Rotary drive device and image forming apparatus including same

摘要

A rotary drive device to drive a rotary body included in an image forming apparatus. The rotary drive device includes a drive source and a planetary gear mechanism to control torque from the drive source. The planetary gear mechanism includes a sun gear rotated by the torque, an annular gear coaxial to the sun gear and having inward-facing teeth, multiple planetary gears provided within the annular gear, and a carrier rotatable coaxially to the sun gear and the annular gear to rotatably support the multiple planetary gears. The annular gear is formed by injecting molten resin into a mold having a cylindrical cavity with teeth shapes along an inner circumference of the cavity from multiple pin gates provided to the mold at equal intervals along a circumference of the cavity. A number of pin gates is a non-integer multiple of a number of planetary gears.