Scanner System - Canon LBP1760P Service Manual

CHAPTER 2
C. Scanner System
Figure 2-3-4 is the scanner motor control circuit.
Engine controller PCB
Frequency
comparator
J53-2 /PRNT
6
P67
Standard
Oscillator
CPU(IC501)
The scanner motor is a three-phase, eight-pole DC brushless motor with hall elements, and is
unified with the drive circuit.
When the printer is turned ON, the CPU (IC501) on the engine controller divides the oscilla-
tion frequency of the crystal oscillator (X501) and generates standard clock.
When the /PRNT signal sent to the CPU becomes "L," the CPU sets the SCANNER MOTOR
ACCELERATION signal (/ACC) to "L." The scanner driver IC rotates the scanner motor when the
/ACC signal is "L" and accelerates while the /ACC signal is "L."
While the scanner motor is rotating, the CPU forces laser emission, and the /BDI signal is
sent from the BD PCB. The CPU compares the /BDI signal cycle with the standard clock in the
frequency comparator of the CPU and controls the rotation speed of the scanner motor by con-
trolling the /ACC signal until the the scanner motor reaches the prescribed speed.
When stopping the scanner, the CPU decelerates the scanner rotation by setting the SCAN-
NER MOTOR DECELERATION signal (/DEC) to "L."
The CPU monitors the /BDI signal sent from the BD PCB to judge whether the scanner motor
2 - 26
/BDI
J53-6
+24VA
J53-1
/ACC J53-2
/ACC 90
/DEC J53-3
/DEC
89
J53-4
clock
X501
64
X1
X2 63
Figure 2-3-4
Laser/scanner unit
J551-2
+24VA
J401-4
Scanner driver IC
J401-3
Integration
circuit
J401-2
J401-1
BD PCB
Scanner motor
Drive
circuit
M