Sharp AR-M550 (serv.man12) Service Manual ▷ View online
AR-M550/M620 DETAILS OF EACH SECTION 6 - 100
a-21. Document size detection light receiving PWB
1) Remove the operation base plate A.
2) Remove the document size detection light receiving PWB., and
disconnect the connector.
AR-M550/M620 DETAILS OF EACH SECTION 6 - 101
6. Fusing section
A.
General
This section performs the following functions and operations.
1) Toner attached to paper in the transfer section are heated and
pressed onto paper to fuse.
2) The auxiliary heat roller is used to improve fusing capacity and
separation capacity after fusing.
B. Major parts and signal functions
Copy
Paper
exit
exit
Fusing roller
(Heating)
(Heating)
Sub power PWB
Fusing
motor
motor
Paper exit
roller
roller
Heater lamps
(2 pcs.)
(2 pcs.)
Fusing roller
(Pressing)
(Pressing)
Cleaning
roller
roller
Auxiliary
heat roller
heat roller
Heat lamp
(1 pc)
(1 pc)
Fusing
Drawer connector
RT H1
RTH2
RTH 3
HLTS1
HLTS2
HL1
HL
FUM
2
HL3
HLTS3
1
2
2
1
1
2
3
4
4
3
2
1
A
B
A
B
PCU
4
3
1
6
8
8
7
5
2
Sub power PWB
2
Cross-
sectional
view of
connector
sectional
view of
connector
AR-M550/M620 DETAILS OF EACH SECTION 6 - 102
C. Details of operations
(1)
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.
motor (FUM) through the connection gear to the upper heat roller gear.
The drive motor DC brushless motor is driven according to the control
signal sent from the PCU.
signal sent from the PCU.
(2) Heater lamp drive
The surface temperature of the heat roller detected by the thermistor is
sent to the PCU.
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 cir-
cuit in the sub power PWB.
lamp lighting signal is sent from the PCU to the heater lamp drive cir-
cuit 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.
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.
thermostat is provided for safety.
When the thermostat is opened, power supply (AC line) to the heater
lamp is cut off.
lamp is cut off.
(3) Fusing operation
Toner on paper is heated and pressed to be fused by the heat roller.
Code
Signal
name
Name
Type
Function/Operation
Active condition
Note
RTH1
RTH1
Fusing temperature
sensor (1)
sensor (1)
Thermistor Detects the surface temperature of the fusing roller
(heating).
Analog input
RTH2
RTH2
Fusing temperature
sensor (2)
sensor (2)
Thermistor Detects the surface temperature of the fusing roller
(heating).
Analog input
HLTS1
HLTS1
Thermostat (1)
Shuts conduction to the heater lamp when the
temperature rises abnormally. [For the fusing roller
(heating)]
temperature rises abnormally. [For the fusing roller
(heating)]
HLTS2
HLTS2
Thermostat (2)
Shuts conduction to the heater lamp when the
temperature rises abnormally. [For the fusing roller
(heating)]
temperature rises abnormally. [For the fusing roller
(heating)]
HL1
HL1
Heater lamp (1)
Heats the fusing roller (heating).
HL2
HL2
Heater lamp (2)
Heats the fusing roller (heating).
RTH3
RTH3
Fusing temperature
sensor (3)
sensor (3)
Thermistor Detects the surface temperature of the auxiliary heat
roller.
HLTS3
HLTS3
Thermostat (3)
Shuts conduction to the heater lamp when the
temperature rises abnormally. [For the auxiliary heat
roller]
temperature rises abnormally. [For the auxiliary heat
roller]
Analog input
HL3
HL3
Heater lamp (3)
Heats the auxiliary heat roller.
FUM
FUM
Fusing motor
Drives the fusing unit.
No.
Name
Function/Operation
Active
condition
Note
1
Fusing roller (heating)
Heats toner on paper and fuses it on paper.
2
Separation pawl
Mechanically separates paper which was not separated naturally from the
fusing roller (heating).
fusing roller (heating).
3
Fusing roller (pressing)
Heats and presses toner on paper.
4
Auxiliary heat roller
Heats the fusing roller (pressing).
5
Separation pawl
Mechanically separates paper which was not separated naturally from the
fusing roller (heating).
fusing roller (heating).
6
Discharge brush
Discharges the fusing roller.
7
Fusing cleaning scraper
Cleans the surface of the fusing roller (pressing).
8
Cleaning sheet
Clean the sub heat roller surface.
FUM
PCU
Fusing roller (Heating)
HL2
HL1
---------
---------
Fusing roller (Pressing)
HL3
Auxiliary heat roller
Paper exit
AR-M550/M620 DETAILS OF EACH SECTION 6 - 103
Two heater lamps are provided for the fusing heat roller (heating) and
one heater lamp is provided for the auxiliary heat roller for the fusing
roller (pressing) to heat paper from above and below.
one heater lamp is provided for the auxiliary heat roller for the fusing
roller (pressing) to heat paper from above and below.
This is because toner on paper must be heated from above and below
to be fused on paper.
to be fused on paper.
The fusing rollers (heating/pressing) are of silicon rubber because of
the following reasons and purpose.
the following reasons and purpose.
1) Paper is separated upward. (Since the fusing roller (heating) is of
higher hardness, the fusing roller (pressing) is deformed to sepa-
rate paper upward.)
rate 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.)
(4) Fusing temperature control
The temperature sensor is provided at the center of the fusing roller
(heating) and the auxiliary heat roller.
(heating) and the auxiliary heat roller.
The roller temperature is detected by the installed temperature sensor,
and the heater lamp is controlled so that the temperature is maintained
at the specified level.
and the heater lamp is controlled so that the temperature is maintained
at the specified level.
In addition, the fusing temperature is switched according to the kind of
paper.
paper.
(5) Cleaning operation
The fusing roller removes toner and dusts from the heat roller and the
pressure roller surfaces by the following two methods.
pressure roller surfaces by the following two methods.
1.
Sub-heat roller (Heating): Clean the sub heat roller with the clean-
ing sheet.
ing sheet.
2.
Fusing roller (Pressing): Mechanical cleaning by the cleaning
roller
roller
Mode
Paper
Fusing roller
Auxiliary heat
roller
Ready
condition
print mode
condition
print mode
Normal paper
185°C
185°C
Heavy paper
220°C
220°C
Tab paper
220°C
220°C
Postcard
220°C
220°C
Pre-heat
–
140°C
140°C
No.
Name
1
Cleaning sheet
2
Fusing roller (Pressing)
3
Cleaning roller
4
Discharge brush
5
Fusing roller (Heating)
6
Sub-heat roller
5
2
4
3
6
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