Chapter 4 Image Formation System; Processes; Controlling The Drum Surface Potential; Outline - Canon NP6251 Service Manual

I. PROCESSES
A. Controlling the Drum Surface Potential

1. Outline

The machine uses an electrostatographic method, and is constructed as shown in
Figure 4-101.
The quality of copy images are mostly affected by the following:
Changes in the sensitivity of the drum.
Changes in the degree of charging by the primary charging assembly.
Changes in the degree of exposure.
These changes are in turn brought about by changes in the site environment
(temperature, humidity) or deterioration of or dirt on associated parts.
The machine is equipped with a drum surface potential control mechanism to ensure
stable latent static images in the presence of these factors.
Pre-exposure
Cleaning blade
Cleaning screw
Copy paper
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Scanning lamp
Primary Optical
charging image
Light area
lamp
- - - - -
+ + + ++
-
-
+ +
-
+
-
+
Photosensitive drum
+
Cleaning roller + + +
Separation
charging wire
Transfer
charging
assembly
High-voltage transformer
DC controller PCB
Figure 4-101
CANON NP6350/NP6251 REV. 0 JULY 1997 PRINTED IN JAPAN (IMPRIME AU JAPON)

CHAPTER 4 IMAGE FORMATION SYSTEM

Lamp
regulator
PCB
Blanking exposure
Potential
measurement
- Dark
- -
PCB
area
-
Potential
+ +
-
+ +
sensor
+
- -
+ +
- -
Blade
+ +
+ + - -
Developing cylinder
+ +
+ +
+ +
+ +
Pre-transfer
charging
assembly
4-1