DETECTING A STOPPAGE OF A ROTATABLE MICROWAVE DISTRIBUTOR

Description

[0001] The invention relates to a method for detecting a standstill of a rotatable microwave distribution device of a household microwave appliance, in which at least one microwave leakage radiation is measured during a feed of microwaves into a cooking chamber of the household microwave appliance. The invention also relates to a household microwave appliance comprising a cooking chamber, a microwave generator for generating microwaves, at least one rotatable microwave distribution device for varying a field distribution of microwaves fed into the cooking chamber, at least one leakage radiation measuring device for measuring microwave leakage radiation, and a data processing device configured to carry out the method. The invention is particularly advantageously applicable to microwave cooking appliances, in particular ovens with a microwave function.

[0002] DE 10 2014 105256 A1 discloses a method for operating a household appliance and a household appliance with at least one heating device for dielectrically heating items to be treated by electromagnetic radiation in at least one treatment chamber. At least one measuring system with at least one processing device is provided. The measuring system is suitable and configured to generate electromagnetic measuring radiation. The measuring system has at least one transmitting device for at least temporarily transmitting electromagnetic measuring radiation into the treatment chamber and at least one receiving device for at least temporarily receiving the measuring radiation transmitted into the treatment chamber. The measuring system is suitable and configured to detect at least one characteristic variable for a wave property of the received measuring radiation.The processing device is suitable and designed to determine at least one measure of a spatial power distribution of the radiation that can be fed into the treatment room by the heating device based on the change in the wave properties of the received measuring radiation in relation to the transmitted measuring radiation.

[0003] JP 2004259646 A discloses a device comprising a heating chamber, a high-frequency oscillator for generating high-frequency waves, and a waveguide for guiding the high-frequency wave generated by the high-frequency oscillator to the heating chamber. The device also includes two rotating antennas for radiating the high-frequency wave into the heating chamber and a control device for controlling the respective rotation speeds of the two rotating antennas.

[0004] EP 2 148 553 A1 discloses a method for detecting a microwave leakage emission using a microwave sensor device. A temporal profile of the detected microwave emission is stored for a time interval by a memory device connected to the microwave sensor device. A portion of the stored microwave emission is evaluated. A device is used for monitoring microwave leakage in a cooking appliance. A cooking appliance is equipped with a device for evaluating the microwave leakage.

[0005] JP 2007335377 A discloses a microwave heating apparatus including: a microwave generating means; a waveguide for transmitting the microwave from the microwave generating means; a heating chamber for accommodating an object to be heated by the microwave; a plurality of rotating antennas for radiating the microwave from the waveguide into the heating chamber; driving means for driving and rotating the rotating antennas; temperature distribution detecting means for detecting the temperature distribution inside the heating chamber; and controlling means for controlling an angular position of the rotating antennas by controlling the driving means in accordance with a detection result of the temperature distribution detecting means.

[0006] EP 0 467 224 A1 discloses a high-frequency heating apparatus and an electromagnetic wave detector for use in the high-frequency heating apparatus, which are arranged to estimate the condition of a food article placed in a heating chamber by detecting microwaves in the heating chamber.

[0007] CN 107 071 951 A discloses a microwave cooking appliance and a stirring antenna module of the microwave cooking appliance. The microwave cooking appliance includes a housing; a microwave transmitting device; a rotatable microwave stirrer; a driving device connected to the stirring device; and a rotation detecting device used to detect the rotation of the microwave stirrer and communicate with the microwave transmitting device to control the microwave transmitting device to stop operation when the microwave stirrer stops rotating.

[0008] JP 2010 175178 A discloses a rotation detection device for a rotating antenna, which is provided with: a photointerrupter provided outside a waveguide 8; a rotating antenna disposed inside the waveguide 8 and radiating microwaves into the interior of a heating chamber; and a light guide hole on a wall of the waveguide through which a detection light generated by a light-emitting element of the photointerrupter and reflected light leading from the rotating antenna to a light-receiving element are passed. Based on a change in the intensity of the reflected light from the rotating antenna, a rotation of the rotating antenna is detected.A film absorbing the reflected light in the waveband is formed on the hole inner surface, the periphery and the adjacent surface of the light guide hole to suppress a reflection factor incident on the light receiving element as noise.

[0009] JP 2001 185343 A discloses a microwave oven provided with a rotating antenna at the bottom of its heating chamber. Microwaves generated by a magnetron are scattered by a rotating antenna and fed into the heating chamber. A bottom plate is provided between the heating chamber and the antenna. The bottom plate is partially transparent, and through this transparent part, the rotation state of the antenna can be observed from inside the heating chamber.

[0010] Using a rotating antenna to introduce microwaves into a food preparation chamber or "cooking chamber" of a household microwave oven is advantageous because, as the antenna rotates, the microwave mode pattern varies within the cooking chamber, thus varying the distribution of local areas of particularly high microwave power (so-called "hot spots"), which in turn allows for particularly uniform heating of the food intended for heating in the cooking chamber. However, it can happen that the rotation of the rotating antenna stops unintentionally, for example, if the antenna motor driving the antenna fails. This unintentional stoppage is difficult for the user to detect, as the antenna motor operates almost silently during normal operation.Since the full microwave power is still delivered into the cooking chamber via the rotating antenna, and not all foods react sensitively to the standstill and immediately detect it (liquids, in particular, show little disadvantage in this regard), the user may not immediately notice that the rotating antenna is stopped. As a result, a habituation effect may occur with the reduced heating performance, or aging of the appliance may be blamed for the deterioration in heating.

[0011] One option is to monitor the rotation or standstill of the rotating antenna using a sensor such as a reed switch. However, this approach is disadvantageous in that it is unreliable over the lifetime of the household microwave oven, as thermal expansion causes the entire antenna structure to move noticeably during microwave operation (e.g., rise and fall with the ceiling of the cooking chamber), or it can only be implemented with considerable design effort.

[0012] It is the Task The aim of the present invention is to at least partially overcome the disadvantages of the prior art and, in particular, to provide a possibility, which can be implemented using structurally simple means, for reliably detecting an unwanted standstill of a rotating antenna of a household microwave appliance, even in the long term.

[0013] This object is achieved according to the features of the independent claims. Advantageous embodiments are the subject of the dependent claims, the description, and the drawings.

[0014] The object is achieved by a method for detecting a standstill of a rotatable microwave distribution device of a household microwave appliance, in which During the feeding of microwaves into a cooking chamber of the household microwave appliance, at least one microwave leakage radiation is monitored for angle-dependent recurring fluctuations and, if an absence of such fluctuations is detected, at least one action is triggered.

[0015] This process has the advantage of being particularly cost-effective and structurally simple, requiring relatively few components. The process can also be implemented with a particularly long service life and a low probability of failure, since the required components are fixed.

[0016] Furthermore, a standstill can be detected particularly reliably because only the desired target state (namely a changing mode image) is measured to determine it and not the functionality of upstream components that cause the target state (e.g. an antenna rotation) is monitored.

[0017] By detecting the standstill, better protection can be achieved against damage to components in the cooking chamber, e.g. against local overheating of an antenna cover and / or components that absorb microwave energy, such as lights, door glasses, silicone seals, etc.

[0018] The household microwave appliance can be a standalone microwave appliance or a microwave combination appliance. The microwave combination appliance can be an oven, in particular an oven, with additional microwave functionality or a microwave appliance with additional IR radiation heating elements. The household microwave appliance can also be considered a cooking appliance, in particular for treating food in the cooking chamber by exposing it to microwaves.

[0019] The at least one microwave distribution device may comprise or be at least one rotatable antenna ("rotating antenna"), via which microwaves generated by a microwave generator are fed into the cooking chamber. Alternatively or additionally, the at least one microwave distribution device may comprise or be at least one wobbler or stirrer.

[0020] Detecting the standstill of the rotatable microwave distribution device during the feeding of microwaves particularly comprises monitoring for a standstill of the microwave distribution device during microwave operation, during which the microwave distribution device should rotate. In other words, the method comprises detecting the standstill of the microwave distribution device during the feeding of microwaves with the rotation of the microwave distribution device activated or switched on.

[0021] The at least one microwave leakage radiation can comprise measuring or detecting microwave leakage radiation at one or more leakage locations using one or more leakage radiation measuring devices. The microwave leakage radiation is in particular microwave radiation that exits the cooking chamber through openings when the cooking chamber door is closed, e.g. through holes or gaps in a wall or muffle of the cooking chamber, through gaps between the wall and the cooking chamber door, etc. A leakage radiation measuring device is located in particular outside or on the outside of the cooking chamber, in particular behind or near one or more openings, and is configured to detect an intensity of the microwave leakage radiation, in particular its energy, power, etc. The generated measurement signal is representative of the intensity of the measured microwave leakage radiation.

[0022] The angle-dependent, recurring fluctuations in the microwave leakage radiation typically only occur during normal rotary operation (i.e., without faulty standstill) of the microwave distribution device, since it is assumed that the field distribution of the microwaves in the cooking chamber, and thus also the microwave leakage radiation, depend heavily on the rotary position of the microwave distribution device, whereas it remains at least approximately constant without rotation of the microwave distribution device. If the microwave distribution device is regularly set to a similar sequence of rotary positions during microwave operation, this should be reflected in a corresponding angle-dependent, recurring fluctuation in the microwave leakage radiation. If these fluctuations are absent during microwave operation with the microwave distribution device activated, this can be regarded as a result of the microwave distribution device being at a standstill.

[0023] In particular, the fluctuations to be monitored, especially patterns (see below), can be automatically identified from the microwave leakage radiation of one or, averaged, several initial rotation angle sequences (especially whole revolutions) of the microwave distribution device. This offers the advantage that characteristic fluctuations can be quickly and reliably identified and used to check for standstill.

[0024] The at least one triggerable action may include, for example, sending a message to a user and / or notifying customer service.

[0025] A further development is that the microwave distribution device is set to a predetermined temporal sequence of discrete rotation angles. This can be advantageous for omitting rotation angles that are less suitable for food processing.

[0026] One embodiment involves rotating the microwave distribution device in a uniform manner (e.g., continuously or stepwise), and monitoring the microwave leakage radiation for periodically recurring fluctuations. This provides the advantage of obtaining a particularly detailed and easily evaluated curve of measured values of the microwave leakage radiation versus the angle of rotation. For example, a measured value can be recorded or scheduled for analysis every 0.5°, 1°, 2°, 5°, etc.

[0027] It is a further development that the microwave distribution device rotates at a constant speed. It is a further development that the angle of rotation of the microwave distribution device is changed in steps, e.g., in steps of 0.5°, 1°, 2°, 5°, etc. It is a further development that phases of microwave operation with a rotating microwave distribution device are interspersed with phases with a stationary microwave distribution device. During the phases with a stationary microwave distribution device, the microwave leakage radiation does not need to be monitored for fluctuations.

[0028] One embodiment is that a periodically recurring sequence of at least one pattern in a profile of the microwave leakage radiation or the corresponding profile of the measurement signal of a leakage radiation measuring device detecting the microwave leakage radiation is monitored. The recurring detection of this pattern in the rhythm of the rotation of the microwave distribution device enables particularly reliable detection of its fault-related standstill. The pattern can comprise one or more characteristic, easily recognizable curve properties such as one or more extreme points (maxima and / or minima), (rising or falling) edges, plateaus, etc. If this pattern does not repeat at the same angle or angular range over several rotations of the microwave distribution device, it can be assumed that the microwave distribution device has stopped due to a fault.The curve may differ slightly between successive revolutions, particularly in terms of intensity, but the curve properties such as the presence of one or more extreme points, etc., should be qualitatively maintained.

[0029] One embodiment involves checking the microwave leakage radiation for a periodically recurring sequence of at least one minimum and at least one maximum. In a further development, successive minima and maxima (in any order) must also have a predefined minimum value separation (also referred to as a "min / max delta") from one another. This advantageously results in an easily evaluated criterion for determining standstill or, analogously, the presence of rotation. Therefore, to determine that no standstill is present, the value separation or difference should not fall below a predefined threshold. The predefined minimum value separation can, for example, be 20% of an average of the relevant minimum and maximum.

[0030] However, the microwave leakage radiation can also be checked for the periodically recurring sequence of other curve properties, possibly including quantitative boundary conditions, or their absence, for example the slope of a flank, the length of a plateau, etc.

[0031] In one embodiment, a cross-correlation of a section of the curve of the microwave leakage radiation or of the corresponding measurement signal stored in a data memory is continuously compared with a currently recorded section of the curve. This has the advantage that there is no need to determine predefined patterns in a curve. If the correlation measure for the corresponding angular range falls below a predefined correlation value, it can be concluded that the microwave distribution device is at a standstill. The section stored in the data memory can, for example, be automatically determined from one or more initial rotation angle sequences (in particular whole revolutions) of the microwave distribution device. This determination can comprise a random selection of one or more rotation angle sections; alternatively, one or more rotation angle sections can be selected based on predefined criteria, e.g.B. based on the presence of a certain property or shape of the curve.

[0032] In general, several patterns from different angles or angle ranges can be checked separately or individually for presence / absence and a standstill of the microwave distribution device can be determined if only one pattern, several patterns or all patterns no longer recur.

[0033] In one embodiment, the at least one microwave leakage radiation comprises a plurality of microwave leakage radiations measured at different leakage locations, each of which is monitored for angle-dependent, recurring fluctuations. This enables particularly reliable detection of a standstill of the rotatable microwave distribution device. This embodiment is particularly advantageous in the case where one or more leakage locations only provide insufficiently strong signals. For this embodiment, it can be advantageous that the microwave leakage radiation from leakage locations that produce too low a signal (where, for example, a certain signal threshold is not reached or exceeded during the course of one revolution) is not taken into account for the evaluation for a standstill.In general, the microwave leakage radiation originating from different leakage locations can be checked separately or individually for standstill and a standstill of the microwave distribution device can be determined if fluctuations in the microwave leakage radiation are detected as no longer recurring at only one leakage location, at several leakage locations or at all leakage locations.

[0034] In one embodiment, the at least one microwave leakage radiation comprises superimposed microwave leakage radiation occurring at several different leak locations and is monitored for angle-dependent recurring fluctuations. This provides the advantage of a particularly simple and cost-effective design, since a microwave sensor can measure microwave leakage radiation emerging at several leak locations. In particular, the microwave leakage radiation occurring at different leak locations can generate measurement signals in the microwave sensor, which are superimposed to form an overall measurement signal. In one further embodiment, the microwave sensor comprises an electrical line (which can also be referred to as a "sniffer line") that runs past several leak locations.The microwave leakage radiation induces electrical currents in the same electrical line, whereby the total current resulting from the superposition of the induced electrical currents corresponds to the measurement signal of the microwave sensor.

[0035] The object is also achieved by a microwave household appliance configured to execute the method described above. The microwave household appliance can be designed analogously to the method and has the same advantages.

[0036] It is an embodiment that the household microwave appliance comprises: a cooking chamber, a microwave generator for generating microwaves, a rotatable microwave distribution device for varying a field distribution of microwaves fed into the cooking chamber, at least one leakage radiation measuring device for measuring microwave leakage radiation and a data processing device which is configured to carry out the method.

[0037] The data processing device may correspond to the central control unit of the household microwave oven. It may have a data memory for storing measurement data.

[0038] An output of the microwave generator can be connected to one or more microwave guides or waveguides configured to guide the microwaves generated by the microwave generator to the cooking chamber. To feed the microwaves into the cooking chamber, the microwave guide leads, in particular, to one or more rotating antennas. The microwave generator can have an inverter. It can be a magnetron or a semiconductor-based microwave generator. In principle, the household microwave appliance can have one or more rotating antennas, one or more wobblers, and / or one or more microwave generators.

[0039] The above-described properties, features and advantages of this invention, as well as the manner in which they are achieved, will become clearer and more clearly understood in connection with the following schematic description of an embodiment, which is explained in more detail in connection with the drawings. Fig.1 shows a sectional side view of a household microwave oven; Fig.2 shows a curve of the intensity of a microwave leakage radiation with a rotating and a stationary rotating antenna; and Fig.3 shows a section of a Fig.2 shown measurement curve in the area of a time period with a rotating antenna.

[0040] Fig.1shows a sectional side view of a sketch of a household microwave appliance 1 with a cooking chamber 2. The cooking chamber 2 is surrounded by a cooking chamber wall 3, which has a front loading opening that can be closed with a door 4. The household microwave appliance 1 has at least one microwave generator 5 for treating the food to be cooked in the cooking chamber 2 (not shown), and optionally also further heating elements such as one or more resistance heating elements (not shown). The household microwave appliance 1 can then, in particular, be an oven with microwave functionality.

[0041] The microwave generator 5 is connected to a microwave guide 6, which at the other end opens into a dome 7 arranged on the ceiling. By means of the microwave guide 6, the MW microwaves generated by the microwave generator 5 are guided into the dome 7, from where they reach the cooking chamber 2. For this purpose, a microwave distribution device in the form of a rotatable antenna 8 is located in the dome 7, by means of which the MW microwaves arriving from the microwave guide 6 are radiated. The rotating antenna 8 can be rotated by means of a motor, in particular a stepper motor 9, acting as an antenna motor, e.g., quasi-continuously in steps of 1°.

[0042] The stepper motor 9 is controllable by a control device 10, which is also connected to a leakage radiation measuring device in the form of a microwave sensor 11 and is configured to evaluate measurement data Sig generated by the microwave sensor 11. The microwave sensor 11 is arranged outside or behind the cooking chamber wall 3, specifically behind or near an opening 12 in the cooking chamber wall 3 that allows microwave leakage radiation LS to pass through. The intensity of the microwave leakage radiation LS typically changes over the course of one rotation of the rotating antenna 8, along with the field distribution of the microwaves MW in the cooking chamber 2.

[0043] Furthermore, an operating device 13 is coupled to the control device 10, which may have one or more operating elements and one or more display devices, e.g., in the form of a touch-sensitive screen. The control device 10 is configured to output one or more instructions or messages to a user on a display device of the operating device 13.

[0044] The control device 10 is also configured to detect a standstill of the activated rotating antenna 8 and subsequently trigger at least one action. The control device 10 thus also serves for this purpose as a data processing device or evaluation circuit. In particular, the control device 10 is configured to monitor the microwave leakage radiation LS measured by the microwave sensor 11 for angle-dependent recurring fluctuations in the rotating operation of the rotating antenna 8 during a feed of microwaves into the cooking chamber 2 and, if it detects an absence of such fluctuations, to trigger at least one action, e.g., to output a corresponding message to the operating device 13 and / or to send it to a mobile user terminal, etc.

[0045] Fig.2shows a curve of the strength of a microwave leakage radiation LS measured by means of the microwave sensor 11 when the rotating antenna 8 is rotating as well as when it is stationary in the form of a plot of measured values Sig of the microwave sensor 11 in mV against a time t in s.

[0046] After the start of microwave operation, the measurement curve shows alternating time periods M in which the rotating antenna 8 rotates uniformly and time periods S in which the rotating antenna 8 does not rotate. While the measurement signal Sig changes only slightly in the time periods S, strong fluctuations of the measurement signal Sig occur in the time periods M. The absence of such fluctuations thus indicates that the rotating antenna 8 is at a standstill.

[0047] Fig.3 shows an excerpt from the Fig.2shown measurement curve in the range of a time period M. The time period M comprises three consecutive full revolutions RP1, RP2 and RP3. Because the rotating antenna 8 rotates uniformly during the time period M, a point in time on the x-axis for a measured value corresponds to a respective angle of rotation of the rotating antenna 8. In the exemplary embodiment shown, a first maximum Max1, a minimum Min and a second maximum Max2 occur alternately in the signal curve or in the curve during a full revolution of the rotating antenna 8.

[0048] For example, the control device 10 can initially automatically identify the extreme values Max1, Min, Max2 from the curve during the first full revolutions RP1. The control device 10 can then monitor whether, with the rotation of the rotating antenna 8 activated, these extreme values Max1, Min, Max2 occur again or periodically in subsequent revolutions RP2 and RP3. In particular, it can also be monitored whether a minimum value interval (Min / Max delta) between Max1 and Min and / or a minimum value interval between Min and Max2 lies above a particular respective threshold value or not. This threshold value can, for example, be 20% of an average value of the respective minimum Min and maximum Max1, Max2.

[0049] It can therefore be checked by means of the control device 10 for the revolution RP1 whether Sig Max 1 − Sig Min ≥ 0 , 2 ⋅ Sig Max 1 + Sig Min / 2 and / or Sig Max 2 − Sig Min ≥ 0 , 2 ⋅ Sig Max 2 + Sig Min / 2 This is the case here during time period M, since it is estimated that 80 - 35 = 45 ≥ 0.2 · 57.5 = 11.5 or 120 - 35 = 85 ≥ 0.2 · 77.5 = 15.5 applies, while these boundary conditions are not met in time periods S. Similarly, a value difference between Max1 and Max2 can also be monitored.

[0050] If the control device 10 detects that the extreme values Max1, Min, Max2 do not occur again during subsequent revolutions RP2, RP3 or if one or both of the above distance conditions are not met, it triggers at least one action.

[0051] Of course, the present invention is not limited to the embodiment shown.

[0052] In general, "a", "an", etc. can be understood as a singular or a plural, in particular in the sense of "at least one" or "one or more", etc., as long as this is not explicitly excluded, e.g. by the expression "exactly one", etc.

[0053] A numerical value may also include the exact number stated as well as a usual tolerance range, as long as this is not explicitly excluded. List of reference symbols

[0054] 1Household microwave appliance 2Cooking chamber 3Cooking chamber wall 4Door 5Microwave generator 6Microwave guide 7Dome 8Rotating antenna 9Stepper motor 10Control device 11Microwave sensor 12Opening 13Operating device LSMicrowave leakage radiation MTime period in which the rotating antenna rotates Max1First maximum Max2Second maximum MinMinimum MWMicrowaves RP1First full rotation RP2Second full rotation RP3Third full rotation STime period in which the rotating antenna does not rotate SigMeasurement signal tTime

Claims

1. Method for detecting that a rotatable microwave distribution apparatus (8) of a household microwave appliance (1) is at a standstill, and in said method - while microwaves (MW) are being supplied into a cooking compartment (2) of the household microwave appliance (1), at least one microwave leakage radiation (LS) is monitored for angle-dependent recurring fluctuations (Max1, Min, Max2) and - if an absence of such fluctuations (Max1, Min, Max2) is detected, at least one action is triggered.

2. Method according to claim 1, in which at least one microwave distribution apparatus (8) is uniformly rotated in a circumferential manner and the microwave leakage radiation (LS) is monitored for periodically recurring fluctuations (Max1, Min, Max2).

3. Method according to claim 2, in which a periodically recurring sequence of at least one pattern (Max1, Min, Max2) is monitored in a curve of the microwave leakage radiation (LS).

4. Method according to claim 3, in which the microwave leakage radiation (LS) is monitored for a periodically recurring sequence of at least one minimum (Min) and at least one maximum (Max1, Max2) that have a predetermined minimum value gap with respect to one another.

5. Method according to one of claims 3 to 4, in which a cross correlation of a stored section of a curve of the microwave leakage radiation (LS) is continuously compared to a section of the curve that is currently received.

6. Method according to one of the preceding claims, in which the at least one microwave leakage radiation (LS) comprises multiple microwave leakage radiations (LS) that are measured at different leakage sites (12) and said microwave leakage radiations (LS) in each case are monitored for angle-dependent recurring fluctuations (Max1, Min, Max2).

7. Method according to one of the preceding claims, in which the at least one microwave leakage radiation (LS) comprises microwave leakage radiations (LS) that occur in an overlapping manner at multiple different leakage sites (12) and said microwave leakage radiation is monitored for angle-dependent recurring fluctuations (Max1, Min, Max2).

8. Method according to one of the preceding claims, in which at least one rotatable microwave distribution apparatus (8) comprises at least one rotary antenna and / or at least one wobbler.

9. Household microwave appliance (1) having - a cooking compartment (2), - at least one microwave generator (5) for generating microwaves (MW), and - at least one rotatable microwave distribution apparatus (8) for varying a field distribution of microwaves (MW) that are supplied into the cooking compartment (2), characterised in that the household microwave appliance (1) further - at least one leakage radiation measuring apparatus (11) for measuring microwave leakage radiation (LS) and - a data processing apparatus (10) that is configured so as to implement the method according to one of the preceding claims.

10. Household microwave appliance (1) according to claim 9, wherein the household microwave appliance (1) is a baking oven having a microwave functionality.