EP2487989B1 - Method for adjusting the temperature of a cooking item - Google Patents

Description

The present invention relates to the thermal regulation of a culinary article, particularly in the field of household appliances.

• établir une valeur pour une température de consigne à atteindre,
• alimenter les moyens de chauffe de l'article culinaire, et
• mesurer la température de l'article culinaire.

More specifically, according to a first of its objects, the invention relates to a method for regulating the temperature of a culinary article heated by variable heating means, the method comprising the steps of:

• establish a value for a target temperature to be reached,
• feeding the heating means of the culinary article, and
• measure the temperature of the culinary article.

Such a method is known to those skilled in the art, and there are many documents of the state of the prior art in this field, the regulation of the feed of the heating means of the culinary article being for example dependent on measuring the temperature of the culinary article.

The document EP-A-2,063,180 discloses a method for controlling the temperature of a cooking appliance of the cooking piano type. This appliance includes an oven, heating elements, a thermal sensor, a thermostat and a control unit. The oven is heated to a predetermined temperature (Tg) (100 ° C) for a time interval ti. The temperature (Tg) being reached, the heating elements are cut during a period t2 and t3 to induce the cooling of the oven to a threshold temperature Ts (80 ° C). It follows a period t4 during which the heating elements are reactivated at maximum power in a constant duty cycle, to re-heat the oven. The documents WO 2008/117910 A1 , DE 41 04 677 A1 and US 2009/0294434 A1 describe other methods of regulating the temperature of a culinary article with a set temperature and a threshold temperature.

However, the regulation of the temperature must be carried out so on the one hand to heat the culinary article quickly, and on the other hand not to degrade the content food item if the temperature of it becomes too important.

• comparer la température mesurée de l'article culinaire à la valeur d'une température seuil et à la valeur de la consigne de température, et
• délivrer par les moyens de chauffe une quantité d'énergie dépendante
  • o de l'écart entre la température mesurée et la valeur de la température seuil, et
  • o de l'écart entre la température mesurée et la valeur de la consigne de température.

With this objective in view, the method according to the invention, moreover, in accordance with the preamble cited above, is essentially characterized in that it further comprises the steps of:

• comparing the measured temperature of the culinary article with the value of a threshold temperature and the value of the temperature setpoint, and
• delivering by the heating means a quantity of dependent energy
  • o the difference between the measured temperature and the value of the threshold temperature, and
  • o the difference between the measured temperature and the value of the temperature set point.

Thanks to these double thresholding characteristics, it is possible to regulate the heating power delivered, so that the rise in temperature of the culinary article is very fast but limited.

Thus, for the temperature rise phase of the culinary article, as long as the measured temperature of the culinary article is lower than the value of the threshold temperature, the amount of energy delivered to (or delivered by) the means of heating is a constant value in time equal to a proportion of the maximum value that can be supplied to said heating means (or that can provide said heating means).

Thanks to this open-loop operation, the temperature rise of the culinary article is carried out rapidly.

Preferably, the proportion of the maximum value that can be supplied to said (or that can provide said) heating means depends on the value of the set temperature.

With this feature, the risk of exceeding the target temperature that the culinary article must reach is limited.

For the regulation phase of the target temperature that the culinary article must reach, it is advantageously provided that at least at the first exceeding of the threshold temperature by the measured temperature of the culinary article, the quantity energy delivered to (or by) the heating means is variable and slaved to the difference between the measured temperature and the value of the set temperature.

Preferably, the temperature is measured in a succession of times, the quantity of energy delivered by the (or delivered to) the heating means in a time (t) being furthermore enslaved to the quantity of energy delivered by the (or delivered to the heating means in a preceding time (t-1).

With this feature, the higher the temperature of the culinary article approaches the set temperature, the lower the amount of energy delivered per unit of time by the heating means, which limits the risk of exceeding the temperature of the deposit, therefore of degradation of the content of the culinary article.

In one embodiment, provision is made to regulate the amount of energy delivered by the heating means by regulating the power supply of said heating means.

An electronic control circuit makes it possible to easily modify the electrical supply signal of the heating means.

In one embodiment, the heating means are powered by a periodic square supply signal, the amount of energy delivered by the heating means being regulated by the value of the duty cycle of said periodic signal.

Thanks to this configuration, the heating energy is regulated in a very simple and very fast way.

In one embodiment, there is provided a step of initializing the amount of energy delivered by the heating means to a minimum or zero value at the first exceeding of at least the threshold temperature by the measured temperature of the culinary article.

With this configuration, it is possible to use the thermal inertia of the culinary article and / or heating means to slow the rise in temperature of the culinary article.

Preferably, there is provided a step of cutting the supply of the heating means if the measured temperature of the culinary article is greater than the set temperature.

Thanks to this characteristic, the temperature of the culinary article is rapidly stabilized around the set temperature.

• un capteur de température pour mesurer la température de l'article culinaire,
• des moyens de chauffe de l'article culinaire,
• des moyens de régulation de l'alimentation électrique des moyens de chauffe,
• des moyens d'établissement d'une valeur de température de consigne à atteindre,
• un calculateur configuré pour
  • ∘ comparer la température mesurée de l'article culinaire à la valeur d'une température seuil et à la valeur de la consigne de température, et
  • o commander aux moyens de chauffe de délivrer une quantité d'énergie dépendante
    • ▪ de l'écart entre la température mesurée et la valeur de la température seuil, et
    • ▪ de l'écart entre la température mesurée et la valeur de la consigne de température.

According to another of its objects, the invention also relates to a device for regulating the temperature of a culinary article, capable of implementing the method according to the invention, and comprising:

• a temperature sensor for measuring the temperature of the culinary article,
• heating means of the culinary article,
• means for regulating the power supply of the heating means,
• means for setting a target temperature value to be reached,
• a calculator configured for
  • ∘ comparing the measured temperature of the culinary article with the value of a threshold temperature and the value of the temperature setpoint, and
  • o control the heating means to deliver a quantity of energy dependent
    • ▪ the difference between the measured temperature and the value of the threshold temperature, and
    • ▪ the difference between the measured temperature and the value of the temperature set point.

Finally, the invention also relates to a computer program, comprising program code instructions for executing the steps of the method according to the invention, when said program is executed on a computer.

• la figure 1 illustre un mode de réalisation du dispositif selon l'invention,
• la figure 2 illustre l'évolution synchrone de la température mesurée et de la quantité d'énergie délivrée aux moyens de chauffe grâce à l'invention,
• la figure 3 illustre l'évolution de la température mesurée lors de la mise en oeuvre de l'invention, en présence d'une perturbation,
• la figure 4 illustre un rapport cyclique de la quantité d'énergie délivrée aux moyens de chauffe, et
• la figure 5 illustre un mode de réalisation du procédé selon l'invention.

Other characteristics and advantages of the present invention will emerge more clearly on reading the following description given by way of illustrative and nonlimiting example and with reference to the appended figures in which:

• the figure 1 illustrates an embodiment of the device according to the invention,
• the figure 2 illustrates the synchronous evolution of the measured temperature and the quantity of energy delivered to the heating means by means of the invention,
• the figure 3 illustrates the evolution of the temperature measured during the implementation of the invention, in the presence of a disturbance,
• the figure 4 illustrates a duty cycle of the amount of energy delivered to the heating means, and
• the figure 5 illustrates an embodiment of the method according to the invention.

In the field of thermal regulation of a culinary article, particularly in the field of household appliances, a user determines a target temperature to be reached to heat the food content of the culinary article at this set temperature, and optionally maintain it for a predetermined time.

From a culinary point of view, it is essential not to degrade or even burn the food contained in the culinary article. It is therefore necessary to control the temperature of it. For this purpose, it is proposed to control the heating thereof by modulating the energy sent to the heating means of said article.

To simplify the description which follows, reference is made to a removable culinary article with respect to the means for heating and regulating the temperature. Those skilled in the art knows, however, deport all or part of the heating and regulating means in the culinary article.

On the basis of a conventional device for regulating the temperature of a culinary article 10, a temperature sensor 13 (for example a CTN for a Negative Temperature Coefficient) is proposed here for measuring the temperature T_CTN of the culinary article. . The CTN is for example plated below the culinary article 10 so as to be the closest to the heated food ( figure 1 ). It can also be deported, that is to say integrated into the culinary article.

The heating of the culinary article 10 is carried out by heating means 11 (variable) of the culinary article, for example a heating resistor, whose heating energy distributed by the latter depends on the electrical power which it is provided. The heating can vary.

The value of a setpoint temperature T_set to reach, which is called for convenience of language indifferently temperature setpoint, setpoint temperature, or setpoint, is determined by a user thanks to a human machine interface HMI (not shown), coupled to a computer described below.

Preferably, the value of the setpoint is displayed on a display screen of the HMI. It is variable and determined by the user, for example by pressing the buttons of the HMI for incrementing or decrementing the value of the setpoint according to a preset step, for example 5 ° C.

The heating time is also preferably programmable. It is saved, like the instruction, in a memory. Once the user has chosen the heating time and the set point, the heating starts, for example, by pressing an HMI validation button. An electronic circuit coupled or comprising the computer then supplies electrical energy to the heating means 11. Preferably, a visual indicator (light) and / or sound indicates that the heating is implemented. Preset time and temperature programs may also be available, the HMI allowing the user to select one of them.

For reasons of safety, it is desirable to further provide means for detecting the presence (not shown) of content in the cooking utensil 10, to cut the heating if the contents thereof is empty. For example an infrared sensor, a weight sensor or other means known to those skilled in the art.

The regulation of the heating energy is implemented by means 12 for regulating the power supply of the heating means 11. These regulating means 12 are connected to the temperature sensor CTN and to the heating means 11, and comprise for example a computer (microprocessor or other).

It is planned to regulate the energy supplied by the heating means 11 by regulating the electric power supply, supplied at the input thereof.

In operation, the value of the heating energy, that is to say the energy distributed by the heating means 11, or the electrical energy supply thereof is controlled at the same time at the temperature T_CTN of the culinary article 10 measured by the sensor 13 and the value of the temperature setpoint T_commands.

That is to say that the computer compares the measured temperature T_CTN of the culinary article 10 to the value of the set temperature T_commands and orders the heating means 11 to deliver a quantity of energy dependent on the difference between the measured temperature T_CTN and the value of the temperature setpoint T_set.

In contrast to the prior art, it is furthermore provided that the value of the heating energy or the electrical energy supply of the heating means 11 is also controlled at the same time at the temperature T_CTN of the article culinary 10 measured by the sensor 13 and the value of a threshold temperature T_seuil, whose T_seuil value is lower than that of the set temperature T_sign.

That is to say that the calculator further compares the measured temperature T_CTN of the culinary article 10 with the value of the threshold temperature T_seuil, and commands the heating means 11 to deliver a quantity of energy dependent in addition to the difference between the measured temperature T_CTN and the value of the threshold temperature T_seuil.

The value of the threshold temperature T_seuil influences the speed of the rise in temperature of the culinary article (the more T_seuil is close to T_commands, the higher the temperature rise is fast but the risk of exceeding the set point is high), as described later.

In one embodiment, it is expected that the value of the threshold temperature T_seuil is slaved to that of the setpoint temperature T_set.

It can be provided that the threshold temperature T_seuil is a fixed proportion of the set temperature, for example T_seuil = 60% T_commits.

It is also possible to predict that the value of the proportion depends on the value of the setpoint T_set.

for example

• T_seuil = X% T_book if
  • T_set <T1 ° C or
  • T_set between T1_1 ° C and T1_2 ° C, and
• T_seuil = Y% T_book if
  • T_set> T2 ° C, or if
  • T_set between T2_1 ° C and T2_2 ° C.

For example, for a set point of between 85 ° C. and 100 ° C., it can be defined that T_seuil = 83% T_commands and that the quantity of energy is set at 60% of the maximum (ie N = 60 with Qeff = N .Qmax as described below).

In operation, it is proposed here a behavior in stages, that is to say, double thresholding, one in open loop and the other in closed loop.

After heating, as long as the measured temperature T_CTN of the culinary article is lower than the value of the threshold temperature T_threshold (phase A figure 2 phase I figure 3 ), the quantity of electrical energy Qeff delivered to the heating means 11 is a constant value in time equal to a proportion N of the maximum value Qmax that can be supplied to said heating means, ie Qeff = N.Qmax with N a value (in percentages) positive and configurable (preferably in the factory and not by the user).

The temperature is measured in a succession of times, and in one embodiment, the amount of energy delivered to the heating means in a time (t) is equal to the amount of energy delivered to the heating means in a previous time. (t-1).

It is thus possible for example to manage the disturbances by calculating for example the time derivative of the measured temperature. We can therefore react on a sudden downward variation of the measured temperature (disturbance, figure 3 ) and apply a given energy value. It is also possible to implement this regulation during the heating phase (phase A figure 2 ) in which the time derivative is positive.

Preferably, the value N of the proportion depends on the value of the set temperature T_set. For example, it can be provided that if T_set is lower than a threshold setpoint value T_set-setpoint for example 85 ° C then N = 60%, so the heating means 11 are fed at 60% of their maximum power Qmax; and that if T_set is greater than the threshold setpoint T_set-setpoint for example 85 ° C, then N = 100%, so that the heating means 11 are fed at their maximum power Qmax.

This open loop operation makes it possible to ensure a rapid rise in temperature of the culinary article 10.

Then, at least at the first exceeding of the threshold temperature T_seuil by the measured temperature T_CTN of the culinary article 10 (phase B figure 2 , early phase II figure 3 ), the amount of electrical energy supplied to the heating means 11 is variable and slaved to the difference between the measured temperature T_CTN and the value of the setpoint temperature T_set.

Operation during this phase (phase B and C figure 2 phase II figure 3 ) is the closed loop.

It is preferably provided an initialization step in which, at the first exceeding of the threshold temperature T_seuil by the temperature T_CTN, the amount of electrical energy supplied to the power supply of the heating means 11 is initialized to an initial value Qeff_i (t0).

In one embodiment, the initial value Qeff_i (t0) is equal to the value of the quantity of electrical energy delivered to the heating means 11 at the previous instant Qeff (t0-1) (in this case before crossing the threshold T_seuil).

In another embodiment the initial value Qeff_i (t0) becomes minimal, possibly zero, that is to say that N then takes a minimum value Nmin stored in a memory, possibly equal to 0. This has the effect of slowing down the rate of rise in temperature of the culinary article while nevertheless benefiting from the thermal inertia of the article and the heating means, which makes it possible to limit the risks of abruptly exceeding the temperature setpoint.

In this case, the increase in temperature is less important, the delay of the sensor 13 relative to the actual temperature of the culinary article is reduced. The measured value is thus closer to the real value, so the measurement is better, more precise.

After initialization, at each measurement of the temperature, the quantity of electrical energy Qeff (t) delivered to the heating means is slaved to the difference between the measured temperature T_CTN and the value of the set temperature T_calls for example from the following way.

The difference between the value of the setpoint temperature T_set (constant) and that of the temperature T_CTN (t) measured at time t is defined by error E (t): $$\mathrm{E}\left(\mathrm{t}\right)=\mathrm{T\_consigne}-\mathrm{T\_CTN}\left(\mathrm{t}\right)$$

The quantity of electrical energy Qeff (t) delivered to the heating means is then a mathematical function of the error E (t).

For example, a simple mathematical function is provided in which the quantity of electrical energy Qeff (t) delivered to the heating means in a time t depends on the quantity of electrical energy Qeff (t-1) delivered to the heating means at previous time t-1, and depends on the value of the error E (t) calculated at time t: $$\mathrm{Qeff}\left(\mathrm{t}\right)=\mathrm{K}*\mathrm{E}\left(\mathrm{t}\right)+\mathrm{Qeff}\left(\mathrm{t}-\mathrm{1}\right)$$

With K a coefficient selected and allowing to influence the rate of regulation of the temperature.

avec δt l'écart temporel entre deux mesures de températures successives.At the first time t0 + δt of measurement after initialization (so after crossing the threshold temperature), we have: $$\mathrm{Qeff}\left(\mathrm{t}0+\mathrm{.delta.t}\right)=\mathrm{K}*\mathrm{E}\left(\mathrm{t}0+\mathrm{.delta.t}\right)+\mathrm{Qeff}\left(\mathrm{t}\mathrm{0}\right),$$

with Δt the time difference between two successive temperature measurements.

In one embodiment, the measurements are made every 1.5 seconds, ie δt = 1.5 seconds.

Thus, the amount of energy delivered to the heating means increases (phase B figure 2 ) since the threshold temperature has been reached until the target temperature has been reached, but the amount of electrical energy added to each iteration is smaller and smaller as the set temperature approaches.

When the set temperature is exceeded (phase C figure 2 ), the error E (t) becomes negative, so that the amount of electrical energy calculated at each iteration decreases until the measured temperature becomes lower than the setpoint.

In one embodiment, each time the set temperature is exceeded, the amount of calculated electrical energy is applied to the heating means.

In another embodiment, whenever the set temperature is exceeded, regardless of the result of the calculation of Qeff, provision is made to force the control of the quantity of electrical energy Q eff delivered to the heating means to a minimum value, for example Qeff_i (t0), possibly zero.

It is also possible, each time the set temperature is exceeded, to replace the calculation of equation (1): Qeff (t) - K * E (t) + Qeff (t-1) by an equation (1 ' ) in which the term Qeff (t-1) is subtracted: $$\mathrm{Qeff}\left(\mathrm{t}\right)=\mathrm{K}*\mathrm{E}\left(\mathrm{t}\right)-\mathrm{Qeff}\left(\mathrm{t}-\mathrm{1}\right)$$

Preferably, the supply of the heating means is carried out in "all or nothing" via a relay.

où Ton est la durée à l'état haut dans une période T correspondant à l'alimentation des moyens de chauffe, etThe power supply of the heating means 11 by the relay is made according to a periodic electrical signal square ( figure 4 ), of period T, and having a duty cycle $$\mathrm{\alpha }=\mathrm{Your}/\mathrm{Toff}$$

where Ton is the duration in the high state in a period T corresponding to the supply of the heating means, and

Toff is the low time in a period T during which the relay is off.

Thus, by controlling a value of the duty cycle α, it is simple to vary the quantity Qeff of energy delivered. the heating means. One can for example initialize the value Qeff_i by α = 0.

In one embodiment, the period T is 3 seconds. That is to say that the calculation of Qeff is done every 1.5s the result is applied to the relay only once in two. The values of period and calculation frequency above are purely illustrative and may vary depending in particular on the culinary article.

The power supply is heating means is steady state when the measured temperature is almost equal to the setpoint (α almost constant), as shown in phase C of the figure 2 .

Thanks to the invention, the fact of modulating the amount of electrical power supply of the heating means according to the set point makes it possible to adapt the power level according to the type of food to be treated and the heating mode. use.

By limiting the energy supplied to a culinary article, by cutting the energy delivered to the heating means, it is possible for a given cooking utensil, for example a heating bowl, to prepare delicate foods (sauces, milk, eggs, etc.). , chocolate ...) and to keep all types of food warm without any risk of deterioration of it, while maintaining a possibility of quick cooking for example for the preparation of soups requiring more energy. For example for a mixed soup, if 100% of the maximum energy is distributed to the heating means, the risk of burning the solid mixed particles of the soup is very high. Thanks to the invention, the heat transfer between the heating means and the culinary article is softer, which also makes it possible to keep food preparation at a consumption temperature hot (for example at 80 ° C. for 40 minutes).

Thanks to the invention, even in the presence of a temporary disturbance (for example a distance from the culinary article of its heating means), the temperature thereof returns very rapidly to the set value ( figure 3 ).

Claims (10)

1. Method for adjusting the temperature of a culinary article heated by a variable heating unit (11), with the method comprising the steps consisting in:

   - establishing (100) a value for a setpoint temperature (T_setpoint) to be reached,

   - measuring (110) the temperature (T_meas) of the culinary article,

   - comparing (120) the measured temperature (T_meas) of the culinary article with the value of the setpoint temperature (T_setpoint),

   - establishing (140) a threshold temperature value (T_threshold) less than the value of the setpoint temperature (T_setpoint),

   - comparing (150) the measured temperature (T_meas) of the culinary article with the value of the threshold temperature (T_threshold),

   characterised in that it further comprises a step consisting in:

   - delivering (130) to the heating unit a quantity of electrical supply energy (Qeff) that depends

   -- on the difference between the measured temperature (T_meas) and the value of the threshold temperature (T_threshold), and

   -- on the difference between the measured temperature (T_meas) and the value of the temperature setpoint (T_setpoint).
2. Method according to claim 1, wherein as long as the measured temperature (T_meas) of the culinary article is lower than the value of the threshold temperature (T_threshold), the quantity of energy (Qeff) delivered to the heating unit (11) is a constant value over time equal to a proportion of the maximum value that can be supplied to said heating unit.
3. Method according to any of the preceding claims, wherein at least one first exceeding of the threshold temperature (T_threshold) by the measured temperature (T_meas) of the culinary article, the quantity of energy supplied to the heating unit is variable and controlled by the difference between the measured temperature (T_meas) and the value of the setpoint temperature (T_setpoint).
4. Method as claimed in the preceding claim, wherein the temperature is measured as a succession of time, with the quantity of energy delivered to the heating unit in a time (t) being furthermore controlled by the quantity of energy delivered by the heating unit in a preceding time (t-1).
5. Method as claimed in any preceding claim, wherein the quantity of energy (Qeff) delivered to the heating unit (11) is regulated by an electrical supply signal of the heating unit, said supply signal being a periodic square signal of which the cyclical relationship (α) is variable.
6. Method as claimed in any preceding claim, comprising a step consisting in initialising the quantity of energy delivered to the heating unit to a minimum or zero value at the first exceeding of at least the threshold temperature (T_threshold) by the measured temperature (T_meas) of the culinary article.
7. Method as claimed in any preceding claim, comprising a step consisting in cutting off the supply of the heating unit if the measured temperature (T_meas) of the culinary article exceeds the setpoint temperature (T_setpoint).
8. Computer programme comprising programme code instructions for the execution of the steps of the method as claimed in any preceding claim, when said programme is executed on a computer.
9. Device for adjusting the temperature of a culinary article (10), able to implement the method according to any of claims 1 to 7, comprising:

   - a temperature sensor (13) for measuring the temperature (T_meas) of the culinary article,

   - a unit (11) for heating the culinary article,

   - means for regulating (12) the electrical supply of the heating unit,

   - means for establishing a setpoint temperature value (T_setpoint) to be reached,

   - a calculator configured to

   -- compare the measured temperature (T_meas) of the culinary article with the value of a threshold temperature (T_threshold) and with the value of the temperature setpoint (T_setpoint), and for

   -- controlling the heating unit (11) to deliver a quantity of energy (Qeff) that depends

   --- on the difference between the measured temperature (T_meas) and the value of the threshold temperature (T_threshold), and

   --- on the difference between the measured temperature (T_meas) and the value of the setpoint temperature (T_setpoint).
10. Device according to claim 9 further comprising a relay for the electrical supply of the heating unit (11).

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