An image forming apparatus includes an image forming portion, a belt, a plurality of stretching rollers including an inner roller and an upstream roller, an outer member, an urging member, a first position changing mechanism, a storing portion, a controller, and an operating portion. The controller controls the first position changing mechanism on the basis of a kind of a recording material on which an image is formed, first set information stored in the storing portion, and first input information for changing setting of a position of the urging member inputted to the controller through the operating portion.

An image forming apparatus 100, employs a constitution in which in a case that a relative position between an inner roller 32 and an outer member 41 with respect to a circumferential direction of the inner roller 32 is changed in a period after a preceding recording material S passed through a transfer portion N2 and until the recording material S subsequent to the preceding recording material S reaches the transfer portion N2 device execution of a job for forming and outputting images on a plurality of recording materials S, a controller 150 controls a position changing mechanism 1 so that the above-described relative position is changed in a state in which the outer member 41 contacts the intermediary transfer belt 31.

An image forming apparatus 100 employs a constitution in which in a case that a relative position between an inner roller 32 and an outer member 41 with respect to a circumferential direction of the inner roller 32 is changed in a period after a preceding recording material S passes through a transfer portion N2 and until a recording material S subsequent to the preceding recording material S reaches the transfer portion N2 during execution of a job for forming and outputting images on a plurality of recording materials S, a controller 150 controls a position changing mechanism 1 and a contact and separation mechanism 2 so that a separating operation for separating the outer roller 41 from the belt 31 and then the above-described relative position is changed.

In an image forming apparatus 100, in a case that a relative position between an inner roller 32 and an outer member 41 with respect to a circumferential direction of the inner roller 32 is changed in a period from a state in which the outer member 41 is separated from a belt 31 until first transfer in a job for forming and outputting an image on a recording material S is started when the job is executed, said controller 150 controls a position changing mechanism 1 and a contact and separation mechanism 2 so that a contact operation for bringing the outer member 41 into contact with the belt 31 after changing the relative position.

A drum member includes: a substantially cylindrical drum body having a hollow part extending in an axial direction; a sheet member wound on the drum body; an adjusting mechanism configured to adjust tension in the sheet member, the adjusting mechanism including a moving member that holds an end of the sheet member in a circumferential direction and moves in a depth direction of the hollow part, and a fixing member that fixes the moving member to the drum body; and one or more positioning members that position the moving member such that the moving member does not move in the circumferential direction of the drum body when the moving member is fixed with the fixing member.

An image forming apparatus includes a plurality of image bearers, a plurality of rotation reference position detectors, and circuitry. Each of the plurality of rotation reference position detectors faces a corresponding image bearer of the plurality of image bearers to detect a rotation reference position of the corresponding image bearer. The circuitry performs, before an operation of rotating the plurality of image bearers, alignment control based on a result of detection performed by the plurality of rotation reference position detectors. The alignment control is control of driving of the plurality of image bearers to acquire a given relationship between the respective rotation reference positions of the plurality of image bearers. The circuitry determines whether to perform the alignment control based on whether the operation of rotating the plurality of image bearers is a function maintenance related operation.

A cam driver includes a support, a cam, a motor, and a retracting torque applicator. The support supports an object. The cam moves the support. The motor rotates the cam and maintains a position of the cam. The retracting torque applicator applies torque to the cam in a direction to move the object away from a counter object that faces the object.

A transfer member includes: an inner layer; an outer layer provided on an outer periphery of the inner layer; and a surface layer provided on an outer periphery of the outer layer, both end portions of the surface layer in circumferential directions extending in the circumferential directions from both end portions of the outer layer in the circumferential directions.

An intermediate transfer unit includes an intermediate transfer belt, a. driving roller, a. tension roller, and a roller supporting frame. The roller supporting frame includes first and second supporting frames, and has a coupling portion formed on it. The coupling portion includes a rotary shaft and a. shall hole. The roller supporting frame shifts from a first state to a second state by rotating the first supporting frame in the forward direction to have the intermediate transfer belt wound around it. The rotary shaft includes a projection. A shaft hole has a restricting wall portion. As the first supporting frame in the second state rotates in the forward direction, the projection makes contact with the restricting wall portion to restrict rotation of the first supporting frame in the forward direction.

A belt driving device includes an adjustment roller to stretch and rotate an endless belt; an inclination adjuster including a cam to adjust inclination of the roller to control deviation of the belt; a belt position detector to detect a belt position in a direction orthogonal to a movement direction of the belt; a stepping motor to rotate the cam; and a control output adjuster to adjust a control output to be supplied to the motor based on the belt position. When obtaining a rotation angle less than one step of the motor, the control output adjuster supplies the control output to the motor for a time corresponding to the rotation angle less than the one step out of a supply time of the control output for obtaining a rotation angle of the one step, and stops supplying the control output for a remaining time out of the supply time.