Canon i-SENSYS LBP5300 Series Service Manual

Also see for i-SENSYS LBP5300 Series: User guide User guide

Contents

Chapter 22-35Each temperature control circuit and function of the fixing unit is described in the following pages.2.6.2 Various Control Mechanisms2.6.2.1 Fixing Temperature Control2.6.2.1.1 Heater temperature control0013-8368/ i-SENSYS LBP5360 / i-SENSYS LBP5300The heater temperature control is to sense the surface temperature of the fixing sleeve and the fixing heater, and to control the DRIVE signals of the fixing heaterin order to maintain the temperature at targeted temperature.The control circuit is illustrated below.F-2-46The fixing heater temperature is monitored by two thermistors, the main thermistor (TH1) and the sub thermistor (TH2).The TH1 is for the print temperature control and the between-sheets temperature control.The TH2 is for the initial rotation temperature control, for the start-up temperature control, and for detecting abnormal temperature rise at both ends of fixing heater.The CPU (IC1001) in the DC controller monitors the input voltage of the FIXING HEATER TEMPERATURE signals (FSRTH1, FSRTH2), and outputs the FIX-ING HEATER DRIVE signal (FSRD) based on the voltage value. The fixing heater control circuit controls the fixing temperature so that the heater can be main-tained at the targeted temperature.This fixing temperature control is divided into the following six fixing sequences.1) Initial rotation temperature controlThis control is to melt the grease, inside the fixing sleeve and to lubricate the sleeve, as soon as the power is turned ON. This prevents the fixing sleeve damage.The CPU temporarily turns ON the fixing heater for short time period just before the fixing motor starts, then it drives the fixing motor.2) Stand-by temperature controlThis control is to shorten the print operation time from the STBY period until print completion The CPU controls the fixing heater to maintain the temperatureat 115 deg C to 120 deg C. This control can be canceled according to the command to the CPU from the video controller.3) Start-up temperature controlThis control is to determine the start-up power providing to the fixing heater according to the temperature detected by the sub thermistor at heater energization.The start-up temperature varies depending on the elapsed time since previous print completion, paper types, and environment.4) Print temperature controlThis control is to maintain the temperature of the fixing sleeve at its targeted temperature during print operation.The CPU gradually switches the target temperature in one printing process depending on the number of print.The targeted temperature varies depending on the paper types.5) Between-sheets temperature controlThis control is to maintain the temperature of fixing heater below its normally targeted temperature during continuous printing in order to prevent the excessivetemperature rise of the fixing pressure roller at uncovering paper portion of between-sheets with low-speed mode.The targeted temperature varies according to the between-sheets intervals and the paper types.6) Throughput down controlThis control is to prevent an overheating at both ends of the fixing heater during continuous printing with smaller than A4 size paper.If the paper width specified by the video controller is narrower than 210mm (A4 size) and detected temperature by the sub thermistor exceeds the specifiedtemperature during continuous printing, the CPU makes the between-sheets interval longer to slow down the printing speed.If the sub-thermistor detects the temperatures shown in the table below while small size paper is being fed, an additional (1st) interval is added to the defaultpickup interval, according to the detected temperature, in order to lower the throughput. If, after having added the 1st additional interval, the sub-thermistoragain detects temperature of 250 deg C or higher and there is no change in the paper interval after five sheets, an additional (2nd) interval is added, accordingto the detected temperature in order to lower the throughput further. The 3rd and 4th intervals are added similarly.T-2-5Sub-thermistor temperature Additional intervals1st 2nd 3rd 4thFixing heater (H1)Fixing sleeveunitMain thermistor(TH1)Fixing heatersafety circuitIC1001CPUDC controller PCBSub thermistor(TH2)FSRD1FSRTH1FSRTH2FLD+RLD-ZEROXFixing heaterdrive circuitRelay drivecircuitZero crossingcurcuitRLD+Thermoswitch (TP)Fixing unit Low-voltage powersupply unit