着磁の最適化によるEPS用永久磁石モータのコギングトルク低減

概要

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EPS (Electric Power Steering) enables an increase in fuel efficiency by 3-5 % and the protection of the environment by eliminating the oil medium in comparison with NPS (Normal Power Steering) which is driven by hydraulic power. For this reason a sharp increase in demand for EPS is expected. Permanent magnet motor is generally used for EPS. Reduction in cogging torque is one of the problems of this motor. In this paper, a new magnetization method to reduce cogging torque is proposed as a result of the investigation into the relationship between the magnetic force distribution and magnetizing waveform of a magnet by using the magnetic field analysis, in the brushless motor using radially oriented ring magnet. It was confirmed that the following methods are effective in reducing cogging torque as a result. (1) Optimization of skew magnetizing angle according to magnetic force distribution along the axial direction of the magnet. (2) Control of the magnetizing intensity of the circumference direction of a magnet.
電気製鋼研究会の論文