Drum Unit; Photosensitive Drum; Primary Charger; Developer Roller - Brother HL-720 - B/W Laser Printer Service Manual

2.4

Drum Unit

2.4.1

Photosensitive Drum

Generates the latent electrostatic image and develops the image on the drum
surface.
2.4.2

Primary Charger

Forms a uniform charge on the drum surface.
(1)
(2)
2.4.3

Developer Roller

Develops the latent electrostatic image on the drum surface by the toner.
2.4.4

Transfer Roller

Transfers the toner image to the paper from the drum surface.
2.4.5

Cleaner Roller

Removes and exhausts the toner remaining on the drum surface.
2.4.6

Erase lamp

Discharges the electrostatic latent image on the drum.
2.5

Print Process

2.5.1

Charging

The drum is charged to approx. +1000V by ion which is generated by the primary
charger. Ion is generated by an ionization of the corona wire, which applied DC
bias from High-voltage Power Supply. The flow of ion is controlled by the grid to
be distributed evenly on the drum surface. The other end of the grid is generated to
approx. 280V by the voltage regulator.
Voltage
Regulator
The primary charge uses a corona wire, but since the charging terminal of the
drum is a positive terminal , only less than 1/10 of the usual quantity of ozone is
generated. The level of ozone expelled from the printer is therefore not harmful to
the human body. Applicable safety standards have been complied with.
Corona wire
Generates ion on the drum.
Grid
Spreads the ion evenly over the drum.
-
-
+
-
+
- -
+
- -
+
- - - -
+ +
+ + +
1000V +
+
+
+
+
+
+
+
+
+ + +
280V
Aluminum pipe
Organic Photoconductor layer
Grid
HVPS
Corona wire
Fig. 2.31
II-28
Passive Type
Voltage Regulator
Drum