Canon MF4500 Series Service Manual

Canon MF4500 Series Service Manual Manual pdf 48 page image

22 2-232-23Technical Overview > Fixing System > Various Control Mechanisms > Protective FunctionsTechnical Overview > Fixing System > Various Control Mechanisms > Protective FunctionsVarious Control Mechanisms■ Fixing Temperature Control● Heater Temperature ControlThe heater temperature control is to keep the fixing heater in the fixing film unit to thespecified temperature.The engine controller monitors the fixing heater temperature detection signal (FSRTH) andoutputs the fixing heater drive signal (FSRD) according to the detected temperature.The fixing heater drive PCB controls the fixing heater according to this signal to keep thefixing heater temperature within the target values.(220-240V model only)FU101RL101+24VFREQSNSFSRD24VOFFFSRTHCPUEngine controllerFixing heater (H1)PressurerollerThermistor (TH1)Thermal fuse (TP1) Fixing filmLow-voltagepower supplyFrequencydetectioncircuitFixing controlRelay drivecircuitFixing heaterdrive circuitFixing heatersafety circuitF-2-31There are 11 types of target fixing temperature depending on the fixing mode.These types are according to the paper type settings and resolution settings on a driver.fixing modeThe number of sheets Normal Heavy1 Heavy2 Light OHT Envelope Envelope2 Quiet1 185 175 185 160 165 165 145 1502 to 6 185 175 185 160 165 165 143 1507 to 26 185 175 185 160 165 165 140 15027 to 41 185 175 185 160 165 165 140 15042 to 76 185 173 185 160 165 165 138 14877 to 150 183 170 185 160 165 165 135 145151 to 197 180 170 185 160 165 165 135 145More than 198 180 170 185 160 165 165 135 145fixing modeThe number of sheets Post NomalN/NNomal(Copy)1 185 185 1902 to 6 185 185 1907 to 26 185 185 19027 to 41 185 185 19042 to 76 185 185 19077 to 150 185 183 188151 to 197 185 180 185More than 198 185 180 185■ Protective Functions● Protective Function of fixing assemblyHost machine carries the following 3 functions to prevent the fixing heater from overheating.1) Protective function by CPUCPU of engine controller monitors the thermistor (TH1) temperature consistently.When TH1 reaches approx 220 deg C, CPU determines that the fixing heater is overheatingand stops the fixing heater drive signal (FSRD) output and also turns OFF relays to shutthe power supply to fixing heater.2) Protection function by fixing heater safety circuitFixing heater safety circuit monitors the thermistor (TH1) temperature consistently.When TH1 reaches approx 235 deg C, it determines that the fixing heater is overheatingand the fixing heater safety circuit turns OFF the relay drive circuit to shut the power supplyT-2-6T-2-7