Patent ID: 8086135

Claim:
A developing device detachably mountable to a main assembly of an electrophotographic image forming apparatus, the main assembly of the electrophotographic image forming apparatus including a rotatable main assembly driving force transmission member, a movable member movable between a first position for permitting said developing device to enter the main assembly of the electrophotographic image forming apparatus in a longitudinal direction of said developing device and a second position for urging said developing device in a direction crossing the longitudinal direction to position said developing device in the main assembly of the electrophotographic image forming apparatus, and a main assembly locking member, said developing device comprising: a developing roller for developing an electrostatic latent image formed on electrophotographic photosensitive drum with developer; a shaft coupling member, provided on one axial end of said developing roller, for transmitting a rotational driving force from the main assembly driving force transmission member with a deviation permitted between an axis of the main assembly drive transmission member and an axis of said developing roller; a holding portion, wherein said shaft coupling member includes an engaging portion for engaging with the main assembly drive transmission member and receiving the rotational driving force when said developing device is mounted to the main assembly of the apparatus, wherein said engaging portion is movable relative to the developing roller in a direction crossing with the axial direction of said developing roller, wherein when said developing device enters said main assembly of the apparatus, said engaging portion is positioned relative to said holding portion, and wherein when said developing device is positioned to the main assembly positioning portion by said movable member taking the second position, said engaging portion is positioned to the main assembly locking member instead of said holding portion.