Magnetic Form applying a C-Shaped Magnet for Hybrid Electric Vehicles

Abstract

Currently, electrification for vehicles such as battery electric vehicles (BEVs), plug in-hybrid electric vehicles (PHEVs), fuel cell electric vehicles (FCEVs), and hybrid electric vehicles (HEVs) has received considerable attention, owing to the urgent need to reduce CO2 emissions created from transportation and the energy dependency on crude oil. Honda has set a target whereby two-thirds of total global sales should come from EVs by 2030. A traction motor is an essential component of electrified vehicles. Generally, interior permanent magnet synchronous motors (IPMSMs) are used as traction motors owing to their high torque and power density, high efficiency and ease of use. The design of rotors, which consist of magnets and electrical steel sheets, is important for IPMSMs because their average torque, efficiency, quietness, as well as cost depend on it. We have developed a novel rotor, which allows for a degree of freedom in the shape of the magnets. In the proposed rotor, first, the shape and position of the magnets are determined parametrically under manufacturing constraints. Then, the shape of the electrical steel sheet is determined by the ideal flux-line using maximized Lq-Ld. This involves combining q-axis flux and flux shape optimization for a practical design of the rotor. We also reduced torque ripple by considering the magnet position and dimple design. Rotors that are used in electrified vehicles are rotated at a maximum speed without gearing; therefore, the rotor must be designed by taking into consideration not only the magnetic forces but also the centrifugal ones. Therefore, we studied a mechanical simulation by optimizing magnetic performance while limiting maximum stress and displacement. We also developed a new production process for a C-shaped sintered and hot-deformed magnet.