Image forming apparatus

An image forming apparatus comprising:

• a sheet feed portion that feeds a sheet used in a print job into a sheet conveying passage;
• a conveying portion that conveys the sheet fed into the sheet conveying passage;
• a sheet feed sensor that has a detection position at a position previously determined in the sheet conveying passage, the sheet feed sensor changing an output thereof according to whether or not a sheet is present at the detection position;
• and
• a control portion that controls the sheet feed portion and the conveying portion, the control portion sensing an arrival of a tip end of and a passage of a rear end of a sheet at the detection position based on an output of the sheet feed sensor,
• wherein
• the sheet feed sensor includes
• a first sensor having the detection position at a first position in the sheet conveying passage, and
• a second sensor having the detection position at a second position on the downstream side, in the sheet conveying direction, of the first position in the sheet conveying passage,
• the control portion sets
• a first time equal to a time obtained by adding a first margin time to a first theoretical time required from a start of feeding of a sheet by the sheet feed portion to the passage of the rear end of the sheet at the first position, and
• a second time equal to a time obtained by adding a second margin time to a second theoretical time required from the start of the feeding of a sheet by the sheet feed portion to the passage of the rear end of the sheet at the second position, and
• the control portion
• performs, based on the output of the first sensor, first sensing in which the control portion senses whether or not the rear end of the sheet has passed the first position within the first time of the start of the feeding of the sheet by the sheet feed portion,
• performs, based on the output of the second sensor, second sensing in which the control portion senses whether or not the rear end of the sheet has passed the second position within the second time of the start of the feeding of the sheet by the sheet feed portion, and,
• even if unable to sense the passage of the rear end of the sheet in the first sensing, when the passage of the rear end of the sheet is sensed in the second sensing, makes the conveying portion continue feeding the sheet.