A post-processing device includes an output unit that outputs a medium; a stacking unit on which the medium that is output is stacked; and a blow-out unit that is disposed below the output unit and that blows gas toward the medium that is output, wherein an amount of the gas blown is adjusted in accordance with a type of the medium.

An improved image forming apparatus includes an image bearer, a nip forming member, a transfer power source, and a controller. The controller switches a transfer mode between a first mode to transfer the toner image onto a first type sheet having a surface smoothness higher than a surface smoothness of a second type sheet and a second mode to transfer the toner image onto the second type sheet. The controller controls the transfer power source to output the transfer bias having an opposite-peak duty of greater than or equal to 50% that is a duty on the side of the opposite-peak value in the first mode. The controller controls the transfer power source to output the transfer bias having an opposite-peak duty of less than 50%, which is different from the opposite-peak duty of the first mode, in the second mode.

An image forming apparatus includes an image bearing member, an image forming portion, an endless belt, a plurality of stretching rollers including an inner roller, an outer roller, a position changing mechanism capable of changing a position of the inner roller to a first position and a second position positioned downstream of the first position with respect to a rotational direction of the endless belt, a feeding member, a feeding member driving portion, and a controller. A feeding start timing of a recording material by the feeding member depends on the position of the inner roller during transfer of a toner image onto the recording material.

An image forming apparatus determines, in a first mode, an image forming condition according to characteristic data, which is input by a user and represents characteristics of a sheet contained in a sheet container, causes the sensor to detect characteristics of a sheet, and stores characteristic data according to a result of the detection into the memory. The image forming apparatus determines, in a second mode with the characteristic data being stored in the memory, an image forming condition, based on the characteristic data stored in the memory before a result of detecting a characteristic of a sheet by the sensor is obtained. The image forming apparatus causes, in the second mode with the characteristic data being not stored in the memory, the sensor to detect characteristics of a sheet, and determines an image forming condition based on a result of the detection.

An image forming apparatus includes a memory and a controller. The memory is configured to store information related to a recording medium type detected by a detector in the past. The controller is configured to control a feeder so as to prevent feeding of a recording medium from starting, when a printing operation is started in a first mode, in a case that a recording medium type set through a setting unit and a recording medium type discriminated based on the information stored in the memory do not match with each other.

A sheet processing apparatus that can suppress a reduction in a quality of a finish of a fold part of a stack of center-folded sheets without losing an ease of center-folding. The sheet processing apparatus comprises a creasing unit for forming a folding stripe on a sheet so as to facilitate folding the sheet, and an acquisition unit for acquiring information related to a thickness of the sheet. One or more sheets to be provided with folding stripes are determined, from among a plurality of sheets to be folded, according to the information related to the thickness of the sheets, and each of the determined one or more sheets are provided with a folding stripe.

An image forming apparatus includes an image bearing member, an image forming portion, an endless belt, a plurality of stretching rollers including an inner roller, an outer roller, a position changing mechanism capable of changing a position of the inner roller to a first position and a second position positioned downstream of the first position with respect to a rotational direction of the endless belt, a feeding member, a feeding member driving portion, and a controller. A feeding start timing of a recording material by the feeding member depends on the position of the inner roller during transfer of a toner image onto the recording material.

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 includes an image forming portion, a belt, an inner roller, an outer member, an inner roller position changing mechanism, an acquiring portion, and a controller. In a case that second information acquired by the acquiring portion shows that first and second recording materials are coated paper, the controller controls a position changing mechanism so that a position of the inner roller when a toner image is transferred onto the second recording material is changed to a second position. In a case that the second information acquired by the acquiring portion shows that the first and second recording materials are plain paper, the controller controls the position changing mechanism so that the position of the inner roller when the toner image is transferred onto the second recording material is maintained at a first position.

An image forming system including: a reading unit configured to read, through a transparent member, an image on a first sheet conveyed by a conveyance unit; an opposed member provided opposite to the reading unit with respect to the transparent member, the first sheet passing through a gap between the opposed member and the transparent member; and at least one processor configured to control, based on the image read by the reading unit, a geometric characteristic of an image to be formed on a second sheet by an image forming portion, and control a changing unit to change the size of the gap to a first size when the thickness of the first sheet is a first thickness, and to a second size larger than the first size when the thickness of the first sheet is a second thickness larger than the first thickness.