EP2061287A2 - Method to stop the timing of a pulsed microwave generator for a cooking device and cooking device for this - Google Patents

Abstract

The method involves controlling the average power and the pulse duration independent of each other between two successive pulses of the microwave generator. The cooked degree of the cooked food such as internal cooked degree is determined particularly by a core temperature, a cook value, a pasteurization value or a reduction of weight. The external cooked degree is determined particularly by the browning and encrustation. An independent claim is included for a cooking appliance with a microwave generator, a control and regulating unit, operator controls, a storage unit and a sensor.

Description

The invention relates to a method for adjusting the timing of at least one pulsed microwave generator of a cooking appliance as a function of at least one food parameter, at least one cooking chamber parameter, at least one user input parameter and / or at least one cooking process parameter.

Foods with a short cooking time, which are sensitive to microwave radiation, may only be exposed to continuous wave microwave radiation for relatively short periods of time. On the other hand, insensitive foods can be exposed to microwave radiation for extended periods of time. In addition, the microwave compatibility of a food may change in the course of a cooking process. This should be taken into account when optimizing a cooking process.

In Fig. 1 is the typical time course of the output power P of a pulsed, not shown microwave generator, in particular a magnetron, plotted. The output power P is understood to mean the power of the envelope of a microwave signal oscillating with the microwave carrier frequency. During the application of a cooking product, not shown, with a rectangular microwave _pulse of duration T _pulse The microwave generator delivers an instantaneous power with a peak value P ₁ , which drops to zero during the pause times for a pause duration T _Pause . The average output power P _{means of} the described rectangular microwave signal is described by the simple relation P _average = P ₁ · T _pulse / T ₀ and can be varied via a change in the ratio between the pulse duration T _pulse and the period T ₀ , ie the duty cycle ,

From the prior art, for example from the US 4,149,057 , it is known to set the average microwave power generated by a magnetron by a change in the duty cycle of a rectangular pulsed magnetron output.

Furthermore, in the DE 35 28 228 A1 discloses to provide a time and / or program control device in a cooking appliance with a microwave source, by which the microwave energy is adjustable in heating power by clocking and heating time, such that the average microwave power for different steps of a cooking program are different.

In the EP 1 021 068 B1 a generic method for thawing food in a microwave oven is disclosed in which, depending on a measured cooking process parameter of the entry of the microwave radiation is set in a food to be thawed. In this case, this parameter is followed at predetermined intervals during a cooking process, and after each measurement interval, the average power of the same is adapted to the change of the cooking process parameter via the timing of the microwave signal.

From the US 4,317,977 In addition, it is known to control the cooking time in a microwave oven as a function of a measured food parameter of a food to be cooked. As Gargut parameters here are the absorbed microwave power of the food, the initial mass of the food, the starting temperature of the food, the specific heat of the food and the weight loss of the food by evaporation of water during cooking described.

In the US 5,317,133 discloses a method for controlling the magnetron output in a microwave oven in which the average microwave power is adjusted by the duty cycle of the periodic magnetron output. Here, the entire cooking time and the average Magentron output power is adapted to the food within the microwave oven.

Another microwave oven is in the US 4,370,535 described, in which the duty cycle of a magnetron is set in dependence of a cooking temperature. In particular, for the thawing of food to be cooked, the duty cycle can be set as a function of the temperature of the cooking product so that the average magnetron output power decreases steadily at the end of the cooking process.

A disadvantage of this prior art is that an adjustment of the average microwave power to a parameter during a cooking process allows only insufficient consideration of the microwave sensitivity of a food.

Furthermore, from the DE 38 30 431 C1 a microwave household appliance with defrosting known in the food is intermittently subjected to microwave radiation, which can compensate for different temperatures within the food in the Beaufschlagungspausen, ie a homogenization of the thawing process is brought about. The control of the timing of the microwave power is carried out in dependence on a user-selected thawing performance. A disadvantage of the in the DE 38 30 431 C1 disclosed microwave domestic appliance is that it is not possible to adjust the timing of the microwave pulses during the cooking or thawing process to changing parameters, such as food parameters.

It is thus the object of the present invention to develop the generic method such that the disadvantages of the prior art are overcome. In particular, during operation of a cooking appliance, the pulsed microwave power for applying food to be cooked should be optimized so that a gentle and efficient cooking takes place during the entire cooking process.

This object is achieved in that the average power and the pause duration between two successive pulses of the microwave generator can be controlled or regulated independently.

Furthermore, it can be provided that the type of food to be cooked, such as meat, fish, baked goods or the like, the initial state of the food, such as frozen or fresh or the initial mass, the initial weight, the starting caliber or the like, the degree of cooking of the food, such as internal degree, determined, in particular, by a core temperature, a cooking value, a pasteurization value, a weight loss or the like, and / or the external degree of cooking, determined in particular by the browning, crusting or the like, and / or the load of food in a cooking space as food parameter is or will be, preferably via at least a first sensor.

It is also proposed that a climate parameter, in particular determined by the temperature, the humidity and / or the flow rate of cooking chamber, is determined in the cooking chamber as cooking chamber parameters, preferably via at least one second sensor.

According to the invention, it is proposed that a desired value, such as a desired value of a food parameter, a cooking chamber parameter or the like, and / or a cooking process and / or cooking process step is input as a user input parameter, preferably with the interposition of an operating device internal storage device storage, a gargeräteexternen storage device, the Internet or the like.

Furthermore, it is proposed according to the invention that the duration and / or remaining running time of a cooking process or cooking process step and / or a cooking space parameter and / or a food parameter be or are determined as cooking process parameters at least two times during a cooking process or cooking process step. preferably via at least one third sensor.

Preferred methods according to the invention are characterized in that, at the beginning of a cooking process or cooking process step, a first default value of the mean power and a second default value of the pause duration are determined as a function of at least one user input parameter.

It is also preferably provided that the first and / or second default value is adjusted depending on at least one detected food parameters, a detected cooking space parameters and / or a detected cooking process parameters or be.

According to the invention it can also be provided that the dead times are adapted in dependence of, in particular temporally changing, thermal diffusion behavior of the food.

The invention further proposes that the microwave generator generates a periodic microwave signal having a substantially rectangular pulse shape, the average power of this signal being set by the ratio between the period duration and the pulse duration.

The invention also provides a cooking appliance with at least one microwave generator, a control or regulating device, an operating device, a storage device and at least one sensor for carrying out a method according to the invention.

Such a cooking appliance according to the invention may further be characterized by an electric heating device, a gas-operated heating device, a cooling device, a moisture supply device, a moisture removal device, a heat storage device, a cooking chamber atmosphere circulation device and a display device.

It is thus the surprising finding of the invention that by the ability to set both the average power and the pause duration of a pulsed microwave signal independently, an optimization of a cooking process or cooking process step in Dependence of a food parameter, a cooking space parameter, a user input parameter and / or a cooking process parameter during the entire duration of the cooking process or cooking process step can take place. By means of an intelligent clocking of the microwave radiation, ie by an intelligent setting of pulse duration and pause duration, whereby the variables also determine the average power, depending on the parameters mentioned, the microwave compatibility of foods in their respective cooking phases can be taken into account for achieving an optimum cooking result.

According to the invention, the average output power of a microwave generator can first be set by setting the duty cycle T _pulse / T ₀ , that is to say the ratio between pulse duration and period duration of the clocked microwave signal. The pause time T _pause = T ₀ (1-T _pulse / T ₀ ) is linked as a remaining degree of freedom over the duty cycle with the period T ₀ . In this way, the pause time can be optimized separately depending on a food parameter, a cooking space parameter, a user input parameter and / or a cooking process parameter during the entire duration of the cooking process or cooking process step. By the pause times between individual microwave pulses for temperature compensation in the food to be cooked sufficiently large, in particular the harmful effects of hot / cold spots in the food can be avoided.

In addition, the invention allows the allocation of an average power and a pause duration to each food, cooking process and / or one of the aforementioned parameters. This assigned value, which leads to a default setting, can be changed as a function of, for example, a known caliber, a food item, the load in the cooking chamber of a food, the initial state of the item to be cooked, such as fresh or frozen, or further state detections during a cooking process. In this case, a cooking process parameter, for example, be determined by a remaining time of a cooking program, so that, for example, at the end of the cooking time for temperature compensation in the food a reduction of timing is possible, so that it comes to a more uniform heating and optimization of the cooking result.

The optimization according to the invention of the microwave application of food to be cooked not only leads to an optimization of the sensory quality of the finished cooked food, but also to a reduction of the cooking time and an energy saving.

1. i) Benutzereingabe-Parameter
   Um ein Hähnchen zu garen, werden vor Beginn eines Garprozesses von einer Bedienperson Soll-Gargut-Parameter, beispielsweise in Form einer gewünschten Gargutkategorie bzw. Gargutart" Geflügel/Braten", einer gewünschten Bräunung und einer gewünschten Kerntemperatur des Garguts, über eine Bedienvorrichtung eines Gargerätes ausgewählt. In Abhängigkeit dieser eingegebenen Benutzereingabe-Parameter wird von einer Steuer- oder Regeleinheit des Gargerätes jeweils ein Default-Wert für die Pulsdauer und die Pausenzeit der getakteten Mikrowellenleistung berechnet. Bei der hier ausgewählten Gargutart "Geflügel/Braten" wird für den nachfolgenden Garprozeß durch einen entsprechenden Tastgrad bspw. die volle mittlere Mikrowellenleistung festgelegt, da sowohl Geflügel als auch Braten relativ unempfindlich gegenüber Mikrowellenstrahlung sind. Die ausgewählte Soll-Bräunung hat keinen Einfluß auf die Taktung der Mikrowellenleistung. Im Gegensatz dazu wird in Abhängigkeit des ausgewählten Soll-Wertes der Kerntemperatur der Tastgrad der Mikrowellenleistung verändert. So führt generell eine Erhöhung des Kerntemperatur-Soll-Wertes zu einer Erhöhung der mittleren Ausgangsleistung der Mikrowellenquelle. Im Anschluß daran läuft der Garprozeß mit den errechneten Default-Werten für die Taktung der gepulsten Mikrowellenleistung an. Das vorstehend genannte Beispiel verdeutlicht also die Steuerung bzw. Regelung der mittleren Mikrowellenleistung in Abhängigkeit von Benutzereingabe-Parametern.
2. ii) Gargut-Parameter
   In den ersten Minuten des genannten Garprozesses werden die Zustände des Garguts erkannt. Insbesondere wird vom Gargerät erkannt, ob es sich bei der Art des Garguts tatsächlich um Geflügel oder Braten handelt und ob das Gargut tiefgekühlt oder frisch ist. Des weiteren werden das Kaliber und die Form des Garguts, die Gargut-Last, und die Feuchte der Garraumatmosphäre, zur Bestimmung eines Gargutgewichtsverlustes, erkannt. Hierzu kommen geeignete Sensoren zum Einsatz.
   Daraufhin wird die aktuelle Taktung in Abhängigkeit der erkannten Gargutzustände, also in Abhängigkeit von Gargut-Parametern, nach Abschluß des jeweiligen Erkennungsprozesses erneut angepaßt.
   Wenn beispielsweise ein tiefgekühltes Hähnchen gegart werden soll, wird, insbesondere mittels eines in das Gargut eingesteckten Garprozeßfühlers, eine Kerntemperatur von unter 0°C gemessen. Daraufhin werden die zuvor errechneten Pausenzeiten der gepulsten Mikrowellenleistung zum Temperaturausgleich zwischen unterschiedlich heißen Stellen im Gargut deutlich verlängert, da zum Auftauen von Gargut generell ein möglichst homogener Eintrag von Mikrowellenstrahlung in das Gargut nötig ist. Wenn die Kerntemperatur, die weiterhin während des Garprozesses kontrolliert wird, über 0°C steigt, werden die Pausenzeiten verkürzt.
   Eine Aussage über die Größe des Hähnchens wird durch die Kalibererkennung ermöglicht. Das Kaliber bzw. die Größe kann beispielsweise über die Auswertung der Ausgabedaten des Garprozeßfühlers über die Zeit erfolgen. Handelt es sich nun um ein kleines Kaliber, wird die mittlere Mikrowellenleistung durch Anpassung des Tastgrades reduziert. Alternativ kann bei Erkennung eines sehr großen Kalibers wieder die volle nominelle mittlere Mikrowellenleistung eingestellt werden.
   Das genannte Beispiel verdeutlicht, wie in Abhängigkeit zweier Gargut-Parameter, nämlich der gemessenen Kerntemperatur und dem erkannten Kaliber des Garguts, während eines Garprozesses oder Garprozeßschrittes einerseits die mittlere Mikrowellenleistung und andererseits die Pausenzeiten zwischen aufeinander folgenden Mikrowellenpulsen gezielt und unabhängig von einander gesteuert oder geregelt werden können, um ein optimales Garergebnis zu erzielen.
3. iii) Garprozeß-Parameter
   Während eines Garprozesses oder Garprozeßschrittes wird unabhängig von der Taktung des gepulsten Mikrowellengenerators die Restzeit des Garprozesses oder Garprozeßschritten von der Steuer- oder Regeleinheit des Gargerätes ermittelt. Eine Anpassung der Mikrowellenleistung in Abhängigkeit der Restzeit als Garprozeß-Parameter läuft beispielsweise wie folgt ab: Sind 80 % der Gesamtzeit abgelaufen, werden die Pausenzeiten der Mikrowellenleistung zum Beispiel um 5 %, erhöht. Eine weitere Verlängerung der Pausenzeiten kann bei Werten von 85 %, 90 % und 95 % der Gesamtzeit erfolgen. Wie bereits zuvor erwähnt, werden durch die Verlängerung der Pausenzeit Hot- und Coldspots im Gargut vermieden, da räumliche Temperaturunterschiede im Gargut, die während der räumlich ungleichmäßig verteilten Mikrowellenbeaufschlagung entstehen, durch thermische Diffusionsprozesse ausgeglichen werden können. Speziell zum Ende des Garprozesses hat das Gargut generell schon eine hohe Temperatur, so daß es daher sehr empfindlich gegenüber weiteren lokalen Temperaturüberhöhungen durch Hotspots reagieren kann.

The course of a cooking process, in which a method according to the invention is used, will be clarified below with reference to an example.

1. i) User input parameters
   In order to cook a chicken, an operator sets desired cooking parameters, for example in the form of a desired type of cooking product or type of food "poultry / roast", a desired browning and a desired core temperature of the food, via an operating device of a cooking appliance before the start of a cooking process selected. Depending on these input user input parameters, a default value for the pulse duration and the pause time of the clocked microwave power is calculated by a control unit of the cooking appliance. In the cooking product "poultry / roast" selected here, for example, the full mean microwave power is determined for the subsequent cooking process by a corresponding duty cycle, since both poultry and roast are relatively insensitive to microwave radiation. The selected target browning has no influence on the timing of the microwave power. In contrast, the duty cycle of the microwave power is changed depending on the selected target value of the core temperature. Thus, increasing the core temperature set point generally increases the average output power of the microwave source. Following this, the cooking process starts with the calculated default values for the pulsed microwave power clocking. The above example thus clarifies the control or regulation of the mean microwave power as a function of user input parameters.
2. ii) food parameters
   In the first few minutes of the mentioned cooking process, the states of the food are recognized. In particular, the cooking appliance detects whether the type of food is actually chicken or roast and whether the food is frozen or fresh. Furthermore, the caliber and the shape of the food, the food load, and the humidity of the cooking chamber, to determine a Gargutgewichtsverlustes recognized. Suitable sensors are used for this purpose.
   Then, the current timing is adjusted again depending on the detected Gargutzustände, that is, depending on Gargut parameters after completion of the respective recognition process.
   If, for example, a frozen chicken is to be cooked, a core temperature of below 0 ° C. is measured, in particular by means of a cooking process probe inserted into the food. Then the previously calculated break times of the pulsed microwave power for temperature compensation between different hot spots in the food are significantly extended, since the thawing of food in general a homogeneous as possible entry of microwave radiation in the food is necessary. If the core temperature, which continues to be controlled during the cooking process, rises above 0 ° C, the pause times are shortened.
   A statement about the size of the chicken is made possible by the caliber detection. The caliber or the size can be done, for example, over the evaluation of the output data of the cooking process sensor over time. If it is now a small caliber, the average microwave power is reduced by adjusting the duty cycle. Alternatively, if a very large caliber is detected, the full nominal average microwave power can be restored.
   The mentioned example illustrates how, as a function of two parameters of the cooking product, namely the measured core temperature and the detected caliber of the food, during a cooking process or cooking process step, on the one hand, the average microwave power and, on the other hand, the pause times between successive ones Microwave pulses can be controlled and controlled specifically and independently of each other to achieve optimum cooking results.
3. iii) cooking process parameters
   During a cooking process or cooking process step, regardless of the timing of the pulsed microwave generator, the remaining time of the cooking process or cooking process steps is determined by the control unit of the cooking appliance. An adaptation of the microwave power as a function of the remaining time as a cooking process parameter runs, for example, as follows: If 80% of the total time has expired, the pause times of the microwave power are increased by 5%, for example. A further extension of the break times can take place at values of 85%, 90% and 95% of the total time. As already mentioned above, the extension of the break time avoids hot spots and cold spots in the food to be cooked, since spatial temperature differences in the food to be cooked, which arise during spatially unevenly distributed microwave application, can be compensated by thermal diffusion processes. Especially at the end of the cooking process, the food in general already has a high temperature, so that it can therefore be very sensitive to other local temperature peaks due to hot spots.

Figur 1

den Verlauf einer Ausgangsleistung eines getakteten Mikrowellengenerators; und

Figur 2

den Verlauf einer Garraumtemperatur und Feuchte.

Further features and advantages of the invention will become apparent from the following description in which an embodiment of the invention with reference to a schematic drawing is explained in detail. Showing:

FIG. 1

the course of an output power of a clocked microwave generator; and

FIG. 2

the course of a cooking chamber temperature and humidity.

The method according to the invention makes it possible, for example, to adapt the microwave clocking as a function of the humidity of the cooking chamber atmosphere in the cooking chamber. This principle is to be illustrated by the example of baked goods or rolls, which are heated in the oven in a dry heat to a cooking chamber temperature GT of 250 ° C. In Fig. 2 is the time course of the target value GT _soll and the actual value GT _is the cooking space temperature GT shown for this case.

After closing the cooking chamber door of a cooking appliance, not shown, at the beginning of the baking process, the actual value of the cooking space temperature GT is regulated to a virtually constant value in the range of the desired value of the cooking space temperature GT _setpoint . In addition, during the cooking process, neither moisture F nor added to the cooking chamber is removed, whereby air circulation in the cooking chamber is generated as part of a recirculation mode. In Fig. 2 It can be seen that from a cooking time of about 8 minutes, the measured actual value of the humidity F _is increased with a first constant increase, with a saturation of the moisture begins later in the course, from about 16 minutes.

If, as in Fig. 2 shown, the moisture in the oven increases later in the cooking process, it is assumed that this evaporation processes are responsible within the food. Thus, the product may be over-cooked in places, especially due to microwave irradiation nonuniformities. In general, when using microwave radiation dehydration both on the surface and in the interior of the food may be possible. At the time of such a moisture increase in the oven, a further addition of microwave radiation can lead to further overcooking or burns of the food, while other parts of the food can still be raw or ungar. If, therefore, such a rise in humidity is detected by means of humidity sensors (not shown) of the cooking appliance, the calculated break times of the pulsed microwave application are prolonged, so that a temperature equalization can take place between differently hot places in the food. Alternatively, the microwave power can be switched off completely.

The features of the invention disclosed in the foregoing description, in the claims and in the drawings may be essential to the realization of the invention both individually and in any combination.

LIST OF REFERENCE NUMBERS

P

instantaneous output power of the microwave generator

P ₁

Peak value of instantaneous power

t

Time

T _pulse

pulse duration

T _break

break time

T ₀

period

GT

Oven temperature

GT _should

Target value of the cooking space temperature

GT _is

Actual value of the cooking chamber temperature

F

humidity

F _is

Actual value of the humidity

Claims (11)

Method for setting the timing of at least one pulsed microwave generator of a cooking appliance as a function of at least one cooking parameter, at least one cooking chamber parameter, at least one user input parameter and / or at least one cooking process parameter, characterized in that the average power and the pause duration between two consecutive pulses of the microwave generator can be independently controlled or regulated. Method according to claim 1, characterized in that
the type of food, such as meat, fish, baked goods or the like,
the initial state of the food, such as frozen or fresh or the starting mass, the starting weight, the starting caliber or the like,
the degree of cooking of the food, such as internal cooking, determined in particular by a core temperature, a cooking value, a pasteurization, a weight loss or the like, and / or the external Gargrad determined in particular by the tanning, crusting or the like, and / or
the load of food in a cooking chamber
is or are determined as food parameters, preferably via at least one first sensor. Method according to claim 1 or 2, characterized in that
a climate parameter, in particular determined by the temperature, the humidity and / or the flow rate of cooking chamber, is determined in the cooking chamber as cooking chamber parameters or, preferably via at least one second sensor. Method according to one of the preceding claims, characterized in that a desired value, such as a desired value of a food parameter, a cooking chamber parameter or the like, and / or a cooking process and / or cooking process step
is input as a user input parameter, preferably with the interposition of an operating device, a device-internal storage device, a gargeräteexternen storage device, the Internet or the like. Method according to one of the preceding claims, characterized in that the duration and / or remaining running time of a cooking process or cooking process step and / or a cooking chamber parameters and / or a food parameter at least two times during a cooking process or cooking process step
is determined as Garprozeß parameter or are, preferably via at least one third sensor. Method according to one of the preceding claims, characterized in that at the beginning of a cooking process or cooking process step, a first default value of the mean power and a second default value of the pause duration in dependence on at least one user input parameter is determined. Method according to claim 6, characterized in that
the first and / or second default value is / are adapted as a function of at least one detected cooking product parameter, a detected cooking chamber parameter and / or a detected cooking process parameter. Method according to one of the preceding claims, characterized in that the pause times are adapted as a function of, in particular temporally changing, thermal diffusion behavior of the food. Method according to one of the preceding claims, characterized in that the microwave generator generates a periodic microwave signal having a substantially rectangular pulse shape, the average power of this signal being adjusted by the ratio between the period duration and the pulse duration. Cooking appliance with at least one microwave generator, a control or regulating device, an operating device, a storage device and at least one sensor for carrying out a method according to one of the preceding claims. Cooking appliance according to claim 10, characterized by
an electric heater, a gas-operated heater, a cooler, a moisture supply device, a moisture removal device, a heat storage device, a cooking-chamber atmosphere circulation device, and a display device.

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