Toshiba 4580, Service Manual

Page: 254 / 379

Mar. 1999 © TOSHIBA TEC 14 - 7 6570/5570 FUSER UNIT
14.5 Heat-Roller Motor Drive
14.5.1 Outline of operation
(1) The LGC transmits control signals for the heat-roller motor rotation (HTRMOT:Motor rotation com-
mand).
(2) The excited phase switching unit excites each phase on the heat roller motor
→
Heat roller motor
rotates.
(3) Hall elements A to C are used to detect the rotation position of the motor (or rotor).
(4) The excited phase switching unit switches the excitation for each phase (By repeating steps (2)
through (4) above, the motor keeps rotating.).
(5) An FG pulse is generated by the rotation of the heat roller motor.
(6) The phases and velocities of the FG pulse and the reference frequency from the SUB are compared,
and the differences are added up. In addition to this are added the fluctuations in the supply voltage
(Signal generation).
(7) The switching timing for the excited phase switching unit is changed to match the signal obtained in
step (6).
That is, control ensures that the FG pulse and reference frequency are equal.
→
The heat roller
motor runs at a constant speed (Locked range state.).
(8) When the HTRMOT signal changes to “H” level, the heat roller motor stops.
(9) During standby, the HTRMOTL level changes to “L” if the temperature of the lower heat roller drops
below the reference temperature, and the heat roller motor rotates at low speed.
Fig. 14.5-1
Phase
comparator
Voltage
detection
circuit
Rotation
control
Roter
position
detector
Excited
phase
switching
unit
Speed
comparator
Wave
shaping
Control
signal
Difference
Difference
Reference
requency
HTR MOT
HTR MOTL
(H-MOT-REF)
+36A
FG pulse
W
V
U
A
C
Heat roller motor
B
M/DC-HTR-300N
U, V, W: Phase
A, B, C: Hall element