5.3 Process Control
For a stable printing, the parameters related to the image forming must be corrected as necessary. The
control of the entire printing process including parameter correction control is called "process control".
Mainly, the process control is performed in the following two methods, both of which are performed
after every 25 cumulative prints upon termination of a print run or during a continuous run.:
• Potential control
• Toner density control
To supplement these two controls, the following controls are provided:
• High Area Coverage Mode
• Admix Mode
5.3.1 Potential Control
To attain stable printing image density, the drum charging voltage, the developing DC voltage and the
ROS light amount are adjusted according to the developing capability of each color carrier that varies
momentarily. The adjusted drum charging voltage, the developing DC voltage and the ROS light
amount are fed back to keep the printing image density constant.
The outline of control is as follows.
1) The HUMIDITY SENSOR (temperature and humidity sensor) detects the temperature and
2) The patches of respective colors (yellow, magenta, cyan, and black) for the potential control are
generated and transferred on the Belt.
3) The ADC Sensor (density sensor) detects the density of the patch on Belt.
4) The drum charging voltage, the developing DC voltage and the ROS light amount are adjusted for
each color according to the detected patch density.
6 – 52
Chapter 6 Principles of Operation