CROSS REFERENCE TO RELATED APPLICATION

This application is a U.S. national stage application of PCT/JP2017/012051 filed on Mar. 24, 2017, the contents of which are incorporated herein by reference.

TECHNICAL FIELD

The present invention relates to an induction heating cooker having a plurality of coils.

BACKGROUND ART

Existing induction heating cookers include a plurality of heating coils, in which the heating coil over which a heating object is not placed is supplied with electric power smaller than electric power applied to the heating coil over which a heating object is placed (for example, see Patent Literature 1).

CITATION LIST

Patent Literature

Patent Literature 1: Japanese Patent No. 5213937

SUMMARY OF INVENTION

Technical Problem

Some heating objects to be heated by an induction heating cooker are made of a composite material of a non-magnetic metal with a magnetic metal attached thereto. An example of such a heating object is a “frying pan with a metal-coated bottom” made of a frying pan of a non-magnetic aluminum material with a magnetic metal such as stainless steel being attached to the center of the bottom of the frying pan. In a typical heating object made of a composite material, a magnetic material is attached to the flat center portion of the non-magnetic bottom surface, but a curved outer peripheral portion of the bottom surface has no magnetic material.

However, while changing power distribution for each of the heating coils depending on an outer diameter of the heating object, the induction heating cooker disclosed in Patent Literature 1 performs no control depending on a material of the heating object. Therefore, when the heating object made of a composite material is inductively heated, the induction heating suitable for the material and shape of the heating object cannot be achieved, resulting in unevenness in heating temperature and a reduction in heating efficiency.

An object of the present invention, which has been made to solve the above problems, is to obtain an induction heating cooker making it possible to suppress unevenness in heating temperature and a reduction in heating efficiency when a heating object made of a composite material is inductively heated.

Solution to Problem

An induction heating cooker of an embodiment of the present invention includes a first coil, a second coil arranged outside the first coil, a third coil arranged outside the second coil, a first inverter circuit configured to supply a first high-frequency current to the first coil, a second inverter circuit configured to supply a second high-frequency current to the second coil, a third inverter circuit configured to supply a third high-frequency current to the third coil, a controller configured to control driving of the first inverter circuit, the second inverter circuit, and the third inverter circuit, and a load determining unit configured to determine a material of a heating object placed above each of the first coil, the second coil and the third coil, wherein when a material of the heating object placed above the first coil is a magnetic material and a material of the heating object placed above the second coil includes a non-magnetic material, the controller operates the first inverter circuit and the second inverter circuit, and stops an operation of the third inverter circuit, and controls such that a frequency of the second high-frequency current is higher than a frequency of the first high-frequency current.

Advantageous Effects of Invention

According to an embodiment of the present invention, when a material of the heating object placed above the first coil is a magnetic material and a material of the heating object placed above the second coil includes a non-magnetic material, the controller operates the first inverter circuit and the second inverter circuit, and stops an operation of the third inverter circuit, and controls such that a frequency of the second high-frequency current is higher than a frequency of the first high-frequency current.

Therefore, it is possible to perform the induction heating suitable for the material of the heating object and suppress unevenness in heating temperature when the heating object made of a composite material is inductively heated. Furthermore, unnecessary electric power is not input to the curved outer peripheral portion in the bottom surface of the heating object, thereby suppressing a reduction in heating efficiency.

