| 摘要 |
<P>PROBLEM TO BE SOLVED: To provide an image forming apparatus capable of reliably detecting a jammed recording medium and to provide a jam detection method for it. <P>SOLUTION: Reference time ts which corresponds to the time required for a sheet S to pass through a detection point P of a sheet detection sensor 84 is set in advance so as to match the length of the sheet S. When time t1 elapses after the start of drive of a gate roller and then the leading end of the sheet S conveyed to a nip N between a heat roller 91 and a pressure roller 92 reaches the detection position P, the output of the sheet detection sensor 84 changes to an L-level. If the sheet conveyance is normal, the sensor output returns to an H-level after the time equal to or longer than the reference time ts elapses. On the other hand, when a jam J2 in which the sheet S is wrapped round the heat roller 91 occurs, since the leading end of the sheet S reverses, time tm becomes shorter than the reference time ts for the sensor output to be maintained at the L-level. <P>COPYRIGHT: (C)2004,JPO&NCIPI |
