Canon CiRC2550, Service Manual

Page: 241 / 774

Chapter 7
7-18
consideration made to facilitate work at the factory), not being able to vary the developing bias for individual colors. To work around the fact, the machine corrects
the density of individual colors (Y, M, C). It, however, varies the developing bias for Bk as in previous machines.
3. Flow of Operation
F-7-21
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.
F-7-22
[1] Patch image data
[2] Developing DC bias
[3] Developing cylinder
Start-up
Patch pattern formation
Patch reading
UN16
DC controller
D-max correction table creation
(Y, M, C)
DC controller
Laser output determination
Laser output
Density
Y3
Y1
Y2
Y8
0
EX: D-max correction table for Y
DC controller
D-CON
[2]
UN16
ITB
Bk
[1]
HVT1
[3]