Drum unit, process cartridge and image forming apparatus

A drum unit usable with a process cartridge, the drum unit comprising:

• a photosensitive drum having an axis L1;
• and
• a coupling member having an axis L2, the coupling member including (i) a first end portion, (ii) a second end portion operatively connected to an end portion of the photosensitive drum, and (iii) a connecting portion connecting the first end portion and the second end portion,
• wherein the first end portion is provided with a recessed surface facing away from the second end portion and is provided with a projection projecting from a surface that is adjacent to the recessed surface,
• wherein the coupling member is movable along the axis L2 between a first position and a second position in which the projection is closer to the photosensitive drum than the projection is to the photosensitive drum when the coupling member is in the first position,
• wherein the projection has an outer surface facing away from the axis L2,
• wherein at least a part of the outer surface of the projection increases in distance from the axis L2 as the distance from the photosensitive drum increases in a direction of the axis L1, and
• wherein a distance along a line perpendicular to the axis L2 between at least a part of an outer surface of the connecting portion and the axis L2 is shorter than a maximum distance along a line perpendicular to the axis L2 between the outer surface of the projection and the axis L2.