WO2023222408A1

WO2023222408A1 - Operation of a domestic microwave device having an ir camera

Info

Publication number: WO2023222408A1
Application number: PCT/EP2023/061910
Authority: WO
Inventors: Sebastian Sterz; Matthias Vogt; Markus Kuchler; Christian Böttcher
Original assignee: BSH Hausgeräte GmbH
Priority date: 2022-05-17
Filing date: 2023-05-05
Publication date: 2023-11-23
Also published as: DE102022204877A1

Abstract

The invention relates to a method (S1-S11) for operating a domestic microwave device (1) that has a cooking chamber (2), which is acted on by means of microwaves, and at least one digital IR camera (8), wherein, during a treatment process, microwaves are irradiated into the cooking chamber (2) (S3, S11), at least one image of the cooking chamber (2) is recorded by means of the IR camera (8), the pixels of the image corresponding to a respective temperature value, and, when the pixel temperature values of a quantity of pixels that belong to a surface of the product being cooked have reached a specified first quantile condition (S5), the power (P) of the microwaves irradiated into the cooking chamber (2) is adjusted (S6). The invention also relates to a domestic microwave device (1) that has at least one microwave generator (4) for generating microwaves, a cooking chamber (2) which can be acted on by means of the microwaves, at least one digital IR camera (8) and a data-processing device (7) which is configured to carry out the method (S1-S11).

Description

Operating a household microwave oven with an IR camera

The invention relates to a method for operating a household microwave appliance, which has a cooking chamber exposed to microwaves and at least one digital infrared (IR) camera, wherein microwaves are irradiated into the cooking chamber during a treatment process, using the IR camera to produce at least one image is recorded in the cooking chamber, the pixels of which correspond to a respective temperature value. The invention also relates to a household microwave appliance which has at least one microwave generator for generating microwaves, a cooking chamber which can be acted upon by the microwaves, at least one digital IR camera and a data processing device, the data processing device being set up to carry out the method. The invention is particularly advantageously applicable to ovens with a microwave function and also independent household microwave ovens.

Previous methods for regulating the supply of microwave energy so that food to be cooked is heated gently and evenly use average or maximum measured surface temperatures of the food to be cooked. A typical property of microwave devices is the occurrence of local areas of high field strength (so-called "hot spots") in the food to be cooked, which are caused by the field distribution (mode pattern) that occurs in the cooking chamber, which practically represents a cavity resonator. In order to prevent overheating in individual parts of the food and to achieve the most homogeneous possible temperature distribution, turntables can be used, which, figuratively speaking, move the food through the field distribution. For the same purpose, the microwave radiation can be fed into the cooking chamber using rotary antennas, with the field distribution then being figuratively moved by the stationary food being cooked. These movements (turntable and/or rotary antenna) change the impedance of the cooking chamber, which in the case of a magnetron as a microwave source results in a change in the working frequencies due to so-called "load pulling" and thus a change in the resulting mode pattern. However, these tools are often not sufficient to adequately avoid hot spots. This means that individual hot spots can occur on the food to be cooked, where the food may already dry out or burn, and at the same time there may also be cool areas of the food to be cooked which have not yet reached consumption temperature. It can then happen that the supply of microwave energy is stopped without the food being cooked being brought into an edible state.

EP 0 781 072 A1 describes the creation of a two-dimensional temperature image from the movement of a turntable in a microwave oven and the termination of the preparation if a medium target temperature is reached.

US 6,586,714 B discloses how the field of view of an infrared sensor in a microwave oven is changed in order to end a cooking process - in particular when a preset final temperature is reached.

US 6,590,192 B discloses a stopping criterion for a heating process.

EP 3285 548 B1 discloses a defrosting process in a microwave device, which is carried out step by step based on the achieved percentile temperatures of the defrosting material, which are determined by an IR camera.

EP 1 076475 B1 is dedicated to solving the problem of how, in the case of large detection areas, it can be decided whether a detection area shows no food, only partially cooked food or completely cooked food. Heating is discussed in particular up to the point of boiling, in which the heating output is reduced as soon as part of the food is boiling. A defrosting process is also considered.

DE 10 2018221 329 A1 discloses a method for operating a household cooking appliance, comprising at least one food treatment device for treating food located in the cooking space with several parameter configurations, wherein the food to be cooked can be treated differently locally by at least two parameter configurations, and at least one directed into a cooking space Sensor for determining measured value distributions of a surface property of the food to be cooked, wherein in the method the at least one food treatment device is operated for a predetermined period of time with one of the parameter configurations in order to treat the food to be cooked, following the expiration of a period of time by means of the at least one sensor a measured value distribution <V > a surface property of the food to be cooked is determined, a quality value is determined from the measured value distribution <V> and, if the quality value does not meet a predetermined quality criterion, the food treatment device is operated following another of the parameter configurations, the quality value being derived from a comparison of two different scalar variables calculated from the same measured value distribution <V> (x, x) is determined

DE 10 2019 201 332 A1 discloses a household cooking appliance. This has a cooking space heating device which is set up for localized heating of a cooking space and which can be operated with at least two configurations which generate different energy distributions in the cooking space, a temperature detection device which is set up for contactless detection of a heat distribution in the cooking space, a data processing device which is used for Distinguishing a non-food area from at least one area of the cooking space occupied by food from the detected heat distribution is set up and a control device which is used to set a current configuration of the cooking space heating device with a view to increasing an energy output into the recognized food to be cooked and for controlling the cooking space heating device , the temperature detection device and the data processing device is set up, wherein the data processing device is set up to distinguish the non-cooked food area from the cooked food in the detected heat distribution based on a temperature difference between the non-cooked food area and the cooked food.

WO 2020/094573 A1 discloses a method in which a food treatment device is operated for a period of time with a parameter configuration in order to treat food, after which a measured value distribution of a surface property of the food is determined by means of a sensor after the expiration of the time period, from a comparison of the p- th measured value distribution calculates a change pattern with a measured value distribution, and a respective evaluation value is calculated for all change patterns stored so far in the course of this method, which represents a difference between a deviation of a target distribution from the measured value distribution and a deviation of the target distribution from a prediction pattern, the prediction pattern being an overlay the measured value distribution with the associated change pattern, and the parameter configuration is set whose evaluation value meets at least one predetermined criterion. It is the object of the present invention to at least partially overcome the disadvantages of the prior art and, in particular, to provide an improved possibility of heating items to be treated, in particular items to be cooked, using microwaves.

This task is solved according to the features of the independent claims. Preferred embodiments can be found in particular in the dependent claims.

The object is achieved by a method for operating a household microwave appliance which has a cooking chamber exposed to microwaves and at least one digital IR camera, wherein

- microwaves are radiated into the cooking chamber during a treatment process,

- at least one image is taken from the cooking chamber using the IR camera, the pixels of which correspond to a respective temperature value,

- when the pixel temperature values of a set of pixels that belong to a food surface have reached a predetermined ("first") quantile condition, the power of the microwaves radiated into the cooking space is adjusted.

This method has the advantage that an empirical quantile represents a particularly suitable measure for the uniformity of a surface temperature of the material to be treated by microwaves. This advantageously supports the strategy of achieving uniformity in the item to be treated, in particular the item to be cooked, by heat conduction within the item to be treated. It is particularly advantageous to apply heating energy from microwaves to the food to be cooked until a temperature distribution has been achieved that just does not cause drying out/damage to the food to be treated and then to adapt the heating energy to this condition so that hot zones and colder zones through heat conduction within the material to be treated. This means that the entire material to be treated can be heated gently and evenly with little loss of time. This is particularly advantageous for sensitive food, which can suffer irreversible damage if overheated, such as bursting. The quantile evaluation can also significantly increase the stability of the method against interference or outliers.

The household microwave appliance can be a stand-alone microwave appliance or a microwave combination appliance, for example a microwave appliance with additional oven functionality through radiant heaters or an oven with additional microwave functionality.

The microwaves are generated using at least one microwave generator, for example using at least one magnetron or a semiconductor-based microwave generator.

It is a further development that the household microwave oven is equipped with a rotary antenna, a mode stirrer ("stirrer") and/or a turntable for the targeted variation of a field distribution of the microwaves in the cooking chamber relative to a material to be treated. If there are several introduction points or ports, the field distribution can also be achieved by changing an amplitude, frequency and/or phase difference of the microwaves emitted via these introduction points.

The digital IR camera creates an image point or pixel-based thermal image of the cooking space. The measured values assigned to the individual pixels (hereinafter referred to as “pixel temperature values” without limiting generality) correspond to or correlate with a surface temperature of a local area in the cooking space corresponding to the pixel.

If microwaves are irradiated into the cooking chamber during a treatment process, the items to be treated in the cooking chamber are exposed to the microwaves and thereby heated. The material to be treated can be food to be cooked, but is not limited to this and can also be, for example, a water bath, etc. If the material to be treated is food to be cooked, the treatment process can also be referred to as a cooking process. In the following, the invention will be further described without restricting the generality using the food to be cooked as the food to be treated. The fact that the evaluated pixel temperature values belong to a surface of the food to be cooked means, in particular, that only pixel temperature values that measure a surface temperature of the food to be cooked are used for the method. For this purpose, for example, an image section can be selected so that it only captures image points that belong to a food surface. However, accessory supports, parts of the cooking chamber wall and/or parts of the cooking utensils that are not covered by food are masked out in particular. Food recognition is generally known and is described in more detail, for example, in DE 10 2018 221 329 A1 and in DE 10 2019 201 332 A1.

A quantile condition is understood to mean a distribution of the pixel temperature values, which corresponds to a p-quantile T _q (p) with a predetermined quantile value.

In the present case, a p-quantile or simply just a quantile is understood to mean in particular a temperature T _q (p), which divides the pixel temperature values of the set of pixels belonging to the surface of the food to be cooked in such a way that a proportion of p is smaller than the quantile and thus vice versa a proportion of 1-p is equal to or greater than the quantile, where a predetermined number ("p-value") is between 0 and 1. For example, the quantile T _q (p = 0.8) is the temperature value at which 80% of the pixel temperature values are less than T _q (p = 0.8) and 20% of the pixel temperature values are equal to or greater than T _q ( p = 0.8).

A quantile condition Q corresponds to a distribution of the pixel temperature values in which both the p-value p and the quantile value are in the form of the (quantile) temperature T _q | _Q are given themselves. For example, the quantile condition Q is: T _q (p) = T _q | _Q °C, this condition is satisfied if p pixel temperature values are lower than T _q | _Q °C. For example, the quantile condition may have been specified as T _q (0.8) = 60 °C, i.e. to the distribution of the pixel temperature values in which 80% of the pixel temperature values are below 60 °C and 20% of the pixel temperature values are 60 °C have been reached or exceeded.

That the pixel temperature values meet the first quantile condition QT _q (pi) = T _q | Qi with pi the corresponding predetermined p-value and T _q | _Qi have "reached" the associated predetermined quantile value, means in particular that at least the proportion (1 -pi) of the set of pixel temperature values the quantile value T _q | _Qi has reached or exceeded.

The type of quantile is fundamentally not limited. However, it has turned out that the method with percentiles can be implemented particularly advantageously. The set of pixel temperature values of the surface of the food to be cooked can be divided into 99 percentiles, where p can take the values 0.01, 0.02, ..., 1, alternatively 100 percentiles if the value 1 is also to be permitted for p .

It is an embodiment that when the pixel temperature values have reached the first quantile condition, the power of the microwaves irradiated into the cooking space is reduced, and then when the pixel temperature values have fallen to a predetermined second quantile condition or the first quantile condition is no longer met, the power of the microwaves radiated into the cooking space is increased again. This has the advantage that - especially with magnetrons - an easy-to-implement equalization of the food temperature can be achieved through heat conduction in the food itself. The food to be cooked is subjected to microwave heating energy until a temperature distribution is reached that just does not cause drying out and/or damage to the food to be cooked (represented by the first quantile condition) and the microwave power is then reduced or even switched off completely. Heat from hot zones of the food is then transferred to surrounding, cooler areas of the food to be cooked through heat conduction, causing the temperature in the hot zones to drop. When the second quantile condition occurs after a sufficient drop in temperature in the hot zones, more microwave energy is supplied again until the first quantile condition is reached again, etc. This process can be repeated until a certain termination criterion is met. This means that the entire food can be heated gently and evenly with little loss of time. This embodiment can also be viewed as a hysteresis-like exposure to microwave energy in the manner of a two-point controller. In general, the microwave energy - especially after the first quantile condition has been reached - not only needs to be switched gradually between two values, but can also, for example, depend on the distance between the measured quantile T _q and the predetermined quantile value T _q | QI and/or T _q | Q2 can be set, for example depending on the difference |T _q | QI - T _q | or |T.| Q2 - T _q |. The microwave energy can then be used, for example, in several steps, adjusted continuously or quasi-continuously. In one example, for example, the microwave energy could be (quasi-)continuously reduced from a higher power level 2 to a lower power level 1 as the measured quantile approaches the first quantile condition, etc.

Reducing the power of the microwaves irradiated into the cooking space can therefore include stopping the emission of the microwaves into the cooking space, or alternatively reducing it to an absolute or percentage value greater than zero.

With the second quantile condition Q2: T _q (P2) = T _q 102, analogous to the first quantile condition Qi, its quantile value T _q 102 itself and its p-value P2 are given.

The state that the pixel temperature values have "dropped" to the second quantile condition means in particular that at least the proportion P2 of the set of pixel temperature values has fallen below the predetermined quantile value T _q 102 of the second quantile condition. For example, T _q | _Q2 = 50 °C with P2 = 0.8, the pixel temperature values or their distribution have fallen to the second quantile condition if at least 80% of the pixel temperature values have fallen below 50 °C.

It is an embodiment that a predetermined quantile value T _q | _Qi of the first quantile condition Qi is greater than a predetermined quantile value T _q 102 of the second quantile condition Q2 and/or a p-value pi of the first quantile condition Qi is smaller than a p-value P2 of the second quantile condition Q2, the first quantile is greater than the second Quantile (i.e. T _q | QI > T _q | Q2 applies) and/or a p-value of the first quantile is smaller than a p-value of the second quantile (i.e. pi < P2 applies). The first relationship can also be written as T _q | QI = T _q 102 + TH can be expressed with TH a "hysteresis temperature". The hysteresis temperature TH indicates the cooling of the food, after which the energy supply is resumed or increased from above.

It is an embodiment that the quantile value T _q | _Qi of the first quantile condition Qi is greater than the quantile value T _q 102 of the second quantile condition Q2 and the p-values of the two quantile conditions Qi and Q2 are the same, so pi = P2 applies. This can advantageously be implemented particularly easily. It is an embodiment that when the pixel temperature values have fallen to the second quantile condition, the power of the microwaves irradiated into the cooking space is increased to a value that is lower than the value of the power set before the first quantile condition was reached for the first time. This advantageously combines rapid heating until the first quantile condition is reached with subsequent gentle heating after the heating breaks in a simple manner. Furthermore, the throttled power supply advantageously offers more time for the optimization process, particularly when using controlled methods - for example as described in WO 2020/094573 A1 - and thus a better overall result of the cooking process.

For example, after the start of a cooking process, microwaves can be radiated into the cooking space at a first power level, the power supply can be stopped after the first quantile condition has been met for the first time and can be resumed after the second quantile condition has been met, but with a second, lower power level. In all subsequent off and on cycles, the microwaves can be radiated into the cooking chamber at the second, lower power level, each time the second quantile condition is met. But it is also possible to vary the power levels even further. This embodiment can also be expressed in such a way that the power of the microwaves radiated into the cooking space after the first quantile condition is reached for the first time is lower than the value of the power set before the first quantile condition is reached for the first time.

However, it is also a further development that, when the pixel temperature values have fallen to the second quantile condition, the power of the microwaves irradiated into the cooking space can be set back to the original value that was present before the first quantile condition was reached for the first time.

It is an embodiment that when the pixel temperature values have reached the first quantile condition (and in particular in this embodiment the only predetermined quantile condition), the power of the microwaves radiated into the cooking space is adjusted, in particular regulated, so that the pixel temperature values be kept at the first quantile condition, which then corresponds to a target temperature distribution. The first quantile condition then corresponds to one State in which the power input through microwaves into the food to be cooked and the release of heat from the hot zones through heat conduction, evaporative cooling and heat radiation are balanced. This has the advantage that food can be heated particularly quickly and gently. This configuration is particularly advantageous in connection with one or more semiconductor-based microwave generators, which, in contrast to typical magnetrons, can have their power output regulated as desired. With semiconductor-based microwave generators, for example, power outputs are possible that can precisely balance the release of heat and the power consumption at approx. 100 W, depending on the food being cooked.

It is an embodiment that a cooking process is ended when a difference AT _q between a further measured ("third") quantile T _q (pa) and yet another measured ("fourth") quantile T _q (P4), whose p -Value p4 is smaller than a p-value pa of the third quantile, reaches or falls below a predetermined value. This difference AT _q = T _q (pa) - T _q (P4) is a measure of how closely the temperatures of hot and cold zones on the surface of the food to be cooked have already converged. The smaller the difference AT _q is, the greater the uniformity of the temperatures in the food. So pa > P4 applies. The quantile values of T _q (pa) and T _q (P4) are not specified as with a quantile condition, but are determined each time from an IR image, that is, measured or calculated.

It is an embodiment that the third quantile corresponds to the predetermined quantile value of the first quantile condition, i.e. T _q (pa) = T _q | Qi applies.

It is an embodiment that the cooking process is ended when the difference AT _q between the third quantile and the fourth quantile measured at the time the first quantile condition Qi is reached has fallen to a predetermined percentage value, for example to 50% of the value at the time of first reaching the first quantile condition Qi. However, in principle any other suitable time can also be selected for the initial or reference difference. It is an embodiment that the cooking process is ended when the difference AT _q = between the third quantile T _q (pa) and the fourth quantile T _q (P4) reaches or falls below a predetermined absolute value, for example X °C.

It is a further development that the cooking process is ended when a period of time has been reached or exceeded since the first quantile condition was first reached (i.e. since the end of the initial heating process). This is advantageous in order to avoid the possibility that the method remains in a state in which the other termination criteria are never reached or fulfilled ("infinite loop") and/or a user becomes impatient.

It is an embodiment that at least one process value is set depending on the item to be treated with microwaves, for example depending on a type of item to be cooked, a type of preparation and/or a cooking result. Such at least one method value can, for example, be the p-values pi, p2, pa and/or p4 and/or the quantile values T _q | _Qi and/or T _q | Q2 or the hysteresis temperature TH include. This in turn advantageously allows different heating strategies that are adapted to the respective food to be cooked to be carried out.

If the household microwave oven also has an optical camera, program selection can also take place using image recognition.

It is a further development that a warming function is also implemented. If, for example, the user forgets to remove the food after the cooking process described above has ended, the quantile value Ti | QI can be noticeably reduced, for example from 90°C to 60°C. This means that the food is not “cooked to ruin” even if it is kept warm for a longer period of time.

The above method is particularly suitable in conjunction with an optimized control of the microwave distribution as described in WO 2020/094573 A1. A system expansion of WO 2020/094573 A1 with additional application of the present method offers a significant expansion of the areas of application. Even standing alone, that is, without a stepper motor, which is a necessary requirement in WO 2020/094573 A1, The quality of the food preparation can be significantly improved. This allows costs to be reduced and the system to be simplified.

The task is also solved by a household microwave oven that is set up to carry out the method described above. The household microwave oven can be designed analogously to the method and vice versa, and has the same advantages.

So it is an embodiment that the household microwave appliance has at least one microwave generator for generating microwaves, a cooking chamber that can be acted upon by the microwaves, at least one digital IR camera and a data processing device. The data processing device is in particular set up, for example programmed, to carry out the method as described above.

It is a further development that the microwave generator is a magnetron. It is a further development that the microwave generator is a semiconductor-based microwave generator.

The characteristics, features and advantages of this invention described above and the manner in which they are achieved will be more clearly and clearly understood in connection with the following schematic description of an exemplary embodiment, which will be explained in more detail in connection with the drawings.

Fig. 1 shows a sketch of a household microwave oven as a sectional view in side view;

Fig.2 shows a possible sequence of the method according to the invention; and

Fig. 3 shows a plot of various values occurring during the process against the duration of a cooking process.

Fig.1 shows a household microwave oven 1 as an example in the form of an oven with microwave functionality. The microwave oven 1 has a cooking space 2 for accommodating food G, which can be closed by a front door 3. The cooking chamber 2 can be acted upon by microwaves, which are generated by a microwave generator 4, through a wave guide 5 to an outlet opening provided with a rotary antenna 6 and radiated there into the cooking chamber 2. The microwave generator 4 can be controlled, for example, by a control device 7. The food G to be cooked is shown here as an example as white sausages floating in a water bath (container S filled with water W).

The household microwave oven 1 also has a digital IR camera 8, which can also be controlled by the control device 7. The IR camera 8 is set up to record a pixel-like image from the cooking space 2 including the food G to be cooked. The number of pixels whose values correspond to respective local temperatures (“pixel temperatures”) is advantageously in the range of several hundred or thousand pixels, so that the image shows a high-resolution heat distribution.

The image can be evaluated in the control device 7, for example by identifying pixels associated with the food G to be cooked in the image and subsequently only these pixels are used to carry out the present method, but, for example, no pixels that represent a food carrier R like a Show the baking tray or a wire rack or a wall of the cooking space 2.

The control device 7 can serve in particular as a data processing device that is set up to carry out the method according to the invention.

Fig. 2 shows a possible sequence of the method according to the invention, which is explained in more detail below by way of example with reference to the household microwave oven 1. Fig. 3 shows a plot of a temperature in °C (left ordinate) and a power level P in arbitrary units (right ordinate) against a duration t of a cooking process in s.

In step S1, the process is started with the food G to be cooked in the cooking chamber 2.

In step S2, the user can make a program selection, for example with regard to a type of food to be cooked (here: sausage), a type of preparation (for example, warm it up in a water bath ready for consumption). The control device 7 then selects suitable operating parameters such as the first quantile value T _q | based on the program _Qi and the p-value pi of the first quantile condition Qi, the hysteresis temperature TH and power level(s) P. In the following, percentiles are used as quantiles purely as examples.

The food G chosen here as an example represents Munich white sausages that have been placed in warm tap water W in a microwave-transparent and uncovered container S in the cooking chamber 2. White sausages are very sensitive and react very quickly to overheating by - irreversibly - bursting open - and should still have the highest possible consumption temperature. In this case, a first quantile condition Qi: Tq (0.99) = 80 °C and a hysteresis temperature TH = 8 °C or a second quantile condition Q2: T _q (0.99) = 72 °C have proven to be particularly advantageous . Since the white sausages swim in water, the surface is also recorded. With T _q | _Qi = 80 °C ensures that no small, selective overheating of the white sausages occurs, as otherwise a bursting would have to be expected at this point well below the boiling temperature of water. It is advantageous not to use the maximum measured temperature value - i.e. T _q (pi = 1) - since a control with pi = 0.99 is more robust against measurement errors or irrelevant points of overheating (e.g. against individual, boiling drops on the dishes or areas of the food carrier R that are not 100% masked out, etc.).

In step S3, the energy supply is started by irradiation of the microwaves and thus also the cooking process as such. This corresponds to the time t = 0 s in Fig.3. The power level P is set here to a high power level 2, e.g. to 640 W, in order to achieve a quick initial warm-up.

In step S4, a thermal image is recorded using the IR camera 8, and the control device 7 evaluates the pixel temperature values empirically by forming percentiles at the p-value pi = 0.99. The control device 7 therefore calculates the temperature T _q at which 99% of the pixel temperature values assigned to the food G and the water W are below this temperature T _q . This temperature corresponds to T _q the calculated (not predetermined) quantile of the amount of pixel temperature values assigned to the food G and the water W with a p-value of 0.99 (0.99 quantile). If step S4 has a non-negligibly short time duration, it can be implemented at the same time as a waiting step, for example with a waiting period of 1 s to 5 s. Alternatively, step S4 may be followed by a dedicated waiting step (not shown).

In step S5 it is checked whether the newly measured or calculated quantile T _q (0.99) determined by the control device 7 from each of the IR images has reached or exceeded the first quantile condition Q1, i.e. whether the measured quantile T _q ( 0.99) > T _q | QI = 80 °C applies. If this is not the case (“N”), the process branches back to step S4. However, if this is the case and 99% (or less) of the pixel temperature values are below 80 ° C or 1% (or more) of the pixel temperature values are above 80 ° C, the process branches to step S6. This is the case here at t = 109 s.

In step S6, the microwave radiation is stopped or paused, as shown, or alternatively just reduced. As a result, the food G cools down and the warmer zones lose energy to the cooler zones through heat conduction.

Subsequently, in step S7, analogous to step S4, a thermal image is again recorded and evaluated using the IR camera 8.

It is then checked in step S8 whether an abort criterion for ending the cooking process has been reached. If this is the case (“Y”), the cooking process is ended in step S9.

However, if the termination criterion in step S8 has not yet been reached ("N"), a check is made in step S10 as to whether the measured or calculated quantile T _q (0.99) corresponds to the value T _q | Q2 = 80 °C - TH = 80 °C - 8 °C = 72 °C or to the second quantile condition T _q (0.99) = T _q | Q2 = 72 °C has dropped. If this is not the case (“N”), the process branches back to step S7.

However, if this is the case ("J"), as here after t = 126 s, the microwave irradiation is resumed or increased again in step S11. In the present case, however, in a power level P = 1, at which a lower microwave power is irradiated into the cooking chamber 2 than at the initial power level P = 2, for example 360 W.

The next step is to step S4. When the first quantile condition Qi: T _q (0.99) = 80 °C is reached again after 166 s, another phase occurs without energy supply, etc. This process is continued iteratively until the termination criterion in step S8 is met. The entire course of the measured quantile T _q (0.99) is shown in Fig. 3 as the top curve, the course of the power levels P as a dotted line.

The course of a "fourth" quantile T _q (p = 0.10) is also shown as an example in FIG. 3, which corresponds to the measured or calculated temperature below which 10% of the pixel temperature values lie. This quantile T _q (0.10) corresponds to the maximum temperature of the coldest 10% of the pixel temperature values. Derived from this, the difference AT _q = T _q (0.99) - T _q (0.10) can be formed, which is the temperature difference between the subsets of the 1% hottest and 10% coldest measuring points. T _q (0.99) is a "third" quantile, which corresponds purely by way of example to the "first" quantile T _q (pi) of the first quantile condition Q1. Alternatively, another third quantile T _q (ps) could be chosen, for example with pa = 0.90 or 0.95.

The difference AT _q tends to decrease as the cooking process progresses, because due to the heat conduction within the food G, areas that cannot be heated or only poorly heated by microwave radiation are also heated. Often there is no mode pattern in the cooking chamber 2 for certain zones of the food G to be cooked, which could heat them up. These cold zones can hardly or not be heated by microwave radiation, but can be heated effectively via heat conduction from neighboring hot zones. The hot zones can be heated cyclically, for example, by the uncontrolled rotation of a turntable or a rotary antenna. The heating can alternatively or additionally be carried out by controlled processes - for example as described in WO 2020/094573 A1.

From this, termination criteria that indicate completion of the cooking process can be formulated from the relationship between T _q (ps) and T _q (P4) with ps > P4. These termination criteria represent how closely the temperatures of hot and cold zones have already converged. Typical values are, for example, ps = 0.90, 0.95 or 0.99 and p4 = 0.05, 0.10 or 0.20.

For example, a termination criterion can be that the current difference AT _q has reduced by a certain percentage compared to the difference AT _q when the first quantile condition T _q (0.99) = 80 ° C is reached for the first time at t = 109 s, e.g around the Half. In Fig. 3, this corresponds to the process ending after approximately 300 seconds, since the difference AT _q then reaches or falls below 10 ° C for the first time, which corresponds to half of the value AT _q at time t = 109 s.

Another termination criterion can be that the difference AT _q reaches or falls below a predetermined value, for example 9 °C. This is the case in Fig.3 after t = 410 seconds.

In general and therefore not limited to the exemplary embodiment shown, can

- in particular in addition to the above termination criteria - one or more termination criteria are defined, which include a maximum operating time of the cooking process and / or a maximum or minimum number of resumptions of the heating cycle S6 / S11. For example, a cooking process can be limited to a maximum of ten minutes and/or include no less than two waiting cycles that were ended with step S11. Falling below a difference AT _q can also be used as a termination criterion.

In general, the termination criteria can be part of the program selection made in step S2 and can be adapted to the individual application.

It can also be advantageous to store the parameter sets as fixed programs for respective dishes in a data memory of the household cooking appliance 1, for example in the control device 7, or to offer them to a user as presets. Such parameter sets and/or presets can be, for example:

- "Gentle heating": QT _q (0.99) = 80 °C, TH = 8 °C, power level P = 2 until Qi is reached for the first time, then power level P = 1;

- "Balanced": QT _q (0.97) = 85 °C, TH = 5 °C, power level P = 2 until Qi is reached for the first time, then power level P = 1 ;

- "Turbo": QT _q (0.95) = 90 °C, TH = 10 °C, power level P = 2 until Qi is reached for the first time, then power level P = 2. Of course, the present invention is not limited to the exemplary embodiment shown.

In another exemplary embodiment, not shown, "robust" food such as a soup or stew can be heated. Irreversible damage to the food is not to be expected here. The main aim is to prevent local overheating from drying out or causing it to boil Splashes occur that contaminate the cooking chamber 2. A parameter set adapted for this could be:

Qi: T _q (0.95) = 90°C, T _H = 10°C.

Here, after the cooking process has started, the food to be cooked is heated until 5% of the pixel temperature values have reached or exceeded a value of 90 °C. Experiments have shown that in standard preparation vessels, dishes such as minced meat sauce, soup or stew with these values are on the verge of going locally to a boiling state. The above parameter set ensures maximum power input. The energy supply is now switched off or greatly reduced, and the food is then warmed up through heat conduction and also cools down on the surface. As soon as the second quantile condition Q2: T _q (0.95) = 80°C is reached or fallen below, the energy supply starts again.

In general, "a", "an", etc. can be understood to mean a singular or a plural, in particular in the sense of "at least one" or "one or more", etc., as long as this is not explicitly excluded, for example by the expression "exactly a" etc.

A numerical statement can also include exactly the number specified as well as a usual tolerance range, as long as this is not explicitly excluded. Reference symbol list

1 household microwave oven

2 cooking space

3 door

4 microwave generator

5 wave guide

6 rotary antenna

7 control device

8 IR camera

G Cooked food

P power level

R Food carrier

S vessel

S1-S11 Process steps t Duration of a cooking process

T temperature

T _q quantile

W water

AT _q difference of quantiles

Claims

Patent claims

1. Method (S1-S11) for operating a household microwave oven (1), which has a microwave-exposed cooking chamber (2) and at least one digital IR camera (8), whereby

- microwaves are irradiated into the cooking space (2) during a treatment process (S3, S11),

- using the IR camera (8), at least one image is recorded from the cooking chamber (2), the pixels of which correspond to a respective temperature value, and

- when the pixel temperature values of a set of pixels that belong to a food surface have reached a predetermined first quantile condition (S5), the power (P) of the microwaves radiated into the cooking space (2) is adjusted (S6).

2. Method (S1-S11) according to claim 1, in which

- then when the pixel temperature values have reached the first quantile condition (S5), the power of the microwaves irradiated into the cooking space is reduced (S6), and

- then, when the pixel temperature values have fallen following a second quantile condition (S10), the power of the microwaves radiated into the cooking space is increased again (S11).

3. Method (S1-S11) according to claim 2, in which a predetermined quantile value of the first quantile condition is greater than a predetermined quantile value of the second quantile condition and / or a p-value of the first quantile condition is smaller than a p-value of the second quantile condition.

4. Method (S1-S11) according to claim 3, in which the quantile value of the first quantile condition is greater than the quantile value of the second quantile condition and the p-values of the first quantile condition and the second quantile condition are the same.

5. Method (S1-S11) according to one of claims 2 to 4, in which when the pixel temperature values have fallen to the second quantile condition (S10), the power (P) of the microwaves irradiated into the cooking space is increased again ( S11), in particular is increased to a value (S11) which is lower than the value of the power (P) set before the first quantile condition was reached for the first time.

6. The method according to claim 1, in which, when the pixel temperature values meet the first quantile condition (S5), the power of the microwaves irradiated into the cooking chamber is adjusted so that the pixel temperature values are kept at the first quantile condition.

7. Method (S1-S11) according to one of the preceding claims, in which the cooking process is ended (S9) when a difference (AT _q ) between a measured third quantile and a measured fourth quantile, the p-value of which is smaller than a p-value of the third quantile, reaches or falls below a predetermined value (S8).

8. Method (S1-S11) according to claim 7, in which the third quantile corresponds to the predetermined quantile value of the first quantile condition.

9. Method according to one of the preceding claims, in which the cooking process is ended (S9) when the difference (AT _q ) between the third quantile and the fourth quantile measured at the time the first quantile condition is reached has fallen to a predetermined percentage value ( S8).

10. Method (S1-S11) according to one of the preceding claims, in which the cooking process is ended (S9) when the difference (AT _q ) between the third quantile and the fourth quantile reaches or falls below a predetermined absolute value (S8).

11. Method (S1-S11) according to one of the preceding claims, in which the cooking process is ended (S9) when a period of time since the first quantile condition is reached is reached or exceeded (S8).

12. Method (S1-S11) according to one of the preceding claims, in which the quantiles are percentiles.

13. Method (S1-S11) according to one of the preceding claims, in which at least one method value is set depending on the material to be treated with microwaves (S2).

14. Household microwave oven (1), comprising

- at least one microwave generator (4) for generating microwaves,

- a cooking space (2) that can be acted upon by microwaves,

- at least one digital IR camera (8) and

- A data processing device (7) which is set up to carry out the method (S1-S11) according to one of the preceding claims.