Determining a temperature during a microwave treatment

Abstract

The invention relates to a method (S1 - S8) for determining a temperature of a liquid product (W) during a microwave treatment (S3 - S8) in a cooking chamber (2) of a domestic microwave appliance (1). In the method, a mixing temperature (Tmix) of the liquid product (W) is calculated from at least one measurement value (Tstart, Tend_init, ∆Tinit, Takt, p) of the liquid product (W), of a vessel (G) accommodating the liquid product (W) and / or at least one measurement value of the cooking chamber (2). A domestic microwave appliance (1) is designed to carry out the method (S1 - S8).

Description

[0001] Determining a temperature during a microwave treatment

[0002] The invention relates to a method for determining the temperature of a product during microwave treatment in a cooking chamber of a household microwave oven. The invention also relates to a household microwave oven configured to carry out the method. The invention is particularly advantageously applicable to ovens with a microwave function.

[0003] EP 0 781 072 A1 describes a microwave oven comprising a number of IR sensor elements for obtaining temperature information from discrete detection areas within the oven's cooking zone and generating a two-dimensional temperature image of the cooking zone. Based on this temperature image, necessary loading parameters for controlling automatic heating processes in the oven can be calculated.

[0004] EP 1 921 384 A1 discloses a device for determining the temperature inside a food item. The device has at least one temperature sensor for detecting at least one surface temperature of the food item and / or an ambient temperature of the food item, in particular at a measuring location within a cooking chamber surrounding the food item, preferably with an ambient temperature sensor arranged at the measuring location. Furthermore, the device comprises at least one distance sensor for detecting one or a plurality of distances between the distance sensor, on the one hand, and one or a plurality of distance measuring points on the surface of the food item, on the other hand.Furthermore, the device comprises at least one time-measuring device for recording the time during preparation of the food and at least one calculation device for calculating the temperature inside the food from the surface temperature of the food and / or ambient temperature, the distance or the plurality of distances, the time, and an initial temperature of the food. Furthermore, a method for determining the temperature inside a food is disclosed. The object of the present invention is to at least partially overcome the disadvantages of the prior art and, in particular, to provide an improved method for preparing liquid food by microwave treatment.

[0005] This object is achieved according to the features of the independent claims. Preferred embodiments can be found in particular in the dependent claims and the description.

[0006] The problem is solved by a method for determining the temperature of a liquid product during microwave treatment in a cooking chamber of a household microwave oven, in which a mixing temperature of the liquid product is calculated from at least one measured value of the liquid product, a container containing the liquid product, and / or at least one measured value of the cooking chamber. The temperature of the liquid product to be determined is therefore the mixing temperature.

[0007] This provides the advantage that the consumption temperature of a liquid product, as perceived by a user's senses, namely the mixing temperature, can be estimated and used, for example, to control a microwave treatment, even though the mixing temperature only becomes apparent when the liquid product is stirred, usually after the treatment process has been completed. In contrast, the (re-)heating of liquids has so far been a process that could not be mapped with sufficient precision, even by advanced sensor technology. In particular, the highly variable layering properties depending on the container have prevented more precise control of the mixing temperature, which is crucial for consumption.

[0008] The method, however, advantageously makes it possible to offer a user a very precise device function for heating liquid material to a target mixing temperature. This avoids a situation where a specific surface temperature is measured, but the user receives a noticeably lower mixing temperature after stirring the material. The user would then have to microwave the material again to achieve the desired mixing temperature, which can be avoided by the present method, thus significantly simplifying the work. The method utilizes the knowledge that microwave treatment of liquid material often results in temperature stratification, in which an uppermost layer (usually thinner than 1 mm), whose temperature can often be measured by a non-contact temperature sensor, is noticeably warmer than deeper layers (e.g., between a few °C and a few tens of °C).This can be due, for example, to the effective absorption of microwaves in the uppermost layer and also to the rising of warmer liquid. The method pursues the advantageous inventive goal of estimating the mixing temperature by calculation from measured values ​​recorded during microwave treatment.

[0009] Furthermore, this method is advantageously easy to implement. For example, if the household microwave already has an IR camera, it can be implemented as a purely software solution in a further development.

[0010] Liquid goods can be understood as fluid goods such as water, water-based beverages (coffee, tea, milk, cocoa, etc.) or soup, etc., and / or viscous goods such as baby food, etc. Especially with baby food, it is a well-known phenomenon that the upper layer can become very hot during microwave treatment, while the lower layers remain cold.

[0011] The mixing temperature is understood in particular to mean a temperature of the liquid material which results from mixing or stirring and thus homogenisation of the temperatures in the liquid material.

[0012] The household microwave appliance can be a pure microwave appliance or a combination appliance, for example, a microwave appliance with an additional oven function, e.g., by providing at least one resistance heating element, or an oven with an additional microwave function. The household microwave appliance can also additionally have a steam cooking function.

[0013] During microwave treatment, the product in the cooking chamber is irradiated with microwaves. Calculating the mixing temperature of the liquid product involves, in particular, calculating the mixing temperature from the at least one measured value, in particular using a formula with the at least one measured value as the input variable. In particular, it is not intended to use the at least one measured value as such as the mixing temperature.

[0014] The at least one measured value can be a directly measured value (e.g. a surface temperature) and / or a measured value derived from at least one directly measured value (e.g. an averaged value, a quantile value, a temperature difference, etc.).

[0015] In one embodiment, the at least one measured value comprises at least one measured value of the liquid material or a measured value sensed on the liquid material. In one embodiment, the at least one measured value comprises at least one measured value of the container in which the liquid material is located, e.g. a glass, a beaker, etc. In one embodiment, the at least one such measured value comprises at least one of the measured values ​​from the group of surface temperature, ultrasonic properties and / or surface area and / or volume. This is because it has been shown that these measured values ​​enable a particularly reliable estimation or calculation of the mixing temperature.

[0016] In a further development, the temperature(s) can be measured by a non-contact cooking chamber temperature sensor. In a further development, the non-contact cooking chamber temperature sensor is a pixel-based IR camera directed into the cooking chamber, in particular also installed in the area of ​​the cooking chamber. Such IR cameras are used in particular for measuring surface temperatures. The household microwave oven can have one or more IR cameras. In a further development, at least one IR camera is arranged in the area of ​​a ceiling of the cooking chamber, which is particularly advantageous for measuring the upper surface temperature of the product.

[0017] It is also possible to install at least one IR camera on the side of the cooking chamber. This can offer the advantage of recording the vertical temperature profile of the vessel particularly easily and reliably, which can then be used to calculate the mixing temperature.

[0018] The ultrasonic property can, for example, be the density and / or fill level of the liquid. The household microwave oven can be equipped with an ultrasonic sensor to measure these properties.

[0019] In one embodiment, the at least one measured value of the cooking chamber comprises at least one measured value from the group of cooking chamber temperature, air humidity, and / or oxygen content. The cooking chamber temperature can be measured using a cooking chamber temperature sensor, and the air humidity and / or oxygen content can be measured using a lambda sensor, for example.

[0020] A further development is that at least one measured value represents a microwave power reflected back from the cooking chamber. The household appliance can be equipped with a corresponding RF sensor that operates based on the scattering parameters. In particular, this can take advantage of the fact that the dielectric constant changes noticeably with the mixing temperature.

[0021] A further development is that the measured value is determined using at least one non-contact sensor. For example, a wired or wireless core temperature probe (also known as a meat thermometer or "meat probe") can be immersed in the liquid product. This is particularly advantageous if the core temperature probe has several temperature sensors distributed along its length, as the mixed temperature can then be relatively easily derived as a—possibly weighted—average value.

[0022] It is an embodiment that the mixing temperature of the liquid material is calculated by estimating at least one surface temperature (e.g. the current surface temperature Takt) of the liquid material and correcting this at least one surface temperature by means of a correction function Tk Orr is corrected, whereby the correction function Tcorr is a function of at least one other of the measured values. This advantageously enables the determination of the correction function using wireless IR measurement. Due to the wide range of deviations between the measured temperature and the mixed temperature, the use of a correction function enables a much better estimate than with a standardized, fixed correction value.

[0023] The at least one surface temperature can be, for example, a temperature averaged from a measured temperature distribution, a quantile temperature of the temperature distribution, etc.

[0024] The at least one other of the measured values ​​can be at least one measured value recorded by a sensor other than the sensor measuring the at least one surface temperature (in particular an IR camera).

[0025] The at least one other of the measured values ​​can additionally or alternatively be at least one measured value derived from the at least one surface temperature, which in particular does not itself correspond to a temperature, for example a size value of a surface of the liquid material determined from a heat distribution.

[0026] The fact that the correction function Tcorr is a function of at least one other of the measured values ​​can mean that the determined or measured at least one surface temperature itself is not an influencing variable or parameter of the correction function Tcorr. Alternatively, the at least one surface temperature itself can also be an influencing variable of the correction function Tcorr. For example, if the at least one surface temperature is or includes a current surface temperature Takt, Tcorr = f (Takt) can apply.

[0027] It is a further development that the mixing temperature T m ix is ​​determined by subtracting the correction function Tkorr from the measured surface temperature T a kt according to

[0028] T mix — Clock " T corr is subtracted, which is advantageously particularly easy to implement.

[0029] It is a design that the correction function has as input variables at least the measured variables - initial temperature T st type of liquid product before or at the start of microwave treatment,

[0030] - temperature increase ATinit of the liquid material measured during an initial period,

[0031] - current temperature of the liquid goods and / or

[0032] - size value p of the liquid good, so Tkorr = f (Tstart, ATinit, Takt, P, ...) applies.

[0033] This design has the advantage that the mixing temperature can be estimated with high accuracy and independently of the liquid container used, purely from the measured values ​​of the surface temperature of the liquid material.

[0034] The temperature increase ATinit measured during the initial period characterizes how quickly the material initially heats up.

[0035] The quantity value p can be determined, for example, by evaluating a temperature distribution, object detection in an image, laser scanning, input by a user, etc.

[0036] The size value p is a measure of the size of the vessel to be heated and / or the material contained therein. This value can be specified in any volume and / or area units (e.g., square centimeters or pixel counts). The size value p can be measured, for example, using an optical camera (e.g., with object recognition), a laser scanner, etc., can be determined as the number of pixels of a camera operating in the visible range and / or an IR camera, can be determined as the area assigned to these pixels, etc.

[0037] In one embodiment, the initial time period is the duration of an initial scan. The initial scan corresponds to an initial phase of the microwave treatment or microwave treatment process, in which the measured values ​​required to carry out the subsequent process are recorded. Thus, the initial scan can be used to determine irradiation parameters that produce a particularly effective mode image for heating. The initial scan can also be used to record the measured values ​​required to establish the correction function. Particularly advantageous time periods for the initial scan are typically between 15 and 30 seconds. The temperature increase ATinit during the initial scan is then ATjnit. — Tend init " Tstart with Tend init the temperature at the end of the initial scan and the assumption that the microwave treatment starts with the initial scan.

[0038] One embodiment allows the input variables of the correction function to be measured using an IR camera with pixel-like resolution. This advantageously eliminates the need for additional sensors to determine the correction function, and enables contactless measurement. In particular, the variables Tstart, ATjnit, Takt, and p can be measured using a single IR camera. This camera is advantageously positioned near the ceiling of the cooking chamber and can thus also view directly into the vessels from above.

[0039] In a further development, at least one of the temperatures, in particular the temperature increase ATinit, is determined based on or as a quantile temperature, in particular a percentile temperature, of a temperature distribution comprising several pixels. This advantageously achieves a particularly reliable measurement. The temperature increase ATinit resulting, for example, from the temperature increase of a p80 percentile temperature corresponds to the temperature increase at which 20% of the IR camera pixels measuring the liquid material are above the p80 percentile temperature and 80% are below it. This advantageously allows the effect of temperature outliers to be dampened.

[0040] It is a design that the correction function according to with a, r, n, m, c and T ma x specified correction parameters. This has proven to be particularly accurate and reliable, or rather robust. This variant for Tk OrrHowever, this is only one possible formulation for mathematically approximating the relationship between mixing and surface temperature. The correction parameters can, for example, be precalculated and stored in the microwave. The above configuration is illustrated below using an example calculation, in which a test heating process of 280 ml of water in a "large coffee cup" is considered. The cup is filled with 280 ml of tap water, placed in the microwave, and the process is started after a target mixing temperature T Z iei has been defined.

[0041] The initial scan, which lasts 30 seconds, produces a mask or subset with p = 130 image points or pixels from an IR camera from the - typically larger - total set of all image points of the IR camera. These specific 130 image points have been identified as belonging to the water and therefore measure the temperature at the water surface. Thus, p is also a measure of the size of the liquid surface. In contrast, the remaining image points have been classified as not belonging to the water, but can be assigned to, for example, the coffee cup, a cooking chamber wall, etc. The image points classified as belonging to the water can, for example, have been identified by the fact that they show the highest temperature increase / fastest temperature rise during the initial scan and possibly also by correlations.

[0042] During the initial scan, an increase in the p80 temperature T pso (the temperature below which 80% of the 130 pixels lie) of T s tart = 18.4°C on T en djnit = 32.9°C determined by IR measurement. This results in an ATinit of 14.5°C. Upon reaching the current surface temperature T a kt = 50°C, the energy supply is stopped, the tap water is stirred, for example, and the actual mixing temperature T m ix, meas = 43°C measured manually with a thermocouple.

[0043] With the parameter set assumed for this example a = 35; n = 0.75; m = 2; c = 7; Tmax = 90°C; r = 3.5, the following calculation results for the individual terms of the correction function T korr- 0.2541 °C = 8.89 °C This first term results from the realization that the temperature difference between the surface and the mixture tends to be higher, the higher the temperature rise ATinit. The larger the vessel, the smaller this temperature difference tends to be. Therefore, with a large liquid surface, the temperature difference decreases. The divisor expression (p - r • p 0 ' 5 ) causes the edge pixels, i.e., those pixels that exhibit a temperature mixture between the liquid product on the one hand and the surrounding cooking chamber on the other, to be subtracted. This correction is particularly advantageous at low resolutions and when using a masking method.

[0044] The second term takes into account effects of thermal stratification and convection depending on the temperature rise T that has already occurred ak t-T st type and the starting temperature T start and corrects the first term.

[0045] (3) = 7 • (1 ) °C « 3.11 °C

[0046] This third term partially compensates for the effect of heat conduction depending on the current temperature. If the temperature gradient is higher, more heat is distributed evenly throughout the vessel by heat conduction. The third term therefore decreases in magnitude the higher T a kt will be.

[0047] The correction function then applies to the example as a whole:

[0048] Tcorr = 8.89 °C ■ 0.45 + 3.11 °C = 7.11 °C

[0049] The calculated mixing temperature T m ix now results from

[0050] Tmix = Takt - Tkorr = 50 °C - 7, 11 °C = 42,89 °C, which corresponds very well to the actually measured value T mix, meas = 43 °C. Conveniently, it is not necessary to determine a separate set of parameters a priori for each vessel, each temperature range, each filling quantity, or each object size. One advantage of the method is that with a sufficient number of measured values, i.e., known cycle rate and T m ix, meas, a universal set of parameters a, c, n, m, r, T ma x can be found. For this purpose, for example, the above calculation can be carried out for a sufficient number of heating processes and then, using conventional optimization algorithms (e.g. the so-called “least-square” fit), a set of parameters a, c, n, m, r, T ma x can be found for which the deviations between the calculated estimated mixing temperature Tmix and the actual mixing temperature T m ix,meas: |T m ix - Tmix, meas| can be minimized.

[0051] This parameter set may depend on the equipment of the cooking appliance used (e.g. compact or full-size appliance, pull-out or hanging rack, position of the microwave feed, etc.) and can be generated by the manufacturer for each equipment and stored, for example, in a data memory of the respective microwave appliance.

[0052] In one embodiment, the correction parameters are selected depending on the type of liquid food being cooked. This utilizes the knowledge that the behavior at the liquid surface can change, particularly depending on the salt content of the liquid food. Consequently, it may be useful to provide a separate correction parameter for particularly salty liquids such as soups or sauces. However, the provision of separate correction parameters is not limited to differences in salt content. In a further development, a type of liquid food is fed into the microwave oven, selected on the microwave oven and / or automatically recognized by the microwave oven, and appropriate correction parameters are selected to carry out the method.

[0053] One embodiment allows the correction parameters to be selected depending on the resulting field distribution (“mode pattern”) of the microwave radiation in the cooking chamber. The mode pattern can, for example, be known for certain liquid products or can be determined as a result of the initial scan. A further development allows the microwave treatment to be terminated when the calculated mixing temperature T m ix a given target value T Z iei is reached or exceeded. If a certain target value T Z If desired by a user, only Tmix needs to be calculated continuously or quasi-continuously during the microwave treatment process until T m ix the target value T zie i, is reached or exceeded, after which the process can be terminated.

[0054] It is therefore a particularly easy-to-implement embodiment of a microwave treatment process that

[0055] - the liquid product is placed in a container in the cooking chamber,

[0056] - a target temperature T Zjei for the mixing temperature of the liquid material,

[0057] - the microwave treatment is started,

[0058] - an initial scan is carried out at the beginning of the microwave treatment, from which at least ATinit and p are determined,

[0059] - the correction function T kor r is calculated at least using the measured input variables ATinit and p,

[0060] - the microwave treatment is continued after the initial scan, whereby the current mixing temperature Tmix is ​​determined quasi-continuously by measuring a current surface temperature Takt of the material less the correction function Tkorr (and thus using the associated correction parameters) and

[0061] - the process is terminated when the current calculated mixing temperature Tmix reaches the target temperature T Z iei reaches or exceeds.

[0062] That the current mixing temperature T m ix "quasi-continuously" means in particular that it is re-determined or recalculated at sufficiently short intervals - e.g. every second.

[0063] It is a further development that the correction function Tkorr is additionally calculated using the initial temperature T start, the current surface temperature, the clock pulse, and / or at least one correction parameter, in particular the set of correction parameters described in more detail above. The object is also achieved by a household microwave appliance configured to carry out the method as described above. The household microwave appliance can be designed analogously to the method, and vice versa, and has the same advantages.

[0064] In a further development, the household microwave appliance can have a microwave generating device (e.g. a magnetron or a semiconductor-based microwave generator), an IR cooking chamber camera, etc.

[0065] The household microwave appliance can also be equipped with a data processing device or be connected to it (e.g., via the Internet) via a data processing device that can execute the data processing steps necessary for implementing the method, in particular calculation steps. Furthermore, the household microwave appliance, in particular the data processing device, can have the data memory described above, in which the correction parameters are stored.

[0066] The above-described properties, features and advantages of this invention, as well as the manner in which they are achieved, will become clearer and more clearly understood in connection with the following schematic description of an embodiment, which is explained in more detail in connection with the drawings.

[0067] Fig.1 shows a sectional side view of a sketch of a vessel filled with liquid material;

[0068] Fig.2 shows a sectional side view of a sketch of a microwave oven loaded with the liquid material;

[0069] Fig.3 shows a masking of an image from an IR camera to a pixel belonging to liquid material;

[0070] Fig.4 shows a possible sequence of a microwave treatment process;

[0071] Fig.5 shows a plot of a measured surface temperature without stirring of the liquid material against a measured mixing temperature; and

[0072] Fig. 6 shows a plot of a calculated mixing temperature against a measured mixing temperature for the samples used in Fig. 5. Fig. 1 shows a vessel in the form of, for example, a glass G, which is filled with a liquid material, for example, in the form of water W. Due to treatment or exposure to microwaves, a temperature stratification develops in the material W, in which the layer temperature T is higher the higher the layer is. The material in the uppermost liquid layer (usually < 1 mm) is particularly hot, whereby this determines the temperature or temperature distribution T SU rf, which is measured by an infrared camera mounted above with a view into the glass G.

[0073] Fig. 2 shows a sectional side view of a sketch of a microwave appliance 1 loaded with the liquid product W in the glass G. The microwave appliance 1 has a cooking chamber 2, which can be loaded with the product W and can be closed by means of a microwave-tight cooking chamber door 3. The cooking chamber can be supplied with microwaves and for this purpose has a microwave generation unit 4, which generates the microwaves. The generated microwaves are guided through a microwave guide 5, from which they can be coupled out into the cooking chamber 2. At the coupling point there is a rotating antenna 6, the angle of rotation of which can be specifically adjusted by means of a control device 7. Depending on the angular position, for example, a mode image in the cooking chamber 2 can be influenced. The control device 7 can also be set up to control the microwave generation unit 4. In the area of ​​a ceiling 8 of the cooking chamber 2 there is avertically or - as shown - diagonally downward directed IR camera 9, in whose field of view the glass G is located. The IR camera 9 therefore measures, among other things, the temperature T. SU rf (here referred to simply as T) of the uppermost layer of the material W. The IR camera 9 can, for example, be a digital camera with an image resolution of 24 32 = 768 pixels. The IR camera 9 can be coupled to the control device 7, wherein the control device 7 can also serve as a data processing device to evaluate the pixels or the associated temperatures.

[0074] Fig. 3 shows a masking of an IR image B from the IR camera 9. The pixels not belonging to the liquid material W have been detected and masked out, e.g., by means of the control device 7. The pixels BPM remaining after the masking, whose temperature is evaluated, correspond to those pixels that show a corresponding part of the uppermost layer of the liquid material W. Typically, the number of masked pixels is between 30 and 300 of the total 768 pixels of the IR image B. The mask can be defined, in particular, during an initial scan and remain the same for the subsequent microwave treatment process. It has proven advantageous not to simply average the measured individual temperatures of the pixels BPM to obtain a single surface temperature T, but to use a quantile temperature for this purpose. It has proven particularly advantageous to use a percentile temperature, specifically T p8o with an 80% percentile.

[0075] Fig.4 shows a possible sequence of a microwave treatment process using the microwave device 1 from Fig.2.

[0076] In a step S1, the liquid product W is placed in the container G in the cooking chamber.

[0077] In a step S2, a target value T Z iei is set for a mixing temperature.

[0078] In a step S3 the microwave treatment process is started.

[0079] In step S4 the initial scan is started.

[0080] In step S5, the masked pixels BPM are determined from the initial scan. From the masked pixels BPM, the size p of the surface of the liquid material W can be derived, namely as the area of ​​the pixels BPM. From the temperatures of the masked pixels BPM, their 80th percentile temperatures at the beginning (T s start) and end (T endjnit) of the initial scan and from this the temperature swing ATmit-

[0081] In a step S6, following the initial scan, the microwave treatment is continued and the current p80 surface temperature T a kt determined. From T a kt, the correction function Tkorr is first calculated - e.g. by means of the control device 7 - in particular according to where the correction parameters a, r, n T ma x, m and c can be stored in a data memory of the control device 7. Subsequently, Tmix — Clock — Tcorr can be calculated, e.g. also by the control device 7.

[0082] During the microwave treatment, a step S7 also checks whether the calculated mixing temperature T m ix the desired target value T zieihas been reached or exceeded. If this is not the case ("N"), the process branches back to step S6 and the microwave treatment is continued, updating the calculated mixing temperature T m ix continued.

[0083] However, if this is the case ("Y"), the microwave treatment process is terminated in step S8.

[0084] Fig.5 shows a plot of a measured p80 surface temperature cycle at the time of stopping the microwave energy supply without stirring the liquid material W against the measured mixing temperature T m ix,meas for hot water W and various vessels G, whereby the type of vessels is not differentiated. Stirring and measuring T mix,meas is performed immediately after the microwave energy supply has been terminated in the experiment to minimize measurement errors. Such vessels G include, for example, a large, a medium, and a small coffee cup, a plastic bowl, a lemonade glass, and a laboratory beaker.

[0085] As already described above, the measured mixing temperature T m ix,meas always below the measured surface temperature Takt, with a high spread of the deviation between these two temperatures T m ix,meas and T a kt both for different vessels G and for multiple measurements with the same vessel G and different T a kt. In the example, the average deviation between T mix And Tmix.meas 7 ,7 C.

[0086] Fig.6 shows a plot of a calculated mixing temperature T m ix against the measured mixing temperature T mix,meas for the samples used in Fig.5. The correction parameters for the correction function Tkorr described above were generated from the samples used in Fig.5, where a = 35; n = 0.75; m = 2; c = 7; T ma x = 90°C and r = 3.5. The dashed range of sample deviations between the two temperatures T m ix,meas and T m ix is ​​small (approx. ± 2.5 °C) and is on average 1.4 °C, which is considerably better than the deviation between the two temperatures T shown in Fig.5 m ix,meas and T SU rf.

[0087] Another advantage is that the parameterized correction function provides more accurate results from T m ix can result in a higher value than, for example, a constant offset, which can also be used in principle. The limiting case T kor r = const, can be written with a = 0; n = 0; m = 0; c = const; T ma x = °° OC and r = 1. The average deviation of 7.7°C, which results from Fig. 5, results in Tcorr = 7.7°C. This also improves the average deviation, but only to 3.5°C (not shown).

[0088] The use of the above correction function Tcorr can also be applied with good accuracy to vessels that are not included in the original data set / population from which the correction parameters were calculated. This is even more successful the more diverse the test vessels in the population are, using which the correction parameters are fitted. With a large and diverse population, a particularly robust set of correction parameters can be achieved, which ensures a particularly high accuracy in the calculation of T even for new vessels not examined in the original data set. m ix enables.

[0089] Of course, the present invention is not limited to the embodiment shown.

[0090] In general, "a", "an", etc., can be understood as a singular or a plural, in particular in the sense of "at least one" or "one or more", etc., unless this is explicitly excluded, e.g. by the expression "exactly one", etc.

[0091] A numerical specification may also include the exact number specified as well as a usual tolerance range, as long as this is not explicitly excluded.

[0092] 1 microwave oven

[0093] 2 cooking chamber

[0094] 3 Cooking chamber door

[0095] 4 Microwave generation unit

[0096] 5 Microwave guide

[0097] 6 Rotating antenna

[0098] 7 Control device

[0099] 8 Ceiling of the cooking chamber

[0100] 9 IR camera

[0101] B IR image

[0102] BPM Masked pixels

[0103] G Vessel p Size of the surface of the liquid material

[0104] S1-S8 process steps

[0105] Clock Current surface temperature

[0106] Tendjnit surface temperature at the end of an initial scan

[0107] Tkorr correction function

[0108] Tmix Calculated mixing temperature

[0109] Tmix Measured mixing temperature

[0110] T, Tsurf surface temperature of the liquid material

[0111] Tstart Surface temperature at the start of a microwave treatment process

[0112] Tztei Target value of the mixing temperature

[0113] W Liquid goods

Claims

Patent claims 1. Method (S1 - S8) for determining a temperature of a liquid material (W) during a microwave treatment (S3 - S8) in a cooking chamber (2) of a household microwave appliance (1), in which a mixed temperature (Tmix) of the liquid material (W) is calculated from at least one measured value (Tstart, Tendjnit, ATinit, Takt, p) of the liquid material (W), of a vessel (G) receiving the liquid material (W) and / or of the cooking chamber (2).

2. Method (S1 - S8) according to claim 1, wherein the at least one measured value (Tstart, Tendjnit, ATinit, Takt, p) of the liquid material (W) and / or the vessel (G) comprises at least one measured value from the group - Surface temperature (Tstart, Tendjnit, ATM, Takt), - Ultrasonic properties, - surface area (p) and / or volume.

3. Method (S1 - S8) according to one of the preceding claims, wherein the at least one measured value of the cooking chamber (2) comprises at least one measured value from the group - Cooking chamber temperature, - humidity, - oxygen content.

4. Method (S1 - S8) according to one of claims 2 to 3, wherein the mixing temperature (Tmix) of the liquid material (W) is determined by measuring at least one surface temperature (Tstart, T etl djnit, ATinit, T a kt) of the liquid material (W) is determined and by means of a correction function (Tk Orr ) is corrected, whereby the correction function (Tk Orr ) is a function of at least one other of the measured values ​​(p).

5. Method (S1 - S8) according to claim 4, wherein the correction function (Tk Orr ) as input variables at least the measured variables - Initial temperature (Tstart) of the liquid material (W), - temperature increase measured during an initial period (AT in it) of the liquid goods (W), - current temperature (T akt ) of the liquid goods (W) and / or - Size value (p) of the liquid good.

6. The method (S1 - S8) according to claim 5, wherein the initial time period is the duration of an initial scan (S4).

7. Method (S1 - S8) according to one of claims 5 to 6, wherein the input variables (Tstart, ATinit, T a kt, p) are measured by means of an IR camera (9) with pixel-like resolution.

8. The method (S1 - S8) according to claim 7, wherein at least one of the temperatures (Tstart, ATinit, T a kt) is determined using a quantile temperature, in particular a percentile temperature, of a temperature distribution comprising several pixels (BPM).

9. Method (S1 - S8) according to one of claims 5 to 8, wherein the correction function (Tkorr) is determined according to with a, r, n, m, c and T ma x given correction parameters.

10. Method (S1 - S8) according to claim 9, wherein the correction parameters are selected depending on the type of liquid food (W).

11. Method (S1 - S8) according to one of claims 9 to 10, wherein the correction parameters are selected depending on an established field distribution of the microwave radiation in the cooking chamber (2).

12. Method (S1 - S8) according to one of claims 5 to 11, in which - the liquid product (W) is placed in a container (G) in the cooking chamber (2) (S1), - a target temperature (T zie i) for the mixing temperature (T m ix) of the liquid goods (W) is specified (S2), - the microwave treatment is started (S3), - at the beginning of the microwave treatment an initial scan is carried out (S4 - S5), from which at least the temperature increase (ATinit) measured during an initial period of time and the size value (p) are determined (S5), - the correction function (Tkorr) is calculated at least using the measured input variables (Tstart, ATinit, Takt, p), - the microwave treatment is continued after the initial scan (S6), whereby the current mixing temperature (Tmix) is determined quasi-continuously by measuring a current surface temperature (Takt) of the liquid material (W) less the correction function (Tkorr) (S6) and - the process is terminated (S8) when the current calculated mixing temperature (Tmix) exceeds the target temperature (T zie i) reaches or exceeds (S7).

13. A household microwave appliance (1) which is designed to carry out the method (S1 - S8) according to one of the preceding claims.

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