JP2002299021A - Heating coil for induction heating device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a small and low-cost induction heating device by realizing a simple-structured inexpensive heating coil, without increasing the loss. SOLUTION: In the heating coil for the induction heating device, an electrical conductor 13 is wound around spirally separated by intervals, and a magnetic material 14 is inserted into approx, one turn part of the intervals, so that the magnetic materials are distributed continuously or separately, and the magnetic material is not inserted into at least one interval adjacent to the magnetic material.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an induction heating device used in ordinary households, restaurants, factories, and the like, and more particularly to a heating coil thereof.

[0002]

2. Description of the Related Art The heating structure of a conventional induction heating apparatus will be described by taking an induction heating cooker as an example.

FIG. 7 is a sectional view of a conventional induction heating cooker.
1 is a heating coil for generating a high-frequency magnetic field, 2 is an object to be heated which is induction-heated by a high-frequency magnetic field generated from the heating coil 1, and 3 is an inverter circuit for supplying a high-frequency current to the heating coil 1. Not connected, but connected to heating coil 1. Reference numeral 4 denotes a top plate on which the object to be heated 2 is placed on its upper surface, the material being ceramic. Reference numeral 5 denotes a housing, and 6 denotes a coil table on which the heating coil 1 is placed.

[0004] The coil wire of the heating coil 1 has a diameter of 0.3 m.
It is configured by twisting about 30 strands of about m to 0.5 mm (Litz wire configuration). The twist pitch is about several centimeters, and each element wire is configured to repeat the vertical positional relationship with the lower surface of the object 2 several times during one turn.

On the other hand, as a configuration for realizing the heating coil 1 with a simple configuration that does not use a litz wire, a system in which a flat coil is configured in a layered manner has been proposed in, for example, Japanese Utility Model Publication S62-106497. In this method, the heating coil 1 can be formed by, for example, a press method, and there is a possibility that a very inexpensive one can be obtained. Further, by adopting a structure in which the coil is alternately laminated with the insulating layer, the thickness of one coil can be reduced, and a structure in which an increase in skin resistance can be suppressed.

[0006]

However, a heating coil having a litz wire configuration or a flat coil having a large number of turns is easily affected by a magnetic field from an adjacent coil current. FIG. 8 is a schematic diagram of an electromagnetic environment around a neighboring coil, where 7 is a coil wire, and 8 is a magnetic flux generated from the coil wire. In FIG. 8, it is assumed that a current flows through the coil wire 7 from the near side of the drawing to the other side. Coil wire 7
Is distributed in a direction away from the adjacent coil wires due to the magnetic flux 8 generated from the adjacent coil wires. In FIG. 8, the shade of the color of the coil wire 7 indicates the current density, and a dark portion indicates that the current density is high. A series of phenomena causing the bias of the current distribution is generally called a proximity effect. Due to this proximity effect, the heating coil resistance increases and the heating coil loss increases. Since the effect of the proximity effect increases as the distance between the coil wires 7 decreases, the heating coil loss increases in a heating coil having a litz wire configuration or a flat coil having a large number of turns.
It is disadvantageous in terms of cooling and efficiency.

Further, the present inventors have studied a configuration in which a magnetic body is inserted between all the coils for the purpose of reducing the proximity effect. This is because the magnetic field concentrates on the magnetic material inserted between the coils,
The aim is to reduce the magnetic field passing through the coil, thereby reducing the effect of the proximity effect. However, the experiment showed that the effect of reducing the proximity effect was not obtained partially. Considering the electromagnetic environment around the coil, as shown in FIG. 9, the magnetic flux distribution around the heating coil is a flat concentric ellipse whose long side is parallel to the heating coil, and the direction of the magnetic field is substantially parallel to the coil surface. There are parts. Therefore, it is considered that a magnetic field that is going to pass through a certain magnetic body is easily attracted to an adjacent magnetic body and passes through a coil. As a result, there is a portion where the proximity effect becomes significant.

The present invention solves the above-mentioned conventional problems, and realizes a heating coil having a loss similar to or less than that of a conventional heating coil by a simple and easy method, allowing a margin in cooling performance and the like, and as a result, it is inexpensive. It is an object of the present invention to provide a simple induction heating device.

[0009]

In order to solve the above-mentioned problems, a heating coil for an induction heating device according to the present invention is formed by winding an electric conductor spirally at intervals, and continuously winding the electric conductor for approximately one turn of the interval. Alternatively, a magnetic body is inserted so as to be discretely distributed, and a plurality of magnetic bodies are radially distributed so as not to insert another magnetic body in at least one interval radially adjacent to the magnetic body. Things. Thereby, in a portion where the direction of the magnetic field is substantially parallel to the coil surface, the magnetic field that is going to pass through a certain magnetic body is not attracted to the adjacent magnetic body, so that the proximity effect is suppressed and the loss is reduced. It can be a heating coil for an induction heating device.

[0010]

According to the first aspect of the present invention, an electric conductor is spirally wound at intervals and a magnetic material is distributed so as to be distributed continuously or discretely for approximately one turn of the interval. Inserted, in at least one interval radially adjacent to the magnetic body, a plurality of magnetic bodies are distributed in the radial direction so as not to insert another magnetic body, so that the direction of the magnetic field with respect to the coil surface And suppress the proximity effect in the part that is almost parallel,
It is possible to provide a heating coil for an induction heating device with reduced loss.

According to a second aspect of the present invention, in the configuration according to the first aspect, in particular, by inserting a magnetic body between at least middle electric conductors, the direction of the magnetic field is substantially equal to the coil surface. It is possible to suppress the proximity effect in the middle portion, which is likely to be parallel, and effectively reduce the loss of the heating coil for the induction heating device.

According to a third aspect of the present invention, the electric conductor according to the first or second aspect is formed such that a cross-sectional corner of the electric conductor is formed into a curved shape or a straight line so that a magnetic field passes therethrough and a current is concentrated. Eliminating the corner portions of the electric conductor that is easy to perform suppresses the proximity effect and makes it possible to reduce the loss of the heating coil for the induction heating device.

[0013]

(Embodiment 1) Hereinafter, a first embodiment of the present invention will be described with reference to the drawings. FIG. 1 shows a cross section of the heating coil. 13 is an electric conductor, and 14 is a magnetic material. The magnetic body 14 is provided between the electric conductors 13.
Every other is inserted. Further, in the present embodiment, an example is described in which the nonmagnetic material inserted between the electric conductors 13 into which the magnetic material 14 is not inserted is made of air.

In the above configuration, when performing induction heating,
A high-frequency magnetic field is generated by the high-frequency current flowing through the electric conductor 13. At this time, as shown in FIG. 2, the magnetic flux distribution around the heating coil has a long side parallel to the heating coil and has a flat concentric elliptical shape, and a portion where the direction of the magnetic field is substantially parallel to the coil surface is large. . Therefore, if the distance between the adjacent magnetic bodies 14 is short, the magnetic field is attracted to the magnetic bodies 14 and the magnetic field passing through the electric conductor 13 increases,
Proximity effects increase losses. However, in the present embodiment, the proximity effect is suppressed by increasing the distance between the adjacent magnetic members 14, the magnetic field passing through the electric conductor 13 is effectively concentrated on the magnetic member 14, and the electric conductor 13 Has a configuration in which a magnetic field does not pass through. Therefore, it is possible to reduce the loss of the heating coil.

In this embodiment, an example is described in which the magnetic members 14 are inserted at every other position between the electric conductors 13. However, two or more intervals where the magnetic members 14 are not inserted may be provided. .

The magnetic body 14 may be inserted into the entire turn for one turn, or may be arranged partially or discretely with an interval.

(Embodiment 2) Next, a second embodiment of the present invention will be described with reference to the drawings. FIG. 3 shows a cross section of the heating coil. Reference numeral 18 denotes an electric conductor, and 19 denotes a magnetic material. The magnetic body 19 is inserted every other one of the middle conductors of the electric conductor 18. Here, the middle part refers to an intermediate part between the inner part and the outer part. Further, in the present embodiment, an example is described in which the non-magnetic material inserted between the electric conductors 18 into which the magnetic material 19 is not inserted is made of air.

In the above configuration, particularly in the middle portion where the direction of the magnetic field tends to be substantially parallel to the coil surface, the effect of the magnetic field from the adjacent electric conductor is effectively reduced, the proximity effect is suppressed, and the heating coil is prevented. Can be reduced.

In this embodiment, an example is described in which the magnetic body 19 is inserted between every other one of the electric conductors 18. However, the present invention is not limited to this.

Further, it has been found from experiments by the inventors that it is effective to adopt the configuration described in the present embodiment particularly at a portion that is three turns or more from the inner circumference and one turn or less from the outer circumference.

(Embodiment 3) Next, a third embodiment of the present invention will be described with reference to the drawings. FIG. 4 shows a cross section of the heating coil. Reference numeral 20 is composed of an electric conductor. The corners of the electric conductor 20 are curved.

[0022] In the above configuration, particularly, the shape of the corner of the electric conductor 20 through which the magnetic field easily passes is made to be a curved surface,
By reducing the passing magnetic field and suppressing the proximity effect, it becomes possible to reduce the concentration of current and reduce the loss of the heating coil.

(Embodiment 4) Next, a fourth embodiment of the present invention will be described with reference to the drawings. In the third embodiment, a single electric conductor is used. However, in this embodiment, as shown in FIG. 5, four insulated electric conductors 21 are formed in a laminated shape, and the uppermost layer and the lower layer are formed. Only the layer has curved corners. With this configuration also, the proximity effect can be suppressed by reducing the current concentration at the corners.

Embodiment 5 Next, a fourth embodiment of the present invention will be described with reference to the drawings. In the fourth embodiment, four insulated electric conductors 21 are formed in a laminated shape,
Only the uppermost layer and the lower layer have curved corners. However, in this embodiment, as shown in FIG. 6, the corners are cut in a curved line or cut straight in each layer. Shape. Also with this configuration, the proximity effect can be suppressed by reducing the current concentration at the corners.

[0025]

As described above, according to the first to third aspects of the present invention, it is possible to suppress the proximity effect due to the magnetic field and reduce the loss of the heating coil.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view illustrating a schematic configuration of a heating coil for an induction heating device according to a first embodiment of the present invention.

FIG. 2 is a diagram showing the same magnetic flux distribution.

FIG. 3 is a cross-sectional view illustrating a schematic configuration of a heating coil for an induction heating device according to a second embodiment of the present invention.

FIG. 4 is a diagram illustrating an example of a cross-sectional view illustrating a schematic configuration of a heating coil for an induction heating device according to a third embodiment of the present invention.

FIG. 5 is a diagram illustrating an example of a cross-sectional view illustrating a schematic configuration of a heating coil for an induction heating device according to a fourth embodiment of the present invention.

FIG. 6 is a diagram illustrating an example of a cross-sectional view illustrating a schematic configuration of a heating coil for an induction heating device according to a fifth embodiment of the present invention.

FIG. 7 is a sectional view showing a schematic configuration of a conventional induction heating device.

FIG. 8 is a schematic diagram of an electromagnetic environment around a nearby coil;

FIG. 9 is a diagram showing a magnetic flux distribution of a conventional induction heating device.

[Explanation of symbols]

 9 Electric conductor 10 Magnetic material

 ──────────────────────────────────────────────────続 き The continuation of the front page F term (reference) 3K051 AA08 AD03 CD43

Claims (3)

[Claims] An electric conductor is spirally wound with an interval therebetween, and a magnetic material is inserted so as to be distributed continuously or discretely for approximately one turn of the interval, and is radially adjacent to the magnetic material. A heating coil for an induction heating device in which a plurality of magnetic materials are distributed in a radial direction so that another magnetic material is not inserted into at least one matching interval. 2. The heating coil for an induction heating device according to claim 1, wherein a magnetic material is inserted between at least the electric conductors in the middle part. 3. The electric conductor according to claim 1, wherein a cross-sectional corner of the electric conductor has a curved shape or a shape cut in a straight line.
4. The heating coil for an induction heating device according to claim 1.