Canon iR6570 series, Service Manual

Page: 221 / 684

Chapter 7
7-23
7.9 Separation Mechanism
7.9.1 Separation Charging Mechanism
7.9.1.1 Outline
0009-4113
The following items are associated with the separation charging control system:
1. controlling the constant current of the DC bias
2. controlling the constant voltage of the AC bias
3. correcting the output to suit the environment and drum surface potential (fuzzy control)
The following shows the construction of the separation charging control system:
F-7-29
The following signals are associated with the separation charging control mechanisms:
[1] Separation charging leakage detection signal; if the current is too high or too low, '0'.
[2] Separation charging current control signal; used to control the DC bias current and the AC bias voltage generated by the high-voltage PCB.
[3] Separation charging remote signal; turns on/off the separation current output.
7.9.1.2 Correcting the Output to Suit the Environment and the Drum Surface Potential
0009-4115
The separation current output is optimized to suit the environment (i.e., reading of the environment sensor) and the deposit of toner (either of 3 levels; low,
average, high, as determined by the count of black pixels).
F-7-30
[1] In a low humidity environment, paper tends to become dry, thus tending to collect charges (high resistance). The output is decreased.
[2] If the drum surface potential is low, the output is increased to prevent separation faults.
[3] If the drum surface potential is high, the current level is lowered to prevent re-transfer.
SERVICE MODE:
COPIER> OPTION> BODY> FUZZY (turning off/on fuzzy control)
0: enable fuzzy control (default)
1: low humidity mode (for higher pre-transfer charging current than normal)
2: normal humidity mode
DC controller PCB
AC+DC
HVT-AC [2]
SEPARATE-LEAK-
DETECT [1]
HVT_SEPARATE [3]
High-voltage PCB
High-voltage AC transformer
Separation
charging wire
J4503
J4502 J102A
Separ
ation current(
A)
Toner deposit high
Toner deposit average
Toner deposit low
If the toner deposit is high, the current
level is lowered to prevent re-transfer.
If the toner deposit is low, the output
is increased to prevent separation faults.
In a low humidity environment, paper tends to
become dry, thus easily collecting charges
(high resistance); to remedy the fact,
the output is lowered.
Low humidity High humidity