Core temperature sensor and system equipped with a core temperature sensor

Abstract

The present invention relates to a core temperature sensor (1), comprising a temperature measuring device (3) equipped with at least one temperature sensor (9), and a signal transmission antenna (2) connected to the temperature measuring device (3) via a coaxial line (4), wherein temperature information calculated by at least one temperature measuring device (3) can be transmitted via the signal transmission antenna (2) at a signal transmission frequency different from the microwave frequency, and the coaxial line (4) has at least one line resonant element (11a, 11b, 12) tuned to the microwave frequency, and conductive small plates (14a to 14d) are provided at at least one interface of at least one such line resonant element (11a, 11b), and the small plates (14a to 14d) are electrically connected to an internal conductor (5) or an external conductor (6) of the coaxial line (4). The present invention also relates to microwave cooking equipment and systems equipped with a signal transmission antenna. The present invention is particularly advantageous as it is configured to work in cooperation with a core temperature sensor and is applicable to an oven further having a microwave function unit.

Description

[Technical Field]

[0001] The present invention relates to a core temperature sensor comprising at least one temperature sensor and a signal transmission antenna connected to the at least one temperature sensor, wherein temperature information calculated by the at least one temperature sensor can be transmitted via the signal transmission antenna at a signal transmission frequency different from the microwave frequency, the at least one temperature sensor is connected to the signal transmission antenna via a coaxial line, and the coaxial line has at least one line resonant element tuned to the microwave frequency. The present invention further relates to a microwave cooking appliance having a cooking space that can be irradiated using microwaves of a set microwave frequency, comprising a signal transmission antenna that transmits signals at a signal transmission frequency different from the microwave frequency, and a signal section that is conducted particularly through the oven wall, wherein the signal section is a coaxial line at least section by section, and the coaxial line has at least one line resonant element tuned to the microwave frequency. The present invention further relates to a system comprising a microwave cooking appliance and the above-described at least one core temperature sensor, wherein the system is configured to wirelessly transmit signals at a signal transmission frequency between the signal transmission antenna of the core temperature sensor and the signal transmission antenna of the microwave cooking appliance. The present invention is particularly advantageous as it is configured to work in cooperation with a core temperature sensor and is further applicable to ovens having a microwave function unit.

[0002] It is well known that in ovens that also have a microwave function section, the microwave energy input-coupled via the signal transmission antenna of the core temperature sensor may impair the operation of components connected to the signal transmission antenna, such as temperature sensors and electrical circuits, or even destroy these components.

[0003] International Publication No. 2017 / 029059 discloses a core temperature sensor. The core temperature sensor here comprises at least one temperature sensor and a signal transmission antenna connected to this temperature sensor, wherein temperature information calculated by at least one temperature sensor can be transmitted via the signal transmission antenna at a signal transmission frequency different from the microwave frequency, and the at least one temperature sensor is connected to the signal transmission antenna via a coaxial line, the coaxial line having at least one lambda (λ) / 4 line resonant element tuned to the microwave frequency. Furthermore, a microwave cooking apparatus having a cooking space that can be irradiated using microwaves is disclosed. The microwave cooking apparatus here comprises a signal transmission antenna positioned in the cooking space to transmit signals at a signal transmission frequency different from the microwave frequency, and a signal line conducted through the oven wall, in which case the signal line is a coaxial line having at least one λ / 4 line resonant element tuned to the microwave frequency, at least in each section. The system described in the document can wirelessly transmit signals at a signal transmission frequency between the signal transmission antenna of a core temperature sensor and the signal transmission antenna of a microwave cooking device.

[0004] European Patent No. 1757862 discloses an oven for cooking food, comprising: a cooking space accessible through an oven door; means configured to generate and radiate microwaves propagating into the cooking space; control means configured to process signals received from an external source; microwave generating and radiating means that control operation depending on signals received from an external source; and a movable temperature sensor comprising a plurality of temperature sensors configured to be inserted into food placed in the cooking space of the oven and distributed toward each other at predetermined intervals along a movable sensor, wherein the sensors are electrically connected to the control means to supply signals from an external source, the control means is configured to receive temperature control signals arriving from predetermined sensors and to modify the operation of the microwave generating and radiating means when it is detected that the temperature control signals have reached a predetermined value, the control means is configured to receive and compare signals related to the temperature detected by the sensors, identify the signal corresponding to the highest temperature, select and use it as the temperature control signal at that time to be compared with a predetermined temperature value, thereby modifying the operating mode according to the microwave generating and radiating means. The problem of undesirable input coupling of microwaves to current circuits is not discussed.

[0005] European Patent Application Publication No. 2163823 relates to a cooking process sensor for a cooking appliance that cooks food, having a tip and a grip and at least one temperature sensor that are at least partially insertable into the cooking appliance, the output data of at least one first temperature sensor being available for adjusting at least one microwave source of the cooking appliance, and the first temperature sensor being surrounded by a microwave-absorbing material, and to a cooking appliance equipped with the cooking process sensor. However, such shielding is practically impractical for a signal transmission antenna.

[0006] German Patent Application Publication No. 2935282 discloses a temperature measurement device that wirelessly monitors the temperature of an object using a passively excitable temperature sensor, and a transceiver unit that externally excites electromagnetic waves as information carrier waves for the temperature of the object each time. A throttle device for preventing microwave signals from entering the internal space of the temperature sensor is also disclosed. The position and structure of the throttle device are not described in detail.

[0007] The problem of the present invention is to at least partially overcome the drawbacks of the prior art and particularly effectively protect the constituent elements of the core temperature sensor from microwave signals radiated into the cooking space of a microwave cooking device and input-coupled via a signal transmission antenna, and to provide a particularly compact, robust, and low-cost means.

[0008] The above problem is solved by the features described in the independent claims. Preferred embodiments are obtained particularly from each dependent claim.

[0009] The above problem is solved by a core temperature sensor comprising a temperature measurement device having at least one temperature sensor and a signal transmission antenna connected to the temperature measurement device via a coaxial line, wherein temperature information calculated by at least one temperature measurement device can be transmitted via the signal transmission antenna at a (data) signal transmission frequency different from the microwave frequency, the coaxial line has at least one line resonance element adjusted to the microwave frequency, a conductive small plate is provided on at least one interface of at least one such line resonance element, and the small plate is electrically connected to the inner conductor or the outer conductor of the coaxial line.

[0010] The conductive small plate creates at least one additional abutment point along the coaxial line in the microwave path in a space-saving, robust, and low-cost manner, and based on the resulting impedance discontinuity, the risk of microwave signals reaching the electrical and / or electronic components of the core temperature sensor, such as temperature sensors, integrated circuits, resistors, coils, capacitances, etc., from the outside via the signal transmission antenna is particularly effectively prevented. In this way, the core temperature sensor or its interior is particularly resistant to microwave interference.

[0011] Furthermore, this enables not only passive signal processing but also active signal processing and signal formation, particularly in core temperature sensors, without the risk of significant signal interference or even circuit damage or destruction.

[0012] Since core temperature sensors can be used even in cooking appliances that do not have a microwave function, for example, regardless of whether or not they have a steam cooking function, users do not need to pay attention to which appliance uses which core temperature sensor.

[0013] A core temperature sensor may also be called a food thermometer or puncture thermometer. It may have, in particular, a forward puncture or needle-shaped portion ("measuring section") inserted into the food being cooked to be monitored, and a gripping portion following behind the measuring section. At least one temperature sensor may be located within the measuring section. If there are multiple temperature sensors, these multiple temperature sensors can be arranged in a longitudinal line within the measuring section. The measuring section may have a hollow cylindrical sleeve (e.g., made of metal or ceramic, especially special steel) whose front end is pointed but closed, and which houses at least one temperature sensor. The core temperature sensor can generally be configured to conduct at least one ("temperature") signal via a coaxial line to a signal transmission antenna for wireless transmission at a signal frequency, where the temperature signal has at least one piece of temperature information calculated using at least one temperature sensor and optionally processed by a corresponding temperature measuring device. Generally, data signals can be received at the signal frequency via a signal transmission antenna, and therefore, in one advanced form, it can be configured as a combined transmitting and receiving antenna.

[0014] The signal transmission antenna can be positioned within the gripping portion or protrude from the gripping portion.

[0015] The core temperature sensor is configured for wireless signal transmission based on its signal transmission antenna. This offers the advantage that the food to be cooked can only be introduced into the cooking appliance after the user has already inserted the core temperature sensor into the food. In the case of wireless signal transmission, the advantages of avoiding through-holes for cable terminals in the oven and related drawbacks, such as microwave leakage radiation, steam leakage, hot air leakage, and oxidation of contact transition parts, are avoided.

[0016] The microwave frequencies most frequently used are in the range of 2.4 GHz to 2.5 GHz, for example, 2.45 GHz. However, the use of microwave frequencies in the range of 902 MHz to 928 MHz is also known. The coaxial line having at least one line resonant element tuned to a microwave frequency includes, in particular, that the line resonant element is tuned for a specific microwave frequency or a specific microwave frequency band, and therefore the core temperature sensor is provided for use in a microwave cooking appliance that uses microwaves having that frequency.

[0017] The signal frequencies most commonly used are in the range of 433.05 MHz to 434.79 MHz. These ISM bands are advantageous because they allow for data or information transmission using widely available and low-cost data transmission components. However, other frequency bands are also usable, such as the ranges of 13.553 MHz to 13.567 MHz, 26.957 MHz to 27.283 MHz, 40.66 MHz to 40.70 MHz, 863 MHz to 870 MHz, and 902 MHz to 928 MHz (if not used for microwaves). Other bands for signal frequencies are also usable, albeit potentially with adjustment difficulties, if they are not arbitrarily available frequencies within the ISM band.

[0018] A coaxial line basically has an inner conductor and an outer conductor, as is well known. The volume between the inner and outer conductors consists of or contains a non-conductive or insulating material, as is common for coaxial lines. The material here may be solid or gaseous. If the volume is filled with a solid material, or if the volume consists of a solid material, the solid can exist as a solid and in this case may also be called an "insulator". The use of an insulator is particularly advantageous for providing a resonant line section with a high dielectric constant or relative dielectric constant. The insulator can be a compact insulator in the sense that it has little or no porosity. In one developmental form, the insulator may be a pre-formed part.

[0019] Microwave and data signals operate along a coaxial line. In one advanced form, the coaxial line has an inner conductor formed from wire pieces and an outer conductor formed from a conductive sleeve, particularly a metal sleeve, in which case the metal sleeve also forms the sleeve of the measurement section at least for each section. In particular, the outer conductor has the shape of a cylindrical tube with a defined inner diameter. The wire pieces, in particular, are parallel to the metal sleeve and extend through the center of the metal sleeve and have a defined diameter. The wire pieces may have a circular cross-section. The wire pieces may be, for example, copper wires. The wire pieces can also be further formed as signal transmission antennas, so that one section of a wire forms a signal transmission antenna and the other section of the wire forms a wire piece of the coaxial line. The outer conductor, particularly the outer conductor in the form of a metal sleeve, is advantageously made of special steel because the outer conductor is resistant and low cost.

[0020] A line resonant element tuned to microwave frequencies corresponds in particular to a section of a coaxial line having a defined length along the coaxial line, tuned to microwave frequencies or microwave wavelengths. The relative dielectric constant ε of the material present between the inner and outer conductors. rThe relative dielectric constants ε of adjacent materials are different. r As the signal transitions, an impedance discontinuity occurs at the transition point due to the interaction with the length of the transmission line resonant element. In other words, the transmission line resonant element has different relative dielectric constants ε with respect to microwaves at its interface. r Adjacent sections of a coaxial transmission line, particularly adjacent transmission line resonators, are in contact with each other. The transmission line resonators introduce a matching error depending on the purpose, and this matching error creates an impedance discontinuity at the interface (also called the "butt joint"). This discontinuity causes most of the microwaves to be reflected back as intended. The relative permittivity at the interface is ε. r The greater the difference, the higher the reflectivity tends to be. A section of a coaxial transmission line having a transmission line resonator can also be called a resonant transmission line or resonant transmission line section. Transmission line resonator and resonant transmission line section can be used synonymously unless the context indicates otherwise.

[0021] In one developmental form, the volume between the inner and outer conductors is hollow cylindrical, in which case the inner conductor passes through the center of the volume. In this case, the interface corresponds to the bottom surface of the hollow cylinder. A particularly effective developmental form is one in which the outer sheath of the tubular volume reaches the outer conductor, or if that is not possible, reaches as close to the outer conductor as possible. Another particularly effective developmental form is one in which the inner surface of the volume reaches the inner conductor, or if that is not possible, reaches as close to the inner conductor as possible. Here, the spacing or gap dimension is only a few tenths of a millimeter in one developmental form.

[0022] In one developmental form, the non-conductive volume is made of industrial ceramic, or the volume is filled with industrial ceramic, or the volume contains at least ceramic. Ceramics have the advantage of having high thermal, mechanical, and chemical resistance. Furthermore, ceramic bodies containing highly electrically insulating ceramic materials can be used. Possible industrial ceramics have a typical relative dielectric constant ε in the range of 6 to 15, for example. r Aluminum oxide Al2O3 or typical relative dielectric constant ε in the range of 20-40 r It may be zirconium dioxide ZrO2 having [a certain property]. Alternatively, glass or glass ceramic may be used as the material. A resonant line filled with ceramic may also be called a "ceramic line". In another development using an insulator between the inner and outer conductors, it is advantageous that a very small tolerance should be maintained. The gap between the inner and outer conductors should be advantageously reduced to a minimum. Microwaves input-coupled via the signal transmission antenna are reflected at least partially at the interface of the insulator facing the signal transmission antenna, because the insulator creates an impedance discontinuity at that point based, for example, on the transition from air to the insulating material. Some of the microwaves that are not reflected at the above point and continue to travel along the coaxial line along the insulator encounter another impedance discontinuity at the interface of the insulator opposite to the signal transmission antenna, and are therefore reflected back to the signal transmission antenna at least partially. In contrast, radio signals pass through with virtually no loss.

[0023] In one evolved form, the non-conductive volume between the inner and outer conductors of at least one line resonant element is air (ε r This consists of (=1). This is particularly advantageous for providing a line resonant element or resonant line section with a low dielectric constant or a low relative dielectric constant. The use of air, in particular, allows for a particularly inexpensive and simple structure. A resonant line filled with air can also be called an "air line".

[0024] That the coaxial line has at least one line resonance element adjusted to microwave frequencies can include that the coaxial line has exactly one line resonance element adjusted to microwave frequencies, or that the coaxial line has a plurality of line resonance elements arranged in series along its extension direction. In an advantageous development for strong attenuation or filtering of micro - waves along the coaxial line, in particular high impedance discontinuities arise, so that the line resonance elements connected in series have alternately high and low dielectric constants. For example, a glass line or ceramic line, an air line and another glass line or ceramic line can be arranged in this order. However, for example, as long as the relative dielectric constants are significantly different, a row having a plurality of resonant lines filled with solid substances and arranged adjacent to each other can also be used. For example, for two adjacent resonant lines, two ceramic lines having, for example, ε r = 6 or ε r = 40 can be provided with respective insulators having different relative dielectric constants.

[0025] The small plate is particularly perpendicular to the inner conductor, that is, its normal vector is oriented parallel to the inner conductor, or its main surface is oriented perpendicular to the inner conductor. In one development, the conductive small plate is formed in the form of a perforated disk. In particular, the small plate can be placed on the bottom surface of the hollow cylinder of the line resonance element adjacent along the coaxial line on one of its bottom surfaces. In particular, the conductive small plate can completely cover the bottom surface of the hollow cylinder.

[0026] In one configuration, the conductive small plate is a metal small plate. This is particularly inexpensive and advantageously has high conductivity. The metal can be, for example, copper, silver, brass, aluminum or alloys thereof. Alternatively, the conductive small plate can be a ceramic small plate made of a ceramic having good conductivity.

[0027] In one configuration, the thickness of the small plate is less than 10% of the microwave wavelength, particularly less than 5%, and especially less than 2%. This thickness can also be referred to as "thickness" or "length" relative to the microwave propagation direction. Because the length of the small plate or the corresponding coaxial "small plate" is short compared to the microwave wavelength, it is advantageous that impedance transformation does not need to be considered, and only the impedance discontinuity that occurs between different coaxial line impedances needs to be considered. In other words, the actual impedance of the small plate can be used directly to determine the reflection coefficient at the abutment point between the small plate and at least one line resonant element in contact with it. This significantly simplifies the design of the coaxial line.

[0028] In one configuration, at least one line resonator is a lambda(λ) / 2 line resonator. Its length corresponds to half a wavelength or several times that of microwave radiation, taking into account its relative dielectric constant. A λ / 2 line resonator can generally have a length of λ / 2 or generally λ / 2 + n·λ / 2 [n=0,1,2,3,…].

[0029] In one configuration, at least one line resonator is a λ / 4 line resonator. Its length corresponds to one-quarter wavelength of microwave radiation, taking into account its relative dielectric constant. A λ / 4 line resonator can generally have a length of λ / 4 or generally λ / 4 + n·λ / 2 [n=0,1,2,3,…].

[0030] In the case of multiple line resonators, in one development, all line resonators can be λ / 4 line resonators. In another development, all line resonators may be λ / 2 line resonators. However, generally, the type, number, and arrangement of each of the multiple line resonators are basically arbitrary; for example, at least one λ / 4 line resonator can be provided together with at least one λ / 2 line resonator. The number of line resonators may depend, for example, on the desired reflectivity of the structure, the achievable quality, and the target compactness. For example, a column sequence of three λ / 4 line resonators can be used, or a column sequence of one λ / 4 line resonator and one λ / 2 line resonator can be used. The latter development is particularly advantageous because it achieves a high filtering effect, especially a high filtering effect equivalent to that of three λ / 4 line resonators, but with less manufacturing and assembly effort, and the overall length of the line resonators can be shortened.

[0031] In one configuration, the coaxial line has an inner conductor formed from wire pieces and an outer conductor formed from a metal sleeve, and at least one line resonant element has a hollow cylindrical insulator, particularly a ceramic one, fitted over the inner conductor and extending radially to or nearly to the outer conductor. Such a device can be realized particularly robustly and at low cost and is easily assembled. Furthermore, the insulator can be constructed particularly compactly and geometrically particularly simply.

[0032] In one configuration, the insulating material has a dielectric constant ε in the range of 6 to 40. r This material has the advantage of providing high impedance discontinuities. Furthermore, it is advantageous that short material lengths can be achieved using such low-cost materials.

[0033] In one configuration, the insulating material has a thermal conductivity κ of at least 20 W / (m·K), which allows the insulator to advantageously function as an effective thermal bridge between the inner and outer conductors. This further allows the microwave energy converted into heat in the line resonant element to be effectively dissipated to the outer conductor, which is at least section by section at the temperature of the food being cooked. For example, aluminum oxide is suitable as the insulating material.

[0034] In one configuration, the coaxial line has two spaced-apart line resonators made of ceramic or glass, with an air section formed between them as a resonant line. This structure is advantageously compact and significantly attenuates microwaves. The configuration here can further be expressed as having an insulator made of ceramic or glass separated from each other by an air-filled line resonator or air line, or having two line resonators spaced apart by an air line with an air section formed between them as a resonant line. Generally, the insulator itself or the section of the coaxial line that forms the line resonance can be referred to as or considered as a line resonator.

[0035] In one advanced form, the core temperature sensor has a substrate connected to an internal conductor, and the substrate is provided with a freewheeling conductor path (a so-called "λ / 4 stub") electrically connected to the internal conductor and having an arbitrary length of λ / 4 along its extension. The λ / 4 stub is open (particularly unconnected and therefore idle), causing freewheeling at its free end, which is converted into a short circuit at the contact point. This is advantageous as it allows for further back reflection of the microwave signal in the substrate. The wavy extension of the λ / 4 stub is advantageous as it allows for a particularly compact structure, especially a short longitudinal section of the core temperature sensor. The wavy extension may be, for example, sinusoidal or meander-shaped. The λ / 4 stub may also have a curved and rolled extension.

[0036] The substrate may be made of, for example, ceramic or circuit board material, such as FR4 or polyimide. The substrate is clampable, crushable, and / or solderable to the internal conductor at the corresponding contact or contact point. From the contact, in addition to the λ / 4 stub, at least one other ("connecting") conductive path on the substrate leads to a temperature measuring device and is electrically connected to the internal conductor via the contact. The conductive path may be, for example, a copper conductive path.

[0037] The recess can be filled with metal, especially copper. The internal conductor, if present in the form of a wire piece, can be press-fitted into the recess and soldered to the conductor path at that location. However, the contact connection between the internal conductor and the substrate can also be achieved in another form, for example, without a recess, by simple soldering.

[0038] In one advanced form, which is particularly advantageous for achieving a compact structural form, the λ / 4 stub is positioned on the side of the substrate opposite to the side on which at least one temperature sensor is located. The temperature measuring device, and in particular at least one of its temperature sensors, can be electrically connected to an internal conductor located, for example, in the conductor path of an HF short circuit. The temperature measuring device, and in particular at least one of its temperature sensors, can form a common node with the internal conductor together with the conductor path.

[0039] In one advanced form, the temperature measuring device has at least one temperature sensor attached to a substrate. In another advanced form, the temperature measuring device additionally has one or more components attached to the substrate, which perform processing of the measurement signal formed by the at least one temperature sensor, such as digitization, filtering, etc. Alternatively, at least one temperature sensor and / or at least one component can be connected to the substrate via at least one electrical line.

[0040] In one developmental form, the temperature measuring device is a passive temperature measuring device, that is, it receives energy for its operation from an externally generated query signal. Such a temperature measuring device can be constructed particularly robustly and at low cost.

[0041] In one developmental form, the temperature measuring device is a surface wave (OFW) temperature measuring device. In this case, at least one temperature sensor is a surface wave temperature sensor, and the substrate is preferably a ceramic substrate. As a further optional component, for example, a surface wave filter can be included. Using a surface wave temperature sensor made of ceramic, especially together with the substrate, provides the advantage that the temperature measuring device has high heat resistance (e.g., up to over 200°C) and is robust. The surface wave temperature measuring device can be used to form a passive, remotely readable temperature sensor, for example, in the form of a wirelessly readable transponder.

[0042] In one advanced form, the temperature measuring device is an electrically driven (non-surface wave) temperature measuring device. The temperature measuring device may include, for example, at least one electrically driven temperature sensor, such as an NTC element or a Pt thermocouple or PtRh thermocouple. The temperature measuring device may additionally have one or more electrical and / or electronic components, which perform, for example, processing of the measurement signal formed by at least one temperature sensor, such as digitization, filtering, and formatting. The substrate may also be a ceramic substrate or an FR4 substrate.

[0043] An electrically driven temperature measuring device may be a passive temperature measuring device.

[0044] Basically, the temperature measuring device may be an active or actively operable temperature measuring device having at least one electrical energy store and at least one electrical or electronic component that can be supplied from the energy store, and in particular capable of independently forming at least one temperature signal. Such components may include, for example, at least one microcontroller, amplifier, filter, resistor, capacitance, inductance and / or bipolar transistor or field-effect transistor. The actively operable circuit enables active signal processing and signal formation, particularly in the core temperature sensor. The basic method of active signal processing and information transmission extended by digital data processing, for example by a microcontroller, has the advantage that, on the one hand, information can be exchanged bidirectionally, and on the other hand, it can be adapted or improved during the manufacturing phase or, in special cases, during the product run-time at the customer through software updates. The electrical energy store may be a rechargeable battery, a non-rechargeable battery, a supercapacitor, etc. The energy store can be placed on or alongside the substrate.

[0045] It is also possible to use a temperature measuring device that combines surface wave elements and non-surface wave elements.

[0046] In one advanced form, at least several constituent elements exist as SMD components, which enables particularly simple implementation.

[0047] In one advanced configuration, at least one microwave filter composed of conventional electrical or electronic components is placed on a substrate. In this case, the advantage is that the incoming microwave energy is already sufficiently small to no longer damage the conventional components. The microwave filter has transparency to the signal transmission frequency, for example, in the 433 MHz range. Making the microwave filter a passive microwave filter is an advantageous and particularly easily achievable advanced configuration. The microwave filter may be a single-stage or multi-stage microwave filter.

[0048] In one advanced form, when the signal transmission frequency is lower than the microwave frequency, the microwave filter is a low-pass filter. This can be realized particularly easily when its constituent elements exist as discrete SMD components. The low-pass filter can be configured as, for example, an LC low-pass filter, an RL low-pass filter, an RCL low-pass filter, or a surface wave filter.

[0049] The microwave filter is provided particularly between the internal conductor and the rest of the circuitry on the substrate (e.g., a temperature measuring device comprising at least one temperature sensor and optionally an active circuit), thereby advantageously providing further protection of the rest of the circuitry from microwaves.

[0050] In one configuration, the antenna is configured to minimize its return loss at microwave frequencies; that is, it is adapted to accept only the smallest possible microwave output. This adaptation can be achieved by corresponding adjustments to the length, diameter, and / or shape of the antenna, depending on its mechanical configuration. These parameters, as in this case, determine the impedance that the antenna should "see" at the input side of the microwave filter.

[0051] In one configuration, the core temperature sensor or its outer conductor, particularly the sleeve, has, as a whole or in part, a coefficient of thermal expansion α that is significantly lower than that of air, but has a relative dielectric constant that is at least approximately equal to that of air.

number

[0052] In one configuration, at least one packing material has at least a thermal conductivity λ WThe material has at least two filling materials that differ significantly in this respect, with the outer conductor, particularly the sleeve, being filled section by section with one of the filling materials along its longitudinal extension, and the other filling material being filled section by section with one of the two filling materials. This provides the advantage that, depending on the components located in each section, the heat conduction can be adjusted to be particularly suitable for each section, for example, along the longitudinal extension and / or along the outer conductor.

[0053] For example, in the realm of temperature sensors, higher thermal conductivity from at least one temperature sensor to the external conductor is advantageous, allowing at least one temperature sensor to respond more quickly and accurately to ambient temperature or changes in ambient temperature. Higher thermal conductivity can also be advantageous in the realm of air lines, because the incident microwave power can be further reduced to reduce the heat generated by the filter itself.

[0054] In contrast, in the remaining sections of the substrate (outside at least one temperature sensor), it may be advantageous to reduce the thermal conductivity of the packing material to prevent the temperature sensors from thermally influencing each other, for example, by preventing a rear-side thermal short circuit between the temperature sensors. In other words, the temperature sensors should be well coupled to the local sleeve temperature but should not be located within a common rear-side "isothermal" heat plane. This is particularly advantageous when various temperature zones may be measured within the food being cooked, as this allows for extended food information to be obtained (e.g., via temperature gradients within the food being cooked), or for example, for detecting misinsertion. For example, in chicken, the tip of the core temperature sensor may penetrate into the hollow abdominal space, in which case the temperature information from the sensor tip will be inaccurate because it will indicate the ambient temperature rather than the temperature of the meat.

[0055] In one developmental form, the signal transmission antenna is embedded in or surrounded by a filler material. In this case, two properties of the filler material can be particularly important: on the one hand, a dielectric constant (e.g., ε in this case) that is significantly higher than that of air, allowing the dimensions of the antenna to be smaller than in the case of air filling. r ≥6) is important, and on the other hand, as an optional means, the probability of electrical dielectric breakdown should be kept low by a filler material having low ionizability or good electrical insulation properties. The specific configuration can be determined, for example, by experiment or simulation. The signal transmission antenna and filler material can be housed, for example, in a non-conductive sleeve of the core temperature sensor, for example, in a plastic sleeve. The filler material can be provided as an integrated body.

[0056] The above problems can also be solved by a microwave cooking appliance having a cooking space that can be irradiated using microwaves of a set microwave frequency, wherein the cooking space has a signal transmission antenna for transmitting signals at a signal transmission frequency different from the microwave frequency, and a signal section that is conducted particularly through the oven wall, in which case the signal section is a coaxial line for at least each section, and the coaxial line has at least one line resonant element or resonant line section tuned to the microwave frequency.

[0057] The coaxial line of a microwave cooking device may be formed in the same manner as the coaxial line of a microwave cooking device described in International Publication No. 2017 / 029059, and can be improved in particular in the same way as the coaxial line of the core temperature sensor described above. A microwave cooking device equipped with such a coaxial line formed as an antenna lead offers the same advantages as the coaxial line of a core temperature sensor.

[0058] In one developmental form, the microwave cooking appliance is a household appliance, particularly a kitchen appliance. In another developmental form, the microwave cooking appliance is a standalone microwave cooking appliance. In yet another developmental form, the microwave cooking appliance is a combination device of a microwave / oven appliance, for example, an oven with a microwave function unit incorporated into it. The cooking appliance may further have a steam cooking function unit. The microwave cooking appliance may have a magnetron or a semiconductor-based microwave generator to generate microwaves.

[0059] The above problems are further solved by a system comprising the microwave cooking device described above and at least one core temperature sensor described above, wherein the system is configured to wirelessly transmit signals at a signal transmission frequency between the signal transmission antenna of the core temperature sensor and the signal transmission antenna of the microwave cooking device. The system can be configured similarly to the core temperature sensor and / or microwave cooking device, and vice versa, yielding the same advantages.

[0060] In one developmental form, the system can perform the following operations:

[0061] For food to be processed within the cooking space of a microwave cooking appliance, such as a block of meat, the core temperature should be monitored so that the microwave cooking appliance can control the cooking operation based on the core temperature. For example, the microwave cooking appliance can terminate the cooking operation when a specific core temperature is reached, or when a set duration has elapsed at a temperature above a specific core temperature. A microwave cooking appliance is, for example, an oven with an additional microwave function, which allows food to be processed alternately or simultaneously by electric oven heating elements, such as an air circulation heater, a high-temperature heating radiator, a low-temperature heating radiator, etc., and microwaves. To monitor the core temperature, a needle-shaped section of a core temperature sensor, equipped with multiple temperature sensors arranged in series, is inserted into the food. The rear gripping portion of the core temperature sensor is located outside the food.

[0062] The core temperature sensor can be remotely queryed wirelessly (particularly via radio) from the microwave cooking equipment. For this purpose, the microwave cooking equipment has a signal transmission antenna that is at least partially located within the cooking space, and can use this antenna to radiate an excitation radio signal (e.g., in the 433 MHz frequency band) into the cooking space. The excitation radio signal can always be radiated, for example, when the microwave cooking equipment requires temperature information for operation, for example, when it has a core temperature value that can be measured or detected by the temperature sensor.

[0063] The excitation radio signal is received via a signal transmission antenna of a core temperature sensor, which is tuned to a transmission frequency of approximately 433 MHz. The received excitation radio signal is transmitted via a coaxial line to, for example, a passively excitable surface wave temperature measuring device. The surface wave temperature measuring device has a substrate made of, for example, ceramic or FR4, and at least one surface wave temperature sensor is provided on the surface of the substrate. The surface wave temperature sensor can be understood as a part of the surface wave temperature measuring device. The excitation radio signal passively excites at least one surface wave temperature sensor to form an information signal containing the queried core temperature value and conduct it to the signal transmission antenna. The information signal is radiated from the signal transmission antenna of the core temperature sensor into the cooking space (particularly in the 433 MHz-ISM frequency band) and received by the signal transmission antenna of the microwave cooking equipment. The received information signal is conducted via a coaxial line through the cooking space wall to a receiving circuit, where the information signal is processed for use in the cooking equipment. Alternatively, a passive non-surface wave temperature measuring device or an active temperature measuring device can be used.

[0064] For this purpose, the cooking appliance may have, for example, an independent evaluation circuit connected to a central control unit. Alternatively, the central control unit may function as the evaluation circuit.

[0065] Microwave cooking equipment may have a combination device of a wireless transmitting circuit / wireless receiving circuit in particular for forming an excitation wireless signal and processing an information signal. This circuit can be connected, for example, to a central control unit of the microwave cooking equipment.

[0066] The signal transmission antennas for core temperature sensors and microwave cooking equipment are tuned to fit the 433 MHz-ISM frequency band and are intentionally designed to have poor coupling in the microwave frequency range (e.g., 2.45 GHz). However, based on the high microwave power output up to approximately 1000 W, the input coupling of microwave signals to the signal transmission antenna becomes extremely strong, which can result in damage or even complete destruction of structures connected to the signal transmission antenna. The coaxial lines described above are provided to render these input-coupled microwave signals substantially harmless.

[0067] The above-mentioned characteristics, features, and advantages of the present invention, as well as the methods by which they are achieved, will be more clearly and distinctly understood in connection with the following schematic description of embodiments, which will be described in detail with reference to the drawings. [Brief explanation of the drawing]

[0068] [Figure 1] This is a schematic, not-to-scale, top cross-sectional view showing a core temperature sensor according to several possible embodiments.

[0069] Figure 1 shows a cross-sectional plan view of a core temperature sensor 1, which includes a signal transmission antenna 2, an exemplary temperature measuring device of a surface wave temperature measuring device 3, and a coaxial line 4 connecting the signal transmission antenna 2 and the surface wave temperature measuring device 3.

[0070] The signal transmission antenna 2 is formed as a wound antenna manufactured from copper wire, and this wound antenna transitions into a straight inner conductor 5 of the coaxial line 4, which is also made of copper wire. The signal transmission antenna 2 and the inner conductor 5 can be manufactured as a single unit from a single wire piece. The outer conductor 6 of the coaxial line 4 in this case consists of, for example, a hollow cylindrical special steel sleeve 7, which extends longitudinally beyond the surface wave temperature measuring device 3 and further to its tip, sometimes changing its cross-sectional shape, thereby allowing the special steel sleeve 7 to be inserted into food. The special steel sleeve 7 is sometimes referred to as needle-shaped. A gripping portion is also provided, but is not shown. The special steel sleeve 7 may have an elliptical or rectangular cross-section.

[0071] The surface wave temperature measuring device 3 has a ceramic substrate 8 or an FR4 substrate 8, and one or more surface wave temperature sensors 9 are arranged on the upper surface of the ceramic substrate 8. In particular, the surface wave temperature sensors 9 can be soldered onto the substrate 8. The surface wave temperature sensors 9 can be SMD components. The internal conductor 5 is inserted at its end face into, for example, a slit-shaped recess 10 of the substrate 8, and can be press-fitted or soldered at that location. The surface wave temperature sensor 9 is electrically connected to the internal conductor 5 via a conductive path (see above) provided on the substrate 8. In this case, the special steel sleeve 7 is also used as a shield to prevent the surface wave temperature measuring device 3 from being directly irradiated by radio and microwave radiation. At least the section of the special steel sleeve 7 including the surface wave temperature sensor 9 may also be referred to as the measuring section.

[0072] The surface wave temperature measuring device 3 can be excited in the 433 MHz-ISM band via a radio excitation signal. The radio excitation signal is input-coupled via a signal transmission antenna 2 designed for this purpose and conducted through a coaxial line 4 to the surface wave temperature measuring device 3 with low loss, or even no practical loss. The radio excitation signal excites the surface wave temperature sensor 9 so that the modified radio signal is formed as a temperature signal, which is then conducted back to the signal transmission antenna 2 through the coaxial line 4 and radiated by the signal transmission antenna 2. The converted radio signal contains (temperature) information calculated by at least one surface wave temperature sensor 9. The core temperature sensor 1 is typically inserted into the food to a depth that allows at least one surface wave temperature sensor 9 to be inserted into the food and thus measure a temperature value corresponding to the core temperature of the food with sufficient accuracy.

[0073] To prevent the microwave signal or microwave energy coupled via the signal transmission antenna 2 from damaging or destroying the surface wave temperature measuring device 3, the signal transmission antenna 2 can be configured such that its reflection attenuation at microwave frequencies is as small as possible, thereby receiving as little microwave output as possible. The signal transmission antenna 2 configured in this way can also be considered as an arbitrary "first" filter stage F1 with respect to the incident microwaves.

[0074] For the same purpose, a "second" filter stage F2 having at least one line resonant element is provided between the signal transmission antenna 2 and the surface wave temperature measuring device 3 or its substrate 8, and here it has two line resonant elements in the form of hollow cylindrical ceramic tubes 11a and 11b spaced apart along the inner conductor 5 and adapted to the microwave frequency to be filtered. For this purpose the wire-like inner conductor 5 is guided through the internal hollow chambers of the ceramic tubes 11a and 11b. Ideally, the ceramic tubes 11a and 11b each completely fill the space radially between the inner conductor 5 and the outer conductor 6, i.e., fully up to the outer conductor 6. If only an annular gap insertion is possible, it is desirable to make the gap between the outer conductor 6 and the ceramic tubes 11a and 11b, and the gap between the inner conductor 5 and the ceramic tubes 11a and 11b, as small as possible.

[0075] Ceramic materials have a dielectric constant ε in the range of 6 to 40 (for example, 10). r It has, for example, aluminum oxide Al2O3 (typically ε in the range of 6 to 15) r ) or zirconium dioxide ZrO2 (typically with an ε in the range of 20-40) r ) may consist of.

[0076] The ceramic tubes 11a and 11b, in this example, filter the wavelength λ of microwave radiation in the ceramic material. Ker It has a length of 1 / 4 of the length, for example about 10 mm, and is therefore formed as a λ / 4 line resonant element. The two ceramic small tubes 11a and 11b are spaced apart from each other along the internal conductor 5 in this case λ Luft / 4(where λ Luft (where λ is the wavelength of microwave radiation in the air), for example, they have a spacing of about 30 mm. This allows the coaxial line 4 between the ceramic tubes 11a and 11b to have a length of λ LuftA so-called air line 12 for λ / 4 microwaves is formed. The air line 12 acts as a λ / 4 line resonator or λ / 4 line resonant element. That is, the second filter stage F2 has three λ / 4 line resonant elements 11a, 12, and 11b connected in series, and these elements alternately have high relative permittivity (ceramic) and low relative permittivity (air).

[0077] Therefore, in a particularly simple embodiment without components 14a to 14d, in the section used as the second filter stage F2 of the coaxial line 4, starting from the signal transmission antenna 2, a first transition from air to ceramic tube 11a exists at the antenna-side end face of ceramic tube 11a. This transition, where an impedance discontinuity occurs, corresponds to an HF freewheeling section for microwaves. On the end face of ceramic tube 11a opposite to the signal transmission antenna 2, an HF short circuit is formed by the impedance discontinuity at the transition from ceramic to air. Similar to the first ceramic tube 11a, the coaxial line 4 also has HF freewheeling for microwaves, where a first transition from air to ceramic tube 11b (i.e., at the antenna-side end face of ceramic tube 11b) exists, starting from the signal transmission antenna 2. Similarly, on the end face of ceramic tube 11b opposite to the signal transmission antenna 2, an HF short circuit can be formed by the transition from ceramic to air. Therefore, an impedance transformation of the microwave signal occurs at each end face of the two ceramic tubes 11a and 11b, and based on this impedance transformation, the microwave signal is significantly reflected and returned to the signal transmission antenna 2.

[0078] A particularly effective impedance transformation can be achieved when the air line 12 between the two ceramic tubes 11a and 11b is formed as a λ / 4 freewheeling line. The HF freewheeling section is realized by the reflection of forward-traveling waves, particularly due to a larger change in the impedance of the coaxial line 4. The reflected, backward-traveling waves overlap with the forward-traveling waves. Depending on the point of observation of the overlap in the coaxial line 4, phase-wise cancellation or reinforcement may occur. A particularly strong reflection occurs in the case of a λ / 4 line, where reflection at one end of the λ / 4 line (corresponding to the freewheeling section) results in complete cancellation on the input side of the λ / 4 line, i.e., the freewheeling is converted into a short circuit. In the case of a short circuit at the end of the line, this is reversed. The capacitance and inductance of the coaxial line 4 determine the impedance of the λ / 4 line and, consequently, the magnitude of the reflection coefficient. The location where the impedance discontinuity occurs can also be called a "butt point".

[0079] Alternatively, one, two, or all three of the line resonant elements 11a, 12, and 11b can be formed as λ / 2 line resonant elements.

[0080] The "third" filter stage F3 can be provided by a conductor path 13, for example, made of copper, which is attached to the substrate 8, particularly at the rear. The conductor path 13 and the surface wave temperature sensor 9 are located, in particular, on different flat surfaces of the substrate 8. The conductor path 13 is connected to, for example, a slit-shaped recess 10 of the substrate 8, and thus to the end of the internal conductor 5 at that location. For further blocking or filtering of the microwave signal, the conductor path 13 is configured as a λ / 4 freewheeling line or a λ / 4 stub. For this purpose, the conductor path 13 has a length of λ / 4 of the microwave to be filtered, depending on the dielectric constant of the substrate 8. Furthermore, the substrate-side end of the sensor element is open (i.e., not electrically connected), so that the freewheeling is converted into a short circuit to the input side of the coaxial line 4. To form space on the substrate 8, the freewheeling conductor path 13 has a rippled or wavy extending state, particularly a meandering extending state, in the extending direction.

[0081] The "fourth" filter stage F4 can be provided by the fact that the surface wave temperature measuring device 3 also has at least one microwave filter F4 constructed from conventional components (see above) in addition to the surface wave temperature sensor 9. This microwave filter can be configured in particular as a low-pass filter. In this case, the microwave energy arriving at the substrate 8 becomes extremely small, which is utilized as it no longer damages the conventional components.

[0082] Each filter stage F1-F4 can withstand high microwave power without being damaged, and also withstand the high ambient temperatures that occur inside the oven.

[0083] In embodiments where microwaves are attenuated particularly well or filtered particularly strongly, thin metal plates 14a to 14d are placed on the bottom surface used as the interface between the ceramic tubes 11a and 11b. The metal plates 14a to 14d may be made of, for example, copper, brass, or aluminum. The diameter D of the metal plates 14a to 14d is radial to the direction of extension of the internal conductor 5.pl Advantageously, the inner diameter D of the outer conductor 6 H and / or the diameter of the corresponding interface, in this case, for example, D pl Corresponds to =3.6mm. Thickness L of the metal small plates 14a~14d along the internal conductor 5. Pl This is significantly smaller than the wavelength of the microwaves to be filtered, for example, L Pl = 1.5 mm. Thickness L Pl This can also be referred to as "thickness" or "length" based on the direction of microwave propagation.

[0084] In one variant, the metal plates 14a to 14d are electrically connected to the internal conductor 5 but not to the external conductor 6. The gap or radial distance between the metal plates 14a to 14d and the external conductor 6 is small, for example, only a few tenths of a millimeter. In an alternative variant, at least one of the metal plates 14a to 14d is electrically connected only to the external conductor 6, and has an annular gap with respect to the internal conductor 5, for example, when metal plate 14a is also used as a terminal for the external conductor 6 to the antenna 2. The metal plates 14a to 14d add further abutting positions for microwaves on the flat surfaces of these metal plates 14a to 14d.

[0085] This can be demonstrated in the framework of one embodiment by considering the individual line sections 14a, 11a, 14b, 12, 14c, 11b and 14d as separate coaxial lines and calculating the impedance of these coaxial lines. In this case, the inner diameter of the special steel sleeve 7 used as the outer conductor 6 is D H Assume that = 4mm. Diameter D of the inner conductor 5. I D I = 1.5 mm.

[0086] Actual impedance R of coaxial air line 12 Luft teeth,

number

[0087] ε r Actual impedance R of coaxial ceramic transmission line 11a or 11b having a relative dielectric constant of 29 Ceram teeth,

number

[0088] Output impedance Z of a λ / 4 transmission line A,λ / 4 The line impedance Z L,λ / 4 and input impedance Z E,λ / 4 Tokara Z A,λ / 4 =( Z A,λ / 4 ) 2 / Z E,λ / 4 This can be determined according to the following. In contrast, for the output impedance of a λ / 2 line, Z A,λ / 4 = Z E,λ / 2 The following holds true. In a λ / 4 transmission line, the output impedance Z is A,λ / 4 The input impedance of the transmission line is Z. E,λ / 4 and the line impedance Z of the λ / 4 transmission line L,λ / 4 It depends on the input impedance of the line Z. E,λ / 2 and output impedance Z A,λ / 2 These have the same value. This means that the following physical quantity is deterministic regarding the effectiveness of these two line converters as microwave filters.

[0089] Basically, in a λ / 4 track, the track length L L,λ / 4 However, it corresponds to λ / 4, that is, 1 / 4 of the microwave wavelength, and in particular, it is possible that it corresponds depending on the propagation speed of electromagnetic waves on the transmission line. Output impedance Z A,λ / 4 The input impedance of the transmission line is Z. E,λ / 4 and the impedance Z of the track itself L,λ / 4 It depends on the and. In contrast, for a λ / 2 line, the length of the line L is basically L,λ / 2 However, it corresponds to λ / 2, that is, half the wavelength of a microwave, and in particular, it is possible that it corresponds depending on the propagation speed of electromagnetic waves on the transmission line. Output impedance ZLA,λ / 2 The input impedance of the transmission line is L E,λ / 2 It is equal to.

[0090] The diameter of the metal plates 14a to 14d is, for example, D Pl = 3.6 mm, and its thickness or length is L Pl If = 1.5mm, the actual impedance R of the corresponding coaxial "plate line" is Pl teeth,

number

[0091] Length L Pl For example, at a frequency of 2.45 GHz,

number

[0092] The entire coaxial filter strand F2 consists of different line components. On the one hand, the abutting positions for the microwave filtering function are obtained based on impedance discontinuities by impedance transducers in the form of λ / 4 and / or λ / 2 air lines and ceramic lines 11a, 11b, 12, and additionally, abutting positions are obtained based on impedance discontinuities in the metal plates 14a-14d.

[0093] All four filter stages F1 to F4 can achieve attenuation of, for example, 60 dB to 80 dB at a microwave frequency of 2.45 GHz. In contrast, at a frequency of 433 MHz, the data signal is attenuated by only 1 dB to 10 dB.

[0094] If a rapid temperature change occurs, the expansion characteristics of the air trapped inside the core temperature sensor 1 can cause damage such as microcracks, i.e., seal rupture at the end of the special steel sleeve 7 in the closing plate 14a. Therefore, it is advantageous to cast or foam-molde the core temperature sensor 1, either as a whole or in part, with fillers FS1 and FS2 that have a significantly lower coefficient of thermal expansion than air. Furthermore, fillers FS1 and FS2 have a low relative dielectric constant ε r It is desirable to have a relative permittivity ε close to 1 (equivalent to that of air) in the region of the air line 12. r This is advantageous. For example, as the fillers FS1 and FS2, foaming fillers that can withstand the temperature range in which they are used (e.g., up to 300°C) can be used.

[0095] Furthermore, the signal transmission antenna 2 can be embedded in the packing material (see above). The packing material is particularly desirable to satisfy the following criteria: on the one hand, that the packing material has a significantly higher dielectric constant than air (= is a material that can polarize well), thereby allowing the dimensions of the antenna to be smaller than those when filled with air; and on the other hand, that the packing material has low ionizability (= is an electrical insulator) to keep the probability of electrical dielectric breakdown low. Specific embodiments can be found, for example, by experiment or simulation to determine an appropriate combination of characteristics.

[0096] Furthermore, the filling material has an appropriate thermal conductivity λ WIt is desirable to have the following: In the region of the temperature sensor 9, a higher thermal conductivity between the special steel sleeve 7 and the temperature sensor 9 is advantageous, as this allows the temperature sensor 9 to be thermally coupled to the ambient temperature more effectively, and consequently to react more quickly and accurately to the ambient temperature or its changes. A higher thermal conductivity is also advantageous in the region of the air line 12, as this allows for more advantageous and effective cooling in that area. This is because, in this case, the microwave incident power must be further reduced in order to reduce the heat generated by the filter itself.

[0097] In the remaining area of ​​the substrate 8, it may be advantageous to reduce the thermal conductivity of the packing material to prevent the temperature sensors 9 from influencing each other, that is, to prevent thermal short circuits, for example, on the rear side, between each temperature sensor 9. In other words, the temperature sensors 9 should be well coupled to the local sleeve temperature, but should not be located within a common rear-side "isothermal" heat plane. This is particularly advantageous when various temperature zones may be measured within the food being cooked, as this allows for the acquisition of extended food information (e.g., via temperature gradients within the food being cooked) or, for example, the detection of misinsertion. For example, in chicken, the tip of the core temperature sensor may penetrate into the hollow abdominal space, in which case the temperature information will indicate the ambient temperature rather than the temperature of the meat, resulting in erroneous temperature information from the sensor tip.

[0098] These various requirements regarding the thermal conductivity of the filler material can be met by using two different filler materials FS1 and FS2, each having at least different thermal conductivity, for example, a first filler material FS1 having a relatively low thermal conductivity and a second filler material FS2 having a relatively high thermal conductivity. For example, in sections along the sleeve 7 or internal conductor 5 where low thermal conductivity is advantageous, such as in the substrate 8 of the fourth filter stage FS4, the core temperature sensor 1 is filled with the first filler material FS1. Similarly, in sections where high thermal conductivity is advantageous, such as the region of the temperature sensor 9 and the air line 12, the core temperature sensor 1 is filled with the second filler material FS2.

[0099] The core temperature sensor 1 equipped with metal plates 14a to 14d exhibits stronger attenuation at the output level at the relevant microwave frequency compared to the core temperature sensor 1 without metal plates 14a to 14d, while simultaneously exhibiting extremely small attenuation at the signal frequency. This effect is amplified by the adapted signal transmission antenna 2.

[0100] The present invention is, of course, not limited to the embodiments described.

[0101] In this alternative, only one row of the λ / 4 line resonant elements 11a, 11b and the λ / 2 line resonant elements 12 can be used.

[0102] Throughout, "a certain," "one," etc., can be understood as singular or plural, particularly in the sense of "at least one" or "one or more," unless an exclusion is explicitly stated, such as by an expression like "strictly one." Furthermore, unless an exclusion is explicitly stated, numerical notations can include both strictly specified numbers and the usual acceptable range. [Explanation of symbols]

[0103] 1 Core temperature sensor 2. Signal transmission antenna 3 (Surface wave) temperature measuring device 4 coaxial line 5. Inner conductor 6. Outer conductor 7 Special steel sleeve 8. Ceramic substrate 9. (Surface Wave) Temperature Sensor 10 recesses 11a Ceramic small tube 11b Ceramic small tube 12 Pneumatic rail lines 13 Conductor path 14a~14d Small metal plates D H Inner diameter of special steel sleeve D Pl Diameter of small metal plates L Pl Thickness or length of the metal plate

Claims

1. Core temperature sensor (1), The system comprises a temperature measuring device (3) equipped with at least one temperature sensor (9), and a signal transmission antenna (2) connected to the temperature measuring device (3) via a coaxial line (4), The temperature information calculated by at least one of the temperature measuring devices (3) can be transmitted via the signal transmission antenna (2) at a signal transmission frequency different from the microwave frequency. - The coaxial line (4) has at least one line resonant element (11a, 11b, 12) that is tuned to the microwave frequency, - A conductive small plate (14a to 14d) is provided at at least one interface of at least one such line resonant element (11a, 11b), and the small plate (14a to 14d) is electrically connected to the inner conductor (5) or outer conductor (6) of the coaxial line (4). Core temperature sensor (1).

2. The core temperature sensor (1) according to claim 1, wherein the conductive small plates (14a to 14d) are metal small plates.

3. The core temperature sensor (1) according to claim 1 or 2, wherein the thickness of the small plates (14a to 14d) is less than 2% of the microwave wavelength.

4. The core temperature sensor (1) according to any one of claims 1 to 3, wherein at least one line resonant element (11a, 11b, 12) is a λ / 2 line resonant element.

5. The core temperature sensor (1) according to any one of claims 1 to 4, wherein at least one line resonant element (11a, 11b, 12) is a λ / 4 line resonant element.

6. The core temperature sensor (1) according to claim 5, wherein the coaxial line (4) has two spaced-apart line resonant elements (11a, 11b) made of ceramic or glass, and the two line resonant elements (11a, 11b) have an air section (12) formed between them as a resonant line.

7. - The coaxial cable (4) has an inner conductor (5) formed from a wire piece and an outer conductor (6) formed from a metal sleeve. - At least one line resonant element (11a, 11b) is formed as a hollow cylindrical insulator that is fitted over the inner conductor (5) and extends radially to the outer conductor (6). A core temperature sensor (1) according to any one of claims 1 to 6.

8. The material of the insulator (11a, 11b) has a dielectric constant ε of 6 to 40. ｒ The core temperature sensor (1) according to claim 7, which has a particular feature and is made of ceramic.

9. - The core temperature sensor (1) has a substrate (8) connected to the internal conductor (5), - The substrate (8) is provided with a freewheeling conductor path (13) having an arbitrary length of λ / 4, which is electrically connected to the internal conductor (5). - The freewheeling conductor path (13) has a wavy, particularly meander-shaped or roll-shaped extension. A core temperature sensor (1) according to any one of claims 1 to 8.

10. The core temperature sensor (1) according to any one of claims 1 to 9, wherein the signal transmission antenna (2) is configured to reduce the amount of reflection loss at its microwave frequency.

11. The core temperature sensor (1) according to any one of claims 1 to 10, wherein the core temperature sensor (1) is filled, in whole or in part, with at least one filler material (FS1, FS2) having a coefficient of thermal expansion significantly lower than that of air but having a relative dielectric constant at least approximately equal to that of air, and is particularly cast.

12. The core temperature sensor (1) according to any one of claims 1 to 11, wherein the core temperature sensor (1) is filled, in whole or in part, with at least one non-conductive or insulating filler material (FS1, FS2) having a coefficient of expansion significantly lower than that of air but a relative dielectric constant at least approximately equal to that of air.

13. The at least one packing material has at least its thermal conductivity λ Ｗ It contains at least two filling materials (FS1, FS2) that are significantly different, The outer conductor (6) is filled in sections along its longitudinal extension with one of the filler materials (FS1, FS2). The core temperature sensor (1) according to claim 12.

14. The core temperature sensor (1) according to any one of claims 1 to 13, wherein the signal transmission antenna (2) is surrounded by a filling material having a dielectric constant significantly higher than that of air.

15. A system comprising a microwave cooking device and at least one core temperature sensor (1) according to any one of claims 1 to 14, The system is configured to wirelessly transmit signals at a signal transmission frequency between the signal transmission antenna (2) of the core temperature sensor (1) and the signal transmission antenna of the microwave cooking equipment. system.

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