Patent ID: 7551887

Claim:
An image forming device comprising: a transportation path; a paper output path connected to the transportation path; a reversal path connected to the paper output path; an image forming unit which transfers a toner image onto printing paper transported through the transportation path; a heat roller which heats the printing paper having the toner image transferred thereon and melts the toner image; a pressure roller which presses the printing paper against the heat roller, fuses the toner image onto the printing paper together with the heat roller, and transports the printing paper from the transportation path to the paper output path; a fusing casing housing the heat roller therein, the fusing casing including an open portion; a paper output roller which is rotatable in both directions to output the printing paper transported to the paper output path to an outer side of the image forming device or to switchback-transport the printing paper to the reversal path during a duplex printing operation; a duplex transportation roller which transports the printing paper, which has been switchback-transported to the reversal path, to the transportation path again; an inner guide which defines a downstream end portion of the transportation path and the paper output path, the fusing casing arranged between the inner guide and the heat roller; a first outer guide which is arranged at a position facing the open portion of the fusing casing across the transportation path and defines the downstream end portion of the transportation path together with the inner guide; wherein the first outer guide includes a hook-shaped portion curved to guide the printing paper to the paper output path; a second outer guide which defines the paper output path together with the inner guide and defines an upstream end portion of the reversal path; and a control device which controls a linear speed of the paper output roller to be faster than a linear speed of the duplex transportation roller at the switchback transportation of the printing paper.