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MX-B201/B201D  COPY PROCESS  6 - 2

This printer is a non-impact printer that uses a semiconductor
laser and electrostatic print process. This printer uses an OPC
(Organic Photo Conductor) for its photoconductive material.

First, voltage from the main corona unit charges the drum surface
and a latent image is formed on the drum surface using a laser
beam. This latent image forms a visible image on the drum surface
when toner is applied. The toner image is then transferred onto the
print paper by the transfer corona and fused on the print paper in
the fusing section with a combination of heat and pressure.

Step-1: Charge

Step-2: Exposure

* Latent image is formed on the drum.

Step-3: Developing

Latent image formed on the drum is then changed into
visible image with toner.

Step-4: Transfer

The visible image (toner image) on the drum is transferred
onto the print paper.

Step-5: Cleaning

Residual toner on the drum surface is removed and col-
lected by the cleaning blade.

Step-6: Optical discharge

Residual charge on the drum surface is removed, by
semiconductor laser beam.

A uniform negative charge is applied over the OPC drum surface
by the main charging unit. Stable potential is maintained by means
of the Scorotron charger.

Positive charges are generated in the aluminum layer.

A Laser beam is generated from the semiconductor laser and con-
trolled by the print pattern signal. The laser writes onto the OPC
drum surface through the polygon mirrors and lens. The resis-
tance of the OPC layer decreases for an area exposed by the laser
beam (corresponding to the print pattern signal). The beam neu-
tralizes the negative charge. An electrostatic latent image is
formed on the drum surface.

About

DC5.5KV

(   580V/   400V)

OPC layer

Pigment
layer

Aluminum
drum

OPC layer

Pigment
layer

Aluminum
layer

Drum surface charge
after the exposure

Non-image area

Image area

Semiconductor laser

Exposure
(semiconductor laser)

MX-B201/B201D  COPY PROCESS  6 - 3

A bias potential is applied to the MG roller in the two component
magnetic brush developing method, and the toner is charged nega-
tive through friction with the carrier.

Non-image area of the drum surface charged with negative poten-
tial repel the toner, whereas the laser exposed portions where no
negative charges exist, attract the toner. As a result, a visible
image appears on the drum surface.

Toner is attracted over the shadowed area because of the develop-
ing bias.

The visible image on the drum surface is transferred onto the print
paper by applying a positive charge from the transfer corona to the
backside of the print paper.

Since the print paper is charged positively by the transfer corona, it
is discharged by the separation corona. The separation corona is
connected to ground.

Toner remaining on the drum is removed and collected by the
cleaning blade. It is transported to the waste toner collecting sec-
tion in the cleaning unit by the waste toner transport roller.

S

N

N

:Carrier (Magnetized particle)
:Toner (Charge negative by friction)
(N) (S) Permanent magnet

(provided in three locations)

MG roller

 

DC

400V   8V

About DC 5.2kV

MX-B201/B201D  COPY PROCESS  6 - 4

Before the drum rotation is stopped, the semiconductor laser is
radiated onto the drum to reduce the electrical resistance in the
OPC layer and eliminate residual charge, providing a uniform state
to the drum surface for the next page to be printed.

When the electrical resistance is reduced, positive charges on the
aluminum layer are moved and neutralized with negative charges
on the OPC layer.

The Scorotron charger functions to maintain uniform surface
potential on the drum at all times, It controls the surface potential
regardless of the charge characteristics of the photoconductor.

A screen grid is placed between the saw tooth and the photocon-
ductor. A stable voltage is added to the screen grid to maintain the
corona current on the photoconductor.

As the photoconductor is charged by the saw tooth from the main
corona unit, the surface potential increases. This increases the
current flowing through the screen grid. When the photoconductor
potential nears the grid potential, the current turns to flow to the
grid so that the photoconductor potential can be maintained at a
stable level.

The print pattern signal is converted into an invisible image by the
semiconductor laser using negative to positive (reversible) devel-
oping method. Therefore, if the developing bias is added before
the drum is charged, toner is attracted onto the drum. If the devel-
oping bias is not added when the drum is charged, the carrier is
attracted to the drum because of the strong electrostatic force of
the drum.

To avoid this, the process is controlled by adjusting the drum
potential and the grid potential of the Scorotron charger.

Voltage added to the screen grid can be selected, high and low. To
make it easily understood, the figure below shows voltage transi-
tion at the developer unit.

1) Because the grid potential is at a low level, the drum potential

is at about -400V. (Carrier may not be attracted though the car-
rier is pulled towards the drum by the electrostatic force of -
400V.

2) Developing bias (-400V) is applied when the photoconductor

potential is switched from LOW to HIGH.

3) Once developing bias (-400V) is applied and the photo conduc-

tor potential rises to HIGH, toner will not be attracted to the
drum.

The reverse sequence takes place.

Retaining developing bias at an abnormal occurrence

The developing bias will be lost if the power supply was removed
during print process. In this event, the drum potential slightly
abates and the carrier makes deposits on the drum because of
strong static power. To prevent this, the machine incorporates a
function to retain the developing bias for a certain period and
decrease the voltage gradually against possible power loss.

Normally, the developing bias voltage is retained for a certain time
before the drum comes to a complete stop if the machine should
stop before completing the normal print cycle. The developing bias
can be added before resuming the operation after an abnormal
interruption. Therefore, carrier will not make a deposit on the drum
surface.

Semiconductor laser

0

START

STOP

Print potential

Toner attract
potential

2)

3)

1)

Low

4)

High

Drum potential

Developing bias

Time

MX-B201/B201D  OPERATIONAL DESCRIPTIONS  7 - 1

The outline of operation is described referring to the basic configuration.

1) Set copy conditions such as the copy quantity and the copy

density with the operation section, and press the Start key. The
information on copy conditions is sent to the MCU.

2) When the Start key is pressed, the scanner section starts scan-

ning of images. 
The light from the copy lamp is reflected by the document and
passed through the lens to the CCD.

3) The image is converted into electrical signals by the CCD circuit

and passed to the MCU.

4) The document image signal sent from the CCD circuit is pro-

cessed under the revised conditions and sent to the LSU (laser
unit) as print data.

5) The LSU emits laser beams according to the print data.

(Electrical signals are converted into photo signals.)

6) The laser beams are radiated through the polygon mirror and

various lenses to the OPC drum.

7) Electrostatic latent images are formed on the OPC drum

according to the laser beams, and the latent images are devel-
oped to be visible images (toner images).

8) Meanwhile the paper is fed to the image transfer section in syn-

chronization with the image lead edge.

9) After the transfer of toner images onto the paper, the toner

images are fused to the paper by the fusing section. The copied
paper is discharged onto the exit tray.

The print data sent from the PC are passed through the network or
USB connector and the MCU to the LSU. The procedures after that
are the same as above 5) and later.

The scan data are passed through the MCU to the PC according
to the conditions requested by the operations with the operation
panel.

Note1: 
The USB port for the MCU can not be used when the option, Net-
work Board, is installed on the machine.

Operation

section

Scanner section

CCD 

MCU (Main control/image process section)

Laser beam

Paper exit

Fusing section

Paper transport section

Manual paper

feed section

Cassette paper

feed section

Printer section

LSU (Laser unit)
Laser diode, Polygon mirror lens

Process section

USB

USB (Note1)

PC

Network
Board

Network

(Option)