According to one embodiment, a sheet conveying device includes a roller, a motor, a clutch, and a torque generator. The roller conveys a sheet. The motor is a driving source. The clutch connects or disconnects drive of the motor with respect to the roller. The torque generator applies a torque to the roller.

An image forming apparatus includes: a first gear train including a first clutch; a second gear train including a second clutch; a third gear train including a third clutch; a fourth gear train including a fourth clutch; a motor including an output shaft; an output gear rotatable with the output shaft; a fifth gear train connected to the first and second clutches; and a sixth gear train connected to the third and fourth clutches. The first clutch engages transmission of a driving force to a first developing unit, the second clutch engages transmission of a driving force to a second developing unit, the third clutch engages transmission of a driving force to a third developing unit, and the fourth clutch engages transmission of a driving force to a fourth developing unit. The fifth and sixth gear trains are connected to the output gear independently from each other.

An image forming apparatus, having first, second, third, and fourth photosensitive drums, first, second, third, and fourth developing rollers, a development-driving gear, a development motor, a first development gear train having a first gear, a second development-gear train having a second gear, a process-driving gear, a process motor, a first process-gear train having a third gear, and a second process gear-train having a fourth gear, is provided. The first development-gear train transmits a driving force from the development motor to the first and second developing rollers. The second development-gear train transmits the driving force from the development motor to the third and fourth developing rollers. The first process-gear train transmits a driving force from the process motor to the first and second photosensitive drums. The second process-gear train transmits the driving force from the process motor to the third and fourth photosensitive drums.

A developing cartridge includes: a developing roller rotatable about an axis extending in a first direction; a casing; and a first cam provided at an outer surface of one end portion of the casing in a second direction. The first cam is movable in a third direction between a first position and a second position closer to the developing roller than the first position is in the third direction. The first cam has: a first inclined surface for receiving a pressing force in the first direction; and a second inclined surface. A distance between the second inclined surface and the casing in the second direction varies as the second inclined surface extends away from the developing roller in the third direction. The first cam is movable between the first position and the second position in response to application of the pressing force to the first inclined surface.

A partial reverse clutch assembly comprises a frame, a coupling member, a corrugated swing body, and a cam body. The frame mounts an input gear and an output gear, and, a coupling member that is disposed between input and output gears couple the input gear to the output gear to transmit a motorized rotational drive in a first direction. The swing body is coupled between the input gear and the coupling member and comprises a projecting swing arm. The cam body abuts and defines a sliding contact between the swing body and the coupling member, where a reversal of the motorized rotational drive oppositely rotates the output gear in engagement with the swing arm in a second direction. The cam body is displaced upon contact to with the swing body during the rotation in the second direction to decouple the coupling member between the input gear and the output gear.

An image-forming apparatus includes: a photosensitive drum, a motor, and a drum gear train configured to transmit a driving force from the motor to the photosensitive drum. The drum gear train includes a first gear, a second gear and a first clutch. The first gear is rotatable about a first axis upon receipt of the driving force. The second gear is rotatable about the first axis and configured to receive the driving force from the first gear and to transmit the driving force to the photosensitive drum. The first clutch is switchable between a first transmission state where the driving force is transmitted from the first gear to the second gear and a first transmission cutoff state where the transmission of the driving force from the first gear to the second gear is cut off.

Provided is an image forming apparatus, having: a power source; a first coupling member configured to be rotated by a driving force transferred from the power source; and a cartridge including a second coupling member configured to rotate in a state of being adsorbed to the first coupling member, and a rotating member connected with the second coupling member, wherein the first coupling member has a first driving force transfer surface which is perpendicular to a rotation axis of the first coupling member, the second coupling member has a second driving force transfer surface which is perpendicular to a rotation axis of the second coupling member, and the driving force is transferred from the first coupling member to the second coupling member in a state where an adsorption force is generated mutually between the first driving force transfer surface and the second driving force transfer surface.

A developing cartridge includes: a casing, a developing roller, a first agitator, a supply roller, and a second agitator. The casing is configured to accommodate toner. The developing roller is rotatable about a developing roller rotation axis extending in a first direction. The first agitator is configured to agitate the toner. The first agitator is rotatable about a first agitator rotation axis extending in the first direction. The supply roller is positioned between the first agitator and the developing roller. The supply roller is rotatable about a supply roller rotation axis extending in the first direction. The second agitator is positioned between the supply roller and the first agitator. The second agitator is rotatable about a second agitator rotation axis extending in the first direction. A rotation locus of the second agitator is positioned outside of a rotation locus of the first agitator.

A process cartridge includes a photosensitive drum and a gear portion having gear teeth configured to receive a driving force from outside of the process cartridge. The gear portion includes an exposed portion exposed to outside of the process cartridge. A shortest distance from an axis of the photosensitive drum to a tooth tip of the exposed portion of the gear portion measured along a direction perpendicular to the axis of the photosensitive drum is no less than 90% and no more than 110% of a radius of the photosensitive drum.

An image forming apparatus includes: a motor; a roller; and a power transmission device for transmitting a driving force of the motor to the roller. The power transmission device includes: a planetary gear mechanism including a first helical gear into which the driving force is inputted, a second helical gear for outputting the driving force to the roller, and a transmission element; and a restriction member. The transmission element can transmit the driving force when the restriction member is in its restricting position and thus rotation of the transmission element is restricted, and interrupts transmission of the driving force when the restricting member is in its non-restricting position and thus rotation of the transmission element is not restricted. A direction of a first thrust force applied to the first helical gear and a direction of a second thrust force applied to the second helical gear are opposite to each other.