Image Density Control - Ricoh FT6645 Manual

PROCESS CONTROL

1.4 IMAGE DENSITY CONTROL

1.4.1 Toner Density Sensor
5
A
C B
4
Sensor
Output
3
(V)
V
REF
2
1
0
1
Toner Weight %
Developer consists of carrier particles (iron) and toner particles (resin and
carbon). Inside the development unit, developer passes through a magnetic
field created by coils inside the toner density sensor. When the toner
concentration changes, the voltage output by the sensor changes accordingly.
<Toner Density Sensor Initial Setting>
When new developer with the standard toner concentration (2.0% by weight,
20 g of toner in 1000 g of developer) is installed, developer initial setting must
be performed by using SP mode (
During this setting, the output voltage (V
circuit (AGC) on the main control board PCB varies to change the output
voltage from the toner density (TD) sensor. This is done by changing the gain
data, see below.
V = V
OUT
If the data is high, V
voltage becomes high. As a result, the sensor characteristic
becomes as illustrated by curve A. If the data is low, V
becomes low, and the sensor output voltage becomes low. As a
result, the sensor characteristic shifts as illustrated by curve C.
A: V (Gain data) is high.
OUT
B: V is within the specification.
OUT
C: V (Gain data) is
OUT
New Developer
2 3 4
Gain Data
x = 12 x
IN
256
OUT
low.
Main PCB
V
V
IN
AGC
Gain
V V
= IN x
OUT
256
Gain
= 12 x
256
SP Adjustment – PAGE 1).
1
) from the auto gain control
OUT
Gain Data
256
becomes high, and the sensor output
2-12
23 April 1993
OUT
V (12 V)
D
GND
Sensor
Output
OUT
TD
Sensor