Rotary power transmission mechanism for transmitting rotary power from a shaft to a cylindrical member while suppressing shifting of the cylindrical member during rotation, and photoreceptor drum device, developing device, fixing device, and image forming device provided with the rotary power transmission mechanism

A rotary power transmission mechanism, comprising:

• a cylindrical member configured to rotate in one direction;
• a flange member fitted to one end portion of the cylindrical member, and having a through hole passing through a center of the flange member;
• a shaft inserted through the through hole, and having an insertion hole passing through a radial direction of the shaft, rotary power of the shaft being transmitted to the cylindrical member via the flange member;
• and
• a pin member inserted through the insertion hole and having two end portions, which are portions of the pin member that protrude from opposite sides of the shaft, wherein
• the flange member has a pair of contact portions that have point symmetry with respect to an axial center of the shaft, the pair of contact portions being composed of a first contact portion and a second contact portion, and when the pin member is rotated in the one direction by the shaft rotating in the one direction, the first contact portion contacts and is pushed by a first end portion of the pin member and the second contact portion contacts and is pushed by a second end portion of the pin member, the first end portion being one of the two end portions and the second end portion being the other one of the two end portions,
• the pin member, when rotating in the one direction, simultaneously pushes against the first contact portion and the second contact portion, to rotate the flange member in the one direction, and thereby transmits rotary power to the cylindrical member, and
• the pair of contact portions protrude toward the in member.