Canon PC770 Service Manual - Page 34

MN COPYING PROCESS E. Development (step 3) Blade Developing cylinder Toner 0 Cylinder}Developing Magnet cylinder ... Blade Depositing roller 1T1 Figure 2-107 (developing assembly) As shown in Figure 2-107, the developing assembly consists of a rubber blade and a developing cylinder constructed of a fixed magnet and a cylinder that rotates around it. The copier's toner is a one-component toner (for both black and color) made mostly of magnetite and resins. The toner has insulating characteristics and becomes positively charged by the friction between the rotating cylinder and the blade. The depositing roller collects toner around the blade and serves to scrape residual toner from the developing cylinder. (See Figure 2-108.) /77 Figure 2-108 The toner is moved between the rotating developing cylinder and a blade, where it is charged to a positive potential and deposited on the developing cylinder in a thin, uniform layer. The developing cylinder receives both AC bias and DC bias (negative component) at the same time; the resulting bias is called developing bias. For this reason, the negative component of the developing bias is greater than the positive component. DC bias Positive component Negative component Figure 2-109 2 - 4 COPYRIGHT © 1994 CANON INC. CANON PC72N7401150R/0 REV.O AUG.1994 PRINTED IN JAPAN (IMPRIME AU JAPON)