Drum Unit; Photosensitive Drum; Primary Charger; Transfer Roller - Brother HL-820 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) Corona wire
Generates the ion charge on the drum.
(2) Grid
Spreads the ion charge evenly over the drum surface.
2.4.3 Development Roller
Develops the latent electrostatic image on the drum surface by the addition of 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 recycles 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. +1150V by an ion charge which is generated by the
primary charger. The charge is generated by ionization of the corona wire, which has a
DC bias from the high-voltage power supply applied to it. The flow of the ion charge is
controlled by the grid to ensure it is distributed evenly on the drum surface. The drum
sleeve is regulated to approx. 280V by the voltage regulator.
Voltage
Regulator
The primary charge uses a corona wire, but since the drum is positively charged, only
less than 1/10 of the usual quantity of ozone is generated compared with the negatively
charged drum. The level of ozone expelled from the printer is therefore not harmful to the
human body. Applicable safety standards have been complied with.
-
+ -
-
+
- -
+
- -
+
- - - -
+ +
+ + +
1150V +
+
+
+
+
+
+
+
+
+ + +
Corona wire
Fig. 2-37
II-30
280V
Aluminum drum sleeve
Organic Photoconductor layer
Grid
HVPS
Passive Type
Voltage Regulator
Drum