In order the image formation device which has the resin make gear and this resin make gear, to center the rotary

摘要

PROBLEM TO BE SOLVED: To provide a resin-made gear having satisfactory rotation transmission accuracy. SOLUTION: A first peripheral direction rib 10 and a second peripheral direction rib 11 are coaxially formed on a web 5 on an inner peripheral side of a tooth part 8. Moreover, the rigidity of the web 5 is increased by ribs 14, 12, 15 in the radial direction. Since the rib 14 in the radial direction is formed to extend obliquely in the direction reverse to the direction of rotation, a resistance force preventing the displacement of the second peripheral direction rib 11 so as to deviate in the direction of rotation relative to a shaft support part 4 is generated in the rib 14 in the radial direction, even if the second peripheral direction rib 11 attempts to displace due to torque fluctuation acting when rotation is transmitted, so that the displacement of the second peripheral direction rib 14 so as to deviate in the direction of rotation relative to the shaft support part 4 can be effectively suppressed and dispersion in rotary angular velocity of the second peripheral direction rib 14, the shaft support part 4, the tooth part 8 and the shaft support part 4 can be suppressed.