Inductive heating apparatus

1. An induction cooking device comprising:

a top plate on which a cooking container is placed,

a heating coil, the outer circumference of which is nearly circular, for generating an induction magnetic field for heating the cooking container,

a heating control unit for controlling a heating power of the cooking container by controlling a high-frequency current to be supplied to the heating coil,

an electrode disposed in a lower surface of the top plate, and

an electrostatic capacity detector for detecting changes in electrostatic capacity occurring in the electrode when articles to be cooked contact with the top plate,

wherein when the electrostatic capacity detector senses changes in the electrostatic capacity of the electrode, the heating control unit decreases or stops the heating power of the cooking container, and

the electrode having an arc shape and being concentrically disposed outside of the outer circumference of the heating coil and along the edge of the heating coil.

2. The induction cooking device according to claim 1 , wherein as to the electrode, a length in the radial direction is shorter than a length in the arc direction.

3. The induction cooking device according to claim 1 , wherein the electrode is a plurality of electrodes having a same area, and the length of a wiring connecting between the electrodes and the electrostatic capacity detector equalizes an electrostatic capacity of the plurality of electrodes.

4. The induction cooking device according to claim 1 , wherein the electrode is formed by printing a conductive material on the top plate.

5. The induction cooking device according to claim 1 , wherein wiring for connecting between the electrode and the electrostatic capacity detector is formed by printing a conductive material on the top plate.

6. The induction cooking device according to claim 1 , wherein the electrode is electrode is provided in a plurality, and metal parts are also disposed near the plurality of electrodes.

7. The induction cooking device according to claim 6 , wherein a distance between the metal parts and the electrode is equal.

8. The induction cooking device according to claim 6 , wherein the metal parts are connected to a specified potential same as in the heating control unit or the electrostatic capacity detector.

9. The induction cooking device according to claim 1 , wherein the heating coil comprises a plurality of heating coils, and the electrode is disposed among the plurality of heating coils.

10. The induction cooking device according to claim 1 , wherein both the electrode and the heating coil are provided in a plurality, and each electrode is disposed among the plurality of heating coils.

11. The induction cooking device according to claim 1 , wherein the heating coil comprises a plurality of heating coils are provided, and the electrode is disposed nearly in the center of the plurality of heating coils.

12. The induction cooking device according to claim 1 , further comprising an operation unit to be manipulated by the user for indicating a heating state, wherein the electrode is disposed between the center of the heating coil and the operation unit.

13. The induction cooking device according to claim 1 , wherein the electrode comprises a plurality of electrodes, and the heating control unit decreases or stops the heating power of the cooking container only when the electrostatic capacity detector first detects a change in electrostatic capacity in a first electrode closer to the center of the heating coil, and then detects a change in electrostatic capacity in a second electrode positioned further from the center of the heating coil than the first electrode.

14. The induction cooking device according to claim 13 , wherein the electrode comprises a plurality of electrodes, and the heating control unit decreases or stops the heating power of the cooking container only when the electrostatic capacity detector detects a change in electrostatic capacity in a first electrode closer to the center of the heating coil, and then detects, within a prescribed time, a change in electrostatic capacity in a second electrode positioned further from the center of the heating coil than the first electrode.

15. The induction cooking device according to claim 1 , wherein the electrode comprises a plurality of electrodes, and the heating control unit decreases or stops the heating power of the cooking container only when the electrostatic capacity detector detects a change in electrostatic capacity in the electrodes.

16. The induction cooking device according to claim 1 , wherein the electrode having the arc shape is entirely disposed outside of the outer circumference of the heating coil and along the edge of the heating coil.

17. The induction cooking device according to claim 1 , wherein the arc shape is aligned in a same plane with the heating coil to circumferentially border a periphery of the edge of the heating coil.

18. An induction cooking device comprising:

a top plate formed to receive a cooking container on a first surface of the top plate;

a heating coil adjacent a second surface of the top plate opposite the first surface, the heating coil having a nearly circular outer circumference and formed to generate an induction magnetic field to heat the cooking container,

an electrode disposed adjacent the second surface and entirely outside the outer circumference of the heating coil, the electrode formed as an arc shape to circumferentially border at least part of the outer circumference of the heating coil; and

an electrostatic capacity detector operable to sense changes in electrostatic capacity of the electrode when articles to be cooked contact the first surface of the top plate.

19. The induction cooking device according to claim 18 , wherein the electrode is positioned to concentrically align the arc shape with the nearly circular outer circumference of the heating coil.