A transfer unit includes first and second rollers, first and second bearing members, a roller holder, first and second urging members, a switching cam, and a driving mechanism. The switching cam includes first and second guide holes with which first and second engaging portions formed on the first and second bearing members engage. The first and second guide holes are formed, each in an approximately arcuate shape, at positions at different distances from the rotation center of the switching cam. By rotating the roller holder, one of the first and second rollers is arranged opposite an image carrying member and, by rotating the switching cam, the first or second roller arranged opposite the image carrying member is arranged selectively either at a reference position where the first or second roller is in pressed contact with the image carrying member or at a released position.

An image forming apparatus includes an image carrier that is capable of holding an image on a surface thereof while rotating, an image forming unit that forms the image on the image carrier, a transfer unit that transfers the image from the image carrier to a medium while rotating, a transport unit that circulates as the transfer unit rotates and that transports the medium to a transfer region while holding the medium, and a control unit that changes a timing at which the image forming unit forms the image in accordance with variation in a ratio of a rotation velocity of the transfer unit to a rotation velocity of the image carrier.

A belt feeding device includes an endless belt, stretching rollers including a tension roller, a bearing member supporting the tension roller, a beating support member supporting the bearing member, an urging member urging the tension roller, a supporting member supporting the bearing supporting member, and a locking member. The locking member is movable between a first position where an engagement between the locking member and one of the bearing support member and the bearing member is released and the bearing member is permitted to move so as to apply the tension to the belt, and a second position where the locking member locks the bearing member by engaging with the bearing support member and the bearing member and the bearing member is restricted to move. The bearing member, the bearing support member, the urging member, and the locking member constitute a unit to be integrally dismountable from the supporting in the second position.

An image forming apparatus includes: a rotatable transfer cylinder with a first groove formed in an outer portion thereof in a rotational radial direction that causes an image to be transferred to a recording medium when it passes along an outer surface of the transfer cylinder; a rotatable fixing cylinder that has a second groove formed in an outer portion thereof in a rotational radial direction, that causes the image transferred to the recording medium to be fixed thereto when the recording medium passes along an outer surface of the fixing cylinder; a loop-shaped circulating member that is wrapped at least around the transfer and fixing cylinders, that circulates in response to rotations of the transfer and fixing cylinders; a recording medium holding member supported by the circulating member, disposed in the first groove when the holding member passes along the transfer cylinder and disposed in the second groove when the holding member passes along the fixing cylinder; first and second driving units that rotate the transfer and fixing cylinders respectively; and that is configured such that a ratio of a moment of inertia of the fixing cylinder to an output torque of the second driving unit is set to be greater than a ratio of a moment of inertia of the transfer cylinder to an output torque of the first driving unit.

An image forming apparatus includes a drive source, an object configured to be driven by the drive source, and a drive transmission mechanism including a driving member, a driven member, an intermediate member, an urging member, and an actuating portion. The intermediate member is configured to move in an axial direction. The intermediate member includes a shaft portion extending in the axial direction, and a positioning portion configured to determine a position of the driven member in a direction orthogonal to the axis. The shaft portion includes a receiving portion configured to receive a force. The receiving portion is positioned inward of the positioning portion in a radial direction of rotation of the intermediate member.

A toner conveying device for conveying toner, comprising: a first conveying portion; and a second conveying portion conveying the toner conveyed from the first conveying portion. The first conveying portion further includes: a first screw which includes a first rotation shaft and a first blade portion, the first screw including an engaging portion and a first protruded portion on a first end portion; and a first conveying passage forming member having a first inner wall face which forms a first conveying passage. The second conveying portion includes: a second screw which includes a second rotation shaft and a second blade portion, the second screw including an engaged portion and a second protruded portion on a second end portion; and a second conveying passage forming member having a second inner wall face which forms a second conveying passage, and which is connected with the first conveying passage forming member.

An image forming apparatus includes a plurality of image bearing members, a transfer unit including an intermediate transfer belt, a plurality of transferring members which sandwich the intermediate transfer belt between the plurality of image bearing members and themselves, a biasing member which biases each of the plurality of transferring members toward the plurality of image bearing members via the intermediate transfer belt, and a frame which supports the intermediate transfer belt, the plurality of transferring members, and the biasing member, and an apparatus main body which supports the plurality of image bearing members and the transfer unit. The apparatus main body includes a supporting portion which supports the transfer unit and a biasing force receiving portion of which a position is between the plurality of transferring members in a moving direction of the surface of the intermediate transfer belt and which is capable of supporting the transfer unit.

An image forming apparatus includes an image bearer, a developing unit configured to develop a latent image formed on the image bearer with a toner to form a toner image, and a transfer member including a contact area that comes in contact with the image bearer. The toner image is primary transferred from the image bearer to the transfer member. A speed difference between the image bearer and the transfer member at the contact area is 0.1% or greater but 0.8% or less. The toner has an average circularity of 0.971 or greater but 0.986 or less and a shape factor SF-2 of 110 or greater but 119 or less. The speed difference is represented by the following formula:

[Speed Difference]

Speed difference[%]={V1−V2)/V2}×100

where V1 is a linear speed of the image bearer, and V2 is a linear speed of the transfer member.

A bearing which supports one end side of a driving roller includes a first restriction portion which is restricted from rotating and moving with respect to a first frame, and a bearing which supports the other end side of the driving roller includes a second restriction portion which is restricted from rotating and moving with respect to a second frame. As viewed from a direction perpendicular to a width direction of an intermediate transfer belt, a phase of shape of the first restriction portion in a state of being held by the first frame and a phase of shape of the second restriction portion in a state of being held by the second frame are equal to each other.

An imaging system includes: a steering roller located between a first belt roller and a second belt roller, that is inclinable around a fulcrum; and a sensor to detect an amount of displacement of the steering roller due to an inclination of the steering roller. A controller may output a command signal when the amount of displacement of the steering roller exceeds a reference value.