Image forming apparatus

An image forming apparatus comprising:

• a transfer unit configured to transfer a developing agent image onto a sheet;
• a fixing unit comprising a heating member configured to thermally fix the developing agent image onto the sheet, and a pressing member configured to press the sheet against the heating member;
• a discharge tray configured to receive the sheet having the developing agent image fixed thereon;
• at least one pair of switchback rollers disposed upstream of the discharge tray in a conveying direction, the at least one pair of switchback rollers being configured to discharge the sheet having the developing agent image fixed thereon in the conveying direction toward the discharge tray and then switch back the sheet toward the transfer unit along a return path in a direction reverse to the conveying direction;
• and
• a corrugation system disposed away from the return path and at a conveying path extending between the fixing unit and the at least one pair of switchback rollers, the corrugation system including at least one pair of conveying rollers configured to convey the sheet passing out of the fixing unit toward the at least one pair of switchback rollers along the conveying path in the conveying direction and to form the sheet passing out of the fixing unit into a corrugated shape having at least one of a ridge portion and a groove portion in a sheet thickness direction,
• wherein the at least one pair of conveying rollers includes a first pair of conveying rollers and the corrugation system further includes a shaft that supports one roller of the first pair of conveying rollers, the shaft including a protrusion configured to contact an end portion, in a sheet width direction, of the sheet passing out of the fixing unit and to form the sheet passing out of the fixing unit into the corrugated shape, the sheet width direction being perpendicular to the conveying direction, and
• wherein the protrusion has a flange shape and protrudes radially from the shaft of the corrugation system.