Image forming apparatus with smooth transfer sheet roller transport

Abstract

A copying machine that is capable of copying a large-size document original on a transfer sheet is provided in which the transfer sheet is prevented from being skewed from the desired transport path. In one embodiment, this bypass transportation path for a cut-sheet extends to a photoreceptor drum and is provided with a resist roller and a downstream transportation roller. A cut-sheet inserted from a manual sheet feeding section is stopped with its leading edge abutting against the resist roller, so that the leading edge of the cut-sheet is aligned with a line perpendicular to a transportation direction of the sheet. The cut-sheet is then transported by the resist roller and the transportation roller. At this time, the circumferential speed of the resist roller is slower by a predetermined degree than the circumferential speed of the transportation roller. Thus, a predetermined tensile force is constantly applied to the cut-sheet transported from the resist roller to the transportation roller to prevent the cut-sheet from being skewed during transport even when a large-size cut-sheet is used as the transfer sheet. Also, to avoid non-smooth transport of a sheet, the first slower roller, which the transport sheet contacts before contacting the faster second roller, is sped up just before the trailing edge leaves the first roller to avoid roller vibration due to immediate tension release in the sheet.