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Browse Prior Art Database

Asymmetric Voice Coil Motor Concept for Load/Unload Disk Files

IP.com Disclosure Number: IPCOM000117170D
Original Publication Date: 1996-Jan-01
Included in the Prior Art Database: 2005-Mar-31
Document File: 4 page(s) / 84K

Publishing Venue

IBM

Related People

Berg, LW: AUTHOR

Abstract

An asymmetric Voice Coil Motor (VCM) design that provides higher data band torque with acceptable load/unload torque is disclosed.

This text was extracted from an ASCII text file.
This is the abbreviated version, containing approximately 52% of the total text.

Asymmetric Voice Coil Motor Concept for Load/Unload Disk Files

      An asymmetric Voice Coil Motor (VCM) design that provides
higher data band torque with acceptable load/unload torque is
disclosed.

      In a file which incorporates load/unload, the VCM design is
somewhat compromised.  In order to provide actuator torque over the
entire band from ID data track to unloaded position, the swing angle
must necessarily be quite large.  In existing designs, the magnets
span the entire band from ID to unload, and VCM designs have aimed to
provide constant torque over the entire band.  The large swing angle
makes the surface area of the magnets large, and drives lots of flux
through the pole pieces.  The flux must be limited by the amount that
can be driven through the pole pieces.  The pole pieces must be made
thicker, while the magnet is thinner to minimize stray flux.  The
thin, large area magnets do not provide the same gap flux density as
would be obtained from thicker, smaller area magnets with a
comparable gap.

      There are two lines of thought on flat coil VCM design.  Some
say one should use a single bipolar magnet or a pair of oppositely
polarized magnets adjacent to one another.  Others say magnets should
be separated by an air gap to eliminate some of the fringe fields.

      If one allows the magnets to have a gap between them, it is
possible to design a VCM that provides nominally a uniform torque
constant over the entire data band.  In the unload region, the torque
can be made to be nominally half of the data band value.

      Consider the actuator and magnets schematically shown in Fig.
1.  The act...