Canon 1000 Service Manual page 151

4. Supplying Toner
a. Outline
Toner is supplied from the hopper based on the measurements taken of the toner density. Different
methods are used to measure the density between Bk toner and Y, M, and C toners because of different
toner characteristics. For Y, M, and C toners, the color toner density sensor is used to measure the density
of the toner in the developer layer on the developing cylinder. As in the case of carriers, the Bk toner tends to
absorb infrared light, and for this reason the density on the developing cylinder cannot be measured. The
video signals carrying a Bk component are counted to find out the image density, thereby computing toner
consumption. When copying operation ends, the SALT sensor measures the toner image on the
photosensitive drum to find out the toner density.
SALT sensor
See Figures 3-533 and -534 for sequences used to measure Y, M, and C toners and the Bk toner; the
supply operation is executed each time the measurement value falls below a specific value.
Start key ON
1st copy
2nd copy
End
Measuring the Y, M, and C Toners
Figure 3-533
COPYRIGHT © 2001 CANON INC.
DC controller PCB
Color toner density sensor
Developing cylinder
Photosensitive
drum
Detects the density of toner on the developing
cylinder (color toner density sensor)
Detects the density of toner on the developing
cylinder (color toner density sensor)
Detects the density of toner
on the drum (SALT sensor)
CANON CLC1000/1000S/3100 REV.2 MAY 2001 PRINTED IN JAPAN (IMPRIME AU JAPON)
Image density detection
Figure 3-532
Start key ON
1st copy
2nd copy
End
Measuring the Bk Toner
3. OPERATION AND TIMING
Hopper
Image density detection
Image density detection
Detects the density of toner
on the drum (SALT sensor)
Figure 3-534
3-107