Process Control - Epson AcuLaser C4000 Service Manual

EPSON AcuLaser C4000/C4100/C3000

2.8.4 PROCESS CONTROL

In order to render a stable print, timely correction of image formation
parameters is needed. Control of the entire process that includes parameter
adjustment control is called "PROCESS CONTROL".
The following two items are the main controlling functions:
• Potential Control
• Toner Density Control
The controlling functions above are supplemented by the following functions:
• High Area Coverage Mode
• Admix Mode
• SENSOR ASSY ADC (PL6.1.11) LED Light Quantity Setting
2.8.4.1 POTENTIAL CONTROL
In order to obtain stable print image density, POTENTIAL CONTROL regulates
the drum charge voltage and the developer DC voltage to match the fluctuating
developer capability moment by moment.
Adjusted drum charge voltage and developer DC voltage is monitored, and a
fixed level of print image density is maintained.
POTENTIAL CONTROL performs its functions just before printing starts under
the following conditions:
• When printing the first page after power has been turned on
• When the number of pages lined up for printing is 16 or more
• When performing a cleaning cycle between a series of pages to be
printed
Operating Principles
An overview of POTENTIAL CONTROL is shown below.
1) Temperature and humidity is measured by the SENSOR HUM TEMP
(PL4.2.4) and target values are set for drum charge voltage and
developer DC voltage.
2) A POTENTIAL CONTROL patch for each color (yellow, magenta, cyan,
black) is formed and transferred to the BTR surface. (The shape of the
patches is shown below.)
Figure 2-34. POTENTIAL CONTROL
3) Density on the portion of the BTR surface not holding toner and density
of the patch are both measured by the SENSOR ASSY ADC (Density
Sensor).
4) Density measurements taken at Step 3) are compared with target values
set in Step 1). Adjustments to drum charge voltage and developer DC
voltage for each color are made according to the difference in the
values.
Control
Revision F
2-84