DE102019207978A1 - Household microwave device with detection device for detecting microwave leakage radiation - Google Patents

Abstract

A household microwave appliance (1) has a cooking space (2) and at least one detection device (10, 11) for detecting microwave leakage radiation outside the cooking space (2), the detection device (10, 11) having at least one antenna line (11) , in which alternating currents can be induced by microwaves, and has an evaluation circuit (10) connected to the at least one antenna line (11) which is designed to determine alternating currents induced in the at least one antenna line (11), and wherein the at least one antenna line ( 11) has at least one other function. The invention is particularly advantageously applicable to baking ovens with a microwave function and stand-alone microwave ovens.

Description

The invention relates to a household microwave appliance, having a cooking space and at least one detection device for detecting microwave leakage radiation outside the cooking space, the detection device having at least one antenna line in which alternating currents can be induced by microwaves and an evaluation circuit connected to the at least one antenna line, which is designed to determine alternating currents induced in the at least one antenna line. The invention also relates to a method for operating the household microwave appliance. The invention is particularly advantageously applicable to baking ovens with a microwave function and stand-alone microwave ovens.

EP 2 152 047 A1 discloses a safety device for detecting leakage radiation in a cooking device with a microwave function and a cooking device with such a safety device. The safety device comprises at least one microwave sensor which comprises a probe in which an alternating current can be induced by leakage radiation, or which is suitable for tapping off alternating currents that are induced in further objects by leakage radiation. The sensor also includes a fuse through which the alternating current is passed. Finally, the safety device comprises a device which is suitable for switching off a microwave source of the cooking appliance as soon as the fuse trips.

EP 2 148 553 A1 discloses methods for microwave leakage monitoring. In the case of a cooking appliance, a microwave leakage radiation emerging from the cooking space is detected by means of a microwave sensor device and its course over time is stored. A subsequent evaluation of the stored microwave radiation values can include, in particular, a prognosis of the future course of the detected microwave radiation over time and the early signaling of a predetermined threshold value being exceeded on the basis of the prognosticated course. A corresponding device for microwave leakage monitoring and a cooking device equipped with such a device are also disclosed.

DE 2 029 559 A1 discloses a safety device against the escape of radiation from microwave devices, whereby at least one gas tube responding to microwaves is used, which is arranged in the vicinity of the zone of a possible radiation exit and is electrically connected to the control circuit of a controlled semiconductor diode, which in turn is in the supply circuit of a relay, the excitation of which causes the electrical supply circuit of a microwave generator to open.

DE 195 37 755 A1 discloses a microwave oven, in particular for a laboratory, with a heating chamber which is surrounded by a housing and into which microwaves can be coupled and which is accessible through a closable access opening. In the area of a gap in the housing emanating from the heating chamber, a microwave sensor is arranged in such a way that when microwave radiation exceeding a certain value enters and / or passes through the gap, the sensor activates a warning signal or switches off the microwave exposure to the heating chamber .

It is the object of the present invention to at least partially overcome the disadvantages of the prior art and, in particular, to provide an improved possibility of detecting a leakage of microwaves emerging from a cooking space of a domestic microwave appliance.

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

• - die Detektionseinrichtung mindestens eine elektrisch leitfähige Leitung („Antennenleitung“), in der durch Mikrowellen Wechselströme induzierbar sind, und eine mit der mindestens einen Antennenleitung verbundene Auswerteschaltung, die zur Bestimmung von in der mindestens einen Antennenleitung induzierten Wechselströmen ausgebildet ist, aufweist und wobei
• - die mindestens eine Antennenleitung mindestens eine weitere Funktion aufweist.

Dieses Haushalts-Mikrowellengerät weist den Vorteil auf, dass keine gesonderte elektrische Leitung benötigt wird, um eine Leckage von Mikrowellen zu erfassen. Dies wiederum ermöglicht vorteilhafterweise einen besonders kostengünstigen Aufbau. Darüber hinaus kann die Antennenleitung eine große Länge aufweisen und vielfältig in dem Haushalts-Mikrowellengerät verlegt sein. Dadurch wird der Vorteil erreicht, dass mit einer Antennenleitung große Bereiche des Haushalts-Mikrowellengeräts außerhalb des Garraums auf Mikrowellen-Leckage überwacht werden können, wodurch die Zahl der Detektionseinrichtungen und/oder ihrer Komponenten im Vergleich zu nur punktuell messenden Mikrowellen-Detektionseinrichtungen verringert werden kann. Ermöglicht wird somit ein besonders zuverlässiger und kostengünstiger Aufbau. Ein weiterer Vorteil besteht darin, dass die Auswerteschaltung ortsfern von Leckstrahlungsherden in thermisch, chemisch und/oder elektromagnetisch wenig beanspruchten Bereichen des Haushalts-Mikrowellengeräts anordenbar ist. Die Antennenleitungen sind dagegen merklich widerstandsfähiger und können problemlos auch thermisch und chemisch beanspruchte (z.B. heiße und/oder feuchte) Bereiche durchlaufen. Noch ein Vorteil besteht darin, dass Mikrowellen-Leckagen mit hoher Empfindlichkeit erkennbar sind. Dadurch können auch erst noch drohende hohe Mikrowellen-Leckagen im Gerät frühzeitig erkannt werden. Dies wiederum bewirkt eine Verringerung eines Gefährdungspotentials für Nutzer und Kundendienst-Mitarbeiter. Darüber hinaus kann durch die frühzeitige Detektion einer Mikrowellen-Leckage ein Kundendiensteinsatz zu einem so frühen Zeitpunkt ermöglicht werden, dass ein Leckstrahlungsherd abgedichtet werden kann und die Funktionstüchtigkeit des Geräts wieder vollständig hergestellt werden kann, ohne dass es zu einem Komponentenausfall kommt. So können beispielsweise sich durch Veränderungen im Gerät wie aufgrund von Bauteilverzug (Spalte öffnen sich) oder Korrosion metallischer Wandungen (Rostlöcher in einer Garraumwandung) oder durch Erhöhung von Übergangswiderständen aufgrund von Oxidation oder ebenfalls Korrosion (wie einem schlechter werdenden elektrischen Kontakt von elektrischen Kontaktfolien oder Dichtungsgeflechten an z.B. Hohlleiter-Muffel-Übergängen oder Heizkörperflanschen) entwickelnde Leckstrahlungsherde frühzeitig erkannt und durch den Kundendienst korrigiert werden. Beispielsweise kann es durch eine Mikrowellen-Leckage zu Störungen (z.B. einer schwankenden Leistungsaufnahme) eines Inverters, eines Mikrowellengenerators kommen, in deren Folge sowohl der Inverter als auch ein Magnetron durch Überlastung zerstört werden können. Es ergibt sich auch eine Zeitersparnis für den Kundendienst bei der Fehlersuche, und ein Kundendienstmitarbeiter kann ggf. zu tauschende Bauteile gleich zum Kunden mitnehmen.The object is achieved by a household microwave appliance, having a cooking chamber and at least one detection device for detecting microwave leakage radiation outside the cooking chamber, with

• the detection device has at least one electrically conductive line ("antenna line") in which alternating currents can be induced by microwaves, and an evaluation circuit connected to the at least one antenna line, which is designed to determine alternating currents induced in the at least one antenna line, and wherein
• - The at least one antenna line has at least one further function.

This household microwave appliance has the advantage that no separate electrical line is required in order to detect a leakage of microwaves. This in turn advantageously enables a particularly cost-effective structure. In addition, the antenna line can have a great length and be laid in various ways in the household microwave device. This has the advantage that large areas of the household microwave appliance outside the cooking chamber can be monitored for microwave leakage with one antenna line, thereby reducing the number of detection devices and / or their components can be reduced in comparison to microwave detection devices that only measure punctually. A particularly reliable and cost-effective structure is thus made possible. A further advantage is that the evaluation circuit can be arranged remotely from leakage radiation sources in areas of the household microwave appliance that are not subject to much thermal, chemical and / or electromagnetic stress. The antenna cables, on the other hand, are noticeably more resistant and can easily pass through thermally and chemically stressed (eg hot and / or humid) areas. Another advantage is that microwave leaks can be detected with high sensitivity. In this way, impending high microwave leaks in the device can be detected at an early stage. This in turn has the effect of reducing the potential risk to users and customer service employees. In addition, the early detection of a microwave leak enables customer service to be carried out at such an early stage that a leakage radiation source can be sealed and the functionality of the device can be fully restored without a component failure occurring. For example, changes in the device such as component distortion (gaps open) or corrosion of metallic walls (rust holes in a cooking chamber wall) or an increase in contact resistance due to oxidation or corrosion (such as deteriorating electrical contact from electrical contact foils or sealing braids) can occur sources of leakage radiation that develop on, for example, waveguide-muffle transitions or radiator flanges) can be detected early and corrected by customer service. For example, a microwave leakage can cause interference (for example fluctuating power consumption) in an inverter or a microwave generator, as a result of which both the inverter and a magnetron can be destroyed by overload. This also saves time for customer service when searching for errors, and a customer service representative can, if necessary, take components to be replaced with him to the customer.

The household microwave device can be a cooking device with a microwave function, in particular an oven with an additional microwave function, a stand-alone microwave device or a microwave device with additional IR heating elements such as resistance heating elements, IR radiators, etc.

A household microwave appliance typically has at least one microwave generator, such as a semiconductor-based microwave generator or a magnetron, in order to generate microwaves, by means of which the items located in the cooking space can be treated or acted upon. The microwave frequency can be in the range of 915 MHz or 2.45 GHz, for example. The microwave generator can feed the microwaves into the cooking space directly or via a microwave guide. In addition, means for distributing the microwaves in the cooking space, such as, in particular, rotatable feed antennas, mode stirrers, wobblers, etc., can be present. The generation and introduction of microwaves into the cooking space is generally well known and is therefore not discussed further here.

The microwave detection device is used to detect microwave leakage radiation outside the cooking space, in particular microwave leakage radiation in an area of the household microwave device between a cooking space wall (hereinafter also referred to as “muffle”) and an outer housing, but also in door gaps, etc. .

The antenna line is an electrically conductive, in particular metallic, line, e.g. a conductor track, wire, cable, etc., into which alternating currents can be induced by the microwaves generated by the microwave generator.

The evaluation circuit is set up in particular to determine the strength of a microwave-induced current induced in the at least one antenna line, which is a measure of the strength of the leakage or leak rate. The evaluation circuit can 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.

In one development, an evaluation circuit can be connected to precisely one antenna line and therefore only evaluate this antenna line or determine the strength of a microwave-induced current induced in this antenna line. It is an alternative development that an evaluation circuit is connected to several antenna lines. In this case, several antenna lines can be evaluated jointly by the evaluation circuit. The joint evaluation enables a particularly simple and inexpensive detection device to be provided. The covered or detectable detection area can also be enlarged as a result, so that the evaluation unit can respond earlier in the event of a leak. In a further development, several antenna lines can be electrically brought together for this purpose and connected to the evaluation circuit at a common node. Alternatively, several antenna lines can be evaluated individually using the same evaluation circuit, for example at different times or in parallel. The individual evaluation enables an improved localization of a leakage radiation source.

Alternatively, the household microwave appliance can contain several e.g. each have evaluation circuits connected to an antenna line. These can be arranged distributed over the household microwave device.

It is a further development that the at least one antenna line has or performs at least one further function, at least in sections. In particular, an electrical line that is already present for another purpose can also be used as an antenna line. A line having the at least one further function would thus also be present in the device if it were not used to detect the microwave leakage.

In one embodiment, the at least one further function comprises a power supply function for supplying at least one electrical consumer of the household microwave appliance with electrical energy and / or a data transmission function. In other words, at least one antenna line is a power supply line for at least one electrical consumer and / or a data transmission line. The (“load”) current used to operate the consumer can be a direct current or an alternating current. Such antenna lines have the advantage that they are typically designed to be the same over their length and / or have a defined, particularly low electrical resistance. In this way, in turn, a particularly precise and reliable detection or evaluation of the microwave-induced alternating currents can be achieved. Another advantage is that such antenna lines typically connect functional units to one another, which are located in room areas of the household microwave appliance that are not exposed to much thermal and / or chemical and / or electromagnetic stress. Consequently, the evaluation circuit can also be arranged with little or no adaptation effort on end sections of the antenna lines in these areas.

In principle, however, it is also possible to use other electrically conductive components of the household microwave device that fulfill a mechanical function, for example, as antenna cables, in particular elongated components such as struts, fastening wires, etc. Shape e.g. of wires to the evaluation circuit so that the evaluation circuit can be accommodated in a thermally and / or chemically less stressed area and / or to enable an electrical connection to the evaluation circuit. The additional line sections can be soldered to the electrically conductive components, etc.

It is an embodiment that the at least one electrical consumer comprises a heating element, a light generating device, a motor, a power supply device and / or electronics (e.g. a control board) etc. The heating element can e.g. be a resistance heating element for heating the cooking space or an evaporator. The light generating device can e.g. be or have a lamp or other lighting device, for example to illuminate the cooking space, control elements or decorative elements. The motor can e.g. be a motor for moving a rotary antenna, a roasting spit, a fan, a flap (e.g. a vapor flap), a turntable, a cooking chamber door, a pump, etc. In principle, however, the at least one electrical consumer is not restricted to this and can be any other consumer such as a control panel or component thereof, a camera, a communication module (e.g. a WLAN or Ethernet module), etc.

It is an embodiment that at least one antenna line has at least one data transmission function and is connected to at least one functional unit of the device that does not represent an electrical consumer, e.g. with a sensor, a reed contact or other magnetic switch, etc. This case can exist, for example, when the functional unit that does not consume electricity is a sensor, e.g. a temperature sensor, especially temperature sensor. However, there are also sensors that represent electrical consumers, for example oxygen sensors in the form of lambda probes that have a heating element. If the functional unit that does not represent an electrical consumer is a reed contact, in one variant this could only switch signal levels (e.g. a microcontroller evaluates the switching state), in another variant e.g. an excitation current of a relay coil. The cabling of both reed contacts would be suitable antenna lines.

An electrical line can also be set up or used as an antenna line, which serves both for power supply and for data transmission, e.g. by modulating a power supply signal with a data signal. In principle, an electrical consumer can be connected both to a dedicated power supply line and to a dedicated data line, one or more of which can serve as an antenna line.

It is an embodiment that at least one antenna line has at least one section, the shape and / or position of which is determined (only) by the function of the antenna line for detecting the microwave leakage radiation. This section therefore does not contribute to the implementation of the further function of the antenna line or can even have a negative effect on it (even if typically only slightly). The advantage of such a section is that it is shaped and / or relocated for improved detection of microwave leakage radiation and thus enables its particularly reliable detection. The section can for example be placed through or around areas of openings in a cooking chamber wall. Due to the increased length, its ohmic resistance is increased, but this need only have a negligibly small or practically no effect on its power line and / or data transmission function. The section can also be twisted (for example, meander-shaped).

It is an embodiment that at least one antenna line has a length of at least 800 mm, in particular of at least 1000 mm, in particular of at least 1500 mm, in particular of at least 2000 mm. Such a long length has the advantage that as many / large areas as possible inside the housing of the household microwave device can be covered with an antenna line and locally distributed sources of leakage radiation can be sensed or detected with a small number of antenna lines.

Since the sources of leakage radiation are not only spatially distributed, but often also radiate at different rates over time (for example, due to a different mode distribution in the cooking chamber due to the movement of a feed antenna, a mode stirrer and / or a turntable), it is advantageous that the antenna line has a locally and possibly . Also has a time-integrating property. The superposition of the different radiated microwave signals then results in the sum signal applied to the microwave sensor. This superposition is more pronounced the longer the antenna cable is.

It is an embodiment that the microwave detection device additionally has at least one electrically conductive line in which alternating currents can be induced by microwaves, which is connected to the evaluation circuit and which has no further signal-conducting (ie no current and / or data-conducting) function has, in particular has no further function. Such a line is referred to below as a "sniffer line". The sniffer line is only laid for the purpose of detecting microwave-based induction. The household microwave appliance can consequently be designed such that the evaluation circuit is connected to at least one antenna line (which also fulfills at least one further function) and to at least one sniffer line (without a dedicated further function). Providing a sniffer line has the advantage that it can be laid in the device in a particularly variable manner, e.g. because it is functionally connected to the evaluation circuit at one end, but the other end is a freely positionable end. A sniffer line can basically be designed and / or connected analogously to an antenna line. As a sniffer line, e.g. a wire, a cable, a conductor track applied to a substrate, etc. can be used.

It is a further development that at least one evaluation circuit is an independent component of the household microwave appliance, is arranged separately from a control device and is connected to the control device via at least one signal line. This has the advantage that at least one evaluation circuit can be positioned particularly flexibly in the household microwave appliance. As an output signal or output information, the evaluation circuit can in particular provide information about the strength of the microwave-induced alternating current. The output signal or the output information can be in analog or digital form. The output signal or the output information can be used by the control device to assess whether at least one action associated with the strength of the leak rate should be triggered, as will be described in more detail below.

It is an embodiment that the evaluation circuit is integrated in a control device of the household microwave appliance. This has the advantage that the evaluation circuit is accommodated in a spatial area which is particularly well suited or provided for accommodating electrical and / or electronic components. This is particularly advantageous if the control device is accommodated in a specially protected compartment, compartment or compartment which is, for example, thermally insulated and / or ventilated to cool the evaluation unit. Another advantage is that the signal paths between the evaluation circuit and the control device are particularly short and therefore not susceptible to interference. In particular, the output signals or output information can be passed directly to a processor (for example a microcontroller, FPGA, ASIC, etc.) of the control device. Another advantage is that a plurality of electrical lines (power supply lines and / or data lines) typically lead from the control device to consumers, so that the positioning of the evaluation circuit on the control device is particularly short distances from the allows at least one antenna line to the evaluation circuit.

It is a further development that the evaluation circuit is integrated into the control device of the household microwave appliance in such a way that it is an independent structural unit (e.g. has its own circuit board or printed circuit board) which is attached to the circuit board or circuit board of the control device, e.g. by soldering connection (s), a slot, etc.

It is a further development that the evaluation circuit is integrated into the control device of the household microwave appliance in such a way that a circuit board of the control device is equipped with the components of the evaluation circuit.

It is a further development that the evaluation circuit is functionally integrated into the control device to the extent that a processor of the control device also takes over the evaluation of the antenna line (s). Advantageously, there is then no longer any need for a separate or separately manufactured evaluation circuit.

In one embodiment, the evaluation circuit is connected to the at least one antenna line via at least one conductor track on a circuit board of the control device. This enables a particularly simple, space-saving and robust connection of the evaluation circuit to the at least one conductor track. In particular, an antenna line is led to the circuit board and connected there to the conductor track, e.g. by soldering points, terminals, plugs, etc.

It is an embodiment that the evaluation circuit is connected to the at least one antenna line via a coupling capacitor. This has the advantage that the antenna line is galvanically isolated from the evaluation circuit, but alternating current signals can be transmitted through the coupling capacitor. The coupling capacitor thus achieves a DC voltage separation between the antenna line and the evaluation circuit. In particular, one connection of the coupling capacitor is electrically connected to at least one antenna line and the other connection is electrically connected to the evaluation circuit. The coupling capacitor can also represent part of the evaluation circuit.

It is an embodiment that the coupling capacitor is a component of a high-pass filter. This has the advantage that the comparatively high-frequency microwave-induced alternating currents (which e.g. can have a frequency in the range of the microwave frequency) are allowed to pass through to the evaluation circuit, while low-frequency alternating currents, such as those e.g. are typically used to supply a load with alternating current (e.g. with a mains frequency of 50 Hz), cannot be let through. This prevents the measurement signal of the microwave leakage radiation from being disturbed by electrical currents in the antenna lines with lower frequencies, which in turn increases the accuracy of the evaluation.

It is a further development that the coupling capacitor forms the high-pass filter together with a particularly grounded ohmic resistor. The resistance can be a component of the evaluation circuit, e.g. their input resistance.

aufweist, wobei R dem Widerstandswert des ohmschen Widerstands und f_u einer unteren Grenzfrequenz des Hochpassfilters entspricht.It is an embodiment that the high-pass filter additionally has a resistor connected to the coupling capacitor, in particular an input resistor, and the coupling capacitor has a capacitance of the same size C. (GI.1): $$\text{C.}=\frac{1}{2\cdot \pi \cdot \mathrm{R.}\cdot f_u}$$

wherein R corresponds to the resistance value of the ohmic resistance and f _u corresponds to a lower limit frequency of the high-pass filter.

This formula results from a complex transfer function I, which shows the ratio of a voltage U ₂ passed on by the high-pass filter to the voltage U _{1 present} on the monitored or tapped antenna line (Eq. 2): $$\underset{\_}{T}=\frac{\underset{\_}{{\mathrm{<figure-callout\; id="2"\; label="U"\; filenames="DE102019207978A1\_0007.png"\; state="\{\{state\}\}">U</figure-callout>}}_2}}{\underset{\_}{U_1}}=\frac{1}{1-\frac{\mathrm{<figure-callout\; id="2"\; label="i"\; filenames="DE102019207978A1\_0007.png"\; state="\{\{state\}\}">i</figure-callout>}}{2\pi \cdot f\cdot \mathrm{R.}\cdot \mathrm{C.}}}$$

Since only the magnitude of the transfer function (and not its phase position) is of interest here, it follows (Eq. 3): $$\left|\underset{\_}{T}\right|=\left|\frac{\underset{\_}{{\mathrm{<figure-callout\; id="2"\; label="U"\; filenames="DE102019207978A1\_0007.png"\; state="\{\{state\}\}">U</figure-callout>}}_2}}{\underset{\_}{U_1}}\right|=\frac{1}{\sqrt{1+\frac{1}{{\left(2\pi \cdot f\cdot \mathrm{R.}\cdot \mathrm{C.}\right)}^2}}}$$

For the selection and dimensioning of the coupling capacitor C. it was assumed that a lower limit frequency f _{u of} the resulting high-pass filter is as high as the signal to be measured at least requires (the measurement signal has a typical microwave frequency of 915 MHz or 2.45 GHz). The lower limit frequency f _u is set in such a way that the transmitted voltage U _{2 is} only 1 / √2 or approx. 70.7% of the amplitude of the original signal U ₁ is or the original signal U ₁ is weakened by this factor. It follows from this for the absolute value of the transfer function $$\left|\underset{\_}{T}\right|=\frac{1}{\sqrt{2}}=\frac{1}{\sqrt{1+\frac{1}{{\left(2\pi \cdot f\cdot \mathrm{R.}\cdot \mathrm{C.}\right)}^2}}}$$

This results in the advantageous size of the capacitance value C. of the coupling capacitor according to equation 1.

If a sniffer line is connected to the evaluation circuit, it does not need to be galvanically separated from the evaluation circuit by a coupling capacitor. The provision of a high-pass filter can also be dispensed with. Alternatively, the sniffer line is also connected via a coupling capacitor and / or a high-pass filter.

The output or calculation values determined by the evaluation circuit, which represent a measure of the microwave leakage, can be evaluated by the control device. One embodiment is that the household microwave appliance, in particular its control device, is set up to trigger at least one action based on a specific or calculated strength of the alternating current induced by the microwave in at least one antenna line. This has the advantage that it is possible to react automatically to an excessively high leak rate. For example, if a limit value for the calculation values is exceeded, the control device can output a message to a user and / or to a customer service and / or switch off the household microwave appliance.

It is a further development that the calculation values are stored, e.g. by the control device, in particular in a data memory of the household microwave appliance and / or in an external entity such as a network server. Calculation values can only be saved from the last operating sequence and / or calculation values from several operating sequences. Saving them has the advantage that the calculation values can be evaluated in order to be able to detect a progression of the leak rate over time and thus any drift in a particularly reliable manner.

It is a further development that the quality of the delivered devices can be tracked via remote data transmission of the calculation values and a prospective assessment of future service requirements is possible. By reading out the stored data, customer service can determine whether a shutdown of a microwave device is due to an increased leak rate in the device, and thus narrow down the causes of the error. Aging phenomena in the device / on components (e.g. the magnetron) can also be determined and assessed.

The object is also achieved by a method for operating a household microwave device, in particular as described above, in which electrical useful signals (in particular load currents and / or data signals) to and / or from at least one functional unit via at least one electrical line (“antenna line”) of the household microwave device (in particular from and / or to a control device of the device) and from this at least one antenna line microwave-induced alternating currents are tapped (e.g. by means of an evaluation circuit) and evaluated (e.g. by means of the evaluation circuit or the control device).

The method can be designed analogously to the above household microwave appliance and produces the same advantages.

• 1 zeigt als Schnittdarstellung in Seitenansicht ein Haushalts-Mikrowellengerät;
• 2 zeigt in Draufsicht eine Steuereinrichtung des Haushalts-Mikrowellengeräts aus 1 mit einer Auswerteschaltung; und
• 3 zeigt eine alternative Auswerteschaltung für das Haushalts-Mikrowellengerät aus 1.

The properties, features and advantages of this invention described above and the manner in which they are achieved will become clearer and more clearly understood in connection with the following schematic description of an exemplary embodiment which is explained in more detail in connection with the drawings.

• 1 shows, as a sectional illustration in side view, a household microwave appliance;
• 2 shows a plan view of a control device of the domestic microwave appliance 1 with an evaluation circuit; and
• 3 shows an alternative evaluation circuit for the household microwave device 1 .

1 shows, as a sectional illustration in side view, a sketch of a household microwave appliance 1 with a cooking space 2 . The cooking space 2 is from a cooking chamber wall or muffle 3 surrounded, the one with a door 4th Has closable front loading opening. The household microwave oven 1 instructs to treat in the oven 2 goods (not shown) at least one microwave generator 5 on, possibly also other heating elements such as one or more resistance heating elements (not shown).

There is also an operating device 6th present, which can have one or more operating elements and / or display devices, for example in the form of a touch-sensitive screen. Also includes the household microwave oven 1 one in the oven 2 existing turntable 7th by means of an outside of the cooking space 2 arranged motor 8th is rotatable. The household Microwave oven 1 or its controllable components 5 , 6th , 8th are by means of a central control device 9 (also referred to as "device control") controllable or operable.

In the control device 9 is an evaluation circuit 10 integrated with an antenna cable 11 connected is. The antenna line 11 is the electrical line that comes from the control device 9 to the engine 8th leads to the engine 8th to provide power and / or data about the motor 8th to control it. The antenna line 11 is also suitable for the fact that alternating currents can be induced in it by microwaves. The evaluation circuit 10 is used to determine in the antenna line 11 induced alternating currents. The evaluation circuit 10 and the antenna line 11 form a detection device 10 , 11 for detecting microwave leakage radiation outside the cooking space 2 , especially in a space between the cooking space 2 and an outer case 12 of the household microwave oven 1 . The antenna line 11 thus has a double function, namely firstly for power and / or data transmission between the control device 9 and the engine 8th and secondly as a “sensor line” for detecting microwave leakage radiation.

The antenna line 11 can correspond to the line that would also be used if it were not set up or intended to be used as a sensor line. Alternatively, the antenna cable 11 have at least one section (not shown) whose shape and / or position depends on the function of the antenna line 11 is intended as a sensor cable. So can such an antenna line 11 e.g. a breakthrough in the muffle 3 be led around by a drive shaft of the motor 8th to the turntable 7th leads. Additionally or alternatively, the antenna line 11 For example, have at least one corrugated or meander-shaped section, which for example via assembly joints, further openings or the like. the grouch 3 runs.

The antenna line 11 can have a length of at least 800 mm, in particular of at least 1000 mm, in particular of at least 1500 mm, in particular of at least 2000 mm.

The household microwave oven 1 can optionally have at least one sniffer line 13 , for example, have a simple wire or a simple cable which is only intended to serve as a sensor line and which is connected to the evaluation circuit and which has no further function. The sniffer line 13 is also with the evaluation circuit 10 connected.

2 shows a plan view of the control device 9 with some of the components present on it. To a circuit board 14th the control device 9 are several electrical lines 15th out, which at their other ends with functional units of the household microwave device 1 how electrical consumers and / or sensors are connected (and thus represent antenna lines) and / or sniffer lines 13 are. Here corresponds one of the electrical lines 15th the antenna cable 11 .

The electrical lines 15th are at connection points 16 like clamps or similar with the circuit board 14th connected and go there in corresponding conductor tracks 17th the circuit board 14th above. In the exemplary embodiment shown, only the antenna line is purely by way of example 11 with one on the circuit board 14th arranged evaluation circuit 10 connected, in turn, to a processor 18th , eg a microcontroller, ASIC or FPGA, the control device 9 connected is. The evaluation circuit 10 is therefore in the control device 9 integrated.

In particular, the evaluation circuit 10 here from the one with the aerial cable 11 connected conductor track 17th via a coupling capacitor 19th connected, the DC voltage separation between the evaluation circuit 10 and the antenna cable 11 causes.

The evaluation circuit 10 shows, as in the enlarged section A. shown at least one ohmic resistor 20th on, the one with the one with the processor 18th connected terminal is connected and on the other hand is connected to a predetermined reference potential or ground. The coupling capacitor 19th and the resistance 20th form a high pass filter 19th , 20th for that from the aerial line 11 incoming signal.

mit R dem Widerstandswert des Widerstands 20 und f_u einer gewünschten unteren Grenzfrequenz des Hochpassfilters 19, 20 auf. Die untere Grenzfrequenz f_u ist so gewählt, dass praktisch nur die mikrowelleninduzierten Spannungsanteile durchgelassen werden.The coupling capacitor 19th here advantageously has a capacitance value C. the size $$\text{C.}=\frac{1}{2\cdot \pi \cdot \mathrm{R.}\cdot f_u}$$

where R is the resistance value of the resistor 20th and f _{u of} a desired lower cutoff frequency of the high-pass filter 19th , 20th on. The lower limit frequency f _u is chosen so that practically only the microwave-induced voltage components are allowed through.

The Z. B. analog - output signal of the evaluation circuit 10 goes to the processor for evaluation 18th routed (e.g. to an analog input of a microcontroller). However, the evaluation circuit 10 also other components or Have components (not shown), for example an A / D converter, operational amplifier, etc.

The control device 9 may be set up based on a strength of the antenna line 11 microwave-induced alternating current, represented by the output signal of the evaluation circuit 10 to trigger at least one action, e.g. a power output from the microwave generator 5 to reduce the microwave generator 5 switch off, issue a message to the user and / or customer service, etc.

This is the case, for example, if there are leakage sources in or on the muffle 3 form or enlarge. The ones from the grouch 3 Microwaves emerging as leakage radiation induce an alternating current in the antenna cable 11 that goes through the high pass filter 19th , 20th is tapped and by the processor 18th is evaluated.

The output signals of the evaluation circuit 10 or a part of it or values derived therefrom can be stored, for example in order to use them as historical data for improved detection of sources of leakage.

3 shows an evaluation circuit 10 alternative evaluation circuit 21st . The alternative evaluation circuit 10 also has a filter function, but now with the provision of an LC filter.

Instead of the in 2 shown ohmic resistance 20th are now a first coil via a common node 22nd with an inductance value L1 and an anode side of a diode 23 with the coupling capacitor 19th connected. The other terminal of the first coil 22nd is connected to ground, while the cathode connection of the diode 23 via another node with a second capacitor 24 with a capacity value C2 and with a second coil 25th with an inductance value L2 connected is. The other terminal of the second capacitor 24 is connected to ground, while the other terminal of the second coil 25th with the processor 18th connected is.

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

Several antenna lines can also be used 11 and / or at least one sniffer line to an evaluation circuit 10 or several evaluation circuits 10 be connected.

In general, “a”, “a” etc. can be understood as a singular or a plurality, 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.

A number can also include exactly the specified number and a customary tolerance range, as long as this is not explicitly excluded.

List of reference symbols

1

Household microwave oven

2

Cooking space

3

Grouch

4th

door

5

Microwave generator

6th

Control device

7th

Turntable

8th

engine

9

Control device

10

Evaluation circuit

11

Antenna cable

12

casing

13

Sniffer line

14th

Circuit board

15th

Electrical line

16

Connection point

17th

Track

18th

processor

19th

Coupling capacitor

20th

resistance

21st

Evaluation circuit

22nd

First coil

23

diode

24

Second capacitor

25th

Second coil

A.

Cutout

C.

Capacity value

C2

Capacity value

R.

Resistance value

L1

Inductance value

L2

Inductance value

QUOTES INCLUDED IN THE DESCRIPTION

This list of the documents listed by the applicant was generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Patent literature cited

• EP 2152047 A1 [0002]
• EP 2148553 A1 [0003]
• DE 2029559 A1 [0004]
• DE 19537755 A1 [0005]

Claims (13)

Household microwave appliance (1), having a cooking chamber (2) and at least one detection device (10, 11; 21, 11) for detecting microwave leakage radiation outside the cooking chamber (2), wherein - The detection device (10, 11; 21, 11) has at least one antenna line (11) in which alternating currents can be induced by microwaves, and an evaluation circuit (10; 21) connected to the at least one antenna line (11) which is used to determine in the at least one antenna line (11) is formed of induced alternating currents and wherein - The at least one antenna line (11) has at least one further function. Household microwave device (1) according to Claim 1 , the at least one further function comprising a power supply function for supplying at least one electrical load (8) of the household microwave appliance (1) with electrical energy, a data transmission function and / or a mechanical function. Household microwave device (1) according to Claim 2 wherein the at least one electrical load comprises - a heating element, - a light generating device, - a motor (8), - a power supply device and / or - electronics. Household microwave device (1) according to one of the Claims 2 or 3 , wherein at least one antenna line has at least one data transmission function and is connected to at least one functional unit of the device, in particular a sensor, which is not an electrical consumer. Domestic microwave appliance (1) according to one of the preceding claims, wherein at least one antenna line (11) has at least one section, the shape and / or position of which is determined by the function of the antenna line (11) for detecting the microwave leakage radiation. Domestic microwave appliance (1) according to one of the preceding claims, wherein at least one antenna line (11) has a length of at least 800 mm, in particular of at least 1000 mm, in particular of at least 1500 mm, in particular of at least 2000 mm. Household microwave appliance (1) according to one of the preceding claims, wherein the microwave detection device (10, 11; 21, 11) additionally has at least one sniffer line (13) in which alternating currents can be induced by microwaves, which are connected to the evaluation circuit (10 ; 21) is connected and has no other function. Domestic microwave appliance (1) according to one of the preceding claims, wherein the evaluation circuit (10; 21) is integrated in a control device (9) of the domestic microwave appliance (1). Household microwave device (1) according to Claim 8 , the evaluation circuit (10; 21) being connected to the at least one antenna line (11) via at least one conductor track (17) on a circuit board (14) of the control device (9). Household microwave device (1) according to one of the Claims 8 or 9 wherein the evaluation circuit (10; 21) is connected to the at least one antenna line (11) via a coupling capacitor (19) and the coupling capacitor (19) is a component of a high-pass filter (19, 20; 19, 22-25). Household microwave device (1) according to Claim 10 , the high-pass filter (19, 20) additionally having an ohmic resistor (20) connected to the coupling capacitor (19) and the coupling capacitor (19) having a capacitance value C of the size $$\text{C.}=\frac{1}{2\cdot \pi \cdot \mathrm{R.}\cdot f_u}$$

with R the resistance value of the ohmic resistor (20) and f _u a lower limit frequency of the high-pass filter (19, 20). Domestic microwave appliance (1) according to one of the preceding claims, wherein the domestic microwave appliance (1) is set up to trigger at least one action based on a strength of the alternating current microwave-induced in at least one antenna line (11). Method for operating a household microwave device (1) according to one of the preceding claims, wherein electrical useful signals to and / or from at least one functional unit (8) of the household microwave device (1) are transmitted via at least one antenna line (11) and from this at least An antenna line (11) microwave-induced alternating currents can be tapped and evaluated.

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