Sharp FO-3150 Service Manual page 51

7-5. Image forming operation
STEP 1 (Cleaning, Charging): Residual toner the OPC drum is stirred
The main charger is a rotating brush roller.
The main charger removes residual toner from the OPC drum by its
rotating sweeping action and causes it to stick to the brush.
At the same time, a high voltage of –850V is applied to the main charger
roller to generate a discharge of electricity between the roller and the
OPC drum, generating positive and negative charges. The negative
charges are attracted to the OPC drum, and evenly distributed on the
OPC drum. (The OPC drum surface is evenly charged.)
Residual
toner
AC600V
(P-P)
DC-850V
CTL
Fig. 12
and negative charges are scattered
evenly on the OPC drum. (The OPC
drum surface is evenly charged.)
Main charger brush
OPC drum
Aluminum layer (drum base)
CGL
STEP 2 (Exposure): Laser beam scanning light corresponding to the
print data is radiated on the OPC drum.
Positive and negative charges are generated in the OPC drum CGL
exposed with the laser beam.
Positive charges generated in the CGL are attracted toward the OPC
drum surface (negative charges), and negative charges toward the
aluminum layer (positive charges).
Therefore, the positive and negative charges neutralize each other in
the laser-exposed area of the OPC drum surface and the aluminum
layer, decreasing the potential of the OPC drum surface.
The area which is not exposed to laser beam has no change, and the
OPC drum surface remains negatively charged to keep a high potential.
As a result, latent electrostatic images are formed on the OPC drum.
Non-exposed area
3 – 7
FO-3150U/C
Laser beam
Exposed area
CTL
CGL
Aluminum layer
(Drum base)
CTL
CGL
Aluminum layer
(Drum base)
Fig. 13