[SOLUTION] A cartridge includes a photosensitive drum and a coupling. the coupling includes a main body and a movable member movable relative to the main body. The movable member includes an engaging portion which is capable of entering between a driving force application member and a braking force application member by the movement relative to the main body. The movable member receives a driving force for rotating the photosensitive drum, from the driving force application member and also receives a braking force applying a load against rotation of the photosensitive drum, from the braking force application member.

A drive force transmission device includes a frame that supports therein plural gears transmitting a rotational drive force and that has a flat portion extending in a direction intersecting a direction in which the rotational drive force is transmitted. The drive force transmission device has an air channel that allows air sucked from an outside of the frame to pass therethrough so as to exhaust the air to the outside of the frame.

A developing device develops, with developer, an electrostatic latent image formed on an image carrying member, and includes a developing tank, a developer carrying member, and a drive input portion. The developing tank stores the developer and has a receiving port and a discharge port through which the developer is received and discharged respectively. The developer carrying member rotates in the developing tank while carrying the developer. The drive input portion receives a rotational force from outside the developing device and transmit the rotational force to a driven rotation shaft that is a rotation shaft of the developer carrying member. The receiving port, the discharge port, and the drive input portion are provided in the developing tank to be close to an end of the developing tank in a longitudinal direction of the developing tank.

A lock device includes a lock cover, a restricting portion, a drive source, a biasing portion, and a pressing portion. The lock cover is opened and closed when a developer storing portion storing developer is attached or detached. The restricting portion, when the lock cover is closed, is engaged with the lock cover in such a way as to restrict the lock cover from being opened. The drive source drives the restricting portion in such a way as to release an engagement between the restricting portion and the lock cover. The biasing portion biases the restricting portion in a direction opposite to a direction in which the drive source drives the restricting portion. The pressing portion presses the lock cover in an opening direction in conjunction with an operation of the drive source to release the engagement between the restricting portion and the lock cover.

An image forming apparatus includes a rotatable first coupling provided at a side surface of an engaging portion with a taper surface, and a unit detachably mountable in a second direction crossing with the first direction. The unit includes a second coupling, a driven member and a releasing member. The second coupling includes at an end portion thereof a portion-to-be-engaged engageable with the engaging portion to transmit the driving force, and the driven member receives the driving force from the second coupling. When the unit is disengaged from the main assembly, the releasing member is moved in the second direction in contact with the taper surface to move the first coupling away from the second coupling to effect disengagement between the engaging portion and the portion-to-be-engaged.

A gear is provided that is capable of suppressing a decrease in strength at a weld line. The gear (40) is provided with a cylindrical boss (41) that is formed at a center portion, a rim (42) that is formed on an outer side in a radial direction of the boss concentrically with the boss and has a tooth portion (42a) at an outer circumferential portion thereof, and a web (43) that links the boss and the rim. In the web, a plurality of gate marks (43a) are formed. Furthermore, in the web, there are provided a plurality of first radial direction ribs (43b) that extend from the boss to the outer side in the radial direction along a weld line (40a) that appears between adjacent ones of the gate marks.

A first gear cover has a first cover portion that covers an outer peripheral surface of a joint and that protrudes from a third outer surface in a first direction. A gear rotates about a third axis extending in the first direction by receiving driving force from coupling, and is located at a second outer surface. A second gear cover covers at least part of the gear, and has a second cover portion protruding in the first direction, and is located at the second outer surface. A first protruding portion protrudes from the first cover portion in a second direction, and is located at an opposite side from the developing roller with respect to the joint in the second direction. A second protruding portion protrudes from the second cover portion in the second direction, and is located at a same position as the first protruding portion in the second direction.

A PWM signal generation unit generates a PWM signal based on a driving voltage so that a midpoint of the longer period out of an H level period and an L level period in each PWM period matches a midpoint of the PWM period. FETs of a full bridge circuit (a driving circuit) are driven according to a PWM signal, and a driving current that corresponds to an A-phase is supplied to a stepping motor. A current detector detects a driving current flowing through an A-phase winding of the motor based on a voltage that is generated across a shunt resistor, at a fixed time point that is in each PWM period and in the H level or L level period that is at the center of the PWM period.

A sheet conveying apparatus capable of continuing conveyance of sheets without causing a jam even when a switching member performs an operation for switching a conveyance path again. A switching member is disposed at a branching point of a conveyance path through which the sheet is conveyed by a conveying unit, and is operated by a drive unit for witching a destination of conveyance of the sheet. A controller causes the drive unit to operate the switching member, and performs a checking operation for checking a state of the drive unit based on an output from a sensor that detects a state of the switching member. The controller controls a sheet conveyance interval between a first sheet conveyed by the conveying unit and a second sheet conveyed following the first sheet, according to a result of the checking operation.

A developing cartridge includes: a casing; a developing roller; a shaft; and a cam. The casing is configured to accommodate developer therein. The developing roller is rotatable about a first axis extending in an axial direction. The shaft extends along a second axis extending in the axial direction. The shaft is movable along the second axis. The cam is movable along the second axis in response to axial movement of the shaft. The cam has a cam surface non-parallel with the second axis.