Ricoh SP 8400DN Field Service Manual page 1395

transports the toner in the bottle horizontally. Transporting by a coil provides a stable and accurate toner supply
and low toner remaining.
Toner transported by the coil [A] falls directly into the development unit from the sub-hopper via the transport
pipe [B]. To prevent toner from remaining, a coil is provided in the transport pipe.
When the PCDU is put in the machine, the sub-hopper [C] slides the shutter [D] on the bottle assembly and the
toner goes to the entrance [E] of the development unit.
Toner Density Control
There is only one toner density control mode, called PID mode.
Mode Toner supply
decision
PID Compares Vt
with Vtref
Toner End Detection
The TD sensor detects toner near end.
If the difference between the TD sensor output and the target value is equal to or larger than the near end
threshold, the machine detects that a "possible" toner near end exists. As the machine continues to operate, it starts
to calculate an integrated value. If the integrated value is equal to or larger than the near end total threshold, the
machine determines that a "true" toner near end exists. The toner near end indicator blinks on the operation panel
at this time.
TD Sensor Reference Value
ID sensor control corrects
the TD sensor reference
value.
Toner Supply Amount
The toner supply amount Is
calculated with the difference
between Vt and Vtref.
7.Detailed Descriptions
Toner End
Detection
Available
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