Patent ID: 8055179

Claim:
An image forming apparatus comprising: a first feeding unit adapted to feed a recording sheet from a container containing the recording sheet; an image forming unit adapted to form an image on the recording sheet; a second feeding unit adapted to re-feed to said image forming unit the recording sheet having the image formed on a first surface thereof by the image forming unit so that an image is formed on a second surface opposite to the first surface; a post-processing unit adapted to perform a post-processing on the recording sheet having an image formed thereon; a both-sides image formation control unit adapted to perform either of a first both-sides image forming processing or a second both-sides image forming processing by controlling said image forming unit, said first feeding unit, and said second feeding unit, wherein the first both-sides image forming processing controls, for at least one time, said first feeding unit to successively feed a plurality of recording sheets, and said image forming unit to successively form an image on the first surface of each of the plurality of recording sheets, thereafter said second feeding unit to feed the plurality of recording sheets, and said image forming unit to successively form an image on the second surface of each of the plurality of recording sheets, and the second both-sides image forming processing controls said first feeding unit to successively feed a predetermined number of recording sheets, said image forming unit to successively form an image on the first surface of each of the recording sheets, thereafter said second feeding unit and said first feeding unit to alternately feed the recording sheets, said image forming unit to alternately form an image on the second surface of the recording sheet fed from said second feeding unit and form an image on the first surface of the recording sheet fed from said first feeding unit, thereafter said second feeding unit to feed the predetermined number of recording sheets, and said image forming unit to form an image on the second surface of each of the recording sheets; a time period computing unit adapted to compute a first time period needed by the first both-sides image forming processing and a second time period needed by the second both-sides image forming processing in a case where said post-processing unit performs the post-processing on the recording sheet formed images on both sides thereof; and a both-sides image forming processing selection unit adapted to compare the first time period and the second time period computed by said time period computing unit and adapted to select any one of the first both-sides image forming processing and the second both-sides image forming processing based on the comparison.