Charge Roller Voltage Correction - Ricoh G035 Service Manual

2.4.2 CHARGE ROLLER VOLTAGE CORRECTION

Correction for Environmental Conditions
ID Sensor Pattern
Charge Voltage
Laser Diode
Drum Potential
Development Bias
ID Sensor Output
In the drum charge roller system, the voltage transferred from roller to drum varies
with the temperature and humidity around the drum charge roller. The lower the
temperature or humidity is, the higher the applied voltage required.
To compensate, the machine uses the ID sensor to measure the effects of current
environmental conditions. For this measurement, the process control parameters
are balanced so that any small change in drum potential caused by environmental
effects is reflected in a change in the amount of toner transferred to the drum.
This measurement is made immediately after the ID sensor pattern for toner
density control is made. Immediately after making the ID sensor pattern [A], the
charge roller voltage drops reducing the drum potential to –600 V. At the same
time, the development bias returns to –550 V. 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 this pattern [B], and the output
voltage is known as Vsdp. This voltage is comparable to Vsg (read from the bare
drum at the same time).
SM
3 cm 3 cm
3
cm
[A]
On
Off
2-19
DRUM CHARGE
[B]
Sub Scan Direction
–1,650 V
–950 V
–600 V
–550 V
–380 V
–150 V
V sg (4.00 V)
V sdp (3.50 V)
V sp (0.31 V)
t
G035D506.WMF
G035