JPH11195481A - Electromagnetic shielding core and fitting structure for core - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electromagnetic shielding core allowing no occurrence of the crack or the chip of a core main body, and capable of increasing permeability, preventing the separation of the laminate core main body. SOLUTION: A core main body 18 molded by soft magnetic powder 18a is arranged crossing the magnetic flux generation coil 14 of a magnetic induction heating device, and the core main body 18 is covered by a box 19 comprising a predetermined nonconductor. The box 19 comprising the nonconductor is formed of resin or rubber, and the soft magnetic powder 18a is formed of iron amorphous, cobalt amorphous, or the like. An electromagnetic shielding core 17 is screwed to the bottom face of an outer furnace 12 with the added magnetic flux generation coil 14 of the electromagnetic induction heating device in a state sandwiching the magnetic flux generation coil 14.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electromagnetic induction heating system (hereinafter referred to as induction heating for short).
Shielding of AC magnetic and electric fields leaking from magnetic flux generating coils used in electromagnetic induction heating devices such as electromagnetic cookers, electromagnetic rice cookers, electromagnetic water heaters (so-called electric pots), electromagnetic warming devices, and high-frequency heaters The present invention relates to an electromagnetic shield core for the purpose of so-called electromagnetic shield) and a mounting structure of the core.

[0002]

2. Description of the Related Art Various types of heaters for business use and home use are known as electromagnetic induction heating devices utilizing the IH system.
For example, a magnetic flux generating coil is provided on the back side of the top plate, the plate itself is not heated, and an eddy current is induced in an iron kettle or the like placed thereon to heat it, or an electromagnetic cooker for heating from the lower surface of the outer cooker to the lower outer peripheral surface. Arrange the magnetic flux generating coil over
An electromagnetic rice cooker (IH type rice cooker) for inducing an eddy current in the inner kettle loosely inserted in the outer kettle to heat the inner kettle is exemplified.

[0003] Explaining the electromagnetic rice cooker, the electromagnetic rice cooker has an outer kettle and an inner kettle loosely inserted into the outer kettle, and a magnetic flux generating coil is arranged from a lower surface of the outer kettle to a lower outer peripheral surface of the outer kettle. The inner pot is formed of a magnetic material such as stainless steel. A plurality of electromagnetic shielding cores are arranged outside the magnetic flux generating coil so as to cross the coil. This core is required to have a high magnetic permeability to guide the magnetic flux generated from the coil in the direction of the inner pot and to suppress leakage to the outside, and a certain degree of insulation to suppress heat generation due to the generation of eddy current. Required. For this reason, the core is formed of sintered ferrite or formed by molding a resin in which soft magnetic powder is oriented and dispersed into a predetermined shape. When the core is formed of sintered ferrite, the core is directly bonded to the coil via an adhesive, or the core is inserted into a resin holder and then the holder is screwed to the lower surface of the outer pot. When the core is formed by orienting and dispersing soft magnetic powder in a resin, the core is directly adhered to the coil via an adhesive or directly screwed to the lower surface of the outer pot.

[0004] In the electromagnetic induction heating apparatus configured as described above, the core is formed regardless of whether the electromagnetic shielding core is formed of sintered ferrite or the soft magnetic powder is oriented and dispersed in resin. Since it has the function of increasing the inductance of the magnetic flux generating coil and the function of shielding the electric field radiated from this coil,
Malfunctions of the electronic devices around the electromagnetic induction heating device due to the electric field can be prevented. Also, when the electromagnetic shielding core is formed by orienting and dispersing soft magnetic powder in resin, since a non-magnetic resin is interposed between countless soft magnetic powders,
The generation of eddy current in the core can be prevented, and as a result, the heat generation of the core can be prevented.

[0005]

However, when the electromagnetic shielding core is formed of sintered ferrite, cracks and chips are liable to occur, and when the core is bonded or afterwards, impact or stress acts to cause cracks and the like. If it occurs, there is a problem that abnormal noise is generated from a cracked portion during operation of the electromagnetic induction heating device or pieces of the core fall off. Further, when the electromagnetic shielding core is formed by orienting and dispersing soft magnetic powder in a resin, the resin is a non-magnetic material, so that there is a problem that it is difficult to increase the magnetic permeability due to the influence of this portion.

[0006] A first object of the present invention is to provide an electromagnetic shielding core which can increase the magnetic permeability without cracking or chipping in the core body and can prevent peeling of the laminated core body. . A second object of the present invention is to provide an electromagnetic shielding core mounting structure that can easily perform an operation of attaching or detaching a core to or from a member to be attached or a resin cover, and can increase the mounting strength of the core. Is to do.

[0007]

The invention according to claim 1 is
As shown in FIGS. 1 and 3, a soft magnetic powder 18a having a surface insulated and coated in a container made of a predetermined non-conductor (19)
Induction heating device 11 formed by filling
And a magnetic shielding core arranged crossing the magnetic flux generating coil 14 of FIG. In the electromagnetic shielding core according to the first aspect, since the eddy current does not occur in the core body 18 when the electromagnetic induction heating device 11 is operated, the core 17 does not generate heat. Further, since the soft magnetic powder 18a has a high magnetic permeability, the magnetic flux generated from the magnetic flux generating coil 14 can be guided toward the heating unit and the leakage to the outside can be suppressed. Further, since the core body 18 itself is a powder and the core body 18 is covered with a container 19 made of a predetermined non-conductor,
Even if an impact is applied to the core 17, the core body 18 does not crack or chip, and the filled soft magnetic powder 18a does not fall off.

FIG. 8 shows the magnetic flux generating coil 14 of the electromagnetic induction heating device 11 formed of the soft magnetic powder 98a.
, A box body 99a formed so as to be able to receive the core body 98 from an opening 99d, and a closing member 9 for closing the opening 99d of the box body 99a.
9b having a non-conductor 99 having a non-conductor 99b.

The invention according to claim 2 is the invention according to claim 1, wherein the soft magnetic powder is formed of iron-based amorphous, cobalt-based amorphous, permalloy, sendust, pure iron or iron-silicon alloy. It is characterized by the following. The invention according to claim 3 is the invention according to any one of claims 1 and 2, wherein the non-conductor according to claim 1 is formed of a resin, rubber, or a liquid crystal polymer. In the electromagnetic shielding core according to the third aspect, it is possible to efficiently guide the magnetic flux generated from the magnetic flux generating coil toward the heating unit and to efficiently suppress leakage to the outside.

A fourth aspect of the present invention is the invention according to the second aspect, wherein the non-conductor according to the second aspect is formed of a resin, silicon oxide, or an oxide film of the powder itself. In the electromagnetic shield core according to the fourth aspect, since no eddy current is generated in the core body, heat generation of the core can be suppressed.

According to a fifth aspect of the present invention, as shown in FIGS. 1 and 2, the electromagnetic shield core 17 according to the first aspect includes the magnetic flux generating coil 14 attached to the body 12 to which the magnetic flux generating coil 14 is attached. This is a mounting structure of an electromagnetic shielding core screwed in a sandwiched state. In the mounting structure of the electromagnetic shielding core according to the fifth aspect, the work of attaching or detaching the core 17 to or from the attached body 12 can be easily performed. The invention according to claim 6 is an electromagnetic shield core mounting structure in which the electromagnetic shield core according to claim 1 is bonded or directly fused to the magnetic flux generating coil via an adhesive. In the mounting structure of the electromagnetic shielding core according to the sixth aspect, the core is bonded or fused to the coil via a non-conductor having good adhesiveness or adhesiveness, so that the mounting strength of the core is increased.

As shown in FIGS. 5, 6, and 7, a pair of locking ribs 52 are provided on both sides of the surface of the resin cover for covering the magnetic flux generating coil 14 opposite to the coil.
8. The electromagnetic shield core 5 according to claim 1, wherein a concave portion or a concave groove 52a having b and 52b is formed.
A pair of engaging portions 59c, 59c capable of engaging with a pair of locking ribs 52b, 52b are formed on both sides of a predetermined non-conductive container 59 which covers the core body 58 of FIG.
This is an electromagnetic shield core mounting structure in which the core 57 is mounted on the resin cover 52 by engaging the c and 59c with the pair of locking ribs 52b. In the mounting structure of the electromagnetic shielding core according to the seventh aspect, the operation of attaching or detaching the core 57 to or from the resin cover 52 can be performed extremely easily.

According to an eighth aspect of the present invention, as shown in FIGS. 1 and 7, the electromagnetic shielding core 17 according to the first aspect is mounted by the mounting structure according to any one of the fifth to seventh aspects. It is a heating device. In the electromagnetic induction heating device according to the seventh aspect, the intensity of the radiated electric field from the magnetic flux generating coil 14 can be reduced by the electromagnetic shield core 17.

[0014]

Next, a first embodiment of the present invention will be described in detail with reference to the drawings. As shown in FIGS. 1 to 4, an electromagnetic rice cooker 11 which is an electromagnetic induction heating device includes an outer cooker 12.
And an inner pot 13 which is loosely inserted into the outer pot 12.
A magnetic flux generating coil 14 is provided from the lower surface to the lower outer peripheral surface. The inner pot 13 is mainly made of a clad material of stainless steel, which is a magnetic substance, and aluminum having high thermal conductivity, and a coating of a fluorine resin or the like (not shown) is provided on the inner side. The coil 14 is attached to the lower surface of the outer hook 12 and the outer peripheral surface of the lower portion of the outer hook 12 by an adhesive. Further, from the lower surface of the coil 14 provided on the lower surface of the outer hook 12 to the outer surface of the coil 14 provided on the outer peripheral surface of the lower portion of the outer hook 12, the coil 14 is formed in a substantially L shape, a rod shape, or a flat plate shape. A plurality of electromagnetic shielding cores 17 are arranged so as to intersect the coil 14 (FIGS. 3 and 4). In this embodiment, eight cores 17 are radiated from the center of the lower surface of the outer kettle 12.
Is arranged.

The magnetic flux generating coil 14 of the electromagnetic rice cooker 11
When an alternating current flows through the coil, an alternating magnetic field is generated around the coil 14, and an eddy current is induced inside the magnetic material of the inner pot 13 by the magnetic field lines of the alternating magnetic field, as indicated by the arrow in FIG.
This eddy current generates Joule heat due to the electric resistance of the magnetic material, and the entire inner pot 13 is heated. The outer hook 12 is made of a non-magnetic material such as polyethylene terephthalate (hereinafter referred to as PET) or the like so that the eddy current is not induced in the outer hook 12. It is covered with the outer plate 16 together with the electromagnetic shielding core 17.

The electromagnetic shielding core 17 includes a core body 18 (FIGS. 1 and 3) formed of a number of soft magnetic powders 18a (FIG. 1), and a predetermined non-conductive container 19 (FIG. 1) covering the core body 18. To FIG. 4).

The soft magnetic powder 18a is made of iron-based amorphous, cobalt-based amorphous permalloy, sendust, pure iron,
It is formed to a particle size of 1 to 500 μm, preferably 10 to 100 μm by an iron-silicon alloy, and polyester, polyvinylidene chloride, polyvinyl chloride, P
A non-conductive coating of 0.1 to 30 μm is formed by an insulating resin such as ET, silicon oxide, or an oxide film of the powder itself. The reason why the particle size of the soft magnetic powder 18a is limited to 5 to 250 μm is that if the particle size is less than 5 μm, it is difficult to manufacture and handle the soft magnetic powder 18a itself, and if the particle size exceeds 250 μm, the loss due to eddy current increases and heat generation occurs. Because there is a problem. The reason for limiting the coating thickness to 0.1 to 30 μm is that if the thickness is less than 0.1 μm, insulation is insufficient and
This is because if it exceeds 0 μm, the magnetic permeability of the core body decreases.

The soft magnetic powder 18a made of an iron-based amorphous material is prepared by melting an alloy of 70 to 90% by weight of iron, 2 to 10% by weight of boron, 5 to 20% by weight of silicon, etc. from a molten state to 1 × 1.
It is formed by quenching at a rate of 0 ⁵ to 1 × 10 ⁶ ° C./sec. The cobalt-based amorphous soft magnetic powder 18a contains 70 to 90% by weight of cobalt and 2 to 1% of boron.
An alloy in which 0% by weight, 5 to 20% by weight of silicon, 5 to 20% by weight of iron, and the like are melted is 1 × 10 ⁵ to 1 × 10 ⁶ from the molten state.
It is formed by quenching at a rate of ° C./sec. Also, the soft magnetic powder 18a made of Permalloy is made of nickel 35-
80% by weight of iron 15-55% by weight, other molybdenum,
The alloy is formed by rapidly cooling an alloy in which niobium, chromium, or the like is dissolved in less than 20% by weight from a molten state. The soft magnetic powder 18a made of Sendust is formed by rapidly cooling an alloy in which 80 to 90% by weight of iron, 5 to 15% by weight of silicon, and less than 10% by weight of aluminum are melted from a molten state. The soft magnetic powder 18a made of pure iron is formed by a so-called atomizing method for rapidly cooling iron from a molten state, a reduction method by reduction from magnetite, a reduction from iron carbonyl complex, or the like. The soft magnetic powder 18a made of an iron-silicon alloy is formed by rapidly cooling an alloy in which 75 to 99% by weight of iron and 1 to 25% by weight of silicon are melted from a molten state.

As shown in detail in FIG. 1, the predetermined conductor container 19 has a substantially L-shaped base portion 19a disposed along the curved inner surface of the core body 18, and the curved outer surface and both side surfaces of the core body 18. And a substantially L-shaped cover portion 19b disposed along both end surfaces. The base portion 19a and the cover portion 19b are formed of resin, rubber, or liquid crystal polymer, respectively. Examples of the resin include resins such as nylon and PET, and examples of the rubber include natural rubber and synthetic rubber.
Acetate type liquid crystal polymers and the like can be mentioned. Cover part 1
9b, the mounting portion 19 is formed integrally with the cover portion 19b.
c (FIGS. 1, 2 and 4), and the mounting portion 19
A through hole 19d is formed in c (FIGS. 1 and 2).

A plurality of bosses 12a project from the lower surface of the outer hook 12 at predetermined intervals on the same circumference (FIGS. 1 to 3), and female screws 12b are formed on these bosses 12a. (FIGS. 1 and 2). Through hole 19 of mounting portion 19c
The screw 21 (FIGS. 1, 2 and 4) is screwed into the screw hole 12b through the through hole 19d in a state where d is aligned with the screw hole 12b of the boss 12a, so that the electromagnetic shielding core 1 is formed.
7 is fixed to the lower surface of the outer shuttle 12 with the magnetic flux generating coil 14 interposed therebetween.

The electromagnetic shielding core may be attached to an electromagnetic cooker, an electromagnetic water heater, an electromagnetic warming device, a high-frequency heater or another electromagnetic induction heating device instead of the electromagnetic rice cooker. In this embodiment, eight electromagnetic shield cores are arranged so as to intersect the magnetic flux generating coils.
Seven or less or nine or more cores may be arranged crossing the coil. Further, an additive such as short glass fiber may be added to a resin such as nylon or PET which is a raw material in order to strengthen the base portion and the cover portion. Also, a through hole is formed in the electromagnetic shielding core through the cover, the core body and the base without projecting the mounting portion on the non-conductive cover, and screws are screwed into the boss through the through hole. The core may be attached to the outer hook by screwing into the hole. Further, instead of screwing the electromagnetic shielding core to the lower surface of the outer hook, the core may be bonded to the lower surface of the magnetic flux generating coil via an adhesive or may be directly fused.

In the electromagnetic shielding core manufactured as described above, since the core body 18 is formed of the soft magnetic powder 18a, no eddy current is generated in the core body 18 when the electromagnetic rice cooker 11 operates. As a result, the core 17 does not generate heat. Further, since the core body 18 itself is a powder and the core body 18 is covered with a container 19 made of a predetermined non-conductor, even if an impact is applied to the core 17, the core body 18 does not crack or chip. Also, the laminated soft magnetic powder 18a does not fall off. Furthermore, the core 17 is screw 2
1 allows the core 17 to be attached to or detached from the outer hook 12 easily.

FIGS. 5 to 7 show a second embodiment of the present invention. 5 to 7, the same reference numerals as those in the first embodiment denote the same parts. In this embodiment, a resin cover 52 covers the outside of the magnetic flux generating coil 14, that is, from the lower surface of the coil 14 disposed on the lower surface of the outer hook 12 to the outer surface of the coil 14 disposed on the outer peripheral surface of the lower portion of the outer hook 12. A flat electromagnetic shield core 57 is attached to the lower surface of the cover 52. A plurality of grooves 52a are formed radially from the center of the lower surface of the resin cover 52, and grooves 52a are formed on both sides of the grooves 52a from within the grooves 52a.
(a) A pair of engaging ribs 52b, 52b having a triangular cross-section and protruding toward each other toward the outside are integrally formed (FIGS. 5 and 6).

The core 57 includes a core body 58 (FIGS. 6 and 7) and a predetermined non-conductive container 59 covering the core body 58.
(FIGS. 5 to 7). The core body 58 is formed of a number of soft magnetic powders 58a (FIG. 6). Non-conductive container 5
9 is a concave groove 52a of the cover 52 on both surfaces of the core body 58.
Base portion 59a disposed along one surface facing
And a cover portion 59b disposed along the other surface, both side surfaces, and both end surfaces of the core body 58 (FIG. 6). The base portion 59a and the cover portion 59b are formed of resin. A pair of engaging portions 59c, 59c are formed on both sides of the core 57, that is, on both sides of the cover portion 59b, and these engaging portions 59c, 59c are formed in a groove shape corresponding to the pair of locking ribs 52b, 52b. (FIGS. 5 and 6).

In the mounting structure of the electromagnetic shielding core configured as above, the pair of engaging portions 59c, 59c of the electromagnetic shielding core 57 are fitted into the pair of locking ribs 52b, 52b of the resin cover 52, respectively. Then, the core 57 is inserted into the concave groove 52a as shown by the solid arrow in FIG. As a result, the pair of engaging portions 59c, 59c is
The core 57 is attached to the resin cover 52, respectively.

In this embodiment, the concave groove is formed in the resin cover. However, a concave portion having a pair of locking ribs on both sides is formed in the resin cover, and the non-conductor of the electromagnetic shielding core is made of rubber. After forming and inserting the pair of engaging portions into the recesses by utilizing the elasticity of the rubber, the pair of engaging portions is restored by the elasticity, and these engaging portions are formed into a pair of resin covers. The core may be attached to the resin cover by engaging with the locking ribs. Further, in this embodiment, the electromagnetic shielding core is attached to the lower surface of the resin cover. However, a concave groove is formed at a portion of the outer hook where the coil is not wound, and a pair of locking grooves are formed on both sides of the concave groove. Ribs may be formed. With this configuration, the electromagnetic shielding core can be directly attached to the lower surface of the magnetic flux generating coil without using a resin cover.

FIG. 8 shows a third embodiment of the present invention.
8 and 9, the same reference numerals as in FIG. 1 denote the same parts. In this embodiment, a core body 98 is formed of a soft magnetic powder 98a whose surface is insulated, and this core body 98 is housed in an opening 99d in a container body 99a to be opened.
Is closed by the closing member 99b. Soft magnetic powder 98a
Is insulated similarly to the first embodiment, and the soft magnetic powder 98a is formed and filled into a substantially L-shape in this embodiment. The box body 99a has a housing recess 99c formed so as to be able to house the core body 98, the opening 99d that can be closed by a closing member 99b, and the mounting portion 9 protruding from the outer surface.
9e. The core 97 is attached to the outer hook 12 at the mounting portion 99e.
A through-hole 99f for mounting with a screw 21 is formed on the lower surface of the. The box body 99a and the closing member 99b, which are the non-conductor 99, are formed of resin, rubber, or liquid crystal polymer. Examples of the resin include thermosetting resins such as phenol, epoxy, polyimide, and urethane, polystyrene, and AB.
Thermoplastic resins such as S, acryl, polycarbonate, polyester, and polyamide are exemplified. Examples of the rubber include natural rubber, synthetic rubber, and liquid crystal polymer. Further, examples of the liquid crystal polymer include copolymerized polyester-based and acetate-based liquid crystal polymers.

[0028]

Next, examples of the present invention will be described in detail together with comparative examples. <Embodiment 1> As shown in FIGS. 3 and 4, an outer hook 12 and an inner hook 13 which is loosely inserted into the outer hook 12 have a magnetic flux generated from a lower surface of the outer hook 12 to a lower outer peripheral surface of the outer hook 12. Coil 14
Was prepared. Also coil 1
Eight electromagnetic shields arranged to cross the coil 14 from the outside of the coil 4, that is, from the lower surface of the coil 14 disposed on the lower surface of the outer hook 12 to the outer surface of the coil 14 disposed on the outer peripheral surface of the lower portion of the outer hook 12. The core 17 was produced by the following method. First, an alloy in which 4% by weight of boron and 8% by weight of silicon were dissolved in 88% by weight of iron was quenched from a molten state to prepare an iron-based amorphous soft magnetic powder.

Next, the soft magnetic powder was impregnated with an acetone solution containing an acrylic resin, filtered, dried and coated on the surface. As shown in FIG. 8, this powder is filled into a housing recess 99c formed in the container body 99a, and the closing member 99b is adhered to the container body so that the core body 98 is formed of the housing recess 99c and the closing member 99b. Was obtained. The eight electromagnetic shield cores 97 were attached to the lower surface of the outer pot 12 of the electromagnetic rice cooker 11 shown in FIGS. Example 1 is an electromagnetic rice cooker 11 to which these electromagnetic shielding cores 97 are attached.

<Example 2> Eight electromagnetic shielding cores 97 obtained by the same method as in Example 1 except that reduced pure iron powder having a particle size of 20 to 150 µm was used in the same manner as in Example 1. 4 was attached to the lower surface of the outer pot 12 of the electromagnetic rice cooker 11 shown in FIG. Example 2 is an electromagnetic rice cooker 11 to which these electromagnetic shielding cores 97 are attached.

<Embodiment 3> Next, as shown in FIGS. 5 to 7, a pair of locking ribs 52b are provided on both sides of the surface of the resin (PET) cover which covers the magnetic flux generating coil 14 on the side opposite to the coil. , 5
An electromagnetic rice cooker 11 having a concave portion or concave groove 52a having 2b was prepared. Next, a container 59 having a pair of engaging portions 59c, 59c capable of engaging with the locking ribs 52b, 52b on both sides of a predetermined stationary body container 59 was formed of PET resin. The soft magnetic powder 18 used in Example 1
a was filled and sealed to obtain eight electromagnetic shielding cores 57. Further, the pair of engaging portions 59c, 59c of the eight electromagnetic shielding cores 57 are connected to a pair of locking ribs 52b, 5c.
2b. Example 3 was an electromagnetic rice cooker 11 to which these electromagnetic shielding cores 57 were attached.

<Comparative Example 1> A sintered ferrite having the same shape as the core body of Example 1 was used as an electromagnetic shielding core. Eight electromagnetic shielding cores were prepared, and these cores were attached to the lower surface of the outer hook with screws via spacers. An electromagnetic rice cooker to which these cores were attached was designated as Comparative Example 1. The spacer was interposed for adjusting the distance from the magnetic flux generating coil of the core. <Comparative Example 2> First, an alloy of 70% by weight of iron, 5% by weight of boron, 5% by weight of silicon, 15% by weight of nickel, and 5% by weight of chromium was rapidly cooled from a molten state to obtain an iron-based amorphous flat powder. Produced. Next, 85% by weight of the iron-based amorphous flat powder and 15% by weight of the nylon resin powder are kneaded, and the kneaded material is formed into the same shape as the core body of Example 1 by injection molding, thereby obtaining eight composites. An electromagnetic shield core made of a material was obtained. These cores were attached to the lower surface of the outer hook with screws together with spacers. An electromagnetic rice cooker to which these cores were attached was used as Comparative Example 2. The spacer was provided for adjusting the distance from the magnetic flux generating coil of the core as in Comparative Example 1. Comparative Example 3 An electromagnetic rice cooker to which no electromagnetic shield core was attached was designated as Comparative Example 3.

<Comparative Test and Evaluation> The inductance of the magnetic flux generating coils of each of the electromagnetic rice cookers of Examples 1 to 3 and Comparative Examples 1 to 3 and the radiated electric field strength during operation were measured. The inductance was measured at a frequency of 25 kHz with an LCR meter directly connected to each magnetic flux generating coil. The radiated electric field strength was measured using a radiated electric field strength meter in an anechoic chamber. At this time, each electromagnetic rice cooker was placed on a wooden table 40 cm in height from the floor, and the antenna of the radiation field intensity meter was placed 3 m from the rice cooker.
It was set apart and at a height of 1 m from the floor. Next, Examples 1 to
3 and each of the electromagnetic rice cookers of Comparative Examples 1 to 3 were packed in cardboard boxes together with styrofoam fasteners.
After falling five times from the height of m, the mechanical strength of the electromagnetic shielding core was measured. Table 1 shows the test results.

[0034]

[Table 1]

As is clear from Table 1, the inductance of each of the magnetic flux generating coils of Examples 1 to 3 and Comparative Example 1 showed substantially the same value, but the inductance of the magnetic flux generating coil of Comparative Example 2 was lower than the above. The inductance of the magnetic flux generating coil of Comparative Example 3 showed a lower value. Further, while the radiated electric field strengths during the operation of each of the electromagnetic rice cookers of Examples 1 to 3 and Comparative Example 1 showed substantially the same value, the radiated electric field strength of Comparative Example 2 showed a higher value than the above. The radiated electric field intensity of No. 3 showed a higher value. This is because in Examples 1 to 3 and Comparative Example 1, the magnetic flux generated from the magnetic flux generating coil was guided toward the heating part by the soft magnetic powder or sintered ferrite having high magnetic permeability, and the leakage to the outside was suppressed. On the other hand, in Comparative Example 2, the magnetic permeability of the core made of the composite material was relatively low, and the induction of the magnetic flux of the magnetic flux generating coil toward the heating portion by this core was insufficient. This is probably because there was no guidance toward the heating section.

In the mechanical strength test of the electromagnetic shielding core, two cracks occurred in the sintered ferrite as the electromagnetic shielding core of Comparative Example 1.
The electromagnetic shielding cores of Nos. 1 to 3 and Comparative Example 2 were not damaged. As a result, it was found that the electromagnetic shielding cores of Examples 1 to 3 and Comparative Example 2 had higher mechanical strength than the electromagnetic shielding core of Comparative Example 1.

[0037]

As described above, according to the present invention, the core body formed of the soft magnetic powder is disposed so as to intersect the magnetic flux generating coil, and the core body is covered with the non-conductor. No eddy current is generated in the core body when the heating device is operated. As a result, the core does not generate heat. Further, since the soft magnetic powder has a high magnetic permeability, it is possible to guide the magnetic flux generated from the magnetic flux generating coil toward the heating portion and to suppress leakage to the outside. Further, since the core body itself is a powder and the core body is covered with a nonconductor, even if an impact is applied to the core, the core body does not crack or chip, and the filled powder does not fall off.

Further, a core body formed by filling the soft magnetic powder is disposed to intersect with the magnetic flux generating coil, and this core body is housed in the box body through an opening, and the opening is closed by a closing member. The same effect as described above can be obtained.

Further, if the core body is attached to the attached body to which the magnetic flux generating coil is attached by screwing with the magnetic flux generating coil interposed therebetween, the work of attaching or detaching the core to or from the attached body can be performed. It can be done easily.

A recess or a groove having a pair of locking ribs is formed on both sides of the surface of the resin cover that covers the magnetic flux generating coil on the opposite side to the coil, and a pair of non-conductors covering the core body is formed on both sides. Forming a pair of engaging portions engageable with the locking rib, and attaching the core to the resin cover by engaging the pair of engaging portions with the pair of locking ribs, the core can be attached to the resin cover. The mounting operation or the removing operation can be performed extremely easily. Further, when the electromagnetic shielding core is attached to the electromagnetic induction heating device, the intensity of the radiated electric field from the magnetic flux generating coil can be reduced by the electromagnetic shielding core.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view taken along the line AA in FIG. 2, showing a structure for attaching an electromagnetic shield core to an electromagnetic rice cooker according to the first embodiment of the present invention.

FIG. 2B shows a state in which the outer pot of the electromagnetic rice cooker is turned down.
FIG.

FIG. 3 is a longitudinal sectional view of an electromagnetic rice cooker to which the core is attached.

FIG. 4C shows a state where a magnetic flux generating coil is removed.
-C sectional view.

FIG. 5 is a perspective view showing a third embodiment of the present invention and corresponding to FIG. 2;

FIG. 6 is a sectional view taken along the line DD of FIG. 5 showing a state where the core is attached.

FIG. 7 is a longitudinal sectional view of an electromagnetic rice cooker to which the core is attached.

FIG. 8 is a sectional view corresponding to FIG. 1, showing a third embodiment of the present invention.

FIG. 9 is a perspective view of the electromagnetic shielding core.

[Explanation of symbols]

 Reference Signs List 11 electromagnetic rice cooker (electromagnetic induction heating device) 12 outer pot (attached body 14 magnetic flux generating coil 17, 57, 97 electromagnetic shielding core 18, 58, 98 core body 18a, 58a, 98a soft magnetic powder 19, 59, 99 Nonconductor 52 Resin cover 52a Groove 52b Locking rib 59c Engaging portion 99a Box body 99b Closing member 99d Opening

Claims (8)

[Claims] 1. Magnetic flux generation of an electromagnetic induction heating device (11) formed by enclosing a soft magnetic powder (18a, 58a, 98a) in a box (19, 59) made of a predetermined non-conductor. An electromagnetic shielding core arranged to cross the coil (14). 2. The soft magnetic powder is formed of iron-based amorphous, cobalt-based amorphous, permalloy, sendust, pure iron, iron-silicon based alloy, and the surface of the powder is coated with a non-conductive material. An electromagnetic shielding core as described. 3. The electromagnetic shield core according to claim 1, wherein the nonconductor is formed of a resin, rubber, or a liquid crystal polymer. 4. The electromagnetic shielding core according to claim 1, wherein the nonconductor is made of resin, silicon oxide, or an oxide film of the powder itself. 5. The electromagnetic shielding core (1) according to claim 1,
7, 57, 97) is attached to the magnetic flux generating coil (14) attached (12)
Mounting structure for an electromagnetic shielding core screwed with the magnetic flux generating coil (14) sandwiched therebetween. 6. A mounting structure for an electromagnetic shielding core, wherein the electromagnetic shielding core according to claim 1 is adhered to a magnetic flux generating coil via an adhesive or directly fused. 7. A resin cover for covering the magnetic flux generating coil (14).
The electromagnetic shield core according to claim 1, wherein a concave portion or a concave groove (52a) having a pair of locking ribs (52b, 52b) is formed on both sides of the surface of the (52) opposite to the coil (14). A pair of engaging portions (59c, 59c) engageable with the pair of locking ribs (52b, 52b) are formed on both sides of (57), and the pair of engaging portions (59c, 59c) are An electromagnetic shield core mounting structure in which the electromagnetic shield core (57) is mounted on the resin cover (52) by engaging with the locking ribs (52b, 52b). 8. The electromagnetic shielding core (1) according to claim 1,
7. An electromagnetic induction heating device mounted with the mounting structure according to any one of claims 4 to 6.