DE102006041665A1 - Pan for heating objects, food and liquids comprises a peripherally closed side wall arranged on a base unit having a layer construction with an active layer that is partly electrically conductive and controls power consumption of the pan - Google Patents

Abstract

Pan (10) comprises a peripherally closed side wall (16) arranged on a base unit (12) having a layer construction (18) with an active layer (22) that is at least partly electrically conductive and controls the power consumption of the pan. Preferred Features: The active layer is less than about 500, especially 120 mu m thick and comprises at least iron, nickel, cobalt, chromium dioxide and/or gadolinium and at least aluminum, samarium, neodymium, yttrium, boron, dysprosium, holmium, erbium, copper and/or terbium. The pan has a lid.

Description

The The present invention relates to a cookware for heating objects Food, liquids and the like, with one arranged on a ground unit in a direction away from the ground unit, circumferentially closed Wall, wherein the bottom unit has a layer structure with respect to the Operation in conjunction with an induction hob active layer has, which is at least partially electrically conductive.

Induction hobs are widely known in the art. Inductive heating has expanding from purely industrial applications, especially in the field of heating food, for example in the gastronomy area, in the commercial kitchen area or even in the household area. Especially when used in the The aforementioned areas have some particularly advantageous properties inductive heating to carry. Thus, in contrast to conventional hotplates such as cast hotplates, radiant heaters and the like, the heat not in the cooking area itself, but directly generated in the pot bottom. Therefore, the induction hob is often used as a cold stove designated. It is only indirectly by the warming of the pot bottom heated. About that In addition, induction cookers are usually with a pot detection equipped, so energy is only released when a suitable cookware is recognized. This automatically achieves an increased safety aspect, because a pot-free induction cooker can not cause dangerous heat generation.

at many usual ones Induction cookers, it is necessary that the active layer the ground unit in which the heat produced in the cookware, must be magnetic. This is under with other reasons that a sufficient power generation effect in the active Layer already at comparatively low frequencies in the range of about greater than 20 kHz can be achieved. Newer types of induction cookers, however, can also frequencies far beyond create.

The special mode of operation of the induction heating principle makes it clear that respect the mode of operation of inductive heating the ground unit as important ingredient regarding the interactions with the induction cooker is. This applies to both the power consumption of the pot, the heat generation or the heat distribution in the ground unit. Modern cookware for inductive cooking are suitable, therefore, have a bottom unit with a layer structure which has both an active layer for interaction with the induction cooker as well as one about it arranged heat-conducting Layer for heat distribution in a substantially planar direction of the ground unit, that is parallel to the cooking surface, having.

by virtue of of the particular principle of effect, it is possible by a particular high power input into the ground unit an extraordinary rapid warming of the cookware, that is short cooking times to reach. At the same time allows the inductive Cooking reaction times as when cooking on a gas hob. By means of suitable controls for Induction cookers it is possible Sensitively control even very sensitive cooking or heating processes.

This But it can also cause problems when the power input is so high that it leads to a temperature gradient in the ground unit leads, their damage can result. Although the induction cookers are in the Usually equipped with temperature sensors, but these are not design-related able to reach the high with the induction hob Temperature change speeds to follow. So there is a danger that just in the Ankochphase the ground unit overheats due to excessive power input and / or damaged is where the temperature sensor is not due to its thermal inertia can protect. A possibility would Although it was to reduce the temperature response, but that would cause that a significant advantage of the induction cooker over conventional Hotplates lost, namely the short cooking time. The cooking times are at least comparable to the cooking times at appropriate Gas-fired cooking, can however about it also considerably shortened become.

It should also be noted that cookware, for example, pots, pans and the like, generally have standard diameter with respect to the bottom of the pot. Adapted to this, the diameters of hotplates are standardized. As a standard diameter, for example, the cooking area diameters 145 mm, 180 mm and 210 mm are provided for household use. The risk of overuse of a ground unit increases, inter alia, when a cookware is operated on a much larger cooking area for which it is not designed. The larger cooking area usually has an increased power input result. By contrast, is due to the smaller cookware and a smaller heat sink. Such a constellation proves to be in terms of normal operation as a particularly unfavorable case, especially because it ge from the consumer wishes is that a cookware, which is intended for a particular cooking point diameter, even at the next larger cooking area can be operated.

Furthermore would it be desirable if the sensitive control characteristics of inductive cooking better could be harnessed.

The The present invention has now taken on the task, a generic device in such a way that the risk of damaging the Ground unit due to overload can be reduced. Furthermore, the usability of the inductive Cooking to be improved.

When solution is proposed with the present invention that the energy consumption of the cookware is controllable by means of the active layer.

for the first time is proposed with the invention that the active layer influence on the power input into the cookware during the cooking and / or heating process can take. This can be achieved, for example, by the fact that the active layer significantly different from the rest of the ground unit having thermal expansion coefficient, for example with increasing temperature to a growing bulge of the Ground unit leads. In this way, a mean distance between ground unit and induction cooker are enlarged, whereby their inductive coupling and consequently also the energy consumption of the cookware can be reduced. The bulge can be advantageously provided such that the ground unit still with an annular Area rests on the hob to a stable state of To allow cookware. But it can also be provided that from a predetermined temperature the electrical conductivity the ground unit, in particular the active layer, significantly decreases, so that the inductive coupling can also decrease. In any Case attacks while the intended use the active layer in the inductive coupling directly and / or indirectly and in this way can influence the energy intake of the Take cookware. Preferably, however, this is done by that the conductivity the active layer when passing through the temperature limit or of the temperature range increases, so that due to the transformative Effects generated eddy current in the soil unit due to the underlying Ohm's law less heat output generated. This can be achieved, for example, by the fact that the specific electrical resistance of the active layer having negative temperature coefficients. Such substances are For example, in the field of semiconductors known.

Especially Preferably, the effect is reversible, so that falls below the temperature limit or passing through the temperature limit range in the direction of lower temperatures intended Performance in the device can be achieved again. The invention This can prevent the ground unit due to too high power input is thermally overloaded and damage takes. A higher one reliability and a higher one Safety can be achieved. But it can also cookware with a for a custom application customized behavior are produced so for example, a milk pot, the bottom of the pot or Ground unit 80 ° C does not exceed or similar. But multiple effects can be achieved, such as a reduction in the energy consumption of the cookware when it reaches or passing through a predeterminable temperature range in conjunction with another significant reduction or shutdown the energy absorption when reaching an upper temperature limit. For further Applications can also be provided that the effect of active Layer has a hysteresis, for example, with respect to the Energy consumption switched off cookware with falling temperature not to turn it on again. This allows, for example Cooking and / or cooking automatically control or stop. The active layer can do this, for example, from two or more sublayers be formed, which have adapted different properties. So can achieved in addition to individual effects and the aforementioned combination effects become.

In an advantageous development, it is proposed that the active layer is magnetically permeable. For example, the material of the active layer is designed such that it does not reach saturation during normal operation. Accordingly, during normal operation, a reliable power input into the ground unit can be achieved. In addition, the magnetic layer allows the floor unit to be operated with older type induction cookers operated in the lower frequency range as stated above. Due to the magnetic permeability, the current-carrying layer is concentrated on a very thin layer, so that it is acted upon by a high current density. Given a specific electrical resistance, a high power input can be achieved. In this embodiment, the temperature limit and / or the temperature limit range can be formed by the Curie temperature, the exceeding of which leads to the fact that the active layer from ferromagnetic behavior to paramagnetic behavior. As a result of this behavior, the cross-section of the current-carrying layer within the active layer increases, so that less power is generated while the current in the layer is assumed to be constant.

In a particularly advantageous embodiment can be provided that the power input can be reduced to zero. So can For example, the effect can be used that a pot detection the induction cooker this when reaching the Curie temperature off. In a simple way, a reliable protective effect can be improved.

It it is further proposed that the active layer at least one A substance from the group consisting of iron, nickel, cobalt, chromium dioxide and / or Has gadolinium. With these substances, in addition to an already existing electrical conductivity achieved a magnetic permeability become. About that In addition, as needed, the substance may be selected for its Curie temperature. Naturally can also mixtures of these substances with each other or with others Be provided substances.

Furthermore It is proposed that the active layer at least one substance from the group consisting of aluminum, samarium, neodymium, yttrium, Boron, dysprosium, holmium, erbium, copper and / or therbium. These substances are preferably suitable for the properties of the active Layer in terms of their electrical conductivity and / or in terms their magnetic permeability to influence. Special attention is paid to the influence To judge the Curie temperature, which allows, if appropriate Selection of material combinations the Curie temperature in wide Specify areas as needed. This can cause the temperature limit and / or the temperature limit range can be set as needed.

With an advantageous development is proposed that the active Layer has a layer thickness of less than about 500 microns, especially less than 120 μm, having. Especially when the active layer is magnetically permeable, the effective range of the eddy current can be limited to this range become. Costs as well as the thickness of the ground unit can be reduced become. In particular, it is proposed that the layer thickness less as 120 μm is. In suitably selected magnetic permeability already this layer thickness can be sufficient to the intended function to reach the active layer. Costs can be further reduced. About that in addition, are so thin Layers of a variety of coating processes accessible, so that cost-effective Production at high quality can be achieved.

Around the ground unit during the intended use To protect against mechanical effects, it is suggested that this boilerside side has a coating. The coating For example, in the form of a paint or an additional Protective layer of the ground unit to be formed. The protective layer can For example, a stainless steel layer, an enamel layer or the like be. Naturally The coating can also be made of a suitably resistant plastic or a composite material. In addition, can also suitable ceramic materials are used.

In An advantageous development is proposed that the layer structure a heat-conducting Layer has. The heat-conducting Layer can promote heat balance within the ground unit, so that the temperature on the side facing away from the cooking of the Ground unit is homogenized. This proves in particular when applied to cookware, where a substantial homogeneous temperature in the cooking area of the soil unit is desired, as advantageous. Thermal inhomogeneities due to the inductive heating principle can be reduced.

According to one Another advantageous proposal of the invention is the ground unit essentially flat. So the soil unit can be part of it a conventional cookware, such as a pot, a pan or the like. The ground unit is thus suitable, a Coupling to the hob to produce. Preferably, ground unit formed adapted to the standard diameter and the surface qualities. This allows a needs-based coupling the device to the cooking area, which also in terms of their Dimensions are standardized, can be achieved. In addition, of course, provided be that the device also kesselelförmig or cupped or the like is formed. This is for applications, for example as a wok possible. Naturally can Also other design aspects come to fruition, the corresponding one Justify adaptation of the ground unit can. A variety of design options can be achieved.

In addition, it is proposed that the wall has a handle. This allows a user to use the cookware properly and safely. For example, it can be achieved that this can be handled safely despite a high temperature. Preferably, the handle is formed of an electrically non-conductive material, so that accidental inductive heating can be avoided. The handle can be formed for example of a plastic, a ceramic material or a composite material.

Farther It is proposed that the device has a lid. this makes possible it, the heating process in terms of efficiency. So can the heat loss be reduced. Also, the lid can handle a corresponding exhibit. For example, it can be made of glass, plastic, ceramic or the like may be formed. An electrically non-conductive lid has the advantage that it does not when filing on an induction hob accidentally be recognized as a pot. The security can be further improved.

Further advantages and features will be apparent from the following description of an embodiment. Substantially identical components are designated by the same reference numerals. Furthermore, with respect to the same features and functions to the description of the embodiment in 1 directed. The drawings are schematic drawings and are merely illustrative of the following embodiment. Show it:

1 a sectional view of a pot according to the invention on an induction hob,

2 a soil unit of the pot 1 in an enlarged view likewise in sectional view,

3 a characteristic field for the relative magnetic permeability of the material of the active layer and

4 a characteristic field for the operating range of the active layer.

In 1 is one on an induction cooker 20 set up pot 10 shown in sectional view. The pot 10 has a ground unit 12 on, in one direction from the ground unit 12 away a circumferentially closed wall 16 stainless steel stretches. In an upper area of the wall 16 is a handle 34 attached. The ground unit 12 has a layer structure 18 on, which consists in the present case of three layers, and from below first an enamel layer 28 , disposed above an active layer 22 and above that an aluminum layer 32 , The aluminum layer 32 also forms the inside 30 of the pot 10 , The pot 10 can also be provided on the inside with a further coating, such as a Teflon coating or the like, in order to use advantages in use during normal operation can.

The induction cooker 20 is below a glass plate 40 arranged a cooking field not shown. It includes a coil 42 , Which is presently designed as Archimedean coil having spirally arranged side by side turns. Centric is in the coil 42 a temperature sensor 36 arranged. In addition, between the glass plate 40 and the coil 42 a thermal insulation can be arranged, and below the coil 42 a magnetic conclusion, for example in the form of ferrites or the like. The sink 42 as well as the temperature sensor 46 are connected to a converter, also not shown, which is controllable by means of known control means such as knobs or the like in terms of performance, operating time or the like.

In 1 is represented by a so-called counting arrow system, such as a current flow in the coil 42 a magnetic field 44 generated. The magnetic field 44 penetrates upwards the electrically non-conductive glass plate 40 as well as the enamel layer 28 of the pot 10 , which is also electrically non-conductive. The magnetic field 44 penetrates into the active layer 22 and here leads to eddy currents, which are not shown for clarity. It should be noted that it is an alternating magnetic field having a frequency of about 25 kHz. Due to the electrical and magnetic properties of the active layer 22 The eddy current generated in this layer is concentrated on a cooking surface side thin layer. The thickness of this layer depends, among other things, on the relative magnetic permeability, decreasing as it increases. The concentration of the eddy current on a very thin current-carrying cross section leads to a resistive heating of the active layer due to the specific electrical resistance of the active layer 22 , This is the thermal energy generated by heat conduction or and / or thermal contact to the aluminum layer 32 from which these radially distributed and to the inside 30 of the pot 10 forwards. Here, the heat is available for heating food or food.

2 shows an enlarged view of the layer structure, wherein it is apparent that the enamel layer 28 around the ground unit 12 along the wall 16 is extended and in this way the ground unit 12 completely surrounds to the outside. This is the ground unit 12 protected against external influences.

To protect the induction cooker 20 itself and for safety reasons is the temperature sensor 46 intended. This sensor becomes the induction hob 20 protected against thermal overload.

The present is the temperature sensor 46 set for a maximum temperature of 400 ° C. The induction cooker 20 has a standardized nominal diameter of 210 mm. It also has a rated output of 3 kW.

In the present embodiment, the ground unit 12 of the pot 10 also a nominal diameter of 210 mm. The thickness of the aluminum layer 32 is 3.5 mm. The thickness of the active layer 22 is 0.5 mm. The thickness of the coating 28 corresponds to commercial coating thicknesses of an enamel layer in the range of about <0.5 mm.

The active layer 22 has an alloy of the materials neodymium, iron and boron, which has a Curie temperature of about 310 ° C. This temperature is below the temperature at which the induction hob 20 is switched off.

By Addition of other substances, the Curie temperature point in almost be set in any way.

A characteristic curve for the relative magnetic permeability of the active layer 22 is in 3 shown. The relative magnetic permeability μ _r 38 is plotted on the ordinate, whereas the temperature T is indicated on the abscissa. T _R corresponds to the room temperature 50 , T _C corresponds to the Curie temperature 24 , The curve 52 represents the course of the relative magnetic permeability μ _r over the temperature T. It can be seen that when the Curie temperature is reached 24 the value of the relative magnetic permeability μ _r decreases sharply.

4 shows the operating behavior of the pot 10 during normal operation. On the ordinate here is the performance 26 indicated by the identifier P The abscissa indicates the temperature T as before. P _max denotes the maximum power of the induction hob 20 , which in the present case is 3 kW. It can be seen that the power consumption of the pot 10 up to the Curie temperature 24 essentially corresponds to the rated power. Of course, a smaller power can also be set, as can be seen from the hatching of the permissible operating range 48 results. In general, however, the power values are not continuous, but only discretely adjustable.

Upon reaching the Curie temperature 24 the relative magnetic permeability decreases sharply. This causes the current-carrying layer in the active layer 22 increases significantly, which means that the current is distributed over a larger electrically conductive layer and therefore generates less heat. The power consumption decreases drastically, like out 4 is clearly visible. It should be noted that the Curie temperature is below the protection temperature at which the hotplate is switched off.

As a rule, the induction hob has 20 via a limitation of the apparent power output from the induction converter, not shown. The aforementioned effect leads to the reactive power component in the apparent power considerably increasing from an inverter perspective. As a rule, the converter will then counteract this and at the same time reduce the power output. If a predefinable limit value is exceeded, the inverter is automatically switched off. In this way it can be achieved that the pot 10 can only be operated up to a predeterminable temperature.

This Effect can also be used, for example, cookware for special Produce applications that are optimal for the intended application are adjusted. For example, could such a cookware to be a milk pot in which the active Layer is adjusted so that the soil temperature does not exceed 80 ° C. As is known, Milk begins to burn at a temperature above 80 ° C. In this way For example, the burning of milk during heating can be avoided become.

Further Application examples can be realized, such as cookware especially suitable for frying applications, Boiling water or the like.

The Embodiment illustrated in the figures is for explanation only of the invention and is for these are not restrictive. So can Naturally the values due to the given material properties of the active Layer vary.

10

pot

12

ground unit

14

direction

16

pot wall

18

layer structure

20

Induction cooking

22

active layer

24

Curie temperature

26

power

28

enamel layer

30

inside

32

aluminum layer

34

Handle

36

temperature

38

relative magnetic permeability

40

glass plate

42

Kitchen sink

44

magnetic alternating field

46

temperature sensor

48

operating range

50

room temperature

52

curve

Claims (11)

Cookware ( 10 ) for heating objects, food, liquids and the like, with one on a floor unit ( 12 ), in one direction ( 14 ) from the ground unit ( 12 ) extending away, circumferentially closed wall ( 16 ), the ground unit ( 12 ) a layer structure ( 18 ) with respect to operation in connection with an induction cooker ( 20 ) active layer ( 22 ), which is at least partially electrically conductive, characterized in that the energy consumption of the cookware ( 10 ) by means of the active layer ( 22 ) is controllable. Cookware according to claim 1, characterized in that the active layer ( 22 ) a temperature limit ( 24 ) and / or has a temperature limit range, beyond which the energy consumption can be reduced. Cookware according to claim 1 or 2, characterized in that the active layer ( 22 ) is magnetically permeable. Cookware according to one of claims 1 to 3, characterized in that the active layer ( 22 ) has at least one substance from the group consisting of iron, nickel, cobalt, chromium dioxide and / or gadolinium. Cookware according to one of claims 1 to 4, characterized in that the active layer ( 22 ) has at least one substance from the group consisting of aluminum, samarium, neodymium, yttrium, boron, dysprosium, holmium, erbium, copper and / or terbium. Cookware according to one of claims 1 to 5, characterized in that the active layer ( 22 ) has a layer thickness of less than about 500 microns, in particular less than 120 microns. Cookware according to one of claims 1 to 6, characterized in that the layer structure ( 18 ) Heizstellenseitig a coating ( 28 ) having. Cookware according to one of claims 1 to 7, characterized in that the layer structure ( 18 ) a thermally conductive layer ( 32 ) having. Cookware according to one of claims 1 to 8, characterized in that the ground unit ( 12 ) is substantially planar. Cookware according to one of claims 1 to 9, characterized in that the wall ( 16 ) a handle ( 34 ) having. Cookware according to one of claims 1 to 10, characterized by a lid.