A mounting/demounting structure includes: a mountable/demountable object including a body, a first projection provided at a first end of the body in a movable manner, and a second projection provided at a second end of the body in a shiftable manner; and a receptacle including a housing configured to house the object when mounted while covering it in at least two directions, first and second stoppers provided in the housing and configured to stop the first and second projections, respectively by engagement, the object including an abutment portion provided on the body and configured to abut against a part of the housing to keep a posture reduced in terms of an engagement amount between the second projection and the second stopper when the first projection is disengaged from the first stopper and the object is stopped at a tilt in the housing during demounting of the object from the receptacle.

A mounting/demounting structure includes: a mountable/demountable object that is mountable or demountable by inserting or pulling the mountable/demountable object including a body, a first projection provided at a first end of the body in a movable manner, and a second projection provided at a second end of the body in a shiftable manner; and a receptacle including a housing portion configured to, when the mountable/demountable object is mounted, house the mountable/demountable object while covering the mountable/demountable object in at least two directions, a first stopper provided in the housing portion and configured to stop the first projection by engagement, and a second stopper provided in the housing portion and configured to stop the second projection by engagement, the mountable/demountable object including an abutment portion provided on the body and configured to abut against a part of the housing portion to keep a posture reduced in terms of an engagement amount between the second projection and the second stopper when the first projection is first disengaged from the first stopper and the mountable/demountable object is stopped at a tilt in the housing portion during demounting of the mountable/demountable object from the receptacle.

A fixing device includes a body and a cover. The body includes a roller and a positioning projection projecting from the body. The cover is supported on one end side in an axial direction of the roller and has a slot in which the positioning projection is inserted. The cover is configured to pivot on the positioning projection inserted in the slot, from a closed position to a retreated position from the body.

A developing cartridge includes: a housing having first and second sidewalls through which respective end portions of a developing roller shaft are rotatably inserted; a developing gear, which is arranged outside of the first sidewall, and which is fixed to the end portion of the developing roller shaft; a transmission gear, which is arranged outside of the first sidewall, and which transmits driving force to the developing gear; a first cover member, which is attached to the first sidewall, and which covers the transmission gear; and a second cover member, which is attached to the first sidewall, and which covers the developing gear from an outer side in the axis line direction. The second cover member is formed separately from the first cover member and is arranged side by side with the first cover member outside of the first sidewall.

A fixing device includes a body and a cover. The body includes a roller and a positioning projection projecting from the body. The cover is supported on one end side in an axial direction of the roller and has a slot in which the positioning projection is inserted. The cover is configured to pivot on the positioning projection inserted in the slot, from a closed position to a retreated position from the body.

An image forming apparatus includes an apparatus body and a unit detachably mounted to the apparatus body and comprising a unit body, a cam, a first movement member, and a second movement member. The unit includes a first contact portion, an urging portion, and a second contact portion. The second movement member is attachable to the first movement member in a first manner or a second manner. A detection pattern of a detection signal differs between a state in which the second movement member is in contact with the first contact portion and a state in which the second movement member is in contact with the second contact portion, and differs between a state in which the second movement member is attached in the first manner and a state in which the second movement member is attached in the second manner.

A developing cartridge includes: a housing having first and second sidewalls through which respective end portions of a developing roller shaft are rotatably inserted; a developing gear, which is arranged outside of the first sidewall, and which is fixed to the end portion of the developing roller shaft; a transmission gear, which is arranged outside of the first sidewall, and which transmits driving force to the developing gear; a first cover member, which is attached to the first sidewall, and which covers the transmission gear; and a second cover member, which is attached to the first sidewall, and which covers the developing gear from an outer side in the axis line direction. The second cover member is formed separately from the first cover member and is arranged side by side with the first cover member outside of the first sidewall.

A developing cartridge includes: a housing having first and second sidewalls through which respective end portions of a developing roller shaft are rotatably inserted; a developing gear, which is arranged outside of the first sidewall, and which is fixed to the end portion of the developing roller shaft; a transmission gear, which is arranged outside of the first sidewall, and which transmits driving force to the developing gear; a first cover member, which is attached to the first sidewall, and which covers the transmission gear; and a second cover member, which is attached to the first sidewall, and which covers the developing gear from an outer side in the axis line direction. The second cover member is formed separately from the first cover member and is arranged side by side with the first cover member outside of the first sidewall.

An image forming apparatus includes a cartridge including a photosensitive drum; an endless belt configured to transfer the toner image formed on the drum; an endless belt supporting member movable between a contacting position for contacting the belt to the drum and a non-contacting position retracted from the contacting position away from the drum; and a cartridge supporting member movable between an image forming position in which the drum contacts the belt taking the contacting position and a non-image-forming position in which the cartridge is movable from a inside to a outside of the main assembly. By movement of the belt from the contacting position to the non-contacting position, a space capable of accommodating at least a part of the cartridge supporting member taking the non-image-forming position and/or the cartridge supported by the cartridge supporting member taking the non-image-forming position is provided.

An image forming apparatus includes an apparatus body and a unit detachably mounted to the apparatus body and comprising a unit body, a cam, a first movement member, and a second movement member. The unit includes a first contact portion, an urging portion, and a second contact portion. The second movement member is attachable to the first movement member in a first manner or a second manner. A detection pattern of a detection signal differs between a state in which the second movement member is in contact with the first contact portion and a state in which the second movement member is in contact with the second contact portion, and differs between a state in which the second movement member is attached in the first manner and a state in which the second movement member is attached in the second manner.