Canon MF720 Series Service Manual page 47

Item
Copy image correc- Gradation of copy images is corrected
tion based on the gradation density read on out-
put test pattern by the reader.
Operational flow
Gradation is corrected either in the 3 approaches above in the following flow.
■ Toner cartridges
● Developing cylinder contact control
The control makes the developing cylinder engagement / disengagement to the photosensitive drum as required in the specified
print mode (full color or monochrome).
By controlling the developing cylinder engagement to the photosensitive drum only when needed, this control effectively prevents
the photosensitive drums from being deteriorated to maximize the service life.
The DC controller actuates the motor (MF8500: Developing motor, MF8200: Main motor) to switch the direction of the
engagement / disengagement cam to contact / separate the developing cylinder to / from the photosensitive drum.
The DC controller controls the developing cylinder (engagement / disengagement) by regulating the main motor rotation upon
detecting signals from the development home position sensor.
The state of the Developing Cylinder for each color (engagement / disengagement) differs depending on the condition of the Main
Body.
Condition of the Main
Body
Power OFF/Standby
Monochrome print
full-color print
Related Error Code
• E015-000 (Error in developing roller contact)
Failed to detect changes in developing home position sensor signals within the pre-defined time after actuating motor
(MF8500: Developing motor, MF8200: Main motor) to control the developing roller contact.
■ Transfer unit
● Pad transfer method
This product employs the pad transfer method in the primary transfer mechanism.
Description
Image gradation
correction
Copy image
Full correction
correction
Test print 1
Test print 2
Y
Disengagement
Output sheets
1 sheet
Quick correction
Scan 1
Full correction
Copy image correction
Quick correction
Scan 2
M
Disengagement
Engagement
39
2. Technical Explanation
Test pattern
Type
for for error diffusion process
C Bk
Engagement