CHAPTER 6 IMAGE FORMATION SYSTEM6-38 COPYRIGHT © 2002 CANON INC. CANON CLC1100/1130/1150/1160/1180 REV.2 FEB. 2002 PRINTED IN JAPAN (IMPRIME AU JAPON)When measuring the concentration of black toner during copying operation, it is necessary toprerent adhesion of toner on the photosensitive drum to the transfer sheet. To prevent such aproblem, the CPU PCB controls the timing at which the laser is turned on so that the black tonerimage will come face-to-face with the metal transfer sheet.Figure 6-4064. Detecting Dirt on the WindowThe LED is turned on when the power switch is turned on or while control rotation (CNTR)takes place during copying operation to measure PT-SIG-D without toner on the photosensitivedrum.The level of PT-SIG-D is low if the sensor window is soiled. The ratio between the level of PT-SIG-D and a predetermined value is stored in memory and used to correct the output of the sensorwhile controlling the concentration of the toner inside the black developing assembly.If the level of PT-SIG-D is ±30% or more of a predetermined level, the copier will indicate‘E020’.Figure 6-407TransferdrumPhotosensitivedrumLaser exposureBlack tonerGradation sensor**CLC1140/1160/1180 onlyDeveloping cylinderTransfer sheet fixing plateBlack toner concentrationsensorPhotosensitive drum Dirt on sensorPhotodiode LED
