Canon MF4690 Service Manual - Page 87
Specification/Control/Function List, 1.2 Overview
UPC - 013803076820
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8.1 Overview/Configuration 8.1.1 Specification/Control/Function List Item Fixing method Fixing heater Fixing temperature detection Fixing temperature control Protection function T-8-1 Function/Method On-demand fixing Flat heater Thermistor (TH1): temperature control, detection of abnormality Temperature fuse (TP1): detection of abnormality Temperature control at startup Temperature control at normal times Temperature control at sheet-to-sheet interval Temperature error detection with the thermistor Temperature rise detection with the temperature fuse Chapter 8 0016-1857 8.1.2 Overview 0016-1858 The fixing unit employees the on-demand fixing method, and it is composed of fixing film unit, in which the fixing heater, thermistor, and temperature fuse are incorporated, and the pressure roller. The pressure roller and the delivery roller are driven with the main motor (M1). A paper separated from the photosensitive drum is fed to inside of the fixing assembly, and the toner is fixed on a paper with the fixing film and the pressure roller. A paper being fixed is detected with the delivery sensor (PS803); then, delivered to outside of the machine via the delivery roller. F-8-1 [1] Pressure roller [2] Fixing film [3] Delivery roller H1: Fixing heater PS803: Delivery sensor The fixing heater is the heater (ceramic heater) that the heating pattern is deposited on the ceramic plate. By heating the fixing film with the fixing heater, it gives heat to passing papers. The thermistor (TH1) locates at the center of the fixing heater (H1), and detects the temperature of the heater. The temperature fuse (TP1) locates at the top center of the fixing heater. If the temperature of the fixing heater increases abnormally, it blocks power supply to the heater by meltdown. The temperature control of the fixing assembly composed of the foregoing components is executed at the fixing control circuit on the DCNT board with the instruction of the CPU (IC902). There are the fixing heater drive circuit and the fixing heater safety circuit in the fixing control circuit. 8-1