WO2014170166A1 - Induction heating device having an induction coil, method for producing an induction heating device and induction cooking appliance - Google Patents

Abstract

An induction heating device having an induction coil, in particular for an induction stovetop, has a supply of phase change material such as paraffin in a container, said induction coil being embedded in the phase change material. This phase change material absorbs the heat given off by the induction coil during operation in order to cool it and melts in the process so that the heat is stored therein. After operation of the induction coil, the stored heat can slowly be dissipated to the surroundings by controlled recrystallization of the phase change material and significantly slower heat dissipation.

Description

 description

Induction heating device with an induction coil, method for producing an induction heating device and induction cooking device

Field of application and prior art The invention relates to an induction heating device with at least one induction coil and to a method for producing such an induction heating device. In addition, it relates to an induction cooking appliance with such an induction heater.

Induction heaters with at least one induction coil, such as those used for induction cooktops as induction cooking appliances, are becoming increasingly popular. A considerable technological challenge is the cooling, both of a power electronics for supplying the induction coil and the induction coil itself. Due to the ohmic losses in a copper strand from the induction coils are often wound, heat losses and in addition also in ferrite rods to influence the generated magnetic field. These heat losses are in themselves a problem and also reduce the efficiency of the induction heater. As a result, among other things, an underlying electronics under and / or next to the induction coil of a device with the induction heating device is affected. Furthermore, the currently used materials for an insulating coating of the copper strands temperatures of up to 200 ° C must be maintained as strand core temperature. Higher temperatures can only be achieved with other paints and at significantly higher costs. Particularly critical are local warming, where the heat generated can be dissipated poorly. Furthermore, the ferrite cores have a Curie temperature of about 200 ° C, which is why they must not be warmer. Finally, the power loss at the induction coils increases with increasing temperature. It is known from DE 19935835 A1 to use a fan in an induction hob in order to cool both power electronics for an induction heater and, if appropriate, the induction coil of the induction heater during operation. However, a fan used for this purpose consumes even electrical energy, in addition, fan noise from an operator are often perceived as disturbing.

Task and solution The invention has for its object to provide an induction heating device mentioned above with at least one induction coil, an induction cooking appliance with such an induction heating and a method for producing such an induction heating, with which problems of the prior art can be avoided and in particular advantageous and on Reliable way to excessive heating of an induction coil is avoided.

This object is achieved by an induction heating device with the features of claim 1, an induction cooking appliance with the features of claim 8 and a method for producing such an induction heating device with the features of claim 9. Advantageous and preferred embodiments of the invention are the subject of further claims explained in more detail below. In this case, some of the features are described only for the induction heater, only for the induction cooking appliance or only for the method for producing an induction heater. However, they should be able to apply independently to the induction heating device, the induction cooking device and the method independently. The wording of the claims is incorporated herein by express reference.

It is provided that the induction heater has at least one induction coil. Such an induction heater can just as will be explained in more detail below, be used in an induction cooker. According to the invention, the induction heater has a supply of so-called Phasenwechselmatenal or a container with phase change material therein. The induction coil is thermally conductively connected to the phase change material or a reservoir or container with phase change material therein and is thus cooled, wherein it at least partially, advantageously embedded at least with a lower region, directly in the phase change material or directly surrounded by this. Preferably, it is completely embedded or surrounded, particularly preferably also the aforementioned ferrite components, for the best possible heat conduction or cooling of the entire induction coil or induction heating device.

Such phase change material is known, inter alia, as the term "phase change material." Its latent heat of fusion, solution heat or heat of absorption is significantly greater than the heat which it can store due to its normal specific heat capacity (without the phase change effect) Latent heat storage referred to and are for example in heat bags or cooling batteries in use, as well as with paraffin or the like filled memory element in Tanks of solar thermal systems. A latent heat storage works by exploiting the enthalpy of thermodynamic state changes of a storage medium, namely just said phase change material. According to the invention, the phase transition is solid-liquid and vice versa, so used as solidification and melting. The effect is a significantly improved heat absorption during the phase transition from solid to liquid, which takes place at a melting temperature which can be adjusted by choice of material in the range between about 45 ° C and 80 ° C, advantageously between about 60 ° C and 70 ° C. The phase change material can absorb a lot of heat very quickly and becomes liquid. By a subsequent solidification of the phase change material, the rapidly absorbed heat can be released back to the environment, which can be done much slower and thus more easily with a given predetermined heat dissipation. This will also be discussed below.

Advantageously used materials may be selected from the following group: paraffin, hard paraffin, plastic, salt, salt hydrate, alum, Glauber's salt, carboxylic acid amides, carboxylic acid esters, dipotassium hydrogenphosphate hexahydrate, sodium acetate trihydrate, thermoplastics and / or sugars. Because of the above-mentioned range melting temperature in the range between about 45 ° C and 80 ° C is especially suitable for paraffin or hard paraffin.

Since the phase change material becomes liquid when it has absorbed much heat, it must be placed in a reservoir or container. This can also have other functions such as a support function or recording function.

In an advantageous embodiment of the invention, the container for the phase change material consists at least partially of poorly heat-conducting material or is thermally insulated. For this purpose, for example, offers a sufficiently temperature-resistant plastic. A thermal insulation can consist of conventional insulating materials. A heat conduction should preferably be reduced at a side pointing downwards or pointing towards an electronics of the induction cooking appliance or into the appliance. This avoids excessive increase of the internal temperature of the device. An exception is a connection to a cooling device inside the device, for example a cooling air duct with a fan or a heat sink.

Up to such a container may have a flexible cover. This makes it possible to press it against a given cover. In particular, in the case of an induction hob with a hob plate, which is often made of glass bottomed ceramic, this is an advantage. Then, if the Phasenwechselmatenal extends to this flexible cover or to the top of a container, a good thermal connection to this hob plate done. Even if it is not particularly suitable for heat absorption due to its special material as hard glass or glass ceramic, a certain amount of heat flows away. This can also last for a longer period of time, which is not bad for a cooktop panel, since it should be used only limited as a support or storage anyway.

An induction coil is advantageously substantially flat or flat, for example, with a height of 0.1 cm to a maximum of 3cm and a diameter of 10cm to 40cm. At least toward a flat side, the induction coil can be connected in a heat-conducting manner to the phase change material or can be cooled by the phase change material. Thus, a fairly good and large heat transfer surface is given, which in particular includes each region of the longitudinal extension of the coil winding to avoid the aforementioned local overheating. Advantageously, the induction coil has ferrite components on a lower side, in particular ferrite rods or ferrite cores, in order to initiate the magnetic field generated by the induction coil as well as possible, for example, in a cooking vessel placed above the induction heater for heating. Such ferrite rods are often elongated, flat and wide. They are arranged relatively close to the induction coil or below. These ferrite components are heated during operation, which should be avoided for various reasons, in particular their strong temperature-dependent properties as well as a lying in the range of slightly above 200 ° C Curie temperature. Such ferrite components are advantageously also thermally conductive connected with Phasenwechselmatenal, particularly advantageous embedded therein. Preferably, they are embedded together with the induction coil in the same container with Phasenwechselmatenal.

An induction coil may have multiple layers or windings. On the one hand, for this purpose, an aforementioned coil wire consisting of a plurality of thin strands can be used with a coating of insulating varnish, as is known in the art. On the other hand, a solid conductor can be used which advantageously has the shape or cross section of a band. Such a conductor is particularly advantageously edged upright in the form of a ribbon, wherein, when the induction coil is wound, distances are provided between the individual windings or to the respectively adjacent band. At these intervals or between adjacent windings Phasenwechselmatenal is present. According to one possibility, the phase change material in the liquid state after the winding of the induction coil and introduction into an aforementioned container can be poured over it for embedding. According to an alternative possibility, the phase change material can be applied to a conductor in a certain thickness prior to winding of the induction coil, so that the coil shape, including distances between the windings, can be determined at least by the thickness of the applied phase change material. In this case, the phase change material is solidified at least during winding of the induction coil and should be plastically deformable for it. For this purpose, especially at the beginning called paraffin. In this case, the phase change material can also be applied to the conductor with different thickness in order to achieve adjustable or varying spacings of the windings and thus a largely arbitrarily adjustable winding density.

In a further embodiment of the invention, the phase change material may have additives which improve the heat conduction and are particularly advantageous for good thermal conductivity and / or metallic. For this purpose, magnesium oxide is suitable, in particular in powder form, under certain circumstances also metal powder or metal particles or metal filaments, for example aluminum or copper.

In a further development of the invention, the induction heating device has a plurality of induction coils, wherein a separate supply or container with phase change material is provided for each induction coil. In this case, the containers should be separated from each other at least by largely continuous partitions, in particular be formed completely separately. They can still be thermally conductively connected by thermal bridges.

Advantageously, the phase change material of an induction coil with phase change material of another induction coil is thermally conductively connected. This can be done through continuous areas or channels that are filled with phase change material. Alternatively, this can be done via the aforementioned separate thermal bridges to the containers, advantageously made of good heat conducting material, such as aluminum. Even so, the possibly still cool phase change material of an induction coil can absorb heat from a heavily heated, other induction coil.

An induction cooking appliance, in particular an induction hob, advantageously has at least two induction coils, and particularly advantageously at least four induction coils. Each of the induction coils may have an initially mentioned container or stock with phase change material according to the invention, in order to remove dissipated power dissipation at the induction coil. After operation of an induction coil, the heat of the power loss is in the phase senwechselmaterial stored, this liquid. For re-operation, this heat must be released again, which is done by recrystallization. For this purpose, a trigger or corresponding actuator may be provided on or in a container with phase change material, for example a snap spring actuator triggered via a piezoelectric element or a bimetal in the manner of a cracking frog or the like. After its release, the phase change material recrystallizes or solidifies very rapidly or solidifies abruptly and releases the stored heat in a relatively short time. This can then be delayed, possibly delayed by the use of insulating material, in part upwards to a hob plate or a cooking vessel standing thereon. However, since this process can take much longer than the operation of the induction coil, for example 1 hour to 6 hours compared to a few minutes to 1 hour of operation of the induction coil, said material properties can be exploited and there are no dangerously high temperatures on the hob plate. The temperatures on a cooktop panel can be maintained in the range of 50 ° C to 70 ° C. In a further embodiment of the invention, it is also possible that an induction hob not only has four induction coils with precisely defined size or delimitation against each other, but a significantly higher number, as is known for example from EP 1463383 A1. Although these many induction coils may be embedded individually, advantageously all together or in each case several together in a container with phase change material embedded therein.

These and other features will become apparent from the claims but also from the description and drawings, wherein the individual features each alone or more in the form of sub-combinations in an embodiment of the invention and in other fields be realized and advantageous and protectable Represent embodiments for which protection is claimed here. The subdivision of the application into subheadings and individual sections does not limit the general validity of the statements made thereunder.

Brief description of the drawings

Embodiments of the invention are shown schematically in the drawings and will be explained in more detail below. In the drawings show:

1 is a schematic sectional view through an inventive induction hob with induction coils, which are embedded in phase change material, 2 shows an enlargement of an induction coil according to FIG. 1,

3 shows a modified induction hob with a plurality of induction coils embedded in a single container of phase change material therein.

Fig. 4 is a schematic section of a manufacturing process of an induction coil during winding with applied layer of phase change material and

Fig. 5 is a wound up according to the method of Fig. 4 induction coil in plan view with a continuous spacer layer of phase change material between adjacent windings.

DETAILED DESCRIPTION OF THE EXEMPLARY EMBODIMENTS In FIG. 1, an induction hob 1 1 is shown schematically in section with a hob plate 12 and a housing 14 facing downwards. The induction hob 1 1 has two induction heaters 16 a and 16 b, which essentially have an induction coil 18 a and 18 b. The induction coils 18a and 18b consist of a plurality of windings of a conductor 19a and 19b, respectively, as known from the prior art. Below the induction coils 18a and 18b are also known from the prior art ferrite rods 20a and 20b are provided, namely at substantially circular trained induction coils 18 in the radial extent.

The induction coils 18a and 18b together with ferrite rods 20a and 20b are arranged in coil containers 22a and 22b, respectively, which are substantially completely filled with a phase change material 25 of the aforementioned type, preferably with paraffin, for example with a melting point of about 60 ° C to 64 ° C. This means that the induction coils 18a and 18b and ferrite rods 20a and 20b are completely embedded in the phase change material 25.

Furthermore, an optional thermal bridge 27 is shown in dashed lines between the coil containers 22a and 22b. It can serve for compensatory heat exchange, as previously described. It advantageously consists of a good heat-conducting material, in particular aluminum. This thermal bridge 27 can also fulfill other functions, for example a stabilizing or carrier function in the induction hob 11. Furthermore In addition, they can odgl a known per se heat sink for circuit breakers. a power supply for the induction coils 18a and 18b.

Another option for the induction hob 1 1 is arranged in the bottom of the housing 14 fan 28. It can either be provided anyway, for example, for cooling the aforementioned circuit breaker. Under certain circumstances, it can also be used for cooling the induction coils 18a and 18b either during operation or, advantageously, after their operation, in particular for heat dissipation of the heat stored in the phase change material 25 for a better and faster delivery to the environment for re-operation of the induction coils 18a and 18b. The magnification of an induction heater 16a of Fig. 2 shows how a coil container 22a has container walls 23 ^' and a container bottom 23 ^" , which may be made of plastic, as explained above Thus, the induction heater 16a is directly applied to the underside of the cooktop panel 12. On the container bottom 23 ^" , a thermal insulation 30 is provided as a layer, for example of conventional thermal insulation material used in cooking appliances, preferably glass or rock wool or vermiculite or the like ..

The phase change material or paraffin 25 is located in the coil container 22a. Not shown are the possible additives mentioned above for a better internal heat conduction, for example magnesium oxide in powder form. To the left and right of the induction coil 18a or surrounding this annular air cushion 32 may be arranged. These are just filled with air and elastic. They serve to compensate for a possible thermal expansion of the phase change material 25. It can easily be seen that due to the complete embedding of induction coil 18a and ferrite rods 20a, good heat dissipation to the phase change material 25 can take place.

On the underside of the left ferrite rod 20a, a temperature sensor 34a is shown, which can measure the temperature of the induction coil 18a and can be connected to a not shown here control of the induction heater 16 and the induction hob 1 1. An alternative or further possible temperature sensor 34a 'is arranged on the container bottom with some distance to induction coil 18 and ferrite rod 20, so that it essentially measures only the temperature of the phase change material 25. This temperature information may serve the controller as an emergency measure in the operation of the induction coil 18 a access, for example, with a reduction in electrical power at imminent overheating. Alternatively, an aforementioned fan 28 can be switched on for additional cooling.

Finally, a trigger 36 is shown in the phase change material 25, advantageously relatively central. It is also connected to a said control and serves with a correspondingly suitable actuator, such as a piezo element or a metallic snap spring to bring the melted by heat absorption or liquid phase change material 25 to give off the stored heat. This has been explained in the beginning. Instead of the thermal insulation 30a, which is intended to protect the interior of the induction hob 1 1 or of the housing 14 from undesired heat, it is also possible for a material layer with good heat conductivity to be provided in the case of another structural design. This is advantageous in particular if an environment which absorbs heat easily is provided or this material layer protrudes from the housing 14. In Fig. 3, another inventive induction hob 1 1 1 is shown with a hob plate 1 12 and a housing 1 14. In a coil container 122 with phase change material 125 therein a plurality of induction coils 1 18 are arranged. Advantageously, it is all induction coils 1 18 of the induction hob 1 1 1. The entire and continuous amount of phase change material 125 can provide reasonably good and balanced heat distribution. Especially in an induction hob of the type mentioned above with a large number of small and the surface of the hob plate 1 12 substantially continuously covering induction coils 1 18, such a configuration is advantageous because otherwise a large number of coil containers would be necessary. Other structural details may correspond to the embodiment of FIGS. 1 and 2. In Fig. 4, as part of a manufacturing process for an induction coil of an induction heater, it is shown how an elongated conductor 19 'is provided with an applied layer of phase change material 25 by means of an applicator 38 moving relatively from right to left. The layer thickness of the phase change material 25 can be chosen largely freely. It may be in the range of the thickness of the conductor 19 'or below or above, for example, 1, 5-fold to 4-fold. On the right-hand side it can be seen how the phase-change material 25-coated conductor 19 'is spirally wound, as is known for an induction coil. The distance between the individual windings is still disproportionately large. After the finished winding, an induction coil 18 according to FIG. 5 is present with a plurality of windings 19 of the conductor 19 '. These have approximately the same distance to each other, which is completely filled with Phasenwechselmatenal 25 each. By varying the application thickness in the application method according to FIG. 4, the distance can also be varied in a simple manner. Thus, the winding of the induction coil 18 is easier, since no additional spacer or the like. needed. These are formed by the Phasenwechselmatenal 25 yes.

In general, it can be said that a cross section for the induction coil or its winding can either be round, as indicated in FIG. 1, and these in particular be wound from a so-called stranded wire, ie a wire with a plurality of individual, each with an insulation coated strands. Likewise, a cross section may also be band-like according to FIG. 2, in particular standing upright and rectangular. Especially in the case of an induction hob 1 1 1 according to FIG. 3, a rectangular cross section for the coil winding is to be preferred, including a high number of turns and a small winding spacing. The dimensions of induction coils 1 18 are significantly smaller here, for example a diameter of 5 cm to 12 cm.

Claims

claims 1 . Induction heater with at least one induction coil, in particular in an induction cooking, characterized by a supply of Phasenwechselmatenal o- a container with Phasenwechselmatenal therein, wherein the induction coil is thermally conductively connected to the Phasenwechselmatenal and is at least partially embedded with at least its lower portion directly into the Phasenwechselmatenal or directly surrounded by this. 2. Induction heater according to claim 1, characterized in that a Phasenwechselmatenal is selected from the following group: paraffin, hard paraffin, plastic, salt, salt hydrate, alum, Glauber's salt, carboxylic acid amides, carboxylic acid esters, dipotassium hydrogenphosphate hexahydrate, sodium acetate trihydrate, thermoplastics and / or sugar .. 3. induction heating device according to claim 1 or 2, characterized in that a container for the Phasenwechselmatenal therein at least partially made of poor thermal conductivity material, preferably made of plastic, and / or thermally insulated, in particular at a downwardly facing or to an electronics Induction heater facing side, wherein preferably an upwardly flexible cover is provided. 4. Induction heater according to one of the preceding claims, characterized in that the induction coil is formed substantially flat and / or flat and is connected at least to a flat side with the Phasenwechselmatenal thermally conductive. 5. Induction heater according to one of the preceding claims, characterized in that the induction coil is completely embedded in the Phasenwechselmatenal and is surrounded directly by this. 6. Induction heater according to one of the preceding claims, characterized in that the induction coil has a plurality of windings of a solid conductor, preferably in band form, wherein in particular a conductor in ribbon edgewise is wound standing with intervals between the individual windings or to the respective adjacent band, wherein preferably phase change material in these intervals or in between. 7. Induction heater according to one of the preceding claims, characterized by a plurality of induction coils, wherein a separate supply or container is provided with phase change material for each induction coil, wherein preferably the plurality of stocks or containers with phase change material are thermally conductively connected together. 8. Induction cooking appliance, in particular induction hob, with at least one induction heating device according to one of the preceding claims. 9. A method for producing an induction heating device according to one of claims 1 to 7, in particular for an induction cooker, characterized in that is placed on a conductor for the induction coil in a previous step phase change material on the conductor and in a subsequent step, the induction coil is wound with defined distance between the windings. 10. The method according to claim 9, characterized in that the conductor has a strip shape, wherein in particular the induction coil is wound with an upstanding conductor in strip form with intervals between the individual windings or to each adjacent band, the thickness of the applied to the conductor Correspond to phase change material.