Determination of arc flash during microwave processing in household microwave equipment

Abstract

A method for identifying arcing within a processing chamber (2) of a household microwave appliance (1) during a microwave processing procedure, wherein the setpoint of at least one microwave operating parameter is varied during the method, wherein a measured value (LM) of leakage radiation is measured multiple times sequentially at the same setpoint of the at least one microwave operating parameter during the microwave processing procedure, and an arcing is identified when the fluctuation range (LMS) of the measured value (LM) measured at the same setpoint reaches or exceeds a predetermined fluctuation range (LMS thr). A household microwave appliance (1) has a microwave generator (5) for generating microwaves, a processing chamber (2) capable of being loaded by the generated microwaves, microwave detection devices (10, 11) for measuring microwave leakage radiation escaping from the processing chamber (2), and a data processing device (10) for identifying arcing by evaluating the microwave leakage radiation (LM) measured by the microwave leakage detection devices (10, 11), wherein the household microwave appliance (1) is configured to perform the method. This invention can be particularly advantageously applied to stand-alone microwave devices and ovens with microwave functionality, especially when the microwave detection device is equipped with a sniffing circuit.

Description

Technical Field

[0001] This invention relates to a method for determining arc flash during a microwave processing flow in a home microwave appliance, wherein the setpoint of at least one microwave operating parameter is varied during the process. The invention also relates to a method for operating a home microwave appliance. Furthermore, the invention relates to a home microwave appliance comprising a microwave generator for generating microwaves, a microwave processing chamber on which the generated microwaves can be loaded, and a data processing device for identifying arc flash, wherein the home microwave appliance is configured to perform at least one of the methods described above. This invention is particularly advantageously applicable to stand-alone microwave appliances and ovens with microwave functionality. Background Technology

[0002] Spark gap formation is a common problem in microwave equipment, especially when these devices are operating at low loads and high power levels and / or when using unsuitable plates or accessories.

[0003] When using a transformer to supply energy to the magnetron—a transformer that only accepts "maximum" or "off" power levels and therefore must be clock-controlled to reach intermediate power levels—a point electric field stronger than the air breakdown field (approximately 3 kV / mm) may appear between the metal components or attachments of the cooking appliance. This results in a spark gap, which ionizes the air (plasma). Due to the high conductivity of the plasma, a high current may now flow. The very high localized heating that occurs in this situation through ohmic losses can sensitively damage the attachments and / or the cooking chamber walls. For example, it may cause damage to the protective enamel layer of the cooking chamber walls, such as melting, or even burn holes in the cooking chamber walls or attachments, where previously loose parts may be firmly welded together, and so on. Furthermore, this creates the starting point for corrosion. However, in principle, this problem also exists in microwave generators equipped with inverters at high power levels.

[0004] Customers who operate cooking appliances incorrectly, such as by using baking pans at high microwave power levels or by using containers that are not microwave-safe, may inadvertently shorten the lifespan of the equipment and accessories, thereby negatively impacting after-sales service.

[0005] In order to identify arcing during the microwave processing of a home microwave device, JP 2009019796 A discloses a measurement method using a camera and microphone to detect the visual and audible effects of arcing.

[0006] EP 3 5 16 928 A1 discloses a method for determining arcing based on the presence of harmonics in the fundamental frequency of the fed microwave.

[0007] EP 2 880 963 A1 discloses how the scattering parameters of the fed microwaves can be used for this purpose.

[0008] EP 2 418 916 A1 and US 7 525 074 B disclose methods to minimize the risk of sparks by identifying the presence of metallic bodies in a cooking chamber based on impedance measurements.

[0009] EP 2 152 047 A1 discloses a safety device for detecting leaked radiation in a microwave-enabled cooking appliance, and a cooking appliance having such a safety device. The safety device includes at least one microwave sensor comprising a probe in which alternating current can be induced by leaked radiation, or the probe is adapted to tap off alternating current induced in other objects by leaked radiation. The sensor also includes a fuse through which the alternating current is conducted. Finally, the safety device includes means adapted to shut off the microwave source of the cooking appliance once the fuse is triggered.

[0010] EP 2 148 553 A1 discloses a method for monitoring microwave leakage. In the case of a cooking appliance, microwave leakage radiation emanating from the cooking chamber is detected by means of a microwave sensor device, and the change process of the microwave leakage radiation over time is stored. Subsequent evaluation of the stored microwave radiation values ​​may, in particular, include predicting the future temporal change process of the detected microwave radiation, and early signaling of expected exceedances of predetermined thresholds based on the predicted change process. A corresponding device for monitoring microwave leakage and a cooking appliance equipped with the device are also disclosed.

[0011] DE 2 029 559 A1 discloses a safety device for preventing radiation from escaping from a microwave device, wherein at least one microwave-responsive duct is arranged near the area where radiation may escape and is electrically connected to a control circuit of a controlled semiconductor diode, which is itself located in the feed circuit of a relay, the excitation of which causes the feed circuit of the microwave generator to be disconnected.

[0012] DE 195 37 755 A1 discloses a microwave oven, particularly for laboratory use, having a heating chamber surrounded by a housing, into which microwaves can be coupled and enter via a closable access opening. A microwave sensor is arranged in a gap region of the housing extending from the heating chamber, such that when microwave radiation exceeding a certain value enters and / or passes through the gap, the sensor activates the output of a warning signal or deactivates the microwave application to the heating chamber.

[0013] The drawbacks to date, in particular, are the need for cost-intensive hardware, such as cameras, microphones, or sophisticated HF measurement techniques, to detect the presence of sparks during microwave feeding. Summary of the Invention

[0014] The objective of this invention is to at least partially overcome the shortcomings of the prior art, and in particular to provide the possibility of reliably and with minimal equipment cost identifying arcing during microwave processing in home microwave devices.

[0015] This task is solved according to the features of the independent claim. Advantageous embodiments are the subject of the dependent claims, the description, and the drawings.

[0016] This task is solved by a method for determining arcing within the processing chamber of a household microwave appliance during a microwave processing procedure, wherein the setpoint of at least one microwave operating parameter is varied during the method.

[0017] -During the microwave processing procedure, microwave leakage radiation was measured multiple times sequentially at the same set value of at least one microwave operating parameter, and

[0018] - When the measured value of microwave leakage radiation, obtained from multiple measurements performed at the same set value of at least one microwave operating parameter, exceeds a pre-given fluctuation range, an arcing is identified.

[0019] The advantage of this method is that it allows for reliable detection of sparks occurring in the processing chamber, such as on and between the walls, accessories, and participating parts of the cookware. The technology is also very inexpensive to implement. The spark-prevention safety and protection features achieved in this way can extend the lifespan of cooking appliances and accessories and protect customers from damage caused by overheating areas due to arcing.

[0020] This method uses leakage radiation escaping outward through openings in the processing chamber walls, cable transmissions, etc., as a highly sensitive indicator of sparks occurring within the processing chamber. This is based on the finding that fly-through arcs represent interference with the dominant microwave field conditions (distribution, pattern, etc.) within the processing chamber, and therefore also represent leakage radiation dependent on that interference. Due to their partially chaotic nature, fly-through arcs cause very noticeable diffusion or fluctuations in measurements, which map the intensity of microwave leakage radiation.

[0021] For example, a microwave processing procedure can be initiated by the user or a cooking program. Microwaves are fed into the processing chamber of a household microwave appliance during the microwave processing procedure, typically to process items located in the processing chamber (such as cooking food).

[0022] A household microwave appliance can be a household microwave cooking appliance, such as a standalone microwave appliance or a microwave / oven combination, such as a microwave appliance with at least one additional radiant heater or an oven with microwave functionality. If a household microwave appliance is present, the processing room can also be referred to as a cooking room surrounded by cooking room walls.

[0023] Home microwave appliances typically include a microwave generator for producing microwaves and a processing chamber from which the generated microwaves can be applied. The processing chamber usually has a front loading opening that can be microwave-sealed by a door. The microwave generator can be a magnetron or a semiconductor-based microwave generator. The microwave generator can be clock-controlled or inverter-controlled. The microwave frequency can be, for example, in the range of 915 MHz or 2.45 GHz. The microwave generator can feed microwaves directly into the processing chamber or via a microwave duct. Furthermore, devices for distributing microwaves within the processing chamber may be present, such as a feed antenna (especially a rotatable feed antenna), a mode stirrer (“stirrer”), an oscillator, etc. The generation and introduction of microwaves into the processing chamber are well-known in principle and will not be discussed further here.

[0024] Leakage radiation escaping from the processing chamber during microwave operation or while the processing chamber is being microwave-loaded can be measured using at least one microwave detection device. This microwave detection device can be provided, for example, to detect microwave leakage radiation in the area of ​​a household microwave appliance between the processing chamber wall (also known as a cooking chamber wall or muffle oven) and the outer casing, but also to detect microwave leakage radiation at locations such as door seams.

[0025] Microwaves can be fed into the processing chamber by setting a specific setpoint from a set of multiple possible setpoints for at least one variable microwave operating parameter. Therefore, a corresponding set of multiple adjustable setpoints is assigned to each variable microwave operating parameter. During the microwave processing flow, at least some setpoints of at least one microwave operating parameter can be changed, particularly according to a predetermined rule or sequence, such as periodically. Microwave operating parameters can be understood in particular as operating parameters that, when changed, can significantly alter the power distribution or pattern profile of the microwaves in the processing chamber.

[0026] At least one microwave operating parameter may include exactly one microwave operating parameter or multiple microwave operating parameters.

[0027] The measured values ​​reflect the intensity of the leaked radiation, such as its power, energy, and amplitude. These measured values ​​can be electrical characteristic parameters generated in a microwave detection device due to microwave irradiation, such as voltage, or digital values ​​derived from them.

[0028] Microwave leakage radiation was measured repeatedly at the same set value for at least one microwave operating parameter or at the same combination of set values. In particular, measurements were taken at the same set value for all microwave operating parameters that significantly affect the microwave field distribution in the processing room (in the case of only one microwave operating parameter: at the same set value).

[0029] The fluctuation range is determined for at least one specific combination of setpoints because, under undisturbed conditions, the same microwave field distribution is produced in the processing chamber at the same setpoints with high reproducibility. However, this field distribution is significantly disturbed by spark formation. The fluctuation range is specifically determined for all combinations of setpoints used or set multiple times during the microwave processing procedure.

[0030] The “predefined fluctuation range” corresponds to a threshold or limit value. If the measured fluctuation range remains below the predefined fluctuation range, it is assumed that no spark is formed.

[0031] In one design, the at least one microwave operating parameter includes at least one microwave operating parameter from the group consisting of:

[0032] - The rotation angle of at least one rotating antenna,

[0033] -At least one mode of stirrer rotation angle

[0034] - Rotation angle of the turntable

[0035] - The power of the incident microwaves,

[0036] - The frequency of the incident microwave,

[0037] -The phase difference between microwaves incident at different feed points

[0038] - The power difference between microwaves incident through different feed points.

[0039] Different combinations of these microwave operating parameters can be set sequentially during the microwave processing flow according to pre-defined rules or schemes, such as periodically.

[0040] Microwave operating parameter "rotation angle" The settings for the rotating antenna can, for example, fall within the angle range of [0°; 180°] or [0°; 360°], with step sizes of 1°, 5°, or 10°.

[0041] The frequency f of the incident microwave can vary, for example, between 2.4 GHz and 2.5 GHz, in steps of 0.01 GHz.

[0042] In an exemplary variant, only the rotation angle of the antenna is rotated during microwave processing. The setpoint changes, for example, in ascending or descending angle steps (e.g., 0°, 10°, 20°, ...) or in other sequences (e.g., 0°, 30°, 20°, 60°, etc.). A "combination of setpoints" represents the setpoint itself—because only one microwave operating parameter changes here. For the corresponding setpoint for at least two repeated measurements (e.g., at least two measurements for angle 0°, at least two measurements for angle 10°, etc.), determine the corresponding fluctuation range and compare it with a pre-defined fluctuation range or threshold or measurement value.

[0043] In another exemplary variant, the rotation angle of the rotating antenna If the setpoints for the incident microwave frequency f and the setpoint for the incident microwave change during microwave processing operation, the intensity of the leakage radiation is measured multiple times for multiple, and in particular all, combinations of setpoints. For each combination, a corresponding fluctuation range is determined and compared with a pre-defined fluctuation range. These combinations may include, for example, all rotation angles traversed multiple times during microwave processing operation. And the paired set value of frequency f, for example, paired [ ; f]=[0°; 2.4GHz], [10°; 2.4GHz], ....., [0°; 2.41GHz], ..., [350°; 2.5GHz], etc.

[0044] In one design, the measurement of microwave leakage radiation is made or recorded by means of a sniffing line arranged outside the processing chamber and representing a component of a microwave detection device. The “sniffing line” should be understood in particular as a conductive line in which alternating current can be induced by microwaves. The intensity of the induced alternating current (e.g., power, amplitude, etc.) represents the intensity of the microwave leakage radiation that caused the induction. The sniffing line is connected to an evaluation circuit for microwave leakage radiation, which converts the alternating current into a corresponding measurement (“leakage radiation measurement”), for example, into a voltage. The evaluation circuit may be connected to one or more sniffing lines. Providing a sniffing line offers the advantage that the sniffing line can be wired in a particularly variable manner within the device, for example because one end is functionally connected to the evaluation circuit, while the other end is a freely locatable end. Sniffing lines can be, for example, wires, cables, conductor tracks laid on a substrate, in which alternating current can be induced by microwaves generated by a microwave generator.

[0045] In one design, the fluctuation range is the difference between the minimum and maximum values ​​of a set of multiple (i.e. at least two) leakage radiation measurements taken at the same set value of the at least one microwave operating parameter.

[0046] In one design, the fluctuation range is calculated based on the standard deviation of a set of multiple leakage radiation measurements taken at the same set value of the at least one microwave operating parameter.

[0047] In one design, a flyby is identified when exactly one combination of the set values ​​of the at least one microwave operating parameter reaches or exceeds a pre-defined fluctuation range. This advantageously provides particularly sensitive identification of flybys.

[0048] In one design, a fly-through arc is identified when multiple combinations of setpoints for at least one microwave operating parameter reach or exceed the fluctuation range. This provides the advantage of particularly robust identification of fly-through arcs. Therefore, in this design, different combinations of setpoints are repeatedly set during the microwave processing flow, and corresponding fluctuation ranges are determined and compared with pre-defined fluctuation ranges. The pre-defined fluctuation ranges for at least two different combinations of setpoints can be the same or different.

[0049] In one design, a predetermined fluctuation range is fixedly set for the microwave processing flow. For example, the predetermined fluctuation range can be determined experimentally. The predetermined fluctuation range can be the same for all combinations of set values, or it can be different for different combinations of set values, for example, different for different rotation angles set for a rotating antenna.

[0050] In one design, the pre-defined fluctuation range is dynamically adapted based on measurements taken or recorded during the microwave processing flow. This enables the particularly reliable identification of arc flashes.

[0051] In one design, the pre-defined fluctuation range for a specific combination of microwave operating parameters corresponds to the product of the average fluctuation range determined for multiple—especially all—setpoint combinations and a factor A, where A > 1. This makes dynamic adaptation to the pre-defined fluctuation range particularly simple. The factor A can be determined, for example, empirically or experimentally. For instance, the pre-defined fluctuation range LMS_thr can be determined as follows: ,in The value of the range of fluctuation (LMS) of the leakage radiation measurement (LM) for multiple setpoint combinations is given by A, where A > 1. Factor A does not need to be an integer. Factor A can be the same or different for different setpoint combinations.

[0052] In one design, the method is executed or initiated only after the microwave processing has begun, specifically after a predetermined duration following the startup of the microwave generator. This takes into account that the microwave generator has not yet reached a stable oscillation state during its heating phase, and that measurements may be significantly dispersed even without sparks during this initial period. In an extension, the method is performed five to ten seconds after the start of the microwave processing, because thereafter the fluctuations in microwave leakage power or leakage radiation measurements have significantly decreased or become negligible due to the heating effect of the microwave generator.

[0053] This task is also addressed by a method for operating home microwave equipment, wherein at least one action is triggered when a flyby arc is identified using the method described above. This method can be designed similarly to the method used to determine flyby arcs and has the same advantages.

[0054] In one design, the at least one action includes reducing the incident microwave power for all set values ​​of the microwave operating parameters. This can be achieved by gradually reducing the microwave power incident into the processing chamber. Once the microwave power is reduced to a level that no longer reaches the breakdown field strength, spark generation immediately ceases, reflected in a reduced fluctuation range. The microwave power can therefore be gradually reduced until the measured fluctuation range falls below a predetermined limit or a predetermined fluctuation range, particularly for all combinations of microwave operating parameter set values. The fluctuation range can be recalculated after each reduction.

[0055] In one design, the at least one action includes reducing the incident microwave power only for combinations of setpoints for microwave operating parameters that exceed a predetermined fluctuation range. This allows the incident microwave power to be maintained for other combinations of microwave operating parameters that do not exceed the predetermined fluctuation range, supporting high power input to microwave-processed items such as water, cooking food, etc.

[0056] In one design, the at least one action includes feeding microwave radiation into the processing chamber briefly over time for a combination of setpoints for microwave operating parameters with a high fluctuation range, and / or feeding microwave radiation into the processing chamber for a longer time over a combination of setpoints for microwave operating parameters with a small fluctuation range. This can also prevent sparking over time and significantly reduce the duration of microwave action. The brief feeding of microwave radiation may also include a pause in the feeding.

[0057] In one extension, the at least one action includes outputting user prompts to the user via the home microwave device. For example, the user may be prompted to locate an accessory in a different manner or to reduce the set microwave power.

[0058] This task is also addressed by a home microwave device having a microwave generator for generating microwaves, a processing chamber that can be loaded by the generated microwaves, a microwave detection device for measuring microwave leakage radiation escaping from the processing chamber, and a data processing device for identifying arcing by evaluating the microwave leakage radiation measured by the microwave leakage sensor, wherein the home microwave device is configured to perform at least one of the methods described above. The home microwave device can be designed similarly to the methods described above, or vice versa, and has the same advantages.

[0059] Thus, for example, the aforementioned home microwave equipment can have a microwave detection device equipped with at least one sniffing line. This sniffing line is used to detect microwave leakage radiation outside the processing room, and the sniffing line has at least one conductive line (antenna or "sniffing line")—in which alternating current can be induced by microwaves—and an evaluation circuit connected to the at least one sniffing line, the evaluation circuit being configured to determine the alternating current induced in the at least one sniffing line. This allows the sniffing line to have a long length and to be wired in a variety of different ways within the home microwave equipment. It also allows monitoring of microwave leakage in large areas of the home microwave equipment outside the processing room, thereby reducing the number of detection devices and / or their components compared to microwave detection devices that only measure at points. Therefore, a particularly reliable and cost-effective structure can be achieved. Another advantage is that the evaluation circuit can be arranged away from the radiation leakage source in areas of the home microwave equipment that are rarely subjected to thermal, chemical, and / or electromagnetic effects. Conversely, the sniffing line is significantly more durable and can also pass through areas subjected to thermal and chemical effects (e.g., heat and / or moisture) without problems. Another advantage is the ability to identify microwave leakage with high sensitivity. At least one sniffing line can be a dedicated sniffing line in the sense that it has no additional signal conduction (i.e., no conduction of current and / or data) function, and in particular, no other function. Such a (“pure”) sniffing line is laid solely for the purpose of detecting microwave-based induction. Alternatively or additionally, the at least one sniffing line may additionally have at least one signal conduction function (“combined sniffing line”).

[0060] The evaluation circuit is specifically configured to determine the intensity of the microwave induced current induced in the at least one sniffing line, which is a measure of the leakage radiation intensity. The evaluation circuit may have one or more electrical and / or electronic components and / or functional units, such as capacitors, resistors, processors (e.g., microcontrollers, ASICs, FPGAs), rectifiers, A / D converters, etc.

[0061] In one extension, the evaluation circuit can be connected precisely to a single sniffing line and thus evaluate only that sniffing line or determine the intensity of the microwave induced current in that sniffing line. In an alternative extension, the evaluation circuit is connected to multiple sniffing lines. In this case, the evaluation circuit can evaluate multiple sniffing lines together. This joint evaluation makes it possible to provide a particularly simple and inexpensive detection device. The covered or detectable detection area can also be further expanded, allowing the evaluation unit to respond even faster in the event of a possible leak. In one extension, multiple sniffing lines can be electrically converged and connected to the evaluation circuit at a common node. Alternatively, multiple sniffing lines can be evaluated individually, for example, time-separated or in parallel, using the same evaluation circuit. Individual evaluation allows for improved localization of radiation leakage sources.

[0062] Alternatively, the home microwave device may have multiple evaluation circuits, each connected, for example, to a sniffing line. These evaluation circuits may be distributed across the home microwave device.

[0063] In one design, the evaluation circuit is connected to the at least one sniffing line via at least one conductor track on the printed circuit board of the control device. This achieves a particularly simple, space-saving, and robust connection between the evaluation circuit and the at least one conductor track. Specifically, the sniffing line is guided to the circuit board and connected there to the conductor track, for example, via solder points, clamps, plugs, etc.

[0064] In designs particularly advantageous to combined sniffing circuits, the evaluation circuit is connected to the at least one sniffing circuit via a coupling capacitor. This achieves the advantage of electrical isolation between the sniffing circuit and the evaluation circuit, while allowing AC signals to be transmitted through the coupling capacitor. Therefore, DC voltage isolation between the sniffing circuit and the evaluation circuit is achieved via the coupling capacitor. Specifically, one terminal of the coupling capacitor is electrically connected to at least one sniffing circuit and the other terminal is electrically connected to the evaluation circuit. The coupling capacitor may also represent a portion of the evaluation circuit.

[0065] In one design, the coupling capacitor is a component of a high-pass filter. The advantage of this is that relatively high-frequency microwave-induced AC (which may have a frequency within the microwave frequency range) is allowed to reach the evaluation circuit, while low-frequency AC, such as that typically used to supply current to power devices using AC (e.g., a mains frequency of 50 Hz), is blocked. This prevents the measurement signal of microwave leakage radiation from being interfered with by lower-frequency currents in the combined sniffing circuit, which in turn improves evaluation accuracy.

[0066] In one extension, the coupling capacitor, together with an ohmic resistor, particularly grounded, forms a high-pass filter. The resistor can be a component of the evaluation circuit, such as the input resistor of the evaluation circuit.

[0067] In one design, the high-pass filter additionally has a resistor connected to the coupling capacitor, specifically an input resistor, and the coupling capacitor has a capacitance of size C (Equation 1):

[0068]

[0069] Where R corresponds to the resistance value of the ohm resistor, f u This corresponds to the lower cutoff frequency of the high-pass filter.

[0070] This formula originates from a complex transfer function. This transfer function reflects the voltage transferred by the high-pass filter. With the voltage applied to the monitored or tapped sniffing line The ratio (Equation 2):

[0071]

[0072] Since we are only interested in the absolute value of the transfer function (not its phase), we arrive at (Equation 3):

[0073]

[0074] Regarding the selection and size setting of the coupling capacitor C, assuming the lower cutoff frequency f of the obtained high-pass filter... u The lower limit frequency f must be at least as high as required by the signal under test (typical microwave frequencies for measurement signals are 915 MHz or 2.45 GHz). u Set to enable the transmitted voltage Raw signal only amplitude Or approximately 70.7% or the original signal This attenuation factor is applied. From this, the absolute value of the transfer function can be derived.

[0075] .

[0076] According to Equation 1, the favorable value of the capacitance C of the coupling capacitor can be obtained.

[0077] If the sniffing line is connected to the evaluation circuitry, there is no need to electrically isolate the sniffing line from the evaluation circuitry via a coupling capacitor. Alternatively, a high-pass filter can be omitted. Or, the sniffing line can also be connected via a coupling capacitor and / or a high-pass filter.

[0078] In one design, at least one sniffing line has a length of at least 800 mm, particularly at least 1000 mm, particularly at least 1500 mm, particularly at least 2000 mm. The advantage of such a long length is that as much / larger area inside the housing of a household microwave device as possible can be covered by the sniffing line, and thus localized sources of radiation leakage can be sensed or detected with a small number of sniffing lines.

[0079] Because the leaking radiation source is not only locally distributed but also often radiates with varying intensities over time (e.g., due to the movement of the feed antenna, pattern stirrer, and / or turntable causing different pattern distributions in the processing chamber over time), it is advantageous for the sniffing line to have local and, if necessary, temporally integrated characteristics. The superposition of the different incident microwave signals then produces a summed signal applied to the microwave sensor. The longer the sniffing line, the stronger this superposition. Attached Figure Description

[0080] The above-described features, characteristics, and advantages of the present invention, as well as the ways in which they are implemented, will become clearer and easier to understand in conjunction with the illustrative description of the following embodiments, which will be explained in more detail with reference to the accompanying drawings.

[0081] Figure 1 A household microwave device is shown in sectional view from the side.

[0082] Figure 2 Shown in top view Figure 1 Possible evaluation circuitry for home microwave devices;

[0083] Figure 3 The graph shows the relationship between the measurement of leakage radiation without the formation of a spark and the rotation angle of the rotating antenna;

[0084] Figure 4 The graph shows the relationship between the measurement of leakage radiation in the case of spark formation and the rotation angle of the rotating antenna;

[0085] Figure 5 The diagram shows the cases with and without spark formation. Figure 3 and Figure 4 The graph shows the relationship between the fluctuation range of the leakage radiation measurement value and the rotation angle of the rotating antenna. Detailed Implementation

[0086] Figure 1 A sketch of a household microwave appliance 1 with a processing chamber in the form of a cooking chamber 2 is shown in sectional view from the side. The household microwave appliance 1 may be, for example, an oven with microwave functionality.

[0087] The cooking chamber 2 is surrounded by a cooking chamber wall or a muffle oven 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 processing items located in the cooking chamber 2 (not shown), and may also have additional heating elements, such as one or more resistance heating elements (not shown), if necessary. Microwaves generated by the microwave generator 5 are fed into the cooking chamber 2 via a microwave duct 5a by means of a rotating antenna 5b, which can be rotated about the longitudinal axis of the microwave duct 5a by a stepper motor (not shown).

[0088] In addition, there is an operating device 6, which may have one or more operating elements and / or a display device, such as in the form of a touch-sensitive display screen.

[0089] Attached to or replacing the rotating antenna 5b, the household microwave appliance 1 includes a turntable 7 located in the cooking chamber 2, which can be rotated by means of a motor 8 disposed outside the cooking chamber 2. The household microwave appliance 1 or its controllable components 5, 6, 8 can be operated or actuated by means of a central control unit 9 (also known as an "equipment controller").

[0090] Evaluation circuit 10 is integrated into control device 9 and connected to combined sniffing circuit 11. Here, combined sniffing circuit 11 is an electrical circuit from control device 9 to motor 8 to supply current to motor 8 and / or transmit data to motor 8 to control the motor. Combined sniffing circuit 11 is also suitable for inducing alternating current through microwaves. Evaluation circuit 10 is configured to determine the alternating current induced in combined sniffing circuit 11. Evaluation circuit 10 and combined sniffing circuit 11 form detection devices 10, 11 for detecting microwave leakage radiation outside the cooking chamber 2, particularly microwave leakage radiation in the gap between muffle oven 3 and the housing 12 of household microwave equipment 1. Combined sniffing circuit 11 thus has a dual function: firstly, for current and / or data transmission between control device 9 and motor 8, and secondly, as a "sensor circuit" for detecting microwave leakage radiation. For this purpose, combined sniffing circuit 11 can, for example, be arranged around an opening in muffle oven 3 through which the drive shaft of motor 8 leads to turntable 7. Additionally or alternatively, the combined sniffing line 11 may have at least one corrugated or zigzag-shaped extension segment, which extends, for example, via the assembly joint of the muffle furnace 3, additional openings, etc.

[0091] Attached to or replacing the combined sniffing circuit 11, the home microwave device 1 may have at least one pure sniffing circuit 13 connected to the evaluation circuit 10, such as a simple wire or a simple cable, which is only configured to serve as a sensor circuit.

[0092] The combined sniffing line 11 and / or the pure sniffing line 13 may have a length of at least 800 mm, particularly at least 1000 mm, particularly at least 1500 mm, particularly at least 2000 mm.

[0093] Figure 2 A top view shows a sketch of an evaluation circuit 10 integrated into the control device 9, which has some additional components present on the control device 9. Multiple electrical lines 15 may lead to a printed circuit board 14 of the control device 9. The lines 15 may be combined sniffing lines 11 and / or pure sniffing lines 13, the combined sniffing lines 11 being connected at their other ends to functional units of the home microwave device 1, such as power supplies and / or sensors.

[0094] The circuit 15 connects to the printed circuit board 14 at a connection point 16, such as a terminal, and merges there into the corresponding conductor track 17 of the printed circuit board 14. In the illustrated embodiment, only one combined sniffer line 11 is shown as being connected, purely exemplary, to an evaluation circuit 10 arranged on the printed circuit board 14, which in turn is connected to a processor 18 of the control device 9, such as a microcontroller, ASIC, or FPGA.

[0095] Specifically, the evaluation circuit 10 is connected here via a conductor rail 17 connected to the combined sniffing line 11 via a coupling capacitor 19, which causes DC voltage isolation between the evaluation circuit 10 and the combined sniffing line 11.

[0096] As shown in enlarged section A, the evaluation circuit 10 has at least one ohmic resistor 20, which is connected on one side to a terminal connected to the processor 18 and on the other side to a pre-given reference potential or ground. The coupling capacitor 19 and the resistor 20 form high-pass filters 19, 20 for signals from the combined sniffing line 11.

[0097] Here, the coupling capacitor 19 advantageously has a size of

[0098]

[0099] The capacitance value C, where R is the resistance value of resistor 20, f u Let f be the desired lower cutoff frequency for high-pass filters 19 and 20. u The setting is chosen so that only the microwave-induced voltage component is actually allowed to pass through.

[0100] The evaluation circuit 10 may output an analog signal, for example, to the processor 18 for evaluation (e.g., to an analog input of the microcontroller). However, the evaluation circuit 10 may also have other components or parts (not shown), such as an A / D converter, an operational amplifier, etc.

[0101] The control device 9 can be configured to detect spark formation in the cooking chamber 2 during microwave operation based on the intensity of the microwave-induced alternating current in the combined sniffing circuit 11, the intensity of which is represented by a measurement / output signal or measurement value from the evaluation circuit 10 and, if necessary, trigger at least one corresponding action, such as reducing the power of the microwave generator 5, outputting a prompt to the user, etc.

[0102] Figure 3 The following figures show the leakage radiation measurement LM in mV and the rotation angle of the rotating antenna 5b in degrees during microwave processing with a water load of 600W introduced into cooking chamber 2 without the formation of sparks. The relationship diagram, wherein the leakage radiation measurement value represents the intensity of the leakage radiation and is measured by the evaluation circuit 10, is output by the evaluation circuit 10, for example.

[0103] It is assumed here that the microwave field distribution in cooking chamber 2 is set solely by rotating the rotating antenna 5b. At least one relevant variable microwave operating parameter therefore only includes the rotation angle of the rotating antenna 5b here. The rotation angle can be set within the range [0°; 360°], for example in steps of 1°, 5°, or 10°. The rotating antenna 5b serves to equalize the microwave power introduced into the cooked food (not shown). During the rotation of the rotating antenna 5b, the microwave field in the cooking chamber 2 changes periodically and may cause arcing under unfavorable but unpredictable conditions and at specific rotation angles.

[0104] However, alternatively or supplementarily, other variable microwave operating parameters can usually be used, such as

[0105] - The rotation angle of at least one mode stirrer (not shown),

[0106] - Rotation angle of turntable (7),

[0107] - The power of the incident microwaves,

[0108] - The frequency of the incident microwave,

[0109] - The phase between microwaves incident through different feed points (not shown).

[0110] -wait.

[0111] This graph shows that ten complete rotations of the rotating antenna 5b can reproduce the leakage radiation measurement LM very well, because it generates very similar measurements (within the range of measurement accuracy) at each rotation angle. Therefore, the rotation angle... The fluctuation range of all settings is very small (LMS), such as for angle values. =100° is shown schematically (see also) Figure 5 ).

[0112] Figure 4 The following figures show the leakage radiation measurement LM in mV and the rotation angle of the rotating antenna 5b in degrees during microwave processing with a water load of 600W introduced into cooking chamber 2 and an additional metal baking pan (not shown). The relationship diagram shows that the leakage radiation measurements represent the intensity of the leakage radiation. Due to the inserted baking pan, microwave-based sparks will now form. The fluctuation range LMS is much higher than... Figure 3 The example shown is for the case without a baking tray, as exemplarily for... =50° as shown.

[0113] Here, for example, with a microwave-enabled oven, it is shown that starting with a microwave power of 360W, the baking pan in cooking chamber 2 promotes spark formation, particularly at the point of contact with the rack or pull-out device. In this case, flying arcs are frequently seen and heard throughout the microwave operation. The diagram shown reflects this: due to the random components at the time of spark generation—even nanoscale effects and fluctuations are sufficient to alter the intensity and spatial occurrence of the spark—the same rotation angle is now observed at the rotating antenna 5b. The field distribution is no longer the same at different times. This change in "spark characteristics" can be directly observed in leakage rate or leakage radiation measurements. These leakage rate or leakage radiation measurements are now different at rotation angles. Under the same conditions, significantly different settings are used each time the rotating antenna 5b is rotated again.

[0114] Figure 5 It shows the target from Figure 3 and Figure 4 The leakage radiation measurement value LM is in mV. The fluctuation range of the leakage radiation measurement value LM is LMS and the rotation angle of the rotating antenna 5b is in degrees. The relationship diagram shows that each leakage radiation measurement is for a specific rotation angle. Calculated from the standard deviation of the leakage radiation measurement LM. The antenna revolutions used for evaluation are at least two, but may advantageously be more than two.

[0115] from Figure 5 It can automatically determine whether sparks or arcing occur in cooking chamber 2. Possible criteria for spark formation may include, for example:

[0116] - The fluctuation range of the leakage radiation measurement (LMS) exceeds the predefined fluctuation range or limit value (LMS_thr) at least once, specifically for the rotation angle. Specific setting value or specific rotation angle range for this range :[ - / 2; + / 2];

[0117] -Regarding rotation angle If there is more than one set value or more than one rotation angle range, the fluctuation range of the leakage radiation measurement value LMS exceeds the limit value LMS_thr.

[0118] The limit value LMS_thr (shown in the current case, for example, when LMS = 40mV) can be a fixed, specific value, or it can be dynamically derived from the measured value. For example, the limit value LMS_thr can be calculated based on the average value of LMS across all fluctuation ranges.

[0119] If the above criteria are met successively for more than one measurement cycle (i.e., a complete run of the microwave operating parameter setpoint combination, here: a complete antenna rotation), spark formation or arcing can also be identified with particular reliability. This is especially advantageous because measurement inaccuracies can provide erroneous results, particularly at steep edges in the process of measurement value variation (see, for example, [reference needed]). Figure 3 Within the angle range =[180°; 210°] (in the middle). However, generally speaking, Figure 3 and Figure 4 Direct comparisons show that the formation of a spark or the presence of a fly-by arc can be determined with great reliability.

[0120] To further improve reliability in determining spark formation or arcing—especially to eliminate so-called "false alarms"—the leakage radiation measurement LM or its variation process (e.g., ...) is analyzed. Figure 3 and Figure 4 (As shown) can be prepared by data processing. For example, the leakage radiation measurement value LM from the first few seconds (e.g., five to ten seconds) of microwave operation cannot be used because the magnetron 5 has not yet reached a stable oscillation state during its heating phase, so the leakage radiation measurement value LM will diffuse even if no spark is formed when necessary.

[0121] The leakage radiation measurement value LM can also be curve adapted (e.g., by interpolation) and / or smoothed.

[0122] If spark formation or arcing is detected, the countermeasure could be to gradually reduce the microwave power incident on the cooking chamber 2. Once the microwave power is reduced to a level that no longer reaches the breakdown field strength, spark generation immediately ceases, which can be detected in the drastically reduced fluctuation range (LMS).

[0123] Alternatively or additionally, the angular range with an increased fluctuation range (LMS) can be traversed or ignored more quickly by means of a stepper motor controlling the rotating antenna 5b via the control device 9. Within the angular range with a small fluctuation range (LMS), the rotating antenna 5b can rotate more slowly. Therefore, the time window for spark occurrence can be significantly reduced, thereby significantly reducing processing or cooking time. Figure 5 In the middle, it can target Figure 4 The scenario described herein exemplarily determines the angular range under both slow and fast rotation speeds of the rotating antenna 5b:

[0124] - For rapid rotation within the angle range [10°; 20°], [45°; 55°], [100°; 110°], [140°; 170°], [240°; 300°];

[0125] - Slow rotation for angle ranges of [20°; 45°], [60°; 95°], [110°; 135°], [180°; 230°], [310°; 360°].

[0126] As a countermeasure, an interaction can be initiated between the home microwave device and the user, prompting the user to remove accessories, reposition accessories, or reduce the microwave power setting during the interaction.

[0127] Of course, the present invention is not limited to the embodiments shown.

[0128] Generally speaking, "one" can be understood as singular or plural, especially in the sense of "at least one" or "one or more", as long as it is not explicitly excluded, such as by expressing "exactly one".

[0129] Numerical specifications may also include the exact numbers specified, as well as the usual tolerance range, provided that this is not explicitly excluded.

[0130] List of reference numerals

[0131] 1. Home microwave equipment

[0132] 2. Cooking space

[0133] 3 Muffle furnace

[0134] 4 doors

[0135] 5. Microwave generator

[0136] 5a Microwave conduit

[0137] 5b Rotating Antenna

[0138] 6. Operating device

[0139] 7 turntables

[0140] 8 motors

[0141] 9. Control device

[0142] 10 Evaluation Circuit

[0143] 11 Combined sniffing circuits

[0144] 12. Outer shell

[0145] 13 Pure sniffing circuits

[0146] 14 Printed Circuit Boards

[0147] 15. Power lines

[0148] 16 Connection Points

[0149] 17 Conductor Tracks

[0150] 18 processors

[0151] 19 Coupling capacitors

[0152] 20 resistor

[0153] Section A

[0154] C Capacitance value

[0155] LM leakage radiation measurement value

[0156] Fluctuation range of LMS leakage radiation measurements

[0157] LMS_thr is a predefined fluctuation range / limit value.

[0158] R resistance value

[0159] The rotation angle of the rotating antenna.

Claims

1. A method for determining arcing within a processing chamber (2) of a household microwave appliance (1) during a microwave processing procedure, wherein at least one microwave operating parameter ( The set value of ) is variable, where in this method - During the microwave processing procedure, at least one microwave operating parameter ( The leakage radiation (LM) was measured multiple times under the same set value, and - When the fluctuation range (LMS) of the measured value (LM) measured under the same set value reaches or exceeds the pre-given fluctuation range (LMS_thr), a fly-by arc is identified.

2. The method according to claim 1, wherein the measured value (LM) of the leakage radiation is measured by means of sniffing lines (11, 13) arranged outside the processing chamber (2).

3. The method according to any one of claims 1 to 2, wherein the fluctuation range (LMS) is the difference between the minimum and maximum values ​​of the measured values ​​(LM) measured at the same set value of the at least one microwave operating parameter.

4. The method according to any one of claims 1 to 2, wherein the fluctuation range (LMS) is the standard deviation of a measurement (LM) measured at the same set value of the at least one microwave operating parameter.

5. The method according to any one of claims 1 to 2, wherein when the at least one microwave operating parameter ( When a combination of the set values ​​of the ) reaches or exceeds the fluctuation range (LMS), a flying arc is identified.

6. The method according to any one of claims 1 to 2, wherein when the at least one microwave operating parameter ( When multiple combinations of the set values ​​of the signal reach or exceed the fluctuation range (LMS), a flying arc is identified.

7. The method according to any one of claims 1 to 2, wherein the predetermined fluctuation range (LMS_thr) is fixedly pre-given for the microwave processing flow.

8. The method according to any one of claims 1 to 2, wherein the pre-given fluctuation range (LMS_thr) is dynamically adapted based on the measured value (LM).

9. The method according to claim 8, wherein the microwave operating parameters are ( The pre-defined fluctuation range (LMS_thr) for a specific setpoint combination corresponds to the product of the average fluctuation range determined for multiple setpoint combinations and factor A, where A>

1.

10. The method according to any one of claims 1 to 2, wherein the at least one microwave operating parameter ( Includes at least one microwave operating parameter from the following groups. - Rotation angle of at least one rotating antenna (5b) ), -At least one mode of stirrer rotation angle - Rotation angle of turntable (7), - The power of the incident microwaves, - The frequency of the incident microwave, - The phase between microwaves incident through different feed points.

11. The method according to any one of claims 1 to 2, wherein the method is performed after a predetermined duration following the start of the microwave processing procedure.

12. A method for operating a home microwave device (1), wherein at least one action is triggered when an arcing is detected by means of the method according to any one of claims 1 to 11.

13. The method of claim 12, wherein the at least one action includes targeting the at least one microwave operating parameter ( All settings reduce the incident microwave power.

14. The method of claim 12, wherein the at least one action includes actions only for the at least one microwave operating parameter ( The incident microwave power is reduced by exceeding the preset fluctuation range (LMS_thr) setting.

15. A home microwave device (1) having a microwave generator (5) for generating microwaves, a processing chamber (2) capable of being loaded by the generated microwaves, a microwave detection device for measuring microwave leakage radiation escaping from the processing chamber (2), and a data processing device for identifying arcing by evaluating the microwave leakage radiation (LM) measured by the microwave detection device, wherein the home microwave device (1) is configured to perform the method according to any one of claims 1 to 14.

Images