Konica Minolta bizhub C658 Service Manual page 1885

bizhub C658/C558/C458/C368/C308/C258
[5] Fusing pressure home sensor (PS38)
[7] Cam shaft
14.3 Operation
14.3.1 Heating roller assy heating control
(1) Heating control
• The heating roller assy consists of the fusing belt (cylindrical shape) into which the fusing roller is inserted.
• The inside surface of the fusing belt is formed with Ni layer and Cu layer.
• The IH coil unit located beside the heating roller assy radiates magnetic flux to the fusing belt when energized.
• The IH coil unit consists of two different types of coil: main coil and demagnetization coil.
• The fusing belt is heated by the main coil. The demagnetization coil controls the heating zone.
• Ni layer and Cu layer of the fusing belt is the conducting layer in which eddy current is generated with magnetic flux. The eddy current
generated in the conducting layer produces Joule heat to heat the heating roller.
• The main coil is provided only on one side of the heating roller assy, so that the heating roller generates heat from a local surface of the
fusing belt close to the main coil. The heating roller assy is therefore rotated to ensure that the entire periphery of the roller is heated to
an adequate temperature.
• The heating roller temperature sensor and heating roller thermistor1 to 3 measure the temperature of the fusing belt.
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[3]
[1]
[2]
[1] Heating roller assy
[3] Ni layer and Cu layer (coated back side)
[5] Demagnetization coil
[7] IH coil unit
(2) Whole area heating control
• During printing, the whole area of the fusing belt is heated by the main coil.
(3) Center heating switch control
• The temperature on ends of the fusing belt is measured with the heating roller thermistor1.
• When the temperature of ends of the fusing belt exceeds a predetermined value during printing using paper of a small size or in the
standby state, the demagnetization coil comes into play in inhibiting heating of roller ends and only the center portion of the roller is
heated.
• When the demagnetization coil is energized, the magnetic flux from the main coil is cancelled by the repulsive magnetic flux induced from
the demagnetization coil. When the magnetic flux at the ends of the roller is canceled, heating of the ends of the roller can be controlled.
• The IH coil unit is provided with one type of demagnetization coil.
• The ON/OFF control of the demagnetization coil is performed depending on the paper width (CD: main scanning length), the temperature
on sides of the fusing belt, and the type of paper to be fed.
[1]
[1] Demagnetization coil
(4) Detection of rotation of the heating roller assy
• The heating roller assy is rotated while it is being heated to ensure that the entire periphery of the fusing belt reaches an adequate
temperature.
• If the heating roller assy does not rotate while the IH coil unit (main coil) is energized, the temperature of the entire periphery of the fusing
belt cannot be measured and thus proper temperature control cannot be provided. At this time, only the half surface of the fusing belt is
heated. If the main coil is energized with the heating roller assy remaining stationary, the roller can be damaged.
O THEORY OF OPERATION bizhub C658/C558/C458/C368/C308/C258 > 14.
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O-110
FUSING SECTION (bizhub C658/C558)
Pressure cam
Fusing pressure motor (M11)
[1]
Fusing roller
Fusing belt
Main coil
Fusing unit
Main coil