Toner Density Control - Panasonic FP-7742 Service Manual

2. 2 Toner Density Control

To keep toner density(toner carrier ratio) in the developer unit constant, the TDC
sensor (toner density sensor) which is installed under the developer unit detects the
amount of carrier in the developer unit to control the toner density.
<Fundamentals>
The change of magnetic flux density in accordance with the amount of carrier
(magnetic power) of the developer (mixture of toner and carrier) is detected by the
TDC sensor and is converted to a voltage to control the toner density.
<Change of toner density and change of TDC sensor output voltage>
Amount of carrier passing TDC sensor
Less
Much
<Control>
The following controls are necessary for normal control of toner density
1) Automatic adjustment of TDC sensor gain (during execution of F8-C09)
(to attain the standard reference level).
2) Maintain the standard level by control of toner density during use.
<Explanation of the control system>
1) Automatic adjustment of TDC sensor gain
Automatically adjust the reference through the TDC sensor by executing service
mode F8-09.
The operation flow is as shown below.
CPU will check toner density sensor output. (2.5 V)
Yes
Memory number will be changed to new number in memory.
(F6-21 or F6-26)
Toner density sensor output voltage will be adjusted to 2.5 V
Toner density condition Sensor output voltage
High
Low
F8-09 start
No
CPU will adjust sensor gain
control signal
Lower than normal
Higher than normal
2-3