CHAPTER 2 NEW FUNCTIONS2-111COPYRIGHT © 2001 CANON INC. 2000 2000 2000 2000 CANON iR8500/7200 REV.1 AUG. 20017.3 Photosensitive DrumThe machine’s photosensitive drum has a higher degree of charging ability than that of theGP605.7.4 Pre-Transfer Exposure LED (addition)The machine uses processing speed of 450 mm/sec (as opposed to 300 mm/sec of theGP605), to enable the generation of 85 copies per minute (iR8500: A4, Direct), in the caseof the iR7200, 72 copies per minute because of the increased distance between sheets.To make up for the reduction in the strength of charging on the photosensitive drum, themachine uses a photosensitive drum with a higher charging ability. The wave length of thelight emitted by the pre-exposure lamp is 660 nm, made shorter to eliminate residualcharges and to ensure a specific volume of charge.In addition, to make up for the possible decrease in the power of separation caused by ahigher process speed, the following pre-transfer exposure LED is used:MemoPre-Transfer ExposureFunction: At the beginning of the transfer process, the photo-sensitive drum potential (white background poten-tial) is reduced by removing charges, and the staticbond between the photosensitive drum and thetransfer medium is weakened to facilitate separation.Wave length: 700 nmTiming of activation: The LED is kept ON between a point in time 100msec before the leading edge of the image reachesthe point of light emission of the LED and a point intime when the trailing edge of the image moves pastit (See F02-701-02).
