Control unit of induction heating unit, induction heating system, and method of controlling induction heating unit
View Patent ↗A control unit of an induction heating unit controls AC power output to a heating coil of a transverse type induction heating unit that allows an alternating magnetic field to intersect a sheet surface of a conductive sheet that is being conveyed to inductively heat the conductive sheet. The control unit includes: a magnetic energy recovery switch that outputs AC power to the heating coil; a frequency setting unit that sets an output frequency in response to at least one of the relative permeability, resistivity, and sheet thickness of the conductive sheet; and a gate control unit that controls a switching operation of the magnetic energy recovery switch on the basis of the output frequency set by the frequency setting unit.
1. A method of controlling an induction heating unit by controlling an AC power, which is output to a heating coil of a transverse type induction heating unit allowing an alternating magnetic field to intersect a sheet surface of a conductive sheet which is being conveyed to inductively heat the conductive sheet, the method comprising:
outputting the AC power to the heating coil by a magnetic energy recovery switch;
setting an output frequency from a plurality of output frequencies in response to at least one of a relative permeability, a resistivity, and a sheet thickness of the conductive sheet; and
controlling a switching operation of the magnetic energy recovery switch on the basis of the output frequency from the plurality of output frequencies which is set.
2. The method of controlling the induction heating unit according to claim 1 ,
wherein the output frequency is set by acquiring an attribute information which specifies the relative permeability, the resistivity, and the sheet thickness of the conductive sheet, and by selecting a frequency corresponding to the acquired attribute information as the output frequency with reference to a table in which the relative permeability, the resistivity, and the sheet thickness of the conductive sheet, and the frequency are correlated with each other and are registered in advance.
3. The method of controlling the induction heating unit according to claim 1 ,
wherein an AC voltage which is output from the magnetic energy recovery switch is lowered by an output transformer, and the lowered AC voltage is output to the heating coil.
4. The method of controlling the induction heating unit according to claim 1 , the method further comprising:
setting an output current value in response to at least one of the relative permeability, the resistivity, and the sheet thickness of the conductive sheet;
measuring an alternating current which flows to the induction heating unit; and
supplying an DC power, which is necessary for adjusting an alternating current which is measured to the output current value which is set, to the magnetic energy recovery switch.
5. The method of controlling the induction heating unit according to claim 2 ,
wherein an AC voltage which is output from the magnetic energy recovery switch is lowered by an output transformer, and the lowered AC voltage is output to the heating coil.
6. The method of controlling the induction heating unit according to claim 2 , the method further comprising:
setting an output current value in response to at least one of the relative permeability, the resistivity, and the sheet thickness of the conductive sheet;
measuring an alternating current which flows to the induction heating unit; and
supplying an DC power, which is necessary for adjusting an alternating current which is measured to the output current value which is set, to the magnetic energy recovery switch.
7. The method of controlling the induction heating unit according to claim 1 ,
wherein the magnetic energy recovery switch includes,
first and second AC terminals which are connected to one end and the other end of the heating coil, respectively,
first and second DC terminals which are connected to an output terminal of the power supply unit,
a first reverse conductivity type semiconductor switch which is connected between the first AC terminal and the first DC terminal,
a second reverse conductivity type semiconductor switch which is connected between the first AC terminal and the second DC terminal,
a third reverse conductivity type semiconductor switch which is connected between the second AC terminal and the second DC terminal,
a fourth reverse conductivity type semiconductor switch which is connected between the second AC terminal and the first DC terminal, and
a capacitor which is connected between the first and second DC terminals,
the first reverse conductivity type semiconductor switch and the fourth reverse conductivity type semiconductor switch are connected in series in such a manner that conduction directions at the time of a switch-off become opposite to each other,
the second reverse conductivity type semiconductor switch and the third reverse conductivity type semiconductor switch are connected in series in such a manner that conduction directions at the time of the switch-off become opposite to each other,
the first reverse conductivity type semiconductor switch and the third reverse conductivity type semiconductor switch have the same conduction direction at the time of the switch-off as each other,
the second reverse conductivity type semiconductor switch and the fourth reverse conductivity type semiconductor switch have the same conduction direction at the time of the switch-off as each other, and
the AC power is output to the heating coil by controlling a switching operation time of the first and third reverse conductivity type semiconductor switches and a switching operation time of the second and fourth reverse conductivity type semiconductor switches on the basis of the output frequency which is set.
8. The method of controlling the induction heating unit according to claim 4 ,
wherein the output current value is set by acquiring an attribute information which specifies the relative permeability, the resistivity, and the sheet thickness of the conductive sheet, and by selecting a current value corresponding to the acquired attribute information as the output current value with reference to a table in which the relative permeability, the resistivity, and the sheet thickness of the conductive sheet, and the current value are correlated with each other and are registered in advance.
9. The method of controlling the induction heating unit according to claim 2 ,
wherein the magnetic energy recovery switch includes,
first and second AC terminals which are connected to one end and the other end of the heating coil, respectively,
first and second DC terminals which are connected to an output terminal of the power supply unit,
a first reverse conductivity type semiconductor switch which is connected between the first AC terminal and the first DC terminal,
a second reverse conductivity type semiconductor switch which is connected between the first AC terminal and the second DC terminal,
a third reverse conductivity type semiconductor switch which is connected between the second AC terminal and the second DC terminal,
a fourth reverse conductivity type semiconductor switch which is connected between the second AC terminal and the first DC terminal, and
a capacitor which is connected between the first and second DC terminals,
the first reverse conductivity type semiconductor switch and the fourth reverse conductivity type semiconductor switch are connected in series in such a manner that conduction directions at the time of a switch-off become opposite to each other,
the second reverse conductivity type semiconductor switch and the third reverse conductivity type semiconductor switch are connected in series in such a manner that conduction directions at the time of the switch-off become opposite to each other,
the first reverse conductivity type semiconductor switch and the third reverse conductivity type semiconductor switch have the same conduction direction at the time of the switch-off as each other,
the second reverse conductivity type semiconductor switch and the fourth reverse conductivity type semiconductor switch have the same conduction direction at the time of the switch-off as each other, and
the AC power is output to the heating coil by controlling a switching operation time of the first and third reverse conductivity type semiconductor switches and a switching operation time of the second and fourth reverse conductivity type semiconductor switches on the basis of the output frequency which is set.
10. The method of controlling the induction heating unit according to claim 6 ,
wherein the output current value is set by acquiring an attribute information which specifies the relative permeability, the resistivity, and the sheet thickness of the conductive sheet, and by selecting a current value corresponding to the acquired attribute information as the output current value with reference to a table in which the relative permeability, the resistivity, and the sheet thickness of the conductive sheet, and the current value are correlated with each other and are registered in advance.