Operating microwave household appliances according to microwave generator temperature

Abstract

In a method for operating a microwave household appliance (1), a microwave processing operation is controlled as a function of a temperature (Tm) of a microwave generator (5). The microwave household appliance (1) comprises a cooking chamber (2), a microwave generator (5), a temperature determination device (9) for determining the temperature (Tm) of the microwave generator (5), at least one microwave distribution device (7, 8) and a control device (10), wherein the control device (10) is configured to carry out the method. The invention can be used in particular advantageously for a stand-alone microwave appliance or a combined appliance with a microwave function (oven, in particular a baking oven), or a microwave appliance with an additional radiator.

Description

Technical Field

[0001] The invention relates to a method for operating a microwave household appliance as a function of the temperature of a microwave generator. The invention also relates to a microwave household appliance having a cooking chamber, a microwave generator, a temperature determination device for determining the temperature of the microwave generator, at least one microwave distribution device and a control device, wherein the control device is configured to carry out the method according to any of the preceding claims. The invention can be used in particular advantageously for stand-alone microwave appliances or combined appliances with microwave functionality (furnaces, in particular ovens), or microwave appliances with additional heat radiators. Background Art

[0002] It is known to measure the magnetron temperature in order to detect idling of the cooking appliance or a fault in the magnetron cooling and to avoid the resulting overheating of the magnetron. When a predetermined temperature threshold is reached, the magnetron is switched off.

[0003] GB 2321764 A discloses a temperature sensor which is fixed to a support made of a heat-conducting material and which can be removably mounted on the cooling ribs of a magnetron of a microwave oven in order to measure the temperature of the anode block which is representative of the magnetron. If this temperature rises to an excessively high value and this indicates an abnormal condition, such as lack of load (idling) or a cooling fault, the power supply to the magnetron is interrupted.

[0004] EP 2 993 961 A1 describes idling detection, which is also based on measuring the magnetron temperature. Idling is detected by the slope of the temperature curve or reaching a maximum temperature, and as a result, the power is reduced or completely switched off. EP 2 378 204 A1 and EP 1 594 345 A1 also involve measuring the magnetron temperature to prevent idling of the cooking appliance.

[0005] DE 10 2016 117 922 A1 discloses a method for operating a magnetron with a cathode of a cooking appliance. The power input, in particular the high voltage supply, of the magnetron is controlled or regulated according to a safe state. In addition, a microwave source and a cooking appliance are described.

[0006] DE 10 2004 015 993 A1 discloses a microwave appliance or a combined appliance with microwave operation. Such an appliance comprises: a) at least one cooking chamber for cooking objects; b) at least one device for generating microwaves; c) one or more temperature sensors, in particular for detecting the temperature of the cooking chamber and / or for detecting the temperature of the device for generating microwaves, wherein each temperature sensor generates a measurement signal; and d) at least one evaluation device, with which the charge state of the cooking chamber, in particular the idle operation of the microwave appliance, can be determined by means of the time evolution of the measurement signal of at least one temperature sensor during microwave operation. In addition, a method for operating a microwave appliance is described, in which the time evolution of the measurement signal of at least one temperature sensor is used during microwave operation to determine the charge state of the cooking chamber, in particular the idle operation of the microwave appliance.

[0007] EP 2 194 758 B1 discloses a state detection device for detecting the operating state of a high-frequency heating device, the high-frequency heating device having a magnetron for generating microwaves, wherein the state detection device comprises: a section for determining a movement position, with which the movement position of a radio wave stirring element is determined, the radio wave stirring element works periodically so as to stir the microwaves generated by the magnetron relative to a heated object; an anode current input section, with which the detected anode current of the magnetron is input; and a determination section, with which the period of the periodic movement of the radio wave stirring element is determined with the help of information on the movement position determined by the section for determining the movement position, and then a corresponding value corresponding to the anode current input through the anode current input section is read a plurality of times during the one period and the operating state of the high-frequency heating device is determined based on the plurality of corresponding values ​​during the one period. Summary of the invention

[0008] The object of the present invention is to at least partially overcome the disadvantages of the prior art and in particular to provide better possibilities for operating a microwave domestic appliance as a function of the temperature of the microwave generator.

[0009] This object is achieved according to the features of the independent claims. Advantageous embodiments are the subject matter of the dependent claims, the description and the drawings.

[0010] This object is achieved by a method for operating a microwave domestic appliance, in which method the microwave processing operation is controlled as a function of the temperature of a microwave generator.

[0011] The advantage of this method is that, in contrast to the prior art, the temperature of the microwave generator is now used to control the microwave treatment operation itself, for example in order to obtain an improved cooking result, reduce the treatment time and / or achieve energy savings. In other words, the method does not allow for the identification of critical states for the operation of the microwave generator, such as idling or cooling failure, with the aid of the temperature of the microwave generator, in order to then be able to take countermeasures. Rather, the method allows for the improved control of a microwave treatment operation of an object that is carried out in a prescribed manner (not affected by critical states of the microwave generator). In the microwave treatment operation that is carried out in a prescribed manner, the object or the load that absorbs the microwaves is located in the cooking chamber. Another advantage is that this control can be implemented with technically simple and inexpensive components.

[0012] This method utilizes the fact that when microwaves are coupled into the cooking chamber, a certain portion of the microwaves is reflected back to the microwave generator again and thus causes an increase in the temperature of the microwave generator. The greater the power of the microwaves reflected back, the greater the temperature increase is typically. During typical microwave processing operation, the field distribution in the cooking chamber is often changed in a targeted manner to avoid static hot spots. It is also known that the microwave processing operation is controlled in such a way that a particularly high microwave absorption / a very small reflection to the microwave generator occurs in the cooking chamber in order to obtain high efficiency. By determining the temperature at the microwave generator (e.g. measured as an absolute temperature, temperature increase, etc.), the reflected microwave power for one or more field distributions can currently be at least roughly inferred. This can in turn be used to specifically adjust the field distribution, which has properties, in particular absorption / reflection proportions, that are beneficial to the purpose of the object currently being processed in the cooking chamber. For example, unfavorable field distributions or associated operating parameters can be identified for the energy introduction into the object and eliminated for the further change trend of the microwave processing process.

[0013] A further advantage of the method is that the temperature of the microwave generator enables rapid temporal control of the microwave treatment operation.

[0014] The microwave household appliance can be an independent microwave appliance or a combined appliance with a microwave function, such as an oven, in particular a baking oven, or a microwave appliance with an additional heat radiator such as a resistive heating body.

[0015] The microwave generator may be a magnetron or a semiconductor-based microwave generator. The microwave generator may be an inverter-controlled microwave generator. In an extended design, the microwave generator may have a plurality of feed points for feeding or coupling microwaves into the cooking chamber. The microwaves fed in at different feed points may have a phase difference or phase shift between each other. In an extended design, this phase shift may be specifically adjusted by the device.

[0016] It is also possible that the microwave household appliance has a plurality of microwave generators, which have different feed points for feeding or coupling microwaves into the cooking chamber. The microwaves fed in at the different feed points can in particular have a phase shift with respect to one another. In an extended design, this phase shift can be specifically adjusted by the appliance.

[0017] Microwave processing operation refers in particular to an operating procedure of a microwave household appliance, in which an object is processed by being exposed to microwaves, for example for cooking, boiling, thawing, etc. The object may be a cooking material such as food, water, or the like.

[0018] Control based on the temperature of the microwave generator includes, in particular, a change in the microwave application to the process material by a normal or prescribed change in the setting parameters provided for the microwave process operation. A change in the microwave application due to emergency measures is not covered by the present method in particular. However, it is not excluded that a reduction in the power of the microwave generator is also provided when a critical temperature threshold is reached.

[0019] Controlling the microwave treatment operation according to the temperature of the microwave generator may include control according to absolute temperature, temperature difference and / or temperature change, etc.

[0020] The temperature of the microwave generator can be measured, for example, by at least one temperature sensor or derived from other measured values. The temperature of the microwave generator can be measured directly at the microwave generator or indirectly at another location. The temperature sensor can be fixed, for example, between cooling strips, directly at the anode block of the microwave generator. Fixing directly at the anode block of the magnetron is particularly advantageous, since there is a minimum thermal inertia of the system at this location. Changes in the microwave loading and the resulting changes in the reflection conditions can therefore be measured with particularly high temperature strokes and particularly small time delays.

[0021] One example of an indirect measurement includes measuring the air temperature after the cooling air has passed through the microwave generator, for example the air outlet temperature of the appliance. Another example of an indirect measurement of the temperature of the microwave generator includes measuring or determining the temperature difference between the air inlet and the air outlet in order to advantageously mitigate the variable preheating effects of upstream components.

[0022] It is also conceivable to determine the temperature of the microwave generator indirectly via operating parameters of the associated inverter (ie, the high-voltage switching network part for driving the microwave generator), since the heating current, the anode current and the anode voltage are dependent on the temperature of the microwave generator.

[0023] One design is that during the microwave processing operation, the field distribution in the cooking chamber of the microwave household appliance changes and the microwave processing operation is controlled according to the temperature change of the microwave generator caused by the change in the field distribution. The advantage achieved by this is that the characteristics of a specific field distribution can be identified when transitioning or changing between different field distributions by means of temperature changes, and a specific field distribution that is beneficial to achieving a specific purpose or scenario can then be selected or adjusted for the microwave processing operation. The change in the field distribution is achieved in a targeted manner by changing at least one operating parameter of the microwave household appliance. The field distribution can also be called a "mode image".

[0024] Another advantage is that the temperature change at the microwave generator occurs relatively quickly after the change in the field distribution or occurs with only a slight time delay. In contrast, the previous effects of the change in the field distribution can be determined solely from the temperature change of the cooked product, for example with the aid of a baking thermometer or infrared images. However, the temperature change of the cooked product can only be detected with a considerable delay, since the cooked product has a high thermal inertia. In contrast, with the present method, reliable measurement results can be achieved after only a few seconds.

[0025] One further development is to change the field distribution while keeping the output power of the microwave generator constant. This has the advantage that the influence of the change in the field distribution or the pattern image can be particularly clearly recognized. However, it is also possible to adapt the output power of the microwave generator to a specific target variable, such as an absorbed or reflected microwave power that remains as constant as possible, depending on the temperature or temperature change at the microwave generator.

[0026] One design solution is to change the field distribution by changing the setting value of at least one operating parameter of at least one microwave distribution device that changes the field distribution. Thus, the field distribution can be changed in a particularly targeted and accurate manner.

[0027] In one embodiment, the microwave distribution device has at least one adjustable operating parameter, which can take on at least two values ​​(setting values). If the setting value is changed, the field distribution usually also changes. The change when switching between two setting values ​​can be large or only small. The microwave distribution device can have one or more such operating parameters.

[0028] One embodiment is to change at least one setting value from the following operating parameter groups:

[0029] - Rotate the antenna's rotation angle;

[0030] - Rotate the antenna height position;

[0031] - the relative angle between the two wings of the rotating antenna;

[0032] - rotation angle of the mode stirrer;

[0033] - height position of the mode stirrer;

[0034] - the rotation angle of the turntable;

[0035] - Microwave frequency;

[0036] - Phase shift between different feed points;

[0037] - Activate or deactivate microwave feeding through multiple feed points;

[0038] - Change the power distribution between multiple feed points.

[0039] Rotating antennas are usually used to couple microwaves, in particular from a microwave guiding device connected to a microwave generator, into a cooking chamber. The rotating antennas often have one or more wings that protrude laterally from the axis of rotation and can be rotated, for example, by means of a stepper motor. The rotating antenna has a rotation angle As an operating parameter, the swivel angle can have, for example, a value range of [0°; 180°] or, if the swivel antenna can completely swivel around itself, a value range of [0°; 360°], for example in steps of 1°, 5°, 10°, etc. Adjustment of the swivel angle is usually used to change the field distribution in the cooking chamber, for example to avoid static hot spots.

[0040] The swivel antenna can additionally be height-adjustable, wherein the swivel antenna can then have a height position as a further operating parameter. The height position can also be used to change the field distribution in the cooking chamber.

[0041] If the swivel antenna has two or more wings, then in one embodiment at least two of the wings can be adjusted relative to one another about the swivel axis of the antenna, for example at intervals of 1°, 5°, 10°, etc. The relative angle can also be used to change the field distribution in the cooking chamber.

[0042] The field distribution in the cooking chamber can also be varied by changing the rotation angle and, if applicable, the height position of the mode stirrer or "stirrer" in the cooking chamber. The mode stirrer is provided primarily for varying the field distribution.

[0043] The field distribution can also be changed by adjusting the rotation angle of the turntable, in particular if an asymmetrically shaped object is present on the turntable.

[0044] Since the cooking chamber forms a resonance body for the microwaves, the field distribution can also be changed by adjusting the microwave frequency. The microwaves can be changed, for example, within the range of [2.4 GHz; 2.5 GHz], for example in steps of 0.001 GHz or 1 MHz.

[0045] In one embodiment, the magnitude of the change in the portion of the microwave power radiated into the cooking chamber that is reflected back from the cooking chamber to the microwave generator is determined by the temperature change. This determination can be performed particularly simply and quickly. Thus, for two consecutive different field distributions or pattern images, their reflected microwave powers can be roughly compared, for example, the second field distribution can have a larger, approximately the same, or smaller portion of the microwave power reflected back than the first field distribution. This is similar to the statement that the portion of the microwave power absorbed or dissipated in the cooking chamber is smaller, approximately the same, or larger in the second field distribution than in the first field distribution. In this embodiment, it is therefore determined by means of the temperature change whether the portion of the microwave power reflected back to the microwave generator is higher, the same, or lower for the field distribution before the switching time point between different setting values ​​or for the field distribution after this switching time point. Accordingly, depending on the qualifications of the current processing flow, the field distribution existing after the switching time point can be maintained or the setting value can be reset to the value existing before the switching time point.

[0046] One design solution is to

[0047] - record the temperature profile during the microwave treatment run,

[0048] - determine the slope of the curve before or after the transition point in time, at which the field distribution in the cooking chamber changes, and

[0049] From the difference in the slopes it is determined whether the reflected back portion of the microwave power is higher or lower for the field distribution before the switching time or for the field distribution after the switching time.

[0050] This results in the advantage of a reliable estimation of the reflected microwave power with very low computational effort. The slope of the curve can be determined, for example, by curve fitting of suitable curve segments.

[0051] In one embodiment, the slope is assumed to be the slope of a linear or virtually linear curve segment ("linear slope"). This allows a particularly simple evaluation. The assumption of linearity of the curve segment used to determine the slope is a good assumption in particular for situations where the microwave generator is not yet in thermal equilibrium or is still in a warming-up phase before the switching time point. This embodiment has the further advantage that it is particularly well suited for process sequences in which the field distribution changes relatively frequently (for example every 5 to 30 seconds).

[0052] The curve segment can be flattened, for example, in order to determine the slope.

[0053] One design solution is to determine the slope of the curve before the switching time point in the curve segment extending to shortly before the switching time point. This allows a particularly reliable comparison with the slope after the switching time point. If the switching time point is thus marked with tp, for example, then the curve segment can be The slope of the previous curve is determined from , where Δt1 is the duration of this curve segment.

[0054] One further development is to determine the slope of the curve starting from the switching time, for example in the curve segment In this. .

[0055] One embodiment is to determine the slope of the curve starting from the switching time point together with a predetermined delay time Δtd. This has the advantage that effects that occur temporarily during the delay time Δtd due to the switching of the field distribution do not influence the determination of the slope. The slope of the curve after the switching time point is thus in the curve segment The delay time Δtd may be, for example, 0.5 to 3 seconds, in particular 1 to 2 seconds.

[0056] One embodiment is that during the microwave treatment operation, at least one operating parameter of at least one microwave distribution device is adjusted based on the intensity of the associated reflected portion of the microwave power. This makes it particularly easy to adopt a favorable adjustment of the field distribution during the microwave treatment process. A combination of adjustment values ​​that can be adjusted at a common time point can also be referred to as an adjustment value group, a value tuple or a microwave parameter combination (MPK).

[0057] For example, only the field distribution or the associated setting of at least one operating parameter can be used to heat a liquid, in which case little microwave reflection occurs. This is because when heating a liquid it is desirable to introduce high microwave power into the liquid as quickly as possible. To achieve this, all microwaves that reflect a lot of microwave power are avoided, thus achieving a shorter cooking process.

[0058] An example of the opposite situation is the thawing process, where it is undesirable to continue heating the thawed areas as long as frozen areas are present in other parts of the food. As soon as thawed areas with liquid are formed, the so-called "runaway effect" occurs, because the thawed (liquid) areas convert the microwave energy into heat energy much faster than the frozen areas. By avoiding setting values ​​that lead to a field distribution with little reflection, uniform thawing can be supported.

[0059] In one embodiment, the method is used to keep the microwave power absorbed in the food being cooked as constant as possible during the treatment process or treatment sequence. If a state of strong reflection is detected, the output power of the magnetron can be increased, or vice versa, if the reflection from the cooking chamber decreases, the output power can be reduced. As a result, the food being cooked can always be exposed to at least approximately the same power during the treatment sequence, more precisely when the field distribution is changed regularly, for example in a targeted or random manner, in order to avoid static hot spots in the food being cooked.

[0060] Therefore, one configuration is usually to set at least one setting value in such a way that a lower reflected back portion of the microwave power results.

[0061] Typically, one configuration also consists in setting at least one setting value in such a way that a higher reflected back portion of the microwave power results.

[0062] During the process sequence, the specified target (e.g. a high or low reflected portion of the microwave power) can be changed. Thus, the frozen soup can first be thawed uniformly while avoiding setting values ​​that lead to a field distribution with little reflection and then be quickly heated by setting a field distribution with little reflection.

[0063] The object is also achieved by a microwave household appliance having a cooking chamber, a microwave generator, a temperature determination device for determining the temperature of the microwave generator, at least one microwave distribution device and a control device, wherein the control device is configured to carry out the above method. The microwave household appliance can be designed similarly to the method and has the same advantages. BRIEF DESCRIPTION OF THE DRAWINGS

[0064] The above-mentioned characteristics, features and advantages of the present invention and the manner and method of achieving these characteristics, features and advantages can be understood more clearly and distinctly in conjunction with the following schematic description of an embodiment explained in more detail with the aid of the accompanying drawings:

[0065] Figure 1 A sketch of a domestic microwave appliance is shown in side view as a cross-section;

[0066] Figure 2 The change trend of the temperature of the microwave generator of the household microwave appliance for different setting values ​​of the microwave distribution device is shown;

[0067] Figure 3 The temperature of the microwave generator until the equilibrium temperature is reached is shown for different setting values ​​of the microwave distribution device;

[0068] Figure 4shows the trend of the temperature change of the microwave generator when the setting value of the microwave distribution device is changed after reaching the equilibrium temperature; and

[0069] Figure 5 The graph shows the temperature profile of the microwave generator when the setting values ​​of the microwave distribution device are changed several times before the corresponding equilibrium temperature is reached. DETAILED DESCRIPTION

[0070] Figure 1 A microwave household appliance 1 is shown, which has a cooking chamber 2 with a feed opening 4 that can be closed by means of a door 3. Objects G can enter the cooking chamber 2 through the feed opening 4. The microwave household appliance 1 also has a microwave generator in the form of, for example, a magnetron 5. The microwaves radiated from the magnetron 5 are guided to the cooking chamber 2 by a microwave guide device 6 configured as a hollow conductor and there are coupled into the cooking chamber 2 by means of a rotating antenna 7. The rotating antenna 7 has antenna wings 8 in the cooking chamber 2 and can be rotated about a rotation axis D (for example, driven by a stepper motor not shown). The antenna wings 8 are provided to change the field distribution of the microwaves in the cooking chamber 2 when the rotating antenna 7 rotates. The rotating antenna 7 therefore also serves as a microwave distribution device. A temperature sensor 9 is mounted on the magnetron 5 to measure the temperature Tm ("magnetron temperature") of the magnetron 5. In addition, the microwave household appliance 1 also has a control device 10, which is also configured to drive the magnetron 5 (for example, adjust its output power), read out the measured value of the temperature sensor 9 and adjust the angular position or rotation angle of the rotating antenna 7 about the rotation axis D. .

[0071] The control device 10 is also configured (eg programmed) to control the microwave processing operation with the food G in the cooking chamber 2 and the normally functioning components as a function of the magnetron temperature Tm.

[0072] Figure 2 Two curves are shown as a graph of the magnetron temperature Tm in ° C. over the time t in seconds, more precisely for different rotation angles of the rotation antenna 7 for the same microwave power fed into the cooking chamber 2 and otherwise consistent with the experimental design. 1 and 2. Under the experimental design, the temperature change of one liter of water as a microwave absorbing load was determined according to the usual method for measuring the actual power output of microwave appliances. The time range between t = 20 s and t = 80 s defined by the vertical dashed line corresponds to a switch-on time or activation period of 60 s for the magnetron 5.

[0073] The microwave power introduced into the water load is also determined simultaneously with the temperature curve. 1 Set as operating parameters The setting value of 100% results in a lower temperature after one minute of processing or cooking than at the setting rotation angle. 2, the magnetron temperature Tm is significantly lower and the temperature rise of the water load (not shown) is greater. 1, less power is reflected back to the magnetron 5, so that a larger share of the microwave power fed in is available for heating the water load.

[0074] In the example shown here, for the rotation angle 1 confirmed a temperature excursion of 11.9 °C in water load, which corresponds to a power input of approximately 870 W. 2, the temperature stroke is only 9.8°C, which corresponds to a power input of about 710 W (calculated according to IEC 60705). 2, the microwave power reflected back to the magnetron 5 is therefore approximately greater than that at the rotation angle 1 is as high as 160 W. This results in 2. Therefore, the magnetron temperature Tm is at a rotation angle of 0.040° near the end of the on-time of the magnetron 5. 1 is about 76°C, at the rotation angle 2 is about 86° C. Although there are marginal effects such as different heating of the elements in the cooking chamber (walls (drum), glass panes of the door, etc.), these are not decisive.

[0075] Figure 3 The magnetron temperature Tm is shown for different rotation angles of the rotating antenna 7 when the magnetron 5 is permanently switched on until the equilibrium temperature is reached. 1. 2 and The changing trend of mult. mult refers to the rotation angle during the measurement time The setting of multiple values, in particular the permanent rotation of the rotating antenna 7.

[0076] During a relatively long heating process, a thermal equilibrium is established in the magnetron 5 due to the cooling of the magnetron 5 , from which the magnetron temperature corresponds constantly to the corresponding equilibrium temperature. The equilibrium temperature depends on the selected rotation angle (usually depends on the set of settings selected). A large reflection share of microwaves leads to a higher equilibrium temperature at a constant cooling power. For application If the scene marked by mult changes continuously during the processing sequence, for example due to antenna rotation, the thermal inertia of the magnetron 5 generates a constant change through all the rotation angles used. Take the average equilibrium temperature.

[0077] Figure 4 The rotation angle of the rotating antenna 7 is shown after reaching the equilibrium temperature. The change trend of magnetron temperature Tm during transformation.

[0078] If the rotation angle changes in the equilibrium state (here after t = 215 s from the rotation angle 1 to rotation angle 2) Due to the new reflection fraction, a slope of the temperature curve different from zero is generated. A positive slope means that at the new rotation angle more power is reflected back to the magnetron 5, and at a negative slope less power is reflected than at the previous rotation angle. The diagram shown shows a positive slope in the temperature curve. Therefore, at the rotation angle 2. There is a ratio at the rotation angle 1More power is reflected back. The temperature change at the magnetron 5 can be The change is observed about one second later, that is, it can be observed very quickly.

[0079] The proportion of the reflected microwave power can usually be stated either by comparison of the corresponding equilibrium states and / or by observing the value and, if necessary, the sign of the slope when leaving the equilibrium state. In practice, observing the slope is particularly advantageous, since this can be observed significantly faster.

[0080] Figure 5 The figure shows the rotation angle of the rotating antenna 7 before reaching the corresponding equilibrium temperature. The temperature change trend of the magnetron during multiple transformations.

[0081] If the currently set rotation angle The magnetron 5 is not yet in its thermal equilibrium state, so at the rotation angle The sign of the slope of the curve cannot be used to make any statement about the change in the temperature range below the lowest equilibrium temperature. Each change in, for example, leads to an increase in the magnetron temperature Tm and thus to a positive slope. In most cases, a change in the temperature leads to a sudden change in the slope, which is manifested as a bend in the curve or the temperature change trend.

[0082] In order to be able to state the reflected power proportion of the current field distribution, the rotation angle Change the slope m1 and rotation angle of the previous curve The slope m2 after the change is compared. If the slope m2 is greater than the previous rotation angle The greater the slope m1, the greater the share of reflected power.

[0083] Figure 5 In particular, the variation trend of the magnetron temperature Tm when the antenna position is changed multiple times is shown. The switching time points tp are labeled tp-1 to tp-4. At least for tp-2 to tp-4, the curve bending can be seen.

[0084] To evaluate the temperature curve, for example, the difference Δm between the slopes m1 and m2 before and after the respective switching time tp-1 to tp-4 can be determined. Therefore, the curve segment is considered to be well close to linear outside the transition time points tp-1 to tp-4.

[0085] The slope difference Δm can be calculated, for example, as:

[0086]

[0087] This means that it is calculated from the difference between the slope m2 and the slope m1, the slope m2 being determined by the curve segment after the switching time tp and having a duration Δt2, wherein this curve segment starts after tp with a delay of the delay time Δtd, and the slope m1 being determined by the curve segment of the duration Δt1, which ends shortly before the switching time tp. The delay time Δtd takes into account the thermal inertia of the system. This is usually only 1 to 2 seconds.

[0088] When the new rotation angle When less power is reflected back, then Δm < 0. When the new rotation angle When the same amount of power is reflected back, then Δm = 0, and at the new rotation angle When more power is reflected back, then Δm > 0.

[0089] The invention is of course not restricted to the exemplary embodiments shown.

[0090] “A”, “an” etc. may generally refer to the singular or the plural, especially in the sense of “at least one” or “one or more” etc., unless this is explicitly excluded by, for example, “exactly one” etc.

[0091] Numerical specifications may also include both the specified data and the customary tolerance ranges, unless this is explicitly excluded.

[0092] Reference numerals list

[0093] 1 Microwave household appliances

[0094] 2 Cooking room

[0095] 3 doors

[0096] 4 Feed opening

[0097] 5 Magnetron

[0098] 6 Microwave Guidance Device

[0099] 7 Rotate the antenna

[0100] 8 Antenna Wing

[0101] 9 Temperature sensor

[0102] 10 Control Device

[0103] D Rotation axis

[0104] G Cooking

[0105] m1 Slope before the transition time point

[0106] m2 Slope after the conversion time point

[0107] t time

[0108] tp-1 – tp4 Transition time point

[0109] Tm magnetron temperature

[0110] Rotation Angle

[0111] mult rotation angle sequence

[0112] 1 Rotation angle

[0113] 2 Rotation angle.

Claims

1. A method for operating a microwave household appliance (1), in which the microwave treatment operation is controlled as a function of the temperature (Tm) of the microwave generator (5), In the method, during the microwave processing operation, the field distribution in the cooking chamber (2) of the microwave household appliance (1) changes, and the microwave processing operation is controlled according to the temperature change of the microwave generator (5) caused by the change of the field distribution. In the method, the magnitude of the change in the portion of the microwave power radiated into the cooking chamber (2) that is reflected from the cooking chamber (2) back to the microwave generator (5) is determined from the temperature change; in: - recording the temperature profile during the operation of the microwave treatment, - determining the slope of the curve (m1, m2) before or after a switching time point (tp1-tp4) at which the field distribution in the cooking chamber (2) changes, and From the change in the slope (m1, m2), it is determined whether the reflected back portion of the microwave power is higher for the field distribution before the switching time (tp1-tp4) or for the field distribution after the switching time (tp1-tp4).

2. The method according to claim 1, wherein the field distribution is changed by changing at least one operating parameter of at least one microwave distribution device (7, 8) The field distribution is changed by adjusting the value.

3. The method according to claim 2, wherein at least one setting value from the following operating parameter groups is changed: - Rotation angle of the rotating antenna (7) - rotating the height position of the antenna (7); - rotation angle of the mode stirrer; - height position of the mode stirrer; - rotation angle of the turntable; - Microwave frequency; - Phase shift between different feed points; - Activate or deactivate the feeding of microwaves through a plurality of feeding points; - Changing the power distribution between multiple feed points.

4. A method according to any one of claims 1 to 3, in which the slope (m1) of the curve before the switching time point (tp1-tp4) is determined shortly before the switching time point (tp1-tp4), and / or the slope (m2) of the curve starting from the switching time point (tp1-tp4) together with a predetermined delay time is determined.

5. The method according to claim 2 or 3, wherein during the microwave treatment operation, at least one operating parameter of the at least one microwave distribution device (7) is adjusted based on the intensity of the associated reflected portion of the microwave power.

6. The method according to claim 5, wherein at least one setting value is set in such a way that This results in a lower reflected portion of the microwave power.

7. The method according to claim 5, wherein at least one setting value is set in such a way that This results in a higher reflected portion of the microwave power.

8. A microwave household appliance (1) comprising a cooking chamber (2), a microwave generator (5), a temperature determination device (9) for determining the temperature (Tm) of the microwave generator (5), at least one microwave distribution device (7, 8) and a control device (10), wherein: The control device (10) is configured to carry out the method according to any one of claims 1 to 7.

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