Induction heating container

An induction heating container (1) in which an induction heat generator (3) is attached to the inside of a container main body (2) made of a non-conductive material so as to enable cooking by heating by an electromagnetic cooker. The induction heat generator (3) includes: a laminated body involving a conductor layer (4) that generates heat by induction of eddy current by high-frequency magnetic field and a heat-seal layer (5) that imparts heat-sealing properties to the container main body, and an eddy current control part (6) obtained by cutting the conductor layer (4) along the circumferential direction.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a National Stage of International Application No. PCT/JP2013/005511 filed Sep. 18, 2013, claiming priority based on Japanese Patent Application Nos. 2012-216899 filed Sep. 28, 2012 and 2013-047816 filed Mar. 11, 2013, the contents of all of which are incorporated herein by reference in their entirety.

TECHNICAL FIELD

The present invention relates to an induction heating container provided with an induction heat generator in which heat is generated by joule heat caused by eddy current induced by a high-frequency magnetic field that occurs by an induction heating coil of an electromagnetic cooker or the like.

BACKGROUND ART

In recent years, a heating cooking device generally called as an electromagnetic cooker in which an object to be heated is heated by joule heat caused by eddy current induced by a high-frequency magnetic field that occurs by an induction heating coil provided inside has come to be widely used in common households. As cookware used for heating an object to be heated by inducting heating by means of an electromagnetic cooker, dedicated cookware made of a metal such as iron and enameled iron has conventionally been used.

Under such circumstances, in order to provide a container capable of conducting induction heating by means an electromagnetic cooker at a low cost, the applicant proposed, in Patent Documents 1, 2 or the like, a container for an electromagnetic cooker in which a heat generator made of a conductive material that generates heat by induction heating is attached to the container main body made of a non-conductive material.

RELATED ART DOCUMENTS

Patent Documents

SUMMARY OF THE INVENTION

Problems to be Solved by the Invention

As for these induction heating containers proposed by the applicant, by combining a container main body molded by using a general-purpose resin material and an induction heat generator formed by using an inexpensive conductive material such as aluminum foil, in order to enable the containers to be disposed and to be provided at an inexpensive cost, the following problems are intended to be solved.

That is, when a container main body is molded by using a general-purpose resin material, if an induction heat generator is heated excessively, the container main body may be damaged such as deformation, burning or the like. To solve this problem, in Patent Document 1, an induction heat generator is separated in the radial direction, the edge parts of the separated parts are abutted or superimposed to form a fuse function part. In the case of overheating, i.e. in the case where an inducting heat generator is heated excessively (for example, in the case of empty boiling), the fuse function part is caused to be broken selectively, whereby the container is prevented from being damaged by avoiding overheating.

Such containers may encounter the following problem. Due to uneven heating or the like, a liquid object to be heated (e.g. water) in the container is suddenly heated locally, thereby causing bumping. As a result, the object to be heated is scattered to cause a user to get burned or to cause the surrounding area of an electromagnetic cooker to be contaminated. In contrast, in Patent Document 2, an induction heat generator is partially fixed to the inner bottom surface of a container main body, whereby linear adhesion parts extending in the circumferential direction of the heat generator are intermittently formed such that they are spaced from each other in the radial direction, whereby bumping that occurs at the time of heating a liquid object to be heated is suppressed.

However, as a result of further intensive studies made by the inventors of the present invention, they have found that, in these conventional technologies, there are still problems to be solved for the prevention of bumping, in particular.

The present invention has been made in view of the above-mentioned circumstances, and is aimed at providing an induction heating container that can be used as an induction heating container in which an induction heat generator is attached to a container main body made of a non-conductive material and a liquid object to be heated accommodated therein is heated by an electromagnetic cocker or the like, and in such use, bumping at the time of heating a liquid object to be heated can be effectively prevented.

Means for Solving the Problems

The induction heating container of the present invention has a configuration in which an induction heat generator is attached to the inside of a container main body that is made of a non-conductive material so as to enable cooking by heating by an electromagnetic cooker, wherein

the induction heat generator comprises:

a laminated body involving a conductor layer that generates heat by induction of eddy current by high-frequency magnetic field and a heat-seal layer that exhibits heat-sealing properties to the container main body, and

an eddy current control part that is obtained by cutting the conductor layer along the circumferential direction.

Advantageous Effects of the Invention

The induction heating container of the present invention can be safely used as an induction heating container with which bumping of a liquid object to be heated accommodated therein is effectively suppressed, whereby burning of a user or contamination of the surrounding area of an electromagnetic cooker can be prevented.

MODE FOR CARRYING OUT THE INVENTION

Hereinbelow, preferred embodiments of the present invention will be explained with reference to the drawings:

First Embodiment

First, the first embodiment of the induction heating container of the present invention will be explained.

FIG. 1is a plan view showing the outline of the induction heating container according to this embodiment, andFIG. 2is a schematic end elevation taken along the line A-A inFIG. 1.

The induction heating container1shown inFIGS. 1 and 2is provided with a container main body2formed of a non-conductive material and an induction heat generator3attached to the inside of the container main body.

The induction heat generator3is formed of a laminated body that includes a conductor layer4that generates heat when eddy current is induced by high-frequency magnetic field and a heat-seal layer5that has heat-sealing properties for the container main body2.

The induction heating container1is generally used on a commercially available electromagnetic cocker. Therefore, it is preferred that the sizes of the container main body2and the induction heat generator3be set according to the size of the heating coil provided in the electromagnetic cocker used. For example, a general heating coil provided in a commercially available household electromagnetic cocker has an inner diameter of about 5 cm and an outer diameter of about 20 cm. In the case of an electromagnetic cocker for business use, a larger heating coil may be used. The size thereof is appropriately set according to the electromagnetic cocker that is supposed to be used.

The container main body2is formed of a non-conductive material. A synthetic resin material such as a polystyrene-based resin such as polystyrene, a polyester-based resin such as polyethylene terephthalate, a polyolefin-based resin such as polypropylene, a polyamide-based resin or the like can preferably be used. The container main body2may be of a single layer structure or a multilayer structure obtained by combining these resins with one another or by combining these resins with other functional resins. Although paper, glass or the like can also be used as the non-conductive material, taking into consideration heat sealing with the heat-seal layer5in the induction heat generator3, it is preferred that the inner surface thereof be coated with the above-mentioned synthetic resin.

The shape of the container main body2is not limited to that shown in the figure. Various shapes can be selected such that the shape in the planer view is square, rectangular oblong, circle, elliptical or the like. In the shown example, in the planer view, the shape of the container main body2is almost square, and a step is provided in the vicinity of an opening at the upper end such that a tray9on which foodstuff is mounted can be supported or fitted. Although not particularly shown, a configuration is possible in which, on the tray9that is supported by or fitted to the container main body2, another induction heating container1is stacked.

The induction heat generator3has an almost circular flat plate form, and is attached to a bottom surface20of the container main body2in an almost circular flat plate form. As for the shape of the induction heat generator3to be attached to the container main body2, a circle is most effective in respect of properties of eddy current induced. However, according to the shape of the container, it may be square or elliptical. Not particularly shown, a rising part may be provided along the side wall of the container main body2.

As for the conductive material forming the conductor layer4of the induction heat generator3, various conductive materials that generate heat by induction heating caused by high-frequency magnetic field such as a metal including aluminum, nickel, gold, silver, copper, platinum, iron, cobalt, tin and zinc, or alloys thereof can be used. More specifically, when aluminum is used as a conductive material, for example, the conductor layer4can be formed by using aluminum foil having a thickness of about 0.10 to 100 μm, more preferably 1 to 40 μm.

If metal foil such as aluminum foil is used, when the induction heat generator3is attached to the container main body2, it becomes easy to adapt the induction heat generator3to the shape of the container main body2by subjecting the induction heat generator3to three-dimensional processing, e.g. folding along a bottom surface21or the side wall of the container main body2, or the like.

The heat-seal layer5of the induction heat generator3is not particularly restricted as long as it has heat-sealing properties for the container main body2. The heat-seal layer5can be appropriately selected according to a non-conductive material forming the container main body2. A synthetic resin material similar to the synthetic resin material used for the container main body2can be used. As one example, it is preferable to use polypropylene that is easy to be processed by molding, has good heat-sealing properties and an adequate heat resistance.

The conductor layer4and the heat-seal layer5can be laminated directly or through an adequate adhesive by a known laminating technology. By configuring the induction heat generator3as a laminated body, since conventionally known technologies for producing a multilayer film or a multilayer sheet can be applied, the production of the induction heat generator3and the induction heating container1that is provided with the induction heat generator3is facilitated.

In such induction heat generator3, a fuse function part7that is broken selectively under specific circumstances (such as empty boiling) is provided. Two fuse function parts7are radially provided on an extension of the center line that passes a shape center8of the induction heat generator3with a prescribed distance being provided from the shape center8.

As for the fuse function part7, a technology disclosed in Patent Document 1 or JP-A-2010-044929 can be used, for example. Specifically, the induction heat generator3is separated in the radial direction, and edges of the thus separated generator are abutted to each other or superimposed one on another to allow the conductor layers4are brought into contact and re-bonded.FIG. 3, which is a schematic end elevation view taken along line B-B inFIG. 1, shows one example of such fuse function part7. In this example, the edge part sides of the separated conductor layer4rises, and the edges thereof are aligned, superimposed one on another, and bonded. In order to ensure bonding of one conductor layer4with another conductor layer4, the heat-seal layer5in the corresponding part is peeled off. In the fuse function part7, in addition to the configuration mentioned above, known technologies can be used; for example, a technology disclosed in JP-H07-296963 in which a narrow part in which the width in the radial direction becomes locally shortest is provided from the center to the outer periphery of the heat generator, whereby eddy current is concentrated in the narrow part to allow the temperature of the narrow part to be higher than that of other parts, a technology disclosed in JP-A-2007-330391 in which the radial direction of a heat generator is subjected to mountain folding processing in the radial direction to form a projection, and the projection is exposed from the liquid surface before other parts are exposed.

In the induction heat generator3, an eddy current control part6that is formed by cutting the conductor layer4along the circumferential direction is provided. A plurality of eddy current control parts6are provided such that they avoid the fuse function part7and that they are spaced from each other in the radial direction. Specifically, in a configuration in which the double concentric circle around the shape center8is intermitted only on a part that intersects the fuse function part7, the eddy current control parts6are provided by four cutting lines13in total in a region slightly nearer to the outer periphery of the induction heat generator3(a main heating area10, mentioned later).

The edges of the cutting lines13that form the eddy current control part6serve as a starting point where bubbles are generated when an object to be heated such as water is boiled. Accordingly, at the time of boiling, a large amount of small bubbles is continuously generated as in the case where a boiling bubble stone is put, whereby an effect is exhibited that abrupt generation of large bubbles is prevented. At the same time, the eddy current control part6controls the eddy current induced in the conductor layer4, and enables uniform heating, whereby occurrence of bumping is suppressed.

Eddy current is strongly induced in accordance with the shape of a heating coil provided in an electromagnetic cooker on which the induction heating container1is mounted. The current density distribution thereof is not uniform in the radial direction, and has a current density peak at a position slightly closer to the outer periphery than the center of the radial direction, and as a result, a corresponding position of the conductor layer4is strongly heated. The cutting line13that forms the eddy current control part6is, as shown in the schematic end elevation inFIG. 4(a), obtained by cutting the conductor layer4of the laminated bodies forming the induction heat generator3. No current is flown in a direction crossing the cutting line13. By forming the cutting line13that extends in the circumferential direction in order to prevent eddy current from being concentrated in a part closer to the outside, eddy current can be aligned to attain uniform heating.

It is desired that a plurality of the eddy current control part6which is formed by the cutting line13be provided. For the reasons mentioned above, it is preferred that the eddy current control parts6be provided densely in a part closer to the outer periphery as compared with a case where they are arranged uniformly in the radial direction. However, no eddy current control part6is provided in the fuse function part7in order not to impede its function of being selectively broken down at the time of overheating.

The shape of the cutting line13that constitutes the eddy current control part6is not limited to a circle or an arc around the shape center8of the induction heat generator3. It can be appropriately altered taking into account factors that affect the state of eddy current induced, such as the shape of a heating coil of an electromagnetic cooker that is supposed to be used or the entire shape of the induction heat generator3.

In the shown configuration, the induction heat generator3is separated into the main heating region10on the center side and the peripheral region11on the outer periphery side by a first radial direction cutting line13athat cuts the conductor layer4circularly (seeFIG. 2). As mentioned above, since eddy current does not flow in the direction crossing the cutting line13, eddy current is formed independently for each region separated. In the main heating region10, strong eddy current is induced around the shape center8of the induction heat generator3(mounted on the center of the heating coil), therefore the main heating area10is heated most efficiently. All of the plural eddy current control parts6and the fuse function part7are provided in the main heating area10.

If the first radial direction cutting line13ais not provided, the entire induction heat generator3can be regarded as the main heating area

The peripheral area11is separated into plural small areas by a circumferential cutting line13cthat extends in the radial direction. By separating in the circumferential direction, strong eddy current around the shape center8is not induced. Accordingly, the temperature of the conductor layer4in the peripheral area11is not raised too much. Therefore, by attaching the induction heat generator3to the container main body2by heat sealing with the container main body4by the heat-seal layer5in the peripheral area11, even when the temperature of the main heating area10of the induction heat generator3rises, heat transmission to the conductor main body2can be suppressed, whereby deformation or burning of the container main body2can be prevented.

Similarly, in the inner peripheral side of the main heating area10including the shape center8, a central adjustment area12is formed by a second radial direction cutting line13bthat cuts the conductor layer4circularly (seeFIG. 2). The central adjustment area12is separated into plural areas in the circumferential direction by a circumferential direction cutting line13c. Due to such a configuration, as in the case of the peripheral area11, strong eddy current is not formed in the central adjustment area12.

Eddy current induced in the region including the shape center8is not so strong. However, the current density distribution thereof is slightly unstable and may disturb eddy current that flows in the outer side, and hence, it is preferable to separate the conductor layer4in this area from the main heating area.

As shown inFIG. 4(a), as in the case of the cutting line13that forms the eddy current control part6, all of the first radial direction cutting line13a, the second radial direction cutting line13band the circumferential direction cutting line13care obtained by cutting the conductor layer4of the laminated body that forms the induction heat generator3. By allowing the heat-seal layer5to be in the connected state, without cutting, the induction heat generator3can be handled as an integrated body, leading to significant easiness at the time of production.

When forming these cutting lines, half-cutting is conducted by a knife from the side of the conductor layer4, or selective cutting of the conductor layer4is conducted by means of a YAG laser, a semiconductor layer or the like. Within a range that no adverse effects are imposed on handling of the induction heat generator3as an integrated body, a part of the heat seal layer5may be cut (seeFIG. 4(b)). Further, on the surface of the conductor layer4, a protective layer15that is formed of the same resin material as that of the heat-seal layer5may be provided (seeFIG. 4(c)).

In the shown configuration, the induction heat generator3is attached in such a manner that the heat-seal layer5in the peripheral region11is heat-sealed to a heat seal site21of the bottom surface20of the container main body2. On the inner peripheral side of the heat-seal site21on the bottom surface20of the container main body2, a through hole22is provided, the induction heat generator3is exposed, and the through hole22is sealed by the induction heat generator3.

The bottom surface20of the container main body2may be deformed by bending during cooking with heat, and may be mounted on an electromagnetic cooker in an unstable manner. In this embodiment, by removing the bottom surface from a position right below the main heating area10of the induction heat generator3, of which the temperature becomes highest, the container is prevented from being deformed by bending. In addition, since a grounding part23surrounding the through hole22has a higher rigidity than that of the induction heat generator3, even if the induction heat generator3that is exposed from the through hole22is bent, it can keep a stable posture.

The container main body2is not limited to the shown example. It may be of a common configuration in which the bottom surface20is closed, that is a general form. Attachment of the induction heat generator3in that case, the technology disclosed in Patent Document 2 can also be used. Further, similar effects can be obtained by providing a through hole in the middle of the induction heat generator3instead of the central adjusting region12. In addition, a convection hole that accelerates the convection of an object to be heated may appropriately be formed by penetration.

The induction heating container1having such a configuration is able to accommodate a liquid object to be heated (water, soup, or the like) and is able to heat the object to be heated by mounting on an electromagnetic cooker. Under specific circumstances where heating starts without accommodating an object to be heated or the container is left until a liquid object to be heated is evaporated, or the like, the fuse function part7is broken, and the break-down of the fuse part7is detected by a safety device of the electromagnetic cocker, then the heating is terminated. As a result, damage on the container can be prevented. When the electromagnetic induction heating container1is used for steam cocking as a disposable container, or the like, the fuse function part7can be used like a cooking timer.

Further, according to the induction heating container1of the present invention, the edges of the cutting lines13that constitute the eddy current control part6(that is, the cutting surface (edge exposed part) in which the conductor layer4is cut in the thickness direction and exposed) (seeFIGS. 4(a) and 4(b)) serve as a starting point at which an object to be heated such as water boils to allow bubbles to be generated, and a large amount of small bubbles is continuously formed, thus preventing sudden formation of large bubbles. In addition, due to the presence of the eddy current control part6, disturbance or deviation of eddy current is prevented, whereby uniform heating becomes possible, leading to effective suppression of bumping.

Accordingly, a circumstance where an object to be heated that has been scattered causes a user to get burned and causes the surrounding area of the electromagnetic cooker to be contaminated can be avoided. Further, since the eddy current control part6is provided such that it avoids the fuse function part7, it can be used safely without hindering operation of the fuse function part7.

Second Embodiment

Next, an explanation will be made on the second embodiment of the induction heating container of the present invention.

FIG. 5is a plan view showing the outline of the induction heating container of this embodiment andFIG. 6is an end elevation taken along line C-C inFIG. 5.

The induction heating container1shown inFIG. 5andFIG. 6is provided with the container main body2formed of a non-conductive material and the induction heat generator3that is attached to the closed bottom surface20of this container main body2.

The bottom surface20of the container main body2is almost square. The container main body2is configured such that it can accommodate a liquid object to be heated such as water by allowing a side wall part to rise such that it surrounds this bottom surface20. The shape of the bottom surface20is not limited to that shown in the figures. For example, the shape of the bottom surface20may be rectangular or circular. In addition, the shape may be a polygon such as a triangle, a pentagon and a hexagon. As for the overall shape of the container main body2, it may have various shapes taking easiness in handling or the like into account. As in the first embodiment mentioned above, the dimensions of the container main body2and the induction heat generator3are set adequately.

This embodiment differs from the above-mentioned first embodiment in that the container main body2of which the bottom surface20is closed is used, and the induction heat generator3is attached to the bottom surface20of the container main body2and the features changed in accordance therewith. Other features are the same as those in the above-mentioned first embodiment, and hence a duplicated explanation is omitted.

In attaching the induction heat generator3to the bottom surface20of the container main body2, it is preferred that the induction heat generator3be attached such that it is spaced from the bottom surface20of the container main body2. By attaching the induction heat generator3such that it is spaced from the bottom surface20of the container main body2, a liquid object to be heated such as water accommodated within the container main body2spreads to a gap between the induction heat generator3and the bottom surface20of the container main body2. As a result, the efficiency of heating an object to be heated can be enhanced, and at the same time, damage of the container main body2by heat from the induction heat generator3can be effectively avoided. At this time, in order to prevent the container main body2from being damaged, a through hole3athat is cut in an arbitrary shape such as circular or elliptical or a slit-like cut is provided in the middle or its vicinity of the induction heat generator3so that convection is accelerated to prevent an object to be heated from stagnating in the backside of the induction heat generator3.

In order to attach the induction heat generator3such that it is spaced from the bottom surface20of the container main body2, the induction heat generator3may be heat-sealed to a supporting part24that projects from the bottom surface20of the container main body2, for example.

As mentioned above, if the conductor layer4is separated into small regions, strong eddy current is not induced in these regions, and hence the temperature of these regions does not rise greatly. Therefore, in the first embodiment mentioned above, the conductor layer4is separated into the main heating region10and the peripheral region11(on the outer peripheral side) by the first radial direction cutting line13a, the peripheral area11is separated into plural small areas by the circumferential direction cutting line13c, and these regions are heat-sealed to the container main body2in the heat-seal layer5in the peripheral area11. For the same reasons, it is preferred that heat sealing to the supporting part24be conducted in the heat seal-layer5in the peripheral area11. In this embodiment, based on the similar concept, the induction heat generator3is heat-sealed to the supporting part24in the heat-seal layer5of the central adjustment region12. Further, it is preferred that, also in the main heating region10of the induction heat generator3, small areas separated from the main heating area10be formed by surrounding a specific range of the conductor layer4by a cutting line13dand that heat sealing to the supporting part24be conducted by the heat-seal layer5in these small areas. As a result, heat transmission from the induction heat generator3to the container main body2is suppressed, whereby deformation or burning of the container main body2can be prevented.

When the induction heat generator3is heat-sealed to the supporting part24by the heat-seal layer5in the main heating area10thereof, if cutting lines13ethat are in the form of line segments extending in the radial direction are formed as shown inFIG. 7, it can be assumed that eddy current flows while avoiding such cutting line13e. Therefore, as shown inFIG. 7, it can be configured such that the induction heat generator3be heat-sealed to the support part24in the heat-seal layer5at a part that overlaps the cutting line13e.

By attaching the induction heat generator3to the container main body2also in the central adjustment area12or the main heating area10, floating or waving of the induction heat generator3due to convection or flow of an object to be heated or repulsion with the heating coil can be suppressed, whereby more stable heating becomes possible.

When cutting lines are formed in the main heating area10, the shape or the dimension thereof is taken into consideration so that eddy current that is induced in the main heating area is not greatly disturbed.

The present invention is explained hereinabove with reference to preferable embodiments. The present invention is not limited to the above-mentioned embodiments, and it is needless to say various modifications are possible within the scope of the present invention.

For example, in the above-mentioned embodiments, the cutting lines13,13a,13b,13c,13dand13eare indicated as those obtained by separating completely the conductor layer4in the thickness direction. However, these cutting lines may be in the state where the conductor layer4is connected thereto with a part in the thickness direction being remained. As long as an edge exposed part obtained by cutting the conductor layer4in the thickness direction is formed, and this edge exposed part serves as a starting point where bubbles are generated when an object to be heated such as water boils, whereby occurrence of bumping is suppressed by preventing abrupt generation of large bubbles, the conductor layer4is not necessarily broken completely in the edge exposed part.

INDUSTRIAL APPLICABILITY

The induction heating container according to the present invention can be used as a container that is able to heat an object to be heated by a commercially available an electromagnetic cooker.

DESCRIPTION OF REFERENTIAL NUMERALS