Induction heating apparatus and induction heating method

1. An induction heating apparatus which continuously heats a steel plate using a solenoid system, the apparatus comprising:

at least three heating coils disposed along a longitudinal direction of the steel plate to make the steel plate pass through an inside thereof; and

inductance adjusters capable of generating self-induction and adjusting self-inductance in the self-induction, wherein said inductance adjusters are disposed on electrical pathways electrically connecting each of said heating coils and a power source which applies a voltage to each of said heating coils, wherein:

each of said heating coils has one inductance adjuster, and

each of said inductance adjusters is disposed to cause a generation of mutual induction at least between said inductance adjusters mutually adjacent to one another.

2. The induction heating apparatus according to claim 1 , wherein

the self-inductance generated by each of said inductance adjusters provided to said heating coil at a first stage and said heating coil at a last stage in the longitudinal direction of the steel plate is adjusted to be smaller than the self-inductance generated by said inductance adjuster for said heating coil disposed between said heating coil at the first stage and said heating coil at the last stage.

3. The induction heating apparatus according to claim 2 , wherein:

a mutual distance of said heating coils mutually adjacent to one another is not less than 1/10 nor more than ⅓ of an inside diameter in a height direction of said heating coil;

each of said inductance adjusters is structured by forming bypassed paths in a direction orthogonal to the electrical pathway; and

a space between said mutually adjacent inductance adjusters is 50 mm to 500 mm.

4. The induction heating apparatus according to claim 3 , wherein

each of said inductance adjusters generates the self-induction by bypassing the electrical pathway on which each of said inductance adjusters is disposed in a substantially coil shape, and adjusts the self-inductance in the self-induction by changing a cross-sectional area of an area surrounded by the substantially coil-shaped bypassed paths being the bypassed electrical pathway.

5. The induction heating apparatus according to claim 4 , wherein:

each of the electrical pathways connecting each of said heating coils and the power source is formed of a pair of input/output terminals longly extended from each of said heating coils; and

said inductance adjuster is formed by bypassing the pair of input/output terminals to make one of the pair of input/output terminals and the other terminal separate from each other, and changes the cross-sectional area of the area surrounded by the bypassed paths by changing a distance between the one of the pair of input/output terminals and the other terminal in the bypassed paths.

6. The induction heating apparatus according to claim 5 , wherein

a space between each of said heating coils and each of said inductance adjusters connected to each of said heating coils is 500 mm to 2000 mm.

7. The induction heating apparatus according to claim 6 , wherein

each of said heating coils is a single-turn coil or a double-turn coil.

8. An induction heating method for continuously heating a steel plate using a solenoid system, the method comprising:

disposing at least three heating coils along a longitudinal direction of the steel plate to make the steel plate pass through an inside of the coils;

disposing inductance adjusters capable of generating self-induction and adjusting self-inductance in the self-induction on electrical pathways electrically connecting each of the heating coils and a power source applying a voltage to each of the heating coils, with respect to the respective heating coils, to cause a generation of mutual induction at least between the inductance adjusters mutually adjacent to one another; and

adjusting the self-inductance generated by each of the inductance adjusters provided to the heating coil at a first stage and the heating coil at a last stage in the longitudinal direction of the steel plate to be smaller than the self-inductance generated by the inductance adjuster for the heating coil disposed between the heating coil at the first stage and the heating coil at the last stage.

9. The induction heating method according to claim 8 , wherein:

a mutual distance of the heating coils mutually adjacent to one another is not less than 1/10 nor more than ⅓ of an inside diameter in a height direction of the heating coil;

each of the inductance adjusters is structured by forming bypassed paths in a direction orthogonal to the electrical pathway; and

a space between the mutually adjacent inductance adjusters is 50 mm to 500 mm.

10. The induction heating method according to claim 9 , wherein

each of the inductance adjusters generates the self-induction by bypassing the electrical pathway on which each of the inductance adjusters is disposed in a substantially coil shape, and adjusts the self-inductance in the self-induction by changing a cross-sectional area of an area surrounded by the substantially coil-shaped bypassed paths being the bypassed electrical pathway.

11. The induction heating method according to claim 10 , wherein:

each of the electrical pathways connecting each of the heating coils and the power source is formed of a pair of input/output terminals longly extended from each of the heating coils; and

the inductance adjuster is formed by bypassing the pair of input/output terminals to make one of the pair of input/output terminals and the other terminal separate from each other, and changes the cross-sectional area of the area surrounded by the bypassed paths by changing a distance between the one of the pair of input/output terminals and the other terminal in the bypassed paths.

12. The induction heating method according to claim 11 , wherein

a space between each of the heating coils and each of the inductance adjusters connected to each of the heating coils is 500 mm to 2000 mm.

13. The induction heating method according to claim 12 , wherein

each of the heating coils is a single-turn coil or a double-turn coil.