EP3977817B1 - Household microwave device comprising a detection unit for detecting microwave leakage radiation - Google Patents

Description

The invention relates to a household microwave appliance, having a cooking chamber and at least one detection device for detecting microwave leakage radiation outside the cooking chamber, 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 oven. The invention is particularly advantageously applicable to 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 appliance with a microwave function and a cooking appliance 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 other objects by leakage radiation. The sensor also includes a fuse through which the alternating current is passed. Finally, the safety device includes a device that is suitable for switching off a microwave source of the cooking appliance as soon as the safety device trips.

EP 2 148 553 A1 discloses methods for microwave leak monitoring. In the case of a cooking appliance, microwave leakage radiation emerging from the cooking chamber is detected by means of a microwave sensor device and its progression over time is stored. Subsequent evaluation of the stored microwave radiation values can include, in particular, a prognosis of the future time profile of the detected microwave radiation and early signaling that a predetermined threshold value is to be exceeded on the basis of the prognosticated profile. A corresponding device for monitoring microwave leaks and a cooking appliance 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, using at least one microwave-responsive gas tube, which is arranged in the vicinity of the zone of a possible emission of radiation and is electrically connected in 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 surrounded by a housing, 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 the emission of a warning signal or switches off the microwave loading of 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 leakage of microwaves escaping from a cooking chamber of a household microwave appliance.

This object is solved 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.

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, wherein

• 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 additional function.

This household microwave oven has the advantage that no separate electric line is required to detect leakage of microwaves. This in turn advantageously enables a particularly cost-effective construction. In addition, the antenna line can have a great length and can be routed in many ways in the household microwave device. This has the advantage that large areas of the household microwave appliance outside of the cooking chamber can be monitored for microwave leakage using an antenna line, which means that the number of detection devices and/or their components can be reduced compared to microwave detection devices that only measure selectively. A particularly reliable and cost-effective construction is thus made possible. A further advantage is that the evaluation circuit can be arranged remotely from sources of radiation leakage in areas of the household microwave appliance that are subject to little thermal, chemical and/or electromagnetic stress. The antenna cables, on the other hand, are noticeably more resistant and can also run through thermally and chemically stressed (e.g. hot and/or humid) areas without any problems. Another advantage is that microwave leaks can be detected with high sensitivity. As a result, high levels of microwave leakage that are still imminent in the device can be detected at an early stage. This in turn reduces the risk potential for users and customer service employees. In addition, the early detection of a microwave leak can enable customer service at such an early stage that a source of radiation leakage can be sealed and the functionality of the device can be fully restored without component failure occurring. For example, changes in the device due to component distortion (gaps open) or corrosion of metal walls (rust holes in a cooking chamber wall) or an increase in contact resistance due to oxidation or also corrosion (such as a worsening electrical contact of electrical contact foils or sealing braids (e.g. at waveguide-muffle transitions or radiator flanges) developing sources of leakage radiation can be detected early and corrected by customer service. For example, a microwave leak can lead to malfunctions (eg a 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 overloading. There is also a time saving for customer service when troubleshooting, and a customer service employee can take components that may need to be replaced straight away to the customer.

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

A domestic 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 in the cooking chamber 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 directly into the cooking chamber or via a microwave guide. In addition, means for distributing the microwaves in the cooking chamber, such as feed antennas, in particular rotatable ones, mode stirrers, wobblers, etc., can be present. The generation and introduction of microwaves into the cooking chamber 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 chamber, in particular microwave leakage radiation in an area of the household microwave between a cooking chamber 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 strip conductor, wire, cable, etc., in which alternating currents can be induced by 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 current is a measure of the strength of the leakage or leakage rate. The evaluation circuit can have one or more electrical and/or electronic components and/or functional units such as capacitors, resistors, processors (eg microcontrollers, ASICs, FPGAs), rectifiers, A/D converters, etc.

In one development, an evaluation circuit can be connected to exactly one antenna line and therefore only evaluate this antenna line or determine the strength of a microwave-induced current induced in this antenna line. In an alternative development, an evaluation circuit is connected to a number of antenna lines. In this case, several antenna lines can be evaluated jointly by the evaluation circuit. The joint evaluation makes it possible to provide a particularly simple and inexpensive detection device. The covered or detectable detection area can also be enlarged in this way, so that the evaluation unit can respond even more quickly in the event of a possible leak. In a further development, several antenna lines can be brought together electrically and connected to the evaluation circuit at a common node. Alternatively, several antenna lines can be evaluated individually using the same evaluation circuit, e.g. at different times or in parallel. The individual evaluation enables an improved localization of a leakage radiation source.

Alternatively, the household microwave device can have several evaluation circuits, each connected to an antenna line, for example. These can be distributed over the household microwave oven.

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

In one configuration, the at least one further function comprises a power supply function for supplying electrical energy to at least one electrical consumer of the household microwave appliance 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 current used to operate the load ("load") can be direct current or alternating current. Such antenna lines have the advantage that they are typically of the same design over their length and/or have a defined, have particularly low electrical resistance. As a result, a particularly precise and reliable detection or evaluation of the alternating currents induced therein by the microwave can be achieved. A further advantage is that antenna lines of this type typically connect functional units to one another which are located in areas of the household microwave appliance which are subject to little thermal and/or chemical and/or electromagnetic stress. Consequently, the evaluation circuit can also be arranged in these areas with little or no adjustment effort at the end sections of the antenna lines.

In principle, however, it is also possible to use other electrically conductive components of the household microwave device that, for example, fulfill a mechanical function as antenna lines, in particular elongated components such as struts, fastening wires, etc. In this case, it may be necessary to separate the components with additional line sections in E.g. to lengthen the form of wires to the evaluation circuit, so that the evaluation circuit can be accommodated in a room area with little thermal and/or chemical stress and/or to enable an electrical connection to the evaluation circuit. The additional line sections can be soldered etc. to the electrically conductive components.

In one configuration, the at least one electrical load comprises a heating element, a light generating device, a motor, a power supply device and/or electronics (e.g. a control board), etc. For example, the heating element may be a resistance heating element for heating the cooking chamber or an evaporator. The light-generating device can, for example, be or have a lamp or other lighting device, for example to illuminate the cooking chamber, operating elements or decorative elements. For example, the motor may be a motor for moving a rotary antenna, a roasting skewer, a fan, a damper (e.g., a damper), a turntable, a cooking chamber door, a pump, and so on. In principle, however, the at least one electrical consumer is not limited 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.

In one configuration, at least one antenna line has at least one data transmission function and, with at least one, no electrical loads representing functional unit of the device is connected, eg with a sensor, a reed contact or other magnetic switch, etc. This case can be present, for example, when the non-current-consuming functional unit is a sensor, eg a temperature sensor, specifically a temperature sensor. However, there are also sensors that represent electrical loads, for example oxygen sensors in the form of lambda probes that have a heating element. If the functional unit that is not an electrical consumer is a reed contact, this could in one variant only switch the signal level (whereby, for example, a microcontroller evaluates the switching state), in another variant, for example, an excitation current of a relay coil. The wiring of both reed contacts would be suitable antenna lines.

An electrical line can also be set up or used as an antenna line, which is used both for power supply and for data transmission, e.g. by modulating a power supply signal with a data signal. In principle, an electrical load 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.

In one configuration, at least one antenna line has at least one section whose shape and/or position is (only) determined by the function of the antenna line for detecting the microwave leakage radiation. This section therefore does not contribute to carrying out the further function of the antenna line or can even (even if typically only slightly) have a negative effect on it. The advantage of such a section is that it is shaped and/or routed for improved detection of microwave leakage radiation and thus enables its particularly reliable detection. The section can be placed, for example, through or around areas of openings in a cooking chamber wall. The increased length increases its ohmic resistance, but this may have negligible or virtually no effect on its power-carrying and/or data-transmission function. The section can also have an intricate (e.g. meandering) shape.

It is an embodiment that at least one antenna line has a length of at least 800 mm, in particular at least 1000 mm, in particular at least 1500 mm, in particular 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 thus 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 distributed locally, but often also radiate at different strengths over time (e.g. due to different mode distributions in the cooking chamber due to movement of a feed antenna, a mode stirrer and/or a turntable), it is advantageous for the antenna cable to have a local and possibly Also has a property that integrates over time. The superposition of the different irradiated microwave signals then results in the sum signal present at the microwave sensor. This superposition is all the more pronounced the longer the antenna line is.

In one configuration, 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 has no further signal-conducting (i.e. 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 therefore only laid for the purpose of detecting a microwave-based induction. The household microwave device can consequently be designed in such a way that the evaluation circuit is connected to at least one antenna line (which also fulfills at least one additional function) and to at least one sniffer line (without a dedicated additional function). The provision of a sniffer line has the advantage that it can be routed in a particularly variable manner in the device, e.g. because it is functionally connected to the evaluation circuit at one end, but the other end is a freely positionable end. In principle, a sniffer line can be designed and/or connected analogously to an antenna line. For example, a wire, a cable, a conductor track applied to a substrate, etc. can be used as a sniffer line.

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

In one configuration, the evaluation circuit is integrated into a control device of the household microwave appliance. This achieves 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, division or compartment that is, for example, thermally insulated and/or ventilated to cool the evaluation unit. A further 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 routed directly to a processor (e.g. a microcontroller, FPGA, ASIC, etc.) of the control device. Another advantage is that typically several electrical lines (power supply lines and/or data lines) lead from the control device to consumers, so that the positioning of the evaluation circuit on the control device enables particularly short distances from the 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 oven in such a way that it is an independent structural unit (e.g. has its own circuit board or circuit board) which is attached to the circuit board or circuit board of the control device, e.g. by a soldered connection (s), a slot, etc.

In a further development, the evaluation circuit is integrated into the control device of the domestic microwave appliance in such a way that a printed circuit board of the control device is equipped with the components of the evaluation circuit.

In one development, the evaluation circuit is functionally integrated into the control device to such an extent that a processor in the control device also evaluates the antenna line(s). A separate or separately manufactured evaluation circuit is then advantageously no longer required.

In one configuration, the evaluation circuit is connected to the at least one antenna line via at least one conductor track on a printed circuit board of the control device. A particularly simple, space-saving and robust connection of the evaluation circuit to the at least one conductor track is thus made possible. In particular, an antenna cable is routed to the circuit board and connected there to the conductor track, e.g. by soldering points, clamps, plugs, etc.

In one configuration, the evaluation circuit is connected to the at least one antenna line via a coupling capacitor. This achieves the advantage that the antenna line is electrically isolated from the evaluation circuit, but AC signals can be transmitted through the coupling capacitor. The coupling capacitor thus achieves DC voltage isolation 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.

In one configuration, the coupling capacitor is a component of a high-pass filter. In this way, the advantage is achieved that the comparatively high-frequency, microwave-induced alternating currents (which, for example, can have a frequency in the microwave frequency range) are let through to the evaluation circuit, while low-frequency alternating currents, such as those typically used for powering a consumer with alternating current (e.g. with a mains frequency of 50 Hz), cannot be let through. This prevents the measuring signal of the microwave leakage radiation from being disturbed by electrical currents in the antenna lines with lower frequencies, which in turn increases the evaluation accuracy.

In one development, the coupling capacitor forms the high-pass filter together with an ohmic resistor that is, in particular, grounded. The resistance can be a component of the evaluation circuit, e.g. its input resistance.

aufweist, wobei R dem Widerstandswert des ohmschen Widerstands und f_u einer unteren Grenzfrequenz des Hochpassfilters entspricht.In one embodiment, 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 size C (GI.1): $$C=\frac{1}{2\cdot \pi \cdot R\cdot f_{\mathrm{and}}}$$

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

This formula results from a complex transfer function T, which reflects 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): $$\underset{\_}{T}=\frac{\underset{\_}{{\mathrm{<figure-callout\; id="2"\; label="u"\; filenames="imgf0001.png"\; state="\{\{state\}\}">u</figure-callout>}}_2}}{\underset{\_}{{\mathrm{<figure-callout\; id="1"\; label="u"\; filenames="imgf0001.png"\; state="\{\{state\}\}">u</figure-callout>}}_1}}=\frac{1}{1-\frac{i}{2\pi \cdot f\cdot R\cdot C}}$$

Since only the absolute value of the transfer function (and not its phase position) is of interest here, it follows (Eq.3): $$\left|\underset{\_}{T}\right|=\frac{\left|\underset{\_}{{\mathrm{<figure-callout\; id="2"\; label="u"\; filenames="imgf0001.png"\; state="\{\{state\}\}">u</figure-callout>}}_2}\right|}{\left|\underset{\_}{{\mathrm{<figure-callout\; id="1"\; label="u"\; filenames="imgf0001.png"\; state="\{\{state\}\}">u</figure-callout>}}_1}\right|}=\frac{1}{\sqrt{1+\frac{1}{{\left(2\pi \cdot f\cdot \mathrm{<figure-callout\; id="2"\; label="R\; \cdot \; C"\; filenames="imgf0001.png"\; state="\{\{state\}\}">R</figure-callout>}\cdot C\right)}^2}}}$$

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 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 is ₁ or the original signal U is present weakened by this factor. It follows from this for the absolute value of the transfer function $$\left|\underset{\_}{T}\right|=\frac{1}{\sqrt{2}}=\frac{1}{\sqrt{1+\frac{1}{{\left(2\pi \cdot f\cdot \mathrm{<figure-callout\; id="2"\; label="R\; \cdot \; C"\; filenames="imgf0001.png"\; state="\{\{state\}\}">R</figure-callout>}\cdot C\right)}^2}}}$$

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

If a sniffer line is connected to the evaluation circuit, it does not need to be electrically isolated 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. In one configuration, 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. In this way, the advantage is achieved that it is possible to react automatically to a leak rate that is too high. For example, if a limit value of the calculation values is exceeded, the control device can output a message to a user and/or to customer service and/or switch off the household microwave oven.

In a further development, the calculation values are stored, for example by the control device, in particular in a data memory of the household microwave oven and/or in an external entity such as a network server. Calculation values of only the last operation and/or calculation values of several operations can be stored. Storing them has the advantage that the calculation values can be evaluated in order to be able to particularly reliably detect a course of the leak rate over time and thus any drift.

It is a further development that the quality status of the delivered devices can be tracked via remote data transmission of the calculation values and a prospective assessment of the future service requirement is possible. By reading out the stored data, customer service can determine whether a microwave oven has been switched off due to an increased leak rate in the appliance, and thus narrow down the causes of the fault. Signs of aging in the device / on components (e.g. the magnetron) can also be determined and evaluated.

The object is also achieved by a method for operating a household microwave appliance, in particular as described above, in which electrical useful signals (in particular load currents and/or data signals) are transmitted 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 domestic microwave oven and gives the same advantages.

Fig.1

zeigt als Schnittdarstellung in Seitenansicht ein Haushalts-Mikrowellengerät;

Fig.2

zeigt in Draufsicht eine Steuereinrichtung des Haushalts-Mikrowellengeräts aus Fig.1 mit einer Auswerteschaltung; und

Fig.3

zeigt eine alternative Auswerteschaltung für das Haushalts-Mikrowellengerät aus Fig.1.

The characteristics, 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 will be explained in more detail in connection with the drawings.

Fig.1

shows a sectional side view of a household microwave oven;

Fig.2

FIG. 12 shows a control device of the household microwave appliance in a plan view Fig.1 with an evaluation circuit; and

Fig.3

shows an alternative evaluation circuit for the household microwave oven Fig.1 .

Fig.1 shows a sectional side view of a sketch of a household microwave device 1 with a cooking chamber 2. The cooking chamber 2 is of a cooking chamber wall or surrounded muffle 3, which has a closable with a door 4 front loading opening. The domestic microwave appliance 1 has at least one microwave generator 5 for treating the material in the cooking chamber 2 (not shown), possibly also further heating elements such as one or more resistance heating elements (not shown).

There is also an operating device 6 which can have one or more operating elements and/or display devices, e.g. in the form of a touch-sensitive screen. In addition, the domestic microwave appliance 1 includes a rotary plate 7 present in the cooking chamber 2 , which can be rotated by means of a motor 8 arranged outside the cooking chamber 2 . The household microwave appliance 1 or its controllable components 5, 6, 8 can be controlled or actuated by means of a central control device 9 (also referred to as “appliance control”).

An evaluation circuit 10 is integrated into the control device 9 and is connected to an antenna line 11 . The antenna line 11 is the electrical line which leads from the control device 9 to the motor 8 in order to supply the motor 8 with electricity and/or to transmit data to the motor 8 in order 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 designed to determine alternating currents induced in the antenna line 11 . The evaluation circuit 10 and the antenna line 11 form a detection device 10, 11 for detecting microwave leakage radiation outside the cooking chamber 2, in particular in a space between the cooking chamber 2 and an outer housing 12 of the household microwave appliance 1. The antenna line 11 therefore has a dual function on, namely firstly for power and / or data transmission between the control device 9 and the motor 8 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 line 11 can have at least one section (not shown) whose shape and/or position is determined by the function of the antenna line 11 as a sensor line. For example, such an antenna line 11 can be routed around an opening in the muffle 3 through which a drive shaft of the motor 8 leads to the turntable 7 . Additionally or alternatively, the antenna line 11, for example have at least one section that runs in a corrugated or meandering manner, which runs, for example, over assembly joints, further openings or the like of the muffle 3 .

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

The household microwave appliance 1 can optionally have at least one sniffer line 13, e.g. 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 other function. The sniffer line 13 is also connected to the evaluation circuit 10 .

Fig.2 shows a plan view of a sketch of the control device 9 with some of the components present on it. Several electrical lines 15 are routed to a printed circuit board 14 of the control device 9, which are connected at their other ends to functional units of the household microwave appliance 1 such as electrical consumers and/or sensors (and thus represent antenna lines) and/or are sniffer lines 13. Here one of the electrical lines 15 corresponds to the antenna line 11.

The electrical lines 15 are connected to the printed circuit board 14 at connection points 16 such as terminals or the like and merge there into corresponding conductor tracks 17 on the printed circuit board 14 . In the exemplary embodiment shown, only the antenna line 11 is connected, purely by way of example, to an evaluation circuit 10 arranged on the circuit board 14, which in turn is connected to a processor 18, e.g. a microcontroller, ASIC or FPGA, of the control device 9. The evaluation circuit 10 is therefore integrated into the control device 9 .

In particular, the evaluation circuit 10 is connected here by the strip conductor 17 connected to the antenna line 11 via a coupling capacitor 19 which separates the evaluation circuit 10 and the antenna line 11 from the DC voltage.

As shown in the enlarged section A, the evaluation circuit 10 has at least one ohmic resistor 20 which is connected on the one hand to the terminal connected to the processor 18 and on the other hand to a predetermined reference potential or ground. The coupling capacitor 19 and the resistor 20 form a high-pass filter 19, 20 for the incoming signal from the antenna line 11.

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.In this case, the coupling capacitor 19 advantageously has a capacitance value C of the size $$C=\frac{1}{2\cdot \pi \cdot R\cdot f_{\mathrm{and}}}$$

with R the resistance value of the resistor 20 and f _u a desired lower limit frequency of the high-pass filter 19, 20. The lower limit frequency f _u is selected in such a way that practically only the microwave-induced voltage components are allowed to pass.

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

The control device 9 can be set up to trigger at least one action based on a strength of the microwave-induced alternating current in the antenna line 11, represented by the output signal of the evaluation circuit 10, e.g impersonate the user and/or a customer service, etc.

This is the case, for example, when sources of leakage form or enlarge in or on the muffle 3 . The microwaves escaping from the muffle 3 as leakage radiation induce an alternating current in the antenna line 11 which is tapped off via the high-pass filter 19, 20 and evaluated by the processor 18.

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

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

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

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

A plurality of antenna lines 11 and/or at least one sniffer line can also be connected to an evaluation circuit 10 or to a plurality of evaluation circuits 10 .

In general, "a", "an" etc. can be understood as a singular or a plural number, 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 a" etc.

A numerical specification can also include exactly the specified number as well as a usual tolerance range, as long as this is not explicitly excluded.

Reference List

1

household microwave oven

2

cooking chamber

3

muffle

4

door

5

microwave generator

6

operating device

7

turntable

8th

engine

9

control device

10

evaluation circuit

11

antenna line

12

Housing

13

sniffer line

14

circuit board

15

Electrical line

16

connection point

17

trace

18

processor

19

coupling capacitor

20

Resistance

21

evaluation circuit

22

First coil

23

diode

24

Second condenser

25

Second coil

A

cutout

C

capacitance value

C2

capacitance value

R

resistance value

L1

inductance value

L2

inductance value

Claims (13)

1. Household microwave appliance (1) having a cooking compartment (2) and at least one detection facility (10, 11; 21, 11) for detecting microwave leakage radiation outside the cooking compartment (2), wherein

   - the detection facility (10, 11; 21, 11) has at least one antenna line (11) in which alternating currents can be induced by microwaves, and an evaluating circuit (10; 21) which is connected to the at least one antenna line (11) and is designed so as to determine alternating currents that are induced in the at least one antenna line (11),
   characterised in that

   - the at least one antenna line (11) has at least one further function.
2. Household microwave appliance (1) according to claim 1, wherein the at least one further function comprises

   - a power supply function for supplying at least one electrical consumer (8) of the household microwave appliance (1) with electrical energy,

   - a data transmission function and/or

   - a mechanical function.
3. Household microwave appliance (1) according to claim 2, wherein the at least one electrical consumer comprises

   - a heating element,

   - a light generating facility,

   - a motor (8),

   - a power supply facility and/or

   - electronics.
4. Household microwave appliance (1) according to one of 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 appliance that does not represent an electrical consumer, in particular sensor.
5. Household 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.
6. Household 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.
7. Household microwave appliance (1) according to one of the preceding claims, wherein the microwave detection facility (10, 11; 21, 11) in addition has at least one sniffer line (13) in which alternating currents can be induced by microwaves and which is connected to the evaluating circuit (10; 21) and which has no further function.
8. Household microwave appliance (1) according to one of the preceding claims, wherein the evaluating circuit (10; 21) is integrated into a control facility (9) of the household microwave appliance (1).
9. Household microwave appliance (1) according to claim 8, wherein the evaluating circuit (10; 21) is connected to the at least one antenna line (11) via at least one conductor track (17) of a circuit board (14) of the control facility (9).
10. Household microwave appliance (1) according to one of claims 8 or 9, wherein the evaluating 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).
11. Household microwave appliance (1) according to claim 10, wherein the high-pass filter (19, 20) in addition has an ohmic resistor (20) that is connected to the coupling capacitor (19), and the coupling capacitor (19) has a capacitance value C of the magnitude $$C=\frac{1}{2\cdot \pi \cdot R\cdot f_u}$$

    

    with R the resistance value of the ohmic resistor (20) and f_u a lower cutoff frequency of the high-pass filter (19, 20).
12. Household microwave appliance (1) according to one of the preceding claims, wherein the household microwave appliance (1) is configured so as to trigger at least one action based on a strength of the microwave-induced alternating current in at least one antenna line (11).
13. Method for operating a household microwave appliance (1) according to one of the preceding claims, characterised in that electrical useful signals are transmitted via at least one antenna line (11) to and/or from at least one functional unit (8) of the household microwave appliance (1) and microwave-induced alternating currents are tapped from this at least one antenna line (11) and evaluated.

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