Induction heating coil and induction heating cooker equipped with the same

Abstract

To provide an induction heating coil that suppresses uneven heating of an object to be heated, and an induction heating cooker equipped with the same.SOLUTION: An induction heating coil for heating an object to be heated includes an insulating substrate, and a coil portion arranged parallel to the surface of the substrate and consisting of a pattern in which a conductor is wound multiple times in a spiral shape around an axis perpendicular to the surface of the substrate, the coil portion has an outer shape with an asymmetric axis which is a virtual straight line parallel to the surface of the substrate and passing through the center, and which is a straight line which divides the pattern asymmetrically, the outer shape is a figure represented by a virtual line drawn along the outermost periphery of the pattern from the starting point at the outermost end of the pattern, connecting the end point and starting point of the virtual line such that no step is created at the point of contact between the end point and starting point of the virtual line.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The present disclosure relates to an induction heating coil for heating an object to be heated and an induction heating cooker including the same.

Background Art

[0002] Conventionally, an induction heating cooker is known that is provided below a top plate on which an object to be heated such as a pan is placed and has a circular heating coil for heating the object to be heated (see, for example, Patent Document 1). The heating coil generates a high-frequency magnetic field by a high-frequency current supplied from an inverter substrate. Below the heating coil, a plurality of ferrites that absorb magnetic flux generated from the heating coil are provided radially.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In the induction heating cooker disclosed in Patent Document 1, when the shape of the bottom surface of the object to be heated has an asymmetric axis, such as an ellipse, the shape of the heating coil does not have an asymmetric axis. Therefore, the shape of the heating coil is different from the shape of the bottom surface of the object to be heated. In this case, the heating power varies depending on the position of the bottom surface of the object to be heated, and heating unevenness occurs. Hereinafter, specific examples of the occurrence of heating unevenness will be described.

[0005] When the shape of the bottom surface of the object to be heated is an ellipse and the major axis of the ellipse is larger than the diameter of the heating coil, in the bottom surface of the object to be heated, the region of the circle near the center with the minor axis as the diameter is heated by the heating coil. However, the outside of the circular region near the center of the bottom surface of the object to be heated protrudes from the circular heating coil and is not heated by the heating coil. Although the circular region near the center of the object to be heated is heated by the heating coil, uneven heating occurs in the object to be heated because the vicinity of both ends in the major axis direction is not heated by the heating coil.

[0006] The present disclosure has been made to solve the above problems, and an induction heating coil for suppressing uneven heating of an object to be heated and an induction heating cooker including the same are obtained.

Means for Solving the Problems

[0007] The induction heating coil according to the present disclosure is an induction heating coil for heating an object to be heated, and includes a substrate having insulation, and a coil portion provided in parallel with the surface of the substrate and configured in a pattern in which a conductor is wound a plurality of times in a spiral shape around an axis perpendicular to the surface of the substrate. The coil portion has an outer shape having an asymmetric axis, which is a virtual straight line parallel to the surface of the substrate and passing through the center and dividing the pattern asymmetrically. The outer shape is a figure represented by the virtual line connecting the end point and the start point so that no step occurs at the contact point between the end point of the virtual line and the start point when a virtual line is drawn along the outermost periphery starting from the end portion of the outermost periphery of the pattern.

[0008] The induction heating cooker according to the present disclosure includes the above induction heating coil.

Effects of the Invention

[0009] According to the present disclosure, when the shape of the bottom surface of the object to be heated matches the outer shape of the pattern of the coil portion, the entire bottom surface of the object to be heated generates heat by the coil portion, and uneven heating of the object to be heated can be suppressed.

Brief Description of the Drawings

[0010]

Figure 1

Figure 2

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Figure 18

MODE FOR CARRYING OUT THE INVENTION

[0011] Hereinafter, embodiments of the induction heating coil and the induction heating cooker according to the present disclosure will be described with reference to the drawings. The present disclosure is not limited to the following embodiments, and various modifications can be made without departing from the gist of the present disclosure. Further, the present disclosure includes all combinations of configurations that can be combined among the configurations shown in the following embodiments. In addition, the induction heating coil shown in the drawings shows an example of a coil to which the technical idea of the present disclosure is applied, and the applicable coil of the present disclosure is not limited by the aspect shown in the drawings. The induction heating cooker shown in the drawings shows an example of a device to which the technical idea of the present disclosure is applied, and the applicable device of the present disclosure is not limited by the aspect shown in the drawings. In the following description, terms indicating directions (for example, "right", "left", "front", "rear", etc.) are used as appropriate for easy understanding, but these are for the purpose of explanation and do not limit the present disclosure. In each figure, for convenience of explanation, three coordinate axes of the X-axis, Y-axis, and Z-axis are shown to define the direction, but the arrangement of each component is not limited by the coordinate axes shown in the figure. Also, in each figure, those with the same reference numerals are the same or corresponding ones, which is common throughout the specification. Note that in each drawing, the relative dimensional relationship or shape of each component may be different from the actual one.

[0012] Embodiment 1. The configuration of the induction heating cooker equipped with the induction heating coil according to Embodiment 1 will be described. FIG. 1 is a schematic configuration diagram showing an example of the configuration of an induction heating cooker 100 according to Embodiment 1. As shown in FIG. 1, the X-axis, Y-axis, and Z-axis are mutually equiangular and their directions are defined. The direction opposite to the Y-axis arrow is the vertical direction. The induction heating cooker 100 has a top plate 1 on which an object to be heated 200 such as a pot or a frying pan is placed, and a generally box-shaped housing 2 provided below the top plate 1. FIG. 1 shows a state in which the top plate 1 is removed from the housing 2 and a part of the housing 2 is cut out in order to explain the internal structure of the housing 2.

[0013] The top plate 1 is made of a non-metallic material such as heat-resistant glass or ceramic. The top plate 1 is provided with a heating port 3 which is an area where the object to be heated 200 is placed. FIG. 1 shows the case where two heating ports 3 are provided, but the number of heating ports 3 is not limited to two. FIG. 1 shows the case where the shape of the heating port 3 is circular, but the shape of the heating port 3 is not limited to circular.

[0014] Also, the top plate 1 is provided with an operation unit 4 for receiving operation inputs by the user, and a display unit 5 for displaying information. The operation unit 4 is an input device such as a touch panel that receives inputs regarding heating conditions such as the heating temperature or heating time of the induction heating cooker 100, and operation instructions such as heating start or stop. FIG. 1 shows a configuration example when the operation unit 4 is provided on the top plate 1, but the operation unit 4 may be provided on the front surface of the housing 2 instead of the top plate 1, or the operation unit 4 may be provided on both the front surface of the housing 2 and the top plate 1.

[0015] The display unit 5 displays the presence or absence of heating at the heating port 3, the set temperature and heating mode, the timer, and caution information for the user. The display unit 5 is composed of a liquid crystal display or an LED (Light Emitting Diode), or a combination thereof. FIG. 1 shows a configuration example when the display unit 5 is provided on the top plate 1, but the display unit 5 may be provided on the front surface of the housing 2 instead of the top plate 1, or the display unit 5 may be provided on both the front surface of the housing 2 and the top plate 1.

[0016] Below the top plate 1, an induction heating coil 300 is provided inside the housing 2. Also, inside the housing 2, below the induction heating coil 300, an inverter circuit 6 that supplies a high-frequency current to the induction heating coil 300 and a control device 7 that controls the heating by the induction heating coil 300 and its stop are provided. The induction heating coil 300 is disposed below the heating port 3. The induction heating coil 300 generates a magnetic flux by the high-frequency current supplied from the inverter circuit 6 and inductively heats the object to be heated 200 placed above the heating port 3. FIG. 1 shows a configuration in which two induction heating coils 300 are provided corresponding to two heating ports 3, but one or three or more induction heating coils 300 may be provided. The configuration of the induction heating coil 300 will be described in detail later.

[0017] The inverter circuit 6 includes a rectifier circuit (not shown) that converts an AC power supply into DC and a drive circuit (not shown) that generates a high-frequency current from the DC and supplies it to the induction heating coil 300. The drive circuit (not shown) is a known electric circuit such as a half-bridge inverter, a full-bridge inverter, or a single-stone voltage resonance inverter. The drive circuit (not shown) is composed of switching elements such as IGBT (Insulated Gate Bipolar Transistor) or MOSFET (Metal Oxide Semiconductor Field Effect Transistor).

[0018] The hardware of the control device 7 is, for example, a dedicated circuit device that realizes the functions provided in the induction heating cooker 100. The hardware of the control device 7 may have a configuration including a memory that stores a software program and an arithmetic device such as a processor that executes processing according to the software program, like a microcomputer. The control device 7 controls the inverter circuit 6 based on the setting content input via the operation unit 4 by the user's operation, thereby heating the object to be heated 200 by the induction heating coil 300.

[0019] Next, the configuration of the induction heating coil 300 shown in FIG. 1 will be described. FIG. 2 is a plan view showing a configuration example of the induction heating coil 300 according to the first embodiment. The induction heating coil 300 is installed inside the induction heating cooker 100 such that the direction opposite to the Y-axis arrow shown in FIG. 2 is the vertical direction and the XZ plane is horizontal. The induction heating coil 300 includes a substrate 10, a coil portion 11, a shield ring 12, and a magnetic plate 13. The induction heating coil 300 is manufactured by a manufacturing technique similar to that of a printed wiring board. The coil portion 11, the shield ring 12, and the magnetic plate 13 correspond to the conductive wiring portions in the printed wiring board. The substrate 10 corresponds to the insulating substrate that electrically insulates between the wirings in the printed wiring board.

[0020] The substrate 10 is made of a material having insulation properties, such as glass epoxy resin, for example. Of the two surfaces of the substrate 10, the surface on which the object to be heated 200 is placed via the top plate 1 of the induction heating cooker 100 is referred to as the "front surface", and the opposite surface is referred to as the "back surface". In the induction heating coil 300 shown in FIG. 2, the coil portion 11 is provided on the front surface of the substrate 10.

[0021] As shown in FIG. 2, the coil portion 11 is configured in a pattern in which a conductor 18 is wound a plurality of times in a spiral shape on the substrate 10 around an axis axs perpendicular to the front surface of the substrate 10. In FIG. 2, when the coil portion 11 is viewed in the vertical direction (the direction opposite to the Y-axis arrow) from above the induction heating coil 300, the outer shape of the pattern of the coil portion 11 is an ellipse. FIG. 3 is a diagram showing the pattern of the coil portion 11 extracted from the induction heating coil 300 shown in FIG. 2. The broken line shown in FIG. 3 indicates the outer shape of the pattern of the coil portion 11. The outer shape of the pattern is an ellipse.

[0022] The pattern of the coil portion 11 is a planar shape represented by the conductor 18. The outer shape of the pattern is a geometric figure such as a circle, an ellipse, an oval, or a polygon, represented by a virtual line drawn along the outermost periphery of the pattern of the coil portion 11. Specifically, the outer shape of the pattern is a geometric figure represented by a virtual line connecting the end point and the start point, where a virtual line is drawn along the outermost periphery of the pattern of the coil portion 11 starting from the end of the outermost periphery of the pattern of the coil portion 11, and no step is generated at the contact point between the end point and the start point of the virtual line. When a virtual line is extended along the outermost periphery of the pattern around the axis axs and the end point of the virtual line approaches the start point, a broken line without a step is formed at the contact point between the end point and the start point by gradually separating the virtual line from the outermost periphery of the pattern in the radial direction as shown in FIG. 3. FIG. 3 shows the case where the outer shape of the pattern of the coil portion 11 is an ellipse.

[0023] The straight lines axL1, axL2, and asm1 shown in FIG. 3 are virtual straight lines parallel to the XZ plane and passing through the axis axs. The straight lines axL1 and axL2 are symmetry axes that divide the pattern of the coil portion 11 symmetrically. In contrast, the straight line asm1 is an asymmetric axis that divides the pattern of the coil portion 11 asymmetrically. Thus, the coil portion 11 having an elliptical shape has an outer shape with an asymmetric axis. The straight lines axL1 and axL2 are an example of symmetry axes, and the straight line asm1 is an example of an asymmetric axis.

[0024] The conductor 18 is, for example, a metal foil such as a copper foil. The coil portion 11 functions as a current circuit. Both ends of the conductor 18 forming the pattern of the coil portion 11 are connected to the inverter circuit 6, and the coil portion 11 generates a high-frequency magnetic flux. The generated magnetic flux intersects the bottom surface of the object to be heated 200 such as a cooking utensil placed directly above the induction heating coil 300. When the magnetic flux intersects the bottom surface of the object to be heated 200, eddy currents are generated on the bottom surface, and Joule heat is generated by the resistance component between the eddy currents and the object to be heated 200, heating the bottom surface of the object to be heated 200.

[0025] The thickness of the conductor 18 is set based on the skin effect. When a high-frequency current is supplied to the coil part 11 by the inverter circuit 6, there is a known skin effect in which the current flowing through the conductor 18 concentrates and flows on the conductor surface. The skin depth d, which is the depth at which the current penetrates from the surface of the conductor 18 into the conductor interior, is expressed by Equation (1).

[0026]

Equation

[0027] In Equation (1), f is the frequency of the high-frequency current, μ is the magnetic permeability of the conductor, and σ is the conductivity of the conductor. The skin depth d expressed by Equation (1) represents the depth at which the amplitude of the current becomes 1 / e of that on the conductor surface. e is the base of the natural logarithm. Therefore, the skin depth d represents the depth at which the amplitude of the current becomes 37% of that on the conductor surface. When the skin depth d doubles, the amplitude of the current attenuates to 13.5%, and when the skin depth d triples, the amplitude of the current attenuates to 5%.

[0028] Here, when copper is used as the material of the coil part 11 and the driving frequency is set to 20 kHz which is in the audible range or higher, from Equation (1), the skin depth d becomes 0.5 mm. Doubling 0.5 mm results in 1.0 mm, and tripling 0.5 mm results in 1.5 mm. Even if the plate thickness of the coil part 11 is made thicker than necessary, the current does not penetrate, which only causes an increase in weight and cost, and no effect of reducing the resistance of the coil part 11 can be obtained. On the other hand, if the plate thickness of the coil part 11 is too thin, it causes an increase in the resistance value of the coil part 11, an increase in the loss of the coil part 11, and a cause of the temperature rise of the coil part 11.

[0029] If the thickness of the coil portion 11 is too thin, it will cause an increase in the resistance value of the coil portion 11, an increase in the loss of the coil portion 11, and a temperature rise of the coil portion 11. Therefore, for example, when using a copper foil as the conductor 18, the thickness of the coil portion 11 should be at least 0.5 mm, which is 1 times the skin depth d, and considering the relationship between the skin depth d and the amplitude of the current, it is desirable to ensure a thickness of 1.0 mm or more, which is 2 times the skin depth d. This can sufficiently reduce the resistance value of the coil portion 11 and reduce the conduction loss.

[0030] On the other hand, it is desirable that the thickness of the coil portion 11 is 2.5 mm or less, which is 5 times the skin depth d. This is because when the thickness of the coil portion 11 becomes 5 times the skin depth d, the amplitude of the current decays to 0.7%, and when it is thicker than this, it can be considered that no current substantially flows.

[0031] The shield ring 12 is arranged so as to surround the outer periphery of the coil portion 11. The shield ring 12 serves to reduce the leakage magnetic flux emitted outside the housing 2 of the induction heating cooker 100. This will be specifically explained. When the magnetic flux generated by the coil portion 11 intersects with the shield ring 12, eddy currents are generated in the shield ring 12 in a direction to cancel the generated magnetic flux, and the leakage magnetic flux to the surroundings is reduced. The shield ring 12 is formed in an annular pattern on the same substrate 10 as the coil portion 11 by, for example, a metal foil such as the same copper foil as the conductor 18. Also, the shield ring 12 may be formed in an annular pattern by a conductor such as aluminum or copper different from the conductor 18 of the coil portion 11.

[0032] The magnetic plate 13 is made of a ferromagnetic material such as ferrite. The magnetic plate 13 is provided on the back side of the substrate 10 and below the coil portion 11. The magnetic plate 13 increases the density of the magnetic flux generated around the coil portion 11 and increases the input power of the object to be heated 200. FIG. 2 shows a configuration example when four magnetic plates 13 are arranged radially. The number of magnetic plates 13 is not limited to four.

[0033] Note that the configuration example shown in FIG. 2 shows the configuration when the coil portion 11 is arranged on the surface of the substrate 10, but the coil portion 11 may be arranged on each of the front and back surfaces of the substrate 10. Further, the coil portion 11 shown in FIG. 2 is constituted by a single coil without a split surface in which the conductor 18 is wound from the inner peripheral side toward the outer peripheral side so that the conductor interval in the radial direction is constant, but the coil portion 11 may be a split coil having a split surface. For example, when the coil portion 11 is constituted by two split coils, the portion where the two split coils are connected to each other becomes the split surface. An example of the split coil will be described in Embodiment 4.

[0034] The induction heating coil 300 of the first embodiment includes an insulating substrate 10 and a coil portion 11 provided in parallel with the surface of the substrate 10 and configured in a pattern in which the conductor 18 is wound a plurality of times in a spiral shape around an axis axs perpendicular to the surface of the substrate 10. The coil portion 11 has a virtual straight line parallel to the surface of the substrate 10 and passing through the center, which is a straight line asm1 that asymmetrically divides the pattern of the coil portion 11.

[0035] According to the first embodiment, when the bottom surface shape of the object to be heated 200 is an ellipse, since the outer shape of the pattern of the coil portion 11 matches the bottom surface shape of the object to be heated 200, the magnetic flux generated by the coil portion 11 intersects the entire bottom surface of the object to be heated 200 and generates heat. Thereby, uneven heating of the object to be heated 200 can be suppressed.

[0036] Further, since the induction heating coil 300 of the first embodiment is manufactured using a manufacturing technique similar to that of a printed wiring board, compared with a conventional heating coil using Litz wire, the degree of freedom in shape is high, and it is possible to form a curve with a small diameter. Therefore, the conductor pattern can be formed up to the central portion of the coil portion 11. Thereby, uneven heating due to insufficient heating of the central portion of the object to be heated 200 having an elliptical bottom surface can be suppressed.

[0037] (Modification Example 1 of the First Embodiment) FIG. 4 is a plan view of the induction heating coil 300 according to Modification 1 of Embodiment 1. FIG. 4 is a plan view when the induction heating coil 300 is viewed from above in the vertical direction (opposite to the direction of the Y-axis arrow) in FIG. 1. As shown in FIG. 4, the coil part 11 is configured in a pattern in which a conductor 18 is wound a plurality of times in a spiral shape on the substrate 10 around an axis axs perpendicular to the surface of the substrate 10.

[0038] In FIG. 4, when the coil part 11 is viewed from above in the vertical direction (opposite to the direction of the Y-axis arrow) of the induction heating coil 300, the outer shape of the pattern of the coil part 11 is oval. FIG. 5 is a diagram showing the pattern of the coil part 11 extracted from the induction heating coil 300 shown in FIG. 4. The broken line shown in FIG. 5 indicates the outer shape of the pattern of the coil part 11. As shown in FIG. 5, when a line is drawn along the outermost periphery of the pattern of the coil part 11 to surround the coil part 11, the outer shape of the pattern is oval. As shown in FIG. 4, the outer shape of the coil part 11 of this Modification 1 is a shape in which a straight part 21 and a curved part 26 are combined. The outer shape of the pattern of the coil part 11 is a shape obtained by extending an ellipse in the horizontal direction (X-axis). Although FIG. 4 shows that the outer shape of the pattern of the coil part 11 is a shape obtained by extending an ellipse in the horizontal direction (X-axis), it may be a shape obtained by extending the ellipse in the vertical direction.

[0039] The straight lines axL3, axL4, and asm2 shown in FIG. 5 are virtual lines parallel to the XZ plane and passing through the axis axs. The straight lines axL3 and axL4 are symmetry axes that divide the pattern of the coil part 11 symmetrically. In contrast, the straight line asm2 is an asymmetric axis that divides the pattern of the coil part 11 asymmetrically. Thus, the oval-shaped coil part 11 has an outer shape with an asymmetric axis. The straight lines axL3 and axL4 are an example of symmetry axes, and the straight line asm2 is an example of an asymmetric axis.

[0040] According to this Modification 1, when the bottom surface shape of the object to be heated 200 is oval, since the outer shape of the pattern of the coil part 11 matches the bottom surface shape of the object to be heated 200, the magnetic flux generated by the coil part 11 intersects the entire bottom surface of the object to be heated 200 and generates heat. Thereby, uneven heating of the object to be heated 200 can be suppressed.

[0041] In addition, since the induction heating coil 300 of the first modification example is manufactured using a manufacturing technique similar to that of a printed wiring board, compared with a conventional heating coil using Litz wire, the degree of freedom in shape is high, and it is possible to form a curved portion 26 having a small diameter. Therefore, a conductor pattern can be formed up to the center of the coil portion 11. As a result, uneven heating due to insufficient heating at the center of the heated object 200 having an oval bottom surface can be suppressed.

[0042] Embodiment 2. The configuration of the induction heating coil 300 of the second embodiment will be described. In the second embodiment, differences from the first embodiment will be described in detail, and detailed descriptions of configurations similar to those described in the first embodiment will be omitted. FIG. 6 is a plan view showing a configuration example of the induction heating coil 300 according to the second embodiment. FIG. 6 is a plan view when the induction heating coil 300 is viewed from above in the vertical direction (opposite to the Y-axis arrow direction) in FIG. 1.

[0043] As shown in FIG. 6, the coil portion 11 is configured by a pattern in which a conductor 18 is wound a plurality of times in a spiral shape on the substrate 10 around an axis axs perpendicular to the surface of the substrate 10. In FIG. 6, when the coil portion 11 is viewed from above in the vertical direction (opposite to the Y-axis arrow direction), the outer shape of the pattern of the coil portion 11 is a rectangle. FIG. 7 is a diagram showing the pattern of the coil portion 11 extracted from the induction heating coil 300 shown in FIG. 6. The broken line shown in FIG. 7 indicates the outer shape of the pattern of the coil portion 11. As shown in FIG. 7, when a line is drawn along the outermost periphery of the pattern of the coil portion 11 to surround the coil portion 11, the outer shape of the pattern becomes a rectangle.

[0044] The outer shape of the pattern of the coil portion 11 shown in FIG. 6 is approximately square, but it may be a rectangular shape with different vertical and horizontal lengths. Further, FIG. 6 shows the case where the outer shape of the pattern of the coil portion 11 is a quadrilateral, but the shape of the pattern is not limited to a quadrilateral and may be a polygon such as a pentagon or a hexagon. Further, the number and positions of the magnetic plates 13 are not limited to the configuration example shown in FIG. 6. FIG. 6 shows the case where a plurality of magnetic plates 13 are radially arranged so as to be orthogonal to each side at the center of each side of the polygon. However, for example, a plurality of magnetic plates 13 may be radially arranged so as to overlap each vertex of the polygon.

[0045] The straight lines axL5, axL6, and asm3 shown in FIG. 7 are virtual lines parallel to the XZ plane and passing through the axis axs. The straight lines axL5 and axL6 are symmetry axes that divide the pattern of the coil portion 11 into line symmetry. On the other hand, the straight line asm3 is an asymmetric axis that divides the pattern of the coil portion 11 asymmetrically. Thus, the polygonal coil portion 11 has an outer shape having an asymmetric axis. The straight lines axL5 and axL6 are examples of line symmetry axes, and the straight line asm3 is an example of an asymmetric axis.

[0046] According to the second embodiment, when the bottom surface shape of the object to be heated 200 is a polygon such as a quadrilateral, since the outer shape of the pattern of the coil portion 11 coincides with the bottom surface shape of the object to be heated 200, magnetic flux is interlinked by the coil portion 11 over the entire bottom surface of the object to be heated 200 and heat is generated. Thereby, uneven heating of the object to be heated 200 can be suppressed.

[0047] Further, since the induction heating coil 300 of the second embodiment is manufactured using a manufacturing technique similar to that of a printed wiring board, it has a higher degree of freedom in shape than a conventional heating coil using Litz wire and can form a curve with a small diameter. Therefore, for the coil portion 11 having a polygonal outer shape of the pattern, the pattern near each vertex can be formed along the angle of the vertex. Thereby, in the object to be heated 200 having a polygonal bottom surface, uneven heating due to insufficient heating near each vertex can be suppressed.

[0048] Embodiment 3. The configuration of the induction heating coil 300 according to Embodiment 3 will be described. In Embodiment 3, the differences from Embodiments 1 and 2 will be described in detail, and the detailed description of the same configuration as that described in Embodiments 1 and 2 will be omitted. FIG. 8 is a plan view showing a configuration example of the induction heating coil 300 according to Embodiment 3. FIG. 8 is a plan view when the induction heating coil 300 is viewed from above in the vertical direction (opposite to the Y-axis arrow) in FIG. 1.

[0049] As shown in FIG. 8, the coil part 11 is configured in a pattern in which a conductor 18 is wound a plurality of times in a spiral shape on the substrate 10 around an axis axs perpendicular to the surface of the substrate 10. In FIG. 8, when the coil part 11 is viewed from above in the vertical direction (opposite to the Y-axis arrow) of the induction heating coil 300, the outer shape of the pattern of the coil part 11 is a waveform in which concave portions and convex portions are alternately arranged along the circumferential direction. FIG. 9 is a diagram showing the pattern of the coil part 11 extracted from the induction heating coil 300 shown in FIG. 8. The broken line shown in FIG. 9 indicates the outer shape of the pattern of the coil part 11. As shown in FIG. 9, when a line is drawn to surround the coil part 11 along the outermost circumference of the pattern of the coil part 11, the outer shape of the pattern becomes a waveform in which concave portions and convex portions are alternately arranged in the circumferential direction.

[0050] The straight lines axL7, axL8, and asm4 shown in FIG. 9 are virtual straight lines parallel to the XZ plane and passing through the axis axs. The straight lines axL7 and axL8 are symmetry axes that divide the pattern of the coil part 11 symmetrically. In contrast, the straight line asm4 is an asymmetric axis that divides the pattern of the coil part 11 asymmetrically. Thus, the waveform coil part 11 has an outer shape having an asymmetric axis. The straight lines axL7 and axL8 are an example of symmetry axes, and the straight line asm4 is an example of an asymmetric axis.

[0051] Note that FIGS. 8 and 9 show six cases where the pattern of the coil portion 11 is a corrugated shape formed by a combination of concave and convex portions. However, the number and size of the corrugated shapes are not limited to the configuration examples shown in FIGS. 8 and 9. Also, the number and position of the magnetic plates 13 are not limited to the configuration example shown in FIG. 8. For example, a configuration in which the magnetic plates 13 are arranged at each of the convex and concave portions of all the corrugated shapes of the coil portion 11 may be employed, or a configuration in which the magnetic plates 13 are arranged at the convex or concave portions of each corrugated shape may be employed.

[0052] Next, the effects of the induction heating coil 300 according to the third embodiment will be described with reference to FIGS. 10 to 13. FIG. 10 is a schematic cross-sectional view for explaining the flow of magnetic flux in the induction heating coil 300 according to the third embodiment. FIG. 10 is a schematic cross-sectional view taken along line A-A in FIG. 8. FIG. 11 is a plan view for explaining the distribution of magnetic flux in the induction heating coil 300 according to the third embodiment. The pattern of the coil portion 11 is virtually divided into three regions. Among the three regions, the innermost region is referred to as the inner peripheral portion 22, the outermost region is referred to as the outer peripheral portion 24, and the region between the inner peripheral portion 22 and the outer peripheral portion 24 is referred to as the intermediate portion 23.

[0053] FIG. 12 is a plan view for explaining the distribution of magnetic flux in the induction heating coil 350 of the comparative example. The induction heating coil 350 includes a substrate 10, a coil portion 111, and a shield ring 12. As shown in FIG. 12, the coil portion 111 is configured by a pattern in which a conductor is wound a plurality of times in a spiral shape on the substrate 10 around an axis axs perpendicular to the surface of the substrate 10. The pattern of the coil portion 111 is virtually divided into three regions: an inner peripheral portion 122, an intermediate portion 123, and an outer peripheral portion 124. Note that although the induction heating coil 350 has a magnetic plate 13, the magnetic plate 13 is not shown in FIG. 12.

[0054] FIG. 13 is a diagram showing the pattern of the coil portion 111 extracted from the induction heating coil 350 of the comparative example shown in FIG. 12. The outer shape of the pattern of the coil portion 111 of the induction heating coil 350 of the comparative example is circular as shown in FIG. 13. The straight lines axL9 to axL11 shown in FIG. 13 are virtual lines parallel to the XZ plane and passing through the axis axs. The straight lines axL9 to axL11 are examples of the symmetry axes that divide the pattern of the coil portion 111 into line symmetry. The coil portion 111 does not have an axis that divides the pattern asymmetrically.

[0055] Regarding the coil portion 11 of the induction heating coil 300, among a plurality of turns with the axis axs as the center of the spiral, the region of the conductor 18 for one round is referred to as a turn. That is, the coil portion 11 is composed of a plurality of turns being continuous. When a high-frequency current is supplied from the inverter circuit 6 to the coil portion 11, as shown in FIG. 10, magnetic fluxes 14 are generated around each turn of the coil portion 11. At this time, the magnetic fluxes 14 generated in each turn are superimposed, and a synthetic magnetic flux 15 is formed. Among a plurality of turns arranged continuously at regular intervals in the radial direction, the synthetic magnetic fluxes 15 of the inner peripheral portion 22 and the outer peripheral portion 24 are added to the synthetic magnetic flux 15 of the intermediate portion 23, and the magnetic flux in the intermediate portion 23 becomes larger than that in the outer peripheral portion 24. That is, for a plurality of turns arranged continuously at regular intervals in the radial direction, the heating power is large in the intermediate portion 23 and small in the outer peripheral portion 24.

[0056] As described with reference to FIG. 10, the coil portion 11 of the third embodiment has a greater heating power at the intermediate portion 23 shown in FIG. 11. Also, for the induction heating coil 350 of the comparative example shown in FIG. 12, the heating power at the intermediate portion 123 is greater than that at the outer peripheral portion 124, but the coil portion 11 of the third embodiment has a longer length per turn compared to the coil portion 111 of the comparative example. Therefore, the area of the intermediate portion 23, which is the region with strong heating power, becomes larger than the area of the intermediate portion 123 of the comparative example. Further, since the outer shape of the pattern of the coil portion 111 of the induction heating coil 350 of the comparative example is circular, regions with high heating power are not formed near the inner peripheral portion 122 and the outer peripheral portion 124 of the coil portion 111. On the other hand, since the pattern of the coil portion 11 of the third embodiment has a corrugated outer shape, concave portions are formed on the inner peripheral portion 22 side and convex portions are formed on the outer peripheral portion 24 side compared to the case where the pattern is circular. That is, with respect to the intermediate portion 123 of the comparative example, the coil portion 11 expands the regions with strong heating power to a part closer to the center than the intermediate portion 123 and a part outside the intermediate portion 123. Therefore, regions with high heating power are formed throughout the coil portion 11. Thereby, uneven heating of the object to be heated 200 can be suppressed.

[0057] Also, since the induction heating coil 300 of the third embodiment is manufactured using a manufacturing technique similar to that of a printed wiring board, it has a higher degree of freedom in shape and can form curves with a smaller diameter compared to conventional heating coils using Litz wire. Therefore, for the coil portion 11, it is possible to form a detailed corrugated pattern. Thereby, the coil portion 11 can be arranged over the entire bottom surface of the object to be heated 200, and uneven heating can be suppressed.

[0058] Embodiment 4. The configuration of the induction heating coil 300 of the fourth embodiment will be described. In the fourth embodiment, differences from the first to third embodiments will be described in detail, and detailed descriptions of configurations similar to those described in the first to third embodiments will be omitted. FIG. 14 is a plan view showing a configuration example of the induction heating coil 300 according to the fourth embodiment. FIG. 14 is a plan view of FIG. 1 when the induction heating coil 300 is viewed from above in the vertical direction (opposite to the Y-axis arrow) of the induction heating coil 300.

[0059] The coil part 11 of the induction heating coil 300 according to the fourth embodiment is composed of two divided coils having different types of outer shapes of the pattern. Here, different types of outer shapes of the pattern mean different geometric figures. For example, a coil part with a circular outer shape and a coil part with a square outer shape have different types of outer figures. The two divided coils are the coil part 25a and the coil part 25b. The coil part 25a is provided on the axis axs side. The coil part 25b is provided outside the coil part 25a. The outer shape of the pattern of the coil part 25a is circular. The outer shape of the pattern of the coil part 25b is square. Since the coil part 25a is circular, it has an outer shape without an axis of symmetry. On the other hand, since the coil part 25b is square, it has an outer shape with an axis of symmetry.

[0060] In the fourth embodiment, the case where the number of divided coils constituting the coil part 11 is two has been described, but the number of divided coils is not limited to two, and two or more are sufficient. FIG. 14 shows a case where the outer shape of the coil part 25a is circular and the outer shape of the coil part 25b is a polygon such as a square, but the combination of the types of outer shapes is not limited to the configuration example shown in FIG. 14. For example, the outer shape of the coil part 25a may be a polygon and the outer shape of the coil part 25b may be circular. The combination of the types of outer shapes of the plurality of divided coils may be any combination of arbitrarily selecting a plurality of types from the outer shape of the coil part 11 and the circular shape described in the first to third embodiments. Further, two divided coils having different types of outer shapes may be provided on each of the two surfaces of the substrate 10. Also, the number and arrangement of the magnetic plates 13 are not limited to the configuration example shown in FIG. 14.

[0061] According to the fourth embodiment, for the object to be heated 200 having a bottom surface shape of the same type as either one of the two types of outer shapes of the coil part 25a and the coil part 25b, magnetic flux is linked by the coil part 11 over the entire bottom surface and heat is generated. Thereby, uneven heating of the object to be heated 200 can be suppressed.

[0062] In addition, since the induction heating coil 300 of the fourth embodiment is manufactured using a manufacturing technique similar to that of a printed wiring board, even if the coil portion 11 is composed of a plurality of divided coils combined with different shapes, the plurality of divided coils can be manufactured in the same process. Therefore, the manufacturing process of the induction heating coil 300 can be simplified.

[0063] Embodiment 5. The configuration of the induction heating coil 300 of the fifth embodiment will be described. In the fifth embodiment, differences from the first to fourth embodiments will be described in detail, and detailed descriptions of configurations similar to those described in the first to fourth embodiments will be omitted. FIG. 15 is a plan view showing the surface of a configuration example of the induction heating coil 300 according to the fifth embodiment. FIG. 15 is a plan view of FIG. 1 when the induction heating coil 300 is viewed from above in the vertical direction (opposite to the Y-axis arrow) of the induction heating coil 300. FIG. 16 is a plan view showing the back surface of the induction heating coil 300 shown in FIG. 15.

[0064] The induction heating coil 300 of the fifth embodiment is a double-sided coil having a surface coil portion 11a which is a coil portion provided on the surface of the substrate 10 and a back surface coil portion 11b which is a coil portion provided on the back surface. The outer shape of the pattern of the surface coil portion 11a is circular. The outer shape of the pattern of the back surface coil portion 11b is polygonal. FIG. 16 shows the case where the outer shape of the pattern of the back surface coil portion 11b is a square. In the fifth embodiment, the induction cooker 100 has two inverter circuits 6. Each of the surface coil portion 11a and the back surface coil portion 11b is connected to a different inverter circuit 6 and operates individually under the control of the control device 7.

[0065] Note that the outer shape of the surface coil portion 11a shown in FIG. 15 is circular, and the outer shape of the back surface coil portion 11b shown in FIG. 16 is polygonal. However, the combination of the types of the outer shapes of the surface coil portion 11a and the back surface coil portion 11b is not limited to the configuration examples shown in FIGS. 15 and 16. The combination of the types of the outer shapes of the surface coil portion 11a and the back surface coil portion 11b may be any combination of arbitrarily selecting a plurality of types from the outer shapes of the coil portion 11 and circular shapes described in Embodiments 1 to 3. Further, the number and arrangement of the magnetic plates 13 are not limited to the configuration example shown in FIG. 16.

[0066] The operation of the induction heating coil 300 according to the fifth embodiment will be briefly described. When heating the object to be heated 200, the control device 7 operates the coil portion having an outer shape similar to the bottom surface shape of the object to be heated 200 among the surface coil portion 11a and the back surface coil portion 11b. For example, when the bottom surface shape of the object to be heated 200 is circular, the control device 7 supplies a high-frequency current from the inverter circuit 6 to the surface coil portion 11a among the surface coil portion 11a and the back surface coil portion 11b. Thereby, heating of the object to be heated 200 is started by the surface coil portion 11a. Note that the bottom surface shape of the object to be heated 200 may be automatically determined by the control device 7 that receives a detection signal from an object to be heated detection means (not shown) provided in advance in the induction heating cooker 100, or may be set in the control device 7 by the user via the operation unit 4.

[0067] According to the fifth embodiment, for the object to be heated 200 having the same bottom surface shape as either one of the two types of outer shapes of the surface coil portion 11a and the back surface coil portion 11b, magnetic flux interlinks the entire bottom surface and heat is generated. Thereby, uneven heating of the object to be heated 200 can be suppressed.

[0068] Further, since the induction heating coil 300 according to the fifth embodiment is manufactured using a manufacturing technique similar to that of a printed wiring board, two types of coil portions can be formed on one substrate 10. Compared with the case of manufacturing using two substrates 10, the number of components can be reduced, and the induction heating cooker 100 can be downsized and lightened.

[0069] Embodiment 6. The configuration of the induction heating coil 300 according to Embodiment 6 will be described. In Embodiment 6, differences from Embodiments 1 to 5 will be described in detail, and detailed descriptions of configurations similar to those described in Embodiments 1 to 5 will be omitted. FIG. 17 is a plan view showing a configuration example of the induction heating coil 300 according to Embodiment 6. FIG. 17 is a plan view when the induction heating coil 300 is viewed in the vertical direction (opposite to the Y-axis arrow direction) from above the induction heating coil 300 in FIG. 1. In FIG. 17, a solid line represents the surface coil portion 11e disposed on the surface of the substrate 10, and a broken line represents the back surface coil portion 11f disposed on the back surface of the substrate 10.

[0070] The induction heating coil 300 according to Embodiment 6 is a double-sided coil having a surface coil portion 11e provided on the surface of the substrate 10 and a back surface coil portion 11f provided on the back surface of the substrate 10. The surface coil portion 11e and the back surface coil portion 11f have the same type of pattern outer shape and the same number of turns. Also, the surface coil portion 11e and the back surface coil portion 11f are such that the terminals on the center side of the spiral pattern are electrically connected to each other, the terminals on the outer peripheral side of the spiral pattern are electrically connected to each other, and they are connected in parallel to one inverter circuit 6.

[0071] FIG. 18 is a schematic cross-sectional view of the induction heating coil 300 according to Embodiment 6. FIG. 18 is a schematic cross-sectional view taken along line B-B in FIG. 17. In FIG. 18, the magnetic plate 13 is not shown in the figure. The conductor 18e is a conductor forming the pattern of the surface coil portion 11e. The conductor 18f is a conductor forming the pattern of the back surface coil portion 11f.

[0072] Regarding the spiral surface coil portion 11e centered on the axis axs shown in FIG. 17, the length of the conductor 18e in the radial direction is defined as the conductor width D. Regarding the back surface coil portion 11f, the length of the conductor 18f in the radial direction is defined as the conductor width D * as well. As shown in FIG. 18, the relationship between the conductor width D of the surface coil portion 11e and the conductor width D * of the back surface coil portion 11f is D < D * .

[0073] Note that Fig. 17 shows the case where the outer shapes of the patterns of the front surface coil portion 11e and the back surface coil portion 11f are circular, but the outer shapes of the patterns are not limited to circular. For example, the outer shapes of the patterns of the front surface coil portion 11e and the back surface coil portion 11f may be shapes selected from a plurality of types of outer shapes of the coil portion 11 described in Embodiments 1 to 3. The number and positions of the magnetic plates 13 are not limited to the configuration example shown in Fig. 17. Figs. 17 and 18 show the configuration in which the pattern of the front surface coil portion 11e and the back surface coil portion 11f are arranged with the substrate 10 interposed therebetween such that the centers of the conductor widths D coincide with each other in each turn, but the configuration is not limited thereto. For example, in each turn, the front surface coil portion 11e and the back surface coil portion 11f may be provided on the substrate 10 such that the outer peripheral side ends of the conductor 18e and the outer peripheral side ends of the conductor 18f coincide with each other. Also, in each turn, the front surface coil portion 11e and the back surface coil portion 11f may be provided on the substrate 10 such that the inner peripheral side ends of the conductor 18e and the inner peripheral side ends of the conductor 18f coincide with each other. * The effect of the induction heating coil 300 of the sixth embodiment will be described. Generally, the resistance R [Ω] of a wiring is expressed by the formula R = ρ (L / S), where ρ [Ω·m] is the resistivity, L [m] is the length of the wiring, and S [m

[0074] is the cross-sectional area of the wiring. That is, the resistance R of the wiring is inversely proportional to the cross-sectional area S. When the cross-section of the wiring is rectangular, the cross-sectional area S is expressed by the formula S = (width of the wiring × height of the wiring). 2 In the sixth embodiment, let the cross-sectional area of the conductor 18e be Se and the resistance of the front surface coil portion 11e be Re. Also, let the cross-sectional area of the conductor 18f be Sf and the resistance of the back surface coil portion 11f be Rf. Since the heights of the conductor 18e and the conductor 18f are equivalent, D < D

[0075] * ​From this relationship, the relationship between the cross-sectional area Se and the cross-sectional area Sf is Se < Sf. Furthermore, for the surface coil portion 11e and the back surface coil portion 11f, the resistivity ρ and the wiring length L are common. Since the resistance R is inversely proportional to the cross-sectional area S, the relationship between the resistance Re and the resistance Rf is Re > Rf. That is, the resistance Rf of the back surface coil portion 11f is smaller than the resistance Re of the surface coil portion 11e.

[0076] In the sixth embodiment, since the surface coil portion 11e and the back surface coil portion 11f are connected in parallel to the inverter circuit 6, the value of the current flowing through the back surface coil portion 11f, which has a smaller resistance than the surface coil portion 11e, becomes larger. At this time, the Joule heat generated in the coil is proportional to the square of the current flowing through the coil. Therefore, a larger amount of Joule heat is generated in the back surface coil portion 11f than in the surface coil portion 11e, and the temperature rises more. In other words, since the Joule heat generated in the surface coil portion 11e is smaller than that in the back surface coil portion 11f, the temperature rise of the surface coil portion 11e is suppressed more than that of the back surface coil portion 11f.

[0077] As described with reference to FIG. 1, the induction heating coil 300 is disposed below the top plate 1. Therefore, in order to cool the surface coil portion 11e disposed on the surface of the induction heating coil 300, a space serving as an air passage is required between the top plate 1 and the upper surface of the induction heating coil 300. On the other hand, according to the sixth embodiment, since the temperature rise of the surface coil portion 11e can be reduced, the space serving as the air passage can be reduced. That is, the induction heating coil 300 can be disposed closer to the top plate 1, and the distance between the induction heating coil 300 and the top plate 1 can be reduced.

[0078] Normally, the effect of the magnetic flux generated in the coil portion on the object to be heated 200 becomes smaller as the distance between the object to be heated 200 and the coil portion increases. On the other hand, according to the sixth embodiment, the distance between the induction heating coil 300 and the top plate 1 can be reduced, and the amount of magnetic flux linked to the object to be heated 200 placed above the top plate 1 increases as the distance between the induction heating coil 300 and the top plate 1 decreases. Therefore, the heating efficiency can be improved.

[0079] Hereinafter, various aspects of the induction heating coil 300 and the induction heating cooker 100 of the present disclosure will be collectively described as appendices.

[0080] (Appendix 1) An induction heating coil for heating an object to be heated, a substrate having insulation, a coil portion provided parallel to the surface of the substrate and configured in a pattern in which a conductor is wound a plurality of times in a spiral shape around an axis perpendicular to the surface of the substrate, and the coil portion has an outer shape having an asymmetric axis, which is a virtual straight line passing through the center and parallel to the surface of the substrate and dividing the pattern asymmetrically, the outer shape is a figure represented by the virtual line connecting the end point and the start point so that no step is generated at the contact point between the end point and the start point of the virtual line drawn along the outermost periphery starting from the end portion of the outermost periphery of the pattern, Induction heating coil. (Appendix 2) The substrate has a front surface, which is a surface facing the object to be heated, and a back surface, which is a surface on the opposite side of the front surface, the coil portion is provided on each of the front surface and the back surface, The induction heating coil according to Appendix 1. (Appendix 3) a first coil portion that is the coil portion, a second coil portion connected to the first coil portion and disposed on the inner peripheral side or the outer peripheral side of the first coil portion, and the second coil portion has a pattern in which a conductor is wound a plurality of times in a spiral shape around an axis perpendicular to the surface of the substrate, the pattern of the first coil portion and the pattern of the second coil portion are different in the type of the outer shape, The induction heating coil according to Appendix 1 or 2. (Appendix 4) a surface coil portion that is the coil portion provided on the front surface, It has a back surface coil part which is the coil part provided on the back surface. The outer shape of the front surface coil part and the outer shape of the back surface coil part are of the same type of figure. The conductor width which is the length of the conductor in the radial direction of the back surface coil part is larger than the conductor width of the front surface coil part. The induction heating coil according to Supplementary Note 2. (Supplementary Note 5) The substrate has a front surface which is the surface facing the object to be heated and a back surface which is the surface on the opposite side of the front surface. A first coil part which is the coil part provided on one of the front surface or the back surface. It has a second coil part provided on the other of the front surface or the back surface. The second coil part has a pattern in which the conductor is wound multiple times in a spiral around an axis perpendicular to the surface of the substrate. The outer shape of the first coil part and the outer shape of the second coil part are of different types of figures. The induction heating coil according to Supplementary Note 1. (Supplementary Note 6) The outer shape of the coil part is an ellipse. The induction heating coil according to any one of Supplementary Notes 1 to 5. (Supplementary Note 7) The outer shape of the coil part is a figure in which a straight part and a curved part are combined. The induction heating coil according to any one of Supplementary Notes 1 to 5. (Supplementary Note 8) The outer shape of the coil part is a polygon. The induction heating coil according to any one of Supplementary Notes 1 to 5. (Supplementary Note 9) The outer shape of the coil part is a corrugated shape in which convex parts and concave parts are alternately arranged along the circumferential direction of the center. The induction heating coil according to any one of Supplementary Notes 1 to 5. (Supplementary Note 10) The thickness of the conductor is 1 time or more and 5 times or less the skin depth based on the skin effect of the conductor. The induction heating coil according to any one of Supplementary Notes 1 to 9. (Supplementary Note 11) An induction heating cooker comprising the induction heating coil according to any one of Supplementary Notes 1 to 10.

Explanation of Reference Signs

[0081] 1 Top plate, 2 Housing, 3 Heating port, 4 Operation unit, 5 Display unit, 6 Inverter circuit, 7 Control device, 10 Substrate, 11 Coil unit, 11a Surface coil unit, 11b Rear surface coil unit, 11e Surface coil unit, 11f Rear surface coil unit, 12 Shield ring, 13 Magnetic plate, 14 Magnetic flux, 15 Synthetic magnetic flux, 18, 18e, 18f Conductor, 21 Straight part, 22 Inner peripheral part, 23 Intermediate part, 24 Outer peripheral part, 25a, 25b Coil unit, 26 Curved part, 100 Induction heating cooker, 111 Coil unit, 122 Inner peripheral part, 123 Intermediate part, 124 Outer peripheral part, 200 Object to be heated, 300, 350 Induction heating coil, asm1 to asm4, axL1 to axL11 Straight lines, axs Axis.

Claims

1. An induction heating coil for heating an object to be heated, comprising a substrate having insulation properties, and a coil portion provided parallel to the surface of the substrate and configured in a pattern in which a conductor is wound multiple times in a spiral shape around an axis perpendicular to the surface of the substrate. The coil portion has an outer shape having an asymmetric axis, which is a virtual straight line parallel to the surface of the substrate and passing through the center and which divides the pattern asymmetrically. The outer shape is a figure represented by a virtual line connecting the end point and the start point, where the virtual line is drawn along the outermost periphery starting from the end portion of the outermost periphery of the pattern so that no step is generated at the contact point between the end point and the start point. Induction heating coil.

2. The substrate has a front surface, which is the surface facing the object to be heated, and a back surface, which is the surface on the opposite side of the front surface. The coil portion is provided on each of the front surface and the back surface. The induction heating coil according to claim 1.

3. A first coil portion that is the coil portion, and a second coil portion connected to the first coil portion and disposed on the inner peripheral side or the outer peripheral side of the first coil portion. The second coil portion has a pattern in which a conductor is wound multiple times in a spiral shape around an axis perpendicular to the surface of the substrate. The pattern of the first coil portion and the pattern of the second coil portion are different in the type of the outer shape. The induction heating coil according to claim 1 or 2.

4. A front surface coil portion that is the coil portion provided on the front surface, and a back surface coil portion that is the coil portion provided on the back surface. The outer shape of the front surface coil portion and the outer shape of the back surface coil portion are the same in the type of figure. The conductor width, which is the length of the conductor in the radial direction of the inner coil portion, is larger than the conductor width of the surface coil portion. The induction heating coil according to claim 2.

5. The substrate has a front surface that is a surface facing the object to be heated and a back surface that is a surface on the opposite side of the front surface. A first coil portion that is the coil portion provided on one of the front surface or the back surface, and a second coil portion provided on the other of the front surface or the back surface. The second coil portion has a pattern in which a conductor is wound a plurality of times in a spiral shape around an axis perpendicular to the surface of the substrate. The outer shape of the first coil portion and the outer shape of the second coil portion are different in the type of figure. The induction heating coil according to claim 1.

6. The outer shape of the coil portion is an ellipse. The induction heating coil according to claim 1 or 2.

7. The outer shape of the coil portion is a figure in which a straight portion and a curved portion are combined. The induction heating coil according to claim 1 or 2.

8. The outer shape of the coil portion is a polygon. The induction heating coil according to claim 1 or 2.

9. The outer shape of the coil portion is a waveform shape in which convex portions and concave portions are alternately arranged along the circumferential direction of the center. The induction heating coil according to claim 1 or 2.

10. The thickness of the conductor is 1 time or more and 5 times or less the skin depth based on the skin effect of the conductor. The induction heating coil according to claim 1 or 2.

11. An induction heating cooker including the induction heating coil according to claim 1 or 2.

Images