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FUSER UNIT
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13.5 Fuser Motor Control Circuit
The fuser motor, which is a DC motor driven by control signals from the ASIC on the LGC board, drives
the fuser roller.
A driving PC board is embedded in this motor to perform the following controls.
Fig. 13-9
1. ASIC outputs the control signals for the fuser motor rotation.
(HTRMT signal: Motor rotation command)
2. The excitation phase switching section excites each phase of the fuser motor.
→
The fuser motor is rotated.
3. Hall elements A, B and C detect the rotation position of the motor (rotor).
4. The excitation phase switching section switches the excitation of each phase.
(The motor keeps rotating by repeating from 2 to 4.)
5. An FG (Frequency Generator) pulse is generated by the rotation of the motor.
6. The FG pulse and the reference frequency (HTRCK-1) from the ASIC are compared in terms of the
phase and speed, and the difference is added to the excitation phase switching section.
Fluctuations in the power supply voltage are also added to the value. (Signal generation)
7. According to the result of step 6), the switching timing of the excitation phase switching section is
changed, namely, the FG pulse and the reference clock are controlled to be equal.
→
The fuser motor is rotated at a constant speed. (= Lock range)
8. When the HTRMT signal moves to a high level, the fuser motor is stopped.
9. When the pressure roller temperature is lowered to less than the reference value during the ready
status, the HTRML signal output from the ASIC moves to a low level. Thus the motor is rotated at a
low speed.
+36VD
+5VB
+36VD
Counter
+5VB
IC56
ASIC
IC58
Main CPU
HTRCK-1
HTRMT-0
IC39
Buffer
IC62
Buffer
LGC board
Pressure roller thermistor
temperature detection signal
Rotation
control
[PC board section]
[Motor section]
Phase W
Phase V
Phase U
Hall element C
FG pulse
Hall element A
Hall element B
Wave
correction
Phase
comparator
Speed
comparator
Voltage
detection
circuit
Excitation
phase
switching
section
Rotor
position
detection
Fuser motor
Difference
Difference
Deceleration
control
circuit
HTRML-0