Sharp FO 4400 Service Manual - Page 58

FO-4400U FO-CS1 10. IMAGE TRANSFER 10-1. Overview · Image transfer is the process of transferring the toner image created on the PC Drum in the developing process to paper. · Roller image transfer is used instead of corona image transfer as the image transfer method. · In roller image transfer, there is little generation of ozone due to corona discharge. Also, there is no blur of toner because the paper is always pressed by the PC Drum and the Image Transfer Roller. · When cleaning the Image Transfer Roller and before printing, reverse bias is applied. · The residual electric potential on the paper is dissipated via a dis- charge needle. PC Drum PC Drum Paper Image Transfer Roller Paper Discharge Needle Image Transfer Roller Reverse Bias Image Transfer Bias Fig. 9 11. FUSING 11-1. Overview · The toner image transferred onto the paper is securely fixed to the paper. · A heat roller system is used as the fusing system. The toner image is fused by the Heat Roller heated by the Heater Lamp (H1), and securely fixed by the pressure between the Heat Roller and Backup Roller. Paper Paper Separator Thermostat (TS1) Thermistor (TH1) Backup Roller Heater Lamp (H1) Heat Roller Fusing Entrance Guide 11-2. Fusing Temperature Control Circuit · The Thermistor (TH1) detects the surface temperature of the Heat Roller and inputs that analog voltage into IC4-78. Corresponding to this data, the Heater Lamp (H1) ON/OFF signal is output from IC4-55, causing the Heater Lamp (H1) to turn ON or OFF to control the fusing temperature. · When the Heater Lamp (H1) is not turned OFF even if the Thermistor (TH1) detects a high temperature malfunction (if the surface temperature of the Heat Roller exceeds 230°C), the signal from IC4-79 changes from L to H to turn OFF the Heater Lamp (H1) forcibly. Thermistor TH1 11 22 Heater Lamp H1 Thermostat TS1 Power Supply PWB CN2 1 2 3 HEAT_N N.C. HEAT_L +24VMAIN GND(MG) GND(DG) GND(DG) +5VMAIN +5VSUB HEATER ON HEATER-RELAY OFF CN1 1 2 3 4 5 6 7 8 L H1: ON H H1: OFF Printer PWB (PWB-A) CN2 1 2 DC5V CN7 1 2 3 4 5 6 L 7 8 Q103 GND GND IC3 H1 3L 2L 78 CMPIN/AN8/P63 IC4 79 CMPOUT 55 P01 DC5V GND Fig. 11 (At 600 dpi) The printer is initialized upon power supply. The Heater Lamp then turns on and the printer starts warming up. The temperature is controlled as follows. Mode 1: The temperature is controlled to maintain 125°C during standby and 210°C during printing. If this mode continues for 300 seconds, the control will shift to mode 2. Mode 2: The temperature of the Heat Roller falls gradually to about 190°C from about 210°C. If this mode continues for 208 seconds, the control will shift to mode 3. Mode 3: The temperature is controlled to maintain 125°C during standby and 190°C during printing. Unless an error occurs or the control is opened, this mode is maintained. Warming-up Thermistor detecting temperature 210°C 190°C 160°C 155°C Printing (600 dpi) Printing (1200 dpi) Temperature (°C) 125°C Standby Mode 1: 300sec Mode 2: 208sec Fig. 12 Mode 3 Temperature immediately after temperature control start The state before Less than 50°C 50°C or more, discontinuation of less than 125°C temperature control Mode 1, warming-up Mode 1 Mode 2, 3 or Power OFF Mode 1 Mode 2 125°C or more, Mode 3 Fig. 10 3 - 6