Canon PC300 Service Manual page 24

COPYING PROCES:
Both AC bias and DC bias (negative
component) are applied to the developing
cylinder at the same time, generating devel-
oping bias; as a result, the negative compo-
nent of the developing bias is greater than
the positive component.
Positive component
Negative component
DC bias
Figure 2-9
During copying operation, the toner is
attracted to the photosensitive drum by the
surface potential of the drum and the devel-
oping bias (positive component) to turn the
latent static image to a visible image.
Excess toner is repelled by the photo-
sensitive drum by the surface potential of the
drum and the developing bias (negative
component).
The DC bias affects copy density and
fogging; a higher bias, i.e., closer to 0 V,
increases the density but, at the same time,
tends to fog the background of the copies.
2-4 COPYRIGHT © 1094 CANON INC,
Step 4 Transfer
Figure 2-10
A negative voltage is applied to the back
of copy paper to transfer toner from the pho-
tosensitive drum to the paper.
The copier uses a roller transfer method;
compared to conventional corona transfer
methods, it provides the following advan-
tages:
* Generates virtually no ozone.
« Ensures good paper transport, as the
paper is held between the roller and drum.
Note:
A jam can cause toner to stick to the
transfer roller. To clean the transfer
charging roller, the copier switches polar-
ities of the transfer voltage during copy-
ing sequence (other than transfer), there-
by returning the toner on the roller to the
drum.
CANON PC300/3207325, FC210/20 REV.0. JULY 1994 PRINTED IN JAPAN (IMPRIME AU JAPON)