Ricoh B291 - Charge Roller Voltage Correction; Correction for Environmental Conditions

DRUM CHARGE
SM 6-57 B291/B295/B296/B297
Detailed
Descriptions
6.8.2 CHARGE ROLLER VOLTAGE CORRECTION
Correction for Environmental Conditions
The voltage transferred from roller to drum could vary with the temperature and
humidity around the drum charge roller. The lower the temperature or humidity, the
higher the applied voltage required.
The ID sensor measures the effects of ambient conditions, and any small change
in drum potential caused by changes in temperature/humidity is reflected in the
amount of toner transferred to the drum.
This measurement is done immediately after the ID sensor pattern for toner density
control. After creating ID sensor pattern another pattern is made. To do this, the LD
switches off, the charge roller voltage drops, and the drum potential is reduced to -
600V. At the same time, development bias returns to -550V. The drum potential is
now slightly higher than the development bias, so only a very small amount of toner
transfers to the drum. The ID sensor measures the density of the second pattern
and Vsdp, the output voltage, is compared with Vsg which was read from the bare
drum at the same time.
ID Sensor Pattern
t
Drum Potential
Development Bias
ID Sensor Output
-850 V
-600 V
-550 V
-400 V
-150 V
V sg (4.00 V)
V sdp (3.50 V)
V sp (0.31 V)
Charge Voltage
Lase
r
Diode
3
cm
3 cm 3 cm
On
Of
f
-1500 V
Sub Scan Direction
CÓPIA NÃO CONTROLADA
CÓPIA NÃO CONTROLADA