DE19853780A1 - Domestic cooking oven - Google Patents

Abstract

The domestic oven comprises at least one oven muffle with an inner chamber bounded by a wall in which a commodity to be cooked can be introduced through a loading opening in the muffle wall. There is an induction heater (3-18) generating a magnetic induction field changing in time when in operation. There is at least one heating body located in the muffle inner chamber and fastened to the wall, made out of material that can be heated inductively and which, in the operation of the induction heating device, is located in its induction field.

Description

The invention relates to a cooking oven and a method for Heating a muffle in a cooking oven. Under the term "Cooking" will be done and in the following all in one Garo fenmuffel usually performed heat treatment courses related to food (thermal accessories preparation of food) understood, especially roasting, baking, Grilling or braising but also drying or thawing of dishes as well as the preparation of yogurt at relative low temperatures, to name a few.

Household ovens and stoves are for heating of food in an interior (cooking space) of the oven muffle of the household oven or stove electric Wi radiant heaters, microwave feed and Heating by burning gas is known. Cooking with Radiant heaters, especially tubular tubular heaters, allows good cooking results for a variety of food items. The radiant heaters are on the muffle wall in the interior of the muffle (top heat radiator, grill radiator) or outside the muffle (bottom heat radiator) arranges. Radiant heater arranged in the interior require a special design effort since they electrically insulated and vapor-tight due to the muffle wall must be carried out due to an odor nuisance can cause grease splashes to evaporate on them and make cleaning the muffle difficult. Microwave cooking does not bring optimal cooking results for all food items.  

Gas stoves require a gas connection and hide through the Use of the explosive natural gas is somewhat safe security risk.

EP 0 464 390 A2 now includes a microwave oven a cooking chamber became known in which in addition to the Mi an induction coil is provided. The induction coil produces an induction alternating field (according to the writing, an electromagnetic table shaft) for inductive heating of a food container ters, especially a pan, made of magnetic material, especially made of iron, which on a rotating plate a dielectric material is placed in the cooking space. The induction coil is on below the rotating plate ordered and from this by a floor grid (mesh) separated from a non-magnetic metal that is for a Alternating induction field of the induction coil with a fre frequency between 20 kHz and 30 kHz is permeable. The Ma The width of the metal grid is chosen so that microwaves len with a frequency of 2.45 GHz are not transmitted can be kept in the cooking space. That in the food container ter located food is in this well-known Kombinati onsgarofen with induction heating practically like on one known induction cooker cooked by the cooking product halter (and also according to the explanations in this document the surface of the food) by creating eddy currents men is heated inductively and the heat via the heat con is transferred to the food to be cooked. With microwave operation the food is cooked directly by the excitation of water molecules in the food as in a conventional microwave oven heated. The design effort in this known Kom binationsgarofen is quite high. It must also always be  special food container suitable for induction cooking made of a magnetic metal such as iron.

The invention is based on the object, a cooking oven, especially a household oven, and a method to specify a heating muffle for which the interior of the muffle is heated in a special way.

The object is achieved according to the invention by a oven with the features of claim 1 or by a method having the features of claim 27.

The oven, especially household oven, includes

• a) at least one oven muffle with one of a muffle wall limited muffle interior, which by a Be loading opening in the muffle wall with food to be cooked is sendable,
• b) a magne that changes over time in operation table induction field generating induction heating Facility, and
• c) at least one in the muffle interior and radiators made of induc. attached to the muffle wall tiv heated material that in the operation of the Indukti on heating device coupled to their induction field is.

The method of heating a muffle in a cooking oven, especially a household oven, with one of one Muffle wall bounded by a muffle interior Feed opening in the muffle wall of the food to be cooked is distinguished by the fact that at least one in the muff The interior of the rock is fixed to the wall of the muffle  and at least partially inductively heatable radiators with a magne that changes over time in operation table induction field generating induction heater tion is heated inductively.

The induction heating device heats the one or more in the sleeve inductively heatable radiators arranged in the interior of the by changing a time, especially periodically Lich and generally location-dependent (vectorial) ma magnetic induction field (magnetic flux density) or magnet generated field that the corresponding radiator at least partially penetrated and in this due to physical Effects creates heat. This inductive, i.e. H. through a time Lich changing magnetic induction field generated Thermal energy is transferred from the radiator to the muffle interior emitted, mainly via heat radiation. That warmth can be used in a cooking mode of the oven for cooking in Muffle interior, at a distance from the radiator or radiators and arranged on the associated food supports be applied. The radiator is therefore not a food support ger intended for carrying food, but excludes Lich for heating, and is therefore also on the muffle wall (removable or non-removable) attached.

Since in the oven and the method for heating a Ga rofenmuffel the radiators by inductive coupling to the Induction heating can be heated, electrical accessories through the muffle wall, as in the resistive heated, known radiant heaters (Again heaters) are not required. This will improves the thermal insulation of the furnace muffle and the constructive effort of the oven muffle itself reduced.  

Advantageous refinements and developments of the Garo fens and the method result from that of claim 1 and claim 27 each dependent claims.

The inductive heating of the radiator or radiators by the Induction field of the induction heating device can cause can also be achieved through two physical effects, which are preferably combined with one another.

A time-changing magnetic induction field or similar Outer magnetic field generated by electromagnetic Induction on around the field lines of the induction field running electric swirl field. In an electric line tendency material, i.e. a material in which free charges are present, the electric swirl field causes electri eddy currents (macroscopic circular currents), their ener gie depending on the electrical resistance of the conductive Material and the inductive coupling converted into heat (Joule heat loss). To take advantage of this effect the thermal eddy current loss is at least egg ne radiator at least from the induction field of the inductors ons penetrated areas made of electrical conductive material formed.

The second effect in inductive heating occurs in magne tisizable (magnetic) materials whose magneti hysteresis in an external magnetic field points. Due to the constant changes in the time of the Field of induction each time subjected to the hysteresis gnetization processes in the magnetic material is in the material generates heat loss. This effect of the hyster Reserve losses are particularly strong in ferromagnetic mate rialien, but also occurs in antiferromagnetic and fer  rimagnetic materials, and is used for the oven exploited by the at least one radiator at least in from the induction field of the induction heater third areas from a hysteresis behavior magnetizable material. A high level of efficiency of induction heating is achieved through the use of, ferro magnetic material for at least part of the heating body reached.

Each radiator is preferably immediately adjacent arranged to the muffle wall, so that no food to be cooked on it can be filed. The radiator or radiators can also thermally insulated from the muffle wall on this befe be steady.

At least one inductively heatable radiator can be used in egg ner special embodiment rotatable about an axis of rotation be for more even heating of the muffle interior. This embodiment in combination is particularly advantageous tion with a circulating air fan, by at least one in the muff Fan interior arranged as a rotatable, induc Heatable radiator is provided and little least partially made of an inductively heatable material stands.

In the presence of a forced air fan, it can also one in front of the fan wheel in the muffle interior Air guiding body for guiding the circulated by the impeller Air can be provided as an inductively heatable radiator and at least in some areas made of induction heat rem material exist. The muffle wall can also be used at least in an area adjacent to the impeller partially consist of an inductively heatable material  and / or an additional one arranged in the muffle interior induction-heated radiator assigned to the impeller his.

The inductive heating of the at least one radiator is used alone or in one or more cooking modes also in combination with other types of heating as with for example, circulating air or hot air mode, for cooking in inserted into the muffle interior (cooking space) puts. To do this, the performance of the induction heater depending on the geometric arrangement relative to the radiators and their material selected that cooking temperatures of typically up to 200 ° C, esp special 250 ° C and preferably 300 ° C in the muffle interior can be enough. The direct induction heating the muffle wall has the advantage that without special Food carriers can be cooked.

Inductive heating of the radiators in the interior of the muffle can also be used for pyrolytic removal of dirt tongues (residues) inserted on the muffle inner wall become. The performance of the induction heater is then to be interpreted so that the pyrolysis (pyrolytic self cleaning) required temperatures of typically up to at least 450 ° C, preferably up to at least 500 ° C the muffle inner wall can be reached.

The induction heater can be used as a whole or in parts len arranged inside or outside the muffle interior be nice. However, the arrangement outside the Muffle interior as no breakthroughs through this measure in the muffle wall for electrical leads of the inductor tion heater are required, the certain  Would represent weakening of the thermal insulation, and also additional measures to avoid too strong Heating and / or contamination of the muffle not arranged parts of the induction heating device are necessary. So that the induction field of induction heating now with sufficient intensity for heating body can get into the muffle interior is the muffle wall at least in a partial area for the induction field of the induction heating device at least largely by casual (transmissive, transparent). In general, it will accomplished that the muffle wall in the little at least largely for the induction field permeable part of a non-magnetic and electrically non-conductive material. Preferred Ma materials for the muffle wall at least in the for the Induction field at least approximately permeable areas are not magnetic stainless steels, glasses, glass ceramics and ceramics, in particular silicon nitride ceramic and Si licium carbide ceramic.

The induction arranged outside the muffle interior heating device can in one embodiment at least one around the muffle wall, preferably around a jacket wall dung, running induction coil with at least one win dung.

But it can also in another embodiment or Training one or more only one at a time Induction coils assigned to radiators may be provided, which are preferably designed as flat coils.

Especially when different parts of the muffle wall is assigned an induction coil, however  also in other cases, it is possible the different Induction coils not at the same time, but one after the other to operate. Assigned the different wall parts Radiators are then inductively heated one after the other. There through can on the one hand the well-known conventional Be Types of heating such as top and bottom heat mode simulated Types of heating and on the other hand also new types of heating through different combinations of heated radiators pern and possibly walls are generated, in particular special to the food and its arrangement in the muffle space can be coordinated, for example under incl drawing of heaters on the rear wall and the side walls that of the oven muffle.

In general, the various induction coils from a common electric field generator (Span voltage generator, induction generator) which supplies the one desired magnetic induction field corresponding electric field (an electric voltage) generated. Be you drive the different induction coils other (sequential operation), the performance of the In production generator in a special embodiment only the maximum power of the individual induction coils and not the sum of the power of all induction coils speak as with the simultaneous operation of all inductors on spools. So there can be a field generator with a gerin lower nominal power (inductive active power) the. This is particularly advantageous for pyrolysis Mode of operation that requires higher performance anyway are.

In one embodiment, at least one and are preferred have all induction coils made of at least one metal  wire wound (single wire or multi wire wound in induction coils).

In another embodiment, at least one induc tion coil of the induction heater with one on egg ner surface of at least one electrically insulating Carrier body, preferably adhesive, arranged inductors structure. The carrier body is in a front partial embodiment thermally to the muffle wall coupled or even forms part of the muffle itself wall. This can also be used in the induction structure self-generated Joule heat loss through the immediate direct thermal contact of the induction structure Surface of the carrier body at least partially over the Carrier body to the muffle wall or when the carrier body forms part of the muffle wall itself the muffle interior are given. This the effect degree of induction heating increasing effect is ver strengthens by the carrier body from a thermally good lei tendency material is formed. Preferred materials for the carrier body is a ceramic, in particular a sili cium nitride ceramic or a silicon carbide ceramic, a Glass ceramic or a glass. Finally, the carrier body also composed of several partial carrier bodies be, which each carry part of the induction structure. The individual parts of the induction structure on different NEN partial carrier bodies are then electrically ver bound. The partial carrier bodies can, for example, each be assigned to a muffle wall.

To further explain the invention, reference is made to the drawing mentions in which embodiments of the  relevant parts of an induction oven are shown table.

Show it:

Fig. 1 is a Garofenmuffel with a ge to the muffle wound induction coil in a view from the top front,

Fig. 2 is a Garofenmuffel having disposed at the bottom of the oven muffle induction heating ei ner rear view of the bottom,

Fig. 3 is a Garofenmuffel each having an induction heating unit on each mold wall,

Fig. 4 is an induction heating using an induction structure to a support body in cross-section,

Fig. 5, the induction heating unit shown in FIG 4 in a plan view.

Fig. 6 shows a muffle with an inductive top heat and bottom heat in a view from the front and

Fig. 7 is a oven muffle with an inductive top heat and an inductive hot air system in a since section.

Corresponding parts are provided with the same reference numerals in FIGS. 1 to 7.

Fig. 6 shows a front view of a, for example cuboid, oven muffle 4 of a cooking oven with a muffle wall 2 , which closes a muffle interior 41 to (limited). At the front of the oven muffle 4 , a loading opening 41 is seen in the muffle wall 2 before, through which food is brought into the muffle interior 41 and can be placed on baking trays, not shown, such as baking, grilling grates, rotisserie spit or the like. For the insertion and support of food carriers, several guides 44 are arranged on the two side walls 25 and 26 of the muffle wall 2 .

Below the ceiling wall 27 of the furnace muffle 4 is a Reali sizing a top heat in the muffle interior 41 by (top heat radiator) 47 for heating the muffle interior 41 from above with radiant heat. The heating body 47 is fastened to the ceiling wall 27 via fastening means 45 and 46 and runs essentially parallel to the (flat) ceiling wall 27 . In the example of Fig. 6, the radiator 47 is formed from a meandering heating rod which has no electrical connections, but can also be closed by connecting the ends. There are therefore no openings in the muffle wall for electrical supply lines. Rather, the radiator 47 is completely arranged in the muffle interior 41 . The shape of the radiator 47 can largely be chosen as desired within the dimensions of the muffle interior 41 and is preferably provided with the largest possible effective radiation area. The radiator 47 can also be plate-shaped in example.

On the opposite side of the ceiling wall 27 , that is to say on the outer surface 20 of the muffle wall 2 , an induction heating unit (inductor) 17 is arranged outside the muffle interior 41 for inductively heating the radiator 47 . The induction heating unit 17 includes at least one arranged in egg nem housing 171 and as a parallel to the ceiling wall 47 lying flat coil formed induction coil 170 , which generates a magnetic induction field B2 when a time-varying electric field.

The radiator 47 is now formed from an inductively heatable material in order to be able to serve as a susceptor for the induction field B2 of the induction heating unit 17 .

Inductively heatable materials are, in particular, electrically conductive materials in which heating occurs in an external temporally changing magnetic induction field due to eddy current losses, and magnetizable materials with hysteresis, in particular ferromagnetic, antiferromagnetic or ferromagnetic materials, which are in the time-variable induction field are heated due to hysteresis losses. In the case of magnetic materials, the achievable temperature at a given inductive heating output also depends on a critical temperature of the material above which the respective magnetic material loses its magnetization and can therefore only be heated inductively via eddy current losses if it also has sufficient electrical conductivity having. For ferromagnetic materials, the critical temperature is called the Curie temperature. Examples of electrically conductive and non-magnetizable materials are copper (Cu), aluminum (Al) and other non-magnetic metals and metal alloys and in particular also graphite (C), which is successfully used in induction heating in crystal growth. Examples of magnetizable and electrically practically non-conductive materials are the ferrimagnetic ferrites, which are increasingly being used in transformer cores and which are caused by the incorporation of foreign atoms such as e.g. B. manganese (Mg) - or aluminum (Al) atoms in an iron oxide structure such as magnetite, it can be generated. Examples of the particularly preferred electrical, albeit usually relatively poor, conductive and magnetizable materials with hysteresis are the ferromagnetic metals iron (Fe), nickel (Ni) and cobalt (Co) and alloys with or from these three metals , in particular steels (iron alloys), and some other magnetizable substances and alloys, for example the ferromagnetic, so-called Heusler alloys of manganese with other substances and the antifer romagnetic materials manganese oxide (MnO) and manganese fluoride (MnF ₂ ). If the material itself does not have sufficient corrosion resistance, it can also be provided with an anti-corrosion layer.

So that the induction field B2 of the induction heating unit 17 can penetrate to the radiator 47 in a sufficient intensity, the muffle wall 2 is located between the radiator 47 and the associated induction heating unit 17 , the area, namely the ceiling wall 27 , from one for the induction field B2 at least predominantly Transmitting material formed, in particular from non-magnetizable and / or, dielectric material that is also sufficiently temperature and corrosion resistant for use in a muffle, for example a non-magnetic stainless steel, a glass, a glass ceramic or a ceramic.

The bottom wall 24 of the muffle wall 2 is now assigned to realizing a lower heat, preferably also arranged outside the muffle interior 41 , induction heating unit 14 with at least one induction coil 140 and a housing 141 for the induction coil 140 . In contrast to the top heat, the bottom heat is not realized with its own radiator arranged in the muffle interior 41 , but with the muffle wall 2 itself; in contrast to the top heat, it is now itself made of an inductively heatable material, in particular that already in connection with the radiator 47 mentioned materials, and is thus heated by the time-varying induction field B1 of the induction heating unit 14 in its operation and this heat is given off to the muffle interior 41 before usually by heat radiation. For example, the bottom wall 24 may consist of an enamelled, magnetizable steel sheet, which is connected to the other part of the muffle wall 2 . If the remaining part of the muffle wall 2 consists of a non-magnetizable stainless steel sheet, the connection can be made, for example, by welding or soldering and the connected sheet metal can be enamelled after the muffle has been formed. This type of unheat has the advantage that no disruptive radiator is arranged in the lower area of the sleeve interior 41 , corresponding to the conventional external bottom heat. In one embodiment, not shown, one or more additional bodies made of inductively heatable material, which are referred to as induction susceptors or susceptors for short, can be applied to the bottom wall 24 from outside or inside in thermal contact, for example by applying a susceptor layer. In this variant, the muffle wall 2 itself does not have to be made of inductively heatable material. However, the lower heat can also be realized with its own radiator in the same way as the upper heat.

In the rear area of the furnace muffle, a hot air or recirculation system is provided for circulating the air in the muffle interior 41 with an impeller 62 and an air baffle (air baffle means) 64 . The air baffle 64 is arranged in the direction of the loading opening 40 in front of the impeller 62 and the impeller 62 in front of a rear wall of the muffle wall 2 covered by the air baffle 64 . The air baffle 64 has a central suction opening 65 and a plurality of blow-out openings 67 . Through the central suction opening 65 air is rotated by the blower serad 62 from the air guiding plate 64 in front of the part of the muffle interior 41 , in which the food is also arranged, sucked in and through the blow-out openings 67 back into this part of the muffle interior 41 blown out. There is a circulating air flow (air circulation) in the muffle interior 41 , which brings good cooking results in some cooking modes. If the fan wheel 62 is now assigned its own heating for heating the circulated air, a hot air system is created which can be used independently for heating the muffle 4 . The heating of the hot air system can be carried out conventionally by a resistively heated ring heater around the impeller 62 or according to the invention by induction heating.

Fig. 7 shows an embodiment of a oven muffle 4 with a hot air system with induction heating. In front of a rear wall 23 of the muffle wall 2 , an impeller 62 of a radial blower or tangential blower, in particular a paddle wheel with a plurality of blades or drum wheel, is arranged in the muffle interior 41, said wall having an axis of rotation guided through the rear wall 23 (drive axis, drive shaft) 63 with an electric one Drive motor 70 is connected. The impeller 62 is separated from the front main area of the sleeve interior 41 , into which the food to be cooked can be separated by an air baffle 64 . This air guide plate 64 has shown in FIG. 7 is a simple plate-shaped configuration with a central suction opening 65 and a position spaced from the muffle edge 2, and between the muffle wall 2 a circumferential blowout port 66 (or a plurality of blow-out openings) is formed. When the drive motor 70 is switched on, the impeller 62 rotates and generates a circulating air flow which flows through the suction opening 65 to the impeller 62 and then flows outward to the blow-out opening 66 . An induction heating unit 18 with an indicated induction coil, which is separated from the drive motor 70 by an intermediate plate 71 , is arranged on the rear of the oven muffle 4 behind the rear wall 23 . The induction heating unit 18 generates a time-varying magnetic induction field B3 during operation.

There are basically at least four possibilities for (indirect) inductive heating of the circulating air circulated by the fan wheel 62 , which can also be combined with one another as desired:

• - First possibility: The air baffle 64 is at least in an area around or in the formation of a suction orifice 65 covering grid or web in the suction opening 65 from an inductively heatable material forms ge, so that the air flowing past is heated by the air baffle 64 . In particular, the air baffle 64 can be provided, at least in this area, with a coating made of a material that can be heated inductively.
• - Second possibility: The fan wheel 62 itself consists at least partially of an inductively heatable material, so that the air in the fan wheel 62 is heated directly.
• Third possibility: An additional radiator, not shown, is arranged in the area behind, in front of or around the impeller 62 in the muffle interior 41 in front of the rear wall 23 . Good results could be achieved here with a commercial heat sink for electronic components in reverse of its function.
• Fourth possibility: the rear wall 23 consists at least in some areas of an inductively heatable material and heats the circulating air. Here, in combination with one of the other options, care must be taken that the rear wall 23 also allows the induction field B3 of the induction heating unit 18 to pass through, so that the parts 41 inside the muffle can also be heated.

In the first three possibilities, the rear wall 23 should be made of an inductively non-heatable material so that the induction field B3 of the induction unit 18 can penetrate the muffeline interior 41 with a sufficient field strength. In the second option, a rotatable, inductively heatable and connected to the Muffelwan heater is realized, which can of course be arranged in a generalization elsewhere in the Muffelin interior 41 and / or does not have to have a flow-related function as a fan. A rotatable radiator basically has the advantage that the heat (radiation over the surface) is distributed more evenly.

Below the ceiling wall 27 of the muffle wall 2 is again, as in FIG. 6, an inductively heatable radiator hen, which, in contrast to FIG. 6, is designed in the form of a continuous plate, on the ceiling wall 27 with fastening means 55 from preferably electrically insulating and thermal insulating material, for example Kera mik, attached and designated 57 . This radiator 57 is an induction heating unit 17 above the ceiling wall 27 associated, the induction field B2 heats the radiator 57 .

In a modification not shown, the heating element 57 and the associated induction heating unit 17 can also be arranged together in a heating chamber arranged above the ceiling wall 27 . The ceiling wall 27 is then formed from transparent material for the heat radiation of the radiator 57 , for example glass or glass ceramic.

Between the induction heating unit 18 and the rear wall 23 and the induction heating unit 17 and the top wall 27 , a muffle insulation 42 surrounding the entire muffle wall 2 is arranged in FIG. 7 in order to heat the induction heating units 16, 17 and 18 from excessive heat from the muff interior 41 to protect.

The heaters which can be heated by induction are arranged in all embodiments in such a way that - at least reasonably - no food can be placed on them. This is achieved in particular by arranging the radiator in the edge region of the muffle interior 41 near the muffle wall 2 . In addition, each radiator is releasably or non-releasably connected to the muffle wall 2 .

Figs. 1 to 5 show advantageous embodiments of the induction heating device for the oven muffle 4, wherein the radiator located in the muffle inner space 41 are not shown for clarity.

In Fig. 1, an all-round closed jacket wall of the muffle wall 2 , which connects the rear wall 23 and loading opening 41 arranged on its end faces, is designated by 22 . Around this jacket wall 22 of the muffle wall 2 , an induction coil 13 is wound as part of an induction heating device from an electrically insulated coil wire 35 . At two at the two ends of the coil wire 35 provided electrical connections 31 and 32 , a time-varying electrical voltage of a field generator - not shown - can be applied as a further part of the induction heating device, which around the induction coil 13 also a time-varying magnetic induction field B. induced. Between the coil wire 35 of the induction coil 13 and the muffle wall 2 which is hot during operation, thermal insulation is generally provided, analogously to FIG. 7, which is not shown in FIG. 1. For example, the coil wire 13 can be wrapped around a conventional mineral fiber insulation, and even the coil wire 35 can help to secure the insulation. The muffle wall 2 is made of an inductively neutral, ie non-heatable, material, so that the induction field B can penetrate into the muffle interior 41 and heat the radiators, not shown, located there. In a modification, part of the muffle wall 2 can again be heated inductively.

Fig. 2 shows a further schematic of a quaderför shaped oven muffle 4 in a rear view. Below the Bo denwand 24 of the muffle wall 2 , an induction coil 6 is arranged with two electrical connections 60 and 61 , which is held in or on a carrier device 5 . In the induction coil 6 is formed as a preferably parallel to the bottom wall 24 extending flat coil and from the exemplary embodiment shown in the form of a rectangular spiral. The carrier device 5 can be a housing with stanchions in which the ge wound from one or more wires induction coil 6 is inserted, or a carrier body on which the induction coil 6 is arranged, for example in the form of a structured electrically conductive layer (induction structure ). The induction coil 6 is used for inductive heating of the bottom wall 24 of the furnace sleeve 4 , which consists of correspondingly inductively heatable material, or a radiator, not shown, under half or above the bottom wall 24 as bottom heat as in Fig. 6 and / or for cleaning the muffle inner surface 21 in the usually most polluted floor area during a pyrolysis operation.

In the embodiment according to FIG. 3, each wall of the furnace muffle 4 is assigned its own induction heating unit, namely the bottom wall 24 an induction heating unit 14 , the top wall 27 an induction heating unit 17 , the rear wall 23 an induction heating unit 18 and the two side walls 25 and 26 induction heating units 15 or 16 . In each induction heating unit 14 to 18 each comprises at least one ne - not shown - induction coil for generating a magnetic induction field. Furthermore, each induction heating unit 14 to 18 is electrically connected to a control device 9 . The control device 9 is in turn connected to an electrical field generator 8 and applies the electrical alternating field generated by the field generator 8 or its electrical alternating voltage as a function of a predetermined or predeterminable process sequence to one, several or all induction heating units 14 to 18 . In an advantageous embodiment, the control device controls the heating process in the furnace muffle 4 in such a way that only one of the induction heating units 14 to 18 is flowed through by the electrical alternating current of the field generator 8 and the associated radiator or the associated muffle wall is heated by its induction field. As a result, on the one hand with a sufficiently rapid cycle sequence of switching between the induction heating units 14 to 18 even with only one field generator 8 during cooking, uniform heating of the muffler interior 41 is achieved. On the other hand, in a py rolysis mode, in which it is not a matter of uniform heating of the muffle interior 41 , but only the cleaning of the muffle interior surface 21 of cooking residues, the walls 23 to 27 are successively heated and cleaned individually by means of the radiators, so that a lower nominal power of the field generator 8 and a low energy consumption for the energy-intensive pyroly serification process are required. As a radiator in the loading area of the side walls 25 and 26 , in particular guiding grids or guide rails such as the guides 44 in FIG. 6 can be used.

That into the induction coils or induction heating devices gene in all embodiments from the corresponding field gene rator coupled time-varying electric field (or the corresponding electrical voltage) preferably a frequency or a frequency spectrum from the Medium frequency range with a between about 20 kHz and about 100 kHz (sometimes referred to as high frequency net), preferably at least 25 kHz, the field in particular a periodically changing polarity or can have periodic pulses of the same polarity. It can also induction fields with higher or lower lower frequency components are generated. That from the inductors generated magnetic induction field B follows in in all cases essentially linear to the electrical gene ratorfeld.

In all embodiments, a stray magnetic field in the front area of the furnace muffle 4 outside the muffle wall 2 can be reduced by additional magnetically conductive bodies for guiding the induction field.

The induction heating device of FIG. 1 may as well as all other induction heating devices described, the oven muffle 4 of the cooking oven in the normal case for cooking in the muffle interior 41 heat contained food to be cooked on corresponding maximum cooking temperature of the usual depending on the mode, between 200 ° C and 300 ° C and in a Cleaning mode for pyrolytic removal of impurities in the muffle inner wall at pyrolysis temperatures of typically at least 450 ° C to 500 ° C. The effective heating power of the induction heating device is determined primarily from the nominal electrical power of its field generator, the efficiency (inductive heatability or losses) of the material of the radiators or the sleeve wall or the susceptor, the inductance of the induction coil (s) and the distance between them Induction coil (s) of the body to be heated. A ferromagnetic material is preferably selected for the radiator or radiators, the Sen Curie temperature above the respective maximum cooking temperature or pyrolysis temperature. For example, the Curie temperature of pure iron is 744 ° C, pure cobalt at 1131 ° C and pure nickel at 372 ° C and in most magnetizable iron alloys such as steels well above 500 ° C, so that the radiator reaches sufficiently high radiation temperatures become.

The effective heating power of the induction heating can be set differently in all embodiments in different sub-areas of the muffle interior 41 , by using materials with different degrees of induction heat for the radiators in these sub-areas, for example different ferromagnetic materials with different sizes of permeabilities and / or Curie temperatures. So even a targeted heating in different food support levels is possible, for example, at the level of these food support levels, the side walls 25 and 26 assigned radiators or the side walls 25 and 26 themselves and the rear wall 23 assigned radiators or the rear wall 23 itself a clearly have greater magnetic permeability and / or higher Cu temperature than in between.

FIGS. 4 and 5 show a special embodiment of an induction heating unit, for example, in one of the embodiments according to FIGS. 2, 3, 6 and 7 were used who can the. The induction heating unit comprises a preferably substantially plate-shaped and generally made of an electrically insulating material carrier body 28 and a arranged on a first surface 200 of the carrier body 28 induction structure 3 , which has a conductor track 30 , which is in the form of a round spiral from an outer Connection 33 extends to an inner connection 32 in the center, is formed. The spiral of the induction structure 3 has a plurality of turns, but can also have only one turn. A susceptor could also be applied to the free surface 210 of the carrier body 28 .

To the flat form contacts 32 and 33 of FIG. 5 are connected electric lines, for example by soldering, the induction for electrically connecting structure 3 having a heat generator 10 and an induction field generator 11 as well as a measuring device 12th Between the induction structure 3 and the heating generator 10 on the one hand and the induction field generator 11 on the other hand, an electrical switch 50 or 51 is connected to couple or disconnect the induction structure 3 from the corresponding voltage supply by a control device not shown. In the operating state shown, only the induction field generator 11 is connected to the induction structure 3 via the closed switch 51 , the other two switches 50 and 52 are open. An induction AC voltage U _I with a frequency between about 20 kHz and about 100 kHz, preferably at least 25 kHz, induces a magnetic induction field B of a corresponding frequency in the induction structure 3 .

An additional heating option is provided by the heating generator 10 , which, when the switch 50 is closed, applies a low-frequency heating alternating voltage U _R , in particular mains voltage at 50 Hz (230 V or 400 V), to the induction structure 3 and heats it due to its ohmic resistance R resistive . The resulting Joulesche loss heat me is transferred to the sleeve wall 2 via the support body 28 which is in direct thermal contact with the induction structure 3 . In such a resistive To set heater, the support body 28 should be made of a thermally highly conductive and electrically non-conductive material and be thermally coupled to the muffle wall 2 .

The measuring device 12 , which can be connected to the induction structure 3 in a measuring operation via the switch 52 , generates a measuring voltage U _M in order to measure the impedance or an impedance change of the induction structure 3 , for example with the aid of a four-pole measurement or a measuring oscillator circuit. The impedance of the induction structure 3 provides information about certain process variables of the cooking process. Thus, a change in the ohmic resistance of the induction structure 3 as a measure of a temperature change and a change in the inductance as a measure of an approach or distance of a food support from metal in the muffle interior 41 can be used. For food carrier detection, the induction structure 3 is supplied with a high-frequency measuring voltage U _M above 100 kHz, typically 300 kHz. A threshold detector, not shown, which is part of a control device together with the switches 50 to 52 , compares the measured inductance of the induction structure 3 with a predetermined threshold value and switches the switches 50 and 51 as a function of falling below or exceeding the threshold value, so that the heating of the oven by the Heizge generator 10 and the induction field generator 11 is only switched on or remains when or as long as there is a good carrier in the muffeline interior 41 . In the approximate shape exporting according to Fig. 5 also Heizgenera gate 10 and / or the measuring device 12 of course may be omitted if the additional functions are not desired.

Preferred materials for the carrier body 28 are glass, a glass ceramic or a ceramic, preferably a silicon nitride ceramic or also a silicon carbide ceramic. In particular, in these embodiments, the induction structure 3 can also be formed with electrically conductive polysilicon (polycrystalline silicon). As a material for the induction structure 3 can also form an elemental metal such as copper (Cu), nickel (Ni), aluminum (Al), titanium (Ti), molybdenum (Mo), or chromium (Cr) or a metal alloy in all embodiments from two or more metallic components, in particular the aforementioned metals, or a metal compound such as preferably a metal nitride, for example titanium nitride, or a metal carbide, in particular tungsten carbide or tantalum carbide, can be used. The induction structure 3 according to FIG. 4 and FIG. 5 can, by applying an electrically conductive layer on the carrier body 28 by a suitable process from thin-film or thick-layer technology, in particular chemical deposition from the gas phase (CVD), thermal vapor deposition, preferably in vacuum, a sputtering process, a mechanical printing process (printing), a soldering process, a melting process or also alloying, and subsequent structuring of the layer, in particular by photolithography with suitable masks and etching, are produced. The induction structure 3 produced using these methods adheres to the surface 200 of the carrier body 28 (adhesive connection). Furthermore, a prefabricated induction structure 3 , for example a stamped metal foil, can be pressed or pressed or glued onto the first surface 200 of the carrier body 28 under a mechanical pressure.

A plurality of induction structures and also an induction structure can also be arranged on a plurality of subcarrier bodies on a carrier body. In a modification, not shown, of the embodiment according to FIG. 1, it is also possible to manufacture an induction coil running around the entire muffle wall from conductor tracks, in which sections of conductor tracks are brought up on a carrier body assigned to a wall of the muffle wall and to form a ring around the entire muffle wall in the form of a spiral induction coil to be put together, the individual conductor track pieces of the induction coil then being electrically connected to one another at the edges where the walls and carrier bodies meet, for example by soldered connections and / or cable pieces.

Reference list

2nd

Muffle wall

3rd

Induction structure

4th

Oven muffle

5

Carrier device

6

Induction coil

7

Muffle interior

8th

Field generator

9

Control device

10th

Heating voltage generator

11

Induction voltage generator

12th

Measuring voltage generator

13

Induction coil

14

to

18th

Induction heating unit

20th

Muffle outer surface

21

Muffle inner surface

22

Jacket wall

23

Back wall

24th

Bottom wall

25th

,

26

Side wall

27

Ceiling wall

28

Carrier body

30th

Conductor track

31

to

34

Connection

35

Coil wire

40

Loading opening

41

Muffle interior

50

,

51

,

52

switch

60

,

61

Connection

200

,

210

surface
U _R

Heating voltage
U _I

Induction voltage
U _M

Measuring voltage

Claims (30)

1. cooking oven, in particular household cooking oven,

• a) comprising at least one oven muffle with a muffle interior delimited by a muffle wall into which food can be introduced through a loading opening in the muffle wall,
• b) an induction heating device ( 3 , 6 , 8 , 9 , 11 , 13 to 18 ) generating a time-varying magnetic induction field (B, B1 to B3), and
• c) at least one radiator ( 47 , 57 , 62 , 64 ) arranged in the muffle interior and fastened to the muffle wall and made of inductively heatable material which is arranged in the induction field during operation of the induction heating device.

2. Cooking oven according to claim 1, wherein each radiator in the Edge area of the muffle interior near the muffle wall is arranged. 3. Cooking oven according to claim 1 or claim 2, in which one of the preceding claims, in which at least one Radiator at least from the induction field of the inductor tion heater penetrated sub-areas magnetizable, hysteresis behavior in particular ferromagnetic material. 4. Cooking oven according to one of the preceding claims, at the at least one radiator at least from the induc  penetrated field of induction heating Partial areas made of an electrically conductive material, in particular a metal. 5. Cooking oven according to one of the preceding claims, at around at least one inductively heatable radiator an axis of rotation is rotatable. 6. Cooking oven according to one of the preceding claims with at least one arranged in the muffle interior Ge blowing wheel ( 62 ). 7. Cooking oven according to claim 5 and claim 6, wherein the impeller ( 62 ) is provided as an inductively heatable heating element and for this purpose at least partially consists of an inductively heatable material. 8. Cooking oven according to claim 6 or claim 7 with in front of the fan wheel ( 62 ) arranged in the muffle interior air guide means ( 64 ) for directing the air drawn in and blown out by the fan wheel ( 62 ). 9. Cooking oven according to claim 8, wherein the air guide means ( 64 ) at least in some areas consist of inductively heatable material. 10. Cooking oven according to one of claims 6 to 9, wherein the muffle wall in an adjacent to the blower wheel ( 62 ) th area ( 23 ) at least partially consists of an inductively heatable material. 11. Cooking oven according to one of the preceding claims, in which

• a) the induction heating device is arranged outside the muffeline interior and
• b) the muffle wall is at least largely permeable to the induction field of the induction heating device in at least one partial area.

12. Cooking oven according to claim 11, wherein the muffle wall in at least largely for the induction field casual areas at least partially from a not magnetic stainless steel, a glass, a glass ceramic or a ceramic, especially a silicon nitride Ceramic or a silicon carbide ceramic is. 13. Cooking oven according to one of claims 11 and 12, in which the induction heater at least a little least partially around the muffle wall Duct coil includes at least one turn. 14. Cooking oven according to claim 13, wherein the muffle wall has a closed jacket wall ( 22 ), on one end side of the jacket wall a rear wall ( 23 ) and on the other front side of the jacket wall, the loading opening and in which the induction coil ( 13 ) around Shell wall runs. 15. Cooking oven according to one of the preceding claims, at which the induction heater for each radiator at least one associated with this radiator preferably substantially flat-shaped inductors on spool includes.   16. Cooking oven according to one of claims 13 to 15, in which at least one induction coil from at least one Metal wire is wrapped. 17. Cooking oven according to one of claims 13 to 15, wherein at least one induction coil is formed with an induction structure arranged on a surface of at least one dielectric carrier body ( 28 ). 18. Cooking oven according to claim 17, wherein the induction structure sticks to the carrier body. 19. Cooking oven one of claims 17 and 18, wherein the Carrier body forms part of the muffle wall. 20. Cooking oven according to one of claims 17 to 19, in which the carrier body made of a good heat-conducting material exists and in thermal contact on the muffle wall application. 21. Cooking oven according to one of claims 17 to 20, in which the carrier body composed of several partial carrier bodies is set, each part of the induction have structure, the individual parts of the In Production structure electrically connected are. 22. Cooking oven according to one of the preceding claims, in which the induction heating device comprises a plurality of induction coils ( 14 to 18 ) and an electrical field generator ( 8 ) which can be electrically connected or connected to the induction coils. 23. Cooking oven according to claim 22, wherein the induction heating device comprises a control device ( 9 ) which in a predetermined or predeterminable order or selection one after the other only one of the induction coils ( 14 to 18 ) connects to the field generator. 24. Cooking oven according to one of the preceding claims, at which the induction heater with respect to Heating power is designed so that in one or more Other cooking modes in the muffle interior to the Ga food in the muffle interior desired cooking temperatures from typically to little at least 206 ° C, in particular up to at least 250 ° C and can preferably be generated up to at least 300 ° C. 25. Cooking oven according to one of the preceding claims, at which the induction heater with respect to Heating power is designed so that in a pyrolysis operating mode for cleaning the muffle wall in the socket pyrolysis system required by pyrolysis temperatures of typically up to at least 450 ° C, in particular up to at least 500 ° C, can be generated. 26. Cooking oven according to one of the preceding claims, at the at least one radiator via thermal insulation Fixing fasteners on the muffle wall is increasing 27. Method for heating an oven muffle of a cook oven, especially a household oven, with a muffle interior delimited by a muffle wall, in through a loading opening in the muffle wall  dung food can be introduced, in which at least one in Muffle interior arranged on the muffle wall strengthened and at least partially inductively heated rer radiator with one in operation a time generate changing magnetic induction field (B) the induction heating device is heated inductively. 28. The method of claim 27, wherein the at least one ne inductively heated radiators at least heat predominantly in the form of heat radiation on the muffle gives off interior. 29. The method of claim 27 or claim 28, wherein at least one in one or more cooking modes Part of the radiator with the induction heater is heated so that in the muffle interior to the Ga food in the muffle interior desired cooking temperatures from typically to little at least 200 ° C, in particular up to at least 250 ° C and preferably up to at least 300 ° C temperatures at least 300 ° C are generated. 30. The method according to any one of claims 27 to 29, in which in a pyrolysis mode for cleaning the muffle wall of residues or radiators and preferably also at least one from induction heating existing part of the muffle wall the induction heater is heated so that in the muffle interior to clean the muffle wall pyrolysis temperatures required by pyrolysis of typically up to at least 450 ° C, preferably up to at least 500 ° C, are generated.