JP2018206723A - Electromagnetic induction heating device - Google Patents

Abstract

To provide an electromagnetic induction heating device with less magnetic field leaking to the outside of a heating coil.SOLUTION: In order to solve the above-described problem, an electromagnetic induction heating device according to the present invention includes a heating coil for heating an object to be heated, a magnetic body arranged opposite to an outer peripheral side surface of the heating coil and guiding a magnetic flux generated from the heating coil to the object to be heated, and a plurality of annular conductors surrounding the outer circumferential side face of the heating coil outside the magnetic body, and the plurality of annular conductors are stacked and arranged with a space therebetween.SELECTED DRAWING: Figure 1

Description

  The present invention relates to an electromagnetic induction heating apparatus for induction heating a metal pan.

  When a load such as a metal pan is placed on the top plate, the electromagnetic induction heating cooker generates high-frequency current from the high-frequency inverter to the heating coil and generates eddy current in the metal pan placed close to the coil. Heat is generated by the electrical resistance of the metal pan itself.

  In this electromagnetic induction heating cooker, if the magnetic flux generated from the heating coil leaks to the outside, it may cause an increase in the magnetic field strength of the radiated noise and malfunction of the control circuit. An annular conductor is provided as a conductive member.

  For example, in the abstract of Patent Document 1, when arranging a plurality of shielded wires (electromagnetic shield conductive members) side by side, the outer shielded wire has a smaller conductor cross-sectional area than the inner shielded wire, In addition, an induction heating device is disclosed that improves airflow to the upper surface of the heating coil by disposing the upper surface of the outer shield wire lower than the inner shield wire.

JP 2002-93561 A

  Even in Patent Document 1 described above, the leakage magnetic field to the outside can be reduced, but there are the following problems.

  In Patent Document 1, a plurality of electromagnetic shielding conductive members (shielded wires) are arranged side by side with respect to the heating coil. In this case, since the magnetic flux generated from the heating coil attenuates as the distance from the heating coil increases, the shielding effect decreases as the distance between the heating coil and the conductive member increases. Therefore, in the configuration in which a plurality of electromagnetic shielding conductive members are arranged concentrically, there is a problem that a sufficient shielding effect cannot be obtained with the electromagnetic shielding conductive member on the outer peripheral side.

  Therefore, in the present invention, an electromagnetic induction heating device that can achieve sufficient cooling of the heating coil as well as Patent Document 1 while obtaining a sufficient shielding effect by effectively arranging a plurality of conductive members for electromagnetic shielding. The purpose is to provide.

  In order to solve the above problems, an electromagnetic induction heating device according to the present invention is arranged to face a heating coil for heating an object to be heated and an outer peripheral side surface of the heating coil, and to generate magnetic flux generated from the heating coil to the object to be heated. A magnetic body to be guided and a plurality of annular conductors surrounding the outer peripheral side surface of the heating coil outside the magnetic body are provided, and the plurality of annular conductors are stacked and arranged with a gap therebetween.

  A heating coil that heats the object to be heated; a magnetic body that is disposed opposite to an outer peripheral side surface of the heating coil; and that guides the magnetic flux generated from the heating coil to the object to be heated; and An annular conductor surrounding an outer peripheral side surface is provided, and the annular conductor is divided into a plurality of conductive portions by a slit extending in the circumferential direction at a portion facing the magnetic body.

  ADVANTAGE OF THE INVENTION According to this invention, the shielding effect by the electroconductive member for electromagnetic shielding can be improved, and the electromagnetic induction heating apparatus with few leakage magnetic fields can be provided.

Basic configuration of electromagnetic induction heating device Schematic diagram of the current flowing through the conductive member for electromagnetic shielding of the comparative example Vector diagram of current flowing in conductive member for electromagnetic shield of comparative example The schematic diagram of the electric current which flows into the electrically-conductive member for electromagnetic shields of Example 1 Current vector diagram flowing through the electromagnetic shielding conductive member of Example 1 Modification Example of Heating Coil of Electromagnetic Induction Heating Device of Example 1 The perspective view of the heating coil of the electromagnetic induction heating apparatus of Example 2. The perspective view of the heating coil of the electromagnetic induction heating apparatus of Example 3

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

  FIG. 1 is a basic configuration diagram of an electromagnetic induction heating apparatus according to Embodiment 1 of the present invention. This electromagnetic induction heating device is for inductively heating an object to be heated 5 (a metal pan or the like) placed on the top plate 6, and the heating coil 1 and the magnetic flux generated from the heating coil 1 are contained therein. A magnetic body 2 that leads to an object to be heated 5 and an annular conductor 3 that is a conductive member for electromagnetic shielding that surrounds the outer peripheral side surface of the heating coil 1 are provided. A high frequency alternating current is supplied to the heating coil 1 from the inverter 4, a magnetic field is generated from the heating coil 1 by the alternating current, and the object to be heated 5 is induction-heated.

  First, a comparative example of the present embodiment using a general annular conductor 30 will be described with reference to FIG. As shown in the perspective view of FIG. 2, the heating coil 1 of the comparative example is composed of an inner winding 1 a and an outer winding 1 b, and the magnetic flux generated from the heating coil 1 composed of these is the heating coil 1. It passes through the magnetic body 2 having a substantially L-shaped cross section disposed opposite to the lower surface and the outer peripheral side surface, and is linked to the object to be heated 5. When the magnetic flux passes through the magnetic body 2, an annular conductor 30 is disposed outside the magnetic body 2 so as to surround the outer peripheral side surface of the heating coil in order to reduce leakage magnetic flux to the outside of the heating coil 1. . Note that the annular conductor 30 of the comparative example has an integral configuration.

The enlarged view at the bottom of FIG. 2 is an enlarged view of the dotted line in FIG. 2 and schematically shows the current distribution of the annular conductor 30. As shown here, the main current I _A flowing to the annular conductor 30 of the comparative example, the flow in a direction to cancel the magnetic flux generated from the heating coil 1, thereby reducing the magnetic flux leaking to the outside. However, in the portion facing the outer peripheral side surface of the magnetic body 2, since the strong magnetic flux interlinked with the annular conductor 30, it occurs the loop current I _B only the opposing portion. Thus, a combined current of the loop current I _B induced by the main current I _A and the local magnetic flux concentration was flowing to the annular conductor 30.

FIG. 3 shows a current vector diagram of the annular conductor 30 of the comparative example. The loop current I _B flows in the same direction as the main current I _A at the upper part of the annular conductor 30 and flows in the opposite direction to the main current I _A at the lower part. It can be confirmed that the current vector density at the upper part of the body 30 is high and lower at the lower part, and the current is concentrated on the upper part. Thereby, since the alternating current impedance of the annular conductor 30 increases, the current flowing through the annular conductor 30 decreases, the shielding effect deteriorates, and the leakage magnetic flux to the outside increases.

  Next, a present Example using the cyclic | annular conductor 31 divided into 2 is demonstrated using FIG. In addition, duplication description is abbreviate | omitted about the point which is common in a comparative example. As shown in the perspective view of FIG. 4, the annular conductor 31 of the present embodiment is divided into two parts, that is, an upper conductive member 31a and a lower conductive member 31b, and both are laminated and spaced from each other. In addition, a resin spacer (not shown) is provided between the two so that the gap can be maintained at a predetermined size.

The enlarged view at the bottom of FIG. 4 is an enlarged view of the dotted line in FIG. 4 and schematically shows the current distribution of the upper conductive member 31a and the lower conductive member 31b. As shown here, by dividing the annular conductor 3, the cross-sectional area of each of the conductive portion is reduced, reducing the individual loop current I _B. Larger cross-sectional area of the conductive portion in the comparative example, since a relatively large loop current I _B generated, but the current concentration at the annular conductor 30 upper occurring, in this embodiment, the individual loop current I _B Therefore, current concentration at the top of each conductive portion can be suppressed. In FIG. 4, the upper conductive member 31a and the lower conductive member 31b have the same shape, but the upper conductive member 31a is made smaller by making the cross-sectional area of the upper conductive member 31a smaller than the cross-sectional area of the lower conductive member 31b. It is also possible to further suppress power concentration at the top of the.

FIG. 5 shows a current vector diagram of the annular conductor 31 of this embodiment. As shown here, by dividing the annular conductor 31 into the upper conductive member 31a and the lower conductive member 31b, current concentration particularly in the vicinity of the facing portion of the magnetic body 2 is suppressed. Therefore, the effective cross-sectional area through which the current flows is increased as compared with the annular conductor 30 of the comparative example configured with a single component. Thereby, since the alternating current impedance of the annular conductor is reduced, the current flowing through the annular conductor 31 is increased as compared with the comparative example, the shielding effect is enhanced, and the magnetic flux leaked to the outside is reduced.
(Modification)
Next, a modified example of the present embodiment using the annular conductor 32 divided into three parts will be described using the perspective view of FIG. In addition, duplication description is abbreviate | omitted about the point which is common in the above-mentioned structure. In this modification, a configuration in which the annular conductor 32 is divided into an upper conductive member 32a, a middle conductive member 32b, and a lower conductive member 32c is shown. Thus, it goes without saying that the shielding effect is enhanced by the same principle even if the annular conductor 3 is divided into two or more parts.

  As described above, magnetic flux leaking outside the heating coil is reduced by using the annular conductors 31 and 32 of the present embodiment. Moreover, since it becomes possible to supply cooling air from the space | gap between annular conductors, compared with the structure of a comparative example, the effect that the temperature of the heating coil 1 falls and a loss reduces is also acquired.

  Next, the annular conductor 33 of Example 2 will be described with reference to FIG. In addition, duplication description is abbreviate | omitted about the point which is common in the above-mentioned structure.

  As shown here, in this embodiment, the arrangement of the heating coil 1 and the magnetic body 2 is the same as that in the first embodiment, but the structure of the annular conductor 33 is different and the outer surface of the magnetic body 2 is opposed to the outer surface. It is assumed that the part has an integral structure having a slit 7 longer than the length of the outer peripheral part of the magnetic body 2.

By providing such a slit 7, even in the case of using the annular conductor 33 of the integral structure, it is possible to divide the loop current I _B generated in the opposing portion of the magnetic member 2 as shown in Figure 4 below , while maintaining the main current I _a equal to the comparative example, it is possible to reduce the loop current I _B. In the present embodiment, since it is not necessary to reduce the cross-sectional area of the annular conductor 33 except for the facing portion of the magnetic body 2, the effective cross-sectional area through which current flows is increased as compared with the first embodiment, and thus a larger shield. An effect can be obtained. In addition, since the annular conductor 33 is constituted by a single component, the assemblability is improved as compared with the first embodiment.

  Next, the annular conductor 34 of Example 3 is demonstrated using FIG. In addition, duplication description is abbreviate | omitted about the point which is common in the above-mentioned structure.

  As shown here, in the present embodiment, the arrangement of the heating coil 1 and the magnetic body 2 is the same as in the first and second embodiments, but the structure of the annular conductor 34 is different, and the upper conductive member 34a and the lower side are arranged. The upper conductive member 34a is divided into conductive members 34b, and the upper conductive member 34a has a slit 7 at a portion facing the magnetic body 2.

  As shown in FIG. 5 of the first embodiment, when the annular conductor 3 is simply divided into two, it can be seen that a larger current flows in the upper conductive member 31a than in the lower conductive member 31b. Therefore, in this embodiment, by providing the upper conductive member 34a with the slit 7 described in the second embodiment, the actions of the first and second embodiments are combined, and a greater shielding effect can be obtained.

  As described above, by using the annular conductor 34 of the present embodiment, the magnetic flux leaking outside the heating coil is reduced as compared with the first and second embodiments. Further, since the cooling air can be obtained from the gap between the upper conductive member 34a and the lower conductive member 34b and the slit 7 provided in the upper conductive member 34a, the heating coil described in the first and second embodiments is used. As compared with the above, the effect that the temperature of the heating coil is lowered and the loss is reduced is also obtained.

1 heating coil,
1a Inner winding,
1b outer winding,
2 Magnetic material,
3, 30, 31, 32, 33, 34 annular conductor,
4 inverter,
5 heated object,
6 Top plate,
7 Slit,
I _A main current,
I _B loop current

Claims (6)

A heating coil for heating an object to be heated;
A magnetic body disposed opposite to the outer peripheral side surface of the heating coil and guiding a magnetic flux generated from the heating coil to the object to be heated;
A plurality of annular conductors surrounding the outer peripheral side surface of the heating coil outside the magnetic body;
The electromagnetic induction heating device, wherein the plurality of annular conductors are stacked and spaced apart from each other. In the electromagnetic induction heating device according to claim 1,
An electromagnetic induction heating device, wherein the uppermost annular conductor is divided into a plurality of conductive portions by a slit extending in a circumferential direction at a portion facing the magnetic body. In the electromagnetic induction heating device according to claim 1,
An electromagnetic induction heating device, wherein the uppermost annular conductor has a smaller cross-sectional area of the conductive portion than other annular conductors. A heating coil for heating an object to be heated;
A magnetic body disposed opposite to the outer peripheral side surface of the heating coil and guiding a magnetic flux generated from the heating coil to the object to be heated;
An annular conductor that surrounds the outer peripheral side surface of the heating coil outside the magnetic body;
In the electromagnetic induction heating device, the annular conductor is divided into a plurality of conductive portions by a slit extending in a circumferential direction at a portion facing the magnetic body. The electromagnetic induction heating device according to claim 4,
The electromagnetic induction heating device, wherein the uppermost conductive portion has a smaller cross-sectional area than other conductive portions. In the electromagnetic induction heating device according to claim 2 or 4,
The electromagnetic induction heating apparatus according to claim 1, wherein a circumferential length of the slit is longer than a circumferential length of the magnetic body.

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