JP2005235594A - Induction heating cooker - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an induction heating cooker for fully reducing leakage magnetic flux. <P>SOLUTION: In the induction heating cooker for performing the electromagnetic induction heating of an object 3 to be heated by a heating coil 2, at least one set of nearly loop-shaped conductors 4 in which a loop surface is composed nearly in a vertical direction to a half circle on the surface of the heating coil are arranged, thus reducing the horizontal component of the leakage magnetic flux. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a technique for reducing leakage magnetic flux of an induction heating cooker, particularly a horizontal component.

  FIG. 5 shows a configuration of a general leakage magnetic flux reduction method for an induction heating cooker. The principle of the induction heating cooker is to supply a high-frequency current to the heating coil 2 disposed on the lower side of the top plate 1 to generate a high-frequency magnetic flux, and by this magnetic flux, a metal pan or the like disposed on the upper side of the top plate 1 An eddy current is generated in the object to be heated 3 and cooking is performed by Joule heat generated by the eddy current and the resistance of the object to be heated.

  Here, a conductive ring 4 is disposed on the outer periphery of the heating coil 2. An induced current flows through the conductive ring 4 by the high-frequency magnetic flux generated from the heating coil 2 or the object to be heated 3. Since the cancellation magnetic flux (high-frequency magnetic flux) due to the induced current is generated in a direction that cancels the high-frequency magnetic flux generated from the heating coil 2 or the object to be heated 3, the leakage magnetic flux to the outside can be reduced.

Therefore, as one method for reducing the leakage magnetic flux, Patent Document 1 or Patent Document 2 discloses providing a conductive ring configured in a donut shape with a conductive material such as aluminum.
Japanese Patent Publication No. 58-37676 Japanese Patent Laid-Open No. 10-302953

  However, in general, the conductive ring 4 is generally disposed on the same plane as the heating coil 2. This is because the high frequency magnetic flux on the substantially same plane as the heating coil 2 is large, so that the canceling magnetic flux on the substantially same plane is maximized, and the induced current is improved by improving the magnetic coupling with the heating coil 2. This is because the flow is easy and a canceling magnetic flux is easily generated.

  Such a positional relationship is shown in FIG. In FIG. 6, at the tip of the vector representing the magnetic flux, the shaded triangle is the magnetic flux due to the heating coil, the black triangle is the magnetic flux due to the object to be heated, the square is the magnetic flux due to the conductive ring, and the triangle is the combined magnetic flux (reduced leakage magnetic flux) Respectively.

  As shown in FIG. 6, on the substantially same plane as the heating coil 2, the high-frequency magnetic flux by the heating coil 2 is only in the vertical direction, but the object to be heated 3 is disposed above the heating coil 2, so The high-frequency magnetic flux generated by the heated object 3 generates both horizontal and vertical components.

  On the other hand, since the conductive ring 4 is disposed on substantially the same plane as the heating coil 2, only a vertical component is generated as a canceling magnetic flux. Therefore, even if the vertical component of the leakage flux can be canceled in a well-balanced manner, the horizontal component remains, resulting in hindering leakage flux reduction.

  Moreover, although copper and aluminum which are low resistance materials are used for the material of the conductive ring 4, there is a slight resistance component even with these materials, so that leakage from the heating coil 2 and the object to be heated 3 occurs. There is a phase difference between the magnetic flux and the canceling magnetic flux from the conductive ring 4.

  FIG. 7 shows the relationship between the amplitude / phase difference between the leakage magnetic flux A and the cancellation magnetic flux B before reduction and the amplitude of the leakage magnetic flux C after reduction. As an example, the phase difference is 5 [deg.] (FIG. 7A). ) And 20 [deg.] ((B) in the figure). Even if the leakage magnetic flux A before and after reduction has the same amplitude as the cancellation magnetic flux B, it can be seen that if the phase difference between the two is large, the effect of reducing the leakage magnetic flux C is limited.

  This invention solves said subject and aims at provision of the induction heating cooking appliance which can fully reduce a leakage magnetic flux.

  In order to solve the above-described problems, the present invention provides a substantially loop-like conductive structure in which a loop surface is configured in a direction substantially perpendicular to a heating coil surface in an induction heating cooker in which an object to be heated is electromagnetically heated by a heating coil. One or more bodies are arranged. According to this configuration, the horizontal component of the leakage magnetic flux can be reduced.

  In this case, the substantially loop-shaped conductor disposed in a direction substantially perpendicular to the heating coil surface can be constituted by two or more turns including the loop center therein. According to this configuration, the phase difference between the high-frequency magnetic flux and the canceling magnetic flux from the heating coil or the object to be heated can be reduced, and the leakage magnetic flux can be effectively reduced.

  Furthermore, a substantially loop-shaped conductor in which a loop surface is configured and arranged in a direction substantially perpendicular to the heating coil surface and another substantially loop-shaped conductor arranged in parallel with the heating coil surface can be connected in series. it can.

  According to this configuration, it is possible to generate a sufficient canceling magnetic flux by increasing the induced current of the conductor and to reduce the leakage magnetic flux, and to change the horizontal / vertical component ratio of the canceling magnetic flux to Magnetic flux can be effectively reduced.

  Moreover, you may arrange | position the substantially loop-shaped conductor in which the loop surface of a substantially perpendicular | vertical direction with respect to a heating coil surface is arrange | positioned in an outer half periphery part other than the structure arrange | positioned in the perimeter of a heating coil. According to the above configuration, it is possible to arrange a substantially loop-shaped conductor having a loop surface in a substantially vertical direction in the front region of the cooker body, for example, which requires countermeasures against magnetic flux leakage. Magnetic flux can be reduced.

  Moreover, the substantially loop-shaped conductor arrange | positioned in parallel with a heating coil surface can be set as the structure which surrounds the center of a heating coil 2 times or more. According to this configuration, the phase difference between the high-frequency magnetic flux and the canceling magnetic flux from the heating coil or the object to be heated can be reduced, and the leakage magnetic flux can be effectively reduced.

  In addition, a litz wire can be used as a component that forms a substantially loop-shaped conductor. According to this configuration, the loop shape of the conductor can be flexibly formed in an effective arrangement, and the leakage magnetic flux can be reduced.

  Moreover, a metal plate can also be used as a structure which forms a substantially loop-shaped conductor. According to this configuration, it is possible to widen a region where the induced current of the conductor flows, and to effectively reduce the leakage magnetic flux.

  Furthermore, a non-magnetic low-resistance metal can be used as the material of the component that forms the substantially loop-shaped conductor. Nonmagnetic low resistance metals include copper and aluminum. According to this configuration, the phase difference between the high-frequency magnetic flux and the canceling magnetic flux due to the heating coil or the object to be heated can be reduced, and the leakage magnetic flux can be effectively reduced.

  As described above, according to the present invention, the induction in which the horizontal component of the leakage magnetic flux is sufficiently reduced by arranging the substantially loop-shaped conductor having the loop surface substantially perpendicular to the semicircle of the heating coil surface. A cooker can be provided.

EMBODIMENT OF THE INVENTION Embodiment of the induction heating cooking appliance which concerns on this invention below is described based on drawing.
<First Embodiment>
Drawing 1 is a figure showing the composition of the induction heating cooking appliance which is a 1st embodiment, (a) is the top view, and (b) is the front view. FIG. 2 is a partial cross-sectional view of the induction heating cooker and a diagram showing the leakage magnetic flux vector. In FIG. 2, at the tip of the vector representing the magnetic flux, the shaded triangle is the magnetic flux due to the heating coil, the black triangle is the magnetic flux due to the object to be heated, the square is the magnetic flux due to the substantially loop conductor, and the triangle is the combined magnetic flux (leakage after reduction) (Magnetic flux) is shown respectively (the same applies to FIGS. 4 and 5).

  As shown in FIGS. 1 and 2, the induction heating cooker according to the present embodiment is provided with a top plate 1 made of a non-magnetic material attached to the upper surface of a cooker body (not shown), and below the top plate 1. One or more sets of the heating coil 2 provided and a substantially loop-shaped conductor 4 for canceling an unnecessary magnetic field radiated from the heating coil 2 to the outside are arranged. The heating coil 2 is placed on an internal support base (not shown) of the cooker body.

  The substantially loop-shaped conductor 4 is arranged in a semicircular shape on the outer side of the heating coil 2 with respect to the semicircle of the heating coil surface and spaced from the outer periphery of the heating coil, and the loop surface is perpendicular to the heating coil 2. Arranged to be configured.

  That is, the substantially loop-shaped conductor 4 forms a substantially rectangular closed loop from the upper side 4a, the lower side 4b, and the left and right side pieces 4c. The substantially loop-shaped conductor 4 has a lower side 4b disposed slightly below the surface of the heating coil 2 and an upper side 4a disposed above the surface of the heating coil.

  Here, the reason why the substantially loop-shaped conductor 4 is arranged in a semicircular shape at the front side position of the heating coil 2 is as follows. When installed on the induction heating cooker body, the user approaches the cooker body on the front side or the rear side, but on the rear side of the cooker body, the distance from the heating coil is relatively far away, and cooking The leakage magnetic flux value on the outer periphery of the main body is smaller than the front side. Therefore, since it is the front part that needs to take countermeasures against leakage magnetic flux, the substantially loop-shaped conductor is preferentially arranged on the front part, thereby reducing the component (substantially loop-shaped conductor). I am doing so. Of course, the substantially loop-shaped conductor may be disposed on the entire circumference of the heating coil.

  The substantially loop-shaped conductor 4 is made of a nonmagnetic low resistance metal such as copper or aluminum. The substantially loop-shaped conductor 4 may be a litz wire or a metal plate as long as it is a low resistance metal.

  In the above-described configuration, the induced current of the substantially loop-shaped conductor 4 is generated in a direction that prevents the magnetic flux interlinking with the substantially loop-shaped conductor 4. At this time, the direction of current and the direction of magnetic flux of the heating coil 2, the object to be heated 3, and the loop-shaped conductor 4 are the directions shown in FIG.

  Here, induced currents having the same size and different directions flow through the upper side 4 a and the lower side 4 b of the loop-shaped conductor 4 arranged perpendicular to the heating coil 2. Accordingly, in the vicinity of the horizontal plane of the heating coil 2, the vertical components of the magnetic flux generated by the upper side 4a / lower side 4b of the substantially loop-shaped conductor 4 cancel each other, the horizontal components have a size obtained by adding each other, and the heating coil 2 and the horizontal component of the magnetic flux due to the object 3 to be heated.

  Thus, in the present embodiment, only the horizontal component can be generated as the canceling magnetic flux, and only the horizontal component can be reduced.

  In addition, although the substantially loop-shaped conductor 4 in the said embodiment has been arrange | positioned so that a loop surface may be comprised in the orthogonal | vertical direction with respect to the semicircle of a heating coil surface, not only this but in the outer periphery of a perimeter of a heating coil The loop surface may be arranged in a direction perpendicular to the heating coil surface.

<Second Embodiment>
FIG. 3 shows the configuration of an induction heating cooker showing a second embodiment of the present invention, in which (a) is a plan view, (b) is a front view, (c) is a side view, and (d). ) Is a perspective view showing the arrangement of conductors in a diagram.

  In FIG. 3, in the induction heating cooker, the first substantially loop-shaped conductor 4 is arranged in two turns so that the loop surface is formed outside the heating coil 2 in a direction perpendicular to the semicircle of the heating coil 2. Has been. The first substantially loop-shaped conductor 4 constitutes a substantially rectangular loop from the upper side 4a, the lower side 4b and the left and right side pieces 4c, and is arranged so that the heating coil 2 is positioned between the upper and lower sides 4a, 4b.

  In addition, a second substantially loop-shaped conductor 5 is disposed on the outside of the heating coil 2 and below the heating coil plane so as to surround the center of the heating coil and to be substantially parallel to the heating coil surface.

  In addition, a third loop conductor 6 is arranged on the upper side of the heating coil 2 with a size smaller than the outer shape of the heating coil 2 around the center of the heating coil and substantially parallel to the heating coil 2.

  These first to third substantially loop-shaped conductors 4, 5, and 6 are connected in series. Moreover, in this embodiment, these conductors 4-6 are comprised with the litz wire which twisted the fine wire.

  Here, when assuming the litz wire of the same specification, when the substantially loop-shaped conductor 4 has only one turn and when it makes two turns, the case of making two turns as shown in the following formula is heating. The phase difference between the high-frequency magnetic flux and the canceling magnetic flux caused by the coil 2 or the object to be heated 3 can be reduced, and it can be expected that the leakage magnetic flux is effectively reduced.

When the phase difference in the case of only one round is θ1, the phase difference in the case of one round is θ2,
θ1 = 90−tan ⁻¹ (ωL / R)
θ2 = 90−tan ⁻¹ (ω4L / 2R) = 90−tan ⁻¹ (ω2L / R)
Here, the angular frequency of the high-frequency magnetic flux is ω, the resistance per loop of the loop-shaped conductor is R, and the self-inductance per loop of the substantially loop-shaped conductor is L.

  In this embodiment, since the substantially loop-shaped conductors of two rounds are arranged in close contact with each other, the shape and arrangement position thereof can be regarded as the same, and the mutual inductance between the loops can be L.

Here, if actual values are introduced into ω, L, and R,
Since ω = 2π · 25000≈157000, L = 0.00000008, and R = 0.02,
θ1≈90−81 = 9 [deg.]
θ2≈90−85 = 5 [deg.]
In the above configuration, the magnetic flux from the heating coil 2 or the object to be heated 3 is larger in the substantially loop-shaped conductors 5 and 6 that are parallel than the substantially loop-shaped conductor 4 that is perpendicular to the heating coil surface. Interlink. In particular, compared with the first embodiment in which the number of magnetic flux linkages of the loop-shaped conductor 6 disposed on the upper side of the heating coil 2 is large and the substantially loop-shaped conductor parallel to the heating coil 2 is not disposed, the substantially loop-shaped conductor. Since the induced currents 5 and 6 can be increased, the canceling magnetic flux can also be increased.

  At this time, the current direction and the magnetic flux direction of the heating coil 2, the object to be heated 3, and the substantially loop-shaped conductors 4 to 6 are the directions shown in FIG. In this embodiment, a canceling magnetic flux is generated by both the substantially loop-shaped conductor 4 perpendicular to the heating coil 2 and the substantially loop-shaped conductors 5 and 6 parallel to the heating coil 2. Therefore, as in the first embodiment, not only a horizontal component but also a cancel flux of a vertical component is generated.

  In the present embodiment, the number of turns of the substantially loop-shaped conductor in the horizontal direction and the substantially loop-shaped conductor in the vertical direction is set to 2 turns on the heating coil 2, but the present invention is not limited to this. Thus, the ratio of the horizontal / vertical component of the canceling magnetic flux can be changed. Therefore, the turn ratio may be set so that a canceling magnetic flux that can effectively cancel the horizontal / vertical components of the magnetic flux from the heating coil and the object to be heated is generated. The shape of the substantially loop-shaped conductor is not limited to a circle, but may be an ellipse, a rectangle, or a polygon.

(A) is a top view which shows the structure of the induction heating cooking appliance which is the 1st Embodiment of this invention, (b) is the front view similarly. The figure which shows the leakage flux vector in 1st Embodiment (A) is a top view which shows the structure of the induction heating cooking appliance which is the 2nd Embodiment of this invention, (b) is a front view similarly, (c) is a side view, (d) is a conductor arrangement line, Perspective view The figure which shows the leakage flux vector in 2nd Embodiment The figure which shows the structure of the conventional induction heating cooking appliance The figure which shows the leakage magnetic flux vector of the conventional induction heating cooking appliance (A) (b) is a figure which shows the phase difference of a cancellation magnetic flux, and a leakage magnetic flux reduction effect.

Explanation of symbols

1 Top plate 2 Heating coil 3 Object to be heated (cooking pan)
4, 5, 6 Substantially loop conductor

Claims (7)

  In an induction heating cooker that electromagnetically heats an object to be heated with a heating coil, one or more sets of substantially loop-shaped conductors having a loop surface substantially perpendicular to the heating coil surface are arranged. Induction heating cooker.   The induction heating cooker according to claim 1, wherein the substantially loop-shaped conductor disposed in a direction substantially perpendicular to the heating coil surface is constituted by two or more turns.   A substantially loop-shaped conductor in which a loop surface is configured and arranged in a direction substantially perpendicular to the heating coil surface and another substantially loop-shaped conductor arranged in parallel to the heating coil surface are connected in series. The induction heating cooker according to claim 1 or 2.   The induction according to any one of claims 1 to 3, wherein a substantially loop-shaped conductor having a loop surface in a direction substantially perpendicular to the heating coil surface is disposed on an outer half circumference of the heating coil. Cooking cooker.   The induction heating cooker according to claim 3 or 4, wherein the substantially loop-shaped conductor arranged in parallel with the heating coil surface surrounds the center of the heating coil two or more times.   The induction heating cooker according to any one of claims 1 to 5, wherein a litz wire or a metal plate is used as a component that forms a substantially loop-shaped conductor.   The induction heating cooker according to any one of claims 1 to 6, wherein a non-magnetic low-resistance metal is used as a component that forms a substantially loop-shaped conductor.

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