Sharp SF-2220 Service Manual page 62

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.
Proccess
unit
Stirring roller
DV drive unit
MG roller
PS roller
Multi manual
insertion paper
feed unit
(Option)
Transport
roller (upper)
Transport
roller (lower)
Paper feed
Paper feed
rive unit
unit
Paper feed
unit
Thermo control
Thermistor
Heat roller
CPU
Heater lamp
(Heater trouble)
Self diag display
Thermostat
•
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.)
Reverse roller
Cur correction unit
Paper feed roller
Main motor
Main drive unit
Fuser unit
Cleaner Transport
unit unit
Paper exit
roller
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
Take-up roller
MC-Service
(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)
Standard mode
Photo mode
TSM mode
2 Main transfer corona – High voltage transformer (THVG)
–41µA (Electrode sheet front-rear balance difference: max. 7.0µA)
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.
Rear edge plate
5 – 17
Grid voltage Developing bias voltage
–750V
–500V –200V
–650V
Transport upper unit
DPHPS2
(Rear edge plate home
position sensor)