Ricoh FW830, Service Manual

Page: 39 / 227

4.4 TONER DENSITY CONTROL
The flow chart above illustrates how the copier determines whether or not to
add toner.
This copier uses a dual sensor system to control toner density. The primary
sensor is the ID sensor (image density sensor) which is installed on the
pick-off pawl unit. This sensor is a photosensor and directly measures the
density of a test pattern on the drum. The test pattern is made by the pattern
plate interrupting the light path. This is done just before making the copy
when the main switch is turned on, and just before making the copy every
1220 mm. If the test pattern image density is too low, toner is added.
The secondary sensor is the toner sensor. It measures the ratio of toner to
carrier in the developer. This sensor is used only if the output of the ID
sensor is abnormal or the original is longer than 1200 millimeters. (For very
long originals, it is possible for the toner density to change while the copy is
being made.)
ID Sensor
Check
Toner Sensor
Check
ID sensor
normal?
Toner
sensor
Toner
density
low?
Toner supply
solenoid ON
Toner supply
solenoid ON
Original
longer than
1220 mm?
Service Call
indicator ON
Yes
No
No
Yes
No
Yes
No
Yes
Abnormal
Toner density
sensor
Low, Normal
Toner
density sensor
low?
Abnormal,
High
Low, Normal, High
density
DEVELOPMENT 31 December 1992
2-20