User Guide

CHAPTER 2
2 - 42
As can be learned from the diagram, the developing assembly consists of a fixed magnet, a devel-
oping cylinder that rotates around the magnet, and a rubber blade.
The developer is called toner, and the Printer uses a 1-component type; it is composed of mag-
netite and resins, and is retained on the cylinder by a magnetic force. The toner has insulating
characteristics, and is charged to a negative potential by friction against the rotation cylinder.
The area of the photosensitive drum exposed by the laser beam has a potential higher than that
of the toner negatively charged on the cylinder. When the area comes closer to the toner layer
(possessing a negative potential) on the cylinder, the difference in potential between the surface of
the photosensitive drum and the cylinder will cause the toner to jump to and stick to the surface
of the photosensitive drum. This is referred to as ‘toner projection,’ and is used to turn the latent
static image on the surface of the photosensitive drum into a visible image.
Voltage (V)
Surface potential
of developing cylinder
Surface potential
of drum (light-area)
Surface potential
of drum (dark area)
+V
-V
0
Time
t
DC bias
Figure 2-4-9
To facilitate the projection of toner to the photosensitive drum and also to enhance the contrast in
output images, an AC bias is applied to the developing cylinder.
The median voltage of the AC bias (1600 Vp-p) varies in relation to the voltage of the DC bias.
Varying the DC bias, the difference in potential between the cylinder and the photosensitive drum
is adjsuted to control the density of printed images (as in response to commands from an external
device).
The Printer is also equipped with a stirring mechanism to ensure smooth supply of toner from
the toner case to the cylinder.