Controlling The Developing Bias/Roller Electrode; Outline; Control Timing - Canon NP6251 Service Manual

CHAPTER 4 IMAGE FORMATION SYSTEM
C. Controlling the Developing Bias/Roller Electrode

1. Outline

During copying, both AC bias and DC bias are applied to the developing cylinder.
The DC bias is a voltage which is the sum of 100 V and V
sensor before copying is started.
When the machine is not making copies, the degree of the DC bias is varied to suit
the surface potential of the drum to prevent adhesion of excess toner on the
photosensitive drum.

2. Control Timing

Bias Voltage
DC +600V
component
+600V
V +100 [V]
L2
AC component 1500 Vp-p,
2700 Hz
4-32
COPYRIGHT © 1997 CANON INC.
Photosensitive
drum



 
Toner
Dark area
 
Light area
Bias
V = V + 100 [V]
DB L2
Figure 4-204
Period
CNTR1, 2
INTR, AER, LSTR
during copying
SCFW, SCRV
during copying
Table 4-201
CANON NP6350/NP6251 REV. 0 JULY 1997 PRINTED IN JAPAN (IMPRIME AU JAPON)
measured by the potential
L2
Developing cylinder
V
DB
Description
To prevent adhesion of excess toner on the
drum. (The surface potential varies
constantly, and is measured by the
potential sensor at all times.)
To prevent adhesion of excess toner on the
drum.
To prevent fogging of the background.
To execute toner projection.