Ricoh G035 Service Manual page 81

Rev. 12/99
Sensor Control Mode
In sensor control mode, the machine varies the toner supply for each print, to
maintain the correct proportion of toner in the developer and to account for
changes in drum reflectivity over time. The adjustment depends on two factors:
• The amount of toner required to print the page (based on a black pixel amount
for the page)
• Readings from the TD sensor and ID sensor
Each step of the previous flow chart is explained in more detail on the following
pages.
Toner Density Sensor Initial Setting
When new developer with standard toner concentration is installed (12.5 g of toner
⇒
in 500 g of developer; 2.5% by weight), use SP2-10 to do the initial setting for the
TD sensor. This sets the sensor output to 4.0 V. this value is used as the toner
supply reference voltage (V
Image Pixel Count
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 or 0 if it were completely white.
Vt(10) Detection
The toner density in the developer is detected once every print cycle. The sensor
output voltage V
readings.
Toner Density Measurement
The machine compares Vt (10) and Vtref. If Vt (10) is greater than Vtref, the toner
concentration in the development unit is low and more toner should be added.
When Vt (10) > Vtref has been detected 20 times (toner concentration is
consistently low), 0.1 is added to Vref, and the conditions are checked again. The
result decides the value of "K" (toner supply rate coefficient), which is one of the
factors in the toner supply motor on time calculation.
If Vt (10) > Vtref has not been detected 20 times, 0.2 is subtracted from Vtref, and
"K" is decided in a similar way as for the previous condition.
GAIN Determination
GAIN is another factor in the toner supply motor on time calculation. It is decided
using the following data.
• Vtref – Vt(10)
• Ten most recent Vt values
SM
) for the TD sensor.
tref
(10) is the average of the 10 most recent sensor output voltage
t
2-29
DEVELOPMENT
G035