Patent ID: 8864620

Claim:
A rotary body driver for driving a rotary body, the rotary body driver comprising: a driving source to generate a driving force; a planetary gear transmission connected to the driving source to receive the driving force therefrom and including: a sun gear rotatable by the driving force received from the driving source; a plurality of planet gears meshed with and surrounding the sun gear with an identical interval between the adjacent planet gears; a rotatable carrier to rotatably support the plurality of planet gears; an outer gear encircling and meshed with the plurality of planet gears; and an output shaft combined with and supporting the carrier; a rotary body shaft mounting the rotary body and connected to the output shaft of the planetary gear transmission to transmit the driving force received from the output shaft to the rotary body; a rotation speed detector including a detected portion disposed coaxial to the rotary body shaft of the rotary body or the output shaft of the planetary gear transmission to detect a rotation speed of the rotary body; a hollow cylindrical joint fitted onto the rotary body shaft of the rotary body to couple the output shaft of the planetary gear transmission to the rotary body shaft of the rotary body; and a screw to fasten the joint to the output shaft of the planetary gear transmission, wherein the detected portion of the rotation speed detector is disposed downstream from the joint in a driving force transmission direction, wherein the joint has a slit extending from a center to a circumferential edge thereof facing the output shaft of the planetary gear transmission in an axial direction of the rotary body shaft of the rotary body, and wherein the outer gear is made of resin and the output shaft and the carrier are made of metal.