Brother International HL-3400CN Service Manual - Page 91

CHAPTER

4

STRUCTURE

OF

SYSTEM

COMPONENTS

(

3

)

Control

of

the

Fusing

Temperature

Each

roller

of

the

fusing

unit

is

controlled

to

maintain

the

appropriate

temperature

so

that

toner

will

be

fixed

correctly

onto

the

print

paper.

<Basic

Structure

of

Temperature

Control

(Fig.4-36)>

FLS:

Thyristor

to

switch

the

power

supply

to

the

heat

lamp.

TFU1fTFU2:

Temperature

fuse

to

shut

down

the

circuit

for

safety

when

the

temperature

becomes

too

hot

within

the

fixing

unit.

TH:

Temperature

sensor

to

detect

the

surface

temperature

of

the

heat

roller

(HR).

RY:

Relay

to

prevent

further

heating

when

it

becomes

hotter

than

the

set

temperature

within

the

fixing

unit.

GA/CPU:

Process

circuit

to

control

the

temperature

signal

(micro

computer).

CM1:

Sensor

circuit

for

temperature

signal

(for

ACOFF

signal).

CM2:

Sensor

circuit

for

temperature

signal

(for

HON

signal).

CM3:

Sensor

circuit

for

temperature

signal

(for

processing).

Q:

Sensor

circuit

for

shut

-down

by

the

thermistor

(for

THERR

signal).

HR:

Heat

lamp

for

the

heat

roller.

BR:

Heat

lamp

for

the

back-up

roller.

<

Signal

Functions

>

HON

-N

To

turn

on/off

the

heater

inside

the

fuser

roller.

ACOFF

To

turn

off

the

relay

RY1

if

overheat

occurs.

THERR

To

detect

the

shut

-down

by

the

thermistor.

AD

To

convert

the

temperature

sensing

signal

to

AD.

<Controlled

Temperature

and

Safety>

Temperature

(t)

,--,

-,'

Time

Fig.

4-35

TPS

TA

150

°

C

TS

4-40

Brother International HL-3400CN Service Manual - Page 91

<Controlled

Page 91 highlights