Coaxial mid-drive power device of bicycle

Abstract

A coaxial mid-drive power device of a bicycle includes a reducing structure and a hollow shaft motor engaged with the reducing structure that are disposed in a motor base. An output end of the reducing structure is operatively coupled with a one-way bearing bracket with a sprocket base via a one-way bearing. A crank spindle engaged with the one-way bearing bracket through another one-way bearing penetrates through the motor base. The two one-way bearings respectively have opposite rotation directions and are respectively located on different sides, i.e., an inside and an outside, of the one-way bearing bracket. A strain gauge disposed on the crank spindle is electrically connected to an annular conductive rail assembly engaged with the crank spindle and an elastic sheet assembly on a control circuit board in the motor base, hence the strain gauge could directly obtain a change in a torque of the crank spindle.