5
Drive system division
The fuser unit is rotated by the main drive unit. In case of manual
rotation of the fuser unit to remove paper jam, however, excessive
loads may be applied to the gears. To prevent against this, the
pressure of the upper/lower heat rollers is reduced when the ma-
chine clamshells are opened. In addition, the fusing gear is so
constructed that the drive is not transferred to the drive system.
•
Abnormally high temperature (H3) 240˚C or upper
•
Abnormally low temperature (H4)
•
Thermistor disconnection (H2)
*
When the thermostat contact is open, it is required to press the
reset button in the upper side of the thermostat. (The contact is not
reset automatically.)
(7) High voltage section
1) General
There are three kinds of coronas; the main corona, the transfer co-
rona, and the separation corona. The main corona employs the
scorotron system, where the drum surface is evenly charged with
negative charges controlled by the screen grid between the corona
and the drum. The transfer corona is used to transfer toner images on
the drum to the copy paper. A high, negative voltage is applied to the
rear side of the paper. The separation corona applies AC corona to
the copy paper to eliminate potential difference with the drum to allow
separation of the paper.
The output voltage of the main charger and the transfer charger is
supplied by transformer 1. The feedback current from the transfer
charger is controlled to be constant and outputted to the main char-
ger.
2) Basic composition
1
Main (charging) corona – High voltage transformer (MHVG)
Grid voltage
Developing bias voltage
Standard mode
–750V
Photo mode
–500V
–200V
TSM mode
–650V
2
Main transfer corona – High voltage transformer (THVG)
–41
µ
A (Electrode sheet front-rear balance difference: max. 7.0
µ
A)
3
Separation corona – High voltage transformer (SHVG)
AC4KV
±
0.1KV
(8) ADU unit (SF-2120 only)
1) Basic operation
The ADU unit is stored above the paper cassette in the lower side of
the copier. In the duplex copy mode, the copy paper is passed from
the fusing unit through the reverse roller to the ADU, where it is
aligned by the alignment plate. Then it is pressed onto the take-up
roller by the paper holding plate, and only one sheet is transported by
the paper feed and reverse roller. It is transported from through the
transport roller to the copier, where duplex copy is made.
Stirring roller
MG roller
Proccess
unit
DV drive unit
Main drive unit
Main motor
Fuser unit
PS roller
Multi manual
insertion paper
feed unit
(Option)
Cleaner
unit
Paper exit
roller
Paper feed
rive unit
Paper feed
unit
Paper feed
unit
Transport
unit
Transport
roller (upper)
Transport
roller (lower)
CPU
Thermistor
Thermostat
Heat roller
Heater lamp
Heat roller surface
temperature detection
The heat roller is heated by the
heater lamp.
(When the heat roller surface
temperature is 190 C˚ or lower,
the heater lamp is actuated)
Contact open (*)
Abnormal high
temperature
(Heater trouble)
Self diag display
Thermo control
Reverse roller
Cur correction unit
Transport upper unit
Paper feed roller
Take-up roller
Rear edge plate
DPHPS2
(Rear edge plate home
position sensor)
5 – 17
MC-Service
