Phaser 6280 Color Laser Printer Service Manual 2-57Theory of OperationFuser ControlFuser Temperature ControlAfter the target temperature is set, the Heat Roll surface temperature iscontrolled so at that it can be the target temperature by turning the HeaterLamp On/Off.Temperature of individual area of the Heat Roll is detected by the Fuser Non-Contact Sensor (NCS) in the middle of the Heat Roll and the Temp Sensor atthe edge of it. When the temperature is detected higher than the target, theHeater Lamp will turn Off. When the temperature is lower than the target, theHeater Lamp will turn On.The target temperature set up varies depending on the time of Warm-up,Printing, or Process Control. The target temperature will be changed basedon the interior temperature detected by the Humidity Sensor, the difference ofthe temperature between the center and edge areas of the Heat Roll, PrintingMode, or the Input Power Voltage.Cool DownAs printing continues, the distribution of temperature in the Heat Rollbecomes uneven in both the paper feed and non-paper feed areas. CoolingDown process is to provide a certain period of time without feeding paper sothat the Heat Roll temperature can be distributed evenly.When the edge of Heat Roll temperature is high, cooling down is performed tolower the temperature to the target temperature.Sensor Warm-UpThe Fuser Non-Contact Sensor at the center of the Heat Roll will lose itsaccuracy of detecting temperature when the temperature of the Sensor itselfis below -5° C. Therefore, the Sensor will be warmed up when the temperatureis below -5° C. This process is called Sensor Warm-Up.
