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Brushless DC Motor for Disc File

IP.com Disclosure Number: IPCOM000040021D
Original Publication Date: 1987-Sep-01
Included in the Prior Art Database: 2005-Feb-01
Document File: 2 page(s) / 44K

Publishing Venue

IBM

Related People

Dance, WG: AUTHOR [+2]

Abstract

In a brushless DC motor, Hall effect switches for commutation are normally mounted above stator laminations. Here, the Hall switches are lowered into a recess in the stator laminations to reduce the overall motor height while maintaining performance. A problem in a small compact disc file where space is at a premium is motor height. Fig. 1 shows the normal arrangement Magnets 1 are fixed to rotor hub 2. Hall switches 3 are mounted above stator laminations 4. In order to operate satisfactorily, Hall switches 3 need to receive sufficient levels of magnetic flux. Thus, the height of rotor magnet 1 must be sufficient to provide the flux levels required.

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Brushless DC Motor for Disc File

In a brushless DC motor, Hall effect switches for commutation are normally mounted above stator laminations. Here, the Hall switches are lowered into a recess in the stator laminations to reduce the overall motor height while maintaining performance. A problem in a small compact disc file where space is at a premium is motor height. Fig. 1 shows the normal arrangement Magnets 1 are fixed to rotor hub 2. Hall switches 3 are mounted above stator laminations 4. In order to operate satisfactorily, Hall switches 3 need to receive sufficient levels of magnetic flux. Thus, the height of rotor magnet 1 must be sufficient to provide the flux levels required. The flux from magnet 1 is not fully contained within the magnetic circuit and so produces an undesired stray magnetic field which may adversely affect neighboring circuitry (not shown).

(Image Omitted)

Figs. 2 and 3 show Hall switches 3 mounted recessed within stator laminations
4. This concentrates the magnetic field on the Hall switches, enables the height of magnet 1 to be reduced and significantly reduces the level of the stray magnetic field. Also due to the improved magnetic circuit through Hall switch 3, less sensitive and lower cost switches may be used.

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