Patent ID: 8050616
Filing Date: 2011-11-01
Classification: B65H,G03G

Abstract:
1. An image forming apparatus comprising: an image forming section for forming an image on a sheet; a registration roller for sending a sheet to the image forming section in a sheet conveyance direction after correcting a skew of the sheet by allowing a leading edge of the sheet to come in contact with the registration roller and by stopping the leading edge of the sheet temporarily; a plurality of loop forming devices which are on an upstream side of the registration roller and which convey a sheet to the registration roller and form a loop of the sheet between the registration roller and the plurality of loop forming devices; a plurality of loop amount detecting devices which are placed between the registration roller and the plurality of loop forming devices and which detect an amount of the loop of the sheet at a plurality of locations across a width of the sheet in a direction perpendicular to the sheet conveyance direction; and a control device which (i) performs control to temporarily stop the leading edge of the sheet by allowing the leading edge of the sheet to hit the registration roller while the registration roller is stopped and to form a loop between the plurality of loop forming devices and the registration roller to correct the skew of the sheet, and (ii) then performs control to start to convey the sheet by the plurality of loop forming devices and the registration roller simultaneously; wherein the control device individually controls a sheet conveyance speed of each of the plurality of loop forming devices to provide a difference in the sheet conveyance speed between the plurality of loop forming devices based on a result of detection of each of the plurality of loop amount detecting devices for the sheet being conveyed so that an amount of the loop is made and kept uniform across a full width of the sheet in a direction perpendicular to the sheet conveyance direction while the registration roller is conveying the sheet.