DEVELOPMENT AND TONER SUPPLY
2-76
A229 SM
V
SP
and V
SG
detection
The ID sensor detects the following voltages.
• V
SG
: The ID sensor output when checking the drum surface
• V
SP
: The ID sensor output when checking the ID sensor pattern
In this way, the reflectivity of both the drum and the pattern on the drum are
checked.
The ID sensor pattern is made on the drum with the charge corona and laser diode.
V
SP
/V
SG
is detected every 50 copies (or at the end of a copy job of more than 50
pages) to update the TD sensor reference voltage (V
REF
). This interval can be
changed using SP2-210. This compensates for any variations in the reflectivity of
the pattern on the drum or the reflectivity of the drum surface.
V
REF
Update
V
REF
is updated using V
SP
/V
SG
and V
T.
This is done every 50 copies (or at the
end of a copy job of more than 50 pages), and during process control initial setting.
See “V
REF
Update” in the Process Control section for details.
V
T
detection
The toner density in the developer is detected once every copy cycle after the
trailing edge of the image passes the development roller.
Image pixel count
For each copy, the CPU adds up the image data value of each pixel and converts
the sum to a value between 0 and 255. (The value would be 255 if the page was
completely black.)
Gain Determination
GAIN is another factor in the toner supply clutch on time calculation. Its value can
be 0, 1, 2, 3, or 4. It is calculated every copy using “V
REF
– V
T
“.
Toner Supply Clutch On Time Calculation
The toner supply clutch on time for each copy is decided using the following
formula: (GAIN × Image pixel count × 0.7mg/cm
2
/Toner Supply Rate) + 50ms
The toner supply rate can be changed using SP2-209.
Image pixel count control
This mode should only be use as a temporary countermeasure while waiting for
replacement parts, such as a TD sensor. This mode controls the toner supply using
the same formula for the toner supply clutch on time. However, the GAIN value is
fixed at 0.7.
Rev. 12/15/98
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