Inductive heating device

1. An inductive heating device comprising:

a coil unit including a heating coil for heating a to-be-heated object, a plurality of ferrites placed under the heating coil in a vertical direction, and a coil base having plural housing holes which house the plural ferrites respectively; and

a heat dissipation plate for directly placing the coil unit thereon, wherein:

the coil unit comprises an electrical insulating member which is arranged between the heating coil and the ferrites to provide electrical insulation therebetween, and a heat conductive member is embedded in an area between the heating coil and the electrical insulating member and an area between the electrical insulating member and the ferrites, and wherein

lower surfaces of the plural ferrites housed in the housing holes in the coil base are arranged to be flushed with a flat surface of a lower surface of the coil base, and

the lower surfaces of the plural ferrites and the flat surface of the coil base are in a surface-to-surface contact with a flat surface of the heat dissipation plate which constitutes an upper surface of the heat dissipation plate;

wherein the housing holes are provided with a positioning protrusion which is protruded from their edge portions, and the lower surfaces of the plural ferrites housed in the housing holes are placed directly on the positioning protrusions, such that the lower surfaces of the plural ferrites housed in the housing holes in the coil base are flushed with the flat surface of the lower surface of the coil base.

2. The inductive heating device according to claim 1 , wherein

the flat surface of the heat dissipation plate is formed to be larger than a profile area in a vertical direction of the coil unit and is adapted to be exposed, at an outer peripheral portion, outside the coil unit.

3. The inductive heating device according to claim 1 , further comprising a fixing member for mechanically securing the coil base and the heat dissipation plate, under the heating coil in the vertical direction.

4. The inductive heating device according to claim 1 , wherein

the coil base is provided with plural hooks protruded from its lower surface in the vertical direction, and the plural hooks are adapted to penetrate through plural holes formed in the heat dissipation plate and engage with portions of the heat dissipation plate.

5. The inductive heating device according to claim 1 , wherein

the electrical insulating member is an adhesive agent having an electrical insulating property, the heat conductive member is a mica plate, and the heating coil and the coil base are directly secured to each other through the adhesive agent charged in through holes formed in the mica plate.

6. The inductive heating device according to claim 1 , wherein

the heat dissipation plate is adapted to be cooled by cooling air from a blower, such that the cooling air is caused to come into contact with only the lower surface of the heat dissipation plate in the vertical direction.

7. The inductive heating device according to claim 1 , wherein

there is placed a control circuit for controlling an output of the heating coil in an area under the heat dissipation plate in the vertical direction, and

cooling air from the blower is brought into contact with heat generating components in the control circuit and the lower surface of the heat dissipation plate in the vertical direction, for cooling the heat generating components and the heat dissipation plate.

8. The inductive heating device according to claim 1 , wherein

the heat dissipation plate is formed such that the vertically-projected area of its flat surface is larger than the vertically-projected area of the heating coil, and the flat surface of the heat dissipation plate is placed in an area outside an outer periphery of the heating coil.

9. The inductive heating device according to claim 1 , wherein

the heat dissipation plate is provided with a concavity and convexity in its portion which is not in contact with the coil unit.

10. The inductive heating device according to claim 3 , wherein

the heating coil comprises plural substantially-concentric induction heating coils, and

there is provided the fixing member for mechanically securing the heat dissipation plate and the coil base which are placed under the heating coil in the vertical direction, at a position under a substantially-midway point on a radial width of each induction heating coil.

11. The inductive heating device according to claim 3 , wherein

there are provided a plurality of the fixing members, and

the distances between the respective fixing members are substantially equal distances in a circumferential direction of the heating coil.

12. The inductive heating device according to claim 3 , wherein

there are provided a plurality of the fixing members, and the fixing members are placed along plural concentric circles, such that the number of the fixing members along the concentric circle in an outer-periphery side is larger than that along the concentric circle in an inner-periphery side.

13. The inductive heating device according to claim 4 , wherein

the plural hooks, and the portions of the heat dissipation plate which engage with the plural hooks are placed under the heating coil in the vertical direction.

14. The inductive heating device according to claim 4 , wherein

the plural hooks are placed along concentric circles in the lower surface of the coil base, at substantially even intervals in the circumferential direction.

15. The inductive heating device according to claim 4 , wherein

the plural hooks are placed along plural concentric circles in the lower surface of the coil base, such that the number of the hooks placed along the concentric circle in the outer periphery side is larger than that along the concentric circle in the inner periphery side, in the coil base.

16. The inductive heating device according to claim 4 , wherein

the plural hooks have respective protruding portions protruded from the lower surface of the coil base, the protruding portions are protruded in the same direction in a plane parallel to the lower surface of the coil base, there is provided a gap between the protruding portions and the lower surface of the coil base, such that the gap is set to be equal to or slightly smaller than a thickness of the heat dissipation plate,

the heat dissipation plate is press-fitted, at its portions, into the gap between the lower surface of the coil base and the protruding portions of the hooks to be secured thereto, by penetrating the hooks through the holes formed in the heat dissipation plate, and sliding the heat dissipation plate in a direction opposite from the direction of the protrusion of the hooks.

17. The inductive heating device according to claim 16 , wherein

the coil base and the heat dissipation plate are secured to each other through a fixing member, after the portions of the heat dissipation plate are press-fitted into the gap between the lower surface of the coil base and the protruding portions of the hooks to be secured thereto.

18. The inductive heating device according to claim 1 , wherein

the heat dissipation plate on which the coil unit is placed is adapted to define only an area thereunder in the vertical direction as a cooling space for passing, therethrough, cooling air from a blower, such that cooling air from the blower directly cools the heat dissipation plate only at is lower surface in the vertical direction, together with heat generating components in a control device placed in the cooling space, and heat from the heating coil is cooled through the heat dissipation plate.