Canon MF8100 Series, Service Manual, Page: 76 / 296

Chapter 2
2-40
2) When the pulse count for ENCODER DETECTION signal does not fit in the prescribed range, (within -/+ 200 of a targeted pulse count memorized by CPU
)after a period of time from the start of the drive when the developing rotary motor becomes Ready.
The encoder used in this printer consists of a disk, reflective sensor, and detection unit. The disk is installed on the motor shaft. The disk rotates as the motor does.
The disk has reflective areas and interrupting areas alternately located on its surface. The sensor strikes light to the rotating disk and sends the monitoring results
of the reflected light to the detection unit. The detection unit monitors the results constantly. It generates the two ENCODER DETECTION (ENCSNS1, ENCSNS2)
signals based on the tim-ing of detecting the reflective and interrupting areas on the disk and sends the signals to the DC controller.
F-2-55
2.6.2.6 Cooling Fan
0008-1730
The Cooling fan, a DC brushless motor with a built-in Hall device, cools off around the fixing unit, power supply unit, high-voltage power supply PCB, and car-
tridge.
The CPU (IC101) controls the cooling fan.
The CPU outputs the FAN DRIVE (FAN1D) signal after receiving a print command from the interface controller and rotates the cooling fan. After the completion
of a print operation, the CPU rotates the fan for a specified period based on internal temperature by monitoring the internal temperature detection thermistor (TH3).
Then it stops the fan.(Refer to the table below)
The CPU monitors the FAN LOCK DETECTION (/FAN1S) signal while the cooling fan is rotating. If the signal remains "H" continuously for more than 10 sec-
onds, the CPU determines a fan failure, then stops the printer engine, and notifies the failure to the interface controller.
F-2-56
T-2-9
Thermistor detection temparature (deg C) Fan rotation time (s)
44 or less 0
45 to 49 30
50 or more 300
ENCSNS1
ENCSNS2
ROTHPS
Start of ENCODER DETECTION
signal monitoring
(Normal speed)
ENCSNS2
(Slow)
ENCSNS2
(Fast)
Delayed
Hastened
ENCSNS1
Delayed
ENCSNS1
T
Hastened
T
Disk
Reflecting
areas
Interrupting
areas
Motor
shaft
Reflective
sensor
Sensor output
ENCSNS1
ENCSNS2
Detection
unit
IC101
CPU
FAN1D
/FAN1S
FM721
J123
-1
-3
+24VB
DCNT board
SLVTH
J137
-1
TH3
Internal temperature
detection thermistor
Fan motor
control circuit
Cooling fan