| 摘要 |
PROBLEM TO BE SOLVED: To suppress occurrence of incorrect detection by optical sensors (69, 70, 71) due to adhesion of stain to the mirror-finished roller peripheral surface of a separation roller 153. SOLUTION: A belt device is composed of: an endless paper conveyance belt 151 comprising a light-transmissive material; a plurality of stretching rollers for stretching the belt in an endlessly movable state; the first optical sensor 69; and the second optical sensor 70 and the third optical sensor 71 in which light emitted from a light emitting element is received by a light receiving element and a signal corresponding to the amount of light received is output. A roller having the mirror-finished roller peripheral surface is used as the separation roller 153 which is one of the plurality of stretching rollers, the respective optical sensors are arranged so that light emitted from the light emitting element toward the paper conveyance belt 151 is passed through the belt, reflected by the surface of the separation roller 153, passed again through the belt, and received by the light receiving element, and a cleaning device 166 for cleaning the rotating surface of the separation roller 153 is disposed. COPYRIGHT: (C)2008,JPO&INPIT
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