| 摘要 |
<P>PROBLEM TO BE SOLVED: To provide an image forming apparatus capable of determining abnormality of a disjunctive mechanism before the disjunctive mechanism fails. <P>SOLUTION: This image forming apparatus includes a shutter 41 moving to a closing position for shielding a detection surface of an optical sensor 51 for detecting a resist mark on an intermediate transfer belt 61 and to an opening position for exposing the detection surface, and the disjunctive mechanism 140 for disjunctively operating a secondary transfer unit 31 so as to separate and butt a transfer roller 10 on the intermediate transfer belt 61. An eccentric cam 37 of the disjunctive mechanism 140 is butted on both the shutter 41 and the secondary transfer unit 31 so as to open and close the shutter 41 in interlock with the disjunctive operation of the secondary transfer unit 31. Malfunction of the disjunctive mechanism 140 is determined based on opening/closing duration t3 required from the opening position of the shutter 41, through the closing position, to the opening position again, and an allowed time (t4+Δt) obtained by adding a predetermined value Δt to a predetermined reference opening/closing duration t4 required from the opening position of the shutter 41, through the closing position, to the opening position again. <P>COPYRIGHT: (C)2010,JPO&INPIT |
