US Patent 6880661 Detachable motor drive for a bicycle

A motor drive for a bicycle is provided. The motor drive includes a drive wheel and a motor device driving the drive wheel. The drive wheel contacts the ground and moves the bicycle by rotating friction between the drive wheel and the ground. The motor device includes a fixing portion that attaches the motor device to the frame of the bicycle, and a driving portion that holds the drive wheel and drives the drive wheel. The driving portion is pivotable with respect to the fixing portion between a parking state and a driving state. The drive wheel is spaced from the ground in the parking state, and contacts the ground in the driving state.