Canon FAX-L1000 - Manual (Page 197)

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FAX-L1000 Chapter 3: Technical Reference
As shown in Figure 3-23, the developing unit consists of a fixed magnet, a developing
cylinder and a rubber blade. The developing cylinder rotates around the fixed imagnet.
The single-component toner consists of magnetite and a resin binder, and is held to the
cylinder by magnetic attraction. The toner functions as an insulator, and is charged
negative by the friction with the rotating cylinder.
The areas on the drum that were exposed to the laser beam have a higher potential than the
negatively charged toner particles on the developing cylinder. When these areas approach
the toner layer of the cylinder (with negative charges), the potential difference (higher on
the drum) projects the toner particles to them.
This is called toner projection, which makes the latent image on the drum visible.
Figure 3-23 Developing Cylinder/Drum Surface Potential
An AC bias is applied to the developing cylinder to help project the toner particles to the
drum surface and improve the contrast of the printed image. The center voltage of the AC
bias (1600 Vp-p) varies with the DC bias voltage. The changes in the DC bias change the
potential difference between the cylinder and drum so that the density of the print can be
adjusted. The adjustment is made through a command from an external device.
This fax has a stirring mechanism in the cartridge to ensure that the toner is applied
smoothly to the cylinder.
d) Drum cleaning block
In the transfer block, not all the toner is transferred to the paper, but some remains on the
photosensitive drum.
In this block, the residual toner is cleaned so that the next print image will be clear and
distinct.
Voltage (V)
Developing cylinder surface potential
Drum surface potential (exposed area)
Drum surface potential (unexposed area)
+V
-V
0
Time t
DC bias