EP2941092B1 - Method and household appliance - Google Patents

Description

The present invention relates to a method for operating a domestic appliance according to the preamble of claim 1.

When treating items in a domestic appliance, the temperature of the items to be treated or its surroundings is often monitored. For example, the treatment process is influenced or automatically controlled as a function of the determined temperature. For the reliability and functionality of such automatic functions, it is therefore important to obtain reliable information about the temperatures prevailing in and on the material to be treated. In particular, the distribution of hot or cold zones or the temperature distribution over the volume of the item to be treated is particularly helpful information.

In the prior art, for example, cooking devices have become known in which the temperature inside the food is determined with a penetration probe during the cooking process. However, the use of such penetration probes is generally uncomfortable for the user. A penetration probe has also become known, which transmits the measured temperature wirelessly to the cooking appliance via electromagnetic waves. However, determining the temperature with penetration probes generally has the disadvantage that measurements are usually only carried out at the point of the probe and therefore only to a very limited extent locally. It is therefore z. B. no information about the temperature at the coldest or hottest point in the food.

Methods have also become known in which the temperature is measured without contact on the surface of the food to be cooked. Such measuring methods are more convenient for the user than, for example, measuring with penetration probes, but the temperature inside the food is not recorded. Therefore, although a statement can be made about the browning state, for example, a statement about the overall cooking state cannot be made reliably as a rule.

From the WO 2013/078325 A1 a method for heating an object is known in which the object is exposed to RF energy and changes in the electromagnetic spectrum are evaluated which occur due to the interaction between the object and acoustic waves. The evaluation is used to control the heating of the object.

The U.S. 5,237,141 A discloses a high-frequency heating device in which food is heated by microwave energy in a cooking space. A receiving antenna is provided with which a center frequency of the microwave energy is received, which is reflected back from the cooking space. The amount of radiation received by the receiving antenna is determined by means of an evaluation circuit and the functions of the heating device are controlled by means of a control circuit as a function of the radiation determined.

It is the object of the present invention to provide a method for operating a domestic appliance which enables an improved contactless temperature determination, in particular inside the item to be treated.

This object is achieved by a method having the features of claim 1. Preferred features are the subject of the subclaims. Further advantages and features emerge from the general description of the invention and the description of the exemplary embodiments.

The method according to the invention is used to operate a domestic appliance. At least one treatment device is provided for treating items to be treated in at least one treatment room. With at least one measuring system with at least one processing device, the temperature of at least part of the material to be treated is determined without contact. The treatment device is controlled as a function of the determined temperature. The measuring system generates electromagnetic measuring radiation at least at times. The measuring system brings the measuring radiation into the treatment room at least temporarily with at least one transmitting device. At least temporarily, measurement radiation that is directly reflected and influenced by the item to be treated is received by at least one receiving device of the measurement system. The measurement radiation has a bandwidth with at least two distinguishable frequencies. The measuring system detects at least one characteristic variable for a wave property of the received measuring radiation, taking into account the frequency. The processing device determines at least one characteristic parameter on the basis of the change in the wave property of the received measurement radiation in relation to the transmitted measurement radiation. The processing device derives the temperature on the basis of the frequency dependence of the parameter.

The method according to the invention has many advantages. A considerable advantage is that at least one parameter can be derived from the received measurement radiation in relation to the transmitted measurement radiation, the frequency of which can be used to determine the temperature. This allows z. B. the temperature inside or over the volume of the Items to be treated can be determined contactlessly and reliably. The temperature inside is usually more meaningful for the treatment process than just the surface temperature.

Such a temperature determination is particularly advantageous when preparing food, for example, since the volume temperature usually correlates closely with the required cooking time. A distribution of hot or cold zones in the item to be treated can also be determined in this way. It is also advantageous that the treatment device can be optimally controlled with knowledge of the internal temperature conditions. For example, the finished cooking point of a roast can be recognized based on the volume temperature and the heating source can be regulated down accordingly or a grill heating source can be switched on for browning.

The variable detected by the measuring system preferably describes a wave property such as, for. B. phase, amplitude, frequency, wavelength and / or polarization. Other variables that are customary in high-frequency technology or radar technology for recording signals are also possible. The variable detected by the measuring system is determined in particular as a function of frequency and / or as a function of time.

The change in the received measuring radiation in relation to the transmitted measuring radiation is preferably determined by changing at least one of the at least one variable detected by the measuring system. The change relates in particular to the phase and / or the amplitude of the measurement radiation. However, it is also possible that the change in the received measurement radiation in relation to the transmitted measurement radiation relates to the frequency and / or the wavelength and / or the polarization and / or the angle of rotation or at least one other common variable in high-frequency technology. The change is preferably detected and / or described by at least one scattering parameter or S-parameter. In particular, the radiation power absorbed by the material to be treated and / or the corresponding scattering parameter is taken into account as a function of the frequency.

The item to be treated is preferably an object which is essentially brought into the treatment room for treatment. This can be, for example, an object to be cleaned and / or dried and / or an item to be cooked or an object to be heated. However, it is also possible that the item to be treated is also and / or only introduced into the treatment room to determine the temperature.

Items to be treated within the meaning of this application can also be any object in the treatment room which, in particular, has been brought into the treatment room together with the object to be treated, such as, for. B. a cooking vessel, a laundry protection bag or a solvent or the like. It is possible that the The temperature of the actual item to be treated is determined together with the item to be treated as an aid and / or separately from the item to be treated as an aid.

Based on the change in the wave property, the complex permittivity and / or its real part and / or its imaginary part is determined and viewed as a function of the frequency. The temperature is derived from the frequency dependence of a maximum value of the function. Several and / or other suitable functional characteristics can also be used to determine the temperature.

For example, the position of the maximum in the course of the frequency dependence of the imaginary part depends on the temperature of the object with which the measurement radiation has interacted. In particular, the maximum migrates to higher frequencies with increasing temperature. As a further example, the real part of the complex permittivity is temperature-dependent at a frequency of 0 Hz. For example, the real part as a function of the frequency, at which the corresponding imaginary part assumes a maximum, is also temperature-dependent.

The complex permittivity and / or its real part and / or its imaginary part are determined in particular using at least one scattering parameter. The scattering parameter is determined in particular by the change in the received measurement radiation in relation to the transmitted measurement radiation as a function of the frequency.

It is possible and preferred that the determined frequency dependency of the complex permittivity and / or its real part and / or its imaginary part is compared with at least one reference parameter stored in at least one storage device. The reference parameter describes in particular the frequency dependence of the complex permittivity and / or its real part and / or its imaginary part of at least one known substance and / or body and / or material at at least one defined temperature. In particular, the temperature of at least part of the material to be treated is determined on the basis of the comparison. For this purpose, at least one value for a temperature and / or a temperature range is preferably assigned to a reference parameter. Reference parameters with discrete values and / or averaged values and / or value ranges can be provided for comparison. At least one mathematical approximation method can be used for the comparison. It is also possible that the comparison is at least partially adapted dynamically and / or is subject to an artificial learning ability.

The reference parameter preferably describes the frequency dependency of the complex permittivity and / or its real part and / or its imaginary part at least one Reference goods to be treated. The reference item to be treated has in particular a material and / or material composition that is comparable to the item to be treated. A reference parameter suitable for the comparison can also be assigned as a function of a temperature or other property that has already been determined for the item to be treated. It is also possible to assign a reference parameter based on a preset by the user, e.g. B. by selecting a category of items to be treated.

It is also preferred that the real part and the imaginary part of the complex permittivity are viewed as a locus in the Gaussian plane as a function of frequency and / or in a Cole-Cole diagram, so that the real part can describe an arc with a center point on the axis . The temperature is preferably determined on the basis of the center of the circle and / or the radius of the circle. Such a consideration has the advantage that the values of the real part and the imaginary part belonging to a common temperature range essentially lie on an arc of a circle. This enables an inexpensive and at the same time reliable assignment of temperature values. The observation can be done arithmetically and / or graphically.

It is possible that the description of the circular arc includes at least one mathematical approximation method, such as, for. B. an interpolation and / or an extrapolation. For example, an arc of a circle can also be fitted into the values of the complex permittivity, with the center of the circle and the radius of the circle being calculated from the arc. It is also possible that the center of the circle is calculated by forming secants and / or perpendicular lines. It can be taken into account that the center of the circle lies on the axis for the real part.

It is also preferred that the radius of the circular arc is compared with at least one reference value stored in at least one storage device of at least one known substance and / or body at at least one defined temperature. It is also possible that the position of the center of the circle on the axis for the real part is compared with at least one reference value of at least one known substance and / or body at at least one defined temperature stored in at least one storage device. The reference value preferably describes the radius and / or the position of the center of the circle of at least one reference item to be treated which is comparable to the item to be treated. The adjustment is preferably carried out in a similar way to the adjustment with the reference parameter described above.

The measuring radiation is preferably emitted repeatedly. In particular, the measurement radiation is emitted before the treatment and / or during the treatment and / or after the treatment of the item to be treated. Is preferred according to the respective Emission of the measurement radiation, the directly reflected measurement radiation influenced by the item to be treated is received again by the receiving device. In addition, the temperature of the item to be treated is preferably determined after the respective sending or receiving. The transmitting device preferably sends the measuring radiation to the item to be treated, so that the measuring radiation is applied to the item to be treated. This has the advantage that the treatment device can be optimally adjusted to the particular item to be treated by taking the temperature into account. It is also preferred that measuring radiation is repeatedly emitted during the treatment process and the temperature is determined. This is advantageous in that changes in temperature of the items to be treated are recognized during or due to the treatment and the treatment device can be adapted accordingly.

The measuring radiation preferably comprises at least two frequencies between 10 megahertz and 1 terahertz which differ by at least 100 MHz. Preferably, several and in particular a large number of different frequencies are provided. In this case, frequencies and / or frequency intervals can also be provided which border one another and / or at least partially overlap.

The measurement radiation can have a frequency width of at least 10% of the center frequency of the frequency band used. A frequency width of at least 10% of the arithmetic mean of the lower and upper limit frequency of the frequency band used is also possible. A frequency width of at least 20% of the corresponding arithmetic mean is preferred. The frequency width comprises in particular at least 250 megahertz and preferably at least 500 megahertz and / or at least one gigahertz and / or at least 5 gigahertz and particularly preferably more than 10 gigahertz. 20 gigahertz or more are also possible.

The frequencies are preferably in a frequency band with a bandwidth that is wider than the ISM band of a conventional microwave oven (approx. 2.4 GHz - 2.5 GHz). Multiple bands are also possible. In particular, at least two bands are provided, the center frequencies of which are spaced apart by at least one gigahertz and in particular at least five gigahertz and preferably 10 or more gigahertz.

The transmitting device and / or the receiving device can have at least one antenna device suitable for the respective frequency width for transmitting or receiving.

An antenna device which is operated as a transmitting device and as a receiving device is also possible. The antenna device can comprise one or two or more antennas for transmitting and / or receiving. There can be at least one Antenna array can be provided, the individual antenna units covering individual bands or band areas and preferably being operated in parallel.

According to the invention, the measuring system is designed as an ultra-broadband system which is designed to transmit and receive ultra-broadband signals and is operated as such. An ultra-wideband radar device is also possible. The advantages of such a broadband measuring system compared to narrowband technology are that very well resolved spectral information is available, by means of which the item to be treated can be characterized accordingly and precisely. The frequency width used or generated can be adjustable. The resolution of the determined temperature can thus be increased or reduced, depending on how detailed the information for the control of the treatment device should be.

It is also preferred that the transmission device transmits the measurement radiation at least temporarily as at least one pulse with a pulse duration shorter than one nanosecond. The pulse duration is preferably in the range of a hundred or less picoseconds. A pulse duration of a few picoseconds or less than one picosecond is also possible. In particular, the pulse duration is designed to be so short that the measurement radiation comprises as broad a frequency spectrum as possible in accordance with a corresponding Fourier transformation. In particular, one of the frequency ranges described above should be achieved. An actual pulse can be generated directly. The pulse can, however, also be formed by scanning a suitable frequency spectrum with a corresponding Fourier transformation.

It is also possible that the measuring system is at least partially designed as a reflectometer or is operated as such. At least one transmitting device and / or at least one receiving device can be designed as a reflectometer or comprise such a device. The reflectometer can be designed as a one-port refectometer in which the transmitting device and the receiving device are combined in a common reflectometer antenna device. A two-port reflectometer or a multi-port reflectometer is also possible. The reflectometer can be used to measure the measurement radiation reflected from the item to be treated and / or to measure the measurement radiation transmitted by the item to be treated. In particular, corresponding further scatter parameters are determined as a function of the frequency. This has the advantage that diverse and well-resolved information about the item to be treated is obtained.

It is particularly preferred that the measurement radiation received by the receiving device is analyzed by the processing device and that the measurement radiation that is received during a defined time window is taken into account. It is in particular, the start of the time window is at least partially dependent on the time at which the measurement radiation is transmitted. For example, the receiving device is synchronized with the transmitting device. In particular, essentially only the measurement radiation that is received during a defined time window is taken into account. The variable detected by the measuring system is determined in particular as a function of time.

The duration and / or the beginning of the time window can in particular be set. The time window is particularly preferably set in such a way that essentially only the measurement radiation reflected and / or transmitted by the item to be treated is detected. The setting is preferably made by the measuring system or the processing device. The time window can also be set as a function of the transmission time of the pulse and / or of the pulse duration. The setting can also be made depending on the measurement radiation that has already been received. The time window preferably begins after the pulse has been transmitted. The duration of the time window is selected in particular so that short or ultra-short pulses can also be used for the evaluation.

Such a development has the advantage that the selection of the time window can determine from which spatial area or from which distance the received measurement radiation originates. For example, the temperature determined from the measurement signal can be assigned to a specific area of the item to be treated. It is also possible that temperature values of the items to be treated are determined as a spatial distribution. The spatial distribution of the temperature can be displayed graphically and / or as an image. The measuring system can also determine spatially resolved and / or three-dimensional information about the item to be treated. Another advantage is that, with a correspondingly short time window, a spatially resolved analysis of the items to be treated is possible even in a correspondingly small treatment room.

It is possible that measurement radiation that is at least partially influenced and transmitted by the item to be treated is received. The use of measurement radiation transmitted and reflected by the item to be treated for determining the temperature enables a more detailed description of the item to be treated. In particular, at least one further receiving device and / or at least one further transmitting device is provided. Transmitting devices and receiving devices can also be operated in pairs, with measurement radiation transmitted and reflected by the material to be treated being recorded for at least one pair.

For example, one transmitting device and two receiving devices can be provided, the one receiving device essentially for the items to be treated reflected measuring radiation and the other receiving device is essentially provided for the measuring radiation transmitted by the material to be treated. However, it is also possible for two transmitting devices and one receiving device to be provided. One of the transmitting devices is arranged in such a way that its measurement radiation hits the receiving device after being reflected from the material to be treated. The other transmitting device is arranged in particular in such a way that its measuring radiation hits the receiving device after transmission through the material to be treated.

Figur 1

eine stark schematisierte Darstellung eines Hausgeräts in einer perspektivischen Ansicht;

Figur 2

eine stark schematisierte Darstellung eines Hausgeräts mit einem Messsystem in einer geschnittenen Seitenansicht;

Figur 3

ein weiteres Hausgerät mit einem Messsystem in einer geschnittenen Seitenansicht;

Figur 4

ein anderes Hausgerät mit einem Messsystem in einer geschnittenen Seitenansicht;

Figur 5

noch ein weiteres Hausgerät mit einem Messsystem in einer geschnittenen Seitenansicht;

Figur 6

eine weitere Ausgestaltung eines Hausgeräts mit einem Messsystem in einer geschnittenen Seitenansicht; und

Fig. 7

noch eine weitere Ausgestaltung eines Hausgeräts mit einem Messsystem in einer geschnittenen Seitenansicht.

In the figures show:

Figure 1

a highly schematic representation of a household appliance in a perspective view;

Figure 2

a highly schematic representation of a domestic appliance with a measuring system in a sectional side view;

Figure 3

a further domestic appliance with a measuring system in a sectional side view;

Figure 4

another household appliance with a measuring system in a sectional side view;

Figure 5

yet another household appliance with a measuring system in a sectional side view;

Figure 6

a further embodiment of a household appliance with a measuring system in a sectional side view; and

Fig. 7

yet another embodiment of a domestic appliance with a measuring system in a sectional side view.

The Figure 1 shows a domestic appliance 1, which is designed here as a cooking appliance 100. The cooking appliance 100 has a treatment space 3 designed as a cooking space 13. A treatment device 2 is provided for treating the items to be treated 200. The treatment device 2 comprises a thermal heating source 103 and a heating device 12.

The heating device 12 is provided for dielectric heating of the material to be treated 200 and is designed here as a microwave heating source. The cooking space 13 can be closed by a door 104. A safety device, not shown here, is provided, which prevents operation of the heating device 12 when the door is open, so that an escape of microwave radiation is counteracted. To heat the cooking space 104, further heating sources, such as, for example, an upper heating element and a lower heating element or a steam heating source or the like, can be provided.

The cooking appliance 100 can be operated via an operating device 6. For example, the temperature in the cooking chamber 13 can be set during the treatment process.

Various other program operating modes and automatic functions can preferably also be set. Operation via a touch-sensitive surface or via a touchscreen or remotely via a computer, smartphone or the like is also possible.

The domestic appliance 1 also has a measuring system 4, which is shown here in a highly schematic manner. The measuring system 4 is provided for the contactless determination of various characteristic parameters of the item 200 to be treated. The treatment device 2 is controlled as a function of the determined parameters. One parameter can be, for example, the internal temperature of the items to be treated 200. The measuring system 4 can, for. B. also determine the distribution of resonance modes at certain frequencies in the treatment room.

The measuring system 4 comprises a transmitting device 14, a receiving device 24, a processing device 5 and a storage device 7. The transmitting device 14 is suitable and designed to generate electromagnetic measurement radiation and to send it into the treatment room. In this case, at least part of the measurement radiation interacts with the item to be treated 200, not shown here, and is reflected again by it. The reflected measurement radiation is received by the receiving device 24.

At least one characteristic variable for a wave property of the received measuring radiation is detected by the measuring system 4. For example, the amplitude, frequency, phase or polarization or angle of rotation is recorded as a wave property. The processing device 5 then determines the characteristic parameters of the material to be treated 200 from the change in the wave properties of the received measurement radiation in relation to the transmitted measurement radiation be.

The determined parameters are taken into account in the treatment of the items 200 to be treated. The treatment device 2 is controlled as a function of the determined parameters. Preferably, the treatment device 2 is with the Measuring system 4 actively connected. It is possible that further control devices, not shown here, are provided. For example, the temperature in the interior of the items to be treated 200 can be determined as a parameter. Depending on this temperature, the heating power of the thermal heating source 103 can then be adjusted accordingly.

If the item to be treated 200 is a roast, for example, the heating power of the heating source 103 is regulated in such a way that optimal temperature conditions prevail in the cooking space 13 for cooking the roast. When controlling the treatment process, taking into account the determined parameters, target parameters specified by the user can also be taken into account. In the example of the roast, the user can e.g. B. pretend whether he wants a particularly crispy roast crust. In this case, the temperature of the thermal heating source 103 is increased or a grill heating source is switched on when the measuring system 4 determines a temperature in the interior of the roast which corresponds to a finished cooking point.

In the Figure 2 a household appliance 1 is shown in a highly schematic, sectional side view. The domestic appliance 1 is here a cooking appliance 100 with a treatment space 3 designed as a cooking space 13. The treatment device 2 comprises a thermal heating source 103, the output of which is regulated by a control device 42. The control device 42 is also operatively connected to the measuring system 4. The measuring system 4 is designed as a reflectometer device 54, which is designed as a one-port reflectometer. The transmitting device 14 and the receiving device 24 are housed together in a reflectometer antenna, which thus simultaneously serves as a transmitter and receiver.

The reflectometer device 54 is also designed here as a broadband radar reflectometer. For this purpose, electromagnetic measurement radiation is generated and sent, which preferably lies in a frequency band that is at least 10 gigahertz wide. For example, the frequency band here is 15 gigahertz or 20 gigahertz or more wide. The measuring radiation comprises at least two frequencies and preferably a plurality of frequencies. At least two of the frequencies differ by at least 100 gigahertz or more. The measuring radiation can preferably also have a frequency width of 10% or more of the center frequency of the frequency band used.

The measuring radiation is sent from the transmission device 14 into the treatment room 3. In the treatment room 3, the measurement radiation interacts, among other things, with the item 200 to be treated and is reflected by it. The reflected measurement radiation is detected by the receiving device 24. Two independent variables are measured here, e.g. B. Amount and Phase. The processing device 5 uses the detected variables to determine the Frequency dependence of the ratio of the radiant power sent into the treatment room 3 to the reflected radiant power. The measured variables can be designated, for example, with the scatter parameter S11, as they are also known from vector network analyzers.

The processing device 5 first calculates the real part components and the imaginary part components of the complex permittivity epsilon for each measurement frequency from the measured, frequency-dependent scattering parameter S11 (as complex numbers, contain two independent measured variables). The complex S11 can be converted into a complex epsilon. The permittivity describes the properties of the material in interaction with the measurement radiation for the item to be treated 200 on which the measurement radiation was reflected. This interaction is dependent, among other things, on the temperature of the material to be treated 200, which can advantageously be used to determine the temperature.

To determine the temperature of the material to be treated 200, the real part and the imaginary part of the complex permittivity are computationally considered by the processing device 5 in a Cole-Cole diagram. As a result, a circular arc with a center point on the axis can be described for the real part. The temperature of the item to be treated 200 results from the radius of the circle or the position of the center of the circle on the real part axis.

The values for the radius or center of the circle are then compared by the processing device 5 with corresponding reference values which are stored in the memory device 7 of the measuring system 4. The reference value is, for example, a value for the radius of the circular arc or the position of the center of the circle on the real part axis of a known substance at defined temperatures. Reference values obtained by measuring defined items to be treated or by corresponding simulations are also possible. If the item to be treated 200 is a food, for example, reference values for water or objects containing water provide correspondingly comparable results for the temperature determination on the basis of the typical water content of food.

For the determination of the circle radius or the circle center point it is advantageous that the corresponding measurement points for the permittivity are as far away as possible on the circle radius. The methods presented here as well as the household appliances are particularly advantageous because a broadband radar reflectometer or ultra-broadband radars are used. The broadband measurement radiation used here enables the corresponding measurement points for the permittivity to be far apart in terms of frequency, so that a corresponding accuracy and reliability of the temperature determination is possible.

Another advantage of the broadband measurement radiation is that a correspondingly few measurement points are sufficient for a reliable temperature determination. In the case of a broadband measurement radiation, the measurement points are so far away on the circle radius that a reliable construction of the circle center z. B. is possible by secant formation and establishment of the vertical center line. The center of the circle lies at the intersection of the vertical line on the secant. The center of the circle can also result from the mean value of the points of intersection of all perpendicular lines on the secants with the axis for the real part of the permittivity. The additional information that the center point must lie on the real part axis is used here. It is also possible to fit a circle into all existing measuring points for the permittivity or to calculate approximately. The center point or circle radius is then calculated from this circle.

The broadband measurement radiation enables measurement points to be recorded which are so far apart on the circle radius that the secants are as long as possible. Such methods have the advantage that the entire frequency band does not have to be scanned to map the semicircle, but only a few measuring points from which the circle can then be calculated. For example, in the case of water, a frequency band of around 1000 gigahertz is required to image a complete semicircle at 0 ° C. However, measurements in such a broad frequency band require a very high level of technical effort. The previously presented method enables a considerably less complex temperature determination, since a narrower band with fewer frequencies to be scanned can be used.

For example, a reliable temperature determination of water or aqueous treatment items 200 is possible by means of measured values from a frequency band around only 10 gigahertz. Depending on the required accuracy, a lower or a higher frequency range is also possible. The method therefore requires only a correspondingly low level of technical effort, so that it can also be used economically in conventional household appliances. Another advantage of viewing in a Cole-Cole diagram is that it is relatively safe to infer the circle from a comparatively small partial circle segment, because it is known that it is a circle and not an ellipse or another indeterminate course of function.

The reflectometer device 54 can also be designed as a two-port or multi-port reflectometer device 54. For this purpose, further transmitting devices 14 or receiving devices 24 can be provided. For example, the principle of transmission measurement is also possible. This can be particularly advantageous in the case of certain geometric conditions in the treatment room 3. In addition to the reflection on Material to be treated 200, the transmission through the material to be treated 200 also accessible for measurement. In addition to the scattering parameters S11, the scattering parameters S12, S21 and S22 can also be determined. Two or more reflectometer antennas can also be provided for this purpose. If there are more than two antennas, a variant is to operate them in pairs and to determine reflection and transmission for each pair.

The household appliance 1 shown here can, as an alternative to the reflectometer device 54, also be designed with an ultra-broadband radar device 44, as it is e.g. B. in the Fig. 3 is described.

It may be necessary to discriminate against other reflections for the measurement, e.g. B. on the walls of the treatment room. No continuous wave train is used in the time domain, only a very short pulse is emitted. This can be done by actually generating a pulse directly or by forming the required pulse by scanning a suitable frequency spectrum according to Fourier transformation. In order to only take into account the reflection on the material to be treated 200 of interest, the transmitting device 24 is only opened for a specific time window. It is also possible that the processing device 5 only takes into account measurement radiation from a specific time window. The time window preferably only comprises the duration of the reflex from the material to be treated 200. The receiving device 24 or the processing device 5 is synchronized with the transmitting device 14 for generating the pulse.

Such a method and the domestic appliance 1 designed for such a method enable a very reliable and contactless temperature determination of the item 200 to be treated. A particular advantage is that the temperature inside an object or item 200 can be measured without contact. With knowledge of the internal temperature or the volume temperature, the treatment process and the treatment device 2 can be influenced in a particularly targeted manner. For example, the heating source 103 is controlled in such a way that the material to be treated 200 has an optimal temperature for the respective treatment. Another particular advantage is that the volume temperature generally correlates very closely with the required cooking time of a product to be cooked. This enables very reliable control of automatic functions.

The Figure 3 time a household appliance 1 in a highly schematic side view. The domestic appliance 1 is designed here as a cooking appliance 100. The treatment space 3 is a cooking space 13 and can be heated by a treatment device 2 designed as a thermal heating source 103. The heating source 103 is operatively connected to a control device 42 and can through these are regulated. The measuring system 4 is provided for determining characteristic parameters of the material to be treated 200 and is designed as an ultra-broadband radar device 44.

The ultra-wideband radar device 44 here has two antennas 440, 441 opposite one another. In this case, each antenna comprises a transmitting device 14, 140 and a receiving device 24, 240. The antenna 440, 441 can thus work as a transmitter and receiver. The bandwidth of the radar is preferably greater than 250 megahertz and preferably greater than 10% of the center frequency of the frequency band used. A frequency band which has been released for such ultra-broadband applications is particularly preferably used. A particularly preferred frequency range is, for example, from 100 megahertz to 30 gigahertz or even 100 gigahertz.

The measuring system 4 generates measuring radiation and sends it out into the treatment room 3 and to the item 200 to be treated. A part of the measurement radiation is reflected by the material to be treated 200 and runs back to the antenna 440, 441 from which the measurement radiation was emitted. Another part of the measurement radiation is transmitted by the material to be treated 200 and passed through to the antenna 440, 441 opposite. It is thus possible to detect measurement radiation reflected and transmitted by the item 200 to be treated. The measuring system 4 detects at least one characteristic variable for a wave property of the received measuring radiation, such as. B. the amplitude, frequency, phase or polarization or angle of rotation. The characteristic parameter of the material to be treated 200 is determined on the basis of the change in the wave property of the received measurement radiation in relation to the transmitted measurement radiation. The change relates in particular to the phase and / or the amplitude and / or other characteristic parameters and can be described, for example, by corresponding scatter parameters.

The processing device 5 calculates the real part and the imaginary part of the complex permittivity from the recorded wave properties. The processing device 5 takes into account the frequency of the transmitted or received measurement radiation, so that the complex permittivity or its real part or imaginary part can be determined as a function of the respective frequency or as a function of the frequency. On the basis of the complex permittivity and its frequency dependency, the most varied of characteristic parameters for the material to be treated 200 can be calculated by the processing device 5.

For example, the outer contour of the item to be treated 200, the temperature distribution or the moisture distribution inside the item to be treated 200, the material composition, the density distribution and numerous other properties of the Items to be treated 200, which can interact with electromagnetic measurement radiation, are shown. A wide variety of parameters can be spatially resolved or determined or represented in an integrated manner over the volume of the items to be treated 200. So z. B. from the integral moisture content in the material to be treated 200 over the treatment time of the moisture loss of the material to be treated 200 and thus z. B. the cooking process can be determined.

The transmission devices 14, 140 of the ultra-wideband radar device 44 are designed here to transmit ultra-short pulses. For example, the duration of the pulses is in the picosecond range. The pulses have correspondingly steep edges. In the frequency representation, a correspondingly large bandwidth of typically a few GHz and z. B. of 10 or 20 GHz or more can be described. The receiving devices 24, 240 are designed to receive the broadband pulses. In this case, the receiving devices 24, 240 only detect the measurement radiation which lies in a specific time window. The time window begins at an adjustable time after the transmission pulse has been sent. Such a time window makes it possible to determine from which spatial area of the treatment room 3 or of the item 200 the received measurement signal originates.

The impulse is influenced by the interaction with the material to be treated 200 in such a way that characteristic wave variables such as the phase or amplitude change. The changes are recorded by the measuring system 4 and evaluated by the processing device 5 as a function of time, so that the electrical properties of the item to be treated can be determined in precisely the spatial area from which the received measuring radiation originates. The spatial resolution is larger or smaller depending on the frequency bandwidth used for the measurement radiation. If, for example, the spatial resolution is to be less detailed, a lower frequency bandwidth can be used or the spatial information can be averaged.

The Figure 4 shows a highly schematic representation of a further domestic appliance in a side view. The measuring system here has an ultra-wideband radar device 44, which has a pivotable transmitter device 14 and a pivotable receiver device 24. The pivoting enables a spatially resolved description of characteristic parameters of the material to be treated 200 with only one transmitting device 14 and one receiving device 24.

The receiving device 24 is preferably pivoted in a spacing grid along the item 200 to be treated. The transmitting device 14 retains its position. At each pivot position of the receiving device 24, measurement radiation is recorded over the entire observed frequency band. The receiving device 24 has a time window for the reception of the measurement radiation reflected and transmitted on the item to be treated, which is preferably passed through completely once. The transmitting device 14 is then moved, the receiving device 24 being pivoted again along the spacing grid at this new position.

It is also possible to work with a directional characteristic so that the transmitting device 14 is pivoted when the receiving device 24 receives a signal with a corresponding phase shift. The above-described measurement run can also be repeated in a desired time pattern in order to observe the behavior over time of the characteristic variable of the material to be treated 200.

The Figure 5 FIG. 4 shows a further embodiment of a measuring system 4 with an ultra-wideband radar device 44. In contrast to that in FIG Figure 4 The measuring system presented here is equipped with movable receiving devices 24, 240. The transmitting device 14 is pivotable. During a measurement process, the transmitting device 14 assumes a specific pivot position, while the receiving devices 24, 240 are moved along the item 200 to be treated. The receiving devices 24, 240 are preferably moved along a predetermined spacing grid. Other combinations of stationary, movable and / or pivotable transmitting devices 14 or receiving devices are also possible.

In the Figure 6 A domestic appliance 1 is shown with a measuring system 4 which enables the distribution of the radiation power in the treatment room 3 to be determined. For example, cavity resonances are determined as a function of frequency. The treatment space is designed as a cooking space 13. The electrical heating device 12 is provided for heating the cooking space 13. The heating device 12 has an oscillator device 52 and an amplifier device 62, which together generate and amplify electromagnetic radiation power for heating the cooking space 13. The heating device 12 is controlled by a control device 42.

The measuring system 4 is designed here as an ultra-wideband radar device 44 and has a transmitting device 14, a receiving device 24 and a processing device 5. The measuring system 4 works essentially similarly to that in FIG Figure 3 The measuring system 4 shown here determines a spatial power distribution of electromagnetic radiation on the basis of the change in the wave properties of the received measuring radiation in relation to the transmitted measuring radiation. The power of the measurement radiation absorbed by the treatment room 3 and / or by the item 200 to be treated is determined as a function of the frequency. The measuring system can also be a Have ultra-wideband radar device 44 or a reflectometer device 54, as previously described.

Depending on which power of the measurement radiation of a certain frequency arrives at the receiving device 24, the common cavity resonances of the treatment room 3 and the items to be treated 200 can be determined for this frequency. The ultrashort pulses emitted as measurement radiation range from picoseconds to nanoseconds or microseconds. The frequency bandwidths associated with the Fourier transformation are in particular in the range of a few 10MHz to 1 THz. The pulse duration is advantageously selected such that the reflected measuring radiation in the treatment room 3 is not superimposed with the incoming pulse on the way to the receiving device 24. In particular, the pulse length is selected to be so short that multiple reflections from different areas of the treatment room 3 can be discriminated against reflections on the treatment room 200. For this purpose, the time window is preferably set as described above.

The frequency-dependent difference between the transmitted and received power of the measurement radiation results in cavity resonances at certain frequencies. With such cavity resonances, a particularly large amount of radiation power is absorbed by the item 200 and the treatment space 3. In this case, it is preferably assumed that the treatment room 3, which is usually lined with metal, shows an absorption that is negligible compared to the item 200 to be treated. The cavity resonances are interpreted in particular in such a way that they describe the field distribution or the spatial distribution of the electromagnetic power supply within the treatment room and in particular within the item 200 to be treated.

The cavity resonances therefore decisively determine the temperature distribution in the material to be treated 200. The cavity resonances thus described by the measuring system 4 can essentially also be transferred to the radiant power supplied by the heating device 12 into the treatment room 3. A prediction can therefore be made as to which cavity resonances will occur when the heating device is active. Such a measurement method thus has the advantage that the spatial distribution of the radiant powers that can be supplied by the heating device 12 can be precisely described for a given item 200 in a treatment room 3. As a result, the power supply to the material to be treated 200 can be specifically influenced, e.g. B. by stirrer or alignment of the material to be treated 200.

In this case, the complex permittivity is preferably determined for each measurement frequency in the frequency band of the ultra-wideband radar device 44. The absorption, reflection and transmission of electromagnetic radiation power of the respective frequency can thus be determined for the item 200 to be treated.

The domestic appliance 1 shown here also has the advantage that the heating device 12 can be controlled in accordance with the previously determined spatial power distribution. For this purpose, the oscillator device 52 can be used to generate radiant power with the specific frequency or in a specific frequency range. For this purpose, the oscillator device 52 is operatively connected to the control device 42 and can be controlled by it. As a result, the frequency of the radiant power emitted by the heating device can be set as a function of the power distribution determined by the measuring system or the determined cavity resonances.

Depending on whether a high or low power supply to the item to be treated 200 is desired, a frequency is selected for which the item to be treated has previously shown a high or low absorption capacity in the measurement run. It is also possible that the heating device 12 emits radiant power at different frequencies over time, so that certain field distributions or cavity resonances can be superimposed one after the other in time. With knowledge of the spatial absorption capacity of the items to be treated 200, it is also possible to supply certain areas of the items to be treated 200 with a high radiation power and to administer a correspondingly low radiation power to other areas. For example, food to be cooked can be heated more intensely in an inner area than in an outer area.

The Figure 7 FIG. 3 shows a domestic appliance 1 embodied as a cooking appliance 100 with a measuring system 4. The measuring system 4 essentially corresponds to the measuring system 4, as shown in FIG Figure 6 has been described. The heating device 12 here has a transmission device 22. The transmission device 22 is connected to the heating device 12 via a waveguide device 72. The transmission device 22 is provided here to distribute the electromagnetic radiation power generated by the heating device 12 in the treatment room 3. For this purpose, the transmission device 22 can be designed, for example, as a stirrer or impeller or the like. In particular, metallic conductive sheets are provided, which are moved by a motor and lead to a deflection of the radiation power sent into the treatment room 3. Thus, depending on the position of the stirrer or the rotary vane, different vibration modes or cavity resonances are achieved in the treatment room 3.

The cooking appliance 100 also has a positioning device 32 here. The positioning is designed, for example, as a rotary plate and is used to position or move the items 200 in the treatment room 3.

The transmission device 22 is operatively connected here to a control device 42, which in turn is operatively connected to the measuring system 4. As a result, the transmission device 22 can be controlled as a function of the information ascertained by the measuring system. The transmission device 22 is preferably aligned in such a way that a desired power supply to the material to be treated 200 is achieved. Here z. B. programs set by the user or other targets are taken into account. The change in the cavity resonances in the treatment room 3 after the position of the transmission device 22 has been changed can be monitored by the measuring system 4. For example, the measuring system 4 transmits the cavity resonances again when the transmission device 22 has been changed. It is also possible for the positioning device 32 to be set as a function of the cavity resonances determined by the measuring system 4.

By means of the transmission device 22 and / or the positioning device 32 and its control as a function of the determined power distribution, different resonances in the treatment room 3 can be realized in a targeted manner in time. In this way, different spatial distributions for the input of power into the material to be treated 200 can also be implemented. The dwell times when approaching a specific cavity resonance are described in particular by a weighted sum. It is determined how long each resonance has to be approached for an optimal result. It can also be determined how the corresponding cavity resonance is to be realized, so z. B. by the positioning device 32 or by a corresponding setting of the transmission device 22.

The desired cavity resonance can also be approached in that the heating device 12 emits radiant power at a certain frequency, as is the case, for example, for the cooking appliance 100 in FIG Figure 6 has been described. The information contained in the weighted sum can preferably have been determined in advance by a simulation or also by experiments. This information and other previously determined parameters of a power distribution are preferably stored as reference parameters in a memory device of the domestic appliance 1. When the user selects a corresponding automatic program or another target specification, the reference parameters can then be called up, adapted to the situation.

List of reference symbols

1

Home appliance

2

Treatment facility

3

Treatment room

4th

Measuring system

5

Processing facility

6th

Control device

7th

Storage facility

12th

Heating device

13th

Cooking space

14th

Sending facility

22nd

Transmission facility

24

Receiving device

32

Positioning device

42

Control device

44

Ultra wideband radar device

52

Oscillator device

54

Reflectometer device

62

Amplifier device

72

Waveguide device

100

Cooking appliance

103

Heating source

104

door

140

Sending facility

200

Item to be treated

240

Receiving device

440

antenna

441

antenna

Claims (8)

1. Method for operating a domestic appliance (1) comprising at least one treatment device (2) for treating items to be treated (200) in at least one treatment chamber (3), the temperature of at least part of the item to be treated (200) being determined contactlessly by means of at least one measuring system (4) comprising at least one processing device (5), and the treatment device (2) being controlled according to the determined temperature, the measuring system (4) generating electromagnetic measuring radiation, at least intermittently, and introducing said radiation into the treatment chamber (3) by means of at least one transmitting device (14), and directly reflected measuring radiation that interacts with the item to be treated (200) being received, at least intermittently, by at least one receiving device (24) of the measuring system (4), the measuring system being designed to transmit and receive ultra-broadband signals having a frequency width of at least 250 MHz and being operated as such, characterised in that the transmitting device (14) repeatedly emits the measuring radiation as at least one ultra-short pulse having a pulse duration shorter than one nanosecond, the measuring system detecting at least the phase and the amplitude as a wave property of the received measuring radiation, taking into account the frequency, the processing device (5) determining the complex permittivity on the basis of the change in the wave property of the received measuring radiation in relation to the transmitted measuring radiation and considering said complex permittivity as a function of the frequency, the temperature being derived on the basis of the frequency dependence of a maximum value of the function.
2. Method according to the preceding claim, characterised in that the determined frequency dependence of the complex permittivity is compared with at least one reference parameter stored in at least one storage device (7), the reference parameter describing the frequency dependence of the complex permittivity of at least one known substance and/or body at at least one defined temperature.
3. Method according to either of the two preceding claims, characterised in that the real part and the imaginary part of the complex permittivity are considered to be a locus in a Cole-Cole diagram such that an arc of a circle having a centre point on the axis can be described for the real part, the temperature being determined on the basis of the centre of the circle or the radius of the circle.
4. Method according to the preceding claim, characterised in that the radius of the arc of the circle or the position of the centre of the circle on the axis for the real part is compared with at least one reference value stored in at least one storage device (7) for at least one known substance and/or body at at least one defined temperature.
5. Method according to any of the preceding claims, characterised in that the measuring radiation is emitted repeatedly.
6. Method according to any of the preceding claims, characterised in that the measuring radiation has at least two frequencies between 10 megahertz and 1 terahertz which differ from one another by at least 100 MHz.
7. Method according to any of the preceding claims, characterised in that the measuring radiation has a frequency width of at least 10% of the centre frequency of the frequency band used.
8. Method according to any of the preceding claims, characterised in that the measuring radiation received by the receiving device (24) is analysed by the processing device (5), and in that the measuring radiation which was received during a defined time frame is taken into account, the beginning of the time frame at least partially depending on the time at which the measuring radiation was emitted.

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