Core temperature sensor and combination oven with core temperature sensor

Description

[0001] The invention relates to a core temperature probe with a microwave trap and a cooking appliance with a core temperature probe.

[0002] In professional and commercial kitchens, combination ovens are used, capable of cooking food in a single cooking chamber using various methods. In addition to classic cooking methods using hot air and / or steam, modern combination ovens often also utilize microwave radiation. The energy from the microwave radiation can be used to cook food alone or in combination with the aforementioned methods. Magnetrons or semiconductor components can be used as microwave sources to introduce microwaves into the cooking chamber.

[0003] To achieve the best possible results when cooking food, it is advantageous to monitor the cooking process as precisely as possible in order to change certain cooking parameters such as temperature, humidity and / or cooking time if necessary.

[0004] Modern cooking appliances use, among other things, core temperature probes for this purpose. A core temperature probe typically has a measuring probe equipped with temperature sensors, which is inserted into the food before the cooking process begins. During cooking, the temperature sensors measure the core temperature of the food and transmit this data to an evaluation unit in the cooking appliance. The measured core temperatures make it possible to determine the degree of doneness of the food, allowing the cooking process to be controlled based on this information to achieve the desired cooking result.

[0005] When using a core temperature probe in a microwave oven, a problem arises: the probe can act as an antenna, receiving the incoming microwaves. This leads to unwanted electrical currents within the probe, which can cause it to overheat. This can result in the probe becoming so hot that it is damaged. This is especially likely to occur when the probe is in a parked position, i.e., not inserted into the food being cooked.

[0006] If the core temperature probe is inserted into the food being cooked, the food can be heated disproportionately in the area of ​​the probe. Furthermore, the unintentional heating of the core temperature probe, especially the temperature sensors, can distort the measured temperatures.

[0007] Therefore, the object of the present invention is to provide a device to prevent damage to the core temperature probe, unwanted heating of the food being cooked, and faulty measurements when a combination cooking appliance is in microwave operation.

[0008] DE 10 2020 104743 A1 discloses a core temperature sensor according to the preamble of claim 1.

[0009] The object of the invention is achieved by a core temperature sensor for a combination cooking appliance, comprising a measuring section and a handle section. Furthermore, a contact tube is provided, which extends at least partially into the handle section and has a handle-side end facing the handle section. A cable is guided in the contact tube, extending from the handle section into the measuring section. The cable has an exposed section within the handle section, where the contact tube and cable form a contact point. The contact point is located at a distance from the handle-side end corresponding to an electrical wavelength of the microwave radiation in the handle section that is less than or equal to one-quarter of the wavelength of the microwave radiation used in the combination cooking appliance.

[0010] This ensures that the handle end of the contact tube is located at a minimum of the electromagnetic field (hereinafter referred to as the E-field) generated by the microwave radiation during microwave operation of the combination oven. This means it is positioned at a point in the electromagnetic field where the field strength is at a local or global minimum. This reduces the current flow to the handle end at this position, thereby reducing the overall energy input to the core temperature probe. Lower energy input, in turn, means that the core temperature probe, and especially the handle section, heats up less, thus extending the handle's lifespan. Since the service life of a core temperature probe is largely determined by the durability of its handle section, this results in an overall improved service life for the core temperature probe.

[0011] A contact tube is a tubular element that has the shape of an elongated, hollow cylindrical body, within which a cable can be received and guided. Specifically, the contact tube is a circular cylinder, i.e., circular in cross-section.

[0012] The term "handle end" refers to the end of the contact tube that faces the handle section, i.e., away from the measuring section. Accordingly, the contact point, viewed from the handle end, is located in the direction of the measuring section.

[0013] A "measuring section" refers to the area used to measure the temperature of food being cooked when inserted. For example, the measuring section may contain at least one temperature sensor. The measuring section does not need to be fully inserted into the food. The measuring section is also referred to as a measuring probe.

[0014] The term "handle section" refers to the part of the core temperature probe by which a user can hold it. For example, the handle section may have an ergonomically shaped design to fit the hand, allowing for easy handling of the core temperature probe in the cooking chamber.

[0015] Wavelength refers in particular to the wavelength in a vacuum (or approximately in air).

[0016] Electrical length refers to the distance an electromagnetic wave travels in a propagation medium, for example, in the handle section and / or the measuring section. This is particularly true when the field lines are completely embedded in the material, e.g., in a coaxial structure, especially between a braided shield and the contact tube.

[0017] Due to the dielectric properties of the materials in the two sections, the electric length can differ from the length or distance that the electromagnetic wave would travel in a vacuum (in the same time), which is also called the mechanical length. In other words, the electric length, depending on the permittivity and, if applicable, the permeability of the propagation medium, is less than or at most equal to the distance in a vacuum. Mathematically, the relationship can be expressed as follows: l el = l mech ⋅ μ r ε r , where l el the electrical length, l mech the mechanical length, µ r the relative permeability number and ε r The relative permittivity corresponds to the dielectric. The product of the relative permeability µ r and the relative permittivity ε rFor most materials, the product is greater than 1. In a vacuum, the product is exactly 1, whereas in air it is approximately 1.

[0018] In particular, a volume-(field strength)-weighted relative permittivity can be used for the handle section of the core temperature sensor. ε r and a volume- (field strength)-weighted relative permeability µ r The field lines are only partially present in the handle or measurement section, as another part is in the air.

[0019] The handle section, meaning all materials arranged within it, corresponds to the electrical wavelength of the microwave radiation within the handle section. This means that the electromagnetic waves of the microwave radiation, i.e., the microwaves themselves, within the handle section have an electrical wavelength that is at least one-quarter of the wavelength of the microwave radiation. Depending on the material used in the handle section, the distance between the contact point and the handle end is shorter than the electrical wavelength. The higher the relative permeability of the material used in the handle section, the shorter this distance can be while still ensuring that the electrical wavelength of the microwave radiation within the handle section is less than one-quarter of the wavelength of the microwave radiation (in a vacuum). This is due to the influence of permeability and permittivity, as explained above.

[0020] Therefore, the electric length can be understood as the distance traveled in a vacuum with a velocity factor. This velocity factor arises because the electromagnetic wave (i.e., the microwave) propagates in a medium with a different permittivity (and permeability) than a vacuum, for example, in the material of the handle. The handle acts as a dielectric for the electromagnetic radiation entering it. This physical relationship is expressed by the velocity factor, which depends on the medium and is 1 in the case of a vacuum.

[0021] As a result, the distance between the contact point and the handle end can be correspondingly shorter, namely by the shortening factor, if a different material (propagation medium) is present in the handle section, especially within the groove, than in the cooking chamber, e.g. the material of the handle, the contact tube, the cable or other components in the handle section.

[0022] Therefore, the following relationship generally applies: 1 4 λ ⋅ F Griffabschnitt ≤ d Abstand , where λ corresponds to the wavelength of the microwave radiation used in the cooking chamber (in a vacuum), d distance is the distance between the contact point and the handle-side end, and F handle section represents the shortening factor of the handle section, where the shortening factor is given by 1 μ r ε r can be expressed.

[0023] To ensure particularly low energy input into the handle section, it is preferred that the electrical length be at least 0.1 cm shorter than one-quarter of the wavelength of the microwave radiation used in the combination oven. Particularly preferred is an electrical length of at least 0.5 cm shorter than one-quarter of the wavelength of the microwave radiation used in the combination oven. Most particularly preferred is an electrical length of at least 1.5 cm shorter than one-quarter of the wavelength of the microwave radiation used in the combination oven.

[0024] According to a first aspect of the invention, the core temperature sensor is provided with a microwave trap having a pot-shaped trap section with a trap opening oriented towards the measuring section and a bottom with a central passage towards the handle section. The contact tube runs through this central passage.

[0025] The term "pot-shaped trap section" refers to the area of ​​the microwave trap that captures electromagnetic waves in the microwave range. This section has a geometric depth, measured from the bottom to the opening, that is specific to at least one electrical wavelength of the electromagnetic radiation used in the cooking chamber, in order to trap it within the trap section.

[0026] A microwave trap is a lambda-quarter trap. A lambda-quarter trap is a device that prevents microwave radiation from passing through it. In principle, the microwave trap can be designed in any way, as long as it has a geometric depth corresponding to an electrical length of approximately one-quarter of the wavelength of the microwave radiation used in the cooking chamber. The lambda-quarter trap can also incorporate a dielectric, in which case the geometric depth is less than one-quarter of the wavelength, while still maintaining an electrical length of one-quarter of the wavelength.

[0027] Furthermore, the microwave trap also works synergistically with the arrangement of the contact point and the handle-side end, since the microwave trap reduces the overall amount of microwave radiation entering the handle section, and the distance between the contact point and the handle-side end further reduces the energy input of the remaining microwave radiation into the handle section.

[0028] In particular, the contact tube is contacted with the base at the central passage, preferably by laser welding at the central passage. This represents a particularly efficient manufacturing process for a microwave trap.

[0029] According to another aspect, the contact tube makes electrically conductive contact with the cable shield at the contact point. Consequently, according to this aspect, the contact tube is made of an electrically conductive material, preferably a metallic material. Due to its electrically conductive properties, the contact tube can absorb electrical currents and conduct them via the contact point into the exposed section of the cable.

[0030] Braided shielding is preferred. Braided shielding is a proven method for protecting the cable's interior from electromagnetic interference.

[0031] In a further embodiment of the invention, the handle-side end of the contact tube is arranged in an insulated area of ​​the cable in which the shielding is surrounded by an outer conductor sheath.

[0032] The end closest to the handle forms the transition from the contact tube to the outer sheath of the cable. Specifically, this end is crimped to the outer sheath, thus firmly connecting the cable and the end of the contact tube. This arrangement of the end closest to the handle on the outer sheath is advantageous because it prevents current flowing along the contact tube into the shielding at random points, instead directing it only into the exposed section. This defines the currents introduced into the cable. Furthermore, it prevents the ingress of liquids and atmospheric moisture.

[0033] The outer conductor sheath is preferably made of an electrically non-conductive material, for example PTFE.

[0034] Another aspect of the invention provides that a counter-pressure element is arranged in the exposed area below the shielding, which is designed to exert a radially outward force on the shielding, so that it is pressed outwards against the contacting tube.

[0035] The counter-pressure element can be a sleeve or similar. The only requirement is that the counter-pressure element has the shape of a wooden cylindrical body so that it can accommodate the inside of the cable.

[0036] Preferably, the counter-pressure element has a diameter that is equal to or larger than the diameter of the shielding, so that when the shielding is placed over the counter-pressure element, the shielding is pressed radially outwards by the same or larger diameter of the counter-pressure element.

[0037] Alternatively, a crimping element can be arranged in the exposed area above the shielding, forming the contact point that (indirectly) connects the cable, and in particular its shielding, to the contact tube. In other words, the contact tube forms an (indirect) contact point with the cable, namely in the exposed area.

[0038] The crimping element can be crimped to the shield and rolled onto the contact tube. To provide counter-pressure for rolling onto the contact tube, the crimping element can have a section with a larger diameter compared to the rest of the crimping element.

[0039] Therefore, the contact tube is indirectly connected to the cable via the pressing element.

[0040] Basically, the contact point establishes an electrical connection between the cable and the contact tube. This electrical contact can be indirect, via the crimping element, or direct, if the contact tube directly contacts a part of the cable, such as its shielding. In this case, a counter-pressure element may be provided, which is located beneath the shielding.

[0041] However, the crimping element can also act as the counter-pressure element for the contact tube. This is because, although the crimping element is applied to the cable, especially its shielding, it functions as the counter-pressure element for the contact tube when it is rolled.

[0042] Another embodiment of the invention involves the contacting tube essentially completely contacting the shield at the contact point along the circumference of the shield, so that the contact point is formed as a continuous contact ring. Alternatively, the contacting tube can essentially completely contact the pressing element at the contact point along the circumference of the pressing element, so that the contact point is formed as a continuous contact ring.

[0043] This ensures particularly good contact. Furthermore, continuous contact in the form of a contact ring provides a particularly stable connection between the contact tube and the shielding or the crimping element.

[0044] According to another aspect of the invention, the contact point is formed by a radially inwardly directed curvature of the contacting tube, wherein the curvature is produced in particular by rolling the contacting tube onto the cable.

[0045] The inward-facing bulge refers to a radially inward-pointing depression along the circumference of the contact tube, at least at its apex, which touches the shielding and thus establishes an electrically conductive connection. A bulge is easy to manufacture and therefore represents a simple design for contacting the contact tube with the shielding. Furthermore, the bulge reduces the diameter of the contact tube and presses against the shielding, thus securing the shielding and, consequently, the cable to the bulge in a slip-resistant position.

[0046] Another aspect of the invention provides that the contact point is arranged at a minimal distance from the ground.

[0047] According to the invention, the distance between the contact point and the handle end corresponds to a distance equal to the electrical wavelength of the microwave radiation in the handle section, which is equal to or less than one-quarter of the wavelength of the microwave radiation used in the combination oven. This condition can be achieved particularly easily by placing the contact point as close as possible to the base of the microwave trap. A minimum distance thus refers to the technically smallest possible distance at which the base may be from the contact point without the base being deformed by the insertion of the contact point between the contact tube and the shielding, which would negatively impair the function of the microwave trap.

[0048] For example, the distance is 0.1 - 4 mm, preferably 0.1 - 2 mm, most preferably 0.1 - 1 mm.

[0049] According to another aspect of the invention, the trap opening has a distance to the handle-side end which corresponds to an electrical length of the microwave radiation in the handle section which is shorter than or equal to one quarter of the wavelength of the microwave radiation used in the combination cooking appliance.

[0050] The distance between the trap opening and the handle end is measured from the center of the trap opening to the center of the handle end of the contacting tube, with both centers having a common axis of rotation extending from the handle section to the measuring section.

[0051] Due to the chosen distance between the opening of the trap and the handle end, the transition from the contact point on the outer sheath of the cable also lies at a local or global minimum in the electric field during microwave operation of the cooking appliance. This results in a lower field strength coupled to the transition point, thus reducing the sheath current flow. This has the advantage of generating less heat at the handle end, thereby extending the lifespan of the core temperature probe.

[0052] Furthermore, the invention relates to a combination cooking appliance for cooking food, comprising a cooking chamber, a microwave generator, and a control unit connected to a core temperature probe provided in the cooking chamber according to one of the preceding aspects. A combination cooking appliance is defined as a cooking appliance for cooking food that, in addition to using microwave radiation, can also cook the food using steam and / or hot air. Such a cooking appliance allows for a combination of different cooking methods, which can be used either individually or together.

[0053] Due to the use of a core temperature probe in accordance with the aspects mentioned above, the combination cooking appliance according to the invention can use the core temperature probe in microwave operation without excessive heating of the handle section and / or the measuring section. Since the measuring section does not heat up significantly in certain areas, more accurate temperature readings are also possible, allowing the cooking appliance to monitor the cooking process more precisely. This also enables more precise control of the cooking process and better cooking results. Conversely, less heating of the handle section allows for a longer lifespan of the core temperature probe.

[0054] Further features and advantages of the invention will become apparent from the following description and the accompanying drawings, to which reference is made. The drawings show: Figure 1in a schematic representation a combination cooking appliance according to the invention with a core temperature probe according to the invention; Figure 2 in a schematic sectional view the core temperature sensor according to the invention Figure 1 ; Figure 3 in a schematic sectional view the handle section of the core temperature sensor according to the invention. Figure 1 ; Figure 4 in a schematic representation the measuring-side end of a cable for the core temperature sensor according to the invention. Figure 1 ; Figure 5 in a schematic sectional view the routing of the cable in the handle of the core temperature sensor according to the invention. Figure 1 ; Figure 6A in a schematic sectional view the routing of the cable in the handle of the core temperature sensor according to the invention. Figure 1 , with a counter-pressure element; Figure 6B in a schematic sectional view the routing of the cable in the handle of the core temperature sensor according to the invention. Figure 1, with a pressing element designed as a sleeve; Figure 7 a simulation model for simulating the electromagnetic load along the core temperature sensor according to the invention Figure 1 ; Figure 8 a simulation graphic according to the simulation model from Figure 7 from an electric field along a non-inventive core temperature sensor; Figure 9 a diagram of the simulation graph from Figure 8 ; Figure 10 a simulation graphic according to the simulation model from Figure 7 from an electric field along a core temperature sensor according to the invention; and Figure 11 a diagram of the simulation graph from Figure 10 .

[0055] Figure 1 schematically shows a combination cooking appliance 10 according to the invention, which has a cooking chamber 12.

[0056] In addition, the combination cooking appliance 10 contains a heating device 14, a steam generator 16 and a microwave generator 18, each of which is connected to and controlled by a control unit 20.

[0057] A food item 22 is placed in the cooking chamber 12, resting on a food carrier 24. The food carrier 24 can be a tray, a dish, or a rack, which is inserted into a slot 26 within the cooking chamber 12.

[0058] The heating device 14 and the steam generator 16 are configured to provide a specific cooking chamber climate in the cooking chamber 12. This cooking chamber climate is determined by the control unit 20, particularly depending on the running cooking program. The microwave generator 18 is designed to generate electromagnetic radiation in the form of microwaves with a wavelength λ and feed it into the cooking chamber 12. Preferably, microwaves with a frequency of 2.45 gigahertz (corresponding to a wavelength λ of 12.45 cm in a vacuum) are fed into the cooking chamber 12. The microwave radiation introduced into the cooking chamber 12 can impart (additional) energy to the food 22, thereby cooking it.

[0059] Furthermore, a core temperature probe 28 is provided in the cooking chamber 12, which is designed to monitor the core temperature of the food 22 during the cooking process, provided the core temperature probe 28 is inserted into the food 22. Using the core temperature probe 28, it is possible to check when a piece of meat, such as a roast, has reached the desired degree of doneness by measuring its core temperature.

[0060] The core temperature sensor 28 has a handle section 30 and a measuring section 32 adjacent to the handle section 30. The handle section 30 is designed so that a user can grasp the core temperature sensor 28 there.

[0061] The measuring section 32, on the other hand, fulfills the actual function of the core temperature probe 28, namely to determine the core temperature inside the food 22. To enable core temperature measurement, the core temperature probe 28 is at least partially inserted into the food 22. The core temperature probe 28 can be inserted along the entire length of the measuring section 32, as shown in Figure 1 shown, being inserted into the food 22 or only partially, especially in the case of small or less voluminous food 22.

[0062] Furthermore, the core temperature probe 28 has a microwave trap 34, which is arranged at the transition between the measuring section 32 and the handle section 30. When inserted, the microwave trap 34 is therefore located outside the food 22 or at most its end face is in contact with it.

[0063] The microwave trap 34 is designed to protect the core temperature probe 28 from the energy of the microwaves when the combination cooking appliance 10 is switched on, i.e. when microwaves are fed into the cooking chamber 12.

[0064] To achieve a trapping effect, the microwave trap 34 is designed as a quarter-lambda trap, which is tuned to the wavelength of the electromagnetic radiation used in the cooking chamber 12. For this purpose, the microwave trap 34 has a geometric length (trap depth) that corresponds to the electrical wavelength of approximately one-quarter of the wavelength of the electromagnetic radiation used in the cooking appliance 10.

[0065] The core temperature probe 28 is connected to the control unit 20 via a cable 36 for signal transmission. In this way, the core temperature probe 28 can transmit the measured core temperature to the control unit 20 so that the latter can monitor the cooking process and, if necessary, regulate the cooking process taking the measured core temperature into account.

[0066] Further details of the core temperature sensor 28 are in Figure 2 explained in more detail below, which will be referred to below.

[0067] In Figure 2 The core temperature sensor 28 is divided into two sections, which are separated by a dashed line in the drawing. The area above the dashed line in Figure 2The measuring section 32 is at least partially inserted into the food 22 to measure the internal temperature of the food 22. Below the dashed line is the handle section 30, which serves to handle the core temperature probe 28. The microwave trap 34 is located at the level of the dashed line, and thus between the measuring section 32 and the handle section 30, i.e., at the transition point.

[0068] For temperature measurement, several temperature sensors 38 are provided along the measuring section 32; in this case, three temperature sensors 38 are used. Of course, any other number of temperature sensors is conceivable. Preferably, the temperature sensors 38 are arranged evenly along the measuring section 32. At least one additional temperature sensor 38 can also be provided in the handle section 30, which can serve as a reference measurement for the cooking chamber temperature or as part of a microwave load sensor.

[0069] The temperature sensors 38 are surrounded by a measuring lance 40, which in the illustrated embodiment is designed as a hollow cylinder. A conductor 42 is also provided in the measuring lance 40, extending along the measuring section 32 and connecting the temperature sensors 38 to each other. From the temperature sensors 38, the conductor 42 extends into the handle section 30 and forms the signal-transmitting component of the cable 36. The core temperature values ​​detected by the temperature sensors 38 can thus be transmitted to the control unit 20.

[0070] In order for the metallic measuring lance 40 to be inserted into the food 22, the measuring lance 40 is provided at its free end, which is away from the handle section 30, with a tip 44, to which an end section 46 is adjacent, which widens conically towards the handle section 30 and leads into a straight shaft section 48.

[0071] More precisely, the shaft section 48 houses the line 42 and the temperature sensors 38.

[0072] Furthermore, a contact tube 50 is provided, which can be formed integrally with the measuring lance 40 or be separate and attached to the measuring lance 40. For example, the measuring lance 40 can be welded to the contact tube 50, in particular by laser welding.

[0073] As in Figure 2As can be seen, the contact tube 50 has a larger diameter than the measuring lance 40, so a transition section 51 is provided in which the measuring lance 40 widens conically towards the handle section 30 until its diameter corresponds to that of the contact tube 50. The transition section 51 can be formed integrally with the measuring lance 40 and / or the contact tube 50, or it can be separate from them and welded to both, in particular by laser welding.

[0074] The contact tube 50 extends at least partially into the handle section 30 and has a handle-side end 52 that faces the handle section 30.

[0075] As in Figure 2 As shown, the handle-side end 52 ends approximately halfway up the handle section 30.

[0076] In addition, the cable 36 is guided in the contact tube 50, extending into the handle-side end 52 and running towards the measuring section 32.

[0077] The handle section 30 is explained in more detail below.

[0078] In the handle section 30 of the core temperature sensor 28, a handle 54 is provided, which is made, for example, of a plastic, preferably of a heat-resistant plastic, in particular PEEK. The handle 54 has an elongated cylindrical shape extending towards the measuring section 32, wherein the handle 54 has one end facing the measuring section 32 and a second end facing away from it.

[0079] At its end facing the measuring section 32, the handle 54 is provided with a trap-side opening 56, which at least partially surrounds the microwave trap 34. Preferably, the handle 54 is injection-molded around the microwave trap 34, so that the microwave trap 34 is firmly connected to the handle 54 in the area of ​​the trap-side opening 56.

[0080] Furthermore, the handle 54 has a knob 58 in the area around the opening 56 on the trap side, which is designed as a continuous radial projection that completely surrounds the microwave trap 34. The knob 58 serves to ensure that the core temperature probe 28 can be handled securely without the user slipping off the handle 54.

[0081] At the end furthest from the measuring section 32, which is opposite the opening 52 on the trap side, the handle 54 has a cable-side opening 60. A cable channel 62 extends from the cable-side opening 60 to the trap-side opening 56, accommodating the cable 36. Consequently, the handle 54 can be designed as a hollow cylinder. The handle-side end 52 of the contact tube 50 is located at about half the height of the cable channel 62, which corresponds approximately to half the height of the handle 54.

[0082] As already mentioned in Figure 1 As shown, the microwave trap 34 is provided at the transition between the handle section 30 and the adjacent measuring section 32, which will be discussed below.

[0083] Figure 2Figure 1 shows that the microwave trap 34 comprises a cylindrical trap section 64, which is pot-shaped, such that the trap section 64 has a base 68 at a first end 66, which corresponds to the handle section 30, and a trap opening 72 at a second end 70, which faces the measuring section 32. The two ends 66, 70 are opposite to each other. Therefore, the base 68 corresponds to the handle section 30 and the trap opening 72 to the measuring section 32. The trap opening 72 is surrounded by a rim region 74.

[0084] Furthermore, the trap section 64 surrounds the contact tube 40, which extends from the measuring section 32 to the handle section 30 through a passage 76 in the base 68 of the trap section 64. The trap section 64 is contacted with the contact tube 40 at the passage 76. Specifically, the trap section 64 is laser-welded to the contact tube 40 at the passage 76. In other words, the base 68 is closed up to the contact tube 40.

[0085] Furthermore, the microwave trap 34 has a dielectric filling element 78, which is arranged in the trap section 64. More precisely, the dielectric filling element 78 is arranged between the contact tube 40 and the trap section 64.

[0086] The filling element 78, for example, contacts the bottom 68 of the trap section 64 via an end face and an inside of the trap section 64 along its outer circumference.

[0087] For example, the dielectric filling element 78 can be a ceramic with a dielectric constant of 9 to 10 (at 20°C and 1 GHz), in particular a ceramic made of aluminum oxide with a purity of at least 95%.

[0088] In order to allow the contacting tube 40 to extend from the measuring section 32 into the handle section 30, the dielectric filling element 78 is shaped as a hollow cylinder which has a through-opening 80 which is aligned with the through-opening 76 in the base 68, so that the contacting tube 40 extends at least partially through the through-opening 76 and the through-opening 80.

[0089] As in Figure 2As can be clearly seen, in the illustrated embodiment, the contact tube 40 extends completely through the through-opening 80 and through the filling element 78. Therefore, the contact tube 40 also extends completely through the trap section 64. This results in the filling element 78, the contact tube 40, and the trap section 64 being arranged coaxially with each other.

[0090] Furthermore, an annular end element 81 is provided in the area around the trap opening 72 of the trap section 64. This end element rests on the end face 83 of the filling element 78 and completely encloses the circumference of the contact tube 40. The annular end element 81 is attached to the contact tube 40, in particular by laser welding. The annular end element 81 serves to securely hold the dielectric filling element 78 in the microwave trap 34.

[0091] Preferably, the ring-shaped termination element 81 is made of an electrically conductive material. Particularly preferably, the ring-shaped termination element 81 is made of a metal or an alloy.

[0092] The microwave trap 34 is designed to prevent excessive heating of the handle 54 and thus of the entire core temperature probe 28. To achieve this, the contact tube 50 is connected to the cable 36 in a specific manner, which is described below. Figures 3 - 6 will be explained.

[0093] First, the cable's construction will be explained in more detail using the following examples: Figure 4 received.

[0094] The cable 36 includes at least the conductor 42, which is enclosed by a shield 82. This in turn is surrounded by a conductor sheath 84.

[0095] The shielding 82 serves to protect the interior of the cable 36, i.e., the at least one conductor 42, from electromagnetic interference.

[0096] Shielding 82 may be a braided shield, as in Fig. 3 As shown, for example, the braided shield is designed as copper wires braided around at least one conductor 42. The wires are either bare or tinned. In any case, the shield 82 is made of an electrically conductive material.

[0097] The at least one conductor 42 is preferably made of a copper wire 86 and insulated with a further sheath 87. In this way, the conductor 42 can be insulated from the shield 82 as well as from optionally further conductors 42. As in Figure 4 As shown, cable 36 preferably comprises six conductors 42.

[0098] Alternatively, the shielding 82 can also be a foil. The outer cable sheath 84 serves to protect the cable interior from moisture and other liquids from the cooking chamber 12. This can be made of PTFE.

[0099] The outer conductor sheath 84 can be made of polytetrafluoroethylene (PTFE) and have a wall thickness greater than 0.3 mm, for example, in the range of 0.35 mm to 1 mm, preferably from 0.45 mm to 0.7 mm. This represents a significant reinforcement of the outer PTFE conductor sheath 84 compared to conventional sheaths, whose wall thickness is typically less than 0.1 mm, particularly in the range of 0.01 mm to 0.05 mm. This allows the temperature inside the cable 36 to be kept low during microwave operation of the combination oven 10, thus preventing overheating of the individual conductors 42. The conductors 42 are better shielded due to the outer conductor sheath 84 with its corresponding wall thickness.

[0100] Ultimately, the outer conductor sheath 84, with its wall thickness, ensures that the distance between the shield 82, which is (directly) surrounded by the outer conductor sheath 84, and a metal part of the cooking chamber 12, e.g., a cooking chamber wall, is sufficiently large. Therefore, due to its wall thickness, the outer conductor sheath 84 also provides (electromagnetic) shielding for the conductors 42, in particular in addition to the shield 82. The wall thickness of the outer conductor sheath 84 ensures, in particular, that the conductors 42 are optimally positioned within the electric field present in the cooking chamber 12.

[0101] The cable 36 is securely fixed in the handle section 30 by being attached to the contact tube 50. For this purpose, the cable 36 has an exposed section 88 in the handle section 30. In this exposed section 88, the contact tube 50 and the cable 36 form a contact point 90.

[0102] The stripped section 88 is characterized by the fact that this section of the cable 36 is stripped, i.e., freed from the outer cable sheath 84, so that the underlying part of the cable 36, i.e., the shielding 82, is exposed. This allows the contact tube 50 to contact the shielding 82 via the contact point 90. The stripped section 88 is located in the handle section 30 and extends towards the measuring section 32 into the microwave trap 34.

[0103] Essentially, the section of the shielding 82 that is not surrounded by the outer conductor sheath 84 defines the spatial extent of the unshielded area 88. This extends into the microwave trap 34.

[0104] Adjacent to the stripped section 88, an insulated section 92 of the cable 36 is provided in the direction of the handle section 30. In the insulated section 92, the shield 82 is not separated from the cable sheath 84, and the handle-side end 52 of the contact tube 50 is located in this section. Consequently, the handle-side end 52 rests on the outer cable sheath 84. The handle-side end 52 of the contact tube 50 is crimped onto the outer cable sheath 84, thereby achieving a secure connection between the cable 36 and the contact tube 50. The insulated section 92 extends from the handle 54 into the control unit 20.

[0105] Adjacent to the stripped section 88 in the direction of measuring section 32, a shield-free section 94 is provided in which the cable 36 is freed from the shielding 82, so that only the conductors 42 extend into the measuring lance 40. In this respect, the stripped section 88 is arranged between the insulated section 92 and the shield-free section 94. Preferably, the shielding 82 ends before the measuring lance 40. Particularly preferably, the shielding 82 ends within the microwave trap 34.

[0106] The following section provides a more detailed explanation of contact point 90.

[0107] More precisely, the contacting tube 50 makes electrical contact with the shielding 82 of the cable 36 at the contact point 90, so that currents can flow between the shielding 82 and the contacting tube 50, e.g. currents that arise from the influence of microwave radiation on the measuring lance 40, the trap section 64 and the contacting tube 50.

[0108] The contact point 90 can be formed by a radially inwardly directed bulge 96 of the contact tube 50, wherein the bulge 96 is produced in particular by rolling the contact tube 50 onto the cable 36. This is particularly well suited in Fig. 6 to recognize.

[0109] Rolling is a process in which the contact tube 50 is first pushed onto the shield 82 and then at least partially deformed by a radially inwardly directed force, so that the bulge 96 is formed on the circumference of the contact tube 50, which contacts the shield 82. In this way, the contact tube 50 is pressed onto the shield 82 by means of the contact point 90, so that they are securely connected to each other.

[0110] Furthermore, the contacting tube 50 can essentially completely touch the shielding 82 at the contact point 90 along the circumference of the shielding 82, so that the contact point 90 is formed as a continuous contact ring.

[0111] The contact ring can be formed by a continuous curvature 96 that completely surrounds the circumference of the shielding 82.

[0112] As in the Figures 3 and 6A As shown, a counter-pressure element 98 can also be provided, which is configured to exert a radially outward force on the shield 82, so that it is pressed outward against the contact tube 50. In this way, the shield 82, which is already mechanically flexible, can be stretched outward to achieve better electrical contact between the shield 82 and the contact tube 50.

[0113] The counter-pressure element 98 can be a metallic sleeve that is pushed onto the lines 42 in the exposed area 88, so that the shielding 82 lying over the lines 42 is displaced radially outwards. Figure 6A It is shown that the lines 42 make a bend outwards towards the shielding 82 through the counter-pressure element 98.

[0114] Alternatively, as in Figure 6B As shown, a crimping element 99 is provided, which is designed as a metallic sleeve. This is pushed onto the conductor 42 in the exposed area 88, so that the shielding 82 lies within the crimping element 99, and in particular is completely enclosed by it. The sleeve is electrically connected to the shielding 82, in particular by crimping.

[0115] Furthermore, the sleeve has a section through which it is connected (mechanically and / or electrically) to the contact tube 50, in particular by a rolling action. This section provides outward counter-pressure for the rolling action against the contact tube 50, which is why the pressing element 99 acts as a counter-pressure element for the contact tube 50. This section can have a larger diameter than the rest of the sleeve.

[0116] In this respect, the (indirect) contact point 90 is formed via the sleeve, which connects the shielding 82 and the contacting tube 50 to each other, in particular electrically conductively.

[0117] The counter-pressure element 98 or the pressing element 99 can also be omitted. An embodiment without counter-pressure element 98 or pressing element 99 is shown, for example, in Fig. 5 shown.

[0118] In any case, the direct or indirect contact point 90 is formed in the unshielded area 88, via which the contact tube 50 is directly or indirectly (at least) electrically connected to the cable 36.

[0119] As in the Figures 3 and 6A, 6B As shown, not only can the contact tube 50 be contacted with the shield 82 via a contact point 90, but the contact tube 50 can also be crimped in the insulated section 92 by at least one recess 100 on the cable sheath 84. This ensures that the contact tube 50 is particularly firmly connected to the cable 36 and also prevents moisture from penetrating through the cable-side opening 60 of the handle 54.

[0120] The recess 100 can also be designed as an inwardly directed bulge 96, which is pressed against the conductor sheath 84 at least at its apex. A continuous recess that surrounds the circumference of the cable 36 is also conceivable and preferred.

[0121] In order to keep the heat input into the handle 54 as low as possible, a certain distance d 1 between the handle-side end 52 of the contacting tube 50 and the contact point 90 must be selected.

[0122] The distance d1 from the contact point 90 to the handle-side end 52 corresponds to an electrical wavelength of the microwave radiation in the handle section 30 that is less than or equal to one-quarter of the wavelength of the microwave radiation used in the combination oven 10. The distance d1 is measured from the center points M1 of the contact point 90 to the center point M2 of the handle-side end 52, with both centers lying on the same axis of rotation Rm.

[0123] The contact point 90 is preferably arranged at a minimum distance d2 from the base 68. The distance d2 can be in a range of 0.1 to 4 mm. The distance d2 is measured from the center point M1 of the contact point 90 to the center point M3 of the base 68, with both centers lying on the same axis of rotation Rm.

[0124] Furthermore, the trap opening 72 can have a distance d 3 to the handle-side end 52, which corresponds to an electrical wavelength of the microwave radiation in the handle section 30 that is shorter than or equal to one-quarter of the wavelength of the microwave radiation used in the combination oven 10. The distance d 3 is measured from the center points M 2 of the handle-side end 52 to the center point M 4 of the trap opening 72, with both centers lying on the same axis of rotation R m.

[0125] The reduced heat transfer achieved by positioning contact point 90 is based on insights gained from simulating the electric field, as described in the Figures 8, 9 and 10 shown.

[0126] The simulation model is in Figure 7 The model shows the core temperature probe 28, whose measuring lance 40 is completely inserted into a simulated food being cooked, in this case a water medium as a food substitute. Microwave radiation is injected from the right as a coaxial mode between cable 36 and the outer surface layer (PEC for the simulation). A port (at the bottom of the water) is located at the bottom left and absorbs the outgoing waves. Based on this simulation, the power loss density in the handle 54 and the electric field strength or surface currents can be calculated.

[0127] In Fig. 8A cross-section along a non-inventive core temperature sensor 28 is shown, in which the handle-side end 52 has a distance d corresponding to an electrical length of the microwave radiation in the handle section 30 that is greater than a quarter of the wavelength of the microwave radiation used in the combination cooking appliance 10. The electric field reflected by the water on the left is shown, analogous to the food being cooked 22. The intensity of the electric field is represented by a scale in V / m (based on the 1 W excitation), where lighter areas 102 correspond to a high electric field and darker areas 104 to a lower electric field.

[0128] From the simulation in Fig. 8 It can be seen that the handle-side end 52 is located at a maximum of the electric field. This is disadvantageous and leads to higher currents along the contact tube 50 and the handle 54, causing it to experience a particularly strong energy input from the electric field.

[0129] This is also shown in the graph in Fig. 9 reproduced, which is derived from the simulation of Figure 9 The collected data shows that handle 54 (top line in the diagram) experiences a particularly high energy input compared to the other components.

[0130] Fig. 10 shows the same simulation as Fig. 8 , with the difference that the handle-side end has a distance d 1 which corresponds to an electrical length of the microwave radiation in the handle section 30 that is less than a quarter of the wavelength of the microwave radiation used in the combination oven 10. This places the handle-side end 52 at a minimum of the electric field.

[0131] This results in a lower energy input for handle 54 compared to the arrangement of handle 54 made of Figure 9 As a result, handle 54 heats up less.

[0132] This is also evident from Figure 11shown, where the handle 54 has the lowest energy input compared to the other components, and this is in comparison to Figure 9 also by an order of magnitude less.

Claims

1. A core temperature detector (28) for a combination cooking appliance (10) for cooking a cooking product (22), comprising a measuring section (32) and a handle section (30), wherein a contacting tube (50) is provided which extends at least partially into the handle section (30) and has a handle-side end (52) facing the handle section (30), wherein a cable (36) extending from the handle section (30) into the measuring section (32) is guided in the contacting tube (50), characterized in that the cable (36) has an unsheathed area (88) in the handle section (30), in which the contacting tube (50) forms a contact point (90) along with the cable (36), wherein the contact point (90) has a distance d1 to the handle-side end (52), which corresponds to an electrical length of the microwave radiation in the handle section (30), which is shorter than or equal to one quarter of the wavelength of the microwave radiation used in the combination cooking appliance (10).

2. The core temperature detector (28) according to claim 1, characterized in that the core temperature detector (28) has a microwave trap (34) which includes a pot-shaped trap section (64) having a trap opening (72) aligned with the measuring section (32) and a bottom (68) provided with a central passage (76) in the direction of the handle section (30), wherein the contacting tube (50) extends through the central passage (76), in particular wherein the contacting tube (50) is in contact with the bottom (68) at the central passage (76), more preferably in that the contacting tube (50) is laser-welded to the bottom (68) at the central passage (76).

3. The core temperature detector (28) according to claim 1 or 2, characterized in that the contacting tube (50) contacts a shielding (82) of the cable (36) in an electrically conductive manner at the contact point (90), wherein the shielding (82) is in particular a braided shielding.

4. The core temperature detector (28) according to claim 3, characterized in that the handle-side end (52) of the contacting tube (50) is arranged in an insulated area (92) of the cable (36), in which the shielding (82) is surrounded by an outer line sheath (84).

5. The core temperature detector (28) according to any of claims 3 or 4, characterized in that a counterpressure element (98) is arranged in the unsheathed area (88) below the shielding (82) and is designed to exert a radially outwardly directed force on the shielding (82), so that the latter is pressed outwardly against the contacting tube (50), or in that a pressure element (99) is arranged in the unsheathed area (88) above the shielding (82), which forms the contact point (90) connecting the shielding (82) to the contacting tube (50).

6. The core temperature detector (28) according to any of claims 3 to 5, characterized in that the contacting tube (50) substantially completely touches the shielding (82) or the pressure element (99) at the contact point (90) along the circumference of the shielding (82) or of the pressure element (99) so that the contact point (90) is formed as a continuous contact ring.

7. The core temperature detector (28) according to any of the preceding claims, characterized in that the contact point (90) is formed by a radially inwardly directed bulge (96) of the contacting tube (50), wherein the bulge (96) is produced in particular by rolling the contacting tube (50) onto the cable (36).

8. The core temperature detector (28) according to any of the preceding claims, if dependent on claim 2, characterized in that the contact point (90) is arranged at a minimum distance d2 from the bottom (68).

9. The core temperature detector (28) according to any of the preceding claims, if dependent on claim 2, characterized in that the trap opening (72) has a distance d3 to the handle-side end (52) which corresponds to an electrical length of the microwave radiation in the handle section (30), which is shorter than or equal to one quarter of the wavelength of the microwave radiation used in the combination cooking appliance (10).

10. A combination cooking appliance (10) for cooking a cooking product (22), comprising a cooking chamber (12), a microwave generator (18) and a control unit (20) which is in communication with a core temperature detector (28) according to any of the preceding claims which is provided in the cooking chamber (12).