EP3177107A1 - Method for operating an induction cooking hob - Google Patents

Abstract

In a method of operating an induction hob with a controller and a hob with an induction heating coil, a relationship is stored in the controller between a cooking vessel temperature and a heating power of the induction heating coil as area output, which causes a constant cooking vessel temperature during continuous operation. By monitoring whether the cooking vessel temperature remains constant, rises or falls after a heating time with high heating power when setting a first relatively small heating power, a target temperature corresponding to the first relatively small heating power can be set for frying operations.

Description

Field of application and state of the art

The invention relates to a method for operating an induction hob, wherein a temperature setting is to be effected or a certain cooking vessel temperature is reached or set as the target temperature and kept constant. A special feature of the method is that no temperature measuring devices are used, which detect the absolute cooking vessel temperature. The cooking vessel temperature is determined only indirectly via other properties of the cooking vessel, such as temperature-dependent permeability change. Only a relative temperature change, but no absolute temperature can be detected. The measuring method is known from the EP 2330866 A2 ,

It is from the EP 2574144 A2 It is known to be able to keep a temperature for frying, which is generally slightly above 200 ° C, constant. In this case, an achieved target temperature must be confirmed, so to speak.

Task and solution

The invention has for its object to provide an aforementioned method, can be avoided with the problems of the prior art and it is in particular possible that in an advantageous manner, preferably in an induction hob, a predetermined or input target temperature for a Cooking vessel can be controlled and held automatically so to speak.

This object is achieved by a method having the features of claim 1. Advantageous and preferred embodiments of the invention are the subject of the other claims and are explained in more detail below. The wording of the claims is incorporated herein by express reference.

An induction hob has a controller and a hotplate with at least one induction heating coil. In the controller is advantageously stored a relationship between a cooking vessel temperature and a heating power of the induction heating coil as area performance or area density, which adjusts the steady state or steady state or in continuous operation said and desired certain cooking vessel temperature or results.

It is envisaged that in the process for operating this induction hob, a cooking vessel is placed on the hob and is inductively heated by the induction heating coil. Before a heating process of the cooking vessel, a target temperature for the cooking vessel or an application case implicit in a specific target temperature is entered into the control of the induction hob, for example as a "roast steak". At the beginning of the heating process, the cooking vessel is heated for a first heating time with a first relatively large heating power as area performance, so as to cause the fastest possible increase in temperature to quickly get close to the target temperature.

After the first heat-up time, the heating power of the induction heating coil is reduced to a first relatively small heat output that would permanently lead to the target temperature. This may correspond to the aforementioned relationship between cooking vessel temperature and heating power, if this is stored. This first small heating power is significantly smaller than the aforementioned large heating power, preferably it is only about 1% to 20% or only up to 10%. Then it is checked, advantageously after a short check-time of one second to thirty seconds, whether at the first relatively low heat output, the cooking vessel temperature remains constant, rises or falls. For the method used for this purpose, more will be explained below.

In a first case, the cooking vessel temperature remains constant when heating the cooking vessel for the short check time with the first relatively small heating power and corresponds to the target temperature, advantageously at least after the aforementioned short check time of a few seconds. Then the target temperature is considered reached and is preferably maintained, for example, then the actual roasting process can begin. To maintain the frying temperature advantageously a continuous control or a two-point control can be used, as they are state of the art. In general, the temperature can be kept approximately constant, possibly with a slight increase in heating power because of the food to be fried.

In a further case that the setting of the first, relatively small heating power, the cooking vessel temperature does not reach the target temperature or no constant temperature within the short check time or after the short check time, the relatively small heating power from the controller adapted or changed their size. So you can try to find a different heating power, which leads to a constant temperature during the short Verification time. This other heating power is advantageously still a relatively small heating power. This can also be used to even a temperature value to determine which is currently present in order to be able to proceed from the target temperature targeted or faster.

Preferably, after sufficiently accurate finding of the corresponding correlation of heating power and cooking vessel temperature, the controller considers the heating process to be completed, cooking or frying or cooking is continued. This is advantageously signaled to an operator, possibly also further process steps can be initiated.

In an embodiment of the invention increases in a further case as a second case when heating the cooking vessel with the first relatively small heating power, the cooking vessel temperature continues to after the short Verification time. It may sometimes come first to a brief drop in the signal used for temperature determination, but this does not bother. Then, the cooking vessel for a Zwischenheiz time again heated with an intermediate heating power more or further, since the cooking vessel temperature is still below the target temperature, so that its temperature rises again. Advantageously, the intermediate heating power is greater than the first relatively small heating power, but can also be the same size. Then, after an intermediate heating time, by re-setting the relatively small heating power, it is checked whether the cooking vessel temperature still rises or remains constant during a short checking time, possibly after a short checking time of one second to a half or one minute. If the cooking vessel temperature then remains constant, not only is a constant temperature set, but the first case applies, namely that the target temperature is reached.

Advantageously, in the event that the cooking vessel temperature still rises after the Zwischenheiz-time and after the short Verification time when heating with the first relatively small heating power, again below the target temperature cooking vessel temperature is detected. Then the cooking vessel can be heated once more with an intermediate heating power for a Zwischenheiz-time. After the intermediate heating time can then be checked again by adjusting the relatively small heating power for a short Verification time, whether the cooking vessel temperature after this short Verification time still rises or remains constant, while maintaining the cooking vessel temperature remains the first case of reaching the target temperature applies.

In a third case, when the cooking vessel temperature continues to drop even after the checking time has elapsed when the cooking vessel with the first relatively low heating power is heated, a cooking vessel temperature above the target temperature is determined. Then, the target temperature can be achieved in different ways, which will be explained in more detail becomes. In the simplest way is simply heated with the relatively small heating power and after some time or a few minutes, the target temperature will have set. Alternatively, the heating operation may be suspended for a short time, for example, 5 seconds to 30 seconds or one minute.

Although the invention core includes only the first case and the other case, but also the second and even the third case are advantageously implemented together in a control process.

Thus, with the invention, in particular in their aforementioned optional embodiments, especially the realization be realized that in a practical method, a certain heat output as area performance leads to a certain final temperature or permanently held cooking vessel temperature, and largely independent of what is used for a cooking vessel. This applies mainly in the range between 150 ° C and 250 ° C, especially 200 ° C to 250 ° C, which is advantageous for frying operations. It should be noted that the aforementioned relationship between cooking vessel temperature and heat output as area performance, so to speak, requires the information about which power the induction heating coil or several induction heating coils connected together in a cooking position produce, ie is introduced into the cooking vessel. Furthermore, the approximate area of the cooking vessel or the cooking vessel bottom is needed so that just the area performance can be determined. However, since hotplates are usually designed for specific sizes of cooking vessels, this is indicated in particular by a mark on the top side of a hob plate, an approximately expected range of the cooking vessel size is known for a defined hotplate. Furthermore, it is also possible in particular to determine an overlap of the induction heating coil by the cooking vessel by monitoring operating parameters of the induction heating coil, in particular an efficiency of the induction heating coil. With a known size of the induction heating coil can then be closed in about the approximate area of the cooking vessel or the cooking vessel bottom. This is already known to the person skilled in the art from another context. The method assumes that there is no food in the dishes during the heating process and the inventive determination of the cooking vessel temperature. This would falsify the above-described adjustment of the temperature. However, the corruption would be so significant that the controller can detect this case and display it to an operator.

The input of the target temperature in the controller can be done either by an operator by means of controls. Alternatively, the input can be through an automatic cooking program take place, which runs in the control itself. It is important that a target temperature is given.

The said first heating-up time can be relatively short. In particular, it is attempted, since relatively high target temperatures are to be approached, to choose the first relatively large heating power very large, advantageously maximally large. Thus it may be 3 W / cm ² to 12 or even 14 W / cm ² , in particular 6 W / cm ² to 10 W / cm ² . Then this first heating-up time can be between one minute and five minutes or even eight minutes. It can also be specified for a particular hob or induction heating coil depending on their size and thus an expected cooking vessel from stored in a table in the control experience, for example, two minutes for small induction heating coils, five minutes for medium induction heating coils and eight minutes for large induction heating coils , These empirical values are based on the fact that when setting up a cooking vessel, in particular a pan, with the appropriate size, this time elapses until at the first relatively large heat output a temperature between 200 ° C and 250 ° C is reached. Alternatively, the heat-up time may also be calculated theoretically via harness heat capacity, area power density, and desired temperature increase in the controller.

The first relatively small heat output can be significantly lower than the first large heat output. In particular, it may be between 0.3 W / cm ² and 2 W / cm ² . It is particularly advantageous between 0.6 W / cm ² and 0.8 W / cm ² . In the context of the invention it has been found that with such relatively small heating cooking vessel temperatures between 200 ° C and 250 ° C can be maintained in the long term. Of course, such cooking vessel temperatures could be achieved only with setting such a relatively small heat output as area performance, but this would then predictably take a long time.

Advantageously, the first relatively small heating power is set for at least one second to 30 seconds or even one minute or introduced into the cooking vessel, so an aforementioned short time as a check-time, before it is expected that the cooking vessel temperature remains constant. The temperature compensation processes usually take a few seconds, especially in the aforementioned first or second case, until the first small heating power defines the energy input. Advantageously, the check-time is 5 seconds to 20 seconds.

An aforementioned intermediate heating time may be in the range similar to the checking time, for example between 5 seconds and 60 seconds, preferably between 10 seconds and 20 seconds. Although the intermediate heating power should be advantageously greater than the first relatively small heat output, can be much larger, but it does not have to. The advantage of choosing a slightly larger intermediate heating power is that when the cooking vessel temperature is obviously still below the target temperature, reaching the target temperature can be faster. Thus, the intermediate heating power between 1 W / cm ² and 12 W / cm ² , in particular between 1.5 W / cm ² and 8 W / cm ² , or it may be 5% to 100% greater than the first relatively low heat output.

In an advantageous embodiment of the invention can indeed be provided that in the third case, the cooking vessel is simply heated after detecting the too high cooking vessel temperature with an intermediate heating power as described above. If then the cooking vessel temperature is constant, it corresponds to the target temperature. However, this results in a somewhat slower drop in the cooking vessel temperature, which means that the determination of the particular cooking vessel temperature as actual frying temperature can take place later, especially after several minutes, and thus the operator can start the frying process only after a time delay.

Alternatively and faster can be heated with a second intermediate heating power, which may then be slightly above the first relatively small heating power, advantageously between 105% and 200% thereof. It is waited until this second intermediate heating power leads to a constant cooking vessel temperature. Then the cooking vessel temperature would be determined from the relationship between cooking vessel temperature and heating power stored in the control. So the controller can not only detect that the cooking vessel temperature is above the target temperature, but also how much it is above. Although the cooking vessel temperature in this case is not at the target temperature, but above, the controller can determine their absolute value again based on the second intermediate heating power at a constant cooking vessel temperature. Then the heating power can be reduced again. Either it can be turned off for a short time to cause a faster drop in temperature towards the target temperature. Since the cooking vessel temperature and the target temperature are known, the controller can estimate this on the basis of stored empirical values. Then, the first relatively small heating power can be set, which leads to the target temperature. Alternatively, the operator can also be given the signal to start the frying process. The inserted food will then cool the cooking vessel to the target temperature relatively quickly. The controller can then take the actually desired target temperature for the temperature control already described, even if it was not previously set explicitly.

Checking the cooking vessel temperature or checking whether the cooking vessel temperature changes or whether it remains constant, is advantageously carried out via a sensorless process or without dedicated temperature sensor. During the heating operation is detected on the basis of the vibration response to at least one induction heating coil, whether the temperature of the cooking vessel or the cooking vessel bottom changes over this induction heating coil or whether this temperature increases. Thus, a temperature gradient of the cooking vessel can be detected by the induction heating coil, which is preferably done according to a method as described in US Pat EP 2330866 A2 is described. Its content is hereby incorporated in this regard by express reference to the content of the present application. If this determination of the oscillation response takes place only periodically, it should be advantageous every 0.01 milliseconds to 1 second, advantageously up to 1 millisecond. In general, the vibration response of an induction heating coil can be understood to mean the evaluation of the change in resonant circuit parameters due to changes in the temperature of the cooking vessel or cooking vessel bottom, in particular the changing permeability. Preferably, the vibration response when operating multiple induction heating coils at the cooking area or for this cooking vessel can be detected at each induction heating coil.

This method advantageously comprises the steps: generating an intermediate circuit voltage at least temporarily as a function of a single-phase or multi-phase, in particular three-phase, mains alternating voltage; Generating a high-frequency drive voltage or a drive current from the intermediate circuit voltage, for example with a frequency in a range of 20 kHz to 70 kHz; and applying a resonant circuit comprising the induction heating coil with the drive voltage or the drive current. In this way, conventionally, an inductive heating of the cooking vessel. For temperature measurement, the following steps are then carried out: Generating the DC link voltage during predetermined periods of time, in particular periodically, with a constant voltage level, wherein during the periods preferably the DC link voltage is generated independently of the AC mains voltage; Generating the driving voltage during the predetermined periods of time such that the resonant circuit oscillates substantially unattenuated with its natural resonant frequency; Measuring at least one vibration parameter of the vibration during the predetermined time periods; and evaluating the at least one measured vibration parameter to determine the temperature. Since the intermediate circuit voltage is kept constant during the temperature measurement, signal influences due to a variable DC link voltage can be eliminated, whereby a reliable and interference-free temperature determination or determination of a temperature change is made possible.

In one development, the method comprises the steps of: determining zero crossings of the mains alternating voltage and selecting the time segments in the region of the zero crossings. In the range of zero crossings with single-phase AC mains voltage, the DC link voltage usually decreases sharply. The constant voltage level is preferably selected such that it is greater than the voltage level which usually sets in the region of the zero crossings, so that the intermediate circuit voltage is clamped to the constant voltage level in the region of the zero crossings. Then prevail in the zero crossings constant voltage conditions that allow reliable temperature measurement. So here no additional temperature sensors are needed, even if they could be present.

In an embodiment of the invention, it is possible that not only a single induction heating coil is provided at the cooking point for the cooking vessel, but several. Here, however, applies in principle the corresponding, then the above-mentioned performance values are just related to all Induktionsheizspulen that are present at the hob and are used to heat the cooking vessel. Their power or area performance or heating power is then considered together as described above for temperature measurement.

In an advantageous embodiment of the invention, it is possible to detect and monitor the amount of energy introduced or the heating power of the induction heating coil over time. Even so, estimates of temperatures reached can be made. Based on this, the controller can slightly vary the heating powers or, above all, set the first heating time, the checking time, the intermediate heating time or off times. Although the above check times in the different cases may be the same or similar, they do not have to. They can also differ by a factor of 1 to 5.

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-combination in one embodiment of the invention and in other areas be realized and advantageous and protectable Represent embodiments for which protection is claimed here. The subdivision of the application into individual sections as well as intermediate headings does not restrict the general validity of the statements made thereunder.

Brief description of the drawings

Fig. 1

für mehrere verschiedene Kochgefäße ein Verlauf der stabil auf Dauer gehaltenen Kochgefäßtemperatur abhängig von einer Flächenleistung,

Fig. 2

eine Seitenansicht eines Induktionskochfelds mit einer Induktionsheizspule und aufgesetztem Kochgefäß,

Fig. 3 bis 6

verschiedene Verläufe der Kochgefäßtemperatur und der Flächenleistung über der Zeit in verschiedenen Fällen der Ansteuerung für leere Kochgefäße, also ohne Zugabe eines Lebensmittels.

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

Fig. 1

for several different cooking vessels, a course of the cooking vessel temperature, which is kept stable in the long term, depending on a surface output,

Fig. 2

a side view of an induction hob with an induction heating coil and attached cooking vessel,

Fig. 3 to 6

different courses of the cooking vessel temperature and the area performance over time in different cases of control for empty cooking vessels, ie without the addition of food.

Detailed description of the embodiments

In the Fig. 1 is recorded as empirically determined values for four different cooking vessels indicate the relationship, as the cooking vessel temperature reached or set depends on the corresponding area performance. From this it can be seen that, on the one hand, the relationship is reasonably linear, that is, it is very easy to determine mathematically. On the other hand, the temperatures are only a maximum of 30 ° C to 35 ° C apart for a given area performance. Thus, Q * / A can be determined relatively precisely at a specific area performance, which cooking vessel temperature adjusts to a cooking vessel after a certain longer period of operation, for example 10 minutes to 30 minutes.

In the Fig. 2 an induction hob 11 is shown with a hob plate 12, on which a cooking point 13 is formed. Under the hob plate 12, an induction heating coil 15 is arranged, which defines the hotplate 13 and also heated. This could also consist of several induction heating coils, which plays no role for the invention. The induction heating coil 15 is powered and driven by a controller 17, and the controller 17 can monitor the power fed into the induction heating coil 15. Furthermore, the controller 17 has a memory, not shown, in which, so to speak, accordingly Fig. 1 a relationship is stored between cooking vessel temperature and area performance. In this case, either the computational relationships can be stored when the temperature curves off Fig. 1 be considered as straight lines approximated. Alternatively, with sufficiently good resolution, temperature values can be stored for each incrementally increasing area power.

In an expanded embodiment of the invention, it is possible that this is stored in the controller 17 for several cooking vessels, so that the controller 17 knows, so to speak, exactly which of the four or more curves from the Fig. 1 to be used in each case. Alternatively, certain parameters could be entered into the controller 17 by an operator or programmed from the outside, which, detached from the actual existing cooking vessel, the controller 17 tell which cooking vessel is now used or which of the stored curves applies. Under certain circumstances, the controller 17 can then also recognize the size range in which a cooking vessel 13 is placed above the cooking vessel.

Of course, the area of the induction heating coil 15 is known. Advantageously, however, said surface power is not related to the surface of the induction heating coil 15, but rather to the surface of the cooking vessel 19. Suitable for the cooking area 13, the surface or the bottom surface of the cooking vessel 19 will move in a relatively narrow range, since matching cooking vessels within certain diameter classes usually have only up to 3 cm diameter variation. Clearly too large or too small cooking vessels are rarely placed, this could also be detected by the controller 17 and signaled to an operator as a mistake.

In the Fig. 3 is shown how at time t = 0 with a large heating power, here 7 W / cm ² , which is constant, is heated. This heating lasts until the time t1 as heating-up time, which can be predefined.

Before or from a target person or an automatic control odgl. a target temperature of 200 ° C has been entered. This temperature should be permanently on the cooking vessel 19, which is here a pan held. This temperature is advantageous for the top of the cooking vessel bottom, ie where food, such as a steak to be simmered, comes into contact with the cooking vessel 19. For the cooking vessel 19, the top curve from the Fig. 1 ,

After the heating time t1, the heating power is greatly reduced and set to 0.68 W / cm ² . This corresponds to the Fig. 1 the top curve or at this area performance is maintained permanently the temperature of 200 ° C.

From the Fig. 3 According to the first case, it can be seen that the temperature T drops only slightly and then becomes relatively fast, for example in 5 seconds to 20 or 30 seconds as the adaptation time. Both the low temperature drop and the constant Temperature can be determined by an aforementioned method or according to the EP 2330866 A2 or the EP 2574144 A2 be recognized.

Since the cooking vessel temperature remains constant at 0.68 W / cm ² at the area output, this temperature remains constant in accordance with the Fig. 1 set to 200 ° C and thus can be kept permanently.

In the next case according to the Fig. 4 is heated until the time t1 'as a heating-up time with a large area power of 7 W / cm ² , the temperature T increases again. At time t1 ', the power is reduced to 0.68 W / cm ^2, corresponding to a target temperature of 200 ° C, which is also desired here. The controller 17 or the temperature detection can now determine that at this now set area performance, the cooking vessel temperature is still rising, although this is probably weaker than before. This means that the cooking vessel temperature at the time t2 'is still below the target temperature of 200 ° C. The time between t1 'and t2' is the aforementioned check time. Therefore, at the time t2 ', which is, for example, a few seconds to one or two minutes after the time t1', again set a much larger and in particular the previously set large power of 7 W / cm ² . Then the temperature T rises again stronger. After a certain period of time as an intermediate heating time between t2 'and t3', for example a few seconds to one minute to three minutes, the power is reduced again to the target temperature, ie back to the first small heating power of 0.68 W / cm ² , Now the temperature detection recognizes that the cooking vessel temperature T only slightly decreases and then relatively quickly, for example, within a minute or even just a few seconds as adjustment time, only has a small decrease or is constant. Thus, it is again the case that with a surface output of 0.68 W / cm ^2, a constant cooking vessel temperature is reached. This must then be the target temperature 200 ° C accordingly Fig. 1 or as before to Fig. 3 described. The reheating with the higher heating power was required in this case, since the cooking vessel to reach the specific temperature requires more energy than assumed by the controller. The heat capacity of the cooking vessel thus deviated from the value stored in the control.

The second time or Zwischenheiz time with high heating power at the Fig. 4 between t2 'and t3' could also be done with a different area performance than the heating time up to the time t1 'However, the heating operations should run so relatively quickly, so that just an at least high area performance should be selected near the maximum area performance.

The case of overheating during the heating up time is in the Fig. 5 shown. Here, even at a desired target temperature of 200 ° C. for the heating time, until a time t 1 "with the high power of 7 W / cm ^{2 is} heated, whereupon the temperature T rises -Zeit with the low area performance of 0.68 W / cm ² heated, so for a few seconds to half a minute to see if the cooking vessel temperature is relatively quickly constant, which would be regarded as reaching the target temperature. However, the controller 17 determines, via the aforementioned temperature monitoring, that the cooking vessel temperature drops permanently even after the checking time has elapsed, even after one or two minutes as an adaptation time. This means that so a cooking vessel temperature is well above the target temperature prevails. Now either the power can be switched off completely for a short time, for example for 10 seconds to 30 seconds, to achieve rapid cooling to or near the target temperature. Then the operation could again use the small heating power of 0.68 W / cm ² , and experience has shown that the temperature would then be relatively fast and then just be the target temperature of 200 ° C.

Or another attempt is made to roughly determine the prevailing temperature. Therefore, a slightly larger heating power is fed as intermediate heating power for the intermediate heating time between t2 "and t3" in the induction heating coil 15, namely here the 0.8 W / cm ² . This sets relatively quickly a constant temperature, which according to the Fig. 1 is about 230 ° C. Thus, the controller 17 thus knows that the temperature is still about 30 ° C too high. Then, as previously described, it may either switch off the induction heating coil 15 completely for a short time for a somewhat faster cooling, for example for 10 seconds to 30 seconds, in which case the small heat output is again set to reach and maintain the target temperature. Alternatively, the areal power of 0.68 W / cm ² corresponding to the target temperature can be set from time t3 "so that the cooking vessel temperature T drops slightly more slowly to the target temperature, which is then finally reached and maintained Advantageously, for a subsequent addition of food to the temperature control, the measured value corresponding to 200 ° C is used as the setpoint and not the measured value corresponding to 230 ° C.

Fig. 6 shows a further advantageous embodiment of the method for defined reaching a certain cooking vessel temperature. If the constant steady-state temperature is not reached after a short period of time, regardless of whether the signal falls or rises, no discrete power levels are subsequently approached between t2 '' and t3 ''. Rather, a Setpoint value T _{S of} the temperature signal determined after a specified time, here at t2 '"with 230 ° C. The controller then controls, for example, by a proportional controller, which may also have integral or differential shares, to this setpoint T _S. t3 '"reaches a constant temperature relatively quickly, faster than would be possible with discrete temperature levels. According to Fig. 1 corresponds to a cooking vessel temperature of 230 ° C, a surface power of 0.8 W / cm ² . Therefore, the cooking vessel temperature of 230 ° C is maintained at this area power density. In this way, in turn, the corresponding correlation of power and constant temperature is found, the power is known, which allows a temperature determination and thus temperature setting. Now, based on known relationships by power reduction starting from the known temperature, the particular cooking vessel temperature of 200 ° C are approached, for example, with simultaneous insertion of the food.

Thus, it is possible with the invention, without absolute temperature measurement and only by relative temperature measurement, ie monitoring whether a temperature rises, drops or is constant, and a known relationship between temperature and permanently set area power density, a temperature control and the startup and holding a certain Allow temperature to a cooking vessel.

Furthermore, the invention is in favor of that in a steady state, ie a permanently prevailing state, a thermal resistance is connected in series to a parallel circuit as a radiation heat resistance and convection heat resistance. This results in just the in Fig. 1 recognizable context.

Thus, the invention uses an energy balance to solve the task initially posed. By looking for a steady state, ie a state without changing the cooking vessel temperature, the internal energy of the cooking vessel is kept constant. As a result, it is known that the energy introduced by the heating into the cooking vessel is completely released again, be it by convection, heat radiation or heat conduction into the hob surface. However, the introduced energy can be measured by the heating. Since the connection out Fig. 1 is known, can thus be concluded by measuring an energy per time or power, under certain conditions, to the absolute temperature.

Claims (15)

Method for operating an induction hob for defined reaching of a particular cooking vessel temperature, wherein the induction hob has a control and a cooking point with at least one induction heating coil, with the steps: - a cooking vessel is placed on the hob and is inductively heated by the induction heating coil, - before a heating process of a cooking vessel, a target temperature for the cooking vessel or a specific target temperature implicit application is entered into the control of the induction hob, - At the beginning of the heating process, the cooking vessel is heated for a first heating time with a first relatively large heating power as area performance, after the first heat-up time, the heating power of the induction heating coil is reduced to a first relatively small heat output that would permanently lead to the target temperature, it is checked whether the cooking vessel temperature remains constant, rises or falls after a short check time at the first relatively low heat output, wherein, in a first case, when the cooking vessel is heated at the first relatively low heating power after the short checking time, the cooking vessel temperature remains constant and corresponds to the target temperature, the target temperature is reached, in another case that, by setting the first, relatively small heating power, the cooking vessel temperature has not reached the target temperature after the short checking time, the relatively small heating power is adjusted by the controller in order to find a heating power, which leads to a constant temperature during the short test time. A method according to claim 1, characterized in that after sufficiently accurate finding the corresponding correlation of heating power and cooking vessel temperature, the control considers the heating process as completed and signals this to an operator and / or initiates further process steps. A method according to claim 1 or 2, characterized in that in a further case as a second case when heating the cooking vessel with the first relatively small heating power, the cooking vessel temperature continues to rise after the short Verification time, a below the target temperature cooking vessel temperature is determined and the cooking vessel heated once more with an intermediate heating power for a Zwischenheiz-time, and then after the intermediate heating time again by adjusting the relatively small heating power is checked whether the cooking vessel temperature after a short Verification time still rises or remains constant, with constant cooking vessel temperature, the first case of reaching the target temperature applies, preferably the target temperature is between 200 ° C and 250 ° C. A method according to claim 3, characterized in that in the event that the cooking vessel temperature after the Zwischenheiz time and after the short Verification time still rises, again below the target temperature cooking vessel temperature is determined and the cooking vessel once again with an intermediate Heating power for a Zwischenheiz-time is heated more strongly, and then checked after Zwischenheiz time again by adjusting the relatively low heating power for a short Verify time, whether the cooking vessel temperature after the short Verification time still rises or remains constant, wherein constant cooking vessel temperature the first case of reaching the target temperature applies. Method according to one of the preceding claims, characterized in that in a further case when heating the cooking vessel with the first relatively small heating power, the cooking vessel temperature drops after the short Verification time, above the target temperature cooking vessel temperature is determined, preferably in heated in this third case, the cooking vessel with an intermediate heating power between 105% and 200% of the first relatively small heating power and the cooking vessel temperature is checked, which is constant after the short Verification time, and from a known in the control relationship between Cooking vessel temperature and heating power as area performance, the cooking vessel temperature is determined, on which basis the heating power is reduced again to a heating power that would permanently lead to the target temperature, preferably the target temperature between 200 ° C and 250 ° C. A method according to claim 5, characterized in that the intermediate heating power is greater than the first relatively small heating power, preferably 10% to 100% larger. Method according to one of the preceding claims, characterized in that the short check-time is 1 second to 30 seconds, preferably 5 seconds to 20 seconds. Method according to one of the preceding claims, characterized in that the intermediate heating time is 5 seconds to 60 seconds, preferably 10 seconds to 30 seconds. Method according to one of the preceding claims, characterized in that the heating power is reduced to a target heat corresponding small heating power, and it is checked when the cooking vessel temperature is constant and thus corresponds to the target temperature, preferably the target temperature between 200 ° C and 250 ° C. lies. Method according to one of the preceding claims, characterized in that the cooking vessel is operated at a cooking point with one or more induction heating coils and the power of the induction heating coils is considered together as area performance or heating power. Method according to one of the preceding claims, characterized in that the amount of energy introduced or the heating power of the induction heating coil is monitored over time. Method according to one of the preceding claims, characterized in that the first relatively large heating power is 3 W / cm ² to 12 W / cm ² , in particular 6 W / cm ² to 10 W / cm ² . Method according to one of the preceding claims, characterized in that the first relatively small heating power is 0.3 W / cm ² to 2 W / cm ² , in particular 0.6 W / cm ² to 0.8 W / cm ² . Method according to one of the preceding claims, characterized in that the intermediate heating power is 1 W / cm ² to 12 W / cm ² , in particular 1.5 W / cm ² to 8 W / cm ² . Method according to one of the preceding claims, characterized in that a cooking vessel size is determined by considering the efficiency of the induction heater by covering the induction heating coil with the established cooking vessel.

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