Patent ID: 7551877

Claim:
An image forming apparatus comprising: a main body casing; a reference shaft provided in the main body casing; a photosensitive unit that is detachably attachable to the main body casing along a generally horizontal attachment/detachment direction, the photosensitive unit holding together a plurality of photosensitive members in a state where the plurality of photosensitive members are arranged in parallel in the attachment/detachment direction, the photosensitive unit having an engaging portion for coming into engagement with the reference shaft when the photosensitive unit is attached to the image forming apparatus; a plurality of developing units each of which is detachably attachable to the photosensitive unit and has a developing agent carrier for supplying a developing agent to the photosensitive member; and a pressing member that is configured to linearly move along the attachment/detachment direction between a press position for pressing the developing unit to press the developing agent carrier into contact with the photosensitive member and a press releasing position for releasing this press contact, the pressing member urging the developing unit in a direction in which the engaging portion comes into engagement with the reference shaft in a process of moving from the press releasing position to the press position, wherein the developing unit has a pressed portion that is pressed by the pressing member, and wherein the pressing member has a pressuring surface that is inclined with respect to the attachment/detachment direction so as to abut against the pressed portion to press the pressed portion in a direction in which the engaging portion comes into engagement with the reference shaft, in the process of moving from the press releasing position to the press position.