Ricoh CH-C1, Service Training

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489
Ch-C1 Training
Slide 489
IH Operation

When high frequency current runs through the coil, a
magnetic flux occurs.

At this time, eddy currents occur in the copper-coated
layer of the heating roller, and as a result of Joule heating,
the heating roller temperature rises.
IH Coil
Magnetic
Flux
Eddy
Currents

Joule heating: Heating of a conductor when a current flows through it; also
called and resistive heating.

The surface of the heating roller is made of a magnetic shunt alloy which is
coated with copper.

The copper coating layer heats as a result of Joule heating, while the
magnetic shunt alloy forms a magnetic circuit.

The magnetic flux which comes through from the magnetic shunt alloy
reaches the low-resistance aluminum shield, and then eddy currents occur
and energy is consumed.

A magnetic shunt alloy drastically changes its magnetic character when its
temperature approaches the Curie temperature.

After the temperature is higher than the Curie temperature, the alloy loses
its magnetic character and lets flux pass through it, in which the copper
coated layer is not heated.

Using a heating roller made of a magnetic shunt alloy whose Curie
temperature is only a few tens of degrees C higher than that of the fusing
limit, contributes to stopping overheating at the ends of the rollers (not
where the paper passes) in serial printing.