Controlling The Laser Scanner Motor; Overview; Failure Detection - Canon Color imageCLASS MF9170c Service Manual

6.3 Controlling the Laser Scanner Motor

6.3.1 Overview

imageCLASS MF9170c / imageCLASS MF9150c / imageCLASS MF8450c
In the DC controller, the scanner motor control is performed to emit the laser beam at the correct position on the photosensitive drum.
The scanner motor control is to rotate the scanner motor at its specified speed and phase.
- Speed control
The scanner motor is rotated at a specified speed.
- Phase control
The phase difference of the 2 polygon mirrors is adjusted while the scanner motor is rotating at a low speed to eliminate line displacement attributed to the
rotation and prevent color displacement in the sub scanning direction.
There are two scanner motors: one is for M/C and the other is for Y/Bk. The configurations of both motors are identical.
DC controller PCB
CPU
(IC1001)
The DC controller PCB generates the reference clock based on the oscillation frequency of the oscillator (X1001).
It compares the intervals between the reference clock and the BD input signal (/BD1I) sent from the laser driver PCB with the frequency comparator, and monitors
the rotational counter of the scanner motor.
It controls the rotational speed of the scanner motor by sending the scanner motor acceleration signal (/SCNMACC) or the scanner motor deceleration signal (/
SCNMDEC) to the scanner motor driver based on the detected rotational speed.

6.3.2 Failure Detection

imageCLASS MF9170c / imageCLASS MF9150c / imageCLASS MF8450c
In the DC controller, the fault in the scanner motor is detected.
The CPU (IC1001) monitors the frequency comparator in the ASIC (IC1010) and determines whether the scanner motor rotates at its specified rotational speed or
not.
When the CPU encounters the following conditions, it determines the scanner motor failure, stops the printer engine, and displays 'E100 (optical unit failure)" on
the control panel.
- Abnormal scanner motor
The scanner motor does not enter scanner ready mode within 5 seconds of scanner motor start-up.
- BD error
- The /BDI signal cannot be detected within 1.5 seconds of once the scanner motor reached at its specified rotational speed.
- The interval of the /BDI signal goes out of the tolerance for 0.5 second continuously after the scanner motor once reached at its specified rotational speed.
+24VA
Frequency
comparator
Reference
clock
X1001
Oscillator
ASIC (IC1010)
Laser driver PCB
/BD1I
+24VA
Scanner driver IC
/SCNMACC
Integration
circuit
/SCNMDEC
Scanner motor
Scanner motor drive PCB for M/C
F-6-4
Chapter 6
BD circuit
Drive
circuit
M
0019-5010
0019-5011
6-5