EP3307019A1 - Method for the operation of an induction hob and induction hob - Google Patents

Abstract

For heating water in a cooking vessel erected above an induction heating coil of an induction hob, a controller drives the induction heating coil at a predetermined relatively high power density. During heating, operating parameters of the induction heating coil are detected by the controller and evaluated to monitor a relative temperature profile of the temperature of a cooking vessel bottom. As soon as this relative temperature curve significantly flattenes or a slope of the relative temperature profile decreases, the controller recognizes this and determines this as the case of a state of "light boiling" and reaching a temperature of a top of the cooking vessel bottom, the 5 ° C to 15 ° C below the boiling point. Then, for a predetermined holding time, the power density is automatically reduced, whereby an operator can hold this state or, after a certain time, can automatically heat up even more.

Description

AREA OF APPLICATION AND PRIOR ART

The invention relates to a method for operating an induction hob to heat water or a similar liquid in a cooking vessel set up above at least one induction heating coil of the induction hob. Furthermore, the invention relates to an induction hob, which is designed to perform this method.

It is from the DE 102009047185 A1 It is known to detect a course of the temperature at the heated cooking vessel or its cooking vessel bottom when heating a cooking vessel by means of an induction heating coil of vibration parameters or operating parameters of the induction heating coil. Although only a relative temperature profile of the temperature of the cooking vessel bottom can be detected, certain functions can be derived therefrom. These are for example in the DE 102011083397 A1 described, which is based on the same physical principle.

TASK AND SOLUTION

The invention has for its object to provide an aforementioned method and trained to carry out induction cooking, with which problems of the prior art can be solved and it is particularly possible to provide more comfort functions or operating functions for operating an induction cooktop.

This object is achieved by a method having the features of claim 1 and by an induction hob with the features of claim 15. Advantageous and preferred embodiments of the invention are the subject of further claims and are explained in more detail below. Some of the features are described only for the process or only for the induction hob. However, they should be able to apply independently and independently of each other both for a process and for a corresponding induction hob. The wording of the claims is incorporated herein by express reference.

It is envisaged that the method, in particular to be able to heat water or a corresponding liquid in the set-up cooking vessel with different degrees of boiling, has the following steps.

A control of the induction hob controls the at least one induction heating coil for inductive heating of the cooking vessel, which is placed above the induction heating coil. It is heated with a given power density, ie a certain power per area. This can be a high power density, for example, higher than 4 W / cm ² to 6 W / cm ² , possibly also a maximum or boost power density of up to 12 W / cm ² . This power density can be specified by an operator. Alternatively, in a particular mode of operation, such as "boiling water", which can be selected on the induction hob, it can be automatically and program dictated by the control of the induction hob as it were.

During heating of the cooking vessel, operating parameters of the at least one induction heating coil, advantageously all induction cooking coils covered by the cooking vessel and operated to heat the same, are detected by the controller. Advantageously, an oscillation response of the induction heating coil is used as the operating parameter. This operating parameter or these operating parameters are evaluated in order to detect or monitor a relative temperature profile of the temperature of the cooking vessel bottom. This is also known from the prior art.

As soon as the detected or monitored relative temperature profile of the cooking vessel bottom clearly flattenes off as a kind of curve or the gradient decreases or even drops below zero, the controller recognizes this. It then determines this as the case of a state of "light boiling" of the water or liquid in the cooking vessel. Further, it is then determined that a temperature has been reached at the top of the cooking vessel bottom that is 5 ° C to 15 ° C below the boiling point of the water. Here is to say that this boiling point is related to a usual height in Germany above the sea level, ie about 20m to 500m above sea level. This altitude range affects the boiling point only insignificantly and can therefore be neglected. In an embodiment of the invention can be provided that this height is entered above the sea level in the induction hob, for example, during the first installation or during the first startup. Then the controller takes into account its effects on the boiling point. The approximate relative temperature curve will always be reasonably the same regardless of the altitude. Of course, only the absolute temperature at the start of the "light boiling" state will vary and be lower as the induction hob is operated above sea level. However, this usually only has a certain effect at a height of more than 1000 m above sea level, namely around 5 ° C. An increase in the relative temperature history of the saucepan bottom may take some time, especially 10 seconds to 300 seconds or 400 seconds Sec. Of course, this depends on the given power density. If this is very high or maximum, in particular using a so-called boost power density for operating the at least one induction heating coil, the duration may also be in the range between 60 seconds and 150 seconds.

If the water has reached a temperature of 100 ° C, then a further increase in temperature can not take place. In this respect, the top of the bottom of the cooking vessel, which is in direct contact with the water, can not reach a higher temperature. So it goes into a kind of saturation or reaches a kind of stop. However, a flattening of an increase in the temperature of the bottom of the cooking vessel occurs before, which is exploited.

After detecting the "light boiling" state, the power density is automatically reduced for a predetermined hold time. Thus, a possibly unwanted strong boiling or excessive bubbling of the boiling of the water or the liquid should be avoided. The power density can be advantageously reduced to a value between 1 W / cm ² and 3.5 W / cm ² . Relatively speaking, the power can be reduced by 10% to 50% or even by 75%, depending on the power density previously used.

Thereafter, an operator is offered a hold option. This holding option is that by operating a control element, advantageously a single control element, which may be particularly advantageous a touch switch, the temperature is controlled by automatically adjusting the power density to that value that prevailed at the time of the start of the hold time , Alternatively, the power density used at the time of the start of the "light boiling" state can be set and kept constant. This may be the power density which has been automatically reduced for the predetermined hold time. Thus, the operator, when operating the operating element, can leave this "light boiling" state maintained for a long time. By using the possibility according to the invention, it does not need to set this state itself consuming by a power density which leads to this state "easy boiling" in the long term.

The holding time can be in the range of a few seconds, advantageously at a maximum of 20 seconds, particularly advantageously a maximum of 10 seconds. If the holding time has elapsed without the operator having selected the holding option or carrying out an actuating operation for the holding option has or any other actuation process for this induction heating coil, with the example, a completely different power density is set manually, so is the default again Power density set. This is a power density that is most likely above the power density that has been automatically reduced during the hold time. Thus, a further heating of the cooking vessel bottom and thus also of the water or the liquid therein will take place again. This may be advantageous for this case if the operator wants to use the water not only in the "light boiling" state, but as "boiling" or bubbling cooking. This is for example advantageous for cooking noodles or is frequently used.

For example, such "light boiling" is more likely to be used for cooking potatoes or eggs, and has the advantage of avoiding spillage of hot water during bubbling cooking. Furthermore, some foods can be undesirably strongly mechanically moved or impaired in the preparation by the strong water movements in the cooking vessel or by the strong movements of the resulting vapor bubbles. Also for this reason, a state of "light boiling" may be more desirable.

In simple words, the invention of an operator so for a certain holding time given the opportunity to maintain a so-called stable state "light boiling". This has been recognized according to the invention. If the operator allows this possibility or this holding option to pass unused, for example because he wishes to bring the water or the liquid to a high boiling point, this takes place automatically after the holding time has expired. Another operation is not necessary.

In an advantageous embodiment of the invention can be provided that the operator is signaled when the state "light boiling" is reached, ie when a temperature of almost 100 ° C or a temperature between 85 ° C and 100 ° C is reached for the water at which the hold time for the hold option begins. Signaling can be done optically and / or acoustically according to various possibilities which are known to the person skilled in the art. Such a signaling can be particularly advantageous in distinguishing from other signaling, so that the operator can see exactly that now this stop option is offered according to the invention and the holding time has started to run.

In an embodiment of the invention can be provided that after the holding time without an actuation process for this Induktionsheizspule, this Induktionsheizspule is operated with a higher power density, just to further heat the cooking vessel or the water therein so a to bring even higher temperature. To Preferably, at least the predetermined power density can be maintained or set again during the first heating of the cooking vessel. Alternatively, an even higher power density can be set, for example also a maximum power density. Thus, the water in the cooking vessel can be heated to a higher temperature for a "strong boiling". Thus, the water can actually be brought up to 100 ° C or to maximum temperature, so that it boils bubbly.

It may be provided that after detecting the state of "strong boiling" of the water in the cooking vessel of the operator a cooking option is offered for a predetermined KochOptions time, which may be a maximum of 20 sec, possibly even a maximum of only 10 sec Increase in the relative temperature of the cooking vessel bottom stopped by reducing the power density. If, during this cooking option, a control is actuated appropriately by the operator, the controller adjusts the power density on the at least one induction heating coil to maintain this "heavy boiling" condition in the cooking vessel. Thus, it does not necessarily maintain the previously used power density with which this "heavy boiling" condition has been achieved. Namely, maintaining the state may also allow for a lower power density, although it should still be a high power density. For this purpose, it can advantageously be provided that exactly that relative temperature which was present at the time of stopping the temperature increase, that is the target temperature or which must also be at 100 ° C., is regulated. Alternatively, the power density used at that time may be maintained.

Also, the achievement of the state "strong boiling" of the water in the cooking vessel can be signaled to the operator generally or specifically. In principle, signaling is similar as previously explained.

In a further embodiment of the invention, it can be provided that a reduction of the power density at the at least one induction heating coil for the cooking vessel after the recognition of the state of "light boiling" is used, a first temperature difference between the temperature at the time of detecting the state "light boiling "and a temperature that was 3 seconds to 20 seconds after the beginning of the reduction in power density, in particular during the hold option. After this time of 3 seconds to 20 seconds, the power density at the at least one induction heating coil can rise again or be increased by the controller. In particular, it can to the predetermined power density during the first heating of the water in the cooking vessel increase. This may be a previously described power increase from light boiling to heavy boiling.

Thereafter, the power density can be reduced again and a second difference between a temperature at the time of the power density reduction and a temperature after a time between 3 sec and 20 sec after the power density reduction is determined. This second difference is then compared to the first difference. In the case that the second difference is smaller than the first difference, it is considered that the relative temperature of the cooking vessel at the time of first reducing the power density does not yet correspond to the state of "high boiling" but only to the state of "low boiling". , If this condition is desired "light boiling", then the temperature fits. Then it can be regulated on it. If the condition "strong boiling" is desired, the power density should be increased again for even more heating.

In a further embodiment of the invention, it can be provided that the controller shuts off the at least one induction heating coil when the cooking vessel is heated with a power density for maintaining the state of "light boiling" after a maximum of 2 hours. This time can be a maximum of 1 hour, alternatively 5 minutes to 30 minutes, so that this state does not last so long that it is obvious that there is a fault or that the operator does not monitor the cooking process or has in sight ,

In a similar form as mentioned above, it can be provided that the at least one induction heating coil is operated at a heating of the cooking vessel with a power density sufficient to maintain the state of "strong boiling". Then it can be switched off after a maximum of 30 minutes. This can only be a maximum of 20 minutes. Finally, a significantly higher power density is set as previously described and thus given a certain higher risk of malfunction. As an alternative to switching off, the power density can be reduced by at least 30% to 60%.

In a further further embodiment of the invention can be provided that the controller sets a medium or rather small power density for the at least one induction heating to keep the state of "easy boiling" or the state of "strong boiling". Here, a power density of less than 4 W / cm ^{2 may be} sufficient, advantageously less than 3 W / cm ² , to maintain the "light boiling" condition. It can be provided that an operator at an operating device of the induction hob, which is of course connected to the controller, either a corresponding predetermined power density selects and then additionally a special function that causes the achievement of the hold option. Alternatively, the same and only a certain program sequence can be started, in which the operator does not specify directly the power density as a cooking level, but only just this type of heating, in the state "light boiling" the holding option is offered and, after its expiration without appropriate operation, continues to heat up to the strong boiling.

In a further embodiment of the invention can be provided that the controller is designed, possibly after basic operator-dependent programming, when heating a raised cooking vessel and reaching the temperature of nearly 100 ° C or a temperature slightly below the boiling point holding option to offer automatically. Thus, it is always available to an operator, without having to be previously selected with a certain adjustment. The aforementioned time delay of a maximum of 20 seconds for the hold option seems defensible, even if an operator does not specifically desire this hold option at all.

These and other features will become apparent from the claims but also from the description and drawings, wherein the individual features each alone or more in the form of sub-combinations in an embodiment of the invention and in other fields be realized and advantageous and protectable Represent embodiments for which protection is claimed here. The subdivision of the application into 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

eine schematische Darstellung eines Induktionskochfelds mit Induktionsheizspule zur Durchführung des erfindungsgemäßen Verfahrens und

Fig. 2

verschiedene Verläufe von Temperaturen sowie ein Verlauf eines Betriebsparameters einer Induktionsheizspule des Induktionskochfelds aus Fig. 1 als relativer Temperaturverlauf über der Zeit.

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

Fig. 1

a schematic representation of an induction cooktop with induction heating coil for carrying out the method according to the invention and

Fig. 2

different courses of temperatures as well as a course of an operating parameter of an induction heating coil of the induction hob Fig. 1 as a relative temperature over time.

DETAILED DESCRIPTION OF THE EMBODIMENTS

In the Fig. 1 is very schematically a part of an induction hob 11 shown with a cooktop plate 13 and an induction heating coil arranged therebelow 15, as they are known from the prior art, in particular also from the aforementioned. On a cooking place 16 formed above the induction heating coil 15, a pot 18 with water is placed therein to be heated or brought to a boil.

Furthermore, the induction hob 11 has a controller 20 which is connected to the induction heating coil 15 to detect the operating parameter of the induction heating coil 15 described above, in particular a vibration response, so as to detect a relative temperature profile of the temperature of the bottom of the pot 18. In this regard, the above-mentioned DE 102009047185 A1 and DE 102011083397 A1 directed. Furthermore, the controller 20 is still connected to an optical or acoustic display 22 and at least one control element 23. In addition, the controller 20 is advantageously connected to all the controls of the induction hob 11 and forms the only control of the induction hob 11th

In the Fig. 2 is shown in a diagram over time t, as the temperature T _{B of} the bottom of the pot 18 extends, at the top of the bottom, as well as the temperature T _{W of} the water in the pot 18 extends. These values are not recorded during the method according to the invention and are shown here by way of example in accordance with measurements that were carried out within the scope of the invention. The temperature T _W of the water is a mean temperature, since the water will be slightly hotter directly above the bowl bottom than at the top. During heating, such an inhomogeneous temperature distribution is common. The temperature differences are a maximum of about 10 ° C to 20 ° C apart. Furthermore, the relative temperature profile S of the bottom of the pot 18 is plotted over time, as it can be detected from the above-described operating parameter of the induction heating coil 15.

At the time t = 0, a pot 18 placed on the induction hob 11 or the hotplate 16 is heated with water from the induction heating coil 15. For this purpose, the controller 20 sets a high power density, for example a maximum boost power density of 10 W / cm ² . During the first approx. 20 sec to 40 sec, the relative temperature curve S rises sharply, and the cup bottom temperature T _{B also} increases, albeit weaker. The temperature T _{W of} the water, however, rises only slowly. In this phase, especially the pot bottom heated, because only this can couple the heat in the water, which naturally slows down.

Between a time of about 50 seconds to 250 seconds, the temperatures T _B and T _W with almost constant slope and also run almost parallel, the water temperature T _W approaches the temperature profile T _B something. At the time of about t = 300 sec, the averaged water temperature T _{W reaches} a value of about 85 ° C. Just a few seconds before the bottom of the pot can have reached a temperature of 100 ° C, which means that this temperature, as can be seen, can not be exceeded while there is still water in the pot 18. Here, the course S slopes or its slope decreases, from t = 300 sec, the course S is approximately horizontal. Here then begins the invention, as has been previously described. Before this is discussed in more detail, an example of a further continued cooking process will be described. Until the time t = 370 sec, the water temperature T _{W is} still rising, but at the end only weaker. At this time, the water is then continuously heated to about 100 ° C, in the pot 18, the entire water boils, so to speak bubbling as a state of "strong boiling".

At time t = 300 sec, the water in pot 18 has just reached the state of "light boiling". Even if an average water temperature T _{W is} only about 85 ° C, there is already at the bottom of the bottom of the pot a clear formation and detachment of vapor bubbles, so that an operator can already recognize a certain boiling or light cooking. This is also sufficient for processes such as cooking noodles, potatoes or the like, but not yet, for example, not usually to start cooking noodles.

It can therefore be seen that, after reaching the state of "light boiling", when the pot bottom has already reliably reached a temperature of T _B = 100 ° C., it will take over 60 seconds until the water in the pot 18 actually boils bubbly and thus continuously or averaged has a temperature of T _W = 100 ° C. Furthermore, it can be seen from the relative temperature curve S that there are changes in the course S or the slope at these two times, which can be evaluated by the controller 20.

In the method according to the invention, the controller 20 recognizes from the relative temperature curve S at the time t = 300 sec approximately the beginning of the state "light boiling", since just here the relative temperature curve S flattens out greatly or even becomes horizontal, ie its slope becomes zero becomes. From the first derivation of the relative temperature curve S, therefore, this point in time can be approximately recognized. During the cooking process of the controller 20 has just been started with a high or maximum power density, after detection of the state "easy boiling" at time t = 300 sec the above-described holding option for the above-mentioned holding time T _H of about 20 sec is offered. The power density is greatly reduced to about 2 W / cm ² to 3 W / cm ² , so it is only 20% to 25%. On the display 22, the controller 20 outputs a corresponding signal to an operator and the above-described holding time T _H is started. Due to the reduced power density, the state of "light boiling" is then kept as possible and the water temperature T _W takes the course shown in dash-dotted lines, ie remains at about 85 ° C. This holding option offered to the operator can then be assumed by actuating the operating element 23 if this takes place within the holding time T _H. The actuation of the operating element 23 or the assumption of the holding option then leads to this reduced power density being approximately maintained or that a temperature control by means of the relative temperature curve S regulates to the temperature T _W at the time t = 300 sec. This is in the Fig. 2 represented by the constant dot-dash line of the water temperature T _W at 85 ° C.

However, if the operator allows the holding time T _{H to} elapse and thus does not use the holding option, the previous high power density can be set again after the holding time has expired, in this case the maximum boost power density. Then according to the in Fig. 2 solid curve for the water temperature T _W again rise up to 100 ° C. Alternatively, after an inconsequential lapse of the hold option or the hold time, the power density can be increased again by the controller 20, but not to the maximum boost power density used at the outset, but to a high power density, for example at 4 W / cm ² to 6 W / cm ² . Then, although again, a renewed heating of the water in the pot to a final temperature of 100 ° C throughout, but this takes a little longer.

The dashed line is the curve for the pot bottom temperature T _B from the time of 300 seconds, when the power has been reduced by the controller 20 during the holding option. As a result of this power reduction, the pot base temperature T _B also drops somewhat, as shown in dotted lines. In the case of the use of the holding option, it then remains at a low power density, so that in the long term, here, for example, from about 370 seconds, the pot bottom temperature T _B has approached the water temperature T _W and is equal to this.

Claims (15)

A method of operating an induction hob (11) to heat water in a cooking vessel (18) positioned above at least one induction heating coil (15) of the induction hob, comprising the steps of: a control (20) of the induction hob controls the at least one induction heating coil (15) for inductive heating of the erected cooking vessel (18) with a predetermined power density, during the heating of the cooking vessel (18), operating parameters of the at least one induction heating coil (15) are detected and evaluated by the controller (20) in order to monitor a relative temperature profile of the temperature of a cooking vessel bottom, - As soon as the relative temperature profile of the cooking vessel bottom significantly flattening or a slope of the relative temperature profile decreases, the controller recognizes this (20) and determines this as the case of a state of "light boiling" and reaching a temperature of a top of the cooking vessel bottom, the 5 ° C is up to 15 ° C below the boiling point, - then the power density is automatically reduced for a predetermined holding time, an operator is offered a holding option such that by operating a control element (23) the temperature is regulated by means of automatic adjustment of the power density to the value at the time of the start of the hold time or the power density at the time of the start of the state "light Boiling is kept constant, - After the holding time without an actuation process for this induction heating coil (15), the predetermined power density is set again. A method according to claim 1, characterized in that the controller (20) drives the at least one induction heating coil (15) for inductive heating of the erected cooking vessel (18) with a predetermined relatively high power density. Method according to claim 1 or 2, characterized in that the controller (20) for the predetermined holding time automatically reduces the power density to a value between 1 W / cm ² and 3.5 W / cm ² or by 10% to 50%. , Method according to one of the preceding claims, characterized in that the controller (20) reaching the temperature of almost 100 ° C or between 85 ° C and 100 ° C as a state of "light boiling" of the water in the cooking vessel (18) of Operator signals, in particular visually and / or acoustically signaled. Method according to one of the preceding claims, characterized in that the controller (20) offers the operator the holding option for a holding time of a maximum of 20 seconds, preferably a maximum of 10 seconds. Method according to one of the preceding claims, characterized in that after expiration of the holding time without an actuating operation, the controller (20) operates the at least one induction heating coil (15) with a higher power density for further heating of the cooking vessel (18) or therein water to a higher temperature. A method according to claim 6, characterized in that for this at least the predetermined power density during the first heating of the cooking vessel (18) is maintained or a higher power density is set to more heat the water in the cooking vessel (18) to a higher temperature for a state " strong boiling ", preferably at 100 ° C. A method according to claim 6 or 7, characterized in that after detecting the state of "heavy boiling" of the water in the cooking vessel (18) by stopping an increase in the relative temperature of the cooking vessel bottom the operator is offered a cooking option for a predetermined cooking option time of a maximum of 20 seconds, preferably of a maximum of 10 seconds, in which, by operating a control element (23), the controller (20) adjusts the power density at the at least one induction heating coil (15) so that this state is "heavy boiling" the at least one induction heating coil (15) or in the cooking vessel (18) is maintained, preferably by regulating at exactly this relative temperature at the time of stopping their rise or by maintaining the power density set at that time. Method according to one of claims 6 to 8, characterized in that the controller signals the achievement of the state of "strong boiling" of the water in the cooking vessel (18) of the operator, in particular visually and / or acoustically signaled. Method according to one of the preceding claims, characterized in that a reduction of the power density at the at least one induction heating coil (15) after detecting the state of "light boiling" is used, a first temperature difference between the temperature at the time of detecting the state "light The controller determines the power density at the at least one induction heating coil (15) again, after which time from 3 seconds to 10 seconds, the power density again increases is reduced and a second difference between a temperature at the time of reducing the power density and a temperature after a time between 3 seconds and 10 seconds thereafter is determined, in which case this second difference is compared with the first difference, in which case the second difference is less than the first Dif Furthermore, the relative temperature of the cooking vessel (18) at the time of first reducing the power density is not yet classified as a "strong boiling" state, but as a "boiling state" state. A method according to claim 10, characterized in that after this time from 3 seconds to 10 seconds, the controller again increases the power density of the at least one induction heating coil (15) to the predetermined power density during the first heating of the water in the cooking vessel (18). Method according to one of the preceding claims, characterized in that the controller shuts off the at least one induction heating coil (15) during a heating of the cooking vessel (18) with a power density for holding the state of "light boiling" after a maximum of 2 hours, in particular 1 hour max. Method according to one of the preceding claims, characterized in that the controller shuts off the at least one induction heating coil (15) during a heating of the cooking vessel (18) with a power density for maintaining the state of "heavy boiling" after a time of at most 30 minutes, in particular 20 minutes or less, or power density reduced by at least 30% to 60%. Method according to one of the preceding claims, characterized in that by the controller (20) a small power density for the at least one induction heating coil (15) is set to operate the induction heating coil (15) to maintain the state of "easy boiling" or the state of "strong boiling", preferably a power density of less than 3 W / cm ² for the "light boiling" condition. Induction hob, characterized by : at least one induction heating coil (15), a controller (20), an operating element (23), wherein the controller (20) is adapted to perform the method according to any one of the preceding claims.

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