Provided are an image forming apparatus and an image forming method capable of coping with a medium exceeding a transport limit of a pair of rollers in image formation in which the medium is transported with the medium interposed between the pair of rollers. In a case where a medium exceeding a transport limit of first transport means to which medium transport using a first roller and a second roller is applied is used, second transport means is used to assist in the medium transport performed by the first transport means. The driving of second driving means for driving the second transport means is controlled using a driving signal applied to the driving control of the first driving means for driving the first transport means. Medium transport in which synchronization is taken between the first transport means and the second transport means is realized.

A paper feeding device includes a pickup roller mechanism disposed at an entrance of a paper feeding path, and a separation mechanism disposed to a rear end of the pickup roller mechanism. The pickup roller mechanism includes a first pickup unit positioned at the entrance of the paper feeding path, a second pickup unit mounted to a rear end of the first pickup unit, and a third pickup unit disposed to a rear end of the second pickup unit. The second pickup unit includes a first driving gear. The third pickup unit includes a second driving gear, and a transmission belt looped around an outer periphery of the first driving gear and an outer periphery of the second driving gear.

An image reading apparatus includes a supporting portion, a feeding portion, a curved conveyance path, a conveyance unit, an image reading unit, a driving source, an output pulley, an input pulley, a first pulley, a second pulley, a driving belt, and a transmission belt. The image reading unit is configured to read an image on a first surface at a location between the first driving roller and the second driving roller in a sheet conveyance direction. The output pulley is fixed to an output shaft of the driving source. The input pulley is fixed to the second driving roller. The first pulley is fixed to the first driving roller. The second pulley is fixed to the second driving roller. The driving belt is wound around the output pulley and the input pulley. The transmission belt is wound around the first pulley and the second pulley.

An image reading apparatus includes a conveyance unit, an image reading unit, a driving source, a first pulley, a second pulley, and a transmission belt. The conveyance unit including a first driving roller and a second driving roller and configured to convey a sheet. The image reading unit configured to read an image on the sheet conveyed by the conveyance unit at a reading position between the first driving roller and the second driving roller in a sheet conveyance direction. The driving source configured to output a driving force for driving the first driving roller and the second driving roller. The first pulley fixed to the first driving roller. The second pulley fixed to the second driving roller. The transmission belt wound around the first pulley and the second pulley. An outer diameter of the second pulley is smaller than an outer diameter of the first pulley.

A sheet separation device separates a non-bonding portion of a two-ply sheet in which two sheets are overlapped and bonded together at one end of the two-ply sheet. The sheet separation device includes a separator that includes a first separator and a second separator. The first separator is inserted into a gap between the two sheets of the two-ply sheet. The second separator is inserted between the two sheets at said another end of the two-ply sheet that is opposite to the one end of the two-ply sheet and moves in a width direction of the two-ply sheet after the first separator is inserted into the gap and relatively moves from the one end to said another end.

A sheet separation device separates a non-bonding portion of a two-ply sheet in which two sheets are overlapped and bonded together at one end of the two-ply sheet. The sheet separation device includes a separator that includes a first separator and a second separator. The first separator is inserted into a gap between the two sheets of the two-ply sheet. The second separator is inserted between the two sheets at said another end of the two-ply sheet that is opposite to the one end of the two-ply sheet and moves in a width direction of the two-ply sheet after the first separator is inserted into the gap and relatively moves from the one end to said another end.

A drive transmission device includes a plurality of pulleys including three or more pulleys, and an endless belt stretched over the plurality of pulleys and in which a plurality of linear belt sections each formed between two of the pulleys are formed, wherein a first flange is provided on a first pulley which is the pulley that forms a longest belt section and does not form a shortest belt section among the plurality of belt sections, and a gap between the first flange and a side surface of the endless belt is smaller than a gap between a flange provided on another pulley and the side surface of the endless belt.

An image reading apparatus includes a supporting portion, a feeding portion, a curved conveyance path, a conveyance unit, an image reading unit, a driving source, an output pulley, an input pulley, a first pulley, a second pulley, a driving belt, and a transmission belt. The image reading unit is configured to read an image on a first surface at a location between the first driving roller and the second driving roller in a sheet conveyance direction. The output pulley is fixed to an output shaft of the driving source. The input pulley is fixed to the second driving roller. The first pulley is fixed to the first driving roller. The second pulley is fixed to the second driving roller. The driving belt is wound around the output pulley and the input pulley. The transmission belt is wound around the first pulley and the second pulley.

A sheet conveyance apparatus includes a drive transmission mechanism configured to transmit a driving force from a driving source to a rotary conveyance member. The drive transmission mechanism includes a shaft, a first rotary member supported on the shaft and configured to rotate by being driven by the driving source, a second rotary member supported on the shaft and configured to rotate the rotary conveyance member, a drive transmission member provided movably in an axial direction of the shaft, and configured to transmit the driving force between the first rotary member and the second rotary member, and a moving unit configured to move the drive transmission member to a transmission position and a release position. The drive transmission member engages the first and second rotary members with each other at the transmission position, and releases engagement of the first and second rotary members at the release position.

A printer includes a platen roller, a first pulley connected to the shaft of the platen roller, a motor, a second pulley connected to the shaft of the motor, and a belt wrapped around the first pulley and the second pulley. At least one of the first pulley and the second pulley has a variable diameter.