EP3890432A1 - Hob comprising an improved cooking programme, cooking system, cooking method and corresponding programme - Google Patents

Abstract

The invention relates to a cooking plate (1) suitable for heating a cooking vessel (2) containing a liquid (3) and suitable for receiving a measurement of the temperature of this liquid, the cooking plate (1) implementing a cooking program comprising the steps consisting in: - supplying a known heating power to the cooking vessel (2), during a temperature rise phase, - determining a value representative of the thermal capacity of an assembly to heater comprising the cooking vessel (2) and its contents, by dividing the heating energy supplied during a first measurement period included in the temperature rise phase, by the rise in temperature of the liquid during the first measurement period, - detect the boiling of the liquid (3), corresponding to the end of the temperature rise phase and the start of a boiling maintenance phase, - provide heating power, during this phase of maintaining boiling, at a power level chosen as a function of the value representative of the thermal capacity of the assembly to be heated, determined during the temperature rise phase.

Description

Field of the invention

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

It particularly relates to such a cooking plate comprising a program specifically adapted to bring a liquid to the 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 contents of the cooking vessel.

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

It relates very particularly to such a cooking process suitable for bringing a liquid to the 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 for implementing such a method.

Prior art

Several types of cooking plates are known, intended for heating food contained in a cooking receptacle such as a saucepan.

Among these hotplates, some, commonly called hotplates, transmit 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 vessel, causing this vessel to be heated by the Joule effect.

The present invention can be applied to the various 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.

Hotplates 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, the aim is generally to obtain the boiling of the liquid as quickly as possible, while providing maximum heating power to the cooking vessel.

Once boiling, maintaining the liquid at the boiling temperature does not generally 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 is lower.

Indeed, if the power supplied by the hotplate 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 results in an evaporative loss of the liquid used for cooking, and a risk of the liquid overflowing. This risk of overflow is particularly common when a food containing starch, such as pasta or rice, has been cooked in the boiling liquid.

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

It is known to measure the temperature inside the cooking vessel. Thus, the document EP 1 037 508 A1 shows a system composed of a cooking plate and a cooking receptacle in which is placed a temperature probe capable of communicating to the cooking plate information on the temperature of a liquid contained in the cooking receptacle. If it makes it possible to know the temperature of the liquid, such a probe does not however make it possible to determine what the boiling point of this liquid is. Indeed, the boiling temperature of a liquid can vary depending on the nature of this liquid. For example, it will not be the same for water, salt water, milk, etc. Furthermore, this boiling temperature varies as a function of atmospheric pressure, and therefore of 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 2020 826 A1 , to determine that a liquid is boiling by the detection of the vibrations generated by the 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 temperature when the temperature measured by a sensor integrated in the cooking plate remains stable for a prolonged period, despite a significant energy input. However, such a method only makes it possible to detect the boiling after having supplied a large amount of energy to the boiling liquid, which risks causing a strong boiling and therefore an overflow.

When a boil 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 inform, by means of an appropriate control of the cooking plate, the volume of liquid that he wishes to keep at the boil, 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. In addition, this adapted heating power may vary during cooking, in particular when the content of the cooking receptacle varies during cooking, for example if the user has introduced food into the boiling liquid.

Objectives of the invention

The object of the present invention is 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 cooking method, which make it possible to bring to the boil rapidly a liquid contained in a cooking vessel, and to keep this liquid at a relatively low boil.

Another objective 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 the boil and to maintain its boiling while generating relatively low energy consumption.

Another objective 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 too strong a boiling of a liquid brought to the boil.

Another objective 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 the 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 below, are achieved with the aid of a cooking plate, able to heat a cooking vessel containing a liquid, this cooking plate being able to receive a measurement. the temperature of the liquid contained in the cooking receptacle, 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,
• provide heating power, during the boiling maintenance phase, at a power level chosen as a function of the value representative of the thermal capacity of the assembly to be heated, determined during the rise phase temperature.

The heating energy supplied by the hob 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 as a function of the thermal capacity of the assembly to be heated, and therefore, in practice, as a function of the quantity of liquid which should be kept at a boil. This adjustment of the heating power advantageously makes it possible to maintain the boiling at a moderate level, without superfluous power input. The low bubbling caused by this boiling very significantly limits the risk of the liquid overflowing out of the cooking vessel.

It should be noted that, according to the invention, the thermal 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 thermal 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 onset of boiling, to avoid excessive boiling of the liquid.

Advantageously, during the implementation of the cooking program, the cooking plate detects the boiling of the liquid, after the first measurement period, by determining that the rise in the 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 rapidly detect boiling, which is characterized in particular by temperature stability despite the addition of heating power. The rapid detection of boiling makes it possible to quickly adjust the heating power to avoid too much boiling of the liquid.

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

Thus, the detection of the boiling can be carried out with optimum efficiency, in particular when the small quantity of liquid increases the risks of too strong boiling if an 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 thermal 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 the 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 level of heating power during the boiling maintenance phase is chosen from several predetermined values, each of the predetermined values being associated with a range of values representative of the thermal capacity of the set to heat.

Preferably, during the maintaining boiling phase, the hotplate 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, able to produce variable magnetic fields capable of generating induced eddy currents in the cooking vessel, to heat the cooking vessel by Joule effect.

Such hotplates allow precise control of the heating power, with very low thermal inertia. They thus allow the efficient 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 content 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 in isolation 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 cooking plate of a known heating power to the cooking vessel, during a temperature rise phase,
• determining 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 rise phase in 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 cooking plate of a heating power, during the phase of maintaining boiling, at a power level chosen as a function of 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 carried out 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 thermal capacity of the assembly to be heated,
• a sub-step for determining the evolution of the temperature of the liquid during the second measurement period,
• a sub-step of comparing the evolution of the temperature of the liquid during the second measurement period with a threshold value.

Such a cooking process can advantageously have the various characteristics described in relation to the cooking plate, these characteristics being taken in isolation 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 plate, 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 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 the boil and then maintained at boiling point by a method according to one embodiment of the invention, and of the heating power supplied to this liquid;
• [ Fig. 3 ] the figure 3 is a set of curves representative of the temperature of a second volume of liquid brought to the boil and then maintained at boiling point 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 substeps of one of the process steps of the figure 4 ;
• [ Fig. 6 ] the figure 6 is a set of curves representative of the temperature of a liquid brought to the boil and the temperature of the outside of the cooking vessel containing this liquid.

Detailed description of embodiments of the invention

The figure 1 schematically shows, in cross-sectional view, a system according to one embodiment which comprises a cooking plate 1 supporting a cooking receptacle 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 supplied, a variable magnetic field capable of generating induced eddy currents in a cooking vessel 2 placed on the upper plate 11. These induced currents by Joule effect cause the cooking vessel to heat up 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 the user. 'via the hob control buttons (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 electric 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 electric 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 capable of precisely measuring, at any time, the power received by the cooking vessel 2. Thus, if the hob 1 is a gas combustion hob, it may be equipped with a flowmeter to measure the volume of gas burnt to heat the cooking pot. The heating power, which is proportional to the flow rate of burnt gas, for a given gas quality, can be known with sufficient precision.

The invention is however of particular interest in the case of induction hobs, 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 receptacle 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 cooking plate on which they are heated.

The cooking vessel 2 is filled with a liquid 3 intended to be heated to 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 not placed in the liquid until after it has come to a boil.

In the remainder of the present description, it will be considered that the cooking receptacle 2 and the contents of this receptacle constitute a “set to be heated”. This assembly to be heated of course only includes the parts of the cooking receptacle intended to rise in temperature, and not the parts of this receptacle which are thermally insulated, such as for example the pan handles.

In the embodiment shown, 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 shown comprises radio communication equipment, and is thus capable of communicating by radio the temperature values that it reads to the cooking plate 1, which for this includes suitable radio communication equipment 14, connected to the control device 13.

Thus, the control device 13 can know, at all times, both the electrical power values supplied to the induction coils 12, and therefore the heating power, and the temperature of the liquid 3 supplied by the 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 is known per se to a person skilled in the art. trade, 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 therefrom.

The implementation of the invention requires that the equipment for measuring the temperature of the liquid 3 performs the measurement of the temperature of the liquid 3 accurately and in real time. In particular, it is important that the temperature measurement is 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 is 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 relates only to the 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 d. 'error of less than 1 ° C, and with a resolution of 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 in order 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 in a sufficiently precise manner to implement the invention.

For example, the figure 6 represents the temperature measurement curves recorded by several measuring devices during the heating of a cooking vessel filled with water, to which a constant heating power is applied from time 0. Curve 91 represents the measurement of temperature of the liquid carried out 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, carried out by a probe placed in the cooking plate. It is clearly noted that the probe placed in the cooking plate does not allow the temperature of the water to be measured. Thus, it measures 100 ° C when the liquid has already largely exceeded its boiling point and it subsequently measures a temperature largely exceeding 100 ° C. Such a measurement of the temperature of the outside of the cooking receptacle 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 exterior of the cooking vessel are therefore necessarily very different from the solution of the invention, and generally do not allow detection of the boiling fast enough to avoid strong boiling, risking the liquid overflowing.

According to the invention, the cooking plate 1 is configured to apply a particular cooking program to the assembly to be heated constituted by the cooking receptacle 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 to initiate this boiling program, or by the choice of this program by the user in an interactive menu.

This boiling program controls the hotplate 1 so that it heats the cooking vessel 2 during two successive phases: a rising phase. temperature, and a boiling maintenance phase. The figures 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 figure 2 , the volume of liquid 3 which is brought to the boil is relatively small. In the situation represented by the figure 3 , this volume of liquid 3 which is brought to the boil is appreciably greater.

When the user initiates the boiling program, it is possible, in some embodiments, for preliminary measurements to be taken 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, may for example be intended to check that a suitable cooking vessel 2 is correctly placed on the cooking plate 1, that the temperature probe 4 is correctly placed in this cooking vessel 2, or that the temperature of the liquid 3 in the cooking vessel 2 is not too high to engage the boiling program.

The boiling program begins, possibly after the preliminary measurements, by implementing the temperature rise 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 hob 1 provides maximum heating power to the heater. cooking vessel, 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 permitted by the cooking plate 1. The objective of this temperature rise phase is in fact to rapidly obtain the boiling liquid 3.

During this temperature rise phase, the boiling program implements a step of determining the thermal capacity of the assembly to be heated, or a value representative of this thermal capacity. For the implementation of this step, the control device 13 measures, during a first measurement period, the temperature rise 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 supplied by the rise in temperature, a value representative of the thermal capacity of the assembly to be heated formed by the cooking vessel 2 and the liquid 3 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 thermal 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 actual volume of liquid 3 contained in the cooking vessel 2. In fact, food liquids most often have a thermal capacity close to that of water. . Furthermore, since the specific heat capacity of the water is generally much greater than the specific thermal capacity of the materials constituting the cooking vessels, the cooking vessel usually only has a marginal impact on the thermal capacity of the set to heat.

The first measurement period during which the heating energy supplied and the temperature rise are measured to calculate the thermal 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 brought to the boil 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 the liquid 3, represented by the 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 C ₁ = (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 figure 3 , the volume of liquid 3 which is brought to the boil is appreciably 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 the liquid 3, represented by the 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 small, 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 water volume of 4.8 L.

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

During the temperature rise phase, the heating power supplied can be constant. However, provision can be made for this power to be variable during the temperature rise phase. For example, provision can be made for the power supplied to be reduced when the temperature of the liquid approaches the usual boiling point 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 as a function of 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 an excessive boiling of the liquid 3 by continuing to provide 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 transmitted heating power 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, sliding measurement period, and compares this rise in temperature to a threshold value. predetermined. Boiling is detected when the temperature rise during this second measurement period is less than 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 thermal capacity of the assembly to be heated.

The slowing of the rise in temperature can thus be detected over a relatively short period when the thermal capacity of the assembly to be heated is relatively low, as shown by curve 52 on the diagram. figure 2 : in fact, 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 thermal capacity of the assembly to be heated is relatively high, the rise in temperature during the temperature rise phase is slower, as shown by curve 52 on the diagram. figure 3 . In this case, the contrast between the rate of temperature rise 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 from reliably than over a longer period. In this case, however, it is less important to quickly detect the boiling phase. Indeed, due to the higher thermal capacity, the liquid 3 takes longer to reach a strong boiling, 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 stronger heat capacity. For example, in the situation represented by the figure 2 , the second measurement period Δt ₂ can be fixed at 2 seconds, while it is fixed at 20 seconds in the situation represented by the figure 3 .

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

In one possible embodiment, the choice of the parameter used to detect the boiling can be made among 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 thermal capacity below a threshold of 5000 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 5,000 J / K.

In other possible embodiments, 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 thermal capacity.

When the boiling program implemented by the control device 13 detects the boiling, it stops providing the maximum heating power P _Max and implements the phase of maintaining the boiling. During this phase of maintaining the boiling, the cooking plate 1 transmits to the assembly to be heated a heating power P _Maintain lower than during the phase of temperature rise, chosen to allow the maintenance of the boiling without causing too much boiling, which may cause the liquid to overflow.

According to the invention, the level of P _Maintain heating power supplied during this boiling maintenance phase is set by the boiling program as a function of the thermal 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 _Maintain, each of these values being associated with a range of thermal capacity of the assembly to be heated. Thus, for example, the boiling program can provide that, during the phase of maintaining the boil, the heating power P _Maintain is fixed at 500 W when the thermal capacity is less than 4200J / K, that is to say approximately the thermal capacity of one liter of water, the heating power P _Maintain is fixed at 1000 W when the thermal capacity is between 4,200 J / K and 8,400 J / K, i.e. approximately between the thermal capacity of a liter of water and the thermal capacity of two liters of water, and the heating power P _Maintain is fixed at 1500 W when the thermal capacity is greater than 8 400 J / K, i.e. higher than the thermal capacity by approximately two liters of water.

Of course, it is possible to provide a larger number of _{different P Maintain} power values, or on the contrary only two _{different P Maintain} power values, for this boiling maintenance phase.

In another embodiment, it is possible that the value of the heating power P _Maintain during this phase of maintaining boiling is calculated as a function of the thermal capacity. It is for example possible that the boiling program calculates a value of the power P _Maintain proportional to the thermal capacity of the assembly to be heated.

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

During the maintain boiling phase, various events can cause the temperature of the liquid to change.

Thus, the introduction into the boiling liquid 3 of food to be cooked can cause a sudden decrease, of several degrees, in the temperature of the liquid 3. The boiling program can advantageously provide for a specific action when the device control unit detects a sudden drop in liquid temperature of several degrees, for example above 3 ° C. This program can thus provide, in the event of such a sudden drop in temperature being detected, a brief increase in the heating power to maximum power, until the temperature of liquid 3 returns to the previously boiling temperature. recorded, or until the temperature of liquid 3 stabilizes again, which indicates the boiling of this liquid 3. When the boiling program detects the return of liquid 3 to boiling, it returns the power heating to the previously determined maintain boiling level. Such an increase in heating power 54 is visible on the figure 2 , in reaction to a sudden and significant drop in temperature 55.

It is also possible that, in certain cases, the heating power P _Maintain determined for the maintenance of the boiling is slightly insufficient to ensure the maintenance of the boiling. This may in particular be the case when the introduction of food to be cooked into the liquid has significantly increased the thermal capacity of the assembly to be heated, compared to the thermal capacity which was calculated during the rise 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 phase of maintaining the boiling, to detect a slight drop. and the temperature gradually relative to the boiling temperature, and increases the heating power for maintaining the boiling as a function of this drop, up to a new heating power P _{Maintain +} . For example, it can be expected that a drop of 1 ° C relative to the boiling point, represented by the reference 56 on the figure 2 , results in an increase of 100 W in the heating power P _Maintain during the boiling maintenance phase, as shown by reference 57 on the figure 2 .

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

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

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

In the embodiment shown, at the end of the 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 at a _{high P Max} value, which may correspond to the maximum power that can be supplied by the cooking plate. This heating power P _Max can be maintained throughout the temperature rise phase 63. In other possible embodiments, the heating power may not be constant throughout the temperature rise phase 63. However, however, the heating power may not be constant. , this heating power supplied to the cooking vessel is known during this temperature rise phase 63.

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

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

In a preferred embodiment, this step 633 of detecting the boiling 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 change in temperature 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 thermal capacity measured in the previous step.

So 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 firstly comprises a sub-step 6331 during which the duration of a second measurement period Δt ₂ is fixed. This duration is chosen according to the thermal capacity measured previously. Thus, the duration of this second measurement period Δt ₂ will be chosen to be 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 that other parameters than the duration of the measurement period are set, depending on the heat capacity measured previously, at the start of the step 633 of detecting the boiling. .

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

The boiling detection step 633 then comprises 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 less than the threshold value.

The threshold value can be a fixed, predetermined value independent of the duration of the second measurement period Δt ₂ . It can for example be set 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 yet other cases, the threshold value may be chosen as a function of other criteria, for example as a function of the program chosen by the user.

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

Preferably, the value of this _holding power P is set as a function of the thermal capacity of the assembly to be heated, measured during the temperature rise phase 63.

After this step 641 of fixing the heating power to a _maintaining power P, the phase 64 of maintaining the 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 taken, such as injecting more power for a limited period of time, or a slight increase in the power to maintain boiling P _Maintain .

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

The steps of this process, 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)

Cooking plate (1) suitable for heating a cooking vessel (2) containing a liquid (3), said cooking plate (1) being suitable for receiving a measurement of the temperature of the liquid (3) contained in said cooking vessel (2), characterized in that said cooking plate (1) implements 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 thermal capacity of an assembly to be heated comprising said cooking vessel (2) and its contents, by dividing the heating energy supplied during a first measurement period included in said rise phase in temperature, by the temperature rise (63) of said liquid during said first measurement period, - detecting the boiling of said liquid (3), corresponding to the end of said temperature rise phase and the start of a boiling maintenance phase, - supplying a heating power, during said boiling maintenance phase (64), at a power level chosen as a function of said value representative of the thermal capacity of said assembly to be heated, determined during said heating phase temperature rise (63). Cooking plate (1) according to the preceding claim, characterized in that , during the implementation of said cooking program, said cooking plate (1) detects the boiling of said liquid (3), after said first period of measuring, by determining that the rise in temperature of said liquid (3) during a second measuring period included in said temperature rise phase (63) is below a threshold value. Cooking plate (1) according to the preceding claim, characterized in that the duration of said second measurement period is chosen as a function of said value representative of said thermal capacity of said assembly to be heated, determined previously. Cooking plate (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 thermal capacity of said assembly to be heated and of the duration of said second measurement period. Cooking plate (1) according to any one of claims 2 and 3, characterized in that said threshold value is determined as a function of said value representative of said thermal capacity of said assembly to be heated and / or of the duration of said second period of measurement. Hob (1) according to any one of the preceding claims, characterized in that said heating power level during said boiling maintenance phase is chosen from several predetermined values, each of said predetermined values being associated with a range of values representative of the thermal capacity of said assembly to be heated. Cooking plate (1) according to any one of the preceding claims, characterized in that , during said phase of maintaining the boiling point (64), said cooking plate (1) detects a drop in the temperature of said liquid (3), and modifies said heating power level to regulate the temperature of said liquid (3) to the boiling temperature. Cooking plate (1) according to any one of the preceding claims, characterized in that it consists of an induction plate, capable of producing variable magnetic fields capable of generating induced eddy currents in said cooking vessel ( 2), to heat said cooking vessel (2) by Joule effect. Cooking system characterized in that it comprises: - a cooking plate (1) according to any one of claims 1 to 8, - a cooking vessel (2), and - equipment for measuring the temperature of the contents of said cooking vessel (2). Cooking system according to the preceding claim, characterized in that said equipment for measuring the content of the cooking vessel (2) comprises a temperature probe (4) in contact with the content of said cooking vessel (2). Cooking method, implemented by a cooking system comprising a cooking plate (1), a cooking vessel (2) containing a liquid (3), and equipment for measuring the temperature of said liquid (3) contained in said cooking vessel (2), characterized in that said cooking method comprises the following steps: - the supply by said cooking plate (1) of a known heating power to said cooking vessel (2), during a temperature rise phase (63), - determining a value representative of the thermal capacity of an assembly to be heated comprising said cooking vessel (2) and its contents, by dividing the heating energy supplied during a first measurement period included in said temperature rise phase (63), by the temperature rise of said liquid during said first measurement period, - the detection of the boiling of said liquid (3), corresponding to the end of said temperature rise phase (63) and to the start of a boiling maintenance phase (64), - the supply by said cooking plate (1) of a heating power, during said boiling maintenance phase (64), at a power level chosen as a function of said value representative of the thermal capacity of said assembly to be heated, determined during said temperature rise phase (63). Cooking method according to the preceding claim, characterized in that said step of detecting the boiling of said liquid (3) is carried out after said first measurement period, and comprises: - a sub-step (6331) of fixing the duration of a second measurement period, as a function of said value representative of the thermal capacity of said assembly to be heated, - a sub-step (6332) of determining the evolution of the temperature of said content during said second measurement period, a sub-step (6333) of comparing said change in the temperature of said content during said second measurement period with a threshold value. Computer program comprising instructions which, when the program is executed by a control device (13) of a cooking plate (1), lead the latter to implement a cooking method according to any one of claims 11 and 12.

Images