JPH0992453A - Induction heating device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make induction heating uniformly and at low cost a subject to be heated whose part to be heated constitutes a curved surface externally. SOLUTION: This device, placed on the bottom side of a wok 2 serving as a subject to be heated, comprises a heating coil 1, a conductive plate 3, and a ferrite core 7, etc. The coil surface of the heating coil 1 and the surface part of the conductive plate 3 are each shaped into a curved surface extending along the curved surface of the heated part (bottom side) of the wok 2, and are arranged so that their centers and circumferences are equally spaced from the heated part.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electromagnetic induction heating apparatus used in, for example, an electromagnetic cooker or a rice cooker, and more particularly, an electromagnetic induction heating apparatus for heating an object to be heated whose outer shape is a curved surface. The present invention relates to an improvement in the structure of a heating coil or the like for uniform heating in an induction heating device.

[0002]

2. Description of the Related Art As an application example of an electromagnetic induction heating apparatus for inductively heating an object to be heated, it has a heating coil in which a conducting wire such as a litz wire is wound in a spiral shape in a circular or rectangular shape from the center toward the outer periphery. An electromagnetic cooker and an electromagnetic induction type rice cooker are generally known. Also, in order to improve the heating distribution when using this type of electromagnetic induction heating device, a flat conductive plate is provided between the heating coil and the object to be heated (electromagnetic cooker).
Has been proposed by the present applicant (Japanese Patent Application No. 6-3106).
No. 75, etc.).

First, an electromagnetic induction heating device provided with a flat conductive plate will be described. FIG. 6 is a side view of a main part of an induction heating mechanism when the electromagnetic induction heating device is applied to a rice cooker. In the figure, reference numeral 11 is a flat heating coil, and 13 is a flat conductive plate. The rice cooker includes a rice cooker 8 made of, for example, a SUS magnetic material, and an insulating / waterproof container 9 for supporting the rice cooker 8. For the container 9, for example, a glass material or a ceramic material is used.
As the conductive plate 13, for example, an annular conductive plate having at least one slit connecting the outer peripheral edge and the inner peripheral edge, a spiral conductive plate, and a plurality of slits radially extending from the central hole toward the peripheral edge. A substantially disc-shaped conductive plate formed by connecting at least one slit part to its outer peripheral edge,
Etc. can be used. Further, the plurality of annular conductive plates having different diameters are concentrically arranged in the same plane at predetermined intervals, respectively, and the slit portions of the respective annular conductive plates are slits of other annular conductive plates adjacent to each other in the radial direction. A plurality of annular conductive plates formed in a portion relatively different from the portion, or a substantially disc-shaped conductive plate with a notch in which a slit-shaped notch portion is formed in the direction of the central hole from a predetermined portion of the outer peripheral edge of the substantially disc-shaped conductive plate. Etc. can also be used.

Specific examples of each conductive plate and the interaction between the conductive plate and the heating coil will be described below with reference to FIGS. 7 to 13. FIG. 7A is a front view of the annular conductive plate 13a having a single unit having the slit portion 14, and FIG. 7B is a sectional view taken along the line AA. As is clear from this figure, the conductive plate 13a
Are arranged in parallel at a predetermined distance from the coil surface of the flat heating coil 11. Further, FIG. 8 is a front view of the annular conductive plate 13b in which the slit portions 14a, 14b, 14c are formed at three locations.

The ring-shaped conductive plates 13a, 13 having such a structure
In the case of using b, when a high frequency current I1 is passed through the heating coil 11, an induction magnetic field is generated on the coil surface, and at the same time, the induction current I is generated in each annular conductive plate 13a, 13b in a direction of canceling the induction magnetic field. ₂ flows. Here, the induced current I ₂ tends to flow in the opposite direction to the high frequency current I ₁ of the heating coil 11, but the slit portions 14, 14a, 14b,
Since it is cut off by 14c, it is not possible to go around the entire conductive plate.
For this reason, the induced current I ₃ which is a large current collected in the vicinity of the slit portions 14, 14a, 14b, 14c moves in the inner peripheral edge of the conductive plate in the opposite direction to the induced current I ₂ , that is, the heating coil 1
1 flows in the same direction as the high frequency current I ₁ . in this case,
The induction current I ₂ flowing through the outer peripheral edge of the conductive plate is generated by the heating coil 11
Since it is in the opposite direction to the high frequency current I _{1 of the above} , it is canceled. Therefore, the object to be heated cannot be induction-heated in this portion, but since the high-frequency current I ₁ and the induction current I ₃ are in the same direction near the inner peripheral edge of the conductive plate, the magnetic field generated by these currents is strengthened. Therefore, a large induction magnetic field is generated near the inner peripheral edge of the conductive plate. As a result, the same effect as when the coil current components of the individual conductive plate widths are aggregated and generated near the inner peripheral edge of the conductive plate is obtained. As a result, a part of the current in the middle portion (the middle portion between the central portion and the peripheral portion) of the heating coil 11 where the magnetic field is relatively strong is selectively moved to the weak magnetic field portion of the central portion of the heating coil 11, and It is possible to make the heating distribution of the heated material uniform.

In FIG. 9A, three annular conductive plates having different diameters are concentrically arranged in the same plane, and slit portions 14d, 14 connecting the outer peripheral edge and the inner peripheral edge of each annular conductive plate.
e and 14f are front views of a plurality of annular conductive plates 13c formed at positions relatively different from the slits of other adjacent annular conductive plates, and FIG. 7B is a sectional view taken along the line BB. The interaction between the high frequency current I ₁ and the induced currents I ₂ and I ₃ in the conductive plate having such a structure is basically as described above.

10 and 11 are front views each showing an example of a spiral conductive plate. The conductive plate 13d shown in FIG.
The slit portions 14g, 14h shown in FIG.
14i, the adjacent conductive plates are joined in a stepwise manner to form one spiral conductive plate. In addition, the conductive plate 13e shown in FIG. 11 does not have three annular conductive plates joined stepwise, but a conductive plate element having a required width is integrally formed in a round spiral shape with a required gap to form a spiral conductive plate. I am configuring. The interaction between the high frequency current I ₁ and the induced currents I ₂ and I ₃ in this case is also as described above.

12 and 13 are front views showing examples of the configuration of a substantially disk-shaped conductive plate 13f and a notched substantially disk-shaped conductive plate 13g, respectively. The substantially disk-shaped conductive plate 13f shown in FIG.
Is formed by cutting out from the outer peripheral edge of the disk-shaped conductive plate in the direction of the central portion thereof to form a central hole portion, and by notching a plurality of slit portions 14j radially from the central hole portion in the peripheral portion direction by a predetermined length. Is forming. Conductive plate 1 having such a configuration
When 3f is used, when a high frequency current I _{1 is} passed through the heating coil 11, an induction current I ₂ is induced near the outer peripheral edge of the conductive plate. This induced current I ₂ changes its direction at the end near the slit 14j connecting the outer peripheral edge and the central hole, and the induced current I _{4 in the} direction of the central hole and the induced current I _{3 in the} same direction as the high frequency current I _1. , An induction current I ₅ in the outer peripheral direction is sequentially circulated along the ends around each slit 14j. At this time, the induced current I ₃ strengthens the induced magnetic field due to the high frequency current I ₁ , while the induced currents I ₄ and I ₅ do not cancel the induced magnetic field due to the high frequency current I _1, so weaken the induced magnetic field in the vicinity of its intermediate portion. There is no. As a result, only the induction magnetic field around the central hole becomes relatively strong, and the heating distribution in the object to be heated is made uniform.

On the other hand, the substantially disk-shaped conductive plate 13g with a notch shown in FIG. 13 is a disk-shaped conductive plate 13f having the structure shown in FIG. The notch 15 having a shape of a circle is formed. When such a conductive plate 13g is used, the induced current I ₂ flowing in the circumferential direction of the outer peripheral edge of the conductive plate is generated by each notch 1
At the ends near 5, the induced current I in the direction of the central hole
_6. Circulating while changing the direction, like the induced current I _{7 in} the peripheral direction. Since these induction currents I ₆ and I ₇ do not weaken the induction magnetic field by the heating coil 11,
By appropriately changing the number of the cutout portions 15, the strength of the magnetic field near the outer peripheral edge can be arbitrarily adjusted.

[0010]

As described above, by disposing the conductive plates 13a to 13g between the heating coil 11 and the object to be heated, the heating distribution during induction heating can be made uniform. However, for example, a flat heating coil 11
In the conventional electromagnetic cooker configured by including the flat plate-shaped conductive plate 13 (13a to 13g), the desired effect is obtained when the outer shape of the portion to be heated is flat, for example, a wok. As described above, in the case of an object to be heated whose outer shape of the heating target portion is a curved surface, the magnetic flux interlinking the heating target portion is directed from the center portion of the bottom surface to the peripheral portion mainly due to the difference in distance from the coil surface of the heating coil. The heating temperature at the center is the highest and the temperature at the periphery is extremely low because it decreases sharply as it goes on. In particular, if a wok requires quick and strong heating, a thin iron plate is generally used, but if induction heating is performed using a conventional electromagnetic cooker, a thin iron plate pan is used for the above reasons. Is more uneven than the thick pot,
There is a problem that it is not suitable for cooking which requires uniform heating.

In the case of a rice cooker, as shown in FIG.
By making the outer shape of the bottom surface of the rice cooker, which is the heating target portion, flat, the problem of uneven heating temperature can be solved. However, in the rice cooker having the rice cooker having the shape shown in FIG. 6, only the bottom of the rice cooker is heated, and it is difficult to heat the entire rice cooker such as the so-called “cooking”, which is necessary to cook delicious rice. As a countermeasure for this, it is conceivable to make the outer shape of the bottom surface of the rice cooker a large curved surface shape, and make the coil surface of the heating coil a curved surface shape that covers the outer shape of the bottom surface of the rice cooker, but simply changing the shape of the heating coil As will be described later, the central portion of the bottom surface of the rice cooker and the side surface of the rice cooker are weakly heated, and conversely, the intermediate portion is heated in a so-called donut shape and uniform heating cannot be performed.
Therefore, conventionally, as a structure of a rice cooker, a layer made of a magnetic material such as iron or stainless steel to be directly heated is further laminated with a layer having excellent thermal conductivity such as aluminum or copper, and the temperature of the rice cooker is increased. However, there has been a problem that material costs and processing costs cannot be reduced.

The object of the present invention is to solve the above problems,
In an electromagnetic induction heating device used for an electromagnetic cooker, a rice cooker, or the like, it is to uniformly and inexpensively heat an object to be heated whose outer shape of a heating target portion is a curved shape.

[0013]

Means for Solving the Problems A first method for solving the above problems is described below.
The electromagnetic induction heating device of the invention is a device for inductively heating an object to be heated, the outer shape of a heating target part of which is a curved surface, and a heating coil having a coil surface formed by spirally winding a conductive wire,
An annular conductive plate having a front surface directed to the heating target portion and a rear surface directed to the coil surface of the heating coil, and the annular conductive plate has at least a slit connecting an outer peripheral edge and an inner peripheral edge. One is formed, and the shape of the surface portion of the annular conductive plate and the shape of the coil surface of the heating coil are curved shapes along the outer shape of the heating target portion, respectively. In the electromagnetic induction heating device having such a configuration, the distance between the coil surface of the heating coil and the surface of the annular conductive plate and the portion to be heated is not only the central portion,
It is even in the peripheral area. Therefore, the magnetic field based on the high frequency current flowing in the heating coil and the induced current flowing in the annular conductive plate uniformly acts on the central portion and the peripheral portion of the heating target portion. Further, of the induced current generated in the annular conductive plate, the current flowing along the outer peripheral edge of the conductive plate is blocked by the slit portion and cannot be further circulated.
The direction changes at the end near the slit, and the flow flows toward the other peripheral edge. And the current flowing along the inner peripheral edge of the conductive plate is
It is in the opposite direction to the induced current along the outer peripheral edge, and flows intensively near the center. This current causes the magnetic field in the vicinity of the center of the annular conductive plate to be relatively stronger than in the vicinity of the periphery. As a result, the central portion of the heating target portion of the object to be heated is heated more strongly, and the temperature difference from the intermediate portion is reduced.

The electromagnetic induction heating apparatus of the second invention is the above-mentioned first invention.
In the configuration of the invention, the plurality of annular conductive plates having different diameters are concentrically arranged at predetermined intervals, and a slit portion connecting the outer peripheral edge and the inner peripheral edge of each annular conductive plate is provided next to another annular ring. It is characterized in that it is formed at a portion relatively different from the slit portion of the conductive plate. In the electromagnetic induction heating device having such a configuration, further, the induced current flowing in the outer peripheral edge of each annular conductive plate flows in a direction to cancel the high frequency current of the heating coil, while the current flowing in the inner peripheral edge strengthens the high frequency current. Act on. Therefore, the heating temperature distribution in the heating target portion can be arbitrarily adjusted by appropriately setting the width (radial length) of each annular conductive plate and the arrangement interval thereof. In addition, since the direction of current flowing in the inner or outer peripheral edge of one annular conductive plate and the direction of current flowing in the outer peripheral edge or inner peripheral edge of the adjacent annular conductive plate are always opposite, a rapid temperature rise or fall. Is suppressed and the heating temperature distribution becomes uniform.

The electromagnetic induction heating apparatus of the third invention is an electromagnetic induction heating apparatus for inductively heating an object to be heated whose outer shape of the heating target portion is a curved surface, and the conductive wire is spirally wound to form a coil surface. A heating coil, and a spiral conductive plate whose front surface is directed to the heating target portion and whose rear surface is directed to the coil surface of the heating coil. The shape of the coil surface of the coil is a curved surface shape along the outer shape of the heating target portion. In the electromagnetic induction heating device having such a configuration, the magnetic field based on the high frequency current flowing in the heating coil and the induction current flowing in the spiral conductive plate element acts uniformly on the central portion and the peripheral portion of the heating target portion. Since the induced currents flowing through the respective conductive plate elements act in a complex manner to flow into the vicinity of the central portion thereof, the magnetic field at the flowing-in portion is relatively strengthened and the heating temperature at the heating target portion becomes uniform.

The electromagnetic induction heating apparatus of the fourth invention is an electromagnetic induction heating apparatus for inductively heating an object to be heated whose outer shape of a heating target portion is a curved surface, and a conducting wire is wound in a spiral shape to form a coil surface. The heating coil, and a conductive plate having a front surface portion directed to the heating target portion and a back surface portion directed to the coil surface of the heating coil, and the conductive plate,
A central hole portion, a plurality of slit portions extending from the central hole portion in a peripheral direction, and at least one connecting cutout portion connecting the central hole portion and the outer peripheral edge are formed, and the conductive plate The shape of the surface portion and the coil surface of the heating coil is
Each of them has a curved surface shape along the outer shape of the heating target portion. In the electromagnetic induction heating device having such a configuration, the magnetic field based on the high-frequency current flowing in the heating coil and the induction current flowing in the conductive plate uniformly acts on the central portion and the peripheral portion of the heating target portion, and The induced current flowing in the circumferential direction is blocked by the slit portion connecting the outer peripheral edge of the conductive plate and the central hole portion, and the conductive plate cannot be further circulated in the circumferential direction. It flows in the direction of the section. This current further flows along the edges around the radially formed slits, but the current flowing from the central hole of the conductive plate toward the outer peripheral edge and the current in the opposite direction are the high-frequency current of the heating coil. Since the magnetic field due to the magnetic field is not canceled, only the magnetic field around the central hole portion is relatively strengthened, and the object to be heated can be uniformly heated.

In the electromagnetic induction heating apparatus of the fifth invention, in the structure of the fourth invention, the conductive plate has a shape in which a slit-like cutout portion is formed from a predetermined portion of the outer peripheral edge thereof toward the central hole portion. Is characterized by. In the electromagnetic induction heating device having such a configuration, the induction current flowing in the outer peripheral edge of the conductive plate in the circumferential direction circulates while sequentially changing its direction at the ends near the slit-shaped notches. Therefore, it is possible to adjust the strength of the magnetic field near the outer peripheral edge by appropriately changing the number of the cutout portions.

In the constructions of the first to fifth inventions, more preferably, an electromagnetic induction heating device is constructed by arranging a ferromagnetic material at a predetermined portion of the center of the coil surface of the heating coil. With this configuration, the magnetic field at the central portion of the coil surface, that is, the heating target portion becomes relatively stronger than that at the peripheral portion, and a more uniform heating distribution can be obtained.

[0019]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. (First Embodiment) First, an embodiment in which the electromagnetic induction heating device of the present invention is applied to an electromagnetic cooker to induction-heat a wok is described with reference to FIGS.

FIG. 1 (a) is a sectional view of the main part of the induction heating mechanism in this embodiment, and FIG. 1 (b) is an actual measurement diagram (graph) of the heating distribution on the bottom surface of the wok. FIG.
Referring to (a), a heating coil 1, a conductive plate 3, and a wok 2 formed by spirally winding a lead wire such as a litz wire on the bottom surface (heating symmetrical portion) of the wok 2 which is the object to be heated.
An electromagnetic cooker including a ferromagnetic material, such as a ferrite core 7, is provided for promoting heating of the central portion of the bottom surface of the. Reference numeral 4 is an insulating waterproof plate made of a glass material or a ceramic material for preventing moisture from the wok 2 on the heating coil 1, the conductive plate 3, and the like. Further, reference numeral 5 is a non-magnetic pot frame for fixing the wok 2 on the Chinese range table 6, and the wok frame 5 supports the wok 2.

The heating coil 1 has a curved shape along the outer shape of the bottom surface of the wok 2, and a high frequency power source (not shown) is connected to its end conductor. The conductive plate 3 is shown in FIG.
One of the conductive plates having the configuration illustrated in FIG. 13 is formed into a curved shape along the outer shape of the bottom surface of the wok 2, the back surface of which is oriented toward the coil surface of the heating coil 1, and the surface of which is the above-mentioned waterproof. It is joined to the back surface of the plate 4 (the surface portion that faces the coil surface). In this embodiment, the case where the conductive plate (13a) having the configuration shown in FIG. 7 is used will be described.

In the electromagnetic cooker having the above structure, the heating coil 1
The distance from the coil surface and the surface portion of the conductive plate 3 becomes substantially uniform over the entire outer bottom surface of the wok 2. for that reason,
When power is supplied to the heating coil 1 from the high frequency power source through the end conductors, a magnetic field based on the high frequency current flowing in the heating coil 1 and the induced current flowing in the conductive plate 3 acts on the entire wok 2 to cause it to flow. Induction heating with almost uniform strength. The interaction between the high frequency current and the induced current corresponding to the type of the conductive plate 3 is as described above.

Next, for convenience, an apparatus having a mechanism similar to the induction heating mechanism of this embodiment is shown in FIGS. 2 and 3, and FIG.
The operational comparison with that of the configuration will be made. Figure 2 (a) shows
FIG. 2B is a cross-sectional view of a main part when the wok 2 is heated by an electromagnetic cooker having the same configuration as that of FIG. 1A except that the conductive plate 3 is omitted. FIG. 2B shows the wok in this case. It is the measurement figure (graph) of the heating distribution in the bottom face. Also, FIG.
In (a), the ferrite core 7 is arranged at the center of the conventional flat heating coil 11, and
FIG. 3B is a cross-sectional view of a main part when the wok 2 is heated by an electromagnetic cooker having a flat conductive plate 13 arranged on the side of the object to be heated, and FIG. 3B is a bottom view of the wok in this case. It is an actual measurement figure (graph) of heating distribution. Hereinafter, the structure shown in FIG. 1 (a) is referred to as an invention product A, the structure shown in FIG. 2 (a) is referred to as a comparative product B, and the structure shown in FIG. 3 (a) is referred to as a comparative product C. explain.

The heating distributions on the bottom surface of the wok 2 according to the invention product A, the comparative product B, and the comparative product C are shown in FIGS.
When compared with (b) and FIG. 3 (b), in the product A of the present invention, there is little decrease in the heating temperature in the central portion C and the peripheral portion P of the wok 2 and the entire bottom surface of the wok 2 is uniformly heated. be able to. On the other hand, in comparative product B, wok 2
The heating temperature in the central portion C and the peripheral portion P of the bottom surface is extremely low, and only the intermediate portion M is strongly heated, which is a so-called donut-shaped non-uniform heating distribution. This is the center C
This is because the number of magnetic flux linkages in the peripheral portion P is relatively smaller than the number of magnetic flux linkages in the intermediate portion M, and as a result, the heating temperature of the central portion C and the peripheral portion P is relatively low. Further, in the case of the comparative product C, the temperature of the central portion C is the highest, and the heating temperature is lowered toward the peripheral portion P, which is a so-called non-uniform heating distribution. Since the heating coil 11 and the conductive plate 13 are flat plates, the magnetic flux decreases as the distance from the heating coil 11 and the conductive plate 13 to the bottom surface of the wok 2 increases as it goes to the periphery of the wok 2. As a result, it is considered that the heating temperature is lowered.

As described above, according to the product A of the present invention, the comparative product B in which the coil surface of the heating coil is simply formed into a curved shape, or the flat heating coil, the ferrite core, and the flat conductive plate are used. A more uniform heating distribution, which cannot be obtained by the comparative product C, is obtained. Therefore, it becomes possible to quickly and strongly perform uniform heating using a thin wok made of an iron plate, and the conventional problems of this kind are solved. When fine adjustment of the heating distribution is necessary, instead of the conductive plate 13a having the configuration shown in FIG. 7, for example, a conductive plate 13g having the configuration shown in FIG. 13 is used, and the number of slit portions 15 is changed as necessary. It is good to increase or decrease.

(Second Embodiment) Next, an embodiment in which the electromagnetic induction heating device of the present invention is applied to a rice cooker to induction-heat a rice cooker will be described with reference to FIGS. 4 and 5.

FIG. 4 (a) is a sectional view of the main part of the induction heating mechanism in this embodiment, and FIG. 4 (b) is an actual measurement graph (graph) of the heating distribution in the rice cooker. Figure 4 (a)
In, the bottom side of the rice cooker 8 and the container 9 which are the objects to be heated
An electromagnetic induction heating device including a heating coil 1a, a conductive plate 3, and a ferrite core 7 which is a ferromagnetic material is provided on the bottom surface side of the. The heating coil 1a, the conductive plate 3, and the ferrite core 7 are the same as the heating coil 1 shown in FIG.
It is similar to the conductive plate 3 and the ferrite core 7.
Usually, the surface portion of the conductive plate 3 is used by being joined to the bottom surface of the container 9. The operation of the rice cooker having such a configuration is basically the same as that of the electromagnetic cooker of the first embodiment.

Next, an apparatus having a mechanism similar to the induction heating mechanism of the present embodiment is shown in FIG. 5, and a functional comparison with that of the configuration of FIG. 4 will be made. FIG. 5A is a sectional view of an essential part of an induction heating mechanism having the same configuration as that of FIG. 4A except that the conductive plate 3 and the ferrite core 7 are omitted, and FIG. It is an actual measurement figure of the heating distribution in a rice cooker. Hereinafter, the structure shown in FIG.
The structure shown in (a) will be described as a comparative product E.

FIG. 4 shows the heating distributions of the product D of the present invention and the comparative product E.
When comparing FIG. 5B and FIG. 5B, the present invention product D
Thus, the heating temperature in the central portion C and the peripheral portion P of the rice cooker 8 is small, and the entire rice cooker 8 can be heated uniformly. As a result, it is possible to easily realize a heating distribution such as "cooking a furnace". On the other hand, in the case of the comparative product E,
The central portion C and the peripheral portion P are weakly heated, and only the middle portion M is strongly heated, so that a so-called donut-shaped heating distribution is obtained, so that the entire rice cooker 8 cannot be uniformly heated. The reason for this is considered to be the same as in the case of the induction heating mechanism configured as shown in FIG.

As described above, according to the product D of the present invention, a more uniform heating distribution can be obtained, which cannot be obtained by the comparative product E in which the coil surface of the heating coil is simply formed into a curved shape. Further, unlike the rice cooker using the flat heating coil 11 and the flat conductive plate 13 as shown in FIG. 6, instead of heating the lower bottom surface of the rice cooker 8, the entire rice cooker is uniformly and efficiently. Since it can be heated, there is no need to disperse the temperature of the rice cooker by pasting a layer with more excellent thermal conductivity on the layer of magnetic material as in the past, reducing the material cost and processing cost and making it widely practical Can be planned.

Although the present invention has been described with reference to a plurality of embodiments, the present invention is not limited to the above examples.
Various design changes are possible without changing the gist. For example, as shown in FIGS. 7 to 13, the conductive plate 3 may have an annular shape, a spiral shape, or a substantially disc shape, and may also be formed into an angular shape, and the number of slit portions may be the same as that of the heating coil. It may be arbitrarily increased or decreased depending on the number of windings or the shape of the part to be heated. Further, the conductive plate 3 does not necessarily have to be formed into a curved surface shape by one conductive plate, and may be formed by combining a plurality of flat plate-shaped conductive plates into a curved surface shape as a whole. In this case, even if there is a slight difference in distance between the surface part of the conductive plate and the central part and the peripheral part of the part to be heated, if the surface part of the conductive plate is in a shape substantially along the outer shape of the part to be heated, it is expected. Therefore, precise shape adjustment is not necessary.

[0032]

As is apparent from the above description, according to the present invention, an electromagnetic cooker or a rice cooker that uniformly induction-heats an object to be heated having a curved outer shape of a heating target portion can be obtained at low cost. It is effective. Further, when the substantially disk-shaped conductive plate having the cutout portion is used, there is also an effect that the heating distribution of the object to be heated can be arbitrarily adjusted.

[Brief description of drawings]

FIG. 1A is a cross-sectional view of a main part of an induction heating mechanism when heating a wok according to the first embodiment of the present invention, and FIG. 1B is a measured value of a heating distribution in the wok in this case.

FIG. 2 (a) is a cross-sectional view of a main part of an induction heating mechanism in the case of heating a wok using only a heating coil formed in a curved shape, and FIG. 2 (b) is an actual measurement of heating distribution in the wok in this case. value.

FIG. 3A is a flat heating coil, a ferrite core,
And a cross-sectional view of the main part of the induction heating mechanism when the wok is heated using a flat conductive plate, (b) is the measured value of the heating temperature distribution in the wok in this case.

FIG. 4A is a sectional view of a main part of an induction heating mechanism when heating a rice cooker according to a second embodiment of the present invention, and FIG. 4B is a measured value of a heating distribution in the rice cooker in this case.

FIG. 5 (a) is a cross-sectional view of a main part of an induction heating mechanism in the case of heating a rice cooker using only a heating coil formed into a curved shape, and FIG. 5 (b) is an actual measurement of heating distribution in the rice cooker in this case. value.

FIG. 6 is a cross-sectional view of a main part of the induction heating mechanism in a state where a flat bottomed rice cooker is heated using a flat heating coil and a flat conductive plate.

FIG. 7A is a plan view showing a configuration example of an annular conductive plate.
(B) is the sectional view on the AA line.

FIG. 8 is a plan view showing another configuration example of the annular conductive plate.

9A is a plan view showing a configuration example of a plurality of annular conductive plates, and FIG. 9B is a sectional view taken along line BB thereof.

FIG. 10 is a plan view showing a configuration example of a spiral conductive plate.

FIG. 11 is a plan view showing another configuration example of the spiral conductive plate.

FIG. 12 is a plan view showing a configuration example of a substantially disc-shaped conductive plate.

FIG. 13 is a plan view showing a configuration example of a substantially disk-shaped conductive plate with a notch.

[Explanation of symbols]

1,1a, 11 Heating coil 2 Wok to be heated 3,13,13a to 13g Conductive plate 4 Insulating waterproof plate 5 Non-magnetic pot frame 6 Chinese range stand 7 Ferrite core 8 Other heated objects Rice cooker 9 Insulating waterproof container accommodating rice cooker 14, 14a to 14j Slit part 15 Notch part I ₁ High frequency current flowing in heating coil I _{2 to} I ₇ Induction current flowing in conductive plate

Claims (6)

[Claims] 1. An electromagnetic induction heating device for inductively heating an object to be heated, the heating target portion of which has a curved outer shape, comprising: a heating coil having a coil surface formed by spirally winding a conductive wire; and a surface portion thereof. Has a ring-shaped conductive plate whose rear surface faces the coil surface of the heating coil while directing to the heating target portion, and at least one slit connecting the outer peripheral edge and the inner peripheral edge is formed in the circular conductive plate. The electromagnetic induction heating device is characterized in that the shape of the surface portion of the annular conductive plate and the shape of the coil surface of the heating coil are curved shapes along the outer shape of the heating target portion. 2. A plurality of annular conductive plates having different diameters are concentrically arranged at predetermined intervals, and a slit portion connecting an outer peripheral edge and an inner peripheral edge of each annular conductive plate is provided adjacent to another annular shape. The electromagnetic induction heating device according to claim 1, wherein the electromagnetic induction heating device is formed at a portion relatively different from the slit portion of the conductive plate. 3. An electromagnetic induction heating apparatus for inductively heating an object to be heated, the heating target portion of which has a curved outer shape, comprising: a heating coil having a coil surface formed by spirally winding a conductive wire; and a surface portion thereof. Has a spiral conductive plate in which the back surface part is directed to the heating target site and the back surface part is directed to the coil surface of the heating coil, and the shape of the surface part of the spiral conductive plate and the coil surface of the heating coil is An electromagnetic induction heating device, each of which has a curved shape along the outer shape of the heating target portion. 4. An electromagnetic induction heating apparatus for inductively heating an object to be heated, the heating target portion having a curved outer shape, comprising: a heating coil having a coil surface formed by spirally winding a conductive wire; and a surface portion thereof. Has a conductive plate having a back surface portion directed to the heating target portion and a back surface portion directed to the coil surface of the heating coil, wherein the conductive plate has a central hole portion and extends from the central hole portion toward a peripheral portion. A plurality of slit portions and at least one connecting cutout portion connecting the central hole portion and the outer peripheral edge are formed, and the shapes of the surface portion of the conductive plate and the coil surface of the heating coil are respectively the above-mentioned. An electromagnetic induction heating device having a curved shape along the outer shape of a heating target portion. 5. The electromagnetic induction heating device according to claim 4, wherein the conductive plate has a slit-shaped notch formed in a direction from the predetermined portion of the outer peripheral edge toward the central hole. 6. The electromagnetic induction heating device according to claim 1, wherein a ferromagnetic material is arranged at a predetermined portion of the central portion of the coil surface of the heating coil.