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 independently.
The toner in the toner cartridge is agitated by the built-in Agitator and fed into the developer. The
Auger is driven by the toner motor.The amount of toner to be consumed according to the print
count is calculated and that amount is fed into the developer. This is called "toner dispensation",
which is controlled by two types of control, "PCDC" and "ADC".
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 attracted
to one another 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.
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 the High Voltage Power Supply
(HVPS). DB voltage is negative DC voltage combined with AC voltage. The magnet roll is kept at
a constant negative voltage against the photoreceptor layer of the drum by DC voltage. Therefore,
at the area surface where the negative electric charge on the drum 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 stimulating the toner to fly to the drum.
Thus, the toner charged negatively is attracted only to the drum surface area where the negative
charge has decreased below that of the magnet roll (electrostatic latent image) and the toner
image is formed on the drum.
Once the toner is adhered on the drum, the negative charge of the toner-bearing portion increases,
which decreases the potential and the toner-attracting force of that portion.
6 – 6
Chapter 6 Principles of Operation
(Refer to 5.3.2 Toner Density