3–89OPERATIONS AND TIMINGCOPYRIGHT © 1998 CANON INC. CANON NP6621 REV.0 FEB. 1998 PRINTED IN JAPAN (IMPRIME AU JAPON)The copier is equipped with three protectionmechanisms to prevent the fixing heater from goingON at wrong timing.• The microprocessor monitors the voltage ofTH1 and indicates ‘E000’ or ‘E001’ or ‘E002’or ‘H003’ in response to an error.• If the voltage of TH1 and TH2 falls belowabout 0.9 V (equivalent of 215°C), the errordetection circuit cuts off the supply power tothe fixing heater regardless of the output ofthe microprocessor.If the inside temperature of the thermal switchrises above 220°C, the power to the fixing heaterwill be off.Note:Once the contact of the thermoswitch (TS1)opens, the thermoswitch cannot be used unlesscooled to 0°C or less; the contact will not recoverat ambient temperature.2. Oil Application RollerThe upper fixing roller is provided with an oilapplication roller for cleaning and application of oil.Normally, the oil application roller remains awayfrom the fixing roller, and it comes into contact withthe upper fixing roller only when copy paper passesthrough.The mechanism is driven by the oil applicationsolenoid (SL6); SL6 goes ON 1 sec after theregistration roller goes ON; it then goes OFF assoon as the main motor (M1) goes OFF therebybringing the oil application roller into contact withthe upper fixing roller.Table 3-442Thermoswitch(220˚C)Fixing heater(H1)Upper fixing rollerDelivery rollerMain motorThermistor(TH1);MainThermistor(TH2);AuxiliaryJ324A-4J324A- 1J319- 1-2-3-4TH1HTON- 3 HTRDJ307-2Microprocessor(slave)Microprocessor(master)Error detectioncircuitOil application rollerOil application solenoidLower fixing rollerPower supplyRelay(K1)TS1SSRSSR ONdetection24VM1SL6DC controller PCBACOFFSL6DCleaning roller
