Canon iR C2880 Series Service Manual page 241

3. Flow of Operation
B. Black D-max Control
1. Start-Up Timing
- when the Bk drum unit is replaced with a new one
- during post-rotation executed every 1000 prints
- during execution of calibration (user mode)
2. Particulars of Control
In the presence of a specific condition, the DC controller forms a patch pattern (Notes) of Bk on the ITB.
Thereafter, the DC controller uses the patch image sensor (UN16) to measure the patch density, thereby correcting the developing DC bias of Bk so that the density
will be identical to the target density.
[1] Patch image data
[2] Developing DC bias
[3] Developing cylinder
UN16: patch image sensor
MEMO:
To reduce down-time, the machine forms only one patch on the ITB. If, however, the measured patch density is outside the range of correction, it forms an additional
EX: D-max correction table for Y
Y8
Y3
Y2
Y1
0
Laser output
[3]
HVT1
[2]
D-CON
Start-up
DC controller
Patch pattern formation
UN16
Patch reading
DC controller
D-max correction table creation
(Y, M, C)
DC controller
Laser output determination
F-7-21
ITB
UN16
[1]
F-7-22
Chapter 7
7-17