Brother DCP-7030 Service Manual page 58

(3) Development
Toner is attracted to the latent image area on the exposure drum where surface potential is
lowered due to the exposure.
By controlling developing bias voltage supplied to the develop roller, the amount of toner
taken to the drum is adjusted to keep printing density constant.
<Supply of toner to the development process>
Toner adheres to the charged develop roller. Such adhered toner is adjusted to an even
thickness, and is attracted to an exposed area on the exposured drum.
Charging
150 V
Fig. Ref. 2-22
Develop roller
Fig. Ref. 2-23
Ref. 2-23
Laser beam
450 V to 300 V
(Changes depending on use condition)
850 V
Develop roller
Blade
Exposure drum
Toner
Confidential