Specifications

5.4 DEVELOPMENT BIAS FOR IMAGE DENSITY CONTROL
Image density is controlled by changing two items: (1) the strength of the bias
voltage applied to the development roller sleeve, and (2) the strength of the
voltage applied to the exposure lamp.
Applying a bias voltage to the development sleeve reduces the potential
between the development roller and the drum, thereby reducing the amount
of toner transferred. As the bias voltage becomes greater, the copy image
becomes lighter. Similarly, increasing the voltage to the exposure lamp
causes an increase in light intensity which also results in lighter copies.
The method of control is different depending on whether the image density is
manually selected or the automatic ID mode is used.
The development bias applied to the development roller sleeve has the
following three factors:
Development bias voltage = Base bias voltage factor
(Manual or automatic image density control)
+
Base bias voltage adjustment factor
+
Vr correction factor
The base bias voltage for non-image areas is –200 volts (Fixed).
5.4.1 Base Bias Voltage Factor In Manual Image Density Control
Manual ID Level123456 7
Base Bias Voltage –120 –120 –160 –200 –200 –240 –280
Exposure Lamp Data Vo –4 Vo Vo Vo Vo +4 Vo+8 Vo+12
In manual ID control mode, the base bias voltage depends on the manually
selected ID level. The voltage applied at each ID level is shown in the above
table. The base exposure lamp voltage also varies depending on the manual
ID level as shown in the table. (See page 2-18 for more information.)
Darker Lighter
1 December 1990
2-29