks within the
disk stack, is minimized, resulting in a maximum number of disks per
vertical drive height, as well as a maximum storage capacity at a
given areal density.  This data storage capacity per volume of the
hard disk drive is the volumetric density and is a maximum for a
well-designed drive.

      A hard disk drive consists of one or more rigid disks rotating
on a spindle comprising a disk stack.  A motor, contained within the
spindle, provides this rotary motion to the disk stack.  A moving
actuator with sensing heads travels over each disk surface reading or
writing information at well-defined locations on the disk.  A portion
of the actuator, two arms and suspensions retaining sensing heads,
must fit between the vertical spacing separating each disk.  The
actuator is driven by a motor. The entire assembly of disks, heads,
actuators and motors are retained within an enclosure having length,
width, and vertical thickness.  Internally within the enclosure, air
circulates to maintain proper flow patterns for particle and
contaminant control.  The external drive dimensions are interrelated
and also are related to disk diameter.

      Disk pitch consists of disk spacing and disk thickness. Spacing
is determined by actuator arm, suspension and sensing head
dimensions, as shown in Figure 1.  Arm thickness is critical, and
shorter arms required for small diameter disks with short data bands
may be thinner while maintaining similar deflection and vibrational
characteristics as well as increased resonant frequency.  As arm
thickness is reduced for small diameter disks, slider height
comprises a larger portion of the disk/disk spacing, and reducing
this height is accelerated through the drive scaling and diameter
reduction.

      Disk thickness is inversely proportional to disk diameter based
on similar deflection mechanics which control disk rigidity.  In this
case thickness can be reduced as disk diameter is reduced while
maintaining both static and dynamic deflection characteristics, by
the following expressions:

                            (Image Omitted)

and
where td and d are the disk thickness and disk diameter,
respectively.

      Figure 2 shows disk thickness has in fact been reduced with the
availability of smaller disk diameters, and this trend is expected to
continue.

      Equations (1) and (2) equally describe the mechanics of such
disk drive parts as arms, which may also be thinner as linear
dimensions are reduced.

      The volumetric densit...