Canon iR C1020 Series, Service Manual

Page: 141 / 408

Chapter 7
7-5
7.3 Controlling the Laser Scanner Motor
7.3.1 Overview
0019-5010
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.
F-7-4
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.
7.3.2 Failure Detection
0019-5011
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.
ASIC (IC1010)
DC controller PCB
CPU
(IC1001)
Scanner motor drive PCB for M/C
+24VA +24VA
BD circuit
Laser driver PCB
Scanner driver IC
Scanner motor
/SCNMACC
/SCNMDEC
X1001
/BD1I
Frequency
comparator
Reference
clock
Oscillator
Drive
circuit
Integration
circuit
M