Developing; Transfer - Brother HL-720 - B/W Laser Printer Service Manual

2.5.3

Developing

Developing causes the toner to be attracted to the electrostatic image on the drum
so as to transform it into a visible image.
The Developer Consists of the non-magnetic toner. The developer roller made of
conductive rubber and the supply roller made of conductive sponge rotate on each
other. The toner is charged and carried from the supply roller to the developer
roller. Thus, the toner is adhered to the developer roller and conveyed to the drum
with its thickness made even by the blade. The toner is nipped between the
developer roller and the drum and developed on the latent image.
Electrostatic field between the drum and the developer roller, which is
DC-biased from the High-voltage power supply, makes electrostatic
potential to attract toner particles from the devel oper roller to the drum.
Toner
Auger
Develop housing
Supply roller
2.5.4

Transfer

(a) Transfer process
After the drum has been charged and exposed , and has received a
developed image, the toner formed image is transferred onto the paper,
applying the negative charge from the backside of the paper. The negative
charge to the paper causes the positive charged toner to leave the drum, and
adhere to the paper. As a result, the image is visible on the paper.
(b) Cleaning process of transfer roller
If the toner is not transferred onto the paper perfectly due to jamming
etc., it is possible that the toner adheres to the charge transfer roller. The
transfer voltage charges to positive voltage during non transferring process. Therefore
the transfer roller is cleaned by returning the positive charged toner adhered
on the transfer roller onto the photo-conductive drum.
Transfer roller
Blade
Drum
Developer roller
DC-bias
Fig. 2.34
II-30
(a) Transfer process [ON]
(b) Cleaning process [ON]
Erase lamp
Cleaner roller