Loop control
The loop control stabilizes the paper feed operation before the paper enters the fuser. If the pressure roller
rotates slower than the secondary transfer roller, the paper loop increases and an image defect or paper
crease occurs. If the pressure roller rotates faster than the secondary transfer roller, the paper loop
decreases and a vertical scanning magnification failure occurs because the pressure roller pulls the paper.
To prevent these problems, loop sensor 1 and loop sensor 2 detect the paper loop before the paper enters
the fuser. The DC controller adjusts the rotational speed of the fuser motor according to the output signals
from the loop sensors and maintains the paper loop. Loop sensor 1 is for light media, and loop sensor 2 is for
heavy media. The DC controller slows the fuser motor when the sensor is off and speeds up the sensor when
the sensor is on.
Figure 1-43 Loop-control mechanism
Pressure roller
The pressure roller rotates faster
than the secondary transfer roller
Loop sensor: OFF
SR14: Loop sensor 1
SR15: Loop sensor 2
Sensor flag
ITB
Loop sensor 1,2
Secondary transfer rollerr
Pressure roller
For light media
For heavy media
Sensor flag
Sensor flag
Loop sensor: ON
The pressure roller rotates slower
than the secondary transfer roller
ENWW Pickup, feed, and delivery system 57
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