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10 May 1996
2.2 TONER DENSITY CONTROL
2.2.1 V
CORRECTION
CNT
V
T
2.5
Even if the toner concentration is constant, the toner density sensor output
gradually increases after new developer is installed because of developer
characteristics. Because of this, the machine believes that the amount of
toner in the developer has reduced. This causes the machine to increase the
toner concentration because the machine controls the toner concentration so
that V
stays constant.
T
To compensate for this, the V
gamma curve made from the 14-grade pattern during process control self
check.
The present gamma curve [A] and the previous gamma curve [B] are
compared, and the average [C] is calculated. As shown in the diagram, the
gain is decreased by 1 when the average gradient is 3.8 or more. The
maximum compensation value is –16.
Because of this new V
performed every 200 copies is no longer necessary. Also, due to the use of
the average value, over-reduction of the gain is avoided.
Copies
A172D511.wmf
Average ≥ 3.8
Average ≤ 2.3
gain is corrected by using the development
CNT
correction system, the V
CNT
2-7
PROCESS CONTROL
Pattern Density (mg/cm
Drum Potential
Gain Value = –1
Gain Value = ±0
Gain value = +1
correction previously
CNT
2
)
[A]
[C]
[B]
A172D512.wmf
A172D513.wmf
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