Panasonic FP-7742 / FP-7750 (serv.man2) Service Manual ▷ View online
2-8
2. 5 Re-try Control for Paper Misfeed
• Copy paper should pass the paper feed sensor within a specific time after the
paper feed clutch turns on. To reduce paper misfeeds due to a slipping paper
feed roller, the paper feed clutch turns on again (re-try operation).
• When the paper does not reach the paper feed sensor within a specific time after
two re-try operations, "jam" is indicated.
The re-try control for misfeeds is executed for each paper feed unit.
Motor off
Re-try
925ms.
@
500ms.
2038ms.
ON
OFF
OFF
ON
OFF
OFF
H
L
L
Paper feed motor
Paper feed clutch
Paper feed sensor
Sub Assemblies
3-1
Section III
Sub Assemblies
3.1 Main Drive
The driving mechanism of this machine is as follows.
Name of motor
Driving method
Driving unit
Main motor
DC24V driving
• Rotation of photo receptor drum
• Developer unit, paper feed unit, paper transport, fuser unit and paper
exit unit
Optics motor
Pulse driving
Optics system scanning and return
Paper feed unit (Lower stage)
Middle roller
Paper
feed unit
feed unit
Middle roller
Registration roller
Bypass
unit
unit
Pulley 2
Pulley 1
Main motor
Magnetic
roller
roller
Drum
Transport
roller
roller
Fuser unit
Middle gear
3-2
Part description
Details
1
Feed the paper fed from sheet bypass paper
transfer roller to timing roller.
2
Feed the paper from sheet bypass tray to paper
feed roller.
3
Detect the paper in the sheet bypass tray.
4
Prevent multiple sheets from feeding.
5
Timing roller
After image registration of original and copy paper,
feed the paper to photo receptor.
6
Upper timing roller
After image registration of original and copy paper,
feed the paper to photo receptor.
7
Paper pass sensor
Detect paper just before timing roller.
8
Cleaning sheet
To prevent paper dust from sticking on photo
receptor, clean off the paper dust on the surfaces
of both timing rollers.
3. 2 Operation
(1)
Sheet bypass paper feed
1)
Construction of the sheet bypass paper feed unit
The construction of the sheet bypass paper feed unit consists of a sheet
bypass paper feed roller, transfer roller, paper pass sensor, DFP roller, and
timing roller.
Sheet bypass paper
feed roller
Sheet bypass paper
transfer roller
Sheet bypass paper
detecting sensor
Sheet bypass double
feed prevention roller
5
6
7
1
2
3
8
4
Sub Assemblies
3-3
2)
Operation of sheet bypass paper feed unit
• When choosing the sheet bypass tray and pressing Print, the revolution of
the main motor is transmitted to the transmission gear via respective driving
gears. Consequently, drive is transmitted to the timing roller gear of the sheet
bypass paper feed unit.
gears. Consequently, drive is transmitted to the timing roller gear of the sheet
bypass paper feed unit.
The revolution of the timing roller gear is transmitted to the sheet by-pass
clutch gear via an idle gear.
• When the sheet bypass solenoid is turned ON, the sheet bypass transfer
roller lowers and touches paper on the tray. The stopper is released at the
same time.
same time.
• Turning on the sheet bypass clutch, the transfer roller (which touches the
paper) and the paper feed roller rotate to transfer the paper into the machine.
• On the way to the timing roller (by the sheet by-pass paper feed roller), the
paper is detected by the paper pass sensor located before the timing roller.
After the specified time, the sheet bypass clutch turns off and the sheet bypass
roller and the sheet bypass transfer roller stop. Also, the sheet bypass
solenoid turns off and the transfer roller is lifted up. The paper touches the
timing roller and waits there.
After the specified time, the sheet bypass clutch turns off and the sheet bypass
roller and the sheet bypass transfer roller stop. Also, the sheet bypass
solenoid turns off and the transfer roller is lifted up. The paper touches the
timing roller and waits there.
• After a specified time following the optics system start, the optics home position
sensor detects the passing of the optics system (full-speed unit), the timing
clutch turns ON and the timing roller rotates. Accordingly the paper is fed into
the image transfer area and the registration of original and copy papers is
achieved.
clutch turns ON and the timing roller rotates. Accordingly the paper is fed into
the image transfer area and the registration of original and copy papers is
achieved.
• The double feed prevention roller contacts the sheet bypass paper feed roller
with the paper at a specific pressure. When multiple sheets are fed, the
rotating force of the double feed prevention roller is under specific torque,
and the double feed prevention roller rotates in reverse. Accordingly, the
bottom paper is put back in the drawer.
rotating force of the double feed prevention roller is under specific torque,
and the double feed prevention roller rotates in reverse. Accordingly, the
bottom paper is put back in the drawer.
(The torque is determined by the torque limiter).
• The paper pass sensor checks the paper feed from the drawer. When it does
• The paper pass sensor checks the paper feed from the drawer. When it does
not detect the paper pass in a specified time the Retry system is employed.
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