Canon MF4690 - ImageCLASS B/W Laser Service Manual

Also see for ImageCLASS MF4690: Reference guide Instructions Starter Guide Operation guide Driver guide

Contents

Chapter 55-35.4 Controlling the Laser Scanner Motor5.4.1 Overview 0016-1836This is the control to rotate the scanner motor at constant speed.The scanner motor is the 3-phase DC brush-less motor with hall element included, and is combined with the drive circuit.The following chart shows the control circuit for the scanner motor.F-5-35.4.2 Scanner Motor Speed Control 0016-1837This is the control to rotate the scanner motor at constant speed.The following is the procedure of this control.1) At activating the scanner motor, CPU outputs /ACC signal to the scanner driver IC to accelerate the scanner motor forcedly. The scanner motor will start rotating.2) CPU periodically turns on the laser, and compares /BDI signal and the cycle of the reference clock to detect the rotation of the scanner motor.3) When the rotation of the scanner motor exceeds the specified value, CPU outputs /DEC signal to decelerate the scanner motor. CPU controls /ACC or /DECsignal to control the rotation of the scanner motor until it becomes its specified value.5.4.3 Detection of Fault of the Scanner Motor 0016-1838CPU of the DCNT board monitors the frequency comparator to judge if the scanner motor rotates at the specified rotation frequency.When the following statuses occur, CPU judges that there is a fault or error and stops the engine. At the same time, it notices the details of the error to the SCNTboard.1) Scanner faultIf /BDI signal cannot be detected 1.5 sec after completing forced acceleration of the scanner motor, extend the detection time by 120sec. If the specified cycle of /BDI signal cannot be detected, it should be judged as scanner fault.2) BD faultIf /BDI signal cannot be detected in 100msec after forced acceleration of the scanner motor or the specified cycle of /BDI signal cannot be detected for 2 sec ormore after the scanner motor reached its specified rotation, it should be judged as BD fault.3) BD errorIf /BDI signal cannot be detected at the specified cycle while CPU outputs /BD signal to the SCNT board, it should be judged as BD error.If door open is detected in 200msec after BD error was detected, CPU does not transmit BD error to the SCNT board.DCNT boardMJ931-9X902IC902CPUJ932-4J932-3J932-2J932-1J902-1J904-1J904-2J904-3J904-4/ACC/DEC/BDI BD sensorDividerReferenceclockFrequencycomparatorLaser / scanner blockIntegrationcircuitScanner driver ICScanner motorDrivecircuit+24V +24V