Detecting Dirt On The Window - Canon 1130 Service Manual

CHAPTER 6 IMAGE FORMATION SYSTEM
When measuring the concentration of black toner during copying operation, it is necessary to
prerent adhesion of toner on the photosensitive drum to the transfer sheet. To prevent such a
problem, the CPU PCB controls the timing at which the laser is turned on so that the black toner
image will come face-to-face with the metal transfer sheet.

4. Detecting Dirt on the Window

The 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 photosensitive
drum.
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 sensor
while 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'.
6-38
COPYRIGHT © 2002 CANON INC.
Photosensitive
drum
Transfer
drum
Figure 6-406
Photosensitive drum
Photodiode
Figure 6-407
CANON CLC1100/1130/1150/1160/1180 REV.2 FEB. 2002 PRINTED IN JAPAN (IMPRIME AU JAPON)
Laser exposure
Gradation sensor*
Black toner
Developing cylinder
Black toner concentration
sensor
Transfer sheet fixing plate
*CLC1140/1160/1180 only
Dirt on sensor
LED