| 摘要 |
A rotary drive device (10) to drive a rotary body included in an image forming apparatus (100). The rotary drive device (10) includes a drive source (73) and a planetary gear mechanism (80) to control torque from the drive source (73). The planetary gear mechanism (80) includes a sun gear (54; 57) rotated by the torque, an annular gear (58) coaxial to the sun gear (54; 57) and having inward-facing teeth, multiple planetary gears (55; 56) provided within the annular gear (58), and a carrier (60; 61) rotatable coaxially to the sun gear (54; 57) and the annular gear (58) to rotatably support the multiple planetary gears (55; 56). The annular gear (58) is formed by injecting molten resin into a mold (14) having a cylindrical cavity (17) with teeth shapes along an inner circumference of the cavity (17) from multiple pin gates (20) provided to the mold (14) at equal intervals along a circumference of the cavity (17). A number of pin gates (20) is a non-integer multiple of a number of planetary gears (55; 56). |
