OPERATING A HOUSEHOLD MICROWAVE APPLIANCE

Abstract

A household microwave appliance operates with multiple parameter configurations to treat food to be cooked in a locally differing manner. The microwave appliance determines in an initial scan with a thermal imaging sensor directed into the cooking chamber a temperature distributions on a surface of the food to be cooked. Change patterns are obtained from differences between different temperature distributions. An evaluation value is calculated for a best heating pattern that brings the current temperature distribution closest to a target temperature distribution determined based on a normalized target state and a current temperature distribution, whereafter microwave power is applied to the food to be cooked with the parameter configuration associated with the best heating pattern.

Claims

1-12. (canceled)

13. A method for operating a household microwave appliance, said method comprising: loading a cooking compartment with food to be cooked; performing an initial scan by supplying microwaves into the cooking compartment using at least two different parameter configurations set in a control apparatus, with the food treatable differently in a localized manner using the microwaves having the at least two different parameter configurations, measuring with a thermal imaging sensor temperature distributions associated with the at least two different parameter configurations on a surface of the food, and determining heating patterns from differences of the temperature distributions, and following the initial scan (a) setting at least one target temperature distribution for the food, based on a standardized target state and a prevailing temperature distribution; (b) determining, based on the prevailing temperature distribution, a most suitable heating pattern for achieving the at least one target temperature distribution; (c) applying to the food microwaves having a sequence of the at least two different parameter configurations associated with the most suitable heating pattern; and (d) determining as a new prevailing temperature distribution the previously prevailing temperature distribution in addition to the most suitable heating pattern.

14. The method of claim 13, further comprising repeating steps (a) to (d) until the prevailing temperature distribution meets a predetermined cancellation criterion.

15. The method of claim 14, wherein the predetermined cancellation criterion comprises that the prevailing temperature distribution reaches or exceeds a predetermined limit temperature calculated from a quantity of energy that is required to perform a phase transformation in the food.

16. The method of claim 15, wherein the phase transformation is performed of water.

17. The method of claim 14, further comprising measuring, in addition to steps (a) to (d), with the thermal imaging sensor the temperature distribution of the food, wherein the cancellation criterion comprises that the measured temperature distribution reaches or exceeds a predetermined limit temperature.

18. The method of claim 13, further comprising prior to performing the initial scan, performing a tuning phase of the microwave generator by measuring a heating pattern as a difference between a temperature distribution at a beginning of the tuning phase and a temperature distribution at an end of the tuning phase; determining from the heating pattern a segment having a highest local temperature increase; determining from the segment a maximum duration of an initial phase until water in the food reaches a phase transition; and thereafter setting a duration of the initial phase such as not to exceed the maximum duration.

19. The method of claim 13, wherein in step (a), the at least one target temperature distribution <T.sub.target> is calculated in accordance with
<T.sub.target>=T.Math.<Z>, wherein T is an average temperature of the prevailing temperature distribution averaged over associated segments and <Z> is the standardized target state, and wherein in step (b), the most suitable heating pattern is determined by calculating for each selected heating pattern an evaluating value B.sub.p,q in accordance with
B.sub.p,q=(|<T.sub.target><T>|.sup.d|<T.sub.target>(<T>+<T>.sub.p,q)|.sup.d) wherein <T> is the prevailing temperature distribution, <T>.sub.p,q are the heating patterns determined from the differences of the temperature distributions, and by selecting as the most suitable heating pattern the heating pattern with the highest evaluating value B.sub.p,q.

20. The method of claim 13, comprising in step (a), calculating a first target temperature distribution <T.sub.target> in accordance with
<T.sub.target>T=.Math.<Z>, wherein T is an average temperature from the prevailing temperature distribution averaged over the associated segments and <Z> is the standardized target state, and calculating for all selected heating patterns a respective second target temperature distribution <T.sub.target*>.sub.p,q in accordance with
<T.sub.target*>.sub.p,q=T.sub.p,q.Math.<Z>, wherein T.sub.p,q is the average temperature from the prevailing temperature distribution plus the selected heating pattern averaged over the associated segments, and in step (b), determining the most suitable heating pattern, calculating for each selected heating pattern an evaluating value B.sub.p,q in accordance with and selecting as the most suitable heating pattern the heating pattern having the highest evaluating value B.sub.p,q.

21. The method of claim 13, wherein the at least one setting parameter comprises at least one setting parameter selected from the group consisting of angle of rotation of a rotary antenna, angle of rotation of a rotary plate, position of a mode stirrer, microwave frequency of a semiconductor-based microwave generator, and phase difference between microwaves that are supplied into the cooking compartment from different feed-in locations or ports.

22. The method of claim 13, wherein the food that is introduced into the cooking compartment is frozen food.

23. The method of claim 13, wherein the food that is introduced into the cooking compartment is food that is not frozen.

24. The method of claim 13, further comprising: performing a further initial scan after multiple repetitions of steps (a) to (d), and subsequently repeating steps (a) to (d) based on the further performed initial scan.

25. A household microwave appliance, comprising: a cooking compartment configured to be loaded with food; a microwave generator generating microwaves to which the food and located in the cooking compartment is exposed; a thermal imaging sensor oriented into the cooking compartment and configured to determine temperature distributions on a surface of the food to be cooked; and a control apparatus configured to set multiple parameter configurations of setting parameters of the household microwave appliance, with at least two parameter configurations treating the food to be cooked differently with the microwaves in a localized manner, wherein the household microwave appliance is configured to implement a method as set forth in claim 16.

Description

[0113] The above-described characteristics, features and advantages of this invention and also the manner in which these are achieved become clearer and more clearly understandable in conjunction with the following schematic description of an exemplary embodiment that is further explained in conjunction with the drawings.

[0114] FIG. 1 shows a simplified sketch of a household microwave appliance that is configured so as to implement the method that is described above;

[0115] FIG. 2 shows various sequential steps of a possible exemplary embodiment of the method that is described above and

[0116] FIG. 3 shows a temporal progression of an average surface temperature of food to be cooked during a defrosting procedure during constant influencing using microwave power.

[0117] FIG. 1 illustrates as a sectional view in a side view a sketch of a household microwave appliance in the form of a microwave appliance 1 that is configured so as to implement the method that is further described in FIG. 2. The microwave appliance 1 has a cooking compartment 2 having a front-side loading hatch 3 that can be closed by means of a door 4. Food to be cooked G is arranged on a carrier 5 for food to be cooked in the cooking compartment 2.

[0118] The household microwave appliance 1 moreover has at least one treatment unit for food to be cooked in the form of a microwave generating facility 6. The microwave generating facility 6 can have for example an inverter-controlled microwave generator, a rotary antenna 7, which can be adjusted in rotation and/or height, and/or a wobbler (not illustrated), which can be adjusted in rotation and/or height. In addition, the microwave appliance 1 can have infrared radiating heating bodies (not illustrated), for example a bottom heat heating body, a top heat heating body and/or a grill heating body.

[0119] The microwave generating facility 6 is controlled by means of a control unit 8. In particular, the microwave generating facility 6 can be set to at least two parameter configurations S.sub.p, S.sub.q having different field distributions in the cooking compartment 2. Different parameter configurations S.sub.p, S.sub.q can correspond for example to different values .sub.i of an angle of rotation of the rotary antenna 7. The angle of rotation consequently corresponds to a field-varied setting parameter or operating parameter of the microwave appliance 1 having at least two setting values (i. In particular, the rotary antenna 7 can rotate continuously, for example in increments =1 with the result that n=360 angle of rotation values (i can be set, in particular individually.

[0120] The control unit 8 is moreover connected to an optical sensor in the form of a thermal imaging camera 9. The thermal imaging camera 9 is arranged so that it is oriented into the cooking compartment 2 and can record a pixelated thermal image of the food to be cooked G. As a consequence, the thermal imaging camera 9 can be used so as to record or determine a temperature distribution <T> on the surface of the food to be cooked G.

[0121] The control unit 8 can moreover be configured so as to implement the method that is described above and also so as to be used as an evaluating facility. Alternatively, the evaluation can run on an instance that is external to the appliance such as a network computer or the so-called cloud (not illustrated).

[0122] FIG. 2 illustrates various sequential steps of a possible exemplary embodiment of the method that is described above with the aid of the microwave appliance 1 in FIG. 1.

[0123] In one step S0, food to be cooked G is introduced into the cooking compartment 2 for treatment using microwaves. The food to be cooked G can be frozen or not frozen.

[0124] In step S1, a microwave treatment procedure is started for which the microwave generator 6 is activated. For this purpose, initially a tuning phase of the microwave generator 6 is waited for, for example for t.sub.es=10 s, in order to bring this microwave generator into a tuned or stable operating state. During the tuning phase, the rotary antenna 7 rotates continuously or quasi-continuously, for example with increments =1.

[0125] At the start of the tuning phase, an image of a heat distribution <T>.sub.begin of the surface of the food to be cooked G is captured by means of the thermal imaging camera 9, with the conclusion of the activation phase an image of a heat distribution <T>.sub.end of the surface of the food to be cooked G is captured. The heat distributions <T>.sub.begin and <T>.sub.end in each case have m surface segments, for example m pixels or m averaged groups of adjacent pixels.

[0126] In step S1, a heating pattern <T>.sub.es is subsequently calculated as the difference of the m surface segments in accordance with <T>.sub.es=<T>.sub.end<T>.sub.begin and the segment T>.sub.es;max having the maximum rise in temperature is ascertained therefrom. If the food to be cooked G is frozen for example at 24 C. and is to be defrosted, the heat distributions and <T>.sub.begin and <T>.sub.end in the four segments can appear for example as follows (temperature values in C.)

##STR00005##

and thus T.sub.es;max=5 C.

[0127] Subsequently, in order to determine a maximum possible duration t.sub.init,max for the following initial scan it is assumed that the initial scan is to be performed at most until a surface region of the food to be cooked G reaches the freezing point of water, minus a safety temperature interval of for example 2 C., in other words does not exceed 2 C. As a consequence, it is ensured that the initial scan is only performed during the warming up phase of the food to be cooked G and while the food to be cooked G is not yet in its saturation state, in other words is not yet locally in its phase transition state or saturation state anywhere.

[0128] Based on the maximum rise in temperature T.sub.es;max=5 C., the maximum possible duration t.sub.init;max of the initial scan is determined as

[00008]$t_{\mathrm{init};\max }=\frac{\left(-2C.-\left(-19C.\right)\right).Math.t_{\mathrm{es}}}{T_{\mathrm{es},\max }}=\frac{17C..Math.10s}{5C.}=34s$

[0129] For the initial scan, a time period t.sub.init of 34 s can be set whereby a particularly effective resolution/low thermal noise of the heat distributions that are then captured by means of the thermal imaging camera 9 are provided.

[0130] It is however also possible that smaller durations t.sub.init than 34 s already suffice in order to obtain an effective resolution/a low thermal noise, for example between 5 s and 10 s, and the duration t.sub.init for implementing the initial scan is set to such a lower duration.

[0131] For the example explanation of the method sequence, it is to be assumed below that the duration of the initial scan is set to t.sub.init=10 s.

[0132] In step S2, an exemplary initial scan is performed in that microwaves having a constant power are supplied into the cooking compartment 2 for t.sub.init=10 s in the case of a continuously or quasi-continuously (for example with an increment =1) rotating rotary antenna 7. The rotary antenna 7 in this case advantageously performs at least one full rotation between =0 and =360, however can also be rotated further.

[0133] The thermal imaging camera 9 during or after each angle of rotation that is set or during or after each angular sector (for example for all =10) captures an image of a heat distribution of the food to be cooked G having in each case m segments. Under the exemplary assumption that only the angle of rotation is varied as a setting parameter, for example for the full rotation of the rotary antenna 7 the parameter configurations S.sub.0=0, S.sub.1=1, . . . , S.sub.359=359 result.

[0134] The corresponding temperature distributions <T>(S.sub.i)<T>(.sub.i)<T>.sub.i can appear for example as follows (with <T>.sub.0=<T>.sub.end and values in C.):

##STR00006##

etc. wherein the rises in temperature starting from <T>.sub.0 become greater the further the rotary antenna 7 rotates. In this case, it is to be noted that the temperature distributions <T>.sub.i at different angles of rotation (i locally do not generally change uniformly since the associated field distributions of the microwaves in the cooking compartment 2 are not uniform but rather for example hot spots stated above can form in dependence upon the angle of rotation.

[0135] In step S2, moreover corresponding distributions of temperature changes or rises in temperature (heating patterns)<T>.sub.p,q that result in the case of an antenna rotation between a parameter configuration S.sub.p and a parameter configuration S.sub.q (here: between different angles of rotation .sub.p and .sub.q) can be calculated from the temperature distributions, in the present example for example

##STR00007##

[0136] etc., wherein <T>.sub.p,q is calculated in accordance with <T>.sub.p,q=<T.sub.q><T.sub.p>.

[0137] The further apart S.sub.p and S.sub.q or p and q are from one another, the higher in general the associated rise in temperature of the segments. In the above examples, it is therefore assumed in a simplified manner that the rises in temperature between two angles .sub.i and .sub.i+1 are practically negligible with the result that for example <T>.sub.0.89 for practical considerations can be represented by <T>.sub.0.89 etc.

[0138] In general, heating patterns <T>.sub.p,q can be calculated using arbitrary values p and q. It is possible for example to calculate heating patterns <T>.sub.p,q for all the possible pairs of S.sub.p and S.sub.q or p and q or it is possible to calculate heating patterns <T>.sub.p,q only for selected pairs of S.sub.p and S.sub.q or p and q, for example having a specific interval and namely also overlapping, for example <T>.sub.0,29<T>.sub.10,39, <T>.sub.20,49, . . . , etc., <T>.sub.0,59, <T>.sub.10,69, <T>.sub.20,79, . . . , etc.

[0139] The initial scan is thus concluded. The prevailing temperature distribution of the food to be cooked G at the end of the initial scan, in the above example if the rotary antenna 7 has only been rotated to =3600 (in other words has only performed precisely one full antenna rotation), corresponds to the temperature distribution <T.sub.360>.

[0140] In a step S3, the desired standardized target distribution <Z> is set, for defrosting in the above example for example a (here to a standardized) homogenous target distribution <Z> with

##STR00008##

[0141] wherein <Z> in generalfor example for a cooking procedure in lieu of a defrosting procedurecan also be inhomogeneous.

[0142] In a step S4, it is determined which heating pattern <T>.sub.p,q that is determined by means of the initial scan must be added to the prevailing temperature distribution <T> in order to obtain a best approximation of the desired standardized target distribution <Z>. Below, two variants are described for how the most suitable heating patterns <T>.sub.p,q|best can be determined:

[0143] 1.sup.st Variant

[0144] The average T of the segments of the prevailing temperature distribution <T> is formed, in the above example after the initial scan T=(13 C.13 C.14 C.12 C.)/4=13 C. and the non-standardized target temperature distribution <T.sub.target> that is used for the prevailing iteration step is determined therefrom in accordance with

##STR00009##

[0145] Evaluating values B.sub.p,q are subsequently calculated for all or only selected heating patterns <T>.sub.p,q and the evaluating values for this purpose represent a measure for how good or suitable the associated heating pattern <T>.sub.p,q is based on the prevailing temperature distribution <T> for achieving the non-standardized target temperature distribution <T.sub.target>.

[0146] The evaluating values B.sub.p,q can be calculated for example in accordance with the formula

B.sub.p,q=(|<T.sub.target><T>|.sup.d|<T.sub.target>(<T>+<T>.sub.p,q)|.sup.d)

[0147] The above formula can be written in segment-related representation as

[00009]$B_{p,q}=\underset{j=1}{\overset{m}{.Math.}}\left({.Math.T_{\mathrm{target};j}-T_j.Math.}^d-{.Math.T_{\mathrm{target};j}-\left(T_j+T_{p,q;j}\right).Math.}^d\right)$

[0148] using m the number of the segments. In this case, the greater the value of B.sub.p,q the better the target temperature distribution <T.sub.target> is approximated.

[0149] The value of the exponent d is a preset value that determines how much deviations from the target temperature distribution <T.sub.target> are taken into consideration. For d>1 it follows that the evaluating value B.sub.p,q prefers such heating patterns <T>.sub.p,q that compensate for the large differences of the prevailing temperature distribution <T> to the target distribution <T.sub.target>. The most suitable evaluating value B.sub.p,q|best then corresponds in other words to the largest calculated evaluating value B.sub.p,q and the most suitable heating pattern <T>.sub.p,q|best is the heating pattern that is associated with the evaluating value B.sub.p,q|best.

[0150] 2. Variant

[0151] In addition to the target temperature distribution <T.sub.target> that is also calculated in the first variant, for each selected heating pattern <T>.sub.p,q a further target temperature distribution <T.sub.target*>.sub.p,q=T.sub.p,q.Math.<Z> is formed, wherein T.sub.p,q is calculated from the prevailing temperature distribution <T> plus the selected heating pattern <T>.sub.p,q averaged over the associated segments.

[0152] An evaluating value B.sub.p,q is subsequently calculated for each selected heating pattern <T>.sub.p,q in accordance with

B.sub.p,q=(|<T.sub.target>.sub.p,q<T>|.sup.d|<T.sub.target*>(<T>+<T>.sub.p,q)|.sup.d)

[0153] and the heating pattern <T>.sub.p,q for which the evaluating value B.sub.p,q assumes the highest value B.sub.p,q|best is selected as the most suitable heating pattern <T>.sub.p,q|best.

[0154] As already indicated above, the exponent value d can be set independent of segment or can be varied in dependence upon the segment (for example in accordance with d=d1 or d=d2). Optionally, step S4 can be calculated using a segment-dependent exponent value d with every nth pass, otherwise using an exponent value d that is independent of segment.

[0155] In a subsequent step S5, for the two variants the prevailing temperature distribution <T> is increased by the most suitable heating pattern <T>.sub.p,q|best in other words written iteratively in accordance with

<T>:=<T>+<T>.sub.p,q|best,

[0156] and the thus increased temperature distribution represents the new prevailing temperature distribution <T>. The new prevailing temperature distribution <T> is a virtual temperature distribution that has been determined in a purely computational manner and does not need to match the actual temperature distribution.

[0157] Prior to or after the computerized determination of the new prevailing temperature distribution <T>, in step S5 the food to be cooked G or the cooking compartment 2 is influenced using microwaves under the succession or sequence of parameter configurations S.sub.p, . . . , S.sub.q using microwaves, which corresponds to the most suitable heating pattern <T>.sub.p,q| best.

[0158] In a step S6, a check is performed as to whether the (new) prevailing temperature distribution <T> reaches or exceeds a predetermined limit temperature T.sub.limit. This can include checking whether a segment, some segments (for example more than 50% of the segments) or all the segments of the prevailing temperature distribution <T> reach or exceed the predetermined limit temperature T.sub.limit. If this is not the case, (N), the method branches to step S4. However, if this is the case (J), the microwave treatment procedure is terminated in step S7.

[0159] Optionally, for the case that the prevailing temperature distribution <T> has not yet reached or exceeded the predetermined limit temperature T.sub.limit, following step S5 in a step S8 it is possible for the food to be cooked G to not be influenced using microwave energy for a specific period of time (holding period t.sub.wait) until the next setting of a heating pattern in order to render possible an advantageous thermal compensation due to heat conduction within the food to be cooked. It is likewise possible to pass through multiple step sequences S4 and S5 one after the other and only then in step S8 to wait for the holding period t.sub.wait. In particular, in the case of the use of a magnetron, this can be preserved by the avoidance of many starts.

[0160] Optionally, for the case that the prevailing temperature distribution <T> has not yet reached or exceeded the predetermined limit temperature T.sub.limit, step S6 or step S8 (if provided) is followed by a query as to whether a new initial scan is to be performed. If this is not the case, (No) the method proceeds to step S4.

[0161] However, if this is the case (Yes), the method branches to step S2, and heating patterns <T>.sub.p,q are again recorded. The method subsequently proceeds to step S3, wherein then the previously used standardized target distribution <Z> can be further used or a new standardized target distribution <Z> can be selected.

[0162] FIG. 3 illustrates as a plotting of an average surface temperature T in [ C.] against a microwave treatment duration t in [s] a temporal progression of the average surface temperature T of a 500 g block of minced meat during a defrosting procedure while being influenced using constant microwave power.

[0163] Starting here as an example from an initial average temperature T of 17 C., which is present for example after the tuning phase, during the subsequent microwave influencing under for example continuous rotation of the rotary antenna 7 the average temperature T during a warming up phase W increases in an approximately linear manner. During transition into the saturation phase S (here at T=5 C. or t=approximately 50 s) the progression or the curve bends. In the saturation phase, the microwave power that is absorbed by the food to be cooked can no longer be represented in a linear manner to an increase of the average temperature T.

[0164] Obviously, the present invention is not limited to the illustrated exemplary embodiment.

[0165] In general, a, an, one etc. can be understood to mean singular or plural, in particular in the sense of at least one or one or multiple etc. as long as this is not explicitly ruled out, for example by the expression precisely one etc.

[0166] A numerical disclosure can also include precisely the number that is disclosed as well as a typical tolerance range as long as this is not explicitly ruled out.

LIST OF REFERENCE CHARACTERS

[0167] 1 Household microwave appliance [0168] 2 Cooking compartment [0169] 3 Loading hatch [0170] 4 Door [0171] 5 Carrier for food to be cooked [0172] 6 Microwave generating facility [0173] 7 Rotary antenna [0174] 8 Control unit [0175] 9 Thermal imaging camera [0176] B.sub.p,q Evaluating value [0177] B.sub.p,q|best Most suitable evaluating value [0178] G Food to be cooked [0179] S Saturation phase [0180] S0-S9 Method steps [0181] <T> Temperature distribution on the surface of the food to be cooked G [0182] <T>.sub.begin Temperature distribution at the beginning of a tuning phase [0183] <T>.sub.end Temperature distribution at the end of a tuning phase [0184] <T>.sub.p,q Heating pattern [0185] <T>.sub.p,q|best Most suitable heating pattern [0186] T.sub.es;max Maximum rise in temperature during the tuning phase [0187] T.sub.limit Limit temperature [0188] t Time [0189] t.sub.init Set duration of the initial scan [0190] t.sub.init; max Maximum possible duration of the initial scan [0191] t.sub.wait Holding period [0192] T Average temperature [0193] W Warming up phase [0194] <Z> Standardized target state