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Functional Overview
: Image formation system
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any previous image. In addition, a negative DC bias is applied by the charging
roller to create a uniform negative potential on the drum surface. The amount
of DC voltage is modified by the print density setting.
Step 3
Writing stage. During this process, a modulated laser diode projects the beam
onto a rotating scanning mirror. As the mirror rotates, the beam reflects off the
mirror, first through a set of focusing lenses, then off a mirror, and finally
through a slot in the top of the toner cartridge, and onto the photosensitive
drum. The beam sweeps the drum from left to right, discharging the negative
potential wherever the beam strikes the surface. This creates a latent
electrostatic image, which later is developed into a visible image.
Because the beam is sweeping the entire length of the drum and the drum is
rotating, the entire surface area of the drum can be covered. At the end of
each sweep, the beam strikes the beam detect lens, generating the beam
detect signal (BD signal). The BD signal is sent to the ECU where it is
converted to an electrical signal used to synchronize the output of the next
scan line of data.
Step 4
Developing stage. At this stage of the process, the latent electrostatic image is
present on the drum. The toner particles obtain a negative surface charge by
rubbing against the developing cylinder which is connected to a negative DC
supply. The negatively charged toner is attracted to the discharged (exposed,
grounded) areas of the drum, and repelled from the negatively charged
(unexposed) areas.
Step 5
Transferring stage. During the transferring process, the toner image on the
drum surface is transferred to the paper. A positive charge applied to the back
of the paper by the transfer roller causes the negatively charged toner on the
drum surface to be attracted to the paper. After separation, the drum is
cleaned and conditioned for the next image.
During the separating process, the paper separates from the drum. To
stabilize the feed system and prevent dropouts on the printed image at low
temperature and humidity, the charge on the back of the paper is reduced by
the static charge eliminator.
Step 6
Fusing stage. During the fusing process, the toner is fused into the paper by
heat and pressure to produce a permanent image. The paper passes
between a heated fusing element and a soft pressure roller. This melts the
toner and presses it into the paper.
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