JP5105475B2 - Induction heating coil - Google Patents

Description

  The present invention relates to an induction heating coil for inductively heating an object to be heated based on passing a high-frequency current through a coil conductor.

  Conventionally, the only metal that can be heated by the induction heating coil is an iron-based metal having a high magnetic permeability, but in recent years, heating of metals other than iron, such as copper and aluminum, is also desired. In particular, in an induction heating cooker in which an induction heating coil is applied to a cooker, there is a high demand for using a copper pan or an aluminum pan in addition to an iron pan. Inductive heating of copper pans and aluminum pans requires a high-frequency current of 40 to 100 kHz, which is higher than 20 to 30 kHz suitable for iron pans, to flow through the induction heating coil because their permeability is lower than that of iron pans. is there. The higher the frequency, the higher the effective resistance because the so-called skin effect causes a high-frequency current to flow only near the surface of the conductor. Therefore, as a method of increasing the surface area and effectively reducing the resistance, instead of the conventionally used conductor (conductor with a diameter of 0.3 to 0.5 mm), a thinner conductor (diameter of 0.1 mm or less) For example, it is considered to use a large number of conductive wires having a diameter of 0.05 mm (see, for example, Patent Document 1).

Specifically, a structure as shown in FIG. 7 is considered. This is, for example, by twisting seven small assembly wires 1 formed by bundling 60 strands having a diameter of 0.05 mm (insulating layer is provided on the surface of a conductor) and making these medium assembly wires 2 and, further, three middle assembly wires 2 are twisted to form assembly wires 3. The assembly line 3 is covered with two layers of an insulating layer 4 and a fusion layer 5 made of fluororesins having different melting points. Among them, the inner insulating layer 4 uses PFA (melting point: 300 ° C. to 310 ° C.) as a fluororesin having a high melting point, and the outer fusion layer 5 is ETFE or FEP which is a fluororesin having a melting point lower than that of the insulating layer 4. (Melting point is 250 ° C. to 270 ° C.). The long one thus configured is referred to as a coil conductor 6. And in the state which wound this coil conducting wire 6 in the predetermined | prescribed shape (for example, multistage spiral shape), by heating and fuse | melting the outer side fusion | melting layer 5, the adjacent fusion | melting layers 5 are mutually connected. A configuration is adopted in which the shape of the coil conductor 6 is stabilized by being fixed. What was comprised in this way is used as an induction heating coil. By passing a high frequency current of 40 to 100 kHz to the induction heating coil having such a configuration, it is possible to induction heat the copper pan or the aluminum pan.

However, the configuration shown in FIG. 7 has the following drawbacks.
1. The outer layer of the coil conductor 6 is a two-layer structure in which an insulating layer 4 made of a fluororesin (PFA) having a high melting point is provided on the inner side, and a fusion layer 5 made of a fluororesin (ETFE or FEP) having a lower melting point is provided on the outer side. Although it has a structure, both layers are fluororesins (thermoplastic resins) having relatively close melting points. For this reason, when the fusion layer 5 is melted and solidified in order to solidify the coil conductor 6 into a predetermined shape, it is necessary to melt only the outer fusion layer 5, but temperature control at that time is difficult (insulating layer) 4 may also melt).

2. Fluororesin has a large shrinkage ratio with respect to temperature, and is easily broken or swelled when melted and solidified, making quality control difficult.
3. Since both the insulating layer 4 and the fusion layer 5 are fluororesins and are a combination of thermoplastic resins, not only the fusion layer 5 but also the insulation layer 4 may be broken when the fusion layer 5 is melted and solidified. If the insulating layer 4 is torn, the strands of the inner assembly wire 3 are exposed, and the insulation layer of the strands cannot be withstood at the time of use, and there is a risk of causing dielectric breakdown (voltage breakdown).

  4). When the insulating layer 4 and the fusion layer 5 are formed of fluororesin, they are formed in a tube shape by melt extrusion or the like. In this case, heat is applied to the coil conductor 6 when the fusion layer 5 is melted and solidified. Then, since the wires move, or the air between the wires or the air in the assembly wire 3 expands, the bulge is generated from the inside of the insulating layer 4, so that the insulating layer 4 and the fusion layer 5 may swell and be broken. There is.

  The present invention has been made in view of the above-described circumstances, and the object thereof is to provide an insulating layer and a fusion layer on the outside of a coil conductor, and when the fusion layer is melted and solidified, the insulation layer An object of the present invention is to provide an induction heating coil that can prevent swelling and tearing as much as possible and has stable quality.

In order to achieve the above object, the present invention provides an induction heating coil for inductively heating an object to be heated on the basis of flowing a high-frequency current through the coil conductor, and the coil conductor is insulated from the outer periphery of the conductor. An assembly wire formed by twisting together a strand having a layer or a small assembly wire in which the strands are bundled, a heat-resistant and electrically insulating inorganic material, or an organic material non-melting thermosetting resin or An insulating layer provided so as to cover the outer periphery of the assembly line by winding an insulating tape formed of a thermoplastic resin that is difficult to melt around the outer periphery of the assembly line, and the outer periphery of the insulating layer provided so as to cover the insulating tape from a fusion layer having a melting point which is formed by a lower thermoplastic resin, the coil conductors of electric current to the coil conductor in a state wound in a predetermined shape Exothermed the coil conductor, characterized in that a configuration in which by fixing the bonding layer between the adjacent by melting and solidifying the melt adhesive layer in the heat stabilizing the shape of the coil conductor.

  Of the insulating layer and the fusion layer provided outside the coil conductor, the inner insulating layer is formed of an inorganic material having heat resistance and electrical insulation, a non-melting thermosetting resin, or a thermoplastic resin that is difficult to melt. Since the insulating tape is formed, it is strong against heat and does not melt or hardly melts. For this reason, when the fusion layer is melted and solidified in order to solidify the coil conductor into a predetermined shape, temperature control when only the outer fusion layer is melted can be easily performed. In addition, since the insulating layer formed of the insulating tape is hardly deformed by heat and is not easily torn, even if the fusion layer is torn, it is possible to prevent the strands of the inner assembly line from being exposed as much as possible. be able to. Furthermore, since the assembly wires are clamped with insulating tape, when the fused layer is melted and solidified, it is possible to prevent the strands from moving even if heat is applied to the coil conductors, and the insulating layer expands due to the expansion of the internal air. As a result, the swelling of the fusion layer can be suppressed as much as possible, and the insulation layer and the fusion layer can be prevented from being broken. Along with this, it becomes possible to simplify the structure of the jig for preventing the swelling of the insulating layer and the fusion layer.

Hereinafter, an embodiment in which the present invention is applied to an induction heating cooker will be described with reference to FIGS.
First, a schematic configuration of the induction heating cooker will be described with reference to FIG. A top plate 13 is mounted on the top surface of the casing 12 of the induction heating cooker 11 so as to close the top opening of the casing 12. Inside the housing 12, a coil unit 15 (see FIG. 6) including the induction heating coil 14 of the present invention is disposed, and a control device 16 for controlling the induction heating coil 14 is disposed. . The control device 16 is configured by mounting a plurality of electronic components 18 on a printed wiring board 17. On the top plate 13, a metal cooking pan 19 that constitutes an object to be heated is placed. As shown in FIG. 6, the induction heating coil 14 is formed by spirally winding a coil conductor 20 to be described later, and is disposed near the lower surface of the top plate 13.

  In this configuration, when a cooking pan 19 is placed on the top plate 13, a magnetic flux is generated when a high-frequency current is passed through the coil conductor 20 of the induction heating coil 14, and the magnetic cooking pan 19 is caused by the magnetic flux. An induction current (eddy current) flows, and the cooking pot 19 generates heat due to the loss of eddy current at that time, and the cooking object in the cooking pot 19 is heated by this heat.

Next, the structure of the coil conducting wire 20 constituting the induction heating coil 14 will be described with reference to FIGS. In FIG. 3 which shows sectional drawing of the coil conducting wire 20, the small assembly wire 21 is comprised by twisting 20 strands 22 (refer FIG. 4 ), for example. As shown in FIG. 4 , each strand 22 is configured by covering an outer peripheral portion of a thin copper conductor 22a having a diameter of, for example, 0.05 mm with an insulating layer 22b having electrical insulation. The insulating layer 22b may be a double layer. A bundled wire 23 is formed by bundling, for example, 50 the small bundled wires 21 and twisting them together. Therefore, the assembly wire 23 has a configuration in which about 1000 strands 22 are twisted together.

  Then, an insulating tape 25 (see FIGS. 1 and 2) is wound around the outer periphery of the assembly line 23 to provide an insulating layer 25 on the outer periphery of the assembly line 23. In this case, the insulating tape 24 is made of a thermosetting resin polyimide resin which is a non-melting resin among organic materials excellent in heat resistance and electrical insulation, and has a thickness of 0.025 mm (25 μm), A tape having a width W1 (see FIG. 2) of 7 mm is used, and this insulating tape 24 is wound in a spiral shape so as to partially overlap (lap width W2 (see FIG. 2) is about 2 mm). The thickness of the insulating tape 24 is preferably 0.2 mm to 0.01 mm in consideration of handleability and quality. Further, the wrap width W2 when the insulating tape 24 is spirally wound is preferably 1/2 to 1/5 of the width W1 of the insulating tape 24 so that the strands 22 of the inner assembly line 23 are not exposed. .

  The material of the insulating tape 24 may be a polyamide-imide resin as long as it is a non-melting thermosetting resin excellent in heat resistance and electrical insulation among organic materials, and even a thermoplastic resin melts. If it is a difficult thermoplastic resin, for example, a thermoplastic polyimide resin (melting point: 388 ° C.) or PTFE (melting point: 327 ° C.) may be used. Furthermore, the material of the insulating tape 24 may be an inorganic material excellent in heat resistance and electrical insulation, such as mica.

  A fusion layer 26 is provided on the outer periphery of the insulating layer 25 so as to cover the insulating layer 25. This fusion layer 26 is made of FEP (tetrafluoroethylene / hexafluoropropylene copolymer) (melting point: 250 ° C. to 270 ° C.), which is a thermoplastic resin fluororesin having a melting point lower than that of the insulating tape 24 of the insulating layer 25. It is provided in a tube shape by melt extrusion molding. The thickness of the fusion layer 26 is 0.2 to 0.3 mm. With such a configuration, a long coil conductor 20 is formed.

  As shown in FIGS. 5 and 6, the coil conductor 20 having such a configuration is disposed on a coil base 27 of the coil unit 15 by being wound into a predetermined shape, in this case, a plurality of spirals. Yes. Terminals 28 are fixed to both ends of the coil conductor 20 by heat caulking, and a current is passed between the terminals 27 for a short time to cause the coil conductor 20 (each element wire 22) to generate heat, thereby melting the fusion layer 26. By adhering to each other, the adjacent fusion layers 26 are fixed to each other, and the coil conductor 20 is solidified with a stable shape. In this way, the induction heating coil 14 is formed. In the state where the induction heating coil 14 is disposed in the induction heating cooker 1, the terminals 28 at both ends of the coil conductor 20 are connected to the terminal connection portions 29 provided on the printed wiring board 17 as shown in FIG. 5. The

According to the above configuration, the following operational effects can be obtained.
With the cooking pan 19 placed on the top plate 13, the cooking pan 19 generates heat based on passing a high-frequency current through the induction heating coil 14, and the cooking object in the cooking pan 19 is heated by this heat. Is done. At this time, even if the cooking pan 19 is a copper pan or an aluminum pan other than iron, the cooking object in the cooking pan 19 is heated and cooked by passing a high frequency current of 40 to 100 kHz to the induction heating coil 14. can do.

  Of the insulating layer 25 and the fusion layer 26 provided outside the coil conductor 20 in the induction heating coil 14, the inner insulating layer 25 is formed of a polyimide resin, which is a thermosetting resin having heat resistance and electrical insulation. Since it is constituted by the insulating tape 24, it is strong against heat and does not melt. Therefore, when the fusion layer 26 is melted and solidified in order to solidify the coil conductor 20 into a predetermined shape, the temperature control when only the outer fusion layer 26 is melted can be facilitated.

  The insulating layer 25 formed by the insulating tape 24 is not easily deformed by heat and is not easily torn. Therefore, even if the fusion layer 26 is torn, the strands 22 of the inner assembly line 23 are exposed. As much as possible, it is possible to prevent dielectric breakdown (breakdown of breakdown voltage) from occurring.

  Since the assembly wire 23 is fastened by the insulating tape 24, the wire 22 can be prevented from moving even if the coil conductor 20 (each wire 22) is heated by heating when the fusion layer 26 is melted and solidified. At the same time, it is possible to prevent the insulating layer 25 from expanding due to the expansion of the internal air, and thus to suppress the swelling of the fusion layer 26 as much as possible, and to prevent the insulation layer 25 and the fusion layer 26 from being broken. Along with this, it is possible to simplify the structure of the jig that prevents the insulating layer 25 and the fusion layer 26 from swelling.

  Here, the insulating layer 25 may be formed in a long cylindrical shape (tube shape) in the same manner as the fusion layer 26 instead of winding the insulating tape 24. However, when the polyimide resin constituting the insulating layer 25 is formed in a simple cylindrical shape, it is not flexible and cannot be wound even if the coil conductor 20 is wound in a spiral shape. There was a problem that could not be done. On the other hand, as in this embodiment, the polyimide resin insulating tape 24 is used, and the insulating tape 24 is wound around the outer periphery of the assembly line 23 in a spiral manner, thereby obtaining flexibility. Thus, the coil conductor 20 can be wound into a predetermined shape. Then, by melting and solidifying the fusion layer 26 provided on the outer peripheral portion of the insulating layer 25, the coil conductor 20 can be held in a wound shape. Even when mica is used for the insulating tape, the same effect can be obtained.

The insulating layer 25 has a structure in which the insulating tape 24 is spirally wound so that a part of the insulating tape 24 overlaps, so that the strands 22 of the inner assembly line 23 can be prevented from being exposed from the insulating layer 25, and thus insulated. It is also possible to prevent destruction.
By using a tape having a thickness of 0.2 mm to 0.01 mm as the insulating tape 24, the handleability is good and the quality as the insulating layer 25 can be ensured.

The present invention is not limited to the above-described embodiment, and can be modified or expanded as follows.
The collective wire 23 of the coil conducting wire 20 can also be formed by putting a large number of the strands 22 together. Further, similarly to the conventional FIG. 7, it is also possible to form a plurality of small set lines obtained by combining a plurality of strands 22 to form a medium set line, and to form a plurality of medium set lines. .
Although the example which applied the induction heating coil 14 of this invention to the induction heating cooking appliance was illustrated as an induction heating apparatus, it is applicable also to the induction heating coil of induction heating apparatuses other than an induction heating cooking appliance.

The perspective view for demonstrating the structure of the coil conducting wire which shows one Embodiment of this invention Enlarged perspective view of the part wrapped with insulating tape Cross section of coil conductor Cross section of strand Longitudinal section of induction heating cooker Coil unit perspective view FIG. 3 equivalent view showing a conventional example

Explanation of symbols

  In the drawings, 11 is an induction heating cooker, 14 is an induction heating coil, 15 is a coil unit, 19 is a cooking pan (heated body), 20 is a coil conductor, 21 is a small assembly wire, 22 is a strand, and 22a is Conductor, 22b is an insulating layer, 23 is an assembly line, 24 is an insulating tape, 25 is an insulating layer, and 26 is a fusion layer.

Claims (3)

An induction heating coil for inductively heating an object to be heated based on passing a high-frequency current through a coil conductor,
The coil conductor is
An assembly wire formed by twisting together a strand having an insulating layer on the outer periphery of the conductor or a small assembly wire in which the strands are bundled;
An assembly line is formed by winding an insulating tape formed of an inorganic material having heat resistance and electrical insulation, or a non-melting thermosetting resin of an organic material or a thermoplastic resin that is difficult to melt around the outer periphery of the assembly line. An insulating layer provided to cover the outer periphery of the
The outer peripheral portion of the insulating layer is provided so as to cover the outer peripheral portion, and includes a fusion layer formed of a thermoplastic resin having a lower melting point than the insulating tape,
In the state where the coil conductor is wound into a predetermined shape, an electric current is passed through the coil conductor to heat the coil conductor, and the fusion layers adjacent to each other are melted and solidified by the heat. An induction heating coil characterized by being configured to be fixed to stabilize the shape of the coil conductor.   The induction heating coil according to claim 1, wherein the insulating layer is formed by spirally winding the insulating tape so that a part of the insulating tape overlaps.   The induction heating coil according to claim 1 or 2, wherein the insulating tape has a thickness of 0.2 mm to 0.01 mm.

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