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.

A drive device, which is included in an image forming apparatus, includes a drive source, a drive switching device configured to switch between a transmission state and a halting state, a first rotary body having a rotary shaft, a first drive transmission passage through which a driving force is transmitted to the first rotary body, a second rotary body, a second drive transmission passage through which the driving force is transmitted to the second rotary body, a drive transmission body rotatably mounted on the rotary shaft of the first rotary body, and an input drive transmission body mounted on the rotary shaft of the first rotary body and configured to input the driving force to the rotary shaft of the first rotary body, the input drive transmission body configured to rotate together with the drive transmission body as a single unit.

An image forming apparatus includes an image forming target looped around plural rotators including a driving roller, having at least one straight portion that is shaped straight when viewed in an axial direction of the driving roller, and transported by the driving roller and the rotators, and three or more image formers arranged along the straight portion and configured to form images on the image forming target. An adjacency distance along the straight portion between the image formers adjacent to each other on the straight portion is an integral multiple of an outer peripheral length of the driving roller. The adjacency distance at a downstream end is shorter than the adjacency distance at an upstream end, and one of the adjacency distances is equal to or shorter than the adjacency distance that is relatively on an upstream side.

A drive device, which is included in an image forming apparatus, includes a drive source, a drive switching device configured to switch between a transmission state and a halting state, a first rotary body having a rotary shaft, a first drive transmission passage through which a driving force is transmitted to the first rotary body, a second rotary body, a second drive transmission passage through which the driving force is transmitted to the second rotary body, a drive transmission body rotatably mounted on the rotary shaft of the first rotary body, and an input drive transmission body mounted on the rotary shaft of the first rotary body and configured to input the driving force to the rotary shaft of the first rotary body, the input drive transmission body configured to rotate together with the drive transmission body as a single unit.

A belt drive device includes an endless belt, a plurality of tension rollers on which the belt is rotatably tensioned and a belt cleaning device. The belt cleaning device includes a cleaning blade and an opposite roller. The cleaning blade makes contact with the outer circumferential surface of the belt to remove a foreign substance adhered to the belt. The opposite roller is arranged in contact with the inner circumferential surface of the belt opposite the cleaning blade through the belt. The opposite roller includes a cover layer arranged on an outer circumferential surface, the surface resistance value of the cover layer when a voltage of 100V is applied is equal to or greater than 10 to the 10th power () and the Asker A hardness of the cover layer is equal to or greater than 60 and equal to or less than 90.

A first stretch roller stretches a secondary transfer belt at a position where a tip in a conveying direction of a recording medium being conveyed through a secondary transfer portion can reach. The first stretch roller has a circumferential surface formed into a normal crown shape in which a straight area where a diameter of the first stretch roller is constant is provided at a center part in a direction of axis of rotation. A second stretch roller has a circumferential surface formed into an inverse crown shape in which a straight area where a diameter of the second stretch roller is constant is provided at a center part in a direction of axis of rotation.

A sheet transport apparatus includes a first belt having a first pattern of first vacuum holes, and a second belt having a second pattern of second vacuum holes. The first belt is positioned on and contacts the second belt. The first belt contacts sheets to be transported. When transporting the sheets on the first belt separated by spaces between the sheets, the first pulleys and second pulleys rotate together and the first belt and the second belt move together. When not transporting the sheets, a controller controls pulleys to move the first belt relative to the second belt so as to leave blocked-hole regions of the first belt where the spaces between the sheets are located. The blocked-hole regions are locations of the first belt where the first vacuum holes are unaligned with the second vacuum holes and the first vacuum holes are blocked by the second belt.