Gestetner G060, Service Manual

Page: 238 / 1106

PROCESS CONTROL
G060 6-8 SM
6.2 PROCESS CONTROL
6.2.1 OVERVIEW
This machine provides the following two forms of process control:
•
Potential control
•
Toner supply control
The process control facilities of this machine have the following features:
•
Two ID (image density) sensors (front and rear). Only the front ID sensor is
used for process control. The front and rear ID sensors are used for line
positioning and other adjustments.
•
TD (toner density) sensor.
6.2.2 POTENTIAL CONTROL
Overview
Potential control controls development to maintain the density of the toner image
on the drum. It does this by compensating for variations in drum chargeability and
toner density.
The machine uses the ID sensor to measure the reflectivity of the transfer belt and
the density of a standard sensor pattern. This is done during the process control
self check.
The machine determines the following depending on the ID sensor output and a
reference table in memory.
•
V
D
: Drum potential without exposure – to adjust this, the machine adjusts the
charge roller voltage.
•
V
B
: Development bias
•
V
L
: Drum potential at the strongest exposure – to adjust this, the machine
adjusts the laser power
(In addition, V
REF
is corrected. This is used for toner supply control.)
This process controls the development potential so that the maximum amount of
toner applied to the drum is constant. However, to control the development
potential to improve reproduction of highlight parts of the image, the laser power
control method can be changed. This depends on the setting of SP3-125-2. The
default setting is 1 (normal control method). To change to the highlight range
control method, set this SP to 2.
If SP3-125-1 is set to 0 (Off), the machine does not do the potential control, but
uses the development bias adjusted with SP2-201-1 to -9, the charge roller voltage
adjusted with SP2-001-1 to -9, and the laser power selected with SP2-103-1 to -27.
However, these SPs should normally not be adjusted in the field.