A drive transmission device includes a drive train including a plurality of drive transmitters, and a container. The plurality of drive transmitters of the drive train transmit a driving force of a drive source to a rotator rotatable around a shaft and a swing member rotatable around a shaft different from the shaft of the rotator. The container contains the drive train.

A medium transport unit includes an upstream route in which a print sheet is transported, a first switchback route, a second switchback route, a first guide route, a second guide route, a guide flap configured to switch the route so that the print sheet in the upstream route is transported either toward the first guide route or toward the second guide route, a first discharge route from which the print sheet in the first switchback route is discharged, a second discharge route from which the print sheet in the second switchback route is discharged, and a downstream route passing between the first switchback route and the second switchback route and having an upstream end connected to a junction of downstream ends of the first discharge route and the second discharge route.

A medium transport unit includes an upstream route in which a print sheet is transported, a first switchback route, a second switchback route, a first guide route, a second guide route, a guide flap configured to switch the route so that the print sheet in the upstream route is transported either toward the first guide route or toward the second guide route, a first discharge route from which the print sheet in the first switchback route is discharged, a second discharge route from which the print sheet in the second switchback route is discharged, and a downstream route passing between the first switchback route and the second switchback route and having an upstream end connected to a junction of downstream ends of the first discharge route and the second discharge route.

An image forming apparatus includes a casing, a door, first and second switching portions, an interlocking portion, and an operating portion. The first switching portion is switched to a first state in which the door is rotatable from a closed position to a first opened position and a second state in which the door is rotatable from the first opened position to a second opened position. The second switching portion is switched to a third state in which the door is rotatable from the closed position to the first opened position and a fourth state in which the door is rotatable from the first opened position to the second opened position. The interlocking portion interlocks the first and second switching portions. The operating portion switches the first switching portion to the first and second states, and switches the second switching portion to the third and fourth states.

An image forming apparatus includes: an image forming unit; a first re-conveyance guide that guides a sheet on which an image is formed in a re-conveying direction; a second re-conveyance guide that guides the sheet from the first re-conveyance guide toward the image forming unit; a side guide provided at one end portion of the second re-conveyance guide in a widthwise direction to regulate the sheet; a side chute provided at one end portion of the first re-conveyance guide in the widthwise direction; and an engaging portion provided on the second re-conveyance guide. The engaging portion is engaged with a first engaging portion extending downward from an upstream end portion of the side guide in the re-conveying direction and is engaged with a second engaging portion provided on a downstream end portion of the side chute in the re-conveying direction.

A media path includes a first media path portion, and a second media path portion opposed to the first media path portion, where the first media path portion and the second media path portion form the media path therebetween, and where, to open the media path, the first media path portion is rotatable relative to the second media path portion and the second media path portion is rotatable relative to the first media path portion.

A sheet transport device includes a first transport route, a roller, a second transport route, a switching nail, a lever, a sheet detection piece, a cam, an intermediate rotary member, a rotary member, a sensor, a driver, and a controller. The controller controls the driver to switch the switching nail between a first transport position and a second transport position, decides that the sheet is transported through first transport route, when the sheet detection piece retreats contacted by the sheet on the first transport route, with the switching nail being set to the first transport position, and the sensor detects that the rotary member is in the second posture, and decides that the switching nail has been switched from the first transport position to the second transport position, when the sensor detects that the rotary member is in the second posture, after the sheet has passed the sheet detection piece.

An image forming apparatus includes a discharging portion to discharge a sheet on which the image has been formed, an image reading portion to read the image formed on the sheet, and a switching portion to switch between a first position where the discharged sheet is conveyed to a supporting portion and a second position where the discharged sheet is conveyed toward the image reading portion. The sheet conveyed toward the image reading portion is conveyed to a reading position after conveyance of the sheet by the discharging portion is finished, and the control portion conveys the sheet at a first conveyance speed in a period before a trailing end of the sheet is released from the discharging portion and conveys the sheet at a second conveyance speed different from the first conveyance speed in a period after the trailing end of the sheet is released from the discharging portion.

An image forming apparatus includes an output shaft including a columnar part and a D cut part connected to the columnar part and having a D section, and an electromagnetic clutch including a cylindrical member fitted to the output shaft. The image forming apparatus further includes a key member. The key member includes a conductive member. When the D cut part of the output shaft is employed as an insertion tip side and the output shaft has been inserted to the cylindrical member from one side in an axial direction, the key member is configured to fill a space between the sectional circular part of the inner peripheral surface of the cylindrical member and the D cut part of the output shaft.

In accordance with an embodiment, an image forming apparatus comprises an external connection control section, a determination section and a guidance control section. The external connection control section controls connection with an external device. The determination section determines a type of the external device connected with the image forming apparatus. The guidance control section selects, on the basis of a determination result of the determination section, a message of guidance and displays the message on a display device.