In the development process, toner is electrically attached to the invisible electrostatic latent image on
the drum surface to form visible toner image on the drum.
This process is performed in parallel for yellow, magenta, cyan and black color respectively.
The toner in the toner cartridge is agitated by the Agitator in the toner cartridge and fed into the
TONER DISPENSER ASSEMBLY. Further, the toner is fed to the developer by the Auger in the
TONER DISPENSER ASSEMBLY and the Auger in the tube that connects the TONER
DISPENSER ASSEMBLY and the developer. The Agitator and Auger are spiral agitating
components and they are driven by the toner motor provided on the rear of toner cartridge. The
toner to be consumed according to the print count is calculated and fed into the developer. This is
called "toner dispensation", which is controlled by two types of control, "PCDC" and "ADC". For the
PCDC and ADC, refer to "5.4 Process Control" in this chapter.
The toner fed into the developer and the carrier in the developer are agitated by the Auger, and
supplied to the Magnet Roll arranged in the vicinity of the drum surface. The toner and carrier are
charged by friction due to the agitation (toner in negative, carrier in positive), and they are
absorbed each other electrically. As the carrier is a magnetic substance, it is attracted to the
Magnet Roll having a magnetic force and a homogeneous layer is formed by the Trimmer Rod and
The magnet roll is covered by a thin semi-conductive sleeve over the surface. DB (Developing
Bias) voltage is supplied to this semiconductor sleeve from HIGH VOLTAGE POWER SUPPLY
(HVPS). DB voltage is negative DC voltage combined with AC voltage. The magnet roll is kept at
constant negative voltage against the optical conducting layer of the drum by DC voltage.
Therefore, at the area on the drum surface where the negative electric charge does not decrease,
potential is lower than the magnet roll, while the potential is higher than the magnet roll at the area
where the negative charge on the drum surface decreases. The AC voltage shakes the developer
on the magnet roll surface pressing the toner to fly to the drum.
Thus, the toner charged negatively is attracted only by the area where the minus charge has
decreased on the drum surface from the magnet roll (electrostatic latent image) and the toner
image is formed on the drum.
When the toner is attached, minus charge at that portion increases, potential decreases, and force
to attract the toner decreases.
6 – 6
Chapter 6 Principles of Operation