JP2008218091A - Induction cooker - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an induction cooker for improving heating efficiency of an object to be heated with a simple structure. <P>SOLUTION: The induction cooker 20 is constituted of a top plate 22 on which the object 21 to be heated is loaded, a heating coil 11 provided at a lower side of the top plate 22 for heating the object 21 to be heated by induction and a high-frequency power source for driving the heating coil 11. By installing the heating coil 11, a coil axis becomes parallel with the top plate 22, magnetic flux in one direction is made to intersect the bottom surface of the object 21 to be heated. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an induction heating device, and more particularly to a technique for improving the heating efficiency of an object to be heated.

  The induction heating device places an object to be heated, such as a cooking pan, on a top plate formed of a non-magnetic material and insulator such as glass or resin, and generates eddy currents by interlinking magnetic flux with the object to be heated. Heating by Joule heat.

  As such an induction heating device, for example, it is conventionally known that a heating coil for generating magnetic flux is arranged on the lower side of the top plate so that the coil axis is orthogonal to the bottom surface of the object to be heated. In this case, when a high frequency current is supplied to the heating coil by a high frequency power source such as an inverter circuit to generate a magnetic flux, the magnetic flux is radially linked through the center of the bottom surface of the object to be heated. In this case, since the eddy current flows in a circular shape between the center part of the bottom surface of the heated object and the outer edge part with a large amount of magnetic flux linkage, a strong heat generation occurs in the doughnut-shaped intermediate part, resulting in uneven heating. There is a problem that occurs.

  On the other hand, Patent Document 1 describes that conductive materials are arranged in a straight line in parallel and in the same direction in order to generate an induction magnetic field. According to this, uniform heating can be performed in the width direction.

  Patent Document 2 describes that a heating coil for generating magnetic flux is formed by connecting a rectangular heating coil body and a reverse winding heating coil body. According to this, it is said that the electric current which flows into the heating coil of the range between the vertical center lines of each heating coil body becomes the same direction, and uniform heating is attained without canceling each magnetic flux.

JP 2002-289334 A JP 2006-120542 A

  However, in each said patent document, consideration is not made to the improvement of the heating efficiency of a to-be-heated material.

  That is, since the technique of Patent Document 1 has a configuration in which conductive materials are arranged in parallel, the inductance value is small. If the inductance value is small, the magnetomotive force is also small. Therefore, in order to obtain a large heating power, it is necessary to pass a large current. For this reason, the loss of the inverter which generates a high frequency current increases, and there exists a possibility that a high frequency power supply may enlarge. Moreover, in order to implement | achieve this structure, it is necessary to connect each electrically conductive material by an edge part, and it is also considered that manufacturability deteriorates.

  Moreover, since the coil described in Patent Document 2 has a smaller size than the object to be heated and the eddy current path is shortened, it is necessary to apply a large current to the coil in order to obtain a large heating force. There is. For this reason, the loss of the inverter which generates a high frequency current increases, and there exists a possibility that a high frequency power supply may enlarge.

  Then, this invention makes it a subject to implement | achieve the induction heating apparatus which improved the heating efficiency of the to-be-heated object with simple structure.

  In order to solve the above-described problems, an induction heating apparatus according to the present invention includes a top plate on which an object to be heated is placed, a heating coil that is disposed below the top plate and induction-heats the object to be heated, and the heating And a high frequency power source for driving the coil. And a heating coil is arrange | positioned so that the magnetic flux of one direction may be linked to the bottom face of to-be-heated material, It is characterized by the above-mentioned.

  According to this, since the magnetic flux is generated using the coil, the inductance value is increased and the magnetomotive force is increased as compared with the configuration in which the conductive materials are arranged in parallel. Further, since the magnetomotive force is increased, the heating amount of the object to be heated can be improved.

  Furthermore, since the generated magnetic flux is linked to the bottom surface of the object to be heated in one direction, the eddy current generated thereby flows perpendicularly to the direction of the magnetic flux and flows through the entire object to be heated in a large loop. It will be. That is, the path through which the eddy current flows becomes longer, the resistance increases, and the inner and outer surfaces of the object to be heated are simultaneously heated, so that it is possible to obtain a large amount of heat with a small current. Therefore, the energy lost by the heating coil and the loss in the inverter circuit can be significantly reduced with a simple structure, and the heating efficiency of the object to be heated can be improved.

  Specifically, the heating coil may be arranged so that the coil axis is parallel to the top plate. In this case, the heating coil may be formed in a flat shape so that the flat surface faces the top plate. With this configuration, the magnetic flux generated by the heating coil can be linked in one direction to the bottom surface of the object to be heated.

  Moreover, you may insert a magnetic body member in the air core part of a heating coil. According to this, the magnetic flux generated from the heating coil is induced to the object to be heated, and the object to be heated can be efficiently heated. Therefore, the current flowing through the heating coil can be further reduced, and the loss of the heating coil and the inverter circuit can be reduced.

  In this case, you may comprise a magnetic body member by the at least 2 or more magnetic body member inserted side by side at intervals. In this way, by forming an air layer that is not magnetically saturated between the magnetic members, saturation of the magnetic member caused by flowing a large current through the heating coil can be suppressed.

  Further, the heating coil may be constituted by one coil, and this coil may be arranged over the entire lower surface of the top plate. This makes it possible to heat the object to be heated anywhere on the top plate, and to heat a plurality of objects to be heated at the same time.

  On the other hand, the heating coil may be composed of a plurality of coils, each of the plurality of coils may be disposed below the portion of the top plate where the object to be heated is placed, and the directions of the coil axes may be different from each other. In this case, it is desirable to arrange the plurality of coils so that the relative angle between the coil axes is 60 ° to 120 °, or 240 ° to 300 °.

  With such an arrangement, the direction of the magnetic flux generated in each heating coil is different, so that there is no interference between the magnetic fluxes, and it is possible to suppress interference noise and panning noise.

  ADVANTAGE OF THE INVENTION According to this invention, the induction heating apparatus which improved the heating efficiency of the to-be-heated material with a simple structure is realizable.

  Hereinafter, an embodiment to which the present invention is applied will be described with reference to FIGS. In the following description, the same functional parts are denoted by the same reference numerals, and redundant description is omitted.

(First embodiment)
A first embodiment of the present invention will be described with reference to FIGS. FIG. 1 is a configuration diagram of a heating coil for generating magnetic flux used in the induction heating apparatus according to the first embodiment of the present invention. As shown in FIG. 1, the heating coil 11 is formed by winding a conductive material in a spiral shape. As the heating coil, an electric wire in which a large number of enamel wires called litz wires are brought close to each other and other known conductive members can be used.

  FIG. 2 is a longitudinal sectional view showing the configuration of the induction heating apparatus of the first embodiment. The induction heating device 20 includes, for example, a top plate 22 formed of glass or the like on which an object to be heated 21 such as a cooking pot is placed, and a cross section AA in FIG. 1 arranged below the top plate 22. And an inverter circuit as a high-frequency power source (not shown) that generates an induction magnetic field by flowing an alternating current through the heating coil 11. The top plate 22 is not limited to glass, and other materials such as non-magnetic materials and insulators such as resin can be used.

  The heating coil 11, which is a characteristic part of the present embodiment, is formed in a flat shape in which the coil shape viewed from the coil axial direction crushes a circle, and the flat surface faces the top plate 22. . Further, the coil shaft centers are arranged in parallel along the top plate 22. However, the shape of the heating coil is not limited to such a shape, and can be appropriately modified as long as the coil axis is arranged in parallel with the top plate 22.

  FIG. 3 is a diagram showing a general inverter circuit used in the present embodiment. The inverter circuit has a power supply 31 and an upper and lower arm composed of IGBTs 32 and 33, and is configured to connect the heating coil 11 via a resonance capacitor 36 between the middle point of the upper and lower arms and the negative electrode of the power supply 31. ing.

  In the inverter circuit, when the IGBT 32 is turned on, a current flows from the positive electrode of the power supply 31 to the IGBT 32, the heating coil 11, the resonance capacitor 36, and the negative electrode of the power supply 31. Next, when the IGBT 32 is turned off at a desired time, a current flows through the path of the heating coil 11, the resonance capacitor 36, and the diode 35 by the energy stored in the heating coil 11. The IGBT 33 is kept on during the period when the diode 35 is on.

  Next, when the energy stored in the heating coil 11 is exhausted, a current flows through the resonant capacitor 36, the heating coil 11, and the IGBT 33 using the resonant capacitor 36 as a power source. Next, when the IGBT 33 is turned off at a desired time, a current flows through the path of the heating coil 11, the diode 34, the power supply 31, and the resonance capacitor 36. The IGBT 32 is kept in an on state while the diode 34 is on. By repeating the above operation, a sinusoidal alternating current flows through the heating coil 11.

  Next, the heating principle of the pan that is the object to be heated will be described. When a high frequency current flows through the heating coil 11, a magnetic flux 23 is generated from the heating coil 11. Here, since the heating coil 11 is disposed so that the coil axis is parallel to the top plate 22, the magnetic flux 23 passes through the entire bottom surface of the pan in one direction. When the magnetic flux is linked to the pan, an eddy current 41 is generated in the pan. This eddy current 41 flows perpendicular to the direction of magnetic flux as shown in FIG.

  And as shown by the arrow of FIG. 5, the eddy current 41 flows through the pan bottom outer surface to the pan bottom outer end (outer edge portion of the pan bottom), and passes the pan bottom inner surface through the side plate portion of the pan to the outer side opposite to the pan bottom. It flows toward the end. That is, since the eddy current 41 flows in a large loop of the entire pan, the current path becomes long, the resistance increases, and the inner and outer surfaces of the pan are simultaneously heated, so that it is possible to obtain a large amount of heat with a small current. Therefore, the energy lost in the heating coil 11 and the loss in the inverter circuit can be greatly reduced.

  Moreover, in the conventional induction heating apparatus, the problem of the pot floating due to the electromagnetic repulsive force has occurred. However, in this embodiment, the eddy current 41 flows on the inner and outer surfaces of the pot, thereby canceling the electromagnetic repulsive force and causing the pot to float. Suppression becomes possible.

  That is, as shown in the principle diagram of the pot floating suppression in FIG. 6, since the eddy current flows to the outer and inner surfaces of the pot bottom, a downward force 61 is generated on the outer surface of the pot bottom according to Fleming's left hand rule. An upward force 62 is generated on the inner surface. As a result, the force applied to the pan is offset, and the pan floating can be suppressed.

(Second Embodiment)
A second embodiment of the present invention will be described with reference to FIGS. FIG. 7 is a configuration diagram of a heating coil unit for generating magnetic flux used in the induction heating apparatus according to the second embodiment of the present invention.

  As shown in FIG. 7, the heating coil unit 72 includes a heating coil 11 formed by winding a conductive material in a spiral shape, and a ferrite core 71 that is a magnetic member inserted in the air core of the heating coil 11. Is composed.

  FIG. 8 is a longitudinal sectional view showing the configuration of the induction heating device of the second embodiment. The induction heating device shows a top plate 22 formed of glass or the like on which a heated object 21 such as a cooking pot is placed, and a cross section AA of FIG. 7 arranged below the top plate 22. The heating coil unit 72 includes the above-described inverter circuit that generates an induction magnetic field by flowing an alternating current through the heating coil 11.

  The heating principle is the same as in the first embodiment. The feature of this embodiment is a configuration in which the heating coil 11 is wound around a U-shaped ferrite core 71 whose both ends are bent toward the top plate as shown in FIG. By setting it as such a structure, the magnetic flux 73 generated from the heating coil 11 will be induced | guided | derived to the pan side, and it will become possible to heat a pan efficiently. Therefore, since the current flowing through the heating coil 11 can be further reduced, the loss of the heating coil 11 and the inverter circuit can be reduced.

(Third embodiment)
A third embodiment of the present invention will be described with reference to FIG. FIG. 9 is a configuration diagram of a heating coil unit for generating magnetic flux used in the induction heating apparatus according to the third embodiment of the present invention.

  As shown in FIG. 9, in the present embodiment, a plurality of ferrite cores 91 are inserted in the air core of the heating coil 11 so as to be spaced apart from each other. In other words, the heating coil unit 92 is configured by winding a conductive material in a spiral shape around ferrite cores divided in parallel.

  The heating principle of this embodiment is the same as that of the first embodiment. When heating a non-magnetic and low-resistance material such as an aluminum pan, as shown in the relationship diagram between the current flowing through the heating coil and the electric power generated in the object to be heated shown in FIG. Need to flow. At this time, if a large current is passed, the magnetomotive force determined by the product of the number of turns of the heating coil and the current increases, and the ferrite core may be saturated.

  In this respect, the feature of this embodiment is that the U-shaped ferrite 91 is divided and an air layer that is not magnetically saturated is interposed between the ferrite cores, thereby preventing magnetic saturation as a whole of the heating coil unit. In addition, it is possible to link a unidirectional alternating magnetic field to the pan, thereby preventing the pan from being lifted and improving the heating efficiency.

(Fourth embodiment)
The fourth embodiment will be described with reference to FIGS. FIG. 11 is a plan view of an induction heating apparatus according to the fourth embodiment of the present invention. In the present embodiment, as shown in FIG. 11, an object to be heated 21 is placed on the top plate 22, and one heating coil 111 is disposed on the entire lower portion of the top plate 22.

  FIG. 12 is a view showing a longitudinal section of the induction heating apparatus of the present embodiment, and shows an AA section of FIG. 11. The same components as those in FIG. 11 are denoted by the same reference numerals. As shown in FIG. 12, the upper surface of the casing 121 of the induction heating device is configured by the top plate 22, and the heating coil 111 extends over the entire lower surface of the top plate 22 and the coil axis is parallel to the top plate 22. Are arranged as follows. When an alternating current is passed through the heating coil 111, a magnetic flux 122 that links the object to be heated 21 in one direction is generated as in the above-described embodiment.

  The present embodiment is characterized in that the heating coil 111 is disposed on the entire lower portion of the top plate 22. This makes it possible to heat the object to be heated anywhere on the top plate 22. In addition, a plurality of objects to be heated can be heated at the same time.

(Fifth embodiment)
A fifth embodiment will be described with reference to FIGS. FIG. 13 is a plan view of the induction heating apparatus of the fifth embodiment. As shown in FIG. 13, the present embodiment has a configuration in which two heating coils 131 and 132 are arranged corresponding to the place on the top plate 22 where the object 21 to be heated is placed.

  FIG. 14 is a view showing a longitudinal section of the induction heating apparatus of the present embodiment, and shows an AA section of FIG. The same components as those in FIG. 13 are denoted by the same reference numerals. As shown in the drawing, the upper surface of the casing 141 of the induction heating apparatus is configured by the top plate 22, and the two heating coils 131 and 132 are provided on the lower side of the top plate 22 corresponding to the placement positions of the heated objects 21. The coil axis is arranged so as to be parallel to the top plate. Furthermore, the feature of this embodiment is that the winding directions of the heating coils 131 and 132 are different on the left and right. With respect to the heating coil 131, the heating coil 132 is disposed with its coil axis rotated 90 degrees. With this arrangement, as shown in FIG. 14, the magnetic fluxes 142 and 143 generated by the left and right heating coils 131 and 132 are different in direction, so that there is no interference between the magnetic fluxes. Can be suppressed.

  FIG. 15 shows the relationship between the angle θ created by the magnetic flux generated from the left and right heating coils 131 and 132, the degree of coupling of the left and right heating coils, and the amount of noise. The degree of interference shown in FIG. 15 is determined by COSθ. It can be seen that when the angle θ of the magnetic flux generated from the heating coil is 60 ° to 120 ° or 240 ° to 300 °, the noise amount is 0 dB or less, and interference noise can be efficiently suppressed. Therefore, it is desirable to arrange the heating coils 131 and 132 so that the relative angle between the coil axes is 60 ° to 120 °, or 240 ° to 300 °.

It is a block diagram of the heating coil for magnetic flux generation used for the induction heating apparatus of 1st Embodiment. It is a longitudinal cross-sectional view which shows the structure of the induction heating apparatus of 1st Embodiment. It is a figure which shows an inverter circuit structure. It is a figure which shows the relationship between the magnetic flux linked to a to-be-heated material, and the eddy current which generate | occur | produces in a to-be-heated material. It is a figure which shows the path | route of the eddy current which flows through a to-be-heated material. It is a figure which shows the principle of the float suppression of a to-be-heated material. It is a block diagram of the heating coil unit for magnetic flux generation used for the induction heating apparatus of 2nd Embodiment. It is a longitudinal cross-sectional view which shows the structure of the induction heating apparatus of 2nd Embodiment. It is a block diagram of the heating coil unit for magnetic flux generation used for the induction heating apparatus of 3rd Embodiment. It is a figure which shows the relationship between the electric power which generate | occur | produces in a to-be-heated material, and the electric current sent through a heating coil. It is a top view of the induction heating apparatus of 4th Embodiment. It is a figure which shows the longitudinal cross-section of the induction heating apparatus of 4th Embodiment, and has shown the AA cross section of FIG. It is a block diagram of the heating coil unit for magnetic flux generation used for the induction heating apparatus of 5th Embodiment. It is a figure which shows the longitudinal cross-section of the induction heating apparatus of 5th Embodiment, and has shown the AA cross section of FIG. The relationship between the angle θ created by the magnetic flux generated from the left and right heating coils, the degree of coupling of the left and right heating coils, and the amount of noise is shown.

Explanation of symbols

11, 111, 131, 132 Heating coil 20 Induction heating device 21 Object to be heated 22 Top plate 23, 73, 122, 142, 143 Magnetic flux 31 Power supply 32, 33 IGBT
34, 35 Diode 36 Resonant capacitor 41 Eddy current 71, 91 Ferrite core

Claims (8)

An induction heating apparatus comprising: a top plate on which an object to be heated is placed; a heating coil that is disposed under the top plate and that induction-heats the object to be heated; and a high-frequency power source that drives the heating coil. There,
The induction heating apparatus, wherein the heating coil is arranged so as to link a magnetic flux in one direction to a bottom surface of the object to be heated. An induction heating apparatus comprising: a top plate on which an object to be heated is placed; a heating coil that is disposed under the top plate and that induction-heats the object to be heated; and a high-frequency power source that drives the heating coil. There,
The induction heating apparatus, wherein the heating coil has a coil axis arranged in parallel with the top plate.   The induction heating apparatus according to claim 2, wherein the heating coil is formed in a flat shape, and is arranged with a flat surface facing the top plate.   The induction heating apparatus according to any one of claims 1 to 3, wherein a magnetic member is inserted into an air core portion of the heating coil.   The induction heating apparatus according to claim 4, wherein the magnetic member is composed of at least two or more magnetic members inserted side by side with a space therebetween.   The induction heating apparatus according to claim 4, wherein the heating coil is composed of one coil, and the coil is disposed over the entire lower surface of the top plate.   The heating coil is composed of a plurality of coils, and the plurality of coils are respectively disposed below the top plate where the object to be heated is placed, and the directions of the coil axes are different from each other. The induction heating apparatus according to claim 4, wherein the induction heating apparatus is arranged.   The induction heating apparatus according to claim 7, wherein the plurality of coils are arranged such that a relative angle between the coil axes is 60 ° to 120 °, or 240 ° to 300 °. .

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