Spindle motor having reduced torque ripple
US5093595A · kind A · utility
Assignee
Inventor
Key dates
| Filing date | Apr 29, 1991 |
| Grant date | Mar 3, 1992 |
| Priority date | — |
| Expiry date | Apr 29, 2011 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH02K21/22
- WIPO fieldElectrical machinery, apparatus, energy
- WIPO sectorElectrical engineering
Abstract
A disc drive includes a stationary frame and vertical spindle shaft, and a hub rotatable relative to the spindle shaft and supporting one or more magnetic discs. A motor for rotating the hub includes an annular stator integrally secured to the spindle shaft, and a rotor assembly integral with the hub. The rotor assembly includes an annular magnet and an annular back iron, with the magnet being spaced apart from the stator to define an air gap. The magnet includes four longitudinally disposed arcuate poles of equal size, separated from one another by flux gaps. Each of the poles has a medial region and first and second end regions on opposite sides of the medial region. The medial region is selectively magnetized to a level less than the level to which the end regions are magnetized, creating a flux gap and torque profile for the magnet particularly effective in reducing torque ripple.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.