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Main Unit Theory of Operation Fusing Section
2-111
II Composition/Operation
16.3.11 Heater control
A. Single reference temperature adjustment
• The heater is turned ON or OFF using a target temperature value.
B. Hysteresis temperature adjustment
• The heater is turned ON or OFF with a certain allowance given for the threshold value of
turning ON or OFF the heater.
C. Ripple prediction temperature adjustment
• The heater is turned ON or OFF by determining whether the temperature is on the
increase or decrease within a set temperature range.
16.3.12 PPM control
• When a multi-print cycle is run, the temperature of the Fusing Pressure Roller and the
Fusing Belt decrease, resulting in the fusing performance of the printed image being
degraded.
To prevent this problem, fusing performance is estimated based on the surface tempera-
ture of the Fusing Pressure Roller; the distance between sheets of media is widened
according to the media length and fusing speed, thereby allowing the Fusing Pressure
Roller and the Fusing Belt to recover the required temperature; the fusing performance of
the printed toner image is thus ensured.
• If a multi-print cycle is run using media of a small size, a difference is produced in tem-
perature between the center portion of the roller/belt (the surface over which the media
moves past) and the edges of the roller/belt (where no part of the media moves past).
Since the thermistor is located at the center portion, the machine determines that there
is a drop in roller temperature and turns ON the heater to increase the roller temperature.
This also heats the edges of the roller, at which a high temperature is still maintained.
This increases the overall temperature.
To inhibit this situation, the distance between sheets of media is widened and the tem-
perature of the Fusing Pressure Roller and Fusing Belt is thereby made uniform.
A. Control start timing
• In an ambience of low temperature and low humidity
• In an ambience of high temperature and high humidity
• Media of a small size is detected through media width detection control.
☞ 2-102
• The Heating Roller temperature becomes lower than a predetermined level.
• Media of a small size is detected through media width detection control.
B. Control termination timing
• The control proceeds to “wait control” or “heater OFF control” during the PPM control.
• The media that requires no PPM control is fed through during PPM control.
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