Olivetti d-Color MF4003 Service Manual page 632

d-Color MF4003/MF3303
Purpose
To stabilize image transfer
• *: Refer to descriptions concerning control of each section.
Toner supply motor
PH temperature
sensor
Color shift
correction
TCR sensor
Toner supply control
OUT/IN
· To be set on operation panel
D MAX density
Background voltage margin
Toner supply
1.16.2 Description of control
(1) IDC sensor adjustment control
• Controls changes in characteristics due to change with time and contamination of the transfer belt and IDC sensor, part-to-part variations
in the sensors, and change of environment.
• The intensity (current value) of the IDC sensor is adjusted on the surface of the transfer belt, on which no toner sticks (background level).
(2) Dmax density adjustment control
• The developing bias (Vdc) is adjusted to control changes in the solid density resulting from variations in developing characteristics and
IDC sensor intensity, variations in sensitivity of the photoconductor, and changes in the environment, durability, and the amount of
charge in toner.
• Patterns are produced on the surface of the transfer belt and the IDC sensor detects the amount of toner sticking to them.
• Referring to the detected data and the environment data taken by the temperature/ humidity sensors, the developing bias value that
results in the appropriate maximum density is calculated and stored in memory.
• Thereafter, the grid voltage (Vg) value, including the background margin adjustment value, is calculated and stored in memory.
(3) LD intensity adjustment control
• It adjusts the variation in reproducibility of the thin line and the reverse outline, which is resulting from the variations in electrostatic
characteristics of the photoconductor, developing characteristics and transfer characteristics in terms of individual difference,
environment and durability, to make it the target level.
• It produces detection patterns on the surface of the transfer belt with the given level of LD intensity and detects the output value of IDC
sensor.
• LD intensity is calculated from the detected IDC sensor data.
(4) Color registration control (color shift correction)
• In a tandem engine, each four different color has an independent image reproduction process. Color shift may occur due to accuracy
differences of parts in the print head unit. The color registration control system automatically detects color shift and correct color shift in
the main and sub scanning directions.
• Color shift is misalignment of the images of three different colors, yellow (Y), magenta (M), and cyan (C), with respect to the image of
black (K).
• The color shift is detected as follows. The IDC sensors read the pattern that is produced at each of front and rear ends of the transfer
belt. It calculates and stores color shift amounts in the sub scanning and main scanning directions.
• The amount of color shift in the sub scanning direction is read from the pattern falling within the sub scanning detection range.
• From data readings, the machine calculates how much the position of each of the different colors should be corrected. Based on the
calculated data, the machine controls each dot during image output, thereby correcting the color shift amount.
(5) Gamma correction control
• The intensity of LD in all gradation levels is adjusted to correct changes in gradation characteristics to a linear one. The changes in
gradation characteristics are caused by variations in the photoconductor sensitivity and developing characteristics and changes with time
and in environment.
• It produces gradation patterns on the transfer belt and calculates gradation characteristics output by the current engine with the IDC
sensor.
Service Manual
• Transfer output control *
• 2nd transfer ATVC
PC PC PC
drum drum drum
Y M C
Developing bias Vdc Grid voltage Vg
Image density
Gradation control
Gamma correction data
Gradation correction table
Temperature/
humidity sensor
P THEORY OF OPERATION > 1. d-Color MF4003/MF3303
Control
2nd transfer roller
PC
drum
K
IDC sensor
Transfer ATVC control
IN
OUT
P-58
Control means
Temperature/humidity sensor
Y119930-3