Antenna for detecting microwave radiation and cooking appliance

Abstract

Antenna (30) for detecting microwave radiation with a base body (32) having a hole (38), a first conductor section (34) provided on the base body (32) which, viewed from above, completely surrounds the hole (38), and a second conductor section (36) provided on the base body (32) which is connected to the first conductor section (34), wherein the first conductor section (34) is arranged radially outside the second conductor section (36), and wherein the second conductor section (36) is arranged radially outside the hole (38).

Description

[0001] The invention relates to an antenna for detecting microwave radiation and a cooking appliance with a microwave sensor.

[0002] The use of microwave radiation in cooking appliances for cooking or inspecting food is well known, especially in professional kitchens such as restaurants, canteens, and large-scale catering establishments. When operating the microwave source of these appliances, care must be taken to minimize microwave radiation exposure in the vicinity of the appliance to avoid endangering the user or electrical circuits outside the cooking chamber. In particular, openings in the walls of the cooking chamber represent potential points of microwave emission and require appropriate monitoring.

[0003] Microwave traps, typically installed at openings in the oven wall, prevent microwave radiation from escaping through these openings. However, the effectiveness of such traps can be impaired by contamination, damage, or improper reassembly after maintenance, allowing microwave radiation to escape unnoticed from the cooking chamber.

[0004] From US 2008 / 0 036 689 A1, an antenna system is known that has a base body with a breakthrough.

[0005] US 5 945 963 A shows an antenna that has a base body with a breakthrough.

[0006] The object of the invention is to provide a device that detects microwave radiation exiting through an opening in the oven wall without reducing the cross-section of the opening.

[0007] The problem is solved by an antenna for detecting microwave radiation comprising a base body with a cutout, a first conductor section provided on the base body that completely surrounds the cutout, and a second conductor section provided on the base body that is connected to the first conductor section, wherein the first conductor section is arranged radially outside the second conductor section. The invention provides an antenna with a cutout that can align with the opening to be monitored, so that the opening is not blocked by the antenna. Furthermore, by having the antenna surround the cutout, high antenna sensitivity is achieved. If the first conductor section is arranged radially outside the second conductor section, the second conductor section can circumvent the cutout as closely as possible.

[0008] According to the invention, the second conductor section is arranged radially outside the opening, so that the second conductor area can at least partially surround the shaft without blocking the opening.

[0009] The first conductor section can cover an angular range of less than 360°, making it easy to manufacture.

[0010] However, it is also possible for the second conductor section to cover an angular range of 360° or greater. In this case, care must be taken to ensure that the sections of the conductor covering the same angular range do not come into contact with each other. This can be achieved, for example, by an insulating layer between these sections or by a spiral design of the second conductor section.

[0011] Preferably, the second conductor section has a length on the order of one-quarter of the wavelength of the microwave radiation to be detected, or on the order of one-quarter of the wavelength plus a multiple of half the wavelength, so that reliable detection of the microwave radiation to be detected is possible. "On the order of" here means that the length of the second conductor section is chosen such that the wavelength of the microwave radiation to be detected lies within the full width at half maximum (FWHM) of the antenna's resonance peak. If detection of a frequency band is desired, the wavelength used to select the length of the second conductor section is chosen such that the frequency band to be detected is covered as well as possible by the antenna's resonance peak.

[0012] In one embodiment of the invention, the first conductor section and the second conductor section lie in a common plane and / or the base body is designed to be flat, so that the installation space required by the antenna is as small as possible.

[0013] Preferably, the first conductor section can be grounded and the second conductor section can be connected to a measuring unit via an antenna feed line, so that the antenna can be put into operation in a known and simple way.

[0014] The antenna feed line can be arranged on the second conductor section in such a way that the antenna has an input resistance of 50 ohms.

[0015] The problem is further solved by a cooking appliance comprising a cooking chamber defined by cooking chamber walls, a microwave source capable of generating microwave radiation, and a microwave sensor, wherein at least one of the cooking chamber walls has at least one opening, the microwave sensor completely surrounding a wave extending through the opening. In this way, the reliable detection of microwave radiation emanating from openings from which drive shafts or other elongated objects extend is ensured, where in this context "drive shafts" is understood as a collective term for elongated objects extending from the opening, particularly perpendicularly.

[0016] For example, the microwave sensor is designed in a ring shape so that it can completely surround the opening, thereby improving the sensor's sensitivity. In one embodiment of the invention, a drive shaft, in particular a drive shaft of a fan arranged in the cooking chamber, extends through the opening and / or the microwave sensor. In this way, it is possible to mechanically drive devices in the cooking chamber from outside the cooking chamber without the necessary opening representing an uncontrolled leak for microwave radiation.

[0017] The microwave sensor can be designed as an inverted F-shaped antenna (IFA), thus using a simple antenna structure.

[0018] In one embodiment of the invention, the antenna according to the invention can be used in the cooking appliance, wherein the opening of the antenna is aligned with the opening, so that the opening and thus the wave is completely surrounded by the antenna, whereby any leakage radiation that may occur from the opening is almost completely detected by the antenna.

[0019] In one embodiment of the invention, the base body of the antenna is formed by the cooking chamber wall, with the opening corresponding to the penetration, so that the space requirement for the microwave sensor is limited to the conductor tracks.

[0020] For example, the microwave sensor is located on the side of the cooking chamber wall facing away from the cooking chamber, so that it is not exposed to the cooking chamber atmosphere. This can extend the lifespan of the microwave sensor.

[0021] In one embodiment of the invention, a microwave trap is provided between the microwave sensor and the cooking chamber wall to minimize the leakage of microwave radiation from the cooking chamber.

[0022] Further features and advantages of the invention will become apparent from the following description and from the accompanying drawings, to which reference is made. The drawings show: - Fig. 1 a cooking appliance according to the invention in longitudinal section, - Fig. 2. An enlarged view of the area around an opening of the cooking chamber of the cooking appliance. Fig. 1, - Fig. 3 an antenna according to the invention in top view, - Fig. 4 the antenna according to the invention Fig. 3 in cross-section, and - Fig. 5 an area of ​​a cooking chamber wall of a second embodiment of a cooking appliance according to the invention.

[0023] In Fig. 1 is a cooking appliance 10 shown schematically in longitudinal section.

[0024] The cooking appliance has a cooking chamber 12, which is bounded by cooking chamber walls 14.

[0025] The cooking appliance includes a microwave source 16 which is connected to the cooking chamber 12 and can generate microwave radiation which is propagated into the cooking chamber 12.

[0026] Furthermore, a fan 18 is provided in the cooking chamber 12, which is driven by a motor 21 via a drive shaft 20.

[0027] Of course, instead of or in addition to the fan 18, another mechanically driven component, operated by means of a drive shaft 20, can be provided in the cooking chamber 12. Other elongated components extending through the opening 22 for other purposes are also conceivable.

[0028] The drive shaft 20 extends out of the cooking chamber 12 through an opening 22 in one of the cooking chamber walls 14. In particular, the shaft 20 runs perpendicular to the wall in which the opening 22 is provided.

[0029] A microwave trap 24 is provided on the cooking chamber wall 14 in the area of ​​the opening 22, through which the drive shaft 20 extends. The microwave trap 24 serves to prevent microwave radiation from escaping the cooking chamber 12.

[0030] In the illustrated embodiment, the microwave trap 24 is arranged on the side of the cooking chamber wall 14 facing away from the cooking chamber 12. Of course, the microwave trap 24 can also be located inside the cooking chamber 12 at the opening 22.

[0031] Furthermore, a microwave sensor 26 is provided in the area of ​​the opening 22, which completely surrounds the drive shaft 20. The microwave sensor 26 is, for example, ring-shaped, so that the drive shaft 20 can extend through the microwave sensor 26.

[0032] The microwave sensor 26 can also be arranged on the side of the cooking chamber wall 14 facing away from the cooking chamber 12. The microwave trap 24 is then preferably arranged between the microwave sensor 26 and the cooking chamber wall 14.

[0033] The microwave sensor 26 is preferably designed as an antenna 30, which is located in the Fig. 3 and Fig. 4 is shown.

[0034] In particular, antenna 30 is an inverted F-shaped antenna (IFA).

[0035] The antenna 30 has a base body 32 and a first conductor section 34 as well as a second conductor section 36.

[0036] For example, the ladder sections 34, 36 are provided directly on the base body 32.

[0037] The base body 32 is designed to be flat, whereby the first conductor section 34 and the second conductor section 36 can be formed on the same side of the base body 32 and in one plane.

[0038] In addition, the base body 32 has a central opening 38 which is aligned with the opening 22 in the cooking chamber wall 14.

[0039] The cross-section of the opening 38 is greater than or equal to the cross-section of the opening 22, so that the opening 22 is not obscured by the antenna 30.

[0040] Furthermore, the drive shaft 20 extends through the opening 38, so that the antenna 30 completely surrounds the drive shaft 20.

[0041] The outer contour of the base body 32 describes, for example, a circle, and the opening 38 can also be round, so that the base body 32 forms a ring.

[0042] The base body 32 is advantageously made of a non-conductive material.

[0043] The first conductor section 34 is radially outside the second conductor section 36, and the second conductor section 36 is radially outside the opening 38. Thus, the second conductor section 36 lies radially between the opening 38 and the first conductor section 36.

[0044] The first conductor section 34, the second conductor section 36 and / or the opening 38 can be arranged concentrically to each other and / or to the base body 32.

[0045] The first conductor section 34 can be ring-shaped and completely encloses the opening 38.

[0046] Furthermore, a connection element 40, for example a connector for a coaxial cable, can be provided on the first conductor section 34. The first conductor section 34 can be grounded using the connection element 40.

[0047] A conductive bridge 42 extends between the first conductor section 34 and the second conductor section 36, electrically connecting the first conductor section 34 with the second conductor section 36.

[0048] The bridge 42 extends radially inwards from the first conductor section 34 to the second conductor section 36.

[0049] The second conductor section 36 has a free end 44 and a contacted end 46, with the bridge 42 connecting to the second conductor section 36 at its contacted end 46.

[0050] The second conductor section 36 describes a circular arc around the opening 38. In the embodiment shown, the second conductor section 36 covers an angular range α of less than 360° (but significantly more than 270°).

[0051] However, it is also conceivable that the conductor section covers a full circle or more, i.e., 360° or more. In this case, however, the area of ​​the second conductor section 36 that extends beyond 360° from the first end should not come into contact with the remaining area of ​​the second conductor section 36.

[0052] This could be achieved, for example, by an insulating layer between the two sections of the second conductor segment. It is also conceivable that the second conductor segment could be designed as a spiral whose radius changes with increasing angle of rotation.

[0053] The second conductor section 36 has a length L between the free end 44 and the contacted end 46, which is on the order of one quarter of the wavelength of the microwave radiation to be detected or on the order of one quarter of the wavelength plus a multiple of half the wavelength.

[0054] The length L of the second conductor section 36 thus depends on the wavelength of the microwave radiation generated by the microwave source 16, which is to be detected by the antenna 30. The length L does not have to correspond exactly to one quarter of the wavelength or one quarter of the wavelength plus a multiple of half the wavelength; rather, it is sufficient if the length L is on the order of this magnitude such that the wavelength to be detected is sufficiently close to the resonant wavelength of the antenna 30, allowing for trouble-free detection.

[0055] The second conductor section 36 may also be provided with an antenna feed line 48, with which the second conductor section 36 can be connected to a measuring unit (not shown) or a control unit (not shown) of the cooking appliance 10.

[0056] The antenna feed line 48 extends, for example, from the connection element 40. Furthermore, the antenna feed line 48 can be arranged on the second conductor section 36 such that the antenna 30 has an input impedance of 50 ohms.

[0057] The connection element 40 can be designed as a plug for a coaxial cable.

[0058] Furthermore, the connecting element 40 can be electrically connected to a control unit (not shown) of the cooking appliance 10 in such a way that the first conductor section 34 is grounded and the second conductor section 36 is connected to the measuring unit of the cooking appliance 10 via the antenna supply line 48.

[0059] In Fig.Figure 5 shows a cooking chamber wall 14 of a second embodiment of a cooking appliance. The cooking appliance of the second embodiment differs from that of the first embodiment only in that the antenna 30 is not provided as a separate component, but is designed as part of the cooking chamber wall 14.

[0060] In the second embodiment, the first conductor section 34 and the second conductor section 36 are applied to the cooking chamber wall 14 around the opening 22, which in this case corresponds to the opening 38.

[0061] If the cooking chamber wall 14 is made of a conductive material, an insulating layer (not shown) is necessary between the first conductor section 34, the second conductor section 36 and the bridge 42 on the one hand and the cooking chamber wall 14 on the other.

[0062] Naturally, the features of the first embodiment can be transferred to the antenna 30 of the second embodiment.

Claims

[1] Antenna (30) for detecting microwave radiation comprising a base body (32) having a hole (38), a first conductor section (34) provided on the base body (32) which fully surrounds the hole (38) when viewed from above, and a second conductor section (36) provided on the base body (32) which is connected to the first conductor section (34), wherein the first conductor section (34) is arranged radially outside the second conductor section (36), and wherein the second conductor section (36) is arranged radially outside the hole (38). [2] Antenna according to claim 1, characterized by , that the second conductor section (36) has a length (L) which is on the order of one quarter of the wavelength of the microwave radiation to be detected or on the order of one quarter of the wavelength plus a multiple of half the wavelength. [3] Antenna according to any of the preceding claims, characterized by that the first ladder section (34) and the second ladder section (36) lie in a common plane and / or the base body (32) is flat. [4] Antenna according to any of the preceding claims, characterized by , that the first conductor section (34) is grounded and the second conductor section (36) is connected to a measuring unit via an antenna feed line (48). [5] Antenna according to claim 4, characterized by , that the antenna feed line (48) is arranged on the second conductor section such that the antenna (30) has an input resistance of 50 ohms. [6] Cooking appliance (10) comprising a cooking chamber (12) defined by cooking chamber walls (14), a microwave source (16) capable of generating microwave radiation, and a microwave sensor (26), wherein the microwave sensor (26) completely surrounds a wave (20) extending through an opening (22) in one of the cooking chamber walls (14). [7] Cooking appliance according to claim 6, characterized by , that the microwave sensor (26) is designed in a ring shape. [8] Cooking appliance according to claim 6 or 7, characterized by , that the shaft (20), in particular a drive shaft of a fan (18) arranged in the cooking chamber (12), extends through the opening (22) and / or the microwave sensor (26). [9] Cooking appliance according to any one of claims 6 to 8, characterized by , that the microwave sensor (26) is designed as an inverted F-shaped antenna (IFA). [10] Cooking appliance according to any one of claims 6 to 9, characterized by , that the microwave sensor (26) is an antenna (30) according to one of claims 1 to 5, wherein the opening (38) of the antenna (30) is aligned with the opening (22). [11] Cooking appliance according to claim 10, characterized by , that the base body (32) of the antenna (30) is formed by the cooking chamber wall (14), with the opening (38) corresponding to the opening (22). [12] Cooking appliance according to any one of claims 6 to 11, characterized by , that the microwave sensor (26) is located on the side of the cooking chamber wall (14) facing away from the cooking chamber (12). [13] Cooking appliance according to one of claims 6 to 12, but not referring back to claim 11, characterized by , that a microwave trap (24) is provided between the microwave sensor (26) and the oven wall (14).

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