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I
OPERATIONS
AND
TIMING!
B.
Fixing
and Paper
Delivery
Assemblies
1.
Outline
The
upper and
lower
rollers of
the
fixing
assembly
are driven
by
the
main motor
(M1).
The
upper
roller
is
heated by a
single
heater
(H1:900W).
When
the surface
temperature
of
the
roller
rises,
the resistance
of
the thermistor (TH)
falls,
so
the voltage
of
the
signal that
it
produces FIXING
ROLLER
SURFACE TEMPERATURE
signal
(TH1)
also
falls.
Whether
the voltage
of
TH1
(analog)
is
above
or
below a
certain
level
at
a
given time
determines
if
the
microprocessor
of
the
DC
controller
makes
the
HEATER
DRIVE
com-
mand
(HTRD)
"1"
or
"0".
The NP-1550
is
provided
with the
following
three protection
mechanisms:
•
The
microprocessor monitors
the
voltage
of
TH1
and
indicates 'E000'
o
r
'E001'
in
response
to
an
error,
i.e.,
ACOFF
goes
'0'
to
turn
the
relay
(S105)
OFF,
thereby
cutting
the
power
to
the
fixing
heater.
•
The
fixing roller
error
detection
circuit
monitors
the voltage
of
TH1
and,
when
it
drops below 0.9V
(equivalent
of
215°C),
turns
HTRD
OFF.
•
The
thermo
switch (TS1)
goes
OFF
when
the
temperature
of
its
inside rises
to
230°C
to
cut
off
the
power
to
the
fixing
heater.
'Trie
thermo
switch (TS1)
cannot
be
used
after
its
contact
has opened;
the
i<;e^ht^:yplhnc>fi'y^
at
room
temperature.
Fixing
roller
heater
H1
900W
Upper
fixing roller
J317
:
2
Delivery
rollers
Lower
fixing roller
Thermo-switch
TS1
(F1
)
230°C
©i
Thermistor (TH)
\l
S105
•y?r
lV/T
JZ.
J306-2
.
24V
HTRD
|
J304-4I
5V
!
CWT)
24V
L__
I
AC
driver
PCB
J306-4i
ACOFF
L_
r
DC
controller
PCB
Figure 3-39
COPYRIGHT©
1992
CANON
INC.
CANON
NP-1550
REV.1 SEPT. 1992
PRINTED
IN
JAPAN
(IHPRIME
AU JAPON]
3-35
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