Ricoh FT5034 Service Manual page 13

3.1 COPY PROCESS DIAGRAM
Cleaning Blade
Cleaning
Brush
Pre-Cleaning
Corona (PCC)
1. DRUM CHARGE
In the dark the charge corona unit gives a uniform
positive charge to the selenium drum. The charge
remains on the surface of the drum because the
photoconductive selenium has high electrical resistance
in the dark.
2. ERASE
The erase lamp illuminates the areas of the charged
drum surface that will not be used for the copy image.
The resistance of the drum in the illuminated areas
drops and the charge on those areas dissipates.
3. EXPOSURE
An image of the original is reflected onto the selenium
drum surface via the optics assembly. The charge on
the drum surface is dissipated in direct proportion to the
intensity of the reflected light, thus producing an
electrical latent image on the drum surface.
4. DEVELOPMENT
Negatively charged toner is attracted to the positively
charged areas of the drum, thus developing the latent
image. (The negative triboelectric charge is caused by
rubbing action between the carrier and toner particles.)
5. ID SENSOR
The main CPU checks toner density by directly sensing
the image density at the beginning of the first copy cycle
after the main switch is turned on, and at every 10th
copy after that.
6. PRE-TRANSFER LAMP (PTL)
The PTL illuminates the drum to remove all positive
charge from the exposed areas of the drum. This
prevents the toner particles from being reattracted to
the drum surface during paper separation and makes
paper separation easier.
Quenching
Lamp
F TYPE
Photoconductor Drum
Pick-off Pawls
Charge Corona Unit
Erase Lamp
Transfer
Corona Wire
Separation
Corona Wire
7. IMAGE TRANSFER
Paper is fed to the drum surface at the proper time so
as to align the copy paper and the developed image on
the drum surface. Then, a strong positive charge is
applied to the reverse side of the copy paper, providing
the electrical force to pull the toner particles from the
drum surface to the copy paper. At the same time, the
copy paper is electrically attracted to the drum surface.
8. PAPER SEPARATION
A strong ac corona discharge is applied to the reverse
side of the copy paper, gradually reducing the positive
charge on the copy paper and breaking the electrical
attraction between the paper and the drum. Then, the
stiffness of the copy paper causes it to separate from
the drum surface. The pick-off pawls help paper which
has low stiffness to separate from the drum.
9. PRE-CLEANING CORONA (PCC)
The PCC applies a positive charge to any toner
remaining on the drum after image transfer. This
causes repulsion between the toner particles and the
drum and thereby makes cleaning more effective.
10. CLEANING
The cleaning brush removes part of the toner on the
drum and loosens the remainder. The cleaning blade
then scrapes off the loosened toner.
11. QUENCHING
The light from the quenching lamp, which is a cold
cathode tube, electrically neutralizes the surface of the
selenium drum.
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Exposure
Carrier
Toner
Development
Roller
ID Sensor
Pre-Transfer Lamp
Paper