An image forming apparatus which includes a rotary member and a detecting member configured to detect light from a surface of the rotary member. A controller is configured to acquire information relating to a position on the rotary member in a moving direction thereof based on a detection result obtained by the detecting member. The surface of the rotary member has, in a part of the rotary member in its moving direction, an area with a different detection result obtained by the detecting member based on a shape of the surface of the rotary member. The controller acquires the information relating to the position on the rotary member in the moving direction based on the detection result of detecting light from the surface of the rotary member by the detecting member.

An intermediate transfer belt assembly includes an intermediate transfer belt, a driving roller, a backup roller, a driving frame; and a backup frame. The driving roller and the backup roller spaced apart from each other to support and move the intermediate transfer belt in a first direction. The driving frame is to rotatably support the driving roller. The backup frame is connected to the driving frame, is to rotatably support the backup roller and is to move in the first direction.

An electrophotographic belt including: a base layer, an elastic layer formed on the base layer, and a surface layer formed on the elastic layer. The surface layer contains a binder resin and polytetrafluoroethylene particles. A content of the polytetrafluoroethylene particles is 200 parts by mass or more with respect to 100 parts by mass of the binder resin. The polytetrafluoroethylene particles have a number average particle diameter of 200 nm or less.

An electrophotographic belt having an endless shape and including an endless-shaped base layer, an elastic layer on an outer peripheral surface of the base layer, and a surface layer on the outer peripheral surface of the elastic layer, and the surface layer contains a urethane resin as a binder, polytetrafluoroethylene particles, and a compound having a perfluoropolyether structure and an oxyalkylene structure.

Provided is an electrophotographic belt having a cylindrical film as a base layer. The cylindrical film contains crystalline polyester and carbon black, and a content of the carbon black in the cylindrical film is 2.0% by mass or more. Fc1 is 0.30 or more, and Φc1 being -10° to +10°, where Fc1 denotes an average degree of arrangement of the carbon black in the circumferential direction observed in a cross section in a direction along a circumferential direction of the cylindrical film, and Φc1 denotes an average arrangement angle of the carbon black in the circumferential direction observed in a cross section in a direction along a circumferential direction of the cylindrical film.

An intermediate transfer belt includes a single-layer body including a resin layer or a multilayer body including the resin layer serving as a top surface layer. The surface of the resin layer has an arithmetic average surface height Sa of 0.005 μm or more and 0.020 μm or less. The surface of the resin layer has a maximum height Sz of 0.050 μm or more and 0.200 μm or less. The surface of the resin layer has recesses having a depth of 0.050 μm or more, the recesses being arranged at a regular interval, and the interval of the recesses is 0.20 μm or more and 0.80 μm or less.

An image forming apparatus includes a developer that forms a toner image on an endless belt that is suspended over outer portions of a plurality of rollers, a driver that rotates at least one driving roller out of the plurality of rollers, a position adjustment mechanism that corrects relative positions of the plurality of rollers relative to one another, and a hardware processor, wherein the hardware processor controls the position adjustment mechanism to correct a relative position between the belt and the driving roller with tension applied to the belt being a second tension smaller than a first tension that is applied in a developing state in which a toner image is formed on the belt by the developer.

An image forming apparatus employs a constitution in which, in a case that a relative position between an inner roller and an outer member with respect to a circumferential direction of the inner roller is changed in a period after a preceding recording material passes through a transfer portion and until a recording material subsequent to the preceding recording material reaches the transfer portion during execution of a job for forming and outputting images on a plurality of recording materials, a controller controls a position changing mechanism and a contact and separation mechanism so that a separating operation for separating the outer roller from a belt is performed and then the above-described relative position is changed.

A transfer device includes: an endless member in an endless shape that orbits; primary transfer members that are respectively arranged on an opposite side of plural image holding bodies disposed side by side in a circumference direction of the endless member with the endless member interposed between the primary transfer member and the image holding body, and transfer an image held by the image holding body to the endless member; a secondary transfer member that transfers the image transferred to the endless member to a recording medium; an applying roll around which the endless member is wound, that is disposed on a downstream side of all the primary transfer members and on an upstream side of the secondary transfer member in the circumference direction, and that urges the endless member from an inner peripheral surface of the endless member to apply tension to the endless member; an upstream roll around which the endless member is wound, and that is disposed on the downstream side of all the primary transfer members and on an upstream side of the applying roll in the circumference direction; a contact and detachment member that moves at least some of the plural primary transfer members, and contacts and detaches the endless member and the image holding body to change a posture of the endless member; a detection member that faces a portion of the endless member between the upstream roll and the applying roll to detect the image transferred to the endless member; and a positioning mechanism that changes a posture of the detection member according to the change in the posture of the endless member to position the detection member at the endless member.

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.