Patent ID: 8213852

Claim:
An image forming apparatus having an image forming unit configured to form an image on a photosensitive member and transfer the image formed on the photosensitive member onto a sheet so that an image is formable on each of a first side and a second side of the sheet, the image forming apparatus comprising: a sheet feeding unit configured to feed the sheet to said image forming unit; a sheet re-feeding unit configured to reverse the sheet with the first side formed with an image, and re-feed, via a transport path for sheet re-feeding, the reversed sheet to said image forming unit to form an image on the second side of the sheet, the sheet re-feeding unit causing: a plurality of sheets transported in the transport path to temporarily stop at a plurality of stop positions, the sheet stopped at a most downstream stop position of the transport path to said image forming unit to be fed at predetermined re-feeding timing, and the sheets stopped at the remaining stop positions to be transported to the next stop positions; a full state detecting unit configured to detect a full state where all the plurality of stop positions are occupied by sheets; and a control device configured to: control said sheet feeding unit and said sheet re-feeding unit to continuously perform image formation on the first side of a predetermined number of sheets fed by said sheet feeding unit, and then alternately perform image formation on the second side of the sheet re-fed by said sheet re-feeding unit and the first side of a new sheet fed by said sheet feeding unit; control said sheet re-feeding unit to, when said full state detecting unit detects the full state, at a predetermined timing before the sheet with the first side formed with the image reaches the most upstream stop position among the plurality of stop positions, re-feed the sheet stopped at the most downstream stop position in advance of the predetermined re-feeding timing, and transport the sheets stopped at the remaining stop positions to the next stop positions, respectively; and control said sheet re-feeding unit to, when said full state detecting unit does not detect the full state at the predetermined timing before the sheet with the first side formed with the image reaches the most upstream stop position among the plurality of stop positions, re-feed the sheet stopped at the most downstream stop position at the predetermined re-feeding timing, and transport the sheets stopped at the remaining stop positions to the next stop positions, respectively.