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Browse Prior Art Database

Linearity Improving Technique for Voice Coil Motor

IP.com Disclosure Number: IPCOM000119644D
Original Publication Date: 1991-Feb-01
Included in the Prior Art Database: 2005-Apr-02
Document File: 2 page(s) / 34K

Publishing Venue

IBM

Related People

Fukushima, Y: AUTHOR [+3]

Abstract

Disclosed is a technique for improving the linearity of Bg (magnetic flux density in working air gap) of VCM (Voice Coil Motor) which is composed of iron core and permanent magnets. In order to improve the linearity of Bg, the surface of the iron core which faces the magnet is depressed like a dimple. The appropriate shape of dimple(s) makes the characteristics of Bg flat.

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Linearity Improving Technique for Voice Coil Motor

      Disclosed is a technique for improving the linearity of
Bg (magnetic flux density in working air gap) of VCM (Voice Coil
Motor) which is composed of iron core and permanent magnets.  In
order to improve the linearity of Bg, the surface of the iron core
which faces the magnet is depressed like a dimple.  The appropriate
shape of dimple(s) makes the characteristics of Bg flat.

      VCM is used as an actuator drive mechanism in HDD (Hard Disk
Drive).  Flat linearity of Bg is required in the seek angle of moving
coil to achieve a flat force factor in the seek angle.

      The figure shows an example of VCM magnetic circuit using this
technique.  This magnetic circuit is composed of iron cores 1 and 3
and a permanent magnet 2.  The Bg is almost proportional to the ratio
of Lg (gap length) to Lm (magnet thickness).  If Lm is constant, the
Bg is decreased when Lg is increased.  Therefore, the Bg is
adjustable by the shape of dimples 4 formed on the upper surface of
the iron core 3.