Canon imagePRESS C1 Service Manual - page 373
Chapter 7
7-24
F-7-24
7.4.10 D-max Control
0014-4592
imagePRESS C1 P / imagePRESS C1
This D-max control (image density correction control) is executed to control the variation in image density caused by the change in environment, or deterioration
of the photosensitive drum or toner.
Activation Timing
- At PASCAL control
- At every paper interval
Control Description
The DC controller creates patch patterns of each color (Y, M, C, Bk) on the drum at every paper interval. Afterwards, the patch image read sensor (PS3) measures
the patch patterns to execute toner supply control according to patch density. At this point, the ATR sensor (PS7) reads the sleeve surface of the developing assembly
to measure the T/D ratio. The DC controller evaluates whether to execute toner supply by measuring result of the T/D ratio to determine the developing bias and
the grid bias for each color (Y, M, C, Bk) in order to realize optimal density.
Memo:
T-7-11
1
Vt Application
Estimate the voltage corresponding the current listed on the environmental table and then apply Vt1 to Vt3 to
the bias roller. Gauge the current at HVT6 and feed back the results to the DC controller.
2
Drawing Target It-Vt Curve
Measure the current (It) at the voltages Vt1 to Vt3, and draw an It-Vt curve.
3
Determining the Cleaning Bias
DC controller calculates a target Vt from the target It and then determines the most suitable cleaning bias based
the target Vt.
Condition
Cause
Remedy
The patch density is light, and the
sleeve surface is dark
The toner density developed to the drum is getting
lower due to developing-related reasons,
Stop toner supply, and determine the developing bias and the
grid bias in order to obtain optimal density.
The patch density is dark, and the
sleeve surface is light
The toner density developed to the drum is getting
higher due to developing-related reasons,
Execute toner supply forcibly, and determine the developing
bias and the grid bias in order to obtain optimal density.
Target It
Vt3
Vt2
Vt1
Vt
Current (It)
Voltage (Vt)