q When the Level of Toner Is AdequateThe presence of toner around the toner level sensor causes the AC bias generatedby the sensor to be larger than the reference signal.The condition causes the output from the comparator circuit to go ‘1’ and the tonerout signal (TEP*) to go ‘0’.w When the Level of toner Is InadequateThe toner around the toner level sensor decreases in amount, causing the AC biasgenerated by the sensor to lower.Since the reference signal, on the other hand, remains unchanged, the outputvoltage remains high.The difference in the potential causes the output of the comparator circuit to go ‘0’,causing the toner out signal (TEP*) to go ‘1’.The condition causes the microprocessor (Q301) in the DC controller cirucit to makechecks only during copying operating (AC bias ON); if it detects the toner out signal=0,each lasting 0.25 sec or more, for a total time equivalent of three copies, the Cartridgeindicator is flashed on the display of the control panel.e Torque LimiterIf an excessive load is imposed on the photosensitive drum because of excessiveamounts of waste toner or some other reason while the drum is rotating, the torquelimiter cuts off the drive from the main motor to stop the rotating of the drum.Figure 4-203COPYRIGHT © 1997 CANON INC. CANON NP6218 REV. 0 MAY 1997 PRINTED IN JAPAN (IMPRIME AU JAPON)CHAPTER 4 IMAGE FORMATION SYSTEM4-24STBYCopy Start keyONMain motor (M1)Toner level detection timingToner out signal (TEP*)AC biasPower switchONCartridge indicatorflashing timingA4, AE3 copies, continuous modeCartridge indicator (tlashing)1st (3 sec) 2nd (1 sec) 3rd (0.5 sec)Copy STBY Copy STBY Copy
