Ricoh A085, Руководство пользователя, Страница: 270 / 617

1.6 DRUM ROTATION CONTROL
1.6.1 Overview
During the OPC drum’s life the photo conductive layer gets worn and this
causes a drop in drum sensitivity and a decrement in the drum potential after
the drum charge.
The CPU keeps track of the drum rotation time (main motor on time) that
corresponds to the wear of the drum surface. The grid bias voltage is
increased at set intervals (V
G
correction).
1.6.2 V
G
Correction
If drum potential decreases after the drum charge, the ID sensor pattern on
the drum becomes lighter, causing higher toner concentration in the
developer. Also, copy image density becomes slightly lighter.
To control toner density properly and to keep copy image density, drum
potential is maintained by increments of the grid bias voltage at set intervals.
(See graph above)
Drum rotation time
(V)
(H)
Drum
potential
37 63 88~(H)
–450
–550
–600
0 1 2
–500
–520
–540
–560
–580
–500
(V)
Drum rotation time
Grid bias
voltage
V
G
Correction for Sensor
Pattern
37 63 88~(H)
–700
–800
–850
0 1 2
–745
–765
–785
–805
–825
–750
(V)
Drum rotation time
Grid bias
voltage
V
G
Correction for Image
Det
a
il
ed
Descriptions
12 February 1992 PROCESS CONTROL
2-15