The idea behind ID correction is to cancel the effect on the V
SP
pattern of
the decrease in the chargability of carrier with time. ID correction is done by
changing the development bias for the V
SP
pattern so that it has the same
darkness even though the chargeability of the carrier has changed.
ID Correction Method
The machine determines whether the development bias needs adjusting by
monitoring the density of the toner/carrier mixture in the development unit.
When the toner weight ratio in the developer changes, the voltage output by
the TD sensor changes accordingly. The smaller the toner weight ratio in the
developer is, the greater the TD sensor output is, as shown in the diagram
below.
When new developer with the standard concentration (2.0% by weight, 20 g
of toner in 1,000 g of developer) is installed, the TD sensor initial setting
must be done with SP mode 2-214. This sets the sensor output to 2.5
±
0.1
V.
As shown earlier, the chargeability of carrier in the developer decreases with
the copy count. If no correction is done, the CPU tries to decrease the toner
weight ratio in the developer. So this eventually causes the reading from the
TD sensor to exceed its maximum acceptable value (initial value + 1.0 V).
If the corrected TD sensor output V
TREF
exceeds the upper limit over 100
times continuously, development bias for the V
SP
pattern is corrected. V
TREF
is the current TD sensor output with a correction factor included that is based
on the V
SP
/V
SG
ratio from the ID sensor (see V
SP
and V
SG
Detection)
calculated every 10 copies or so (see Toner Supply Control - Detect Supply
Mode for more about V
TREF
).
The first time this happens, the correction is -40 V. If the upper limit is
exceeded 100 consecutive times again later, an extra -40 V correction is
applied (see the following table). There should be no need for further steps,
because the toner proportion by weight will stabilize before this.
Rev. 6/95
Detailed
Descriptions
STM 2-13 A156/A160/A162
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