JP2020145183A - Induction heating coil and induction heating device - Google Patents

Abstract

To provide an induction heating coil capable of heating in various modes.SOLUTION: In operation of an induction heating coil 31, since a direction of a current in an outermost peripheral portion of a front-rear peripheral heating coil 35 and a left-right peripheral heating coil 36 and a direction of a current of an outer heating coil 34 are the same, a current flows counterclockwise around a center of each coil through the front-rear peripheral heating coil 35, the left-right peripheral heating coil 36, and the outer heating coil 34. A current flows in the clockwise direction in a plan view through an inner heating coil 32. Since a current flowing through each heating coil is an alternating current, a direction of the current flowing through each heating coil is reversed after half a cycle.SELECTED DRAWING: Figure 8

Description

The present invention relates to an induction heating coil and an induction heating device, and in particular, an induction heating coil that receives an electric current to heat an object to be heated arranged on the coil, and an induction heating device that supplies an electric current to the induction heating coil. Regarding.

There is known an induction heating device that supplies an electric current to a coil to heat an object to be heated arranged on the coil. For example, Patent Document 1 describes a central heating coil wound in a plane and a plurality of peripheral heating coils arranged adjacent to each other around the central heating coil and having an arc shape along the central heating coil. The induction heating device provided is disclosed. The induction heating device described in Patent Document 1 can strongly heat the region between the central heating coil and the peripheral heating coil by controlling the direction of the current supplied to each coil.

Japanese Unexamined Patent Publication No. 2013-179077

However, the induction heating device described in Patent Document 1 cannot perform various types of heating, such as being unable to strongly heat the side of the peripheral heating coil that is not adjacent to the central heating coil. Therefore, an object of the present invention is to obtain an induction heating device capable of performing heating in various modes in order to solve the above problems.

One aspect of the present invention is a plurality of peripheral heating coils having an arc-shaped outer peripheral portion, and an upper surface or a lower side of the peripheral heating coils, or a plane surface outward from the center of a circle having an arc shape as a part. Provided is an induction heating coil comprising: an outer heating coil wound in a circular shape.

Another aspect of the present invention includes an induction heating coil according to the above embodiment, an electric circuit that supplies an electric current to the inner heating coil, a plurality of peripheral heating coils, and an outer heating coil, a control circuit that controls the electric circuit, and the like. Provided is an induction heating device comprising the above.

INDUSTRIAL APPLICABILITY According to the present invention, an induction heating coil and an induction heating device capable of supplying an electric current to an outer heating coil to realize various magnetic flux distributions and performing heating in various modes can be obtained.

It is a perspective view which shows the induction heating apparatus which concerns on Embodiment 1 of this invention. It is a top view which shows the heating coil in Embodiment 1. FIG. It is a top view which omitted the outer heating coil from FIG. 2a. It is a schematic sectional view of the heating coil of FIG. 2a seen in the direction III-III. It is a figure for demonstrating an inner region, a peripheral region, and an outer region. It is a figure which shows the arrangement example of a ferromagnet. It is a figure which shows the structure of the electric circuit of the induction heating apparatus in Embodiment 1. FIG. It is a figure which shows the structure of the variable capacity capacitor of an electric circuit. It is a schematic diagram which shows an example of the operation of a heating coil. It is a figure which shows the Joule loss distribution of the object to be heated placed on the heating coil which passed the electric current as shown in FIG. It is a figure which shows the Joule loss distribution of the object to be heated when the outer heating coil is omitted from the heating coil of FIG. It is a schematic diagram which shows another example of the operation of a heating coil. It is a figure which shows the Joule loss distribution of the object to be heated placed on the heating coil which passed the electric current as shown in FIG. It is a schematic diagram which shows another example of the operation of a heating coil. It is a figure which shows the Joule loss distribution of the object to be heated placed on the heating coil which passed the electric current as shown in FIG. It is a top view of the heating coil which has the structure which omitted the outer heating coil from the heating coil in Embodiment 1. FIG. It is a figure which shows the Joule loss distribution of the object to be heated placed on the heating coil which passed the electric current as shown in FIG. It is a schematic diagram which shows another example of the operation of a heating coil. It is a figure which shows the Joule loss distribution of the object to be heated placed on the heating coil which passed the electric current as shown in FIG. It is a schematic diagram which shows another example of the operation of a heating coil. It is a figure which shows the Joule loss distribution of the object to be heated placed on the heating coil which passed the electric current as shown in FIG. It is a figure which shows the Joule loss distribution of the object to be heated placed on the heating coil which passed the electric current as shown in FIG. It is a figure which shows the Joule loss distribution of the object to be heated placed on the heating coil which passed the electric current as shown in FIG. It is a schematic diagram which shows another example of the operation of a heating coil. It is a figure which shows the Joule loss distribution of the object to be heated placed on the heating coil which passed the electric current as shown in FIG. It is a schematic cross-sectional view which shows the heating coil, the top plate, and the object to be heated. It is a schematic cross-sectional view which shows the heating coil, the top plate, and the object to be heated. It is a top view which shows the structure of the heating coil and ferromagnet of the induction heating apparatus which concerns on Embodiment 2. FIG. It is a top view of the ferromagnet according to the second embodiment. It is a front view of the ferromagnet according to the second embodiment. It is a figure which shows the Joule loss distribution of the object to be heated placed on the heating coil in Embodiment 2. FIG. It is a figure which shows the structure of the electric circuit of the induction heating apparatus in Embodiment 3 of this invention. It is a figure which shows the modification of the heating coil. It is a figure which shows the other modification of a heating coil. It is a schematic cross-sectional view which looked at the heating coil of FIG. 29 in the direction of XXX-XXX.

Hereinafter, the induction heating coil and the induction heating device according to the embodiment of the present invention will be described with reference to the drawings. In each embodiment, the same configurations are designated by the same reference numerals and description thereof will be omitted.

Embodiment 1.
<1. Overview>
FIG. 1 is a perspective view showing an induction heating device 100 according to a first embodiment of the present invention. The induction heating device 100 includes a housing 1 and a top plate 2 provided on the upper portion of the housing 1. The housing 1 and the top plate 2 form the outer shell of the induction heating device 100.

In the present specification, for convenience of explanation, the z-axis having the vertical upward direction is provided, and the x-axis and the y-axis orthogonal to each other are provided in a plane orthogonal to the z-axis. The + x direction is called the right direction, and the -x direction is called the left direction. Further, the + y direction is called the rear direction, and the −y direction is called the front direction.

The top plate 2 contains an insulator such as glass, ceramics or resin. An object to be heated such as a pan or a frying pan that is induced to be heated by the induction heating device 100 is placed on the top plate 2.

On the top plate 2, mounting position indications 3a, 3b, and 3c indicating a guideline for the position where the object to be heated is placed are displayed. The induction heating device 100 induces and heats the object to be heated placed on the placement position indications 3a, 3b, and 3c. The portions surrounded by the mounting position indications 3a, 3b, and 3c are referred to as heating ports 30a, 30b, and 30c, respectively. Although the heating ports are shown with three ports, the number of heating ports does not necessarily have to be three, and one or more may be used.

When the top plate 2 is made of a transparent material such as glass, the mounting position indications 3a, 3b, and 3c may be displayed by printing or the like on the back surface opposite to the front surface of the top plate 2 which is the mounting surface. .. Further, the mounting position displays 3a, 3b, and 3c are composed of a light emitting element such as a light emitting diode provided on the back surface side of the top plate 2 and a light guide member, and the position where the object to be heated is placed is the top plate 2. It may be configured so that it can be visually recognized from the surface side of the. In FIG. 1, the mounting position displays 3a, 3b, and 3c are shown so as to indicate the area on which the object to be heated is placed, but the mounting position displays 3a, 3b, and 3c are the positions where the object to be heated is placed. It may be displayed as a point indicating the center.

The induction heating device 100 may include a grill portion 4 having an opening / closing door that can be pulled out forward on the front surface of the housing 1. The grill portion 4 includes a heating chamber having a rectangular parallelepiped internal space. The heating chamber of the grill portion 4 is provided with a heating means such as a heater or a heating coil. The grill portion 4 is used, for example, when performing grill cooking for heating grilled fish. The grill portion 4 is not always necessary, and the induction heating device 100 does not have to include the grill portion 4.

The induction heating device 100 includes an operation unit 5a in front of the surface of the top plate 2, and an operation unit 5b and 5c in the front surface of the housing 1. The operation units 5a, 5b, and 5c adjust the heating power of the object to be heated by the heating ports 30a, 30b, and 30c, and start, stop, or adjust the heating power by the grill unit 4. It is used for such purposes. The positions where the operation units 5a, 5b, and 5c are provided are not limited to the positions shown in FIG. 1, and may be any place where the user can easily operate the induction heating device 100.

A display unit 6 for displaying the state of the induction heating device 100 is provided in front of the surface of the top plate 2. The display unit 6 may be, for example, a display device such as a liquid crystal display or an organic EL (Electroluminescence) display. Various information is displayed on the display unit 6 according to the operating status of the induction heating device 100. For example, the display unit 6 displays the electric power input to each heating port and the relative magnitude of the electric power. For example, the display unit 6 may display the temperature of the bottom surface of the object to be heated placed on each heating port. The position where the display unit 6 is provided is not limited to the front of the top plate 2, and may be any position that is easy for the user to see. For example, the display unit 6 may be provided on the front surface of the housing 1. Further, the display unit 6 may be configured by a display device with a touch panel, and the display unit 6 and the operation unit may be integrally formed.

Exhaust ports 7a, 7b, and 7c are provided behind the surface of the top plate 2. The exhaust ports 7a, 7b, and 7c are generated by heat generated by the grill portion 4, the electric circuit (not shown), the heating coil (not shown), etc. in the induction heating device 100, or by cooking in the grill portion 4. Discharges the oil smoke to the outside. In FIG. 1, the exhaust ports 7a, 7b, and 7c are provided on the top plate 2, but may be provided on the housing 1. Further, the number of exhaust ports is not limited to three, and may be one or more. If the induction heating device 100 does not have the grill portion 4, it may not have an exhaust port, and may be configured to dissipate heat from the surface of the housing 1, for example.

<2. Induction heating coil ＞
Inside the induction heating device 100, an induction heating coil for inductively heating an object to be heated such as a pot placed on the top plate 2 and an electric circuit for supplying an electric current to the inductive heating coil are provided. Has been done.

FIG. 2a is a plan view showing the induction heating coil 31 according to the first embodiment. FIG. 2b is a plan view in which the outer heating coil 34 is omitted from FIG. 2a. FIG. 3 is a schematic cross-sectional view of the induction heating coil 31 of FIG. 2a as viewed in the III-III direction. FIG. 3 also shows the top plate 2 for convenience of explanation. Hereinafter, the configuration of the induction heating coil 31 will be described with reference to FIGS. 2a and 3.

The induction heating coil 31 is provided below the top plate 2 (see FIG. 1). That is, the induction heating coil 31 is provided on the back surface side of the top plate 2 so as to face each of the heating ports 30a, 30b, and 30c shown in FIG. 1 in the z direction. The induction heating coil 31 may be formed by, for example, spirally winding a coated lead wire. The lead wire forming the induction heating coil 31 may be a litz wire formed by twisting a plurality of thin clothing wires coated with a thin wire made of a metal having high conductivity such as copper. The use of a litz wire as the lead wire is advantageous in that an increase in the electrical resistance of the heating coil at a high frequency of 20 kHz to 100 kHz can be suppressed.

One induction heating coil 31 has two terminals that are electrically connected to an electric circuit (hereinafter, simply referred to as "connection"). That is, one heating coil is a two-terminal circuit component having both ends. Further, if necessary, a magnetic material such as a ferrite core may be provided so as to face the surface of the induction heating coil 31 opposite to the surface facing the object to be heated in the z direction.

The induction heating coil 31 includes an inner heating coil 32 arranged at the center of the heating ports 30a, 30b, and 30c in a plan view, a front-rear peripheral heating coil 35 arranged before and after the inner heating coil 32, and an inner heating coil 32. It includes left and right peripheral heating coils 36 arranged on the left and right, front and rear peripheral heating coils 35, and outer heating coils 34 arranged on the upper side of the left and right peripheral heating coils 36.

In the example shown in FIG. 2a, the inner heating coil 32 is wound in a circle so as to surround the first inner heating coil 32a in a plan view and the first inner heating coil 32a in a plan view. Includes a second inner heating coil 32b.

In the example shown in FIG. 2a, the front-rear peripheral heating coil 35 includes a front heating coil 35a and a rear heating coil 35b. The front heating coil 35a and the rear heating coil 35b are arranged adjacent to the second inner heating coil 32b, and have an arc-shaped outer peripheral portion along the circular outer peripheral portion of the second inner heating coil 32b. The left and right peripheral heating coils 36 include a right side heating coil 36a and a left side heating coil 36b.

The right side heating coil 36a and the left side heating coil 36b are arranged adjacent to the second inner heating coil 32b, and have an arc-shaped outer peripheral portion along the circular outer peripheral portion of the second inner heating coil 32b. In other words, the front-rear peripheral heating coil 35 and the left-right peripheral heating coil 36 have a shape deformed so as to bend an ellipse so as to follow the shape of the inner heating coil 32 in a plan view. Each coil constituting the induction heating coil 31 may have any shape such as a rectangular shape, a concentric circle shape, and an elliptical shape. Further, each heating coil may have any width in the xyz axis direction by adjusting the number of windings and the number of winding stages.

In the examples shown in FIGS. 2a and 2b, the front heating coil 35a, the rear heating coil 35b, the right heating coil 36a and the left heating coil 36b all have the same shape and are centered on the center of the inner heating coil 32. They are arranged in rotational symmetry. That is, even if the front heating coil 35a, the rear heating coil 35b, the right side heating coil 36a, and the left side heating coil 36b are rotated 90 degrees around the center of the inner heating coil 32, the shape of the entire coil does not change.

The outer heating coil 34 is a circular coil wound concentrically with the inner heating coil 32 in a plan view. The outer heating coil 34 is arranged above the right heating coil 36a and the left heating coil 36b and facing the right heating coil 36a and the left heating coil 36b.

The arrangement of the inner heating coil 32, the front-rear peripheral heating coil 35, the left-right peripheral heating coil 36, and the outer heating coil 34 is not limited to the above. For example, each coil may have a slight deviation in arrangement by giving a slight width to the arrangement in the left-right side, front-rear side, or up-down side direction. That is, the arrangement of each coil does not have to exactly match the examples shown in FIGS. 2a and 2b. Further, the inner heating coil is not an indispensable configuration, and may have only a peripheral heating coil and an outer heating coil.

In FIG. 3, the outer heating coil 34 is not in contact with the right side heating coil 36a and the left side heating coil 36b. In this way, the outer heating coil 34 is arranged with a gap from the front-rear peripheral heating coil 35 and the left-right peripheral heating coil 36. However, the arrangement is not limited to this, and the outer heating coil 34 may be arranged so as to secure insulation from the front-rear peripheral heating coil 35 and the left-right peripheral heating coil 36.

For example, when a wire having a high withstand voltage is used for the outer heating coil 34, the front / rear peripheral heating coil 35, or the left / right peripheral heating coil 36 and sufficient insulation is secured, the outer heating coil 34 may be the front / rear peripheral heating coil 35 and. It may come into contact with the left and right peripheral heating coils 36. Further, for example, an insulating tape such as Capton tape or mica tape, an insulating paper, an insulating resin or the like is provided between the outer heating coil 34, the front and rear peripheral heating coils 35, and the left and right peripheral heating coils 36. May be good.

The inner heating coil 32, the front-rear peripheral heating coil 35, the left-right peripheral heating coil 36, and the outer heating coil 34 constituting the induction heating coil 31 may be individual heating coils, or at least among these heating coils. Two heating coils may be connected to form one heating coil. A switch such as a relay or a semiconductor switching element may be used to switch the connection of a plurality of heating coils according to, for example, a cooking purpose.

As shown in FIG. 4, in the present specification, the region extending from the center O of the induction heating coil 31 to the outer circumference of the second inner heating coil 32b in a plan view is referred to as a “first region” or an “inner region”. Further, in a plan view, the region sandwiched from the inner circumference of the second inner heating coil 32b to the inner circumference of the front-rear peripheral heating coil 35 and the left-right peripheral heating coil 36 is the "second region", "intermediate region" or ". Called "peripheral area". The region directly above the second inner heating coil 32b is both an inner region and a peripheral region. In this way, the inner region and the peripheral region may partially overlap. Further, in a plan view, a region outside the center of each of the front-rear peripheral heating coil 35 and the left-right peripheral heating coil 36 is referred to as a "third region" or an "outer region".

When an object to be heated is placed on the top plate 2 above the induction heating coil 31, when a current is supplied to the induction heating coil 31, the inner heating coil 32 heats the inner region near the center O. .. The inner heating coil 32, the front-rear peripheral heating coil 35, and the left-right peripheral heating coil 36 heat the outer peripheral region of the inner region. The front-rear peripheral heating coil 35, the left-right peripheral heating coil 36, and the outer heating coil 34 heat the outer region further outside the peripheral region.

In order to suppress interference between the coils constituting the induction heating coil 31, the ferromagnet may be arranged close to the upper side or the lower side of the induction heating coil 31. FIG. 5 is a diagram showing an arrangement example of the ferromagnet 99. FIG. 5 shows 20 ferromagnets 99 closely arranged below the induction heating coil 31. Although the reference numerals are omitted, the 20 rectangles shown in FIG. 5 each represent the ferromagnet 99.

<3. Electric circuit>
<3-1. Overall>
FIG. 6 is a diagram showing a configuration of an electric circuit 8 of the induction heating device 100 according to the first embodiment. The electric circuit 8 is provided inside the induction heating device 100 surrounded by the housing 1 and the top plate 2 shown in FIG. The electric circuit 8 includes inverter circuits 81 and 86, a power supply unit 82 for supplying electric power to the inverter circuits 81 and 86, a choke coil 83, a DC unit 84, and a control circuit 85.

<3-2. Power supply, etc.>
The power supply unit 82 includes a power fuse 12, an input capacitor 13, and a diode bridge 14.

The input capacitor 13 is connected in parallel to the AC side terminal (input side terminal) of the diode bridge 14. An input capacitor 13 and an external AC power supply 9 are connected in parallel to the AC side terminal of the diode bridge 14. The input capacitor 13 functions as a filter. The AC power supply 9 is a commercial power supply. The power fuse 12 is arranged between the AC power supply 9 and the input capacitor 13. The power fuse 12 prevents an overcurrent from flowing from the AC power source 9 into the induction heating device 100. The diode bridge 14 rectifies the AC power input to the AC side terminal into DC power. The rectified DC power is output from the DC side terminal (output side terminal) of the diode bridge 14.

One terminal of the choke coil 83 is connected to the DC side terminal of the diode bridge 14. A DC unit 84 is connected to the other terminal of the choke coil 83. The DC unit 84 is connected in parallel with the diode bridge 14 via the choke coil 83.

The DC unit 84 is, for example, a DC / DC converter such as a capacitor, a step-up chopper, a step-down chopper or a buck-boost chopper, or a power factor improving converter. When the DC unit 84 is a capacitor, the choke coil 83 and the DC unit 84 may form a filter. In this case, the DC voltage of the pulsating current in which the AC voltage is full-wave rectified and the voltage value fluctuates periodically is input to the inverter circuits 81 and 86.

When the DC unit 84 is a DC / DC converter, the DC unit 84 can change the voltage value of the DC voltage input to the inverter circuit 81 and the inverter circuit 86 connected in parallel. In this case, a DC voltage having a substantially constant voltage value is input to the inverter circuits 81 and 86.

When the DC unit 84 is a power factor improving converter, the DC unit 84 can improve the power factor of the AC power input from the AC power source 9.

A voltage detector or a current detector may be provided between the DC unit 84 and the inverter circuits 81 and 86. In this case, the DC unit 84 may calculate the power value applied to the inverter circuits 81 and 86.

<3-3. Inverter circuit ＞
Hereinafter, the configurations of the inverter circuit 81 and the inverter circuit 86 will be described. First, the configuration of the inverter circuit 81 will be described.

The inverter circuit 81 includes a first arm circuit 21, a second arm circuit 27, and a third arm circuit (common arm circuit) 24. The first arm circuit 21, the second arm circuit 27, and the common arm circuit 24 of the inverter circuit 81 are connected in parallel with each other. The first arm circuit 21, the second arm circuit 27, and the common arm circuit 24 of the inverter circuit 81 are also connected in parallel with the DC unit 84.

The first arm circuit 21 of the inverter circuit 81 comprises a first switching element 21a connected to the high voltage side of the DC unit 84 and a second switching element 21b connected to the low voltage side of the DC unit 84. Be prepared. The first switching element 21a and the second switching element 21b are connected in series. The connection point between the first switching element 21a and the second switching element 21b is called an output end 23.

The first and second switching elements 21a and 21b are composed of an IGBT (Insulated Gate Bipolar Transistor) and a MOSFET (Metal-Oxide-Semiconductor Field-Effect-Transistor). Alternatively, the first and second switching elements 21a and 21b may be discrete semiconductor switching elements. Such a discrete semiconductor switching element may be a power semiconductor module in which a plurality of semiconductor elements are incorporated in one package, such as an IPM (Intelligent Power Module).

The first arm circuit 21 of the inverter circuit 81 further includes a diode 22a connected in antiparallel to the first switching element 21a and a diode 22b connected in antiparallel to the second switching element 21b. When the first and second switching elements 21a and 21b are MOSFETs having a body diode, the diodes 22a and 22b are not always necessary.

A gate signal H1 is input to the gate terminal of the first switching element 21a based on control by the control circuit 85. On and off of the first switching element 21a is controlled based on the gate signal H1. Similarly, a gate signal L1 is input to the gate terminal of the second switching element 21b based on the control by the control circuit 85, and the on and off of the second switching element 21b are controlled.

The second arm circuit 27 of the inverter circuit 81 has the same configuration as the first arm circuit 21. That is, the second arm circuit 27 includes a first switching element 27a connected to the high voltage side of the DC unit 84 and a second switching element 27b connected to the low voltage side of the DC unit 84. The first switching element 27a and the second switching element 27b are connected in series via the output terminal 29. The second arm circuit 27 further includes a diode 28a connected in antiparallel to the first switching element 27a and a diode 28b connected in antiparallel to the second switching element 27b. A gate signal H7 is input to the gate terminal of the first switching element 27a based on the control by the control circuit 85, and a gate is input to the gate terminal of the second switching element 27b based on the control by the control circuit 85. The signal L7 is input.

The common arm circuit 24 of the inverter circuit 81 also has the same configuration as the first arm circuit 21 and the second arm circuit 27. That is, the common arm circuit 24 includes a first switching element 24a connected to the high voltage side of the DC unit 84 and a second switching element 24b connected to the low voltage side of the DC unit 84. The first switching element 24a and the second switching element 24b are connected in series via the output terminal 26. The common arm circuit 24 further includes a diode 25a connected in antiparallel to the first switching element 24a and a diode 25b connected in antiparallel to the second switching element 24b. A gate signal H4 is input to the gate terminal of the first switching element 24a based on the control by the control circuit 85, and a gate is input to the gate terminal of the second switching element 24b based on the control by the control circuit 85. The signal L4 is input.

In the example shown in FIG. 6, the inverter circuit 81 has a configuration in which three arm circuits are provided and one of them is a common arm, but the configuration of the electric circuit 8 of the present embodiment is this. Not limited to. For example, the inverter circuit 81 may be composed of a full bridge circuit or a half bridge circuit in order to supply electric power to one heating coil. Further, the inverter circuit 81 may not be provided with an arm circuit, and the inverter circuit may be configured by one switching element.

A variable capacitance capacitor 41 and an inner heating coil 32 are connected in series between the output end 23 of the first arm circuit 21 of the inverter circuit 81 and the output end 26 of the common arm circuit 24. The variable capacitor 41 and the inner heating coil 32 form a resonance circuit.

A variable capacitor 45 and an outer heating coil 34 are connected in series between the output end 26 of the common arm circuit 24 of the inverter circuit 81 and the output end 29 of the second arm circuit 27. The variable capacitor 45 and the outer heating coil 34 form a resonance circuit.

As described above, the first arm circuit 21 and the common arm circuit 24 of the inverter circuit 81 form the first full bridge circuit, and the second arm circuit 27 and the common arm circuit 24 form the second full bridge circuit. Consists of.

A larger current flows through the common arm circuit 24 than in the first arm circuit 21 and the second arm circuit 27. Therefore, for the first switching element 24a and the second switching element 24b constituting the common arm circuit 24, a switching element having an on-resistance smaller than that of the first arm circuit 21 and the second arm circuit 277 is used. preferable. For example, the first switching element 21a and the second switching element 21b of the first arm circuit 21 are made of a silicon semiconductor, and the first switching element 24a and the second switching element 24b of the common arm circuit 24 are wide banded. It may be composed of a gap semiconductor. This is because, when the withstand voltage is the same, the on-resistance of the switching element formed of the wide bandgap semiconductor can be made smaller than that of the switching element formed of the silicon semiconductor.

Similarly, the first switching element 27a and the second switching element 27b of the second arm circuit 27 are made of a silicon semiconductor, and the first switching element 24a and the second switching element 24b of the common arm circuit 24 are wide. It may be composed of a bandgap semiconductor.

As a result, the inverter circuit 81 can be realized at a lower cost than in the case where the switching elements of all the arm circuits are composed of wide bandgap semiconductors.

FIG. 7 is a diagram showing the configuration of the variable capacitance capacitor 41. The variable capacitance capacitor 41 is a capacitor whose capacitance can be changed by a control signal from the control circuit 85. The variable capacitor 41 has a configuration in which a portion in which the capacitor 41b and the switch 41c are connected in series and a capacitor 41a are connected in parallel. The switch 41c is, for example, a switch such as a relay or a semiconductor switching element. The switch 41c switches the open / closed state by a control signal from the control circuit 85.

However, the configuration of the variable capacitance capacitor 41 is not limited to the above, and any capacitor may be used as long as the capacitance can be changed. For example, the variable capacitance capacitor 41 may have a configuration in which a switch connected in parallel to the capacitor is connected in series to another capacitor. The number of capacitors and switches used in the variable capacitance capacitor 41 is not limited to these, and may be any number.

The variable capacitor 45 and the variable capacitors 61 and 65 described later also have a configuration in which the capacitance can be changed, similarly to the variable capacitor 41.

Next, the configuration of the inverter circuit 86 will be described. The inverter circuit 86 has the same configuration as the inverter circuit 81 except for the heating coil to be connected. In the following, detailed description of the same configuration as the inverter circuit 81 will be omitted.

The inverter circuit 86 includes a first arm circuit 51 connected in parallel with each other, a second arm circuit 57, and a third arm circuit (common arm circuit) 54.

The first arm circuit 51 of the inverter circuit 86 comprises a first switching element 51a connected to the high voltage side of the DC unit 84 and a second switching element 51b connected to the low voltage side of the DC unit 84. Be prepared. The first switching element 51a and the second switching element 51b are connected in series via the output terminal 53. The first arm circuit 51 further includes a diode 52a connected in antiparallel to the first switching element 51a and a diode 52b connected in antiparallel to the second switching element 51b. A gate signal H2 is input to the gate terminal of the first switching element 51a based on the control by the control circuit 85, and a gate is input to the gate terminal of the second switching element 51b based on the control by the control circuit 85. The signal L2 is input.

The second arm circuit 57 of the inverter circuit 86 has the same configuration as the first arm circuit 51. That is, the second arm circuit 57 includes a first switching element 57a connected to the high voltage side of the DC unit 84 and a second switching element 57b connected to the low voltage side of the DC unit 84. The first switching element 57a and the second switching element 57b are connected in series via the output terminal 59. The second arm circuit 57 further includes a diode 58a connected in antiparallel to the first switching element 57a and a diode 58b connected in antiparallel to the second switching element 57b. A gate signal H8 is input to the gate terminal of the first switching element 57a based on the control by the control circuit 85, and a gate is input to the gate terminal of the second switching element 57b based on the control by the control circuit 85. The signal L8 is input.

The common arm circuit 54 of the inverter circuit 86 also has the same configuration as the first arm circuit 51 and the second arm circuit 57. That is, the common arm circuit 54 includes a first switching element 54a connected to the high voltage side of the DC unit 84 and a second switching element 54b connected to the low voltage side of the DC unit 84. The first switching element 54a and the second switching element 54b are connected in series via the output terminal 56. The common arm circuit 54 further includes a diode 55a connected in antiparallel to the first switching element 54a and a diode 55b connected in antiparallel to the second switching element 54b. A gate signal H5 is input to the gate terminal of the first switching element 54a based on the control by the control circuit 85, and a gate is input to the gate terminal of the second switching element 54b based on the control by the control circuit 85. The signal L5 is input.

A variable capacitance capacitor 61 and a front-rear peripheral heating coil 35 are connected in series between the output end 53 of the first arm circuit 51 of the inverter circuit 86 and the output end 56 of the common arm circuit 54.

The variable capacitance capacitor 65 and the left and right peripheral heating coils 36 are connected in series between the output end 56 of the common arm circuit 54 of the inverter circuit 86 and the output end 59 of the second arm circuit 57.

In the example shown in FIG. 6, the number of arm circuits included in the inverter circuits 81 and 86 was three, but the number of arm circuits is not limited to this. For example, each inverter circuit may have four or more arm circuits, and one or a plurality of arm circuits may be a common arm circuit.

Further, each switching element constituting each arm circuit may be composed of a discrete semiconductor switching element, and a semiconductor module for power in which a plurality of semiconductor elements are incorporated in one package such as an IPM (Intelligent Power Module). It may be composed of. For example, each inverter circuit may include a power semiconductor module containing three arm circuits. A power semiconductor module incorporating three arm circuits is inexpensive because it is widely used in a drive inverter device for a three-phase AC motor. By using such a power semiconductor module in the inverter circuit, the induction heating device 100 can be realized at low cost. Further, each arm circuit may have a configuration in which a snubber circuit including a capacitor and a resistor is connected in parallel to the switching element to suppress a surge voltage applied to the switching element.

In the above, the configurations of the inverter circuits 81 and 86 in which some of the heating coils are connected have been described, but each heating coil may be all connected, or an independent inverter circuit for each heating coil. May be provided. Further, the connection between the inverter circuit and the plurality of heating coils may be appropriately switched by using a relay or the like. As a result, current can be supplied to the plurality of heating coils by at least one or more inverter circuits.

<3-4. Load detector>
Hereinafter, a load detection unit (not shown) will be described. The load detection unit is a circuit that determines the material of the object to be heated mounted on the inner heating coil 32, the outer heating coil 34, the front-rear peripheral heating coil 35, and the left-right peripheral heating coil 36.

For example, the impedance measured at both ends of each heating coil differs depending on whether the object to be heated is a magnetic metal such as iron or a non-magnetic material such as aluminum or copper. Using this difference in impedance, the material of the object to be heated placed on each heating coil is determined. Impedance differences are measured, for example, as changes in resistance or inductance.

The position where the load detection unit is provided will be described. For example, a first load detection unit is provided in series with the inner heating coil 32, a second load detection unit is provided in series with the outer heating coil 34, and a third load detection unit is provided in series with the front and rear peripheral heating coils 35. A fourth load detection unit may be provided in series with the left and right peripheral heating coils 36.

The load detection unit measures, for example, the ratio of the current of the DC unit 84 to the current of the load detection unit provided in series with each heating coil, and determines the material of the object to be heated from the difference in the current ratio depending on the object to be heated. You may. The load detection unit may detect the material of the object to be heated by using other known load detection techniques not described above.

The load detection unit determines the material of the inner region near the center of the object to be heated based on the discrimination result of the first load detection unit connected to the inner heating coil 32, and the second load connected to the outer heating coil 34. Based on the discrimination result between the detection unit, the third load detection unit connected to the front and rear peripheral heating coils 35, and the fourth load detection unit connected to the left and right peripheral heating coils 36, the area outside the inner region is covered. The material of the heated material may be determined.

The load detection unit may be provided separately from the control circuit 85, but may be provided integrally with the control circuit 85. For example, only a current detector or a voltage detector is provided in the load detection unit, the detected current value or voltage value is input to the control circuit 85, and the control circuit 85 calculates the detected current value or voltage value and receives the voltage value. The material of the heated object may be determined. That is, the control circuit 85 may have a function of a load detection unit.

A current detector and a voltage detector are provided between the output end of the arm circuit and the heating coil, and the control circuit 85 that functions as a load detector is based on the current value and voltage value of the heating coil to be heated. The material may be discriminated.

<3-5. Control circuit>
The control circuit 85 shown in FIG. 6 controls the entire operation of the induction heating device 100. The control circuit 85 may be configured by using an integrated circuit having an analog circuit or a digital circuit. Further, the control circuit 85 may be an arithmetic processing unit such as a CPU (Central Processing Unit), an MPU (Micro Processor Unit), or an MCU (Micro Controller Unit) that realizes a predetermined function by executing a program. The control circuit 85 may include a gate drive circuit and a protection circuit for driving each switching element, if necessary.

The control circuit 85 controls switching of the switching elements 21a, 21b, 24a, 24b, 27a, 27b, 51a, 51b, 54a, 54b, 57a and 57b. That is, the control circuit 85 outputs the gate signals H1, H2, H4, H5, H7, H8, L1, L2, L4, L5, L7 and L8. In FIG. 6, the signal line connecting the gate terminal of each switching element and the control circuit 85 is omitted.

Further, the control circuit 85 controls the change of the capacitance of the variable capacitance capacitors 41, 45, 61 and 65. For example, the control circuit 85 outputs a signal for controlling the opening and closing of the switch 41c shown in FIG. In FIG. 6, the signal line connecting each variable capacitance capacitor and the control circuit 85 is omitted.

Further, the control circuit 85 is connected to a load detection unit (not shown) and receives a signal from the load detection unit. Further, the control circuit 85 is connected to the operation unit 5 and the display unit 6, and transmits / receives signals such as an operation signal and a display signal between the operation unit 5 and the display unit 6. The operation unit 5 includes the operation units 5a, 5b, and 5c shown in FIG.

The control circuit 85 receives a signal from the load detection unit and outputs a gate signal for driving each switching element in order to heat the material to be heated. As a means for changing the magnitude of the current, the control circuit 85 may use frequency control for moving the frequency for switching the inverter closer to the resonance frequency of the resonance circuit or away from the resonance frequency. Instead of or in combination with frequency control, the control circuit 85 may control the magnitude of the current using duty control that increases or decreases the on-duty width of the gate signal.

The control circuit 85 controls, for example, so that the current flowing through each coil has the same frequency, magnitude, and phase, but the present invention is not limited to this, and the magnetic flux in the peripheral region and the outer region can be strengthened. I hope I can.

The advantage of having the same frequency as the current flowing through each coil is that it suppresses the interference sound (beat) caused by the difference in frequency between the currents flowing through each coil and does not cause discomfort to the user. In order to suppress the interference sound (groaning), in addition to setting the current flowing through each coil to the same frequency, for example, the frequency difference of the current between the coils may be made larger than the maximum value of the audible frequency. It is known that the maximum value of human audible frequency is about 20 kHz.

When the inverter circuit is composed of a full bridge circuit, the control circuit 85 controls the magnitude of the current by using the phase difference control that controls by increasing or decreasing the phase difference of the output current with respect to the output voltage of the inverter. You can.

When the DC unit 84 is a DC / DC converter, the control circuit 85 may perform switching control of the switching element included in the DC / DC converter.

<4. Operation>
The induction heating device 100 of the present embodiment can strongly heat the outer region.

The magnetic flux can be strengthened by controlling the directions of the currents flowing through the two adjacent heating coils so that they are in the same direction. On the other hand, the magnetic flux can be weakened by controlling the directions of the currents flowing through the two adjacent heating coils to be opposite to each other. In the present embodiment, the outer region can be strongly heated by controlling the direction of the electric current to control the strengthening of the magnetic flux.

FIG. 8 is a schematic view showing an example of the operation of the induction heating coil 31. In FIG. 8, the direction of the current is indicated by a broken line arrow. In FIG. 8, the direction of the electric current at the outermost peripheral portion of the front-rear peripheral heating coil 35 and the left-right peripheral heating coil 36 is the same as the direction of the electric current of the outer heating coil 34. That is, a current flows in the front-rear peripheral heating coil 35, the left-right peripheral heating coil 36, and the outer heating coil 34 in a counterclockwise direction around the center of each coil in a plan view. A current flows through the inner heating coil 32 in the clockwise direction in a plan view. Since the current flowing through each heating coil is an alternating current, the direction of the current flowing through each heating coil is reversed after half a cycle.

The control circuit 85 may control not only the direction of the current flowing through the heating coils 32, 34, 35 and 36, but also the magnitude, phase and frequency of the current.

In the induction heating coil 31 and the metal arranged around the induction heating coil 31, a current (induced current) induced by the interference of the induction heating coils 32, 34, 35 and 36 is generated. The control circuit 85 may control the magnitude of the current flowing through each of the heating coils 32, 34, 35 and 36 to zero or near zero so as to cancel the induced current. Alternatively, by means such as turning off the switching element, the control circuit 85 stops the supply of current to each of the heating coils 32, 34, 35 and 36 so that the induced current flows through the stopped heating coils. May be good.

FIG. 9a is a diagram showing the Joule loss distribution of the object to be heated placed on the induction heating coil 31 in which an electric current is passed as shown in FIG. Joule loss is caused by the resistance of the object to be heated. For comparison, FIG. 9b shows the Joule loss distribution of the object to be heated when the outer heating coil 34 is omitted from the induction heating coil 31 of FIG. In FIGS. 9a and 9b, the brighter the color (whiter), the larger the Joule loss.

When a current is applied not only to the front-rear peripheral heating coil 35 and the left-right peripheral heating coil 36 but also to the outer heating coil 34 as shown in FIG. 8 (FIG. 9a), and when no current is applied to the outer heating coil 34 (FIG. Compared with 9b), the outer region can be heated more strongly. Further, when a current is passed through the outer heating coil 34, the magnetic flux is not weakened, so that highly efficient and uniform heating can be realized.

Further, the induction heating device 100 can realize various Joule loss distributions other than the above.

FIG. 10 is a schematic view showing another example of the operation of the induction heating coil 31. In FIG. 10, a current flows in the front-rear peripheral heating coil 35 and the outer heating coil 34 in the counterclockwise direction in a plan view. A current flows through the inner heating coil 32 in the clockwise direction in a plan view. That is, FIG. 10 shows a state in which the supply of current to the left and right peripheral heating coils 36 is stopped in FIG.

FIG. 11 is a diagram showing a Joule loss distribution of an object to be heated placed on an induction heating coil 31 in which an electric current is passed as shown in FIG. By passing an electric current as shown in FIG. 10, the front-rear portion (the portion along the y-axis) of the peripheral region and the front-rear portion of the outer region can be strongly heated.

FIG. 10 shows an example in which a current is passed through the front-rear peripheral heating coil 35, the inner heating coil 32, and the outer heating coil 34, and no current is passed through the left and right peripheral heating coils 36, but the present invention is not limited thereto. For example, the control circuit 85 (see FIG. 6) may control the left and right peripheral heating coils 36, the inner heating coil 32, and the outer heating coil 34 so that the current does not flow through the front and rear peripheral heating coils 35. Good.

FIG. 12 is a schematic view showing another example of the operation of the induction heating coil 31. In FIG. 12, a current flows in the front-rear peripheral heating coil 35 and the left-right peripheral heating coil 36 in the counterclockwise direction in a plan view, and a current flows in the inner heating coil 32 in the clockwise direction. That is, FIG. 12 shows a state in which the current flowing through the outer heating coil 34 in FIG. 8 is stopped.

FIG. 13 is a diagram showing a Joule loss distribution of an object to be heated placed on an induction heating coil 31 in which an electric current is passed as shown in FIG. By passing an electric current as shown in FIG. 12, it is possible to strongly heat the peripheral region while not heating the outer region. Regarding the Joule loss in the outer region, as can be seen by comparing FIG. 9b and FIG. 13, the result is not the same as when the induction heating device 100 does not include the outer heating coil 34 (FIG. 9b), and the result is further outer. Joule loss in the region can be suppressed. This is because the magnetic flux generated by the current flowing through the front-rear peripheral heating coil 35 and the left-right peripheral heating coil 36 interlinks with the outer heating coil 34, whereby the front-rear peripheral heating coil 35 and the left-right peripheral heating coil 36 are connected to the outer heating coil 34. This is because the induced current flows in the direction opposite to the direction of the current in the outer region of the coil and cancels the magnetic flux leaking to the outer region.

In this way, the induction heating device 100 can realize heating (exact heating) that does not heat the outer region. Further, in the induction heating device 100, the leakage of noise to the surroundings can be suppressed by canceling the magnetic flux leaking to the outer region.

FIG. 14 is a plan view of the heating coil 37 having a configuration in which the outer heating coil 34 is omitted from the induction heating coil 31 in the first embodiment. In FIG. 14, a current flows in the front-rear peripheral heating coil 35 and the left-right peripheral heating coil 36 in the counterclockwise direction in a plan view, and no current flows in the inner heating coil 32.

FIG. 15 is a diagram showing a Joule loss distribution of an object to be heated placed on a heating coil 37 through which an electric current is passed as shown in FIG. In FIG. 15, magnetic flux is generated around the front-rear peripheral heating coil 35 and the left-right peripheral heating coil 36, and Joule loss is observed.

FIG. 16 is a schematic view showing another example of the operation of the induction heating coil 31. In FIG. 16, a current flows in the front-rear peripheral heating coil 35 and the left-right peripheral heating coil 36 in a counterclockwise direction in a plan view, and no current flows in the inner heating coil 32 and the outer heating coil 34. That is, FIG. 16 shows a state in which the current flowing through the inner heating coil 32 and the outer heating coil 34 is stopped in FIG. 8 as compared with FIG. Further, the induction heating coil 31 of FIG. 16 has a configuration in which the outer heating coil 34 is added to the heating coil 37 of FIG. 14 as compared with FIG.

FIG. 17 is a diagram showing a Joule loss distribution of an object to be heated placed on an induction heating coil 31 in which an electric current is passed as shown in FIG. Comparing FIG. 17 with FIG. 15, by adding the outer heating coil 34, it is possible to heat only the peripheral region without heating the outer region. This is because the magnetic flux generated by the current flowing through the front-rear peripheral heating coil 35 and the left-right peripheral heating coil 36 interlinks with the outer heating coil 34, thereby interlocking with the outer heating coil 34, as described with reference to FIGS. 12 and 13. This is because an induced current flows through the heating coil 34 in the direction opposite to the direction of the current in the outer region of the front-rear peripheral heating coil 35 and the left-right peripheral heating coil 36, and cancels the magnetic flux leaking to the outer region.

FIG. 18 is a schematic view showing another example of the operation of the induction heating coil 31. In FIG. 18, a current flows in the front-rear peripheral heating coil 35, the left-right peripheral heating coil 36, and the outer heating coil 34 in the counterclockwise direction in a plan view, and no current flows in the inner heating coil 32. That is, FIG. 18 shows a state in which the current flowing through the inner heating coil 32 is stopped in FIG. 8 as compared with FIG. Further, FIG. 18 shows a state in which a current flows in the counterclockwise direction in a plan view to the outer heating coil 34 in which the current did not flow in FIG. 16 as compared with FIG.

19a, 19b and 19c are diagrams showing the Joule loss distribution of the object to be heated placed on the induction heating coil 31 in which an electric current is passed as shown in FIG. The difference between FIGS. 19a, 19b and 19c is the magnitude of the current flowing through the outer heating coil 34. For example, FIG. 19a shows a Joule loss distribution when a current having an effective value I ₁ is passed through the outer heating coil 34. FIG. 19b shows a Joule loss distribution when a current having an effective value I ₂ is passed through the outer heating coil 34. FIG. 19c shows a Joule loss distribution when a current having an effective value I ₃ is passed through the outer heating coil 34. Here, I ₁ <I ₂ <I ₃ .

As can be seen by comparing FIG. 19a and FIG. 15, even if the outer heating coil 34 is arranged as shown in FIG. 18, the same Joule loss, that is, heating as in the case where the outer heating coil 34 is not arranged (FIG. 14) is generated. It can be realized.

By increasing the amount of current flowing through the outer heating coil 34, the peripheral region and the outer region can be strongly heated as shown in FIG. 19b. By further increasing the amount of the current flowing through the outer heating coil 34, as shown in FIG. 19c, it is possible to realize a heating mode in which only the outer region is strongly heated without heating the peripheral region.

FIG. 20 is a schematic view showing another example of the operation of the induction heating coil 31. In FIG. 20, a current flows in the front-rear peripheral heating coil 35 and the outer heating coil 34 in the counterclockwise direction in a plan view, and no current flows in the inner heating coil 32 and the left-right peripheral heating coil 36. That is, FIG. 18 shows a state in which the current flowing through the inner heating coil 32 and the left and right peripheral heating coils 36 is stopped in FIG. 8 as compared with FIG.

FIG. 21 is a diagram showing a Joule loss distribution of an object to be heated placed on an induction heating coil 31 in which an electric current is passed as shown in FIG. By passing an electric current as shown in FIG. 20, it is possible to heat only the peripheral region and the outer region, which are the upper parts of the front-rear peripheral heating coil 35, in the front-rear direction without heating the inner region. Further, due to the presence of the outer heating coil 34, it is possible to strongly heat the outer region in the front-rear direction.

FIG. 20 shows an example in which a current is passed through the front-rear peripheral heating coil 35 and the outer heating coil 34, and no current is passed through the inner heating coil 32 and the left-right peripheral heating coil 36, but the present invention is not limited thereto. For example, the control circuit 85 (see FIG. 6) may control so that a current flows through the front-rear peripheral heating coil 35 and the outer heating coil 34, and no current flows through the inner heating coil 32 and the left-right peripheral heating coil 36. ..

Further, for example, the control circuit 85 may supply a current to each coil constituting the induction heating coil 31 by switching in a time division manner. Further, the control circuit 85 may switch ON / OFF of the current of each coil constituting the induction heating coil 31 according to the input from the operation unit 5 (see FIG. 6). Further, the induction heating device 100 may store various operation modes shown in the above operation example in an internal storage device or the like, and the user may select the operation mode by using the operation unit 5.

In the above, the control circuit 85 has shown an example in which the directions of the currents flowing through the adjacent heating coils are controlled to be the same in order to strongly heat the coils, but the control circuits 85 are adjacent to each other in the heating coils of the present invention. It may be controlled so as to weaken the magnetic flux generated by the heating coil. That is, the currents flowing through the adjacent heating coils may be controlled to be in different directions.

<5. Effects, etc.>
With the induction heating device 100 having the above configuration, various modes of heating and cooking can be realized.

FIG. 22 shows that when the object to be heated 110 is placed on the induction heating coil 31 via the top plate 2, the induction heating coil 31, the top plate 2 and the object to be heated 110 are oriented in the same direction as in FIG. It is a schematic sectional view as seen (direction III-III of FIG. 2a). By providing the outer heating coil 34, the induction heating device 100 can strongly heat the R portion 111 even when the object to be heated 110 has a curved portion (R portion) 111 in the outer region as shown in FIG. 22. ..

Since the R portion 111 is separated from the front-rear peripheral heating coil 35 and the left-right peripheral heating coil 36 in the z direction due to the curvature, it can only interlink with a weak magnetic flux without the outer heating coil 34 and cannot be sufficiently heated. .. In the induction heating device 100 according to the present embodiment, the outer region can be heated by two types of coils (front-rear peripheral heating coil 35 and outer heating coil 34, or left and right peripheral heating coil 36 and outer heating coil 34).

Further, the induction heating device 100 can realize various heat generation distributions by controlling the magnitude and direction of the current flowing through each coil constituting the induction heating coil 31. Convection can be generated in the liquid in the object to be heated 110 by utilizing the heat gradient generated by various heat generation distributions and the boiling bubbles generated in the high temperature portion. In particular, since the induction heating device 100 can strongly heat the outer region, it is possible to generate strong convection from the outside to the inside of the object to be heated 110. Further, since the induction heating device 100 can select the coil to be heated, it is possible to control the magnitude of convection (the length of the convection distance).

As described above, since the induction heating device 100 can generate various convections depending on the size and strength, the effect of improving the permeation of the taste into the ingredients in cooking and the effect of shortening the permeation time are realized. it can. Further, the contents of the object to be heated 110 can be appropriately agitated by convection, and the contents can be prevented from burning or spilling.

The induction heating device 100 also has an advantage when heating an object to be heated made of a different material such that a magnetic material is attached to the bottom surface of a non-magnetic material such as aluminum. In FIG. 23, when such an object to be heated 112 is placed on the induction heating coil 31 via the top plate 2, the induction heating coil 31, the top plate 2 and the object to be heated 112 are shown in FIG. It is a schematic cross-sectional view seen in the same direction (direction III-III of FIG. 2a).

The object to be heated 112 includes a main body 114 made of a non-magnetic material such as aluminum, and a magnetic material 113 arranged on a bottom surface portion. In the conventional induction heating device, when the main body 114 made of a non-magnetic material is heated by, for example, a low frequency, the switching element, the heating coil, and the capacitor may be destroyed by an overcurrent or an overvoltage. Therefore, the induction heating device of the prior art limits the current flowing through the heating coil when the load detection unit (not shown) determines that the material of the object to be heated 112 at the upper part of the outer region is a non-magnetic material. On the other hand, the induction heating device 100 of the present invention includes an outer heating coil 34 and an inverter circuit for passing an electric current through the outer heating coil 34, as compared with the conventional induction heating device. That is, since a plurality of inverter circuits are provided to heat the outer region, even if the magnitude of the current supplied to the front-rear peripheral heating coil 35 and the left-right peripheral heating coil 36 under the non-magnetic material is weakened, it is added. Since the insufficient current can be supplied by the inverter circuit that supplies the current to the outer heating coil 34 and the outer heating coil 34, sufficient heating can be performed.

Further, although an example in which a plurality of heating coils and a plurality of inverter circuits are provided for the main body 114 made of a non-magnetic material is shown above, the present invention is not limited to this. For example, even if a plurality of inverter circuits are not provided, the outer heating coil 34, the front and rear peripheral heating coils 35, and the left and right peripheral heating coils 36 may be connected and heated by one inverter capable of supplying a current to the connected heating coils. As a result, as compared with the induction heating device of the prior art, the outer region is concentrated by providing a plurality of heating coils such as the outer heating coil 34, the front and rear peripheral heating coils 35, and the left and right peripheral heating coils 36 in the outer region. Therefore, the induction heating device 100 of the present invention can heat the outer region more strongly than the induction heating device of the prior art.

Embodiment 2.
Hereinafter, the induction heating device according to the second embodiment of the present invention will be described. Compared with the first embodiment, in the second embodiment, a ferromagnet is added to the lower side of the induction heating coil 31.

FIG. 24 is a plan view showing the configurations of the induction heating coil 31 and the ferromagnetic materials 98 and 99 of the induction heating device according to the second embodiment. In FIG. 24, in addition to the induction heating coil 31 and the 20 ferromagnets 99 as described in FIG. 5, four ferromagnets 98 are further provided.

FIG. 25a is a plan view of the ferromagnet 98. FIG. 25b is a front view of the ferromagnet 98.

As can be seen from the direction of the electric current indicated by the arrow in FIG. 24, the upper part of the ferromagnetic material 98 is adjacent to the four regions between the front-rear peripheral heating coil 35 and the left-right peripheral heating coil 36. The direction of the current flowing through the front-rear peripheral heating coil 35 and the direction of the current flowing through the left-right peripheral heating coil 36 are opposite. Therefore, the current flowing through the front-rear peripheral heating coil 35 and the left-right peripheral heating coil 36 has an effect of weakening the magnetic flux in these four regions. Therefore, as shown in FIG. 9a, the Joule loss in the vicinity of these four regions and immediately above the outer heating coil 34 near these regions is small.

Therefore, in the second embodiment, the ferromagnetic material 98 is arranged in each of these four regions, whereby the effect of strengthening the magnetic flux can be obtained.

FIG. 26 is a diagram showing the Joule loss distribution of the object to be heated placed on the induction heating coil 31 in the second embodiment. By arranging the ferromagnet 98 in the four regions, strong heating can be realized over the entire circumference of the upper part of the outer heating coil 34. As a result, uneven heating can be suppressed especially in four regions.

In FIGS. 24, 25a and 25b, the bottom surface of the ferromagnet 98 is shown in a rectangular shape, but the shape of the ferromagnet 98 is not limited to this. For example, in order to reduce costs, the shape of the ferromagnetic material 98 may be a trapezoidal shape having a wide outside and a narrow inside. Further, in FIG. 24, the width of the ferromagnet 98 is larger than the width of the ferromagnet 99, but may be less than or equal to the width of the ferromagnet 99. Further, the shape of the ferromagnetic material 98 is not limited to the L-shape shown in FIGS. 24, 25a and 25b, and may be a flat shape.

Embodiment 3.
Hereinafter, the induction heating device according to the third embodiment of the present invention will be described. FIG. 27 is a diagram showing the configuration of the electric circuit 308 of the induction heating device 300 according to the third embodiment. Compared to the first embodiment, in the third embodiment, the induction heating device 300 further includes a zero volt voltage detecting means 360 connected in parallel with the input capacitor 13. Since the other configurations of the induction heating device 300 are the same as those of the first and second embodiments, the description thereof will be omitted.

As shown in the first and second embodiments, the control circuit 85 controls the inverter circuits 81 and 86. Specifically, the control circuit 85 controls the inverter circuits 81 and 86 so as to supply a current to each coil of the induction heating coil 31 or to stop the current flowing through each coil. In the third embodiment, the control circuit 85 detects the timing when the AC voltage of the AC power supply 9 becomes zero by using the zero-volt voltage detecting means 360, and flows to each coil of the induction heating coil 31 based on this timing. Control to supply or stop current.

The zero-volt voltage detecting means 360 is a means for detecting the timing at which the AC voltage of the AC power supply 9 becomes the zero-volt voltage (hereinafter, referred to as “zero cross timing”). The zero-volt voltage detecting means 360 is composed of, for example, a resistor, a diode, a photocoupler, and the like. There are two zero cross timings per cycle of AC voltage. The zero-volt voltage detecting means 360 may detect at least one zero cross timing per cycle of the AC voltage. In other words, the zero-volt voltage detecting means 360 need only be able to detect at least one of the zero-cycle or half-cycle zero cross timings of the AC voltage. The zero volt voltage detecting means 360 outputs the detected zero cross timing to the control circuit 85.

In the induction heating device 300 according to the third embodiment, the DC unit 84 may be a capacitor having a small capacity. In this case, when the inverter circuits 81 and 86 are driven and operated, it becomes a load and the electric charge stored in the capacitor of the DC unit 84 is consumed. Therefore, the voltage applied to the DC unit 84 is stepped down. The AC power input to the AC side terminal is not sufficiently rectified by the diode bridge 14, and a voltage close to zero is applied to the inverter circuits 81 and 86 at the timing of half a cycle of the AC power supply 9. Therefore, the zero cross timing detected by the zero volt voltage detecting means 360 and the timing at which the voltage input to the inverter circuits 81 and 86 becomes a voltage close to zero are substantially the same. Similarly, at the same timing as the zero cross timing detected by the zero volt voltage detecting means 360, the voltage input to the inverter circuits 81 and 86 becomes a voltage close to zero, so that the current flowing through each heating coil also becomes zero. It will be close.

When the current flowing through each coil is stopped, if the current supply is stopped at the timing when the current is flowing through each coil, the induction heating coil 31, the ferrite core around the induction heating coil 31, and the coil are arranged. The object to be heated vibrates or is magnetically distorted, causing abnormal noise. Since the abnormal noise becomes smaller as the current when stopping is smaller, the current flowing through each coil becomes almost zero at the timing when the voltage input to the inverter circuits 81 and 86 becomes almost zero (the current flowing through each coil becomes almost zero). When this happens), it is preferable to stop the current flowing through each coil. On the other hand, when the current is supplied to each coil, if the current is supplied at the timing when the input voltage of the inverter circuits 81 and 86 deviates from the timing close to zero, the current is suddenly started to be supplied to each coil with a large voltage. Become. As a result, abnormal noise is generated.

In particular, in the case of intermittent operation in which the current supply and stop are periodically repeated, if the current is supplied and stopped at the timing when the above abnormal noise is generated, the abnormal noise will be generated in the intermittent cycle. hear. Therefore, the user may hear the emphasized sound, which may cause discomfort, discomfort, or the like to the user.

In the present embodiment, the control circuit 85 executes supply or stop of the current flowing through each coil of the induction heating coil 31 at the zero cross timing detected by the zero volt voltage detecting means 360. As a result, it is possible to reduce the abnormal noise generated at the timing of supplying or stopping the current.

Similarly, the control circuit 85 may intermittently operate the inner heating coil 32 and the plurality of peripheral heating coils based on the zero cross timing detected by the zero volt voltage detecting means 360. Thereby, the abnormal noise generated in the inner heating coil 32 and the plurality of peripheral heating coils can be reduced.

Further, for example, when the inner heating coil 32 and the outer heating coil 34 are switched and operated alternately, the control circuit 85 may control the switching timing based on the zero cross timing. As a result, when the inner heating coil 32 and the outer heating coil 34 are operated alternately, the abnormal noise can be reduced. Similarly, the control circuit 85 may control the switching timing based on the zero cross timing when the plurality of peripheral heating coils and the outer heating coils 34 are switched and operated alternately. Similarly, the control circuit 85 may control the switching timing based on the zero cross timing when the inner heating coil 32 and the plurality of peripheral heating coils are switched and operated alternately. By performing the above control, it is possible to reduce the abnormal noise that may occur at the timing of switching.

The control circuit 85 may perform an intermittent operation based on the timing when the AC voltage of the AC power supply 9 becomes zero, and may be operated so as to reduce abnormal noise. Further, at least two coils of the induction heating coils 31 may be combined in any way, and when at least two coils are switched and operated alternately, the timing at which the AC voltage of the AC power supply 9 becomes zero. The switching timing may be controlled based on the above. As a result, the abnormal noise generated in the coil can be reduced.

Further, when the current flowing through each coil is large, if the current flowing through the coil is stopped, the turn-off loss may increase and the loss of the switching element may also increase. Further, if the current supply is suddenly started or the current is suddenly stopped at the timing when the current is flowing, a large noise may be generated. In the present embodiment, since the control circuit 85 executes the start or stop of the current supply in synchronization with the zero cross timing, the loss of the switching element can be reduced or the generation of large noise can be prevented.

As described above, in order to realize heating with less demerits such as abnormal noise, in the induction heating device 300 according to the present embodiment, the AC voltage of the AC power supply 9 detected by the zero volt voltage detecting means 360 is zero. The current flowing through each heating coil of the induction heating coil 31 is supplied or stopped based on the timing.

In FIG. 27, the zero-volt voltage detecting means 360 connected in parallel with the input capacitor 13 has been described, but the present embodiment is not limited to this. For example, the zero-volt voltage detecting means 360 may be configured by any circuit as long as it can detect the zero cross timing of the AC voltage of the AC power supply 9.

Further, the induction heating device 300 may include a voltage detection circuit (not shown) for detecting the voltage of the AC power supply instead of the zero volt voltage detecting means 360. In this case, the control circuit 85 may acquire the voltage of the AC power supply detected by the voltage detection circuit and determine the zero cross timing based on the acquired voltage.

As described above, the induction heating device 300 further includes a voltage detection circuit that detects the voltage of the AC power supply 9 for supplying electric power to the induction heating coil 31. The control circuit 85 causes the electric circuit 308 to start supplying the current to the induction heating coil 31 and to stop the supply of the current to the induction heating coil 31 based on the voltage detected by the voltage detection circuit. Perform at least one of the actions.

Further, the induction heating device 300 may include a zero volt voltage detecting means 360 for detecting the timing when the voltage of the AC power supply 9 becomes zero. The control circuit 85 controls the electric circuit 308 and starts supplying the current to the induction heating coil 31 at the timing when the voltage of the AC power supply 9 becomes zero. Alternatively, or in combination with this, the control circuit 85 controls the electric circuit 308 to stop the supply of current to the induction heating coil 31 at the timing when the voltage of the AC power supply 9 becomes zero.

Thereby, the generation of abnormal noise in the induction heating device 300 can be reduced.

Other embodiments.
FIG. 28 is a diagram showing a modified example of the heating coil represented by 331. FIG. 29 is a diagram showing another modification of the heating coil represented by 332. As shown in FIGS. 28 and 29, in order to strongly heat the outer region, the outer heating coil 34 is located on the inner peripheral side (inner heating coil 32 side) of the front and rear peripheral heating coils 35 and the left and right peripheral heating coils 36. May be placed on the outside.

FIG. 30 is a schematic cross-sectional view of the heating coil of FIG. 29 as viewed in the XXX-XXX directions. As shown in FIG. 30, the outer heating coil 34 may be arranged in the same plane as the inner heating coil 32, the front-rear peripheral heating coil 35, and the left-right peripheral heating coil 36.

Further, in order to strongly heat the inner region, the outer heating coil 34 may be arranged on the inner peripheral side of the front-rear peripheral heating coil 35 and the left-right peripheral heating coil 36. Further, in order to strongly heat the peripheral region, the outer heating coil 34 may be arranged between the inner heating coil 32, the front and rear peripheral heating coils 35, and the left and right peripheral heating coils 36.

As shown above, the outer heating coil 34 may be arranged on the upper side or the lower side or in the same plane as the inner heating coil 32, the front-rear peripheral heating coil 35, and the left-right peripheral heating coil 36. The arrangement of the outer heating coil 34 has the effect of being able to strongly heat the selected region by selecting the arrangement according to the region of the object to be heated to be strongly heated. However, when the outer heating coils 34 are arranged on the same plane, for example, the outermost outer diameter of the heating coil 31 and the outermost outer diameter of the heating coil 331 are the same, and the same object to be heated is heated, each heating coil is used. Since only the range of each heating coil can be heated, the ratio of heating by the inner heating coil 32, the front-rear peripheral heating coil 35, and the left-right peripheral heating coil 36 may be narrowed.

As described above, the induction heating device according to the present invention is arranged adjacent to the inner heating coil 32 wound in a circular shape in a plane and the periphery of the inner heating coil, and is an arc along the outer peripheral portion of the inner heating coil. The front-rear peripheral heating coil 35 and the left-right peripheral heating coil 36 having an outer peripheral portion of the shape, and the front-rear peripheral heating coil 35 and the left-right peripheral heating coil 36 on the upper or lower side of the front-rear peripheral heating coil 35 and the left-right peripheral heating coil 36. It is provided with an outer heating coil 34 that is wound in a circular shape in a plane so that the portions overlap. The induction heating device 100 controls the electric circuit 8 that supplies an electric current to the inner heating coil 32, the front-rear peripheral heating coil 35, the left-right peripheral heating coil 36, the outer heating coil 34, and the electric circuit 8. Further provided with a circuit 85.

The outer heating coil 34 is located outside the outer peripheral portion of the front-rear peripheral heating coil 35 and the left-right peripheral heating coil 36 adjacent to the inner heating coil 32, and above or below the front-rear peripheral heating coil 35 and the left-right peripheral heating coil 36. It may be wound in a flat shape.

The outer heating coil 34 may be wound in a plane on the upper side or the lower side of the outer peripheral portion of the front-rear peripheral heating coil 35 and the left-right peripheral heating coil 36, which is the farthest from the inner heating coil. Further, in the outer heating coil 34, the front-rear peripheral heating coil 35 and the left-right peripheral heating coil 36 are shifted upward or downward so that the upper or lower surface of the inner heating coil 32 coincides with the surface on the Z axis. May be good.

The front-rear peripheral heating coil 35 and the left-right peripheral heating coil 36 may have an arc-shaped outer peripheral portion arranged concentrically with the inner heating coil 32.

The front heating coil 35a, the rear heating coil 35b, the right side heating coil 36a, and the left side heating coil 36b all have the same shape and may be arranged rotationally symmetrically about the center of the inner heating coil 32.

The outer heating coil 34 may be arranged so as to be concentric with the inner heating coil 32.

The electric circuit 8 may include inverter circuits 81 and 86 that generate an electric current.

The control circuit 85 controls the inverter circuits 81 and 86 so as to independently supply an electric current to the inner heating coil 32, the front and rear peripheral heating coils 35, the left and right peripheral heating coils 36, and the outer heating coil 34. can do.

The control circuit 85 controls at least one of the direction and magnitude of the current supplied to the inner heating coil 32, each of the front-rear peripheral heating coil 35 and the left-right peripheral heating coil 36, and the outer heating coil 34. be able to.

The control circuit 85 has a direction of the current flowing in the outer peripheral portion of the outer peripheral portion of the front-rear peripheral heating coil 35 and the left-right peripheral heating coil 36 farthest from the inner heating coil 32, and a vertical direction in the outer peripheral portion of the outer heating coil 34. It can be controlled so that the direction of the current flowing in the portion facing the is the same.

The control circuit 85 can control so as to stop the current flowing through at least one of the inner heating coil 32, the front-rear peripheral heating coil 35, the left-right peripheral heating coil 36, and the outer heating coil 34. it can.

The induction heating device according to the present invention may further include a ferromagnet 98 arranged in a region between the peripheral heating coil and another peripheral heating coil adjacent thereto.

At least two of the inner heating coil 32, the front-rear peripheral heating coil 35, the left-right peripheral heating coil 36, and the outer heating coil 34 may be connected in series or in parallel.

At least two of the inner heating coil 32, the front-rear peripheral heating coil 35, the left-right peripheral heating coil 36, and the outer heating coil 34 may be connected to the same arm circuit.

1 housing, 2 top plate, 5 operation part, 6 display part, 8 electric circuit, 31 induction heating coil, 32 inner heating coil, 32a first inner heating coil, 32b second inner heating coil, 34 outer heating coil, 35 Front and rear peripheral heating coil, 35a front heating coil, 35b rear heating coil, 36 left and right peripheral heating coil, 36a right heating coil, 36b left heating coil, 81 inverter circuit, 82 power supply unit, 85 control circuit, 86 inverter circuit, 98 Ferromagnetic, 99 ferromagnetic, 100 induction heating device.

Claims (18)

Multiple peripheral heating coils with an arc-shaped outer circumference,
An outer heating coil that is wound in a circular shape on the upper side, the lower side, or the outer side of the circle having the arc shape as a part of the peripheral heating coil.
An induction heating coil characterized by being provided with. The induction heating coil according to claim 1, wherein the plurality of peripheral heating coils are arranged on the same circumference. The induction heating coil according to claim 1 or 2, wherein the outer heating coil is arranged on the upper side or the lower side of the peripheral heating coil so as to partially overlap the peripheral heating coil. An inner heating coil wound in a circular shape in a plane is further provided inside the peripheral heating coil.
The outer heating coil is claimed to be wound in a plane on the upper side or the lower side of the peripheral heating coil outside the outer peripheral portion of the peripheral heating coil adjacent to the inner heating coil. Item 2. The induction heating coil according to any one of Items 1 to 3. The induction according to claim 4, wherein the outer heating coil is wound in a plane on the upper side or the lower side of the outer peripheral portion of the outer peripheral portion of the peripheral heating coil, which is farthest from the inner heating coil. Heating coil. The induction heating coil according to claim 4 or 5, wherein the plurality of peripheral heating coils have an arc-shaped outer peripheral portion arranged concentrically with the inner heating coil. The induction heating coil according to claim 6, wherein the plurality of peripheral heating coils all have the same shape and are arranged rotationally symmetrically with respect to the center of the concentric circles. The induction heating coil according to any one of claims 4 to 7, wherein the outer heating coil is arranged so as to be concentric with the inner heating coil. The induction heating coil according to any one of claims 1 to 8.
An inner heating coil wound in a circular shape on the inside of the peripheral heating coil,
An electric circuit that supplies an electric current to the induction heating coil and
A control circuit that controls the electric circuit and
An induction heating device comprising. The induction heating device according to claim 9, wherein the electric circuit includes an inverter circuit that generates an electric current. The claim is characterized in that the control circuit controls the inverter circuit so as to independently supply an electric current to the inner heating coil, each of the plurality of peripheral heating coils, and the outer heating coil. Item 10. The induction heating device according to item 10. The control circuit is characterized in that it controls at least one of the directions and magnitudes of currents supplied to the inner heating coil, each of the plurality of peripheral heating coils, and the outer heating coil. The induction heating device according to any one of claims 9 to 11. In the control circuit, the direction of the current flowing in the outer peripheral portion of the peripheral heating coil farthest from the inner heating coil and the current flowing in the outer peripheral portion of the outer heating coil facing the outer peripheral portion in the vertical direction. The induction heating device according to any one of claims 9 to 12, wherein the direction is controlled to be the same as that of the device. The control circuit is characterized in that it controls so as to stop the current flowing through at least one of the inner heating coil, each of the plurality of peripheral heating coils, and the outer heating coil. The induction heating device according to any one of 9 to 13. The induction heating according to any one of claims 9 to 14, further comprising a ferromagnet arranged in a region between the peripheral heating coil and another peripheral heating coil adjacent thereto. apparatus. The induction heating device according to any one of claims 9 to 15, wherein at least two of the inner heating coil, the plurality of peripheral heating coils, and the outer heating coil are connected in series or in parallel. .. The induction heating according to any one of claims 9 to 16, wherein at least two of the inner heating coil, the plurality of peripheral heating coils, and the outer heating coil are connected to the same arm circuit. apparatus. It is further equipped with a voltage detection circuit that detects the timing when the voltage of the AC power supply for supplying power to the induction heating coil becomes zero.
Based on the timing detected by the voltage detection circuit, the control circuit causes the electric circuit to start supplying a current to the induction heating coil, and stops supplying a current to the induction heating coil. The induction heating device according to any one of claims 9 to 17, wherein at least one of the operations is performed.