Cooking appliance with microwave function and microwave traps

Abstract

The invention relates to a cooking appliance, comprising: a housing (2) with a cooking chamber (3), the cooking chamber (3) having a cooking chamber opening, a cooking chamber door (5) for closing the cooking chamber opening, wherein the cooking chamber door (5) has a viewing pane (52), and at least one heating means for generating microwaves of a nominal frequency in the cooking chamber (3), wherein the cooking chamber door (5) and the housing (2) together form a contact region (2.5), wherein a surface of the housing (2) in the contact region (2.5) is metallic, wherein on the cooking chamber door (5) a first seal (15) is formed and in the contact region (2.5) a first microwave trap (13) and a second microwave trap (14) are formed, wherein the microwave traps (13, 14) are each designed as a cavity (13.1, 14.1) with a trap opening (13.2, 14.2) and wherein the trap opening (13.2) of the first microwave trap (13) is covered by the viewing pane (5.2) and the trap opening (14.2) of the second microwave trap (14) is covered by the first seal (15).

Description

[0001] Cooking appliance with microwave function and microwave traps

[0002] Technical area

[0003] The invention relates to cooking appliances, in particular a cooking appliance comprising: a housing with a cooking chamber delimited by housing walls, wherein the cooking chamber has a cooking chamber opening, a cooking chamber door for closing the cooking chamber opening, wherein the cooking chamber door has a viewing window and at least one heating means for generating microwaves of a nominal frequency in the cooking chamber.

[0004] Background of the invention

[0005] Cooking appliances, in particular microwave ovens and ovens with microwave function, are known from the state of the art.

[0006] In such cooking appliances, it is necessary to prevent the escape of microwave radiation to avoid endangering people in the vicinity of the cooking appliance. For this purpose, microwave traps in the form of cavities are provided in the area of ​​a door gap to couple stray microwave radiation, thus preventing microwave radiation from escaping through the door gap. The resonant frequency of a microwave trap is determined, among other things, by the size of the door gap. A microwave appliance with a double microwave trap is known, for example, from the publications DE 102022 201 198 A1 and US 2007 / 0 012 691 A1.

[0007] It is also known to provide seals in the area of ​​a door gap in cooking appliances, as shown in the documents DE 36 07 557 A1 and EP 1 758432 A2. Such seals serve, in particular, to prevent the escape of steam or escaping hot air. The disadvantage of providing such seals is that the tolerance of the door gap increases, so that the resonant frequency of the microwave trap may no longer always match the nominal frequency of the microwave radiation used, and microwave radiation may subsequently escape through the door gap.

[0008] It is also a common requirement for the aforementioned cooking appliances that they should be as easy to clean as possible and also have an attractive design.

[0009] Description of the invention Based on the background of the invention, it is an object of the present invention to reliably prevent the escape of microwave radiation in a cooking appliance with a microwave function and a door gap seal, wherein cleaning of the cooking appliance should be easy.

[0010] The object of the invention is achieved by the features of the independent main claims, which define the invention in this respect. Advantageous embodiments are specified in the subclaims. To the extent technically feasible, the teachings of the subclaims can be combined arbitrarily with the teachings of the main and subclaims.

[0011] Advantages of the claimed aspects of the invention are explained below, and preferred modified embodiments of the aspects of the invention are described further below. Explanations, particularly regarding advantages and definitions of features, are essentially descriptive and preferred, but not limiting, examples. If an explanation is limiting, this will be expressly stated.

[0012] Where ordinal numbers ("first", "second", etc.) are used, for example to designate a component, an element, a process step, or a process action, these ordinal numbers are intended purely for differentiation in the designation and do not indicate any dependencies or sequences. This means, in particular, that, for example, a device does not have to have a "first component" in order to have a "second component." A device can also have a "first component" and a "third component" without necessarily having a "second component." Multiple units with the same ordinal number can also be provided, for example, multiple "first components."

[0013] In particular, the object is accordingly achieved by a cooking appliance comprising: a housing with a cooking chamber delimited by housing walls, wherein the cooking chamber has a cooking chamber opening, a cooking chamber door for closing the cooking chamber opening, wherein the cooking chamber door has a viewing window and at least one heating means for generating microwaves of a nominal frequency in the cooking chamber, wherein the cooking chamber door and the housing form a contact region with one another, wherein a surface of the housing is metallic in the contact region, wherein at least one first seal is formed on the cooking chamber door and a first microwave trap and a second microwave trap are formed one behind the other in the contact region, wherein the microwave traps are each formed as a cavity with a trap opening and wherein the trap opening of the first microwave trap is covered by the viewing window and the trap opening of the second microwave trap is covered by the first seal.According to the invention, the trap openings of the first microwave trap on the door side and the second microwave trap on the door side are located opposite the metal contact surface of the housing. This means that none of the door-side trap openings are located in the area of ​​the cooking chamber opening.

[0014] A cooking appliance is particularly designed as an oven with an integrated microwave (a so-called combination appliance), in which temperatures of approximately 100-250°C, for example, are provided in the cooking chamber for preparing food. The cooking appliance can also be designed as an oven with a pyrolysis function and / or a steam cooking function. The cooking appliance can also be designed as a steam cooker or as a microwave.

[0015] The heating means for generating microwaves are designed, for example, as a magnetron or a semiconductor element and, in addition to the means for generating the microwave radiation, also include means for coupling the microwave radiation into the cooking chamber, such as appropriate waveguides. The nominal frequency is, in particular, 2.45 GHz plus / minus 50 MHz. In particular, the geometry of the cooking chamber is designed such that the microwaves of the nominal frequency form standing waves therein.

[0016] A contact area is designed, in particular, as a contact area that extends at least partially around the cooking chamber opening between an outer area of ​​the cooking chamber door and the front edges of the side cooking chamber walls. In this case, the housing forms a metallic contact surface in the contact area, opposite which the door-side microwave traps with their trap openings are located. The microwave traps extend at least partially around the cooking chamber opening in accordance with the extent of the contact area and are thus channel-shaped. The trap openings then each form a slot. If the housing forms a metallic surface in the contact area, this can be the surface of a metallic component or a metallic-coated surface of a component made of another material.

[0017] To the extent that a trap opening is covered by the viewing window or the first seal, the trap opening is particularly tightly sealed, at least protected from the ingress of dirt and / or liquid, especially vapors or parts of the food being cooked, such as grease splashes. The viewing window and the first seal are designed to be permeable to microwave radiation, at least in the area where they cover the trap openings, to ensure reliable coupling of the microwave radiation into the microwave traps.

[0018] The solution to the problem with the cooking appliance described above therefore includes the teaching that a double microwave trap is formed in an outer region of the cooking chamber door, which is associated with the contact area. This double microwave trap advantageously prevents microwaves of a specific frequency from escaping from the door gap not only in a narrow band, but also across a specific, relatively broad band of frequencies. For this purpose, the microwave traps are designed for slightly different resonant frequencies, the distance between which determines the width of the band.In this way, it is achieved that even with the tolerance of the door gap caused by the first seal and the associated shift in the resonance frequencies of the microwave traps, the nominal frequency of the generated microwaves always lies within the band and the microwaves generated by the heating medium are thus reliably prevented from escaping from the door gap.

[0019] The term "one behind the other" refers to a radially outward-facing direction relative to the center of the door surface of the closed cooking chamber door. In particular, the first microwave trap is positioned further inside, closer to the center of the door surface, than the second microwave trap in the contact area.

[0020] The solution further includes the teaching that the outer region of the cooking chamber door can be designed relatively compactly, so that both microwave traps and the first seal can be arranged together in that region. The visual design of the cooking chamber door can therefore be relatively free from boundary conditions imposed by the microwave traps, thus enabling a design that is perceived as advantageous. At the same time, the viewing window extends relatively far outwards and, together with the first seal, forms a largely flat surface that is easy to clean overall. By extending the viewing window outwards, i.e. up to the trap opening of the first microwave trap, the area of ​​the cooking chamber door that is primarily exposed to soiling from the cooking chamber is largely or even completely covered by the completely flat and thus particularly easy-to-clean viewing window.

[0021] The positioning of the first seal relatively far outward and thus relatively far away from the cooking chamber also ensures that the temperature resistance requirements for the first seal are moderate. Due to the distance from the cooking chamber, the temperatures prevailing in the area of ​​the first seal are significantly lower than the cooking chamber temperature, even at relatively high cooking chamber temperatures. Therefore, many materials can be used to form the first seal, especially those that offer particularly favorable sealing properties and service lives without, however, having particularly good temperature resistance.

[0022] As an alternative to features of the above-described solution, or in a preferred embodiment of the above-described solution, the first seal is designed to be liquid-tight, in particular vapor-tight. This eliminates the need for a further seal to prevent air, vapor, and / or liquid from escaping from the cooking chamber.

[0023] As an alternative to features of the solution described above, or in a preferred embodiment of the solution described above, the first seal is made of a silicone material. Such a material has particularly good sealing properties, in particular against steam and / or liquid, with a particularly long service life, wherein silicone materials have at least sufficient properties with regard to temperature resistance to be arranged relatively far outside on the cooking chamber door. In addition, silicone materials have a favorable permittivity for forming the second microwave trap with compact geometries at the necessary resonance frequencies, favoring a compact cooking chamber door. The first seal acts as a dielectric when covering the trap opening of the second microwave trap and thus helps determine the oscillation behavior of the microwave trap.

[0024] The microwave traps each behave like an LC resonant circuit, whose inductance L is determined by the volume as well as the geometry and surface properties of the entire cavity wall, and whose capacitance C is determined by the input capacitance at the trap opening. Two opposing printed circuit boards preferably form a capacitance at the trap opening. The capacitance depends on the permittivity between the material at the trap opening, which is also determined by the material covering the trap opening, and the conductor material of the printed circuit boards on both sides of the trap opening. The resonant frequency w0 (here angular frequency) of a microwave trap is given by where the capacity C is with e as permittivity, A as the area of ​​the circuit boards at the trap opening and d as the width of the trap opening.

[0025] As an alternative to features of the above-described solution, or in a preferred embodiment of the above-described solution, the viewing panel is made of a glass material. A glass material is easy to clean and also has favorable permittivity, allowing the first microwave trap to be formed with compact geometries at the necessary resonant frequencies. Furthermore, the glass can be printed in the area where the viewing panel covers the first microwave trap to prevent the first microwave trap from being visible. The print is then permeable to microwave radiation.

[0026] As an alternative to features of the above-described solution, or in a preferred embodiment of the above-described solution, the first microwave trap is designed for a resonant frequency below the nominal frequency, and the second microwave trap is designed for a resonant frequency above the nominal frequency. This reliably prevents the escape of microwave radiation at the nominal frequency, both when the belt is shifted upwards and downwards, depending on the direction of the tolerance deviation of the door gap.

[0027] As an alternative to features of the solution described above, or in a preferred embodiment of the solution described above, the cooking appliance comprises a second seal arranged on the housing in the contact area. Such a second seal is preferably formed internally relative to the first seal, i.e. closer to the cooking chamber, and can advantageously serve to keep particularly hot air away from the first seal. The requirements placed on the first seal with regard to temperature resistance are thus reduced depending on the temperatures prevailing in the cooking chamber. In particular, a second seal is provided if a pyrolysis function is provided in the cooking appliance in order to keep the particularly hot air generated therefrom away from the first seal.

[0028] In addition to or in addition to the feature described immediately above, a further embodiment of the solution provides for the second seal to be made of glass fiber. Glass fiber offers particularly good temperature resistance and can therefore be arranged close to the cooking chamber even at temperatures during pyrolysis cleaning of the cooking chamber.

[0029] Preferably, the second glass-fiber seal is arranged closer to the cooking chamber than the first seal. In particular, the second seal is arranged further inside the contact area, closer to the center of the door surface, than the first seal.

[0030] According to one embodiment, the second seal rests against the viewing window of the cooking chamber door when the cooking chamber door is closed.

[0031] The second seal protects the first seal from high temperatures in the cooking chamber, especially during pyrolysis operation.

[0032] In addition to or in addition to the features described immediately above, a further embodiment of the solution provides for the second seal to be arranged in a groove formed on the housing in the contact area. The second seal is then held particularly securely on the housing and, with a correspondingly designed arrangement, advantageously influences the tolerance of the door gap dimension only insignificantly or not at all.

[0033] In addition to or in addition to the features described immediately above, a further embodiment of the solution provides for the second seal to be arranged opposite the viewing window on the housing. The second seal is then advantageously designed to rest easily against the viewing window in the area of ​​the first microwave trap when the cooking chamber door is closed, so that the contact area for the second seal does not need to be significantly larger to create a contact area for the second seal.

[0034] As an alternative to features of the above-described solution, or in a preferred embodiment of the above-described solution, the cooking appliance includes a spring element for pressing the cooking chamber door against the housing in the contact area when the cooking chamber door is closed. This allows the tolerance of the door gap to be relatively small, even with a seal provided, so that deviations of the resonant frequencies of the microwave traps from their design are minimal, and the escape of microwaves of the nominal frequency is reliably prevented. The spring element is particularly preferably arranged in a hinge of the cooking chamber door and interacts with the hinge.

[0035] As an alternative to features of the above-described solution, or in a preferred embodiment of the above-described solution, at least one microwave trap has a projection extending from the trap opening into the cavity, so that the trap opening is designed as a channel bounded on both sides. The projection and an outer wall of the microwave trap then form circuit boards, which together form a particularly high input capacitance C of the microwave trap. For this purpose, the circuit boards are metallic or at least metallically coated. Due to a high input capacitance C, the entire geometry of the microwave trap can be designed to be particularly compact, and the microwave trap is also particularly well suited for the entry of obliquely incident microwaves and microwaves of higher modes.

[0036] In addition to or in development of the feature immediately above, a further embodiment of the solution provides for the projection to be slotted. The slotting provides the microwave trap with further improved properties with respect to obliquely incident microwaves and microwaves of higher modes. As an alternative to features of the above-described solution, or in a preferred embodiment of the above-described solution, the cooking appliance comprises means for providing a pyrolysis function. With regard to a pyrolysis function, the advantages achieved by the first seal and optionally the second seal are particularly relevant, since potentially harmful vapors generated during pyrolysis are reliably prevented from escaping from the cooking chamber.

[0037] Short description of the drawings

[0038] The invention will be explained in more detail below with reference to preferred embodiments and the accompanying drawings. The term "figure" is abbreviated to "Fig."

[0039] The drawings show

[0040] Fig. 1 is a schematic view of a cooking appliance according to one aspect of the invention;

[0041] Fig. 2 is a detailed view of a contact area between a cooking chamber door and a housing according to one aspect of the invention in a first embodiment;

[0042] Fig. 3 is a detailed view of a contact area between a cooking chamber door and a housing according to one aspect of the invention in a second embodiment; and

[0043] Fig. 4 is a diagram showing the frequency reduction by a single microwave trap and by a double microwave trap at a door gap.

[0044] Detailed description of the drawings

[0045] The described embodiments are merely examples which can be modified and / or supplemented in many ways within the scope of the claims. Each feature described for a specific embodiment can be used independently or in combination with other features in any other embodiment. Each feature described for an embodiment of a specific claim category can also be used correspondingly in an embodiment of a different claim category. Figure 1 shows a schematic view of a cooking appliance 1 designed as an oven, comprising a housing 2, wherein a cooking chamber 3 surrounded by cooking chamber walls 2.1, 2.2, 2.3, 2.4 is formed in the housing 2. The cooking chamber 3 is accessible through a cooking chamber opening 4, in particular for introducing and removing food to be cooked, wherein the cooking chamber opening 4 can be closed by means of a cooking chamber door 5, which is shown open.In a closed state, the cooking chamber door 5 rests in a contact area 2.5 on the housing 2, circumferentially to the cooking chamber 3. The cooking appliance 1 has heating means, such as a circulating air heating means 6 with a fan (not shown in detail), heating means 7.1, 7.2 for generating radiant heat in a top and bottom heat mode, and a hidden heating means 8 for generating microwaves of a nominal frequency w0, wherein the heating means 8 is arranged such that the microwaves are coupled into the cooking chamber 3. The heating means 8 is, for example, a magnetron or a semiconductor generator. Built-in components 9 with a food support 10 resting thereon are arranged in the cooking appliance 1. The cooking appliance 1 further has operating elements 11 and a display 12.

[0046] Figure 2 shows a contact area 2.5 between a closed cooking chamber door 5 and the housing 2 in a cross-sectional view in detail. The cooking chamber door 5 is essentially formed by a frame 5.1 and a viewing window 5.2, made of glass, for example. The frame 5.1 forms a first microwave trap 13 and a second microwave trap 14 in the outer region of the cooking chamber door 5, wherein the microwave traps 13, 14 are each formed with a cavity 13.1, 14.1 and with a trap opening 13.2, 14.2. In the region of the trap openings 13.2, 14.2, a projection 13.3, 14.3 also projects into the cavity 13.1, 14.1, which forms an input capacitance C with an opposite wall of the microwave trap 13, 14. The projections 13.3, 14.3, and the opposite wall are designed as metallically conductive circuit boards. The frame 5.1 also has an external closing rebate 5.3 of the cooking chamber door 5.

[0047] The trap opening 13.2 of the first microwave trap 13 is covered by the viewing window 5.2 and protected by the viewing window 5.2 against the ingress of air, steam, and / or liquid, in particular against contamination. The trap opening 14.2 of the second microwave trap 14 is covered by a first seal 15 and protected by the first seal 15 against the ingress of air, steam, and / or liquid, in particular against contamination. The first seal 15, as the sole component of the cooking chamber door 5, rests against the metallically conductive surface of the housing 2 in the contact area 2.5 and seals the door gap T.

[0048] The first seal 15 is made of silicone, for example. Due to the relatively large distance from the cooking chamber 3, the temperature effectively present at the first seal 15, i.e. the thermal influence acting on the first seal 15 from the air and the surrounding components of the cooking appliance 1, is significantly reduced compared to the cooking chamber temperature. This enables the use of a silicone seal without the risk of thermal damage. Furthermore, the cooking chamber 3 and a part of the cooking chamber door 5 that extends relatively far into the contact area 2.5 are covered by the viewing window 5.2, so that the area of ​​the cooking chamber door 5 that is primarily affected by soiling from the cooking chamber 3 is essentially formed by the easy-to-clean viewing window 5.2.

[0049] Figure 3 shows a variant of a contact area 2.5 between a closed cooking chamber door 5 and the housing 2 in a detailed cross-sectional view, which essentially corresponds to the embodiment shown in Figure 2 and will not be explained again with regard to identical features. In addition to the features of the embodiment according to Figure 2, a groove 16 is formed in the contact area 2.5 on the housing 2, in which groove a second seal 17 is arranged. The second seal 17 is made of glass silk and is arranged closer to the cooking chamber 3 than the first seal 15. The second seal 17 thus provides protection against the penetration of hot air from the cooking chamber 3 into the door gap T or into the contact area 2.5 and to the first seal 15, for example at particularly high cooking chamber temperatures during pyrolysis cleaning of the cooking appliance 1.When the cooking chamber door 5 is closed, the second seal 17 rests against the viewing window 5.2 in the area of ​​the first microwave trap 13.

[0050] Figure 4 shows a diagram of a frequency band of frequencies that can pass through the door gap T, with microwave traps 13, 14 causing a reduction in this frequency band around their resonant frequency. The angular frequencies w are shown on the X-axis, and a level A on the Y-axis. w0 also indicates the nominal frequency of the heating means 8. The solid line represents the frequency bands or frequency reductions when the nominal dimension for the door gap T between the cooking chamber door 5 and the housing 2 is precisely maintained. The dashed line represents deviations in the frequency bands or frequency reductions when the door gap T deviates from the nominal dimension due to tolerances.

[0051] In an upper illustration, the frequency band is shown for a single microwave trap, in a lower illustration for a double trap as in Figures 2 and 3, in which the resonance frequency of the first microwave trap 13 is nominal, that is, at the nominal size of the door gap T, below the nominal frequency w o and the resonant frequency of the second microwave trap 14 is nominally above the nominal frequency w0. It can be seen that due to the illustrated tolerance deviation of the door gap T, the nominal frequency w0 falls outside the frequency reduction range for a single microwave trap, and microwaves of the nominal frequency w0 can therefore pass through the door gap T at a relevant level. With a double trap, however, the reduction is significantly broader, so that with the illustrated tolerance deviation of the door gap T, the nominal frequency w0 remains in the fully reduced range.

[0052] List of reference symbols

[0053] 1 cooking appliance

[0054] 2 housings

[0055] 2.1 Cooking chamber wall of the housing

[0056] 2.2 Cooking chamber wall of the housing

[0057] 2.3 Cooking chamber wall of the housing

[0058] 2.4 Cooking chamber wall of the housing

[0059] 2.5 Contact area of ​​the housing

[0060] 3 Cooking chamber

[0061] 4 Cooking chamber opening

[0062] 5 Cooking chamber door

[0063] 5.1 Cooking chamber door frame

[0064] 5.2 Viewing window of the cooking chamber door

[0065] 5.3 End rebate of the cooking chamber door

[0066] 6 circulating air heating

[0067] 7.1 Heating medium for generating radiant heat

[0068] 7.2 Heating means for generating radiant heat

[0069] 8 Heating means for generating microwaves

[0070] 9 fixtures

[0071] 10 food carriers

[0072] 11 Control element

[0073] 12 Advertisement

[0074] 13 first microwave trap

[0075] 13.1 Cavity of the first microwave trap

[0076] 13.2 Trap opening of the first microwave trap

[0077] 13.3 Advance of the first microwave trap

[0078] 14 second microwave trap

[0079] 14.1 Cavity of the second microwave trap

[0080] 14.2 Trap opening of the second microwave trap

[0081] 14.3 Projection of the second microwave trap

[0082] 15 first seal

[0083] 16 grooves

[0084] 17 second seal

[0085] A level

[0086] T door gap w angular frequencies where nominal frequency

Claims

Patent claims 1. A cooking appliance (1), comprising: a housing (2) with a cooking chamber (3) delimited by housing walls (2.1, 2.2, 2.3, 2.4), the cooking chamber (3) having a cooking chamber opening (4); a cooking chamber door (5) for closing the cooking chamber opening (4), the cooking chamber door (5) having a viewing window (5.2); and at least one heating means (8) for generating microwaves of a nominal frequency (wo) in the cooking chamber (3); the cooking chamber door (5) and the housing (2) forming a contact area (2.5) with each other; a surface of the housing (2) in the contact area (2.5) being metallic and defining a contact surface; at least one first seal (15) being formed on the cooking chamber door (5), and a first microwave trap (13) and a second microwave trap (14) being formed one behind the other in the contact area (2.5); and wherein the microwave traps (13, 14) are each designed as a cavity (13.1, 14.1) with a trap opening (13.2, 14.2); wherein the trap opening (13.2) the first microwave trap (13) through the viewing window. (5.2) is covered and the trap opening (14.2) of the second microwave trap (14) is covered by the first seal (15), characterized in that the trap openings (13.2, 14.2) of the door-side first microwave trap (13) and the door-side second microwave trap (14) are opposite the contact surface of the housing (2), and / or a second seal (17) is provided and arranged on the housing (2) in the contact area (2.5), the second seal (17) being made of glass silk.

2. Cooking appliance (1) according to claim 1, wherein the first seal (15) is designed to be liquid-tight, in particular vapor-tight.

3. Cooking appliance (1) according to one of the preceding claims, wherein the first seal (15) is made of a silicone material.

4. Cooking appliance (1) according to one of the preceding claims, wherein the viewing window (5.2) is made of a glass material.

5. Cooking appliance (1) according to one of the preceding claims, wherein the first microwave trap (13) is designed for a resonance frequency below the nominal frequency (wo) and the second microwave trap (14) is designed for a resonance frequency above the nominal frequency (wo).

6. Cooking appliance (1) according to one of the preceding claims, wherein the second seal (17) is arranged in a groove (16) formed on the housing (2) in the contact area (2.5).

7. Cooking appliance (1) according to one of the preceding claims, wherein the second seal (17) is arranged opposite the viewing window (5.2) on the housing (2).

8. Cooking appliance (1) according to one of the preceding claims, comprising a spring element for pressing the cooking chamber door (5) against the housing (2) in the contact area (2.5) and in a closed state of the cooking chamber door (5).

9. Cooking appliance (1) according to one of the preceding claims, wherein at least one microwave trap (13, 14) has a projection (13.3, 14.3) projecting from the trap opening (13.2, 14.2) into the cavity (13.1, 14.1), so that the trap opening (13.2, 14.2) is designed as a channel delimited on both sides.

10. Cooking appliance (1) according to the preceding claim, wherein the projection (13.3, 14.3) is slotted.

11. Cooking appliance (1) according to one of the preceding claims, comprising means for providing a pyrolysis function.

12. Cooking appliance (1) according to one of the preceding claims, designed as an oven.

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