An image forming apparatus includes an image forming unit configured to form an image on a sheet based on image forming condition, a reader configured to convey the sheet and read a test image on the sheet while the sheet is conveyed, and a controller configured to control the image forming unit to form the image and the test image on a same sheet, control the reader to read the test image on the same sheet, and generate the image forming condition for adjusting a density of an image to be formed by the image forming unit, based on a reading result of the test image by the reader.

A rotating device includes: a first rotating body capable of forward rotation; a second rotating body capable of forward rotation and reverse rotation; a drive unit outputting drive forces in a forward rotation direction and a reverse rotation direction; and a transmission mechanism transmitting the drive force in the forward rotation direction output from the drive unit to the first rotating body and the second rotating body to rotate the first rotating body and the second rotating body in the forward direction and transmitting the drive force in the reverse rotation direction output from the drive unit to the first rotating body and the second rotating body to rotate the first rotating body in the forward direction and rotate the second rotating body in the reverse direction.

An image forming apparatus includes: a holding unit that holds a recording medium transported; a circumferential rotation unit that circumferentially rotates with the holding unit fixed, and constitutes part of a transport path along which the recording medium is transported; an image former that forms an image on the recording medium at an image formation position on a circumferential rotational path of the circumferential rotation unit; a pass point at which the recording medium is passed on the circumferential rotational path; and a receiving point which is provided on a same side as the pass point with respect to the image formation position, and at which the recording medium is received from the circumferential rotational path.

An image forming apparatus includes: a forming part that forms an image on a recording medium; a fixing part that fixes the image formed on the recording medium; a revolving part having a revolving member stretched over multiple rotary members, the revolving member revolving between the forming part and the fixing part to transport the recording medium from the forming part to the fixing part; a feed part that feeds the recording medium to the forming part; a discharge part that discharges the recording medium to which the image has been fixed in the fixing part; a branch part that is provided so as to be split from the discharge part and along which the recording medium, to one side of which the image has been fixed, is transported to the feed part after switching the leading end and the trailing end of the recording medium; a first housing accommodating the forming part, the fixing part, and the revolving part; and a second housing connected to the first housing and accommodating the feed part, the discharge part, and the branch part.

An image forming apparatus includes: an apparatus body; an image forming unit that forms a toner image on a recording medium; a first transport part that transports the recording medium to the image forming unit along a feed path extending from one side toward the other side in the horizontal direction, the feed path being a path along which the recording medium transported by the first transport part passes, and that includes a portion extending toward the one side beyond the image forming unit; and a second transport part that transports the recording medium from the image forming unit to the outside of the apparatus body along a discharge path extending from the other side toward one side in the horizontal direction and that includes a portion extending toward the one side beyond the image forming unit, the discharge path and the feed path at least partially overlapping each other in the vertical direction.

An image forming apparatus includes first and second light emitting units, a light receiving unit for receiving light of the first light emitting unit when it is reflected, and receiving light of the second light emitting unit when it is not reflected, to output a signal of a predetermined level, and a control unit for starting light emission of the first light emitting unit before a front end of a paper sheet reaches an area, stopping light emission of the first light emitting unit while starting light emission of the second light emitting unit before a rear end of the paper sheet passes the area, and detecting a length of the paper sheet based on time after the output signal becomes a predetermined level during light emission of the first light emitting unit until the output signal becomes the predetermined level during light emission of the second light emitting unit.

An image forming apparatus configured to form images on both sides of a sheet, includes an image forming unit, which is configured to form an image on an image bearing member, and a sheet conveying device, which is configured to move the sheet being conveyed toward a width direction, which is orthogonal to a conveyance direction. After the formed image is transferred onto a first surface of the sheet, the image forming apparatus inverts and conveys the sheet to transfer an image onto a second surface. Moreover, a side edge position of the sheet in the width direction is detected during conveyance for the transferring onto each of the first surface and the second surface, and an image writing start position for the image forming unit is determined based on a result of the detection to store a result of the determination in a memory.

An image forming apparatus, including: a sheet cassette; an image former; a fixer; a discharge tray; a conveyor configured to convey a sheet along a conveyance passage; a return conveyor configured to convey the sheet from a branch position between the fixer and the discharge tray to a merge position between the sheet cassette and the image former along a return passage which is branched from the conveyance passage at the branch position, passes below the sheet cassette, and merges with the conveyance passage at the merge position; a switchback roller disposed between the branch position and the discharge tray in the conveyance passage and configured to convey the sheet to the discharge tray when it rotates forwardly and to the return passage when it rotates backwardly; and an intermediate conveyance roller disposed in the return passage at a height level intermediate between the fixer and the sheet cassette.

An image forming apparatus includes: a toner image forming section; a transfer section; a fixing section; a conveyance roller section disposed on a downstream side of the fixing section in a sheet conveyance direction; a conveyance guide section disposed on a downstream side of the conveyance roller section and including a first guide member disposed on a fixing side of a sheet and a second guide member disposed on a rear surface side of the sheet; a feeding-path-switching section disposed on a downstream side of the conveyance guide section and configured to switch sheet feeding paths; and a nip angle adjusting section configured to change a nip angle of a conveyance nip in accordance with whether a sheet on which an image is formed on a first surface thereof is conveyed, or a sheet on which an image is formed on a second surface thereof is conveyed.

The electro-photographic sheet of paper duplex printing machine includes a sheet supply section, a sheet positioning section which positions sheets and sends out sheets to a backup roller in an electro-photographic printing section, the electro-photographic printing section transfers an image which has been transferred onto the transfer roller onto the sheet, a chain delivery section, a delivery section and a sheet carrying section for turnover. The chain delivery section selectively transfers printed sheets, which has been transferred from the backup roller to the delivery section or sheet carrying section for turnover. The sheet carrying section for turnover supplies one side printed sheet to the sheet positioning section. The sheet fed from the sheet supply section and one side printed sheet fed from the sheet carrying section for turnover are alternately carried to the sheet positioning section and the toner image on the printed sheet is fixed by the fixing device.