EP3890432B1 - Hob comprising an improved cooking programme, cooking system, cooking method and corresponding programme - Google Patents

Description

Field of the invention

The present invention relates to the field of cooking plates, intended to heat food placed in a cooking vessel.

It particularly relates to such a cooking plate comprising a program specifically adapted to bring a liquid to a boil and to maintain this boiling, for example to ensure the cooking of food in this liquid.

The invention also relates to a cooking system comprising such a cooking plate, a cooking vessel and equipment for measuring the temperature of the content of the cooking vessel.

The invention also relates to a cooking process specifically adapted to bring a liquid to a boil and to maintain this boiling, for example to ensure the cooking of food in this liquid.

It relates most particularly to such a cooking method suitable for bringing a liquid to a boil and maintaining this boiling while avoiding any overflow of the liquid.

Finally, the invention also relates to a computer program that can be used to implement such a method.

Prior art

Several types of hotplates are known, intended to heat food contained in a cooking receptacle such as a saucepan.

Among these hotplates, some, commonly called hotplates, transmit the heat from thermoelectric resistors to the cooking vessel. Such plates are generally considered to have relatively high thermal inertia. Other hotplates provide heating of the cooking vessel by the combustion of a fuel, most often a combustible gas. Finally, other cooking plates, commonly called induction plates, emit lines of magnetic fields inducing an eddy current in a cooking container, causing the heating of this container by Joule effect.

The present invention can be applied to the different types of known cooking plates which offer low thermal inertia. However, it applies more particularly to induction hobs, the characteristics of which make it possible to take full advantage of the advantages of the invention.

Cooking plates are often used to bring a liquid, such as water, contained in the cooking vessel to a boil in order to cook food placed in the boiling liquid. In such situations, it is generally sought to obtain the boiling of the liquid as quickly as possible, by providing maximum heating power to the cooking vessel.

Once boiling is achieved, maintaining the liquid at boiling temperature generally does not require the maximum heating power that can be offered by the hob. On the contrary, it is preferable that the heating power supplied to the boiling liquid by the cooking plate be lower.

Indeed, if the power supplied by the cooking plate is too high, it generates an increase in the evaporation of the liquid, and therefore its bubbling. In addition to unnecessary energy consumption, this bubbling leads to loss by evaporation of the liquid used for cooking, and a risk of overflow of the liquid. This risk of boiling over is particularly common when a food containing starch, such as pasta or rice, has been cooked in the boiling liquid.

To avoid this excessive bubbling, it is known to lower the heating power of the cooking plate when the boiling of the liquid is obtained. This reduction in heating power can be carried out manually. It can also be carried out automatically by a program integrated into the cooking plate, associated with boiling detection means.

It is known to measure the temperature inside the cooking vessel. Thus, the document EP 1 037 508 A1 shows a system consisting of a cooking plate and a cooking container in which is placed a temperature probe able to communicate to the cooking plate information on the temperature of a liquid contained in the cooking container. If it makes it possible to know the temperature of the liquid, such a probe does not however make it possible to determine what is the boiling point of this liquid. Indeed, the boiling point of a liquid can vary depending on the nature of this liquid. For example, it will not be identical for water, salt water, milk, etc. Moreover, this boiling temperature varies according to the atmospheric pressure, and therefore to the altitude. The measurement of the temperature of the liquid is therefore insufficient to effectively detect its boiling.

It is also known, in particular from the document EP 2 020 826 A1 , to determine that a liquid is boiling by detecting vibrations generated by boiling. Such a method is however particularly complex to implement.

It is still known, in particular from the document JP 2004-127822 , to determine that a liquid is at its boiling point when the temperature measured by a sensor integrated into the cooking plate remains stable for a long time, despite a high energy input. However, such a method only makes it possible to detect boiling after having supplied a large quantity of energy to the boiling liquid, which risks causing strong boiling and therefore an overflow.

When boiling is detected, it is not easy to determine the most appropriate heating power to maintain this boiling without it being too strong. For this, it is known to ask the user to enter, by means of an appropriate control of the cooking plate, the volume of liquid that he wishes to keep boiling, in order to be able to adapt the heating power to this volume. However, this solution introduces a constraint for the user, and may lack reliability if the latter does not correctly fill in the requested information. Moreover, this suitable heating power may vary during cooking, in particular when the content of the cooking vessel varies during cooking, for example if the user has introduced food into the boiling liquid.

The document EP 1 768 461 A1 describes a hob according to the preamble of claim 1.

Objectives of the invention

The present invention aims to overcome these drawbacks of the prior art.

In particular, the object of the invention, according to at least some of its embodiments, is to provide a cooking plate, a cooking system comprising such a cooking plate and a method of cooking, which allow rapid boiling a liquid contained in a cooking vessel, and to maintain this liquid at a relatively low boil.

Another object of the invention is to provide such a cooking plate, such a cooking system and such a cooking method which make it possible to bring a liquid to a boil and to maintain its boiling while generating relatively low energy consumption.

Another object of the invention is to provide such a cooking plate, such a cooking system and such a cooking method which make it possible to avoid overflows caused by excessive boiling of a liquid brought to the boil.

Another object of the invention is to provide such a cooking plate, such a cooking system and such a cooking method which are particularly easy to use for the user.

Yet another object of the invention, according to certain embodiments, is to provide such a cooking plate, such a cooking system and such a cooking method which take into account the modifications of the contents of the cooking vessel.

Disclosure of Invention

• fournir une puissance de chauffage connue au récipient de cuisson, au cours d'une phase de montée en température,
• déterminer une valeur représentative de la capacité thermique d'un ensemble à chauffer comprenant le récipient de cuisson et son contenu, en divisant l'énergie de chauffage fournie au cours d'une première période de mesure comprise dans la phase de montée en température, par l'élévation de température du liquide pendant la première période de mesure,
• détecter l'ébullition du liquide, correspondant à la fin de la phase de montée en température et au début d'une phase de maintien de l'ébullition,
• fournir une puissance de chauffage, au cours de la phase de maintien de l'ébullition, à un niveau de puissance choisi en fonction de la valeur représentative de la capacité thermique de l'ensemble à chauffer, déterminée au cours de la phase de montée en température.

These objectives, as well as others which will appear more clearly subsequently, are achieved with the aid of a cooking plate, capable of heating a cooking vessel containing a liquid, this cooking plate being capable of receiving a measure the temperature of the liquid contained in the cooking vessel, this cooking plate implementing a cooking program comprising the steps consisting in:

• provide a known heating power to the cooking vessel, during a temperature rise phase,
• determine a value representative of the thermal capacity of an assembly to be heated comprising the cooking vessel and its contents, by dividing the heating energy supplied during a first measurement period included in the temperature rise phase, by the temperature rise of the liquid during the first measurement period,
• detect the boiling of the liquid, corresponding to the end of the temperature rise phase and the start of a boiling maintenance phase,
• supplying a heating power, during the boiling maintenance phase, at a power level chosen according to the value representative of the heat capacity of the assembly to be heated, determined during the heating up phase temperature.

The heating energy supplied by the cooking plate during the first period corresponds to the integral of the heating power supplied during this first measurement period.

It is thus possible, advantageously, to adjust the heating power necessary to maintain boiling according to the heat capacity of the assembly to be heated, and therefore, in practice, according to the quantity of liquid which should be kept boiling. This adjustment of the heating power advantageously makes it possible to maintain boiling at a moderate level, without superfluous power input. The low bubbling caused by this boiling greatly limits the risk of the liquid overflowing out of the cooking vessel.

It should be noted that, according to the invention, the heat capacity of the assembly to be heated does not have to be entered by the user, which simplifies the use of the cooking plate. Furthermore, this heat capacity of the assembly to be heated is advantageously determined before boiling is reached. It is thus possible to adjust the heating power immediately after the occurrence of boiling, to avoid excessive boiling of the liquid.

Advantageously, during the implementation of the cooking program, the hob detects the boiling of the liquid, after the first measurement period, by determining that the rise in temperature of the liquid during a second period measurement included in the temperature rise phase is below a threshold value.

It is thus possible to quickly detect boiling, which is characterized in particular by temperature stability despite the supply of heating power. Rapid boil detection allows quick adjustment of heating power to prevent excessive boiling of the liquid.

Preferably, the duration of this second measurement period is chosen as a function of the value representative of the heat capacity of the assembly to be heated, determined previously.

Thus, the detection of boiling can be carried out with optimum efficiency, in particular when the small quantity of liquid increases the risks of excessive boiling if excessive power is supplied after the boiling point.

According to a preferred embodiment, this threshold value is a predetermined fixed value, independent of the value representative of the thermal capacity of the assembly to be heated and of the duration of the second measurement period.

According to another possible embodiment, this threshold value is determined as a function of the value representative of the heat capacity of the assembly to be heated or of the duration of the second measurement period.

In this case, advantageously, the threshold value is determined so that the quotient of the rise in temperature of the liquid during the second measurement period over the duration of said second measurement period is a predetermined fixed value.

According to an advantageous embodiment, the heating power level during the boiling maintenance phase is chosen between several predetermined values, each of the predetermined values being associated with a range of values representative of the heat capacity of the together to heat.

Preferably, during the boiling maintenance phase, the cooking plate detects a drop in the temperature of the liquid, and modifies the level of heating power to regulate the temperature of the liquid to the boiling temperature.

Such regulation makes it possible to avoid any risk of prolonged loss of boiling of the liquid.

Preferably, the cooking plate is constituted by an induction plate, capable of producing variable magnetic fields capable of generating eddy currents induced in the cooking vessel, to heat the cooking vessel by Joule effect.

Such cooking plates allow precise control of the heating power, with very low thermal inertia. They thus allow the effective implementation of the invention.

• une plaque de cuisson telle que décrite ci-dessus,
• un récipient de cuisson, et
• un équipement de mesure de la température du contenu du récipient de cuisson.

The invention also relates to a cooking system comprising:

• a cooking plate as described above,
• a cooking vessel, and
• equipment for measuring the temperature of the contents of the cooking vessel.

Preferably, this equipment for measuring the contents of the cooking vessel comprises a temperature probe in contact with the contents of the cooking vessel.

Such a cooking system can advantageously have the various characteristics described above in relation to the cooking plate, these characteristics being taken individually or in combination.

• la fourniture par la plaque de cuisson d'une puissance de chauffage connue au récipient de cuisson, au cours d'une phase de montée en température,
• la détermination d'une valeur représentative de la capacité thermique d'un ensemble à chauffer comprenant le récipient de cuisson et son contenu, en divisant l'énergie de chauffage fournie au cours d'une première période de mesure comprise dans la phase de montée en température, par l'élévation de température du liquide pendant la première période de mesure,
• la détection de l'ébullition du liquide, correspondant à la fin de la phase de montée en température et au début d'une phase de maintien de l'ébullition,
• la fourniture par la plaque de cuisson d'une puissance de chauffage, au cours de la phase de maintien de l'ébullition, à un niveau de puissance choisi en fonction de la valeur représentative de la capacité thermique de l'ensemble à chauffer, déterminée au cours de la phase de montée en température.

The invention also relates to a cooking method, implemented by a cooking system comprising a cooking plate, a cooking vessel containing a liquid, and equipment for measuring the temperature of the liquid contained in this cooking vessel, the cooking process comprising the following steps:

• the supply by the hob of a known heating power to the cooking vessel, during a temperature rise phase,
• the determination of a value representative of the heat capacity of an assembly to be heated comprising the cooking vessel and its contents, by dividing the heating energy supplied during a first measurement period comprised in the ramp-up phase temperature, by the rise in temperature of the liquid during the first measurement period,
• the detection of the boiling of the liquid, corresponding to the end of the temperature rise phase and the start of a boiling maintenance phase,
• the supply by the hob of a heating power, during the boiling maintenance phase, at a power level chosen according to the value representative of the thermal capacity of the assembly to be heated, determined during the temperature rise phase.

• une sous-étape de détermination de la durée d'une seconde période de mesure, en fonction de la valeur représentative de la capacité thermique de l'ensemble à chauffer,
• une sous-étape de détermination de l'évolution de la température du liquide au cours de la seconde période de mesure,
• une sous-étape de comparaison de l'évolution de la température du liquide au cours de la seconde période de mesure avec une valeur seuil.

Preferably, the step of detecting the boiling of the liquid is implemented after the first measurement period, and comprises:

• a sub-step of determining the duration of a second measurement period, as a function of the value representative of the heat capacity of the assembly to be heated,
• a sub-step of determining the change in temperature of the liquid during the second measurement period,
• a sub-step of comparing the change in temperature of the liquid during the second measurement period with a threshold value.

Such a cooking method can advantageously have the different characteristics described in relation to the cooking plate, these characteristics being taken individually or in combination.

The invention also relates to a computer program comprising instructions which, when the computer program is executed by a device for controlling a cooking hob, lead the latter to implement a cooking method as described above.

List of Figures

• [Fig. 1] la figure 1 est une représentation schématique, en vue de coupe transversale, d'un système de cuisson selon un mode de réalisation de l'invention ;
• [Fig. 2] la figure 2 est un ensemble de courbes représentatives de la température d'un premier volume de liquide porté à ébullition puis maintenu à ébullition par un procédé selon un mode de réalisation de l'invention, et de la puissance de chauffage fournie à ce liquide ;
• [Fig. 3] la figure 3 est un ensemble de courbes représentatives de la température d'un second volume de liquide porté à ébullition puis maintenu à ébullition par un procédé selon un mode de réalisation de l'invention, et de la puissance de chauffage fournie à ce liquide ;
• [Fig. 4] la figure 4 est une représentation schématique des étapes d'un procédé selon un mode de réalisation de l'invention ;
• [Fig. 5] la figure 5 est une représentation schématique des sous-étapes de l'une des étapes du procédé de la figure 4 ;
• [Fig. 6] la figure 6 est un ensemble de courbes représentatives de la température d'un liquide porté à ébullition et de la température de l'extérieur du récipient de cuisson contenant ce liquide.

The invention will be better understood on reading the following description of preferred embodiments, given by way of a simple figurative and non-limiting example, and accompanied by the figures among which:

• [ Fig. 1 ] the figure 1 is a schematic representation, in cross-sectional view, of a cooking system according to one embodiment of the invention;
• [ Fig. 2 ] the figure 2 is a set of curves representative of the temperature of a first volume of liquid brought to a boil then kept boiling by a method according to one embodiment of the invention, and of the heating power supplied to this liquid;
• [ Fig. 3 ] the picture 3 is a set of curves representative of the temperature of a second volume of liquid brought to a boil and then kept boiling by a method according to one embodiment of the invention, and of the heating power supplied to this liquid;
• [ Fig. 4 ] the figure 4 is a schematic representation of the steps of a method according to one embodiment of the invention;
• [ Fig. 5 ] the figure 5 is a schematic representation of the sub-steps of one of the process steps of the figure 4 ;
• [ Fig. 6 ] the figure 6 is a set of curves representing the temperature of a boiling liquid and the temperature outside the cooking vessel containing this liquid.

Detailed Description of Embodiments of the Invention

The figure 1 schematically represents, in cross-sectional view, a system according to one embodiment which comprises a cooking plate 1 supporting a cooking vessel 2 containing a liquid 3. A temperature probe 4 is immersed in this liquid 3.

In the embodiment shown, the hob 1 is an induction hob. It comprises an upper plate 11, intended to carry the containers of cooking. This upper plate 11 is, conventionally, a glass-ceramic plate. Below this upper plate 11, induction coils 12 produce, when they are electrically powered, a variable magnetic field capable of generating eddy currents induced in a cooking vessel 2 placed on the upper plate 11. These induced currents of Foucault cause, by Joule effect, the heating of the cooking vessel 2.

The power supply to this induction coil 12 is controlled by a control device 13. This control device 13 is an electronic card, capable of executing programs, which can receive instructions from the user, for example by between hotplate control knobs (not shown). Depending on the instructions it receives, it can deliver the appropriate heating power. In the present description, the term “heating power”, or “useful power”, designates the power supplied by the cooking plate, which is actually used for heating the cooking vessel. In the embodiment shown, this heating power corresponds to approximately 90% of the electrical power delivered to the induction coils 12, which is converted by these induction coils into magnetic waves, which are themselves converted into heat in the cooking vessel.

Advantageously, when the hob 1 is an induction hob as in the embodiment shown, the control device 13 can measure, with a measurement precision of the order of 2 to 5%, the electrical power delivered to the induction coils 12. The efficiency of these induction coils being known elsewhere, it is therefore possible to know the heating power transmitted to the cooking vessel 2 with an accuracy of the order of 2 to 5%.

In other possible embodiments, the cooking plate 1 can be of a different type. It is however important, for the implementation of the invention, that the cooking plate 1 has a low thermal inertia and is able to measure precisely, at each instant, the power received by the cooking vessel 2. Thus, if the hob 1 is a gas combustion hob, it is possible that it is equipped with a flow meter to measure the volume of gas burnt to warm the cooking vessel. The heating power, which is proportional to the flow rate of burnt gas, for a given quality of gas, can be known with sufficient precision.

The invention is however of particular interest in the case of induction cooking plates, for which it is particularly easy to know in real time the heating power absorbed by the cooking vessel 2.

In the embodiment shown, the cooking vessel 2 is a metal saucepan, suitable for cooking on an induction hob. Other types of cooking vessels can be used, provided they are suitable for the hob on which they are heated.

The cooking container 2 is filled with a liquid 3 intended to be heated until boiling, for example to cook food in the boiling liquid. This liquid 3 can for example be water, salt water, milk, etc. This liquid 3 can contain the food to be cooked. However, in many cases, the food to be cooked is only placed in the liquid after it has reached a boil.

It will be considered, in the remainder of this description, that the cooking receptacle 2 and the contents of this receptacle constitute an “assembly to be heated”. This assembly to be heated of course only comprises the parts of the cooking container intended to rise in temperature, and not the parts of this container which are thermally insulated, such as for example the handles of a saucepan.

In the embodiment represented, the cooking vessel 2 is equipped with a temperature probe 4, immersed in the liquid 3. This temperature probe advantageously makes it possible to directly measure the temperature of the liquid 3. The temperature probe 4 represented comprises radio communication equipment, and is thus capable of communicating by radio the temperature values that it records to the cooking plate 1, which comprises for this purpose a suitable radio communication equipment 14, connected to the control device 13.

Thus, the control device 13 can permanently know both the electrical power values supplied to the induction coils 12, and therefore the heating power, and the temperature of liquid 3 supplied by temperature probe 4.

In other possible embodiments, other types of temperature measuring equipment can be used to know the temperature of the liquid 3. These temperature measuring equipment, which are known in themselves to those skilled in the art profession, can for example be in thermal contact with the liquid 3, to directly measure its temperature, or measure the infrared radiation of the liquid 3 to deduce its temperature.

The implementation of the invention requires that the equipment for measuring the temperature of the liquid 3 measures the temperature of the liquid 3 precisely and in real time. In particular, it is important that the temperature measurement be carried out with a margin of error of less than 3°C, and preferably less than 1°C. It is also important that the resolution of this temperature measurement be fine, less than 0.3°C, and preferably less than 0.1°C. Such a fine resolution makes it possible to follow the temperature variations of small amplitude, preferably the temperature variations of the order of 0.1° C., which is important for the implementation of the invention.

The term "measurement of the temperature of the liquid", in the present application, therefore only relates to measurements making it possible to know the real temperature of the liquid with a margin of error of less than 3° C., and preferably, with a margin of error less than 1°C, and with a resolution less than 0.3°C, and preferably less than 0.1°C. The embodiments of the invention in which a temperature measuring equipment is directly in contact with the heated liquid, which generally make it possible to know the temperature of the liquid with a margin of error of the order of 1°C and a resolution of the order of 0.1°C, are therefore preferred.

It should be noted that the invention cannot be implemented with known measuring equipment measuring the temperature of the outside of the cooking vessel to estimate the temperature of the liquid contained in this vessel. Such measuring equipment does not in fact make it possible to measure the temperature of the liquid sufficiently accurately to implement the invention.

For example, the figure 6 represents the temperature measurement curves recorded by several measuring equipment during the heating of a cooking vessel filled with water, to which a constant heating power is applied from time 0. The curve 91 represents the measurement of temperature of the liquid taken by a probe in direct contact with this liquid, which is a precise measurement, in real time, allowing the implementation of the present invention.

Curve 92 represents the measurement of the temperature of the outside of the cooking vessel, taken by a probe placed in the cooking plate. It is clearly noted that the probe placed in the cooking plate does not make it possible to measure the temperature of the water. Thus, it measures 100°C when the liquid has already greatly exceeded its boiling point and it subsequently measures a temperature well in excess of 100°C. Such a measurement of the temperature of the outside of the cooking vessel therefore does not constitute a measurement of the temperature of the liquid, within the meaning of the present application.

The cooking programs of the prior art which are based on such measurements of the temperature of the outside of the cooking container are therefore necessarily very different from the solution of the invention, and generally do not allow detection of the boil fast enough to avoid a strong boil, risking boiling over of the liquid.

According to the invention, the cooking plate 1 is configured to apply a particular cooking program to the assembly to be heated consisting of the cooking vessel 2 and the liquid 3, this cooking program being specifically adapted to bring the liquid 3 to boil and to keep it at a moderate boil.

This cooking program, which will be called hereafter "boiling program", can be a computer program executed by the control system 13 of the cooking plate 1. It can be triggered, for example, by the pressure of a user on a specific button for triggering this boiling program, or by the choice of this program by the user in an interactive menu.

This boiling program controls the cooking plate 1 so that it heats the cooking vessel 2 during two successive phases: a rising phase temperature, and a boiling maintenance phase. The figure 2 and 3 represent the evolution of the temperature of the liquid 3 and of the heating power delivered by the cooking plate 1 during the execution of this boiling program. In the situation represented by the picture 2 , the volume of liquid 3 which is boiled is relatively small. In the situation represented by the picture 3 , this volume of liquid 3 which is brought to a boil is substantially greater.

When the user triggers the boiling program, it is possible, in certain embodiments, for preliminary measurements to be carried out before the temperature rise phase, or at the start of this phase. These preliminary measurements, which are known in themselves to those skilled in the art, can for example be intended to check that a suitable cooking container 2 is indeed placed on the cooking plate 1, that the temperature probe 4 is well placed in this cooking container 2, or that the temperature of the liquid 3 in the cooking container 2 is not too high to engage the boiling program.

The boiling program starts, possibly after the preliminary measurements, by implementing the heating phase. During this temperature rise phase, the control system 13 delivers to the induction coils 12 a high power level, for example a maximum power level, so that the cooking plate 1 provides maximum heating power to the cooking container, and therefore to the assembly to be heated. The liquid 3 contained in the cooking receptacle 2 therefore heats up at high speed, for example at the fastest speed allowed by the cooking plate 1. This temperature rise phase is in fact intended to quickly obtain the liquid boil 3.

During this temperature rise phase, the boiling program implements a step for determining the heat capacity of the assembly to be heated, or a value representative of this heat capacity. For the implementation of this step, the control device 13 measures, during a first measurement period, the rise in temperature of the liquid 3 and the heating energy supplied by the cooking plate 1, which corresponds to the integral of the heating power supplied during the first measurement period. These measures allow the control device 13 to calculate, by dividing the value of the heating energy provided by the rise in temperature, a value representative of the heat capacity of the assembly to be heated formed by the cooking container 2 and the liquid 3 that it contains.

This heat capacity can be expressed in joules per kelvin (J/K). It is also possible to express it in the form of the equivalent volume of water, having a heat capacity equivalent to that of the assembly to be heated. In this case, the equivalent volume of water will most often be an approximation of the real volume of liquid 3 contained in the cooking container 2. Indeed, food liquids most often have a heat capacity close to that of water. . Moreover, the specific heat capacity of water being generally much higher than the specific heat capacity of the materials constituting the cooking vessels, the cooking vessel most often has only a marginal impact on the heat capacity of the together to heat.

The first measurement period during which the heating energy supplied and the temperature rise are measured to calculate the heat capacity of the assembly to be heated can be of fixed duration. It can for example be chosen that this first measurement period lasts one minute, and begins 10 seconds after the user has triggered the boiling program. In other embodiments, the duration of this first measurement period can be variable. It can for example be fixed that the first measurement period lasts the time necessary for the temperature of the liquid 3 to increase by 20°C.

In the situation represented by the figure 2 , the volume of liquid 3 which is boiled is relatively small. During the temperature rise phase 51, the heating power, represented by curve 53, is at the maximum value P _Max , for example equal to 3 kW. The temperature of liquid 3, represented by curve 52, then increases regularly. During this temperature rise phase, the temperature increase ΔT is measured during the first measurement period Δt ₁ , fixed here at one minute. This temperature increase ΔT is relatively large, for example 60° C./min. The heat capacity can then be calculated by the formula Ci = (P _Max × Δt ₁ ) / ΔT = 3,000 J/K, which corresponds approximately to the heat capacity of a volume of water of 0.7 L.

In the situation represented by the picture 3 , the volume of liquid 3 which is brought to the boil is substantially greater. During the temperature rise phase 51, the heating power, represented by curve 53, is at the maximum value P _Max , for example equal to 3 kW. The temperature of liquid 3, represented by curve 52, then increases regularly. During this temperature rise phase, the temperature increase ΔT is measured during the first measurement period Δt ₁ , fixed at one minute. This temperature increase ΔT is relatively low, for example 9° C./min. The heat capacity can then be calculated by the formula C ₂ = (P _Max × Δt ₁ ) / ΔT = 20,000 J/K, which corresponds approximately to the heat capacity of a volume of water of 4.8 L.

Once the heat capacity of the assembly to be heated is calculated, it is stored in memory by the control device 13.

During the temperature rise phase, the heating power supplied can be constant. However, provision may be made for this power to be variable during the temperature rise phase. For example, provision may be made for the power supplied to be reduced when the temperature of the liquid approaches the usual boiling temperature of water. It can also be provided, according to an advantageous characteristic of the invention, that after the thermal capacity of the assembly to be heated has been calculated, the power supplied during the temperature rise phase is adjusted according to this thermal capacity. The power supplied can for example be reduced if the thermal capacity is low.

It is important that the control device 13 detects the boiling of the liquid 3 quickly, to avoid triggering excessive boiling of the liquid 3 by continuing to supply maximum heating power to the assembly to be heated after the liquid has arrived. to a boil. The boiling of this liquid 3 is for example detected by the control device 13 when the temperature of the liquid 3 stops increasing, although the heating power transmitted remains constant.

Preferably, the boiling program implements a boiling detection step during the temperature rise phase, after the implementation of the heat capacity determination step. In the embodiment shown, this boiling detection step continuously measures the rise in the temperature of the liquid 3 during a second, rolling measurement period, and compares this rise in temperature with a threshold value predetermined. Boiling is detected when the rise in temperature during this second measurement period is below the predetermined threshold value.

The transition between the temperature rise phase and the boiling phase appears more or less clearly depending on the speed of the temperature rise, and therefore depending on the heat capacity of the assembly to be heated.

The slowing down of the temperature rise can thus be detected over a relatively short period when the heat capacity of the assembly to be heated is relatively low, as represented by curve 52 on the figure 2 : Indeed, in this case, the temperature rise is rapid during the temperature rise phase, and the contrast with the temperature stagnation of the boiling phase is immediately visible. It can therefore be detected during a short observation period.

On the contrary, when the heat capacity of the assembly to be heated is relatively high, the rise in temperature during the temperature rise phase is slower, as represented by curve 52 on the picture 3 . In this case, the contrast between the temperature rise rate during the temperature rise phase and the temperature stagnation during the boiling phase is lower, and the detection of this stagnation cannot be carried out reliably only over a longer period. In this case, however, it is less important to detect the boiling phase quickly. Indeed, due to the higher heat capacity, the liquid 3 takes longer to reach a strong boil, even if it receives a strong heating power.

According to an advantageous characteristic of the invention, when the thermal capacity of the assembly to be heated is determined by the control device 13, the fixed boiling program, depending on this heat capacity, at least one of the parameters used to detect boiling. Among these parameters, it is advantageous for him to choose the duration of a second measurement period Δt ₂ , which may be shorter for an assembly to be heated having a lower thermal capacity, and longer for an assembly to be heated having a higher heat capacity. For example, in the situation represented by the figure 2 , the second measurement period Δt ₂ can be fixed at 2 seconds, whereas it is fixed at 20 seconds in the situation represented by the picture 3 .

The boiling program can for example set that boiling is obtained if the rise in temperature is less than a given value, for example 0.3° C., during the second measurement period Δt ₂ .

In a possible embodiment, the choice of the parameter used to detect the boiling can be made between several predefined parameters. Thus, the boiling program can use a second measurement period Δt ₂ of 5 seconds when the assembly to be heated has a heat capacity below a threshold of 5,000 J/K, and a second measurement period Δt ₂ of 10 seconds when the assembly to be heated has a thermal capacity greater than this threshold of 5000 J/K.

In other possible embodiments, the parameters used to detect boiling can be variable, continuously or in successive steps, depending on the measured heat capacity. Thus, for example, the duration of the second measurement period Δt ₂ can be proportional to the measured heat capacity.

When the boiling program implemented by the control device 13 detects boiling, it stops supplying the maximum heating power P _Max and implements the boiling maintenance phase. During this boiling maintenance phase, the cooking plate 1 transmits to the assembly to be heated a lower heating power P _Maintenance than during the temperature rise phase, chosen to allow the maintenance of the boiling without boiling too hard, which could cause the liquid to boil over.

According to the invention, the level of heating power P _Maintenance provided during this boiling maintenance phase is set by the boiling program as a function of the heat capacity of the assembly to be heated, which has been determined during the temperature rise phase.

According to one possible embodiment, the boiling program implemented by the control device 13 provides for a plurality of power values P _Hold , each of these values being associated with a heat capacity range of the assembly to be heated. Thus, for example, the boiling program can provide that, during the boiling maintenance phase, the heating power P _Maintenance is fixed at 500 W when the heat capacity is less than 4200J/K, i.e. approximately the heat capacity of one liter of water, the heating power P _Maintenance is set at 1,000 W when the heat capacity is between 4,200 J/K and 8,400 J/K, i.e. approximately between the heat capacity of a liter of water and the heat capacity of two liters of water, and the heating power P _Maintenance is fixed at 1500 W when the heat capacity is greater than 8400 J/K, i.e. greater than the heat capacity of approximately two liters of water.

Of course, it is possible to provide a greater number of different P _Hold power values, or on the contrary only two different P _Hold power values, for this boiling hold phase.

In another embodiment, it is possible for the value of the heating power P _Maintenance during this boiling maintenance phase to be calculated as a function of the heat capacity. It is for example possible for the boiling program to calculate a value of the power P _Hold proportional to the thermal capacity of the assembly to be heated.

This adjustment of the heating power P _Maintenance as a function of the heat capacity of the assembly to be heated, during the boiling maintenance phase, makes it possible to maintain moderate boiling, which does not cause overflow and does not cause excessive evaporation of the liquid.

During the boiling maintenance phase, different events can lead to a change in the temperature of the liquid.

Thus, the introduction into the boiling liquid 3 of food to be cooked can cause a sudden decrease, of several degrees, of the temperature of the liquid 3. The boiling program can provide, advantageously, a specific action when the device control detects a sudden drop in liquid temperature of several degrees, for example greater than 3°C. This program can thus provide, in the event of detection of such a sudden drop in temperature, a brief increase in the heating power to the maximum power, until the temperature of the liquid 3 returns to the boiling temperature previously recorded, or until the temperature of Liquid 3 stabilizes again, indicating that Liquid 3 is boiling. heating to the previously determined boiling level. Such an increase in heating power 54 is visible on the figure 2 , in response to a sudden and significant drop in temperature 55.

It is also possible that, in some cases, the heating power P _Maintain determined for maintaining boiling is slightly insufficient to ensure maintaining boiling. This may in particular be the case when the introduction of food to be cooked in the liquid has significantly increased the heat capacity of the assembly to be heated, compared to the heat capacity which was calculated during the heating phase. temperature.

To avoid a loss of boiling, it can be provided, in an advantageous embodiment, that the boiling program monitors the temperature of the liquid 3 during the boiling maintenance phase, to detect a slight drop and gradual increase in temperature with respect to the boiling temperature, and increases the boiling maintenance heating power as a function of this drop, up to a new heating power P _Maintenance+ . It can for example be provided that a drop of 1°C in relation to the boiling temperature, represented by the reference 56 on the figure 2 , leads to a 100 W increase in the heating power P _Maintenance during the boiling maintenance phase, as represented by reference 57 on the figure 2 .

Preferably, such an increase in power is however limited, to avoid an excessive increase in the heating power in response to a modification of the content of the liquid 3 modifying its boiling point, such as the introduction of salt into water.

The figure 4 schematically represents the steps of a cooking method that can be implemented by the boiling program, according to one embodiment of the invention.

The first step of this method is step 61 for triggering the boiling program. After this first step, a step 62 of preliminary measurements can be implemented, in a preferred embodiment. It is also possible, in other embodiments, for this step 62 to be eliminated, or for it to be carried out at least in part during the temperature rise phase.

In the embodiment represented, at the end of step 62 of preliminary measurements, a temperature rise phase 63 is implemented. During this temperature rise phase 63, the program implements a step 631 of fixing the heating power to a high value P _Max , which may correspond to the maximum power that can be supplied by the hob. This heating power P _Max can be maintained throughout the entire temperature rise phase 63. In other possible embodiments, the heating power may not be constant throughout the entire temperature rise phase 63. However , this heating power supplied to the cooking vessel is known during this temperature rise phase 63.

After this step 631 of setting the heating power to P _Max , the boiling program implements a step 632 of determining the heat capacity of the assembly to be heated, or a value representative of this heat capacity. This step 632 of determining the heat capacity advantageously comprises measuring the heating power and the temperature of the liquid during a first measurement period Δt ₁ and calculating the heat capacity of the assembly to be heated as a function of this measured information.

At the end of step 632 for determining the heat capacity, the program implements a step 633 for detecting boiling. This boiling detection step 633 continues continuously until boiling is detected.

In a preferred embodiment, this boiling detection step 633 comprises a measurement, by the control device 13, of the change in temperature during a second sliding measurement period Δt ₂ , and a comparison of this temperature evolution with a threshold value. Boiling is detected when the change in temperature is below the threshold value. Preferably, the duration of the second measurement period and/or the threshold value are determined as a function of the heat capacity measured in the previous step.

Thus, the figure 5 schematically represents the sub-steps implemented during this boiling detection step 633, according to a preferred embodiment.

This boiling detection step 633 first includes a sub-step 6331 during which the duration of a second measurement period Δt ₂ is fixed. This duration is chosen according to the heat capacity measured previously. Thus, the duration of this second measurement period Δt ₂ will be chosen shorter for a relatively low thermal capacity than for a relatively high thermal capacity. It is thus possible for the duration of this second measurement period Δt ₂ to be proportional to the thermal capacity of the assembly to be heated, or for it to be chosen from among several predetermined duration values, as a function of this thermal capacity. In other embodiments, it is also possible for parameters other than the duration of the measurement period to be set, as a function of the heat capacity measured previously, at the start of step 633 for detecting boiling. .

The boiling detection step 633 then includes a sub-step 6332 during which the change in temperature ΔT during the second measurement period Δt ₂ which has just elapsed is determined. By way of example, if it was previously determined that the second measurement period Δt ₂ , for the thermal capacity of the assembly to be heated, is 10 seconds, this sub-step will consist in determine the evolution ΔT of the temperature of the liquid during the last 10 seconds. Such a determination of the evolution of the temperature during a given period amounts to determining the value of the slope of the progression of temperature, which corresponds to the quotient ΔT / Δt ₂ and can be expressed, for example, in ° C/s.

The boiling detection step 633 then includes a sub-step 6333 during which the change in temperature during the second measurement period Δt ₂ is compared with a threshold value. If this change is less than the threshold value, it is considered that boiling has been reached and step 633 ends. If, on the contrary, the change is greater than the threshold value, it is considered that the change has not been reached and the step 633 of detecting the boiling continues. In practice, the sub-step of determining the change in temperature ΔT during the second measurement period Δt ₂ is repeated until the change is below the threshold value.

The threshold value can be a fixed value, predetermined and independent of the duration of the second measurement period Δt ₂ . It can for example be fixed at 0.2°C. In this case, the slope of the temperature progression corresponding to the threshold value will be variable as a function of the duration of the second measurement period Δt ₂ .

In another possible embodiment, the threshold value can be chosen as a function of the duration of the second measurement period Δt ₂ , for example so that the slope of the temperature progression corresponding to the threshold value is fixed. In still other cases, the threshold value may be chosen according to other criteria, for example according to the program chosen by the user.

When boiling is detected, the boiling program leaves the temperature rise phase 63 and goes to the boiling maintenance phase 64. During this boiling maintenance phase 64, a first step 641 consists of fixing the heating power to a power P _Hold , making it possible to maintain the temperature of the boiling liquid.

Preferably, the value of this power P _Maintain is fixed according to the heat capacity of the assembly to be heated, measured during the phase 63 of temperature rise.

After this step 641 of fixing the heating power to a power P _Maintain , the phase 64 of maintaining boiling can comprise, in advantageous embodiments, a step 642 of regulating the boiling temperature. During this step 642 of regulating the boiling temperature, the temperature of the liquid is monitored so as to maintain it at the boiling temperature. In the event of a drop in temperature, corrective actions can be implemented, such as the injection of greater power for a limited period, or a slight increase in the boiling maintenance power P _Maintenance .

This step 642 of regulating the boiling temperature can be extended until step 643 of the end of the boiling program, which can for example correspond to a press by the user on an end of program control button. boiling.

The steps of this method, or boiling program, can be implemented by a suitable electronic circuit or by a computer program that can be implemented by the control device 13 of the cooking plate 1.

Claims (13)

1. A cooking hob (1) suitable for heating a cooking vessel (2) containing a liquid (3), said cooking hob (1) being suitable for receiving a measurement of the temperature of the liquid (3) contained in said cooking vessel (2), said cooking hob (1) implementing a cooking program comprising the steps of:

   - providing a known heating power to said cooking vessel, during a temperature rise phase (63),

   - determining a value representative of the heat capacity of an assembly to be heated comprising said cooking vessel (2) and its contents, by dividing the heating energy provided during a first measurement period comprised in said temperature rise phase, by the rise in temperature (63) of said liquid during said first measurement period, and

   - detecting the boiling of said liquid (3), corresponding to the end of said temperature rise phase and the start of a boiling maintenance phase, said cooking hob being characterized in that the cooking program comprises a step consisting of

   - providing a heating power, during said boiling maintenance phase (64), at a power level selected based upon said value representative of the heat capacity of said assembly to be heated, determined during said temperature rise phase (63).
2. The cooking hob (1) according to the preceding claim, characterized in that, during the implementation of said cooking program, said cooking hob (1) detects the boiling of said liquid (3), after said first measurement period, by determining that the rise in temperature of said liquid (3) during a second measurement period comprised in said temperature rise phase (63) is below a threshold value.
3. The cooking hob (1) according to the preceding claim, characterized in that the duration of said second measurement period is selected based upon said value representative of said heat capacity of said assembly to be heated, determined previously.
4. The cooking hob (1) according to any one of claims 2 and 3, characterized in that said threshold value is a predetermined fixed value, independent of said value representative of said heat capacity of said assembly to be heated and of the duration of said second measurement period.
5. The cooking hob (1) according to any one of claims 2 and 3, characterized in that said threshold value is determined based upon said value representative of said heat capacity of said assembly to be heated and/or of the duration of said second measurement period.
6. The cooking hob (1) according to any one of the preceding claims, characterized in that said heating power level during said boiling maintenance phase is selected from several predetermined values, each of said predetermined values being associated with a range of values representative of the heat capacity of said assembly to be heated.
7. The cooking hob (1) according to any one of the preceding claims, characterized in that, during said boiling maintenance phase (64), said cooking hob (1) detects a drop in the temperature of said liquid (3), and modifies said heating power level in order to regulate the temperature of said liquid (3) over the boiling point.
8. The cooking hob (1) according to any one of the preceding claims, characterized in that it consists of an induction plate, suitable for producing variable magnetic fields capable of generating eddy currents in said cooking vessel (2), in order to heat said cooking vessel (2) by the Joule effect.
9. A cooking system characterized in that it comprises:

   - a cooking hob (1) according to any one of claims 1 to 8,

   - a cooking vessel (2), and

   - a device for measuring the temperature of the contents of said cooking vessel (2).
10. The cooking system according to the preceding claim, characterized in that said device for measuring the contents of the cooking vessel (2) comprises a temperature probe (4) in contact with the contents of said cooking vessel (2).
11. A cooking process, implemented by a cooking system comprising a cooking hob (1), a cooking vessel (2) containing a liquid (3), and a device for measuring the temperature of said liquid (3) contained in said cooking vessel (2), characterized in that said cooking process comprises the following steps:

    - providing, by said cooking hob (1), a known heating power to said cooking vessel (2), during a temperature rise phase (63),

    - determining a value representative of the heat capacity of an assembly to be heated comprising said cooking vessel (2) and its contents, by dividing the heating energy provided during a first measurement period comprised in said temperature rise phase (63), by the rise in temperature of said liquid during said first measurement period,

    - detecting the boiling of said liquid (3), corresponding to the end of said temperature rise phase (63) and the beginning of a boiling maintenance phase (64),

    - providing, by said cooking hob (1), a heating power, during said boiling maintenance phase (64), at a power level selected based upon said value representative of the heat capacity of said assembly to be heated, determined during said temperature rise phase (63).
12. The cooking process according to the preceding claim, characterized in that said step of detecting the boiling of said liquid (3) is implemented after said first measurement period, and comprises:

    - a sub-step (6331) of setting the duration of a second measurement period, based upon said value representative of the heat capacity of said assembly to be heated,

    - a sub-step (6332) of determining the evolution of the temperature of said contents during said second measurement period,

    - a sub-step (6333) of comparing said evolution of the temperature of said contents during said second measurement period with a threshold value.
13. A computer program comprising instructions which, when the program is executed by a control device (13) of a cooking hob (1), lead the latter to implement a cooking process according to any one of claims 11 and 12.

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