Fuser Control - Minolta Magicolor 3100 Series Service Manual

7.8 Fuser Control

7.8.1 Fuser temperature control
As for the fuser temperature control, the target temperature is set, then the Heat Roll surface temperature
is controlled so as to be the target temperature by turning on/off the Heater Lamp.
The Heat Roll surface temperature is detected by the Temp Sensor. The Temp Sensor detects the
temperature and the resistance value for disconnection sensing alternately at 40ms cycles. That is, the
temperature is detected at 80ms cycles, and if the detection result is higher than target value, the Heater
Lamp is turned off, or if lower, the Heater Lamp is turned on.
For the target temperature, different temperature is set respectively at the time of standby, printing, and
process control. Also, target temperature is changed according to the inside temperature detected with the
SENSOR HUM TEMP, print count, print mode, and input power supply voltage.
7.8.2 Cool down
As the printing continues, the temperature distribution of the Heat Roll becomes uneven between paper
path and non-paper path. To make the Heat Roll temperature as even as possible, the waiting time is
provided, during which the Heater Lamp is not turned on. This is called the cool down.
The cool down is executed for the duration of certain time according to the number of sheets continuously
printed, when the set printing with certain type and size of paper completed.
Also, when the paper type or size was changed, the cool down is inserted even in the midway of several
hundred sheets of printing.
As a simple cool down, the PPM down is provided. This function idles the fuser without feeding the sheets
during the printing to improve uneven temperature distribution of the Heat Roll.
In printing certain type/size of paper continuously, the page interval is increased from the specified print
counts and the prints per minute are reduced, and thus it is called PPM down.
The PPM execution timing is determined depending on the paper size and type.
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