Development of motor assist system for four-door sedan

摘要

This paper presents new IMA (Integrated Motor Assist) system developed from previous one installed in "Insight". To install it in a conventional four-door sedan, system miniaturization and efficiency improvement were needed. The ultra thin DC brushless motor and IPU (Integrated Power Unit) were both improved for this purpose. An improved magnetic circuit and sinter diffusion bonding rotor were developed for the motor. The advancements of IPU are parts integration of inverter, new electric circuit for the DC-DC converter, optimum arrangement of the Ni-MH battery, and integration of the cooling circuit.