Induction heating device and induction heating method
A first coil 110 and a second coil 120 are faced each other across a conductor plate S so that the first coil ( 110 ) and the second coil ( 120 ) become substantially the same in position in a Y-axis direction. The conductor plate S is inductively heated by applying alternating currents at a frequency at which a depth of penetration of the current becomes equal to or less than half a plate thickness of the conductor plate S to the first coil ( 110 ) and the second coil ( 120 ) in opposite directions.
1. An induction heating device being an induction heating device that inductively heats a passing conductor plate, the induction heating device comprising:
a first coil that generates a magnetic field in a plate thickness direction of the conductor plate by an alternating current flowing therethrough; and
a second coil that generates a magnetic field in the plate thickness direction of the conductor plate by an alternating current flowing therethrough, wherein
the first coil and the second coil are positioned to sandwich the conductor plate therebetween,
the first coil and the second coil are substantially the same in position in a passing direction of the conductor plate,
magnetic fields that are opposite to each other in direction are generated in the plate thickness direction of the conductor plate from the first coil and the second coil by the alternating currents,
eddy currents are generated inside the conductor plate by the magnetic fields that are opposite to each other in the plate thickness direction of the conductor plate, and
the conductor plate is inductively heated by the eddy currents.
2. The induction heating device according to claim 1 , wherein
as the alternating currents, alternating currents at a frequency f in a range where (A) Expression below is satisfied are applied to the first coil and the second coil, and thereby the magnetic fields that are opposite to each other in direction are generated in the plate thickness direction of the conductor plate from the first coil and the second coil,
In (A) Expression, d is a plate thickness [m] of the conductor plate,
In (A) Expression, δ is a depth of penetration of the current in the conductor plate and is expressed by (B) Expression below,
In (B) Expression, ρ is resistivity [Ω·m] of the conductor plate, f is the frequency [Hz] of the alternating currents, and μ s is relative permeability of the conductor plate,
[
Mathematical
expression
1
]
δ
≦
d
(
A
)
δ
=
503
ρ
μ
s
f
.
(
B
)
3. The induction heating device according to claim 2 , wherein
the number of turns of the first coil and the number of turns of the second coil are the same.
4. The induction heating device according to claim 2 , further comprising:
a first core that is arranged at a position to be a magnetic path of magnetic fluxes generated from the first coil and is intended for generating a magnetic field between the first core and the conductor plate; and
a second core that is arranged at a position to be a magnetic path of magnetic fluxes generated from the second coil and is intended for generating a magnetic field between the second core and the conductor plate, wherein
by the alternating currents, magnetic fields that are opposite to each other in direction are generated in the plate thickness direction of the conductor plate between the first core and the conductor plate and between the second core and the conductor plate, and by the magnetic fields opposite to each other in the plate thickness direction of the conductor plate, eddy currents opposite to each other in direction are generated inside the conductor plate.
5. The induction heating device according to claim 2 , wherein
by the magnetic fields opposite to each other in the plate thickness direction of the conductor plate, eddy currents opposite to each other in direction are generated in two regions with a distance therebetween in the passing direction of the conductor plate, the two regions being regions vertical to the passing direction of the conductor plate inside the conductor plate, without generating an eddy current along the passing direction of the conductor plate in width-direction end portions of the conductor plate.
6. The induction heating device according to claim 2 , wherein
each of the eddy currents forms one closed loop passing through region on a first surface side of the conductor plate and region on a second surface side of the conductor plate sandwiching center in plate thickness direction of the conductor plate.
7. The induction heating device according to claim 1 , wherein
the number of turns of the first coil and the number of turns of the second coil are the same.
8. The induction heating device according to claim 7 , further comprising:
a first core that is arranged at a position to be a magnetic path of magnetic fluxes generated from the first coil and is intended for generating a magnetic field between the first core and the conductor plate; and
a second core that is arranged at a position to be a magnetic path of magnetic fluxes generated from the second coil and is intended for generating a magnetic field between the second core and the conductor plate, wherein
by the alternating currents, magnetic fields that are opposite to each other in direction are generated in the plate thickness direction of the conductor plate between the first core and the conductor plate and between the second core and the conductor plate, and by the magnetic fields opposite to each other in the plate thickness direction of the conductor plate, eddy currents opposite to each other in direction are generated inside the conductor plate.
9. The induction heating device according to claim 7 , wherein
by the magnetic fields opposite to each other in the plate thickness direction of the conductor plate, eddy currents opposite to each other in direction are generated in two regions with a distance therebetween in the passing direction of the conductor plate, the two regions being regions vertical to the passing direction of the conductor plate inside the conductor plate, without generating an eddy current along the passing direction of the conductor plate in width-direction end portions of the conductor plate.
10. The induction heating device according to claim 7 , wherein
each of the eddy currents forms one closed loop passing through region on a first surface side of the conductor plate and region on a second surface side of the conductor plate sandwiching center in plate thickness direction of the conductor plate.
11. The induction heating device according to claim 1 , further comprising:
a first core that is arranged at a position to be a magnetic path of magnetic fluxes generated from the first coil and is intended for generating a magnetic field between the first core and the conductor plate; and
a second core that is arranged at a position to be a magnetic path of magnetic fluxes generated from the second coil and is intended for generating a magnetic field between the second core and the conductor plate, wherein
by the alternating currents, magnetic fields that are opposite to each other in direction are generated in the plate thickness direction of the conductor plate between the first core and the conductor plate and between the second core and the conductor plate, and by the magnetic fields opposite to each other in the plate thickness direction of the conductor plate, eddy currents opposite to each other in direction are generated inside the conductor plate.
12. The induction heating device according to claim 11 , wherein
by the magnetic fields opposite to each other in the plate thickness direction of the conductor plate, eddy currents opposite to each other in direction are generated in two regions with a distance therebetween in the passing direction of the conductor plate, the two regions being regions vertical to the passing direction of the conductor plate inside the conductor plate, without generating an eddy current along the passing direction of the conductor plate in width-direction end portions of the conductor plate.
13. The induction heating device according to claim 11 , wherein
each of the eddy currents forms one closed loop passing through region on a first surface side of the conductor plate and region on a second surface side of the conductor plate sandwiching center in plate thickness direction of the conductor plate.
14. The induction heating device according to claim 1 , wherein
by the magnetic fields opposite to each other in the plate thickness direction of the conductor plate, eddy currents opposite to each other in direction are generated in two regions with a distance therebetween in the passing direction of the conductor plate, the two regions being regions vertical to the passing direction of the conductor plate inside the conductor plate, without generating an eddy current along the passing direction of the conductor plate in width-direction end portions of the conductor plate.
15. The induction heating device according to claim 1 , wherein
each of the eddy currents forms one closed loop passing through region on a first surface side of the conductor plate and region on a second surface side of the conductor plate sandwiching center in plate thickness direction of the conductor plate.
16. An induction heating method being an induction heating method to, by using an induction heating device including:
a first coil that generates a magnetic field in a plate thickness direction of a conductor plate by an alternating current flowing therethrough; and
a second coil that generates a magnetic field in the plate thickness direction of the conductor plate by an alternating current flowing therethrough, in which
the first coil and the second coil are positioned to sandwich the conductor plate therebetween, and
the first coil and the second coil are substantially the same in position in a passing direction of the conductor plate, inductively heat the passing conductor plate, the method comprising:
generating magnetic fields that are opposite to each other in direction in the plate thickness direction of the conductor plate from the first coil and the second coil by the alternating currents;
generating eddy currents inside the conductor plate by the magnetic fields opposite to each other in the plate thickness direction of the conductor plate; and
inductively heating the conductor plate by the eddy currents.