JP6875934B2 - Electromagnetic induction heating device - Google Patents

Description

The present invention relates to an electromagnetic induction heating device that induces and heats a metal pot.

When a load such as a metal pot is placed on the top plate of an electromagnetic induction heating cooker, a high-frequency current is passed from the high-frequency inverter to the heating coil, and an eddy current is generated in the metal pot placed close to the coil. It is made to generate heat by the electric resistance of the metal pot itself.

In this electromagnetic induction heating cooker, if the magnetic flux generated from the heating coil leaks to the outside, it causes an increase in the magnetic field strength of the emitted noise and a malfunction of the control circuit. Therefore, as a countermeasure against the leakage magnetic flux, an electromagnetic shield is provided around the heating coil. An annular conductor is provided as a conductive member for use.

For example, in the abstract of Patent Document 1, when a plurality of shielded electric wires (conductive members for electromagnetic shielding) are arranged side by side, the outer shielded electric wire has a smaller conductor cross-sectional area than the inner shielded electric wire. Further, there is disclosed an induction heating device that improves ventilation to the upper surface of the heating coil by arranging the upper surface of the outer shielded electric wire lower than that of the inner shielded electric wire.

JP-A-2002-93561

Patent Document 1 described above can also reduce the magnetic field leaked to the outside, but has the following problems.

In Patent Document 1, a plurality of electromagnetic shielding conductive members (shielded electric wires) are arranged side by side with respect to the heating coil. In this case, since the magnetic flux generated from the heating coil is attenuated 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 shield conductive members are arranged concentrically, there is a problem that a sufficient shield effect cannot be obtained with the electromagnetic shield conductive member on the outer peripheral side.

Therefore, in the present invention, the electromagnetic induction heating device can realize sufficient cooling of the heating coil as in 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, the electromagnetic induction heating device of the present invention is arranged to face the heating coil for heating the object to be heated and the outer peripheral side surface of the heating coil, and the magnetic flux generated from the heating coil is applied to the object to be heated. a magnetic body for guiding, comprising a plurality of annular conductors surrounding the outer circumferential surface of the heating coil on the outside than the magnetic body, an annular conductor of the plurality of the stacked spaced a gap, the top of annular conductors , The cross-sectional area of the conductive part is smaller than that of other annular conductors .

According to the present invention, it is possible to provide an electromagnetic induction heating device in which the shielding effect of the electromagnetic shielding conductive member is enhanced and the leakage magnetic field is small.

Basic configuration diagram of electromagnetic induction heating device Schematic diagram of the current flowing through the electromagnetic shield conductive member of the comparative example Current vector diagram flowing through the electromagnetic shield conductive member of the comparative example Schematic diagram of the current flowing through the electromagnetic shield conductive member of Example 1. Vector diagram of current flowing through the electromagnetic shield conductive member of Example 1. Deformation example of the heating coil of the electromagnetic induction heating device of Example 1 Perspective view of the heating coil of the electromagnetic induction heating device of the second embodiment Perspective view of the heating coil of the electromagnetic induction heating device of the third embodiment.

Hereinafter, examples 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 device according to a first embodiment of the present invention. This electromagnetic induction heating device induces and heats an object to be heated 5 (a metal pot or the like) placed on a top plate 6, and inside the heating coil 1 and a magnetic flux generated from the heating coil 1. A magnetic body 2 leading to the object to be heated 5 and an annular conductor 3 which is a conductive member for electromagnetic shielding surrounding 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 induced and heated.

First, a comparative example of this example using a general annular conductor 30 will be described with reference to FIG. As shown in the perspective view on FIG. 2, the heating coil 1 of the comparative example is composed of an inner winding 1a and an outer winding 1b, and the magnetic flux generated from the heating coil 1 composed of these is the heating coil 1. It interlinks with the object to be heated 5 through a magnetic material 2 having a substantially L-shaped cross section arranged opposite to the lower surface and the outer peripheral side surface. An annular conductor 30 is arranged outside the magnetic body 2 so as to surround the outer peripheral side surface of the heating coil in order to reduce the magnetic flux leaking to the outside of the heating coil 1 when the magnetic flux passes through the magnetic body 2. .. The annular conductor 30 of the comparative example has an integral structure.

The enlarged view at the bottom of FIG. 2 is an enlargement of the dotted line portion at the top of 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. Loop current I _B flows in the main current I _A in the same direction at the top of the annular conductor 30, to flow into the main current I _A and the reverse direction at the bottom, in the vicinity of the opposing portion of the magnetic body 2 of the comparative example, the annular conductive It can be confirmed that the current vector density in the upper part of the body 30 is high and low in the lower part, and the current is concentrated in the upper part. As a result, the AC impedance of the annular conductor 30 increases, so that the current flowing through the annular conductor 30 decreases, the shielding effect deteriorates, and the magnetic flux leakage to the outside increases.

Next, this embodiment using the annular conductor 31 divided into two will be described with reference to FIG. The points in common with the comparative example will be omitted. As shown in the perspective view on FIG. 4, the annular conductor 31 of this embodiment is divided into an upper conductive member 31a and a lower conductive member 31b, both of which are laminated and arranged with a gap between them. 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 enlargement of the dotted line portion at the top of FIG. 4, and schematically shows the current distributions 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 Since the amount is reduced, it is possible to suppress the current concentration at the upper part of each conductive portion. In FIG. 4, the upper conductive member 31a and the lower conductive member 31b have the same shape, but by making the cross-sectional area of the upper conductive member 31a smaller than the cross-sectional area of the lower conductive member 31b, the upper conductive member 31a The power concentration at the upper part of the may be further suppressed.

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 an upper conductive member 31a and a lower conductive member 31b, current concentration is suppressed particularly in the vicinity of the facing portion of the magnetic body 2. Therefore, the effective cross-sectional area through which the current flows is increased as compared with the annular conductor 30 of the comparative example, which is composed of a single component. As a result, the AC impedance of the annular conductor is reduced, so that the current flowing through the annular conductor 31 is increased as compared with the comparative example, the shielding effect is strengthened, and the magnetic flux leaked to the outside is reduced.
(Modification example)
Next, a modified example of this embodiment using the annular conductor 32 divided into three parts will be described with reference to the perspective view of FIG. The points in common with the above configuration will be omitted. In this modification, the annular conductor 32 is divided into three parts, an upper conductive member 32a, a middle conductive member 32b, and a lower conductive member 32c. In this way, 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.

As described above, by using the annular conductors 31 and 32 of this embodiment, the magnetic flux leaking to the outside of the heating coil is reduced. Further, since the cooling air can be supplied from the voids between the annular conductors, the effect that the temperature of the heating coil 1 is lowered and the loss is reduced can be obtained as compared with the configuration of the comparative example.

Next, the annular conductor 33 of the second embodiment will be described with reference to FIG. 7. The points in common with the above configuration will be omitted.

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 faces the outer surface of the magnetic body 2. The portion has an integral structure having a slit 7 longer than the length of the outer peripheral portion 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 this 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 the current flows increases as compared with the first embodiment, and thus a larger shield The effect can be obtained. Further, since the annular conductor 33 is composed of a single component, the assembling property is improved as compared with the first embodiment.

Next, the annular conductor 34 of Example 3 will be described with reference to FIG. The points in common with the above configuration will be omitted.

As shown here, in this 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 from that of the upper conductive member 34a and the lower side. It is divided into a conductive member 34b, and the upper conductive member 34a has a slit 7 in 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 through the upper conductive member 31a than that of the lower conductive member 31b. Therefore, in this embodiment, by providing the slit 7 described in the second embodiment in the upper conductive member 34a, the actions of the first and second embodiments can be combined to obtain a larger shielding effect.

As described above, by using the annular conductor 34 of this embodiment, the magnetic flux leaking to the outside of the heating coil is reduced as compared with Examples 1 and 2. Further, since it is possible to obtain cooling air 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 coils described in Examples 1 and 2 can be obtained. It is also possible to obtain the effect that the temperature of the heating coil is lowered and the loss is reduced as compared with the above.

1 heating coil,
1a Inner winding,
1b outer winding,
2 magnetic material,
3, 30, 31, 32, 33, 34 annular conductors,
4 Inverter,
5 Heated object,
6 top plate,
7 slits,
I _A main current,
I _B loop current

Claims (1)

A heating coil that heats the object to be heated,
A magnetic material that is arranged to face the outer peripheral side surface of the heating coil and guides the magnetic flux generated from the heating coil to the object to be heated.
A plurality of annular conductors outside the magnetic material and surrounding the outer peripheral side surface of the heating coil are provided.
The plurality of annular conductors are laminated and arranged with a gap between them .
The uppermost annular conductor is an electromagnetic induction heating device characterized in that the cross-sectional area of the conductive portion is smaller than that of other annular conductors.

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