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AR-M550/M620  DETAILS OF EACH SECTION  6 - 100

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

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.

Copy

Paper
exit

Fusing roller 
(Heating)

Sub power PWB

Fusing 
motor

Paper exit 
roller

Heater lamps 
(2 pcs.)

Fusing roller 
(Pressing)

Cleaning 
roller

Auxiliary 
heat roller

Heat lamp 
(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

7

5

2

Sub power PWB

2

Cross-
sectional 
view of 
connector

AR-M550/M620  DETAILS OF EACH SECTION  6 - 102

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 DC brushless motor is driven according to the control
signal sent from the PCU.

The surface temperature of the heat roller detected by the thermistor 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 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.

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.

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)

Thermistor Detects the surface temperature of the fusing roller 

(heating).

Analog input

RTH2

RTH2

Fusing temperature 
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)]

HLTS2

HLTS2

Thermostat (2)

Shuts conduction to the heater lamp when the 
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)

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]

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).

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).

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.

This is because toner on paper must be heated from above and below
to be fused on paper. 

The fusing rollers (heating/pressing) are of silicon rubber because of
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.)

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.)

The temperature sensor is provided at the center of the fusing 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.

In addition, the fusing temperature is switched according to the kind of
paper. 

The fusing roller removes toner and dusts from the heat roller and the
pressure roller surfaces by the following two methods.

1.

Sub-heat roller (Heating): Clean the sub heat roller with the clean-
ing sheet.

2.

Fusing roller (Pressing): Mechanical cleaning by the cleaning 
roller

Mode

Paper

Fusing roller

Auxiliary heat 

roller

Ready 
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