Ricoh A085, Manual

Page: 262 / 617

1.3 V
R
PATTERN CONTROL
1.3.1 Overview
During the OPC drum’s life, drum residual voltage gradually increases due to
electrical fatigue. This may cause dirty backgrounds on copies. The V sensor
is used to avoid this problem.
The V sensor is located on the drum unit, on the same frame as the ID
sensor. The ID sensor is located on the non-operator side and the V sensor
is on the operator side.
The CPU checks the drum residual voltage through the V sensor by directly
sensing the V
R
pattern on the drum surface. This V
R
pattern detection is
performed after the drum initial setting (SP mode #66). After this, the CPU
will do one V
R
pattern detection every 200 copies for the next 2,000 copies,
and every 1,000 copies after that. Also when V
R
data correction (See 1.5
Drum Temperature Control) is applied and the drum temperature goes over
25°C, this detection is performed.
According to the data of the V
R
pattern detection, the CPU applies V
R
correction to the grid bias voltage and the development bias voltage.
Copy volume
Drum
residual
voltage
(V)
Light intensity
Drum
potential
(V)
Det
a
il
ed
Descriptions
12 February 1992 PROCESS CONTROL
2-7