When toner bottle [A] is pushed in, shutter [B] is pushed open by the PCU body. Pressing in lever [C] pulls
off toner bottle cap [D], which is held by chuck [E]. When clutch [F] turns the bottle, the spiral grooves push
toner out at [G], and the turning Mylar blades [H] push this toner through slit [I] into the developing unit.
Toner collection coil [J] simultaneously recycles toner retrieved from the OPC drum. The recycled toner
slides down chute [K] and enters the developing unit through slit [L].
Toner Density Control
Overview
Toner concentration in the developer is controlled using the following values:
Vts:
TD sensor initial setting (1.25V). (Used as reference voltage when Vref is not
available.)
Vref: Toner supply reference voltage (calculated value; periodically updated)
Vt: Actual output from TD sensor
Vsg/Vsp:
Values from ID sensor, where Vsp is the voltage of a test pattern (the "ID sensor
pattern"), and Vsg is the voltage of the bare drum
Toner is added to the development unit if Vt is higher than the reference voltage.
Reference Voltage
Vts is used as the reference if the PCU has just been installed (since Vref has not yet been calculated) or if
ID sensor correction has been disabled with SP2-927. In all other cases, Vref is used as the reference.
Toner Density Sensor Initial Setting
The Vts for this machine is 1.25 V. During TD sensor initialization (after installation of new PCU), the machine
adjusts the sensor so that it reads out 1.25V.
Toner Concentration Measurement
The machines checks concentration every copy cycle, by comparing Vt against the reference voltage.
Vsp/Vsg Detection
An ID sensor pattern is made on the drum by the charge roller and laser diode. The ID sensor detects the
pattern density (Vsp) and the density of the bare drum (Vsg).
Detection is carried out at the same time as (and immediately before) charge-roller voltage detection (*
"Charge Roller Voltage Correction").
• Use of ID sensor control can be disabled with SP2-927.
Calculation of Vref
6. Detailed Section Descriptions
268
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