Paper Feed Section And Paper Transport Section - Sharp AR-5012 Service Manual

Top view
Thermistor
Heat roller
Separator pawl
(1) Heat roller
A Teflon roller is used for the heat roller and a silicone rubber roller is
used for the lower heat roller for better toner fusing performance and
paper separation.
(2) Separator pawl
Three separator pawls are used on the upper heat roller. The separa-
tor pawls are Teflon coated to reduce friction with the roller and prevent
a smear on the paper caused by the separator pawl.
(3) Thermal control
1) The heater lamp, thermistor, main PWB, DC power supply PWB,
and triac within the power supply unit are used to control the
temperature in the fuser unit.
To prevent against abnormally high temperature in the fuser unit, a
thermal breaker and thermal fuse are used for safety purposes.
Safety device
(thermal breaker, thermal
fuse)
Triac (in the
power supply unit)
2) The surface temperature of the upper heat roller is set to 165 -
190°C. The surface temperature during the power save mode is
set to 100°C.
3) The self-check function comes active when one of the following
malfunctions occurs, and an "H" is displayed on the multicopy
window.
a. When the heat roller surface temperature rises above 240°C.
b. When the heat roller surface temperature drops below 100°C during
the copy cycle.
c. Open thermistor
d. Open thermal fuse
e. When the heat roller temperature does not reach 190°C within 27
second after supplying the power.
(4) Fusing resistor
Fusing resistor
This model is provided with a fusing resistor in the fusing section to
improve transfer efficiency.
Since the upper heat roller is conductive, when using copy paper that
contains moisture and the distance between the transfer unit and the
fusing unit is short, the transfer current may find a path to ground via
the copy paper, the upper heat roller and the discharging brush.
Thermal fuse
Heater lamp
Heated by the heater
lamp. (950W)
The surface temperature
of the upper heat roller is
sensed by the thermistor.
Level of the thermistor is
controlled by the main PWB.
With the signal from the
main PWB, the triac is
controlled on and off.
(power supply PWB)
AR-5012 OPERATIONAL DESCRIPTIONS 7 - 4
5. Paper feed section and paper transport
section
A. Paper transport path and general operations
4 3
14
1 Scanner unit
2 Copy lamp
3 LSU (Laser unit)
4 Paper exit roller
5 Main charger
6 Heat roller
7 Pressure roller
Paper feed is made in two ways; the tray paper feed and the manual
paper feed. The tray is of universal-type, and has the capacity of 250
sheets.
The front loading system allows you to install or remove the tray from
the front cabinet.
The general descriptions on the tray paper feed and the manual paper
feed operation are given below.
(1) Cassette paper feed operation
1) The figure below shows the positions of the pick-up roller, the
paper feed clutch sleeve, and the paper feed latch in the initial
state without pressing the COPY button after lighting the ready
lamp.
The paper feed latch is in contact with the projection of the clutch
sleeve.
2) When the COPY button is pressed, the main drive motor starts
rotating to drive each drive gear.
The pick-up drive gear also is driven at that time. Since, however,
the paper feed latch is in contact with the projection of the clutch
sleeve, rotation of the drive gear is not transmitted to the pick-up
roller, which does not rotate therefore.
PFS
OFF
5 2
1
6
7
8
9
10
13 12 11
8 Drum
9 Transfer unit
10 Pickup roller
11 Manual paper feed tray
12 Manual paper feed roller
13 PS roller unit
14 Paper feed roller
RRS
OFF