Ricoh B246 SERIES, Manual, Page: 185 / 268

185
185
Toner Supply
„
Factors
z
Toner density (TD) sensor
z
Image density (ID) sensor
z
Image pixel count (number of black pixels on the
page)
„
Two toner supply modes
z
Sensor control mode
• Uses all the above factors
z
Image pixel count mode
• Does not use the TD/ID sensors
Service manual, section 6.9.10
Overview
ˆ
To control toner supply, the machine monitors the following:
¾
Toner density (TD) sensor – checked every copy
¾
Image density (ID) sensor – checked just after the machine is switched on (if
the machine does process control), at the end of each job (if not been
checked for 10 pages or more), in the middle of a long job (if not been
checked for 100 pages)
¾
Image pixel count (number of black pixels in the page)
ˆ
Readings from the TD sensor keep the toner concentration in the developer
constant. However, variations in how chargeable toner is affect the image on the
drum. Therefore, the ID sensor monitors a reference pattern on the drum, and the
readings are used to change the toner concentration to keep the density of this
pattern constant. Use of the ID sensor also takes changes in drum reflectivity with
time into account.
Toner Supply Modes
ˆ
There are two toner supply modes:
¾
Sensor control mode: The machine varies toner supply for each copy, to
maintain the correct proportion of toner in the developer. This mode uses the
TD and ID sensors, and the image pixel count
¾
Image pixel count mode: This mode does not use the TD and ID sensors.
The machine switches to this mode when both the TD and ID sensors are
defective.
¾
If only one of the two sensors is defective, the following occurs:
TD sensor defective: The ID sensor is used in combination with the image
pixel count
ID sensor defective: The TD sensor controls the toner supply, but the TD
sensor reference voltage is not recalibrated.