e-STUDIO520/600/720/850 FUSER UNIT March 2005 © TOSHIBA TEC
14 - 6
14.4.2 Heating principle of IH coil
The magnetic field is generated by applying a high frequency current to the IH coil inside the fuser
roller, which then produces the eddy current in it. When the eddy current flows, the Joule heat is gener-
ated by the resistance element of the fuser roller, which is then heated. In the IH coil method, the ther-
mal efficiency is higher than the lamp method because the fuser roller is directly heated.
IH coil is divided into two parts to decrease the temperature difference between the center and both
ends of the fuser roller.
Image of current flowing from A to B
Fig.14-3
Block diagram of IH board
Fig.14-4
Current flowing on the surface of the fuser roller
Current flowing inside the fuser rollerEddy currentHigh frequency
magnetic field
Side IH coil
Center IH coil
High frequency
power source
B
A
C2
D1
T1
C1
C31
CPU
Input
voltage
I/F circuit for LGC board
Monitoring input current
Input current
Monitoring input voltage
Control circuit for high frequency current
Ripple filter circuit
Q11
(
IGBT
)
Fuser roller
IGBT
driver
Q1
IGBT
driver
Photocoupler
IH coil
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