Patent ID: 7974553

Claim:
An image forming apparatus comprising: a main assembly; an image forming unit which forms a toner image on a sheet; a fixing unit which fixes the toner image on the sheet by nipping and conveying the sheet at a fixing nip portion, said fixing unit including a pressure applying mechanism which applies pressure to the fixing nip portion and a cam member for releasing the pressure applied to the fixing nip portion by acting to said pressure applying mechanism and being detachably attachable to said main assembly; an opening and closing member which is attached to said main assembly to be capable of being opened and closed; a first gear which is provided at said main assembly and which is moved in accordance with movement of said opening and closing member; a second gear which is provided at said fixing unit for moving said cam member; and a connection gear which connects said first gear and said second gear by being engaged with both said first gear and said second gear, said connection gear configured to be held by said fixing unit; wherein said connection gear is configured to be detachable from between said first gear and said second gear and to be attachable being engaged with both said first gear and said second gear only in a case that said first gear and said second gear are respectively at a predetermined phase, and wherein said apparatus includes an attaching prevention mechanism which prevents said fixing unit from being attached to said main assembly in a state that said connection gear is held by said fixing unit.