CHAPTER 6 IMAGE FORMATION SYSTEM
6-6
COPYRIGHT © 1999 CANON INC. CANON imageRUNNER 400/330 REV.0 JAN. 1999 PRINTED IN JAPAN (IMPRIME AU JAPON)
4. Correcting the DC Bias Temperature
As the temperature inside the machine increases, the resistance of the photosensitive drum
drops to decrease charging characteristics. To ensure stable potential, the DC bias is corrected
according to changes in temperature. The temperature inside the machine is monitored by the
thermistor mounted on the rear side plate, and the absolute value of the DC bias is increased when
increases are noted in the temperature reading.
Figure 6-103
5. Correcting the AC Bias Humidity
The AC bias output characteristics change according to the humidity around the photosensitive
drum. In a low-humidity environment, the charging efficiency drops to cause uneven charging,
requiring maintenance of the current at a higher level. The AC bias is varied as shown in Figure 6-
104 according to the reading of the humidity sensor. Over time, the resistance of the drum surface
drops to allow more current; the current is decreased in such cases.
Figure 6-104
Primary DC bias
-726V
-750V
-801V
Internal temperature
Higher
Lower
(yaku
nuke)
15 C
23 C 40 C
Pr
imar
y A
C
bias
2030
˚
A
1950
˚
A
2180
˚
A
Humidity
Higher
Lower
Counter reading
@
0 to 5000 sheets
Counter reading
@
5000 sheets and more
35
Humidity
Higher
Lower
35