Various Controls and
Mechanisms
○Purpose : Here, you will lean about the various controls and mechanisms
associated with the fixing assembly.
1. Outline
The following controls are associated with
the fixing system:
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Now, let’s study the particulars of these
control mechanisms:
The machine changes the rotation speed of the
fixing film according to the temperature inside the machine at power-on and the
size of paper being used.
Specifically, the mechanisms include the
following:
a.fixing heater startup speed control
b.printing speed correction speed
c.throughput reduction control
a. Fixing Heater Startup Control
When the fixing assembly must be driven in a
low temperature environment, the speed at which the fixing film is rotated is
accelerated gradually.
When the fixing assembly is cold (e.g., early
in the morning), the hardened grease applied to the fixing film could cause the
fixing film to become displaced if the film was driven at a normal speed. If the
reading of the main thermistor is less than 100 deg C at power-on or during
recovery from sleep, the fixing motor is accelerated in steps (1/4 speed ->
1/2 speed -> normal speed).
b. Controlling the Rotation Speed of Fixing Film
1) Outline
The machine controls the rotation speed of
the fixing motor (M3) so that the fixing film will rotate at a specific speed at
all times.
The speed of the fixing film is checked by
the DC controller by monitoring the fixing film speed sensor (PS8), which is a
reflection type sensor attached to the rear edge of the fixing film. Also
attached to the fixing film is a reflector referred to as a marker. The signal
(film speed detection signal) generated by PS8 changes in response to light
hitting the reflector. The DC controller keeps track of the cycle of changes
that occur in the state of the signal to find out the rotation speed of the
fixing film. When the rotation speed of the fixing film is identical to the
target value, the DC controller controls the fixing motor to correct the
rotation speed of the fixing film.
1] Fixing film speed sensor (PS8)
[2] Marker (reflector)
[3] Fixing film (driven by the fixing motor)
[4] Pressure roller
[A] Direction of paper movement
[B] Film speed detection signal (FILM ROT D)
[C] Single rotation of the fixing film
M3 Fixing motor
2) Detecting a Fault
The machine is designed to monitor the
rotation of the fixing film to make sure that its rotation is
normal.
When the fixing motor (M3) is rotating
normally and, in addition, the reading of the main thermistor is in excess of
100 deg C, the DC controller will identify a fault in the rotation of the fixing
film if PS8 does not detect the marker for a specific period of
time.
The DC controller then will indicate an error
code (E007-0000) and disable printing operation.
c. Preventing Overheating at the Edges
When narrow paper (small-size paper) is used
continuously, the edge of the fixing heater would tend to overheat because of
the absence of contact with paper. If the reading of the sub thermistor (TH2)
exceeds 275 deg C in continuous printing mode, the DC controller increases the
distance between sheets of paper to decrease the temperature of the fixing
heater edges gradually. Thereafter, it will return the sheet-to-sheet distance
to normal as soon as the temperature at the edges has dropped to 265 deg
C.
The machine uses the fixing temperature
control mechanism to make sure that the toner image is permanently fused with
the fibers of paper; specifically, the mechanism consists of the
following:
a. warm-up temperature control
b. paper passage temperature control
c. sheet-to-sheet temperature control
a. Warm-Up Control
The machine controls the temperature of the
fixing heater at power-on and during recovery from sleep.
1) Wait-Up Temperature Control
The machine pre-heats the fixing heater
before increasing its temperature when the fixing assembly must be driven in a
low temperature environment. The grease applied to the fixing film tends to have
hardened in a low temperature environment (e.g., early in the morning). If the
fixing film was driven without a remedial mechanism, the fixing film could well
become displaced. To avoid such a fault, the machine supplies power to the
fixing heater before starting to drive the fixing film if the reading of the
main thermistor is less than 100 deg C at power-on or during recovery from
sleep, thereby softening the grease.
The control mechanism is executed in
combination with the fixing heater startup speed control.
2) Startup Temperature Control
The machine computes the best power supply
rate to increase the temperature of the fixing heater to a ready temperature in
a short period of time. The machine executes this control mechanism when the
reading of the main thermistor (TH1) is 180 deg or less in the following
sequence:
1) turns on the fixing heater at a 65% power supply
rate.
2) checks the changes in temperature occurring during a 400- to 500-msec
period from the start of the 65% power supply rate.
3) from the result of the check, computes the next power supply rate
X(%); then, supplies power using the resulting rate X(%).
4) checks the changes in temperature occurring during a 200- to 300-msec
period from the start of the X (%) power supply rate.
5) from the result of the check, computes the next power supply rate
Y(%); then, supplies paper using the resulting rate Y(%).
6) repeats 4) through 5) until the reading of TH1 reaches 180 deg
C.
7) when the reading reaches 180 deg C, shifts to paper passage
temperature control.
A: Startup control
B: Paper passage temperature control
C: 65(%) power supply
D: X(%) power supply
E: Y(%) power
supply
b. Paper Supply Temperature Control
The machine controls the temperature of the
fixing heater while paper moves past the fixing assembly.
The target temperature of the fixing heater
varies depending on the type of paper. In continuous printing mode, the
temperature of the pressure roller tends to increase gradually; for this reason,
the machine decreases the target temperature of the fixing heater as more and
more prints are made.
c.Sheet-to-Sheet Temperature Control
The machine decreases the temperature of the
fixing heater between sheets to prevent overheating of the fixing assembly in
continuous printing mode.
a. Outline
The machine is designed to clean the fixing
film and the pressure roller by removing toner sticking to them to prevent image
faults.
The machine drives the cleaning mechanism in
response to a command from the DC controller at such times as when recovery is
under way after removal of a jam. (There is a likelihood of the presence of an
appreciable amount of toner on the fixing film and the pressure
roller.)
The DC controller executes the following for
10 sec to move toner from the fixing film and the pressure roller to the fixing
cleaning roller.
∙ rotates the fixing film and the pressure
roller at 1/4 speed
∙ heats the fixing heater
to 220 deg C
You can cause the machine to execute cleaning
at a specific printing interval by making appropriate selections in service
mode. (For instructions, see the descriptions of the tasks of the service
person.)
[1]Toner
[2] Fixing cleaning rolle
[3] Fixing film
[4] Pressure roller
When the fixing cleaning roller becomes
clogged with toner, its cleaning efficiency will drop. Be sure that the roller
is replaced at the following intervals:
∙ if iR2270/2870, every
150,000 prints
∙ if iR2270/2870, every
240,000 prints
The machine is equipped with a mechanism that
automatically releases the fixing film so that the user may easily remove a
jam.
Normally, the fixing film unit [3] is forced
against the pressure roller [2] with the locking plates [9] pressing against the
fixing film stay [8] on both sides of the fixing film unit. The pressure roller
is released by decreasing the force of the locking plates. The mechanism of
release takes place as follows:
1) a jam occurs in the fixing assembly; in response, the user opens the
right door [6] to remove it;
2) when the right door is opened, the wire hook [7] found on the right
door pulls on the pressure release lug [4];
3) when the pressure release lug is pulled, the pressure release gear
[5] starts to rotate and, at the same time, the release lever [1] also
rotates;
4) when the release lever rotates, the release lever pushes up the
locking plate [9]; and
5) as it is pushed up, the locking plate is
released.
1] Release lever
[2] Pressure roller
[3] Fixing film unit
[4] Release rack
[5] Release gear
[6] Right door
[7] Wire hook
[8] Fixing film stay
[9] Locking plate
Fixing Assembly
Fixing Assembly
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