US Patent 9994284 Bicycle assist unit

A bicycle assist unit is basically provided with a transmission and an assist motor. The transmission is configured to receive rotation of a crankshaft. The transmission includes a planetary gear mechanism. The planetary gear mechanism includes an output unit, a plurality of ring gears and a rotation restricting mechanism that selectively restricts rotation of the ring gears. The assist motor is configured to output a second drive force that is added to a first drive force that is outputted from the transmission on a power transmission path between the output unit and a front sprocket that is attached to the crankshaft.