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The traction and power generation motors of hybrid electric vehicles need to provide greater output densities. This can be achieved by increasing output and reducing the physical size and weight of the motors. However, there are limits on how much a motor’s output can be increased while simultaneously shrinking the motor’s size, as it is conventionally structured. To address this issue, the authors developed a stator with a new structure to increase motor output and reduce motor size. By simultaneously optimizing magnetic circuit design, they increased maximum torque by 2.6% and maximum output by 8.9% and reduced volume by 23% and weight by 23% compared to motors of conventional structure, all while maintaining the same level of efficiency. The result was top-of-class output and compactness.

Nd₂Fe₁₄B sintered magnets are used in the drive motors of hybrid, electric and other vehicles. A magnet in which rare earth content is reduced by means of a localized diffusion method has been developed in order to reduce the volume of dysprosium. The distribution of the demagnetization fields in a motor is not uniform, so the necessary coercivity distribution for the magnets was quantified using Computer-Aided Engineering (CAE). Then material specifications of the localized dysprosium diffusion satisfied with this coercivity distribution was determined, and optimal manufacturing conditions including the position of dysprosium diffusion were set. The coercivity distribution in every position of the magnet using localized diffusion method was inspected. As a result, the magnet was satisfied with coercivity distribution demanded by CAE.