EP2618064A1 - Method for controlling a cooking process, and a cooking device for carrying out the method - Google Patents

Abstract

The method involves measuring repeatedly the gas concentration in the cooking appliance and comparing each of two temporally successive measurement values. An extreme value (Me) of the gas concentration is detected as a shut-off condition. The measurement process is continued for a time period after detecting the extreme value. The cooking appliance function is initiated is another shut-off condition is satisfied after detection of the former switch-off condition. An independent claim is included for a cooking appliance with a control unit.

Description

The present invention relates to a method for controlling a cooking process in a cooking appliance according to the preamble of patent claim 1, as well as a cooking appliance for carrying out the method according to the preamble of patent claim 9.

Such a method is known from DE 103 27 864 B4 known. This method for non-contact control of a cooking process in a cooking appliance with a cooking chamber has a sensor for detecting a gas concentration in the oven, and an electrical or electronic control. The controller has an evaluation circuit and a memory and is in signal transmission connection with the sensor. In this case, a Gargerätefunktion is triggered when the first derivative of the gas concentration after the time after the first reaching an extreme value has become zero.

The invention has for its object to develop a comparison with the prior art improved process.

This object is achieved by a method having the features of patent claim 1. Furthermore, the object is achieved by a cooking appliance with the features of claim 9.

• Wiederholtes Messen der Gaskonzentration im Gargerät und Vergleich jeweils zweier zeitlich aufeinanderfolgender Messwerte,
• Erkennen eines Extremwertes der Gaskonzentration als eine erste Abschaltbedingung, Nach Erkennen des Extremwertes Fortführen des Messvorganges für eine bestimmte Zeitdauer und
• Auslösen einer Gargerätefunktion, wenn nach Erkennen der ersten Abschaltbedingung innerhalb der Zeitdauer zumindest eine weitere Abschaltbedingung erfüllt wird.

The method according to claim 1 for controlling a cooking process in a cooking appliance, in which a changing in the cooking appliance during the cooking process gas concentration is determined, comprising the following steps:

• Repeated measurement of the gas concentration in the cooking appliance and comparison of two temporally successive measured values,
• Detecting an extreme value of the gas concentration as a first shutoff condition, After detection of the extreme value continuation of the measuring process for a certain period of time and
• Triggering a cooking appliance function, if after detecting the first shutdown condition within the time period at least one further shutdown condition is met.

By such a scheme, it is possible to run the cooking largely automated. Advantageously, the cooking process is terminated when, for example, a food has reached the ideal degree of browning or a dough is baked through. By regulating the cooking process, for example, a crispy bottom with pizzas or tarte flambée or juicy fruits with a fruit cake can be reached. The gas whose concentration is measured is preferably oxygen. The change in the concentration of oxygen in the cooking chamber is a measure of a change in humidity in the oven. About the change in humidity in the cooking chamber can be the cooking progress rate. A reduction in the oxygen content is due to an increase in the moisture content, conversely, an increase in the oxygen content means a decrease in the moisture content. The extreme value of the gas concentration is achieved by repeatedly measuring it and by comparing in each case two temporally successive measured values, the measured values not having to follow one another directly in time. A typical sampling rate for forming the measured values is for example 10 seconds. The sampling rate is understood to be the time duration between the respective measurements of the gas concentration. The extreme value may be formed as a maximum or a minimum depending on the measured gas. If, for example, the oxygen concentration is measured and converted into a content of gaseous water or a moisture content, then the extreme value of the moisture content is formed as a maximum. To trigger the cooking appliance function at least two shutdown must be met. A first shutdown condition is the detected extreme value of the gas concentration. If, after the first switch-off condition has been determined, a further switch-off condition has been met within a defined period of time, the measuring process is stopped. The initiated cooking appliance function can be, for example, a termination of the cooking process by switching off a heater. Additionally or alternatively, an optical or audible warning signal may be provided for a user of the cooking appliance.

In a preferred embodiment, the further switch-off condition is fulfilled if the values measured until the end of the time duration confirm the extreme value. In the case of a maximum as an extreme value, all subsequent values measured during the specified period of time must be less than or equal to the maximum for its confirmation. This prevents that when a local extreme value is detected already the cooking appliance function is triggered, although a curve of the gas concentration moves after a brief burglary again in the direction of a new extreme value. If the extreme value is not confirmed, then the first switch-off condition is reset or deleted and, in accordance with the first method step, repeated measurements of the gas concentration in the cooking appliance and comparison of two temporally successive measured values are searched for a new extreme value.

In a further embodiment, it is proposed that the second switch-off condition be satisfied if a change in the current measured value in the direction of a gas concentration value measured at the beginning of the method or a constant value of the gas concentration is determined several times within a specific time interval. The value measured at the beginning of the method can be, for example, a starting value or a value of the gas concentration measured first of all. A change in the measured value in the direction of a value measured at the beginning of the method must take place within the specified time interval. If this is not the case, then the first switch-off condition is reset or deleted and the method continues with the first method step. The time interval can be, for example, 5 minutes. Within a time interval, the respective current gas concentration is measured several times. To meet the further switch-off condition, this time interval must, for example, be traversed four times with a positive result (change in the measured value in the direction of a value measured at the beginning of the method, or a constant measured value). The time duration for fulfilling the further switch-off condition is thus 20 minutes in this example.

It is preferred if a heater of the cooking appliance is reduced in power or turned off when fulfilling the further shutdown condition. As heating means is to be understood, for example, a resistance heater, a microwave generator or a steam generator. A reduction of the power of the heater takes place for example, such that only a warming function is given. By switching off the heating elements of the cooking process is stopped and in particular the cooking appliance off, or put into a standby mode.

If a gargutspezifischer value is selected and / or entered by a user of the cooking appliance at the beginning of the process, so for example by a control of the cooking appliance a suitable mode (for example pizza stage) in conjunction with a cooking temperature specified or proposed. As a food-specific value is for example a Gargutart, a weight of the food or a Gargrat (eg., Medium) to understand.

A preferred development consists in that at least one parameter, in particular a time constant of the method, is influenced by the food-specific value. This makes it possible, for example, to incorporate different cooking behaviors of different types of food (such as fish, poultry, cakes) into the process, thereby achieving an ideal state of cooking when the further shutdown condition is met. Such parameters or time constants are stored in a memory of the cooking appliance with reference to the food-specific values. The reference can represent a value table or an arithmetic operation.

It is preferred if the heating device is reduced or switched off regardless of the measured gas concentration after exceeding a fixed maximum duration in their performance. As a result, for example, a burning of the food is prevented in case of malfunction of the cooking appliance. The maximum duration is particularly dependent on a default by the user of the cooking appliance Gargutart.

By each two measured values are compared with each other, which are temporally a multiple of a sampling rate apart, the method can also be used in cooking processes in which the gas concentration changes only very slowly. Such a sequence can be implemented, for example, by a shift register. A shift register is to be understood as a memory area which can store several numbers (measured values) and is constructed in the form of an indexed field. Each number is assigned an index. When adding a new value to an already filled one Shift register causes the first value to be cleared from the field and the other values to move up. The added value is stored as the last element in the shift register.

Furthermore, the invention relates to a cooking appliance with a control unit for the automated control of a cooking process according to the aforementioned method. In this case, the control unit preferably detects an opening of the cooking appliance door and as a consequence terminates the repeated measurement of the gas concentration. As a result, incorrect measurements and their consequences, such. B. not completely durchgegarte or burned food prevented. A user of the cooking appliance is preferably pointed by an optical or acoustic signal to the termination of the measuring process.

By the control unit detects a closing of the cooking appliance door after opening and then starts a new measuring cycle, the automated control of the cooking process continues without user intervention.

Fig. 1

den zeitlichen Verlauf des Sauerstoffgehalts bzw. der Feuchteänderung;

Fig. 2

ein Ablaufdiagramm des Verfahrens gemäß einem ersten Ausführungsbeispiel;

Fig. 3

den zeitlichen Verlauf der Feuchteänderung mit lokalen Maxima Mel;

Fig. 4

eine Ergänzung des Ablaufdiagramms aus Fig. 2 unter Berücksichtigung des Öffnens der Tür;

Fig. 5

eine Ergänzung des Ablaufdiagramms aus Fig. 2 unter Berücksichtigung einer Maximaldauer;

Fig. 6

einen von Fig. 1 abweichenden, zeitlichen Verlauf der Feuchteänderung als Grundlage für ein zweites Ausführungsbeispiel und

Fig. 7

ein Ablaufdiagramm des zweiten Ausführungsbeispiels.

Further features and advantages of the invention will become apparent from the following description of two embodiments with reference to the accompanying figures. Show it:

Fig. 1

the time course of the oxygen content or the change in humidity;

Fig. 2

a flowchart of the method according to a first embodiment;

Fig. 3

the time course of the change in humidity with local maxima Mel;

Fig. 4

an addition to the flowchart Fig. 2 taking into account the opening of the door;

Fig. 5

an addition to the flowchart Fig. 2 taking into account a maximum duration;

Fig. 6

one of Fig. 1 deviating, time course of the change in humidity as a basis for a second embodiment and

Fig. 7

a flowchart of the second embodiment.

In the figures, identical or functionally identical elements are provided with the same reference numerals.

in einen Wert der Feuchteänderung Ma gegenüber einem Anfangswert umgerechnet. Dabei wird nur der prozentuale Wert einer Feuchteänderung bezüglich einer zu Beginn der Messung im Backrohr herrschenden Feuchte (Anfangswert) bestimmt. Der temperaturabhängige Anfangswert der Feuchte ist dabei ohne Bedeutung, wodurch sich die Auswertung vereinfacht und störende Einflussgrößen, wie z.B. die Temperatur unberücksichtigt bleiben können. Der zeitliche Verlauf der prozentualen Feuchteänderung wird zur Ermittlung des Garzeitendes herangezogen. Während des Garvorgangs steigt der Wert für die Feuchteänderung Ma beispielsweise bis auf 22 %. Das Maximum Me mit 22 % wird nach einer Zeit von 27 Minuten erreicht. Nach dem Maximum Me fällt der Feuchtegehalt stetig ab. Der ideale Abschaltzeitpunkt ist 3 Minuten nach Auftreten des Maximums Me erreicht und wird in Abhängigkeit von der Gargutart empirisch ermittelt. Der Verlauf der Feuchteänderung ist stark vom Gargut und dessen Eigenschaften abhängig. Vor Start des automatisierten Garvorganges wählt ein Benutzer des Gargerätes mehrere gargutspezifische Werte G aus. Dabei wählt er ein Gericht aus einer Liste aus (z.B. Rührteig, Hefeteig, Tiefkühlpizza, Flammkuchen oder ähnliches). Bei manchen Gartutarten kann der Benutzer auch ein Gewicht des Gargutes und/oder zusätzlich noch einen Gargrat, wie z.B. medium oder kross wählen. Anschließend startet er den Garvorgang. In einem Speicher des Gargerätes sind mit Bezug auf das gewählte Gericht mehrere gartutspezifische Parameter bzw. Zeitkonstanten, sowie die zu verwendende Heizart mit einer Gartemperatur hinterlegt, die gegebenenfalls noch entsprechend den Benutzereingaben des Gargutgewichtes, sowie dem Gargrat angepasst werden. Eine Konstante D, ein Zähler P, eine Vorlaufzeit T1, eine Zeitdauer T2, ein Zeitintervall T3 und die Maximaldauer T4 werden in Abhängigkeit der gargutspezifischen Werte G ausgewählt, bzw. angepasst und finden in den folgenden Ausführungsbeispielen Verwendung. Fig. 1 shows a dashed line a typical course of the oxygen content in the cooking chamber during a cooking process. This initially corresponds to the oxygen content of the ambient air of about 21% vol. The change in the oxygen content during the cooking process is directly dependent on the course of the moisture content in the cooking chamber. This makes it possible to calculate the course of the change in humidity during the cooking process by continuously measuring the oxygen content. This effect is used in the two embodiments to provide an automated cooking process in which the oven recognizes automatically when the ideal time to shut down the cooking process is reached. The measured oxygen content (oxygen concentration) is given by the formula: $$\mathbf{Ma}\mathrm{=}\left(\mathrm{1}\mathrm{-}\frac{\mathrm{oxygen\; concentration}\left[\mathrm{\%}\right]}{\mathrm{21}\mathrm{\%}}\right)\mathrm{x}\mathbf{100}\mathbf{\%}$$

converted into a value of the humidity change Ma compared to an initial value. Only the percentage value of a change in humidity with respect to a moisture prevailing at the beginning of the measurement in the oven (initial value) is determined. The temperature-dependent initial value of the moisture is of no importance, which simplifies the evaluation and can disregard disturbing factors such as the temperature. The time course of the percentage change in humidity is used to determine the end of cooking time. During the cooking process, the value for the humidity change Ma, for example, increases up to 22%. The maximum me with 22% is reached after a time of 27 minutes. After the maximum Me, the moisture content drops steadily. The ideal switch-off time is reached 3 minutes after the maximum Me has occurred and is determined empirically as a function of the type of food to be cooked. The course of the moisture change is very strong on the food and its properties dependent. Before starting the automated cooking process, a user of the cooking appliance selects several food-specific values G. He chooses a dish from a list (eg batter, yeast dough, frozen pizza, tarte flambée or the like). In some garden species, the user can also choose a weight of the food and / or additionally a Gargrat, such as medium or crisp. Then he starts the cooking process. In a memory of the cooking appliance with reference to the selected dish several garden-specific parameters or time constants, as well as the type of heating to be used with a cooking temperature deposited, which may still be adjusted according to the user inputs of Gargutgewichtes, as well as the Gargrat. A constant D, a counter P, a lead time T1, a time duration T2, a time interval T3 and the maximum duration T4 are selected as a function of the cooking product-specific values G, or adapted and used in the following embodiments.

The program sequence or algorithm according to a first embodiment is in Fig. 2 shown. After the user input of the food-specific values G and the start of the cooking program, a countdown 1 is set to a preprocessing time T1 and runs backwards. T1 is empirically determined and represents a gargutspezifische Mindestgardauer. After the expiration of the countdown 1 begins the actual measurement process, or the measurement cycle Z, where previously the variables F and Ms are set to zero. The variable F can be assigned the value zero or the value one during the program execution. Subsequently, a countdown 2 is set to T2 (empirically determined time duration for the second switch-off condition) and started. Next step is the reading of the current value of the oxygen sensor, which is converted into a corresponding value of the humidity change Ma. The first time through, the values for F and Ms are each = 0. This is followed by a branch via a query. If the variable F is equal to zero or the current humidity change Ma is greater than a stored value of the humidity change Ms plus a constant D, F is set to one and Ms to the current humidity value Ma. D is an empirically determined, property-specific constant. Ms is designed as storage space for the last measured value of the humidity change. The program will now return to the position where Countdown 2 is set to T2. If F is not equal to zero and the current humidity change Ma is less than Ms plus the D value, then the program proceeds to the next branch in the form of a query in which It is checked if the countdown 2 has expired. If countdown 2 has not expired, the program returns to the position at which the current sensor value is read. If countdown 2 has expired, the heating elements are switched off and the cooking program is ended. The countdown 2 is formed as a loop with the time duration T2 within which, after recognizing a first-time extreme value Me in the form of a maximum Me, the moisture change Ma is further measured and looked for a renewed maximum Me. As a result, locally occurring peaks or local maxima Mel of the change in humidity are not used for the switch-off process.

This is again in the diagram of Fig. 3 illustrated. Therein, three local maxima Mel are selected by way of example and in each case that time range is marked which is necessary in order to overcome these local maxima Mel. All local maxima Mel, according to which a new maximum Me sets within the expiration time T2 of the countdown 2, are not considered and thus do not lead to the switching off of the heating elements.

Fig. 4 shows an advantageous extension of the algorithm Fig. 2 in which an opening of the cooking appliance door is detected during the process and taken into account accordingly. By opening and closing the cooking appliance door, as it is z. B. results in the pouring of a roast, the moisture content in the oven can change abruptly by the partial mixing of the cooking chamber with the atmosphere located outside the cooking appliance. The comparison of the current moisture change Ma with the stored moisture change Ms can lead, for example, to a premature shutdown of the cooking appliance. To prevent this, the flowchart of the Fig. 4 after the first branching query another query is inserted, which during the opening of the door, the program flow to the place immediately after the first countdown ( Fig. 2 ) resets. The actual measuring cycle Z is restarted until the door is closed again.

An addition to the algorithm Fig. 2 to a query of a maximum duration T4 is in Fig. 5 shown. After reading the measured values, the time that has elapsed since the heater was switched on is compared with the maximum duration T4. A crossing the maximum duration leads to switching off the heater. This ensures that the food does not burn in the event of an unexpected malfunction. However, the ideal cooking time can be exceeded.

In practical experiments it has been shown that there are food to be cooked (eg cakes in bakeware), in which according to the diagram in Fig. 6 At the beginning of the cooking process, the moisture change increases rapidly, but then slowly increases to a broad maximum Me. The maximum Me is therefore only indistinctly formed and requires a modified algorithm according to a second exemplary embodiment for reliable detection. The modification essentially relates to a shift register, which compares the measured values in each case with a time delay, as well as a modified query for the detection of the maximum Me.

A

= Abtastrate

A1

= erste Abschaltbedingung

A2

= weitere Abschaltbedingung

D

= Konstante

G

= gargutspezifischer Wert

Ma

= aktueller Messwert; aktueller Wert der Feuchteänderung

Me

= Extremwert; Maximum

Me

= lokales Maximum

Mo

= Startwert

Ms

= gespeicherter Messwert; gespeicherter Feuchteänderung

P

= Zähler

T1

= Vorlaufzeit

T2

= Zeitdauer für A2

T3

= Zeitintervall

T4

= Maximaldauer

Z

= Meßzyklus

The corresponding flow chart of the algorithm is in Fig. 7 shown. After program start the countdown 1 is set to T1 and expires. Every 10 seconds, a current value of the humidity change Ma is added to the shift register. If the countdown 1 has expired, then a counter P is set to zero and the countdown 2 is marked as deactivated. Then every 10 seconds a current value Ma for the humidity change is determined and added to the shift register. In the following branch is queried whether the countdown 2 is activated and has expired. If this condition is met, the counter P is set to zero and the countdown 2 is deactivated. Thereafter, or if the above condition is not satisfied, another query is made as to whether the last value in the shift register is less than or equal to the first value in the shift register. If this condition is not fulfilled, then the program is continued at the beginning of the measuring cycle Z. If this condition is met, the counter P is increased by 1 and countdown 2 is set to five minutes and activated. This is followed by the branching with the query whether P is greater than or equal to P _max . If the condition is not fulfilled, the program is reset to the beginning of the measuring cycle Z. If P is greater than or equal to P _max , the heating elements are switched off and the cooking program is ended. Depending on the requirements of the types of food used, it may be useful to additionally introduce a And-link at the penultimate branch. The query in the branch would then be: If the last value in the shift register is less than or equal to the first value in the shift register, and the difference of the two humidity changes is greater than or equal to a minimum (specified) difference. This causes small ones insignificant changes in humidity are not taken into account. The preceding program sequence is designed in such a way that after the first detection of an extreme value or maximum Me, a first shut-off condition A1 is fulfilled. The further switch-off condition A2 is fulfilled if after the first detection of a maximum Me P times in succession, in each case within a fixed time period T3 of 5 minutes, a reduced or at least constant, current value Ma is detected compared to the value of the humidity change Ms stored in the shift register. The time duration for fulfilling the further switch-off condition A2 results from P times T3. The size of the shift register is such that it can absorb the humidity changes of the last 5 minutes at a sampling rate of 10 seconds. The shift register thus comprises 30 values. The aforementioned two embodiments of the method are easy to apply to a variety of dishes. The parameters can be determined empirically, the values are reproducible. Instead of an oxygen sensor, another gas or humidity sensor can be used.

A

= Sampling rate

A1

= first shutdown condition

A2

= further shutdown condition

D

= Constant

G

= food specific value

Ma

= current measured value; current value of the humidity change

me

= Extreme value; maximum

me

= local maximum

Not a word

= Start value

ms

= stored reading; stored humidity change

P

= Counter

T1

= Lead time

T2

= Duration for A2

T3

= Time interval

T4

= Maximum duration

Z

= Measuring cycle

Claims (11)

Method for controlling a cooking process in a cooking appliance, in which a gas concentration which changes in the cooking appliance during the cooking process is determined, comprising the following steps: Repeated measurement of the gas concentration in the cooking appliance and comparison of two temporally successive measured values (Ma, Ms), Detecting an extreme value (Me) of the gas concentration as a first switch-off condition (A1), - After detecting the extreme value (Me), continue the measuring process for a period (T2) and - Triggering a cooking appliance function, if after detection of the first shutdown condition (A1) within the time period (T2) at least one further shutdown condition (A2) is met. A method according to claim 1, characterized in that the further switch-off condition (A2) is met when the measured values (Ma) up to the end of the time duration (T2) confirm the extreme value (Me). A method according to claim 1, characterized in that the further switch-off condition (A2) is met, if several times within a specified time interval (T3), a change of the current measured value (Ma) in the direction of a measured at the beginning of the method value (Mo) of the gas concentration or a constant value of the gas concentration is detected. Method according to one of the preceding claims, characterized in that when fulfilling the further shutdown condition (A2), a heating device of the cooking appliance is reduced in its power or switched off. Method according to one of the preceding claims, characterized in that at the beginning of the cooking process by a user of the cooking appliance at least one gargutspezifischer value (G) is selected and / or entered. A method according to claim 5, characterized in that at least one parameter (P, D), in particular a time constant (T1, T2, T3, T4) of the method by the gargutspezifischen value (G) is influenced. Method according to one of the preceding claims, characterized in that a heating device of the cooking appliance is reduced or switched off regardless of the measured gas concentration after exceeding a predetermined maximum duration (T4) in their performance. Method according to one of the preceding claims, characterized in that in each case two measured values (Ma, Ms) are compared with each other, which are temporally a multiple of a sampling rate (A) apart. Cooking appliance with a control unit for the automated control of a cooking process according to a method according to one of the preceding claims. Cooking appliance according to claim 9, characterized in that the control unit detects an opening of a cooking appliance door and as a result the repeated measurement of the gas concentration stops. Cooking appliance according to claim 10, characterized in that the control unit detects a closing of the cooking appliance door after opening and then starts a new measuring cycle (Z).

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