Canon iR3245, Service Manual

Page: 285 / 746

Chapter 9
9-3
9.3 Various Control Mechanisms
9.3.1 Controlling the Speed of the Fixing Film
9.3.1.1 Controlling the Fixing Film Speed in Response to Low Temperature
0018-9774
iR3225 / iR3225N / iR3235 / iR3235N / iR3245 / iR3245N
As in the morning, driving the fixing film in a low-temperature environment without warm-up could cause the film to become displaced. In consideration of this
fact, the fixing motor (M3) is started up in phases (1/4 speed to 1/2 speed and then to normal speed).
9.3.1.2 Controlling the Fixing Film Speed
0018-9775
iR3225 / iR3225N / iR3235 / iR3235N / iR3245 / iR3245N
The rotation cycle of the fixing film is monitored to control the fixing motor (M3) to a specific speed.
When the fixing film rotates and, as a result, the reflecting member positioned in the loop of the film approaches the speed sensor, the machine detects the rotation
of the fixing film.
F-9-2
[1] Speed sensor
[2] Reflecting member
[3] Fixing film (driven by fixing motor)
[4] Pressure roller
[A] Paper feed direction
[B] Speed sensor output
[C] 1 rotation of fixing film
Timing of Control
The speed of fixing film rotation is monitored at all times after the fixing motor goes on and its speed reaches a specific value. The speed of the fixing motor is then
controlled so that it remains at a specific level at all times.
9.3.2 Controlling the Fixing Film Temperature
9.3.2.1 Controlling the Power Supply in Response to Low Temperature
0018-9776
iR3225 / iR3225N / iR3235 / iR3235N / iR3245 / iR3245N
In a low temperature environment, sufficient torque may not be generated because the grease applied to the fixing film has not been softened, causing the fixing
performance level to decrease.
In the mechanism of controlling the fixing film, the fixing heater (H1/H11, H2/H12) is supplied with power before the fixing film is driven so as to soften the grease.
If the temperature of the fixing film detected by the fixing thermistor (TH1, TH2) is lower than a specific level, the heater is supplied with power for a specific
period of time before a normal start-up mechanism is initiated.
If the temperature of the fixing film detected by the thermistor is higher than a specific level, the normal start-up mechanism is initiated.
9.3.2.2 Controlling the Feeding in Response to Low Temperature
0018-9777
iR3225 / iR3225N / iR3235 / iR3235N / iR3245 / iR3245N
In a low temperature environment, the feeding timing is changed according to the temperature detected by the environment sensor (HU1) so as to enhance the fixing
capability. The details are described below.
When the environment sensor detection temperature is 15 deg C or less, the feeding timing is delayed by 5000 msec.
In thick paper mode, the feeding timing is not changed even if the environment sensor detection temperature is 15 deg C or less.
[C]
[2]
[B]
[A]
Off
On
[4]
[1]
[3]