The present invention relates to an electric power assist device which can achieve proper power assist control regardless of the angle at which the electric power assist device mounted on a bicycle. An electric power assist device for bicycles of the present invention comprises: a housing (52) which can be attached to a frame structure (18) of a bicycle (10); an electric motor (58) provided in the housing (52); a rotating member (64, 72) rotatably supported by the housing (52), rotationally driven by the electric motor (58), and connected to a crankshaft (24) or crankarm (26) of the bicycle (10) in a torque transmitting relationship; a rotational angle sensor (124) provided in the housing (52) and configured to detect a rotational angle of the electric motor (58) or the rotating member (64, 72); and a control unit (120) for controlling operation of the electric motor (58) based on the rotational angle detected by the rotational angle sensor (124), wherein the electric power assist device further comprises a tilt angle detector (128) for detecting a tilt angle with respect to a direction of gravity, and wherein the control unit (120) comprises a calibrator (148) for determining an absolute angle of the rotational angle detected by the rotational angle sensor (124) based on an output signal from the tilt angle detector (128).
ELECTRIC POWER ASSIST DEVICE FOR BICYCLES AND BICYCLE
2022-07-07
Patent
Electronic Resource
English