IMAGE FORMING APPARATUS AND DETECTING METHOD FOR PRESSURE-CONTACT/SEPARATION STATE OF TRANSFER MEMBER

摘要

PROBLEM TO BE SOLVED: To detect the pressure-contact/separation state of a transfer member at a low cost without using a photointerrupter. SOLUTION: The image forming apparatus has: a secondary transfer roller 28 which is pressed against an intermediate transfer belt 23 to make the intermediate transfer belt 23 perform transfer and can move between pressure-contact state and separation state of the intermediate transfer belt; a contact/separation driving device SK which drives the secondary transfer roller 28 to move between the pressure contact state and the separation state; an optical sensor 33 which is provided to detect the state of a toner image on the intermediate transfer belt 23 as variation in light reflectivity; and a shutter member 56 which opens and closes an opening part for detection by the sensor 33 and performs the opening/closing operation in synchronism with the moving operation of the secondary transfer roller 28 between the pressure-contact state and the separation state. The image forming apparatus is configured to detect the pressure-contact state or the separation state of the secondary transfer roller 28 on the basis of variation of a detection signal S1 of the sensor 33 accompanying the opening/closing operation of the shutter member 56. COPYRIGHT: (C)2008,JPO&INPIT