Sharp MX-M550U Service Manual page 363

No. Name
1 Heat roller
2 Separation pawl
3 Pressure roller
4 Sub heat roller
5 Separation pawl
6 Cleaning sheet
7 CL roller
8 Web roller
9 Pressure roller
10 Lower CL roller DG2
2. Operational descriptions
A. General
This section performs the following functions and operations.
1) Toner attached to paper in the transfer section are heated and
pressed by the fusing roller onto paper to fuse.
2) The sub heat roller is used to improve fusing capacity and sep-
aration capacity after fusing.
Paper
Copy
exit
Paper exit
roller
B. Fusing unit drive
To drive the fusing unit, the drive power is transmitted from the
drive motor (FUM) through the connection gear to the upper heat
roller gear.
The drive motor (stepping motor) is driven according to the control
signal sent from the PCU.
PCU
C. Heater lamp drive
The surface temperature of the heat roller detected by the ther-
mistor is sent to the PCU.
When the temperature is lower than the specified level, the heater
lamp lighting signal is sent from the PCU to the heater lamp drive
circuit in the sub power PWB.
The power triac in the heater lamp drive circuit is turned on, and the
AC power is supplied to the heater lamp, lighting the lamp and
heating the heat roller.
To prepare for an abnormally high temperature of the heat roller,
the thermostat is provided for safety.
When the thermostat is opened, power supply (AC line) to the
heater lamp is cut off.
Heats and presses toner on paper and fuses it on paper.
Mechanically separates paper which was not separated naturally
from the heat roller.
Heats and presses toner on paper and fuses it on paper.
Heats the pressure roller.
Mechanically separates paper which was not separated naturally
from the pressure roller.
Clean the sub heat roller surface.
Clean the pressure roller.
Clean the heat roller.
Applies a pressure to web paper to connect the heat roller.
Clean the pressure roller.
Fusing
Pressure
Heat roller
roller
Fusing Heater lamps Sub heat
roller
motor (2 pcs.)
Heat lamp
Sub power PWB
(1 pc)
FUM
MX-M700N FUSING SECTION N – 2
Function/Operation
D. Fusing operation
Toner on paper is heated and pressed to be fused by the heat
roller.
Heat roller
HL2
Paper exit
Two heater lamps are provided for the heat roller and one heater
lamp is provided for the sub heat roller for the pressure roller to sub
heat paper from above and below.
This is because toner on paper must be heated from above and
below to be fused on paper.
Pressure roller are of silicon rubber because of the following rea-
sons and purpose. This is the following reason, objective.
1) Paper is separated upward. (Since the heat roller is of higher
hardness, the pressure roller is deformed to separate paper
upward.)
2) The nip quantity is increased to increase heat capacity for
paper.
3) By pressing paper with the flexible roller, toner is fused without
deformation. (The flatness, however, is not so high.)
Active
condition
HL1
Pressure roller
HL3
Sub heat roller
NOTE