To miniaturize and reduce weight of an electric drive part motor, improve fuel consumption in addition to efficiently insure necessary maximum torque, and facilitate handling by performing field weakening operation of an electric drive part.
In this assisted motor bicycle, an electric drive part 1 in which a torque detector and a brushless motor, reduction gears and a control circuit are integratedly built, is on the center lower part of a bicycle frame 2, and electrically connected to a battery 3 to be a motor drive energy source. The electric drive part 1 is performed field weakening operation is sufficiently assisted in a normal high load, further in the high speed territory, rotating speed of the motor which can not deal with the vehicle speed by ordinary operation is pulled up to the high speed territory by field weakening operation so as to be able to drive. Hereby, the electric drive part 1 can be miniaturized and the weight can be reduced, in addition to insure necessary maximum torque in high efficiency, improve fuel consumption, and handling can be facilitated.
NAKAMURA KOJI
MATSUO AKIRA
