Patent ID: 11390358

Abstract:
A wide range of existing bicycles can be converted into electric power assisted bicycles with ease. The bicycle electric power assist device comprises a housing (52) configured to be attached to a frame (18) of a bicycle (10), an electric motor (54) attached to the housing (52), a battery (102) configured to be mounted to the frame and serves as a power source for the electric motor, an annular rotational output member (81) rotationally driven by the electric motor (54), the rotational output member being rotatably mounted on the housing and positioned around a crank axis line which is a rotational center line A of a crankshaft (24) and a crank arm (26) for a pedal of the bicycle, and a connecting member (90) connecting the rotational output member (81) to the crankshaft (24) or the crank arm (26) in a torque transmitting relationship.