Patent ID: 8588651

Claim:
A rotary drive device to drive a rotary body included in an image forming apparatus, the rotary drive device comprising: a drive source; and a planetary gear mechanism to control torque from the drive source, the planetary gear mechanism comprising: a sun gear rotated by the torque from the drive source; an annular gear coaxial to the sun gear, having inward-facing teeth; multiple planetary gears provided within the annular gear at equal intervals along a circumference of the annular gear, the multiple planetary gears engaging both the sun gear and 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 being 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 being a non-integer multiple of a number of planetary gears.