US Patent 9525321 Rotation driving device

A rotation driving device includes a motor provided in a housing, a planetary gear reducer connected to the motor coaxially with the motor, an output shaft connected to an end reduction member of the planetary gear reducer coaxially with the end reduction member, and a rotation detector located at the same position as the end reduction member in an axial direction of the planetary gear reducer and located at a different position from a center axis of the end reduction member in a radial direction of the planetary gear reducer, the rotation detector being capable of detecting a degree of rotation of the end reduction member. Accordingly, the rotation driving device can be made to be smaller and compact in the axial direction.