Image forming apparatus with loop detection and conveyance speed control

An image forming apparatus comprising:

• a first sheet conveying unit which conveys a sheet;
• a second sheet conveying unit which is provided downstream of the first sheet conveying unit and conveys the sheet;
• a loop detecting unit which detects the sheet whose loop is formed between the first sheet conveying unit and the second sheet conveying unit;
• and
• a control unit which controls a sheet conveying speed of at least one of the first sheet conveying unit and the second sheet conveying unit so as to form the loop during the sheet conveyance process, wherein the control unit includes a memory in which is set a presumption time, the presumption time approximating a time period from when a leading edge of a sheet has first arrived at the second sheet conveying until when it is presumed that the loop detecting unit will have detected a sheet whose loop is formed,
• wherein when the presumption time has elapsed, if the loop detecting unit has not yet detected a loop, the control unit controls the sheet conveying speed so as to reduce an amount of a loop which is formed in the sheet until an elapse of a setting time previously set, and
• wherein when the presumption time has elapsed, if the loop detecting unit has detected a loop, the control unit controls the sheet conveying speed so as to convey the sheet while keeping an amount of the detected loop which is formed in the sheet in a predetermined range.