The belt conveyance device includes an endless belt member, and a steering roller that stretches the belt member and has a tiltable rotation axis. The steering roller includes a roller that slides on the belt member and rubbing members that rub against the belt member at both ends of the roller. One or a plurality of recessed portions is formed in the surface of each rubbing member in an area where the surface of the rubbing member is opposed to an inner surface of the belt member.

In one example, an apparatus includes a plate configured to pivot about a pivot point, a pulley coupled to a first planar side of the plate and configured to rotate a belt, a motor coupled to the first planar side of the plate and configured to drive the pulley, and a torsion spring coupled to a second planar side of the plate that is opposite the first planar side and configured to apply tension to the belt.

There is provided an electrophotographic photosensitive member having a cylindrical shape, including a plurality of concave portions on a surface thereof, wherein a sum of opening areas of the concave portions is 5% or more and 65% or less based on a total area of a surface layer of the electrophotographic photosensitive member, an average value davg of depths of the concave portions satisfies the following Equation (1),
0.4davg3.0(m)Equation (1) a sum of opening areas of concave portions having a specific depth d is 95% or more of the sum of the opening areas of the concave portions, an average value Lavg of maximum widths of openings of the concave portions in a circumferential direction of the electrophotographic photosensitive member is 20 m or more and 200 m or less, and the electrophotographic photosensitive member has at least one specific region B.

An image forming apparatus includes a plurality of image forming portions; a rotatable endless belt; a plurality of stretching rollers including an inner roller and a steering roller; an outer roller; a steering mechanism; a position changing mechanism; and a controller. In a case that a changing operation for changing a position of the inner roller is performed by the position changing mechanism during execution of a job for forming the toner images on a plurality of recording materials, the controller controls the steering mechanism so that a tilting operation for tilting the steering roller in a predetermined amount in interrelation with the changing operation is executed.

There is provided an electrophotographic photosensitive member having a cylindrical shape, including a plurality of concave portions on a surface thereof, wherein a sum of opening areas of the concave portions is 5% or more and 65% or less based on a total area of a surface layer of the electrophotographic photosensitive member, an average value davg of depths of the concave portions satisfies the following Equation (1),

0.4davg3.0 (m)Equation (1) a sum of opening areas of concave portions having a specific depth d is 95% or more of the sum of the opening areas of the concave portions, an average value Lavg of maximum widths of openings of the concave portions in a circumferential direction of the electrophotographic photosensitive member is 20 m or more and 200 m or less, and the electrophotographic photosensitive member has at least one specific region B.

The belt conveyance device includes an endless belt member, and a steering roller that stretches the belt member and has a tiltable rotation axis. The steering roller includes a roller that slides on the belt member and rubbing members that rub against the belt member at both ends of the roller. One or a plurality of recessed portions is formed in the surface of each rubbing member in an area where the surface of the rubbing member is opposed to an inner surface of the belt member.

An image forming apparatus includes an electrophotographic photoreceptor that includes a conductive substrate and a photosensitive layer disposed on the conductive substrate, the electrophotographic photoreceptor having an outermost surface layer that contains a binder resin, a charge-transporting material, and a fluorine-containing resin particle, the fluorine-containing resin particle containing 0 or more and 30 or less carboxy groups per 10.sup.6 carbon atoms, a charging device that charges the electrophotographic photoreceptor, an electrostatic latent image forming device that forms an electrostatic latent image on the electrophotographic photoreceptor that is charged, a developing device that houses a developer containing a toner and that develops, with the developer, the electrostatic latent image formed on the electrophotographic photoreceptor into a toner image, a transfer device that transfers the toner image onto a transfer-receiving medium, and an optical discharging device that, after the toner image is transferred onto the transfer-receiving medium and before the electrophotographic photoreceptor is charged, irradiates the electrophotographic photoreceptor with discharging light with a light quantity of 1.0 ?W or more and 50.0 ?W or less to perform discharging.

A contact-and-separation system includes a first roller, a second roller, and a contact-and-separation device. The first roller contacts a belt. The second roller is opposed to the first roller. The contact-and-separation device contacts or separates the belt to or from the second roller via a sheet conveyed. The contact-and-separation device includes an eccentric cam, a motor, and a circuitry. The eccentric cam is mounted on an end of a rotation shaft of the first roller. The motor rotates the eccentric cam. The circuitry controls the motor to rotate the eccentric cam to contact or separate the belt to or from the second roller via the sheet conveyed. The circuitry controls the motor to decelerate a rotation speed of the motor on contact or separation of the belt to or from the second roller between the first roller and the second roller.

In an electrophotographic photosensitive member, a circumferential surface has concave portions that are independent one another; each of the concave portions has an opening, a contour of the opening has an apex having an angle of more than 0 and 90 or less on at least an upstream side of a rotational direction of the electrophotographic photosensitive member, and has a largest width in an axial direction of the electrophotographic photosensitive member of 20 m or more and 80 m or less, a width of the contour in the axial direction of the electrophotographic photosensitive member decreasing from a portion having the largest width toward the apex, when viewing each of the concave portions in the axial direction, each of the concave portions has a depth that decreases from a deepest point of each of the concave portions toward the apex.

An image-forming apparatus includes a main body, a belt unit detachably attachable to the main body, a coupling and a restricting part. The belt unit includes: a first roller defining an axis extending in an axial direction, a second roller opposing the first roller in a first direction perpendicular to the axial direction, and a belt looped over the first roller and the second roller. The coupling is configured to move in the axial direction to come into engagement with the first roller for inputting a drive force into the first roller. The restricting part is provided on the main body and is configured to restrict the first roller from moving in a second direction perpendicular to the axial direction and the first direction when the belt unit is attached to the main body.