Brother HL-7050 Service Manual page 116

2.6.5 Cleaning
If the toner is not transferred onto the paper perfectly, it is possible that there may be residual
toner and the paper dust on the photo-conductive drum.
The residual toner is drawn to the cleaning roller by charging lower voltage compared to the
electric potential of the drum surface.
The residual paper dust is drawn to the cleaning roller by charging higher voltage compared to
the electric potential of the drum surface. At this time, the cleaning shaft is charged 100V
higher voltage compared to the voltage charged to the cleaning roller. The paper dust drawn to
the cleaning roller moves to the cleaning shaft, and it is collected by the sponge. The paper
dust collected by the sponge is kept into the front part of the drum unit.
2.6.6 Fixing stage
The image transferred to the paper by static electricity is fixed by heat and pressure when
passing through the heat roller and the pressure roller in the fixing unit.
The heat roller of the fixing unit is heated by two heaters. (two halogen lamps)
One of the heaters (center heater) mainly heats the central part of the heat roller, and the other
heater (side heater) mainly heats the outer edges of the heat roller. The heatroller temperature
is detected by two corresponding thermistors (center thermistor, side thermistor).
The thermistor keeps the surface temperature of the heat roller constant by detecting the
surface temperature of the heat roller and turning on or off the halogen heater lamp.
These two heaters are controlled independently to keep the heat roller temperature uniform
through the longitudinal direction of the heat roller regardless of the paper width.
Photosensitive drum
Fig.3-21
Fig. 3-22
3-21
HL-7050 SERVICE MANUAL
Cleaning shaft
Cleaner roller