EP1241923B1 - Microwave oven - Google Patents

Microwave oven Download PDF

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Publication number
EP1241923B1
EP1241923B1 EP02356051A EP02356051A EP1241923B1 EP 1241923 B1 EP1241923 B1 EP 1241923B1 EP 02356051 A EP02356051 A EP 02356051A EP 02356051 A EP02356051 A EP 02356051A EP 1241923 B1 EP1241923 B1 EP 1241923B1
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EP
European Patent Office
Prior art keywords
antenna
microwave oven
waveguide
oven according
microwave
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Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Expired - Lifetime
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EP02356051A
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German (de)
French (fr)
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EP1241923A1 (en
Inventor
Michel Le Roy
Jean-Paul Morizot
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SEB SA
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SEB SA
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    • H—ELECTRICITY
    • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
    • H05B—ELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL
    • H05B6/00—Heating by electric, magnetic or electromagnetic fields
    • H05B6/64—Heating using microwaves
    • H05B6/70—Feed lines
    • H05B6/707—Feed lines using waveguides
    • H—ELECTRICITY
    • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
    • H05B—ELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL
    • H05B6/00—Heating by electric, magnetic or electromagnetic fields
    • H05B6/64—Heating using microwaves
    • H05B6/70—Feed lines
    • H05B6/702—Feed lines using coaxial cables
    • H—ELECTRICITY
    • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
    • H05B—ELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL
    • H05B6/00—Heating by electric, magnetic or electromagnetic fields
    • H05B6/64—Heating using microwaves
    • H05B6/72—Radiators or antennas

Definitions

  • the present invention relates to a heating oven by microwave comprising a microwave generator diffusing microwave energy in a waveguide and controlled by means of programming the operation of the oven, said waveguide emerging in a heating enclosure delimited by a door and by a wall comprising at least one arch and one sole.
  • Heating ovens of this type collide with problem of energy intensity distribution microwave in the heating enclosure. Indeed it is difficult to obtain a homogeneous distribution of energy microwave.
  • the microwave reflections on the wall cause the presence of standing waves with areas where the intensity of microwave energy is weak, and therefore the heating is weak important.
  • a first solution to overcome this problem consists in placing a stirrer called “stirrer” in the microwave field.
  • a classic stirrer has a rotating propeller whose blades move and randomly reflect the waves in the oven cavity.
  • Another commonly used solution of nowadays involves placing the food on a platter rotatable so that it successively crosses low and high energy microwave areas.
  • the object of the present invention is to remedy these disadvantages by improving the distribution of microwave energy in the heating enclosure.
  • a additional objective of the invention is to be able change the distribution of microwave energy into depending on the type of food to be cooked or defrosted.
  • the oven comprises at least one collecting antenna arranged in the waveguide so as to pick up a part of the microwaves diffused in said waveguide, and at least one transmitting antenna adapted to emit micro- waves arranged in the heating enclosure, said collecting and transmitting antennas being connected by an electromagnetic propagation line of length L.
  • the collecting antenna makes it possible to take a part of the microwave energy generated by the oven for broadcast this energy from the transmitting antenna in a specific area of the heating enclosure.
  • the transmitting antenna arranged near an area where the waveguide does not allow to obtain sufficient microwave energy, allows increase the energy density in this area and improve the general distribution of microwaves in the enclosure.
  • the transmitting antenna is an antenna of the plate type with a suitable geometric shape emitting a polarized electromagnetic field circular.
  • This type of antenna transmits in one precise point, a microwave energy field animated by a rotating movement which ensures more uniform heating than a stationary field.
  • phase shift, at a given point of the enclosure, between the microwaves coming from the waveguide and those coming from the transmitting antenna depends on the length L of the propagation line.
  • this length L is calculated so as to obtain at this point of the enclosure, called focal point, a constructive superposition of the microwaves which makes it possible to intensify the heating power.
  • the length of the propagation line is variable between the length L and a length L + ⁇ L by means of an actuator. Thanks to this arrangement, the focus point can be placed in different positions depending on the nature or shape of the food to be cooked, but the focus point can also be moved continuously during a heating program so as to sweep the entire volume of the food.
  • the collecting antenna can be moved in the guide waves thanks to an actuator so as to pick up a more or less amount of microwave energy. So we can adjust the intensity of microwave energy radiated by the transmitting antenna depending on the type of heating to be carried out or type of food. Through example we can go from a homogeneous distribution particularly suitable for cooking vegetables, at a distribution with a peak in heating power applied to the center of the food which is more effective to carry out a defrosting operation.
  • the microwave heating includes a generator microwave 1 diffusing microwave energy into a waveguide 2 and controlled by means of programming 3 for oven operation.
  • Guide of waves 2 opens into a heating enclosure 4 of general parallelepiped shape delimited by a door not shown, and by a wall 5 comprising at least a vault 6 and a sole 7.
  • the outlet of the waveguide 2 is protected by a plate 8 transparent to microwaves.
  • a magnetron connected to a power supply 9.
  • the magnetron 1 delivers in the waveguide 2 a 900 W power at a frequency of 2.45 GHz. All of these elements are housed in a casing 10 which forms the housing of the device.
  • a collecting antenna 11 is arranged in the waveguide 2 so as to pick up part of the microwave energy scattered in said waveguide, a transmitting antenna 12 adapted to emit microwaves is arranged in the heating enclosure 4, said collecting and transmitting antennas being connected by an electromagnetic propagation line 13 of length L.
  • This arrangement makes it possible to take a part of the microwave energy produced to diffuse it in a chosen area of the enclosure 4 and determined by the position of the transmitting antenna 12.
  • the transmitting antenna 12 can be arranged in any region of the heating cabinet 4. But to achieve a homogeneous distribution of energy microwave, the antenna is placed near a region where the energy diffused by the guide outlet wave 2 is lower. Generally in microwave ovens this is in the central area of enclosure 4 that the microwave energy is lower, and especially in the lower part of the central area if the waveguide opens near the arch 6. It is therefore a good idea to place the transmitting antenna in the central region of sole 7.
  • a plate type antenna called "patch antenna "in English.
  • This type of antenna includes usually one or more radiating plates 15 substantially flat, of conductive material, arranged parallel to a conductive surface connected to the mass, called the ground plane.
  • the insulation between the plate radiant, forming the antenna proper, and the plane mass can be realized by a dielectric material or air.
  • the main dimensions of the antenna depend on the wavelength ⁇ of the microwaves emitted and are generally between ⁇ / 4 and ⁇ .
  • the shape of the antenna plate serving as antenna transmitter 12 can be rectangular but it's particularly advantageous to use an antenna with a radiating plate 15 of geometric shape adapted to emit a polarized electromagnetic field circular.
  • a radiating plate 15 of geometric shape adapted to emit a polarized electromagnetic field circular.
  • plate antennas to obtain such a field. These antennas are in general characterized by longitudinal dimensions and substantially equal in cross-section, as shown by Figures 2a and 2b showing two forms of antenna 15.15 'circular polarization.
  • the first form antenna 15 shown in Figure 2a is square with two opposite corners cut 16,17.
  • the second form antenna 15 'shown in Figure 2b is circular with two rectangular notches 16 ', 17' diametrically opposed.
  • the field created by this type of antenna performs a rotational movement about an axis perpendicular to the antenna plate which allows a good distribution microwave energy in the work area. So, it is possible to make a microwave oven without turntable.
  • the transmitting antenna 12 is separated from the area of heating by a protection 18 transparent to microwaves, such as a glass plate arranged parallel to the sole 7. This protects the shock antenna 12 and facilitates cleaning of the heating chamber 4, in particular when the oven is an oven for domestic use.
  • the wall 5 of the heating enclosure is connected to an electrical ground to prevent microwave leakage.
  • We can shoot advantage of this characteristic by using a portion 19 of the wall 5 to constitute the ground plane of the plate antenna 12. This arrangement minimizes the size of the antenna in the enclosure and. reduces manufacturing costs.
  • the radiating plate 15 of the transmitting antenna 12 can be isolated from the portion 19 of the wall forming the ground plane, by an interposed dielectric material such as PTFE. But according to a preferred embodiment the radiating plate 15 of the antenna 12 is held parallel to a distance d from the wall 19 by a conductive support 20 extending from an electromagnetically neutral point 21 of the radiating plate 15 to the wall 19. This electromagnetically neutral point generally corresponds to the geometric center of the antenna as shown by references 21 and 21 'in Figures 2a and 2b. The distance d is chosen so as to obtain a good adaptation in impedance of the antenna.
  • the insulation between the radiating plate 15 thus arranged and the part of the wall 19 constituting the ground plane is provided by air which does not present the problems of aging of the polymer materials.
  • the use of a conductive support 20 simplifies the assembly which can be carried out by a welding point between the plate and the support, and between the support and the sole.
  • the electromagnetic propagation line 13 comprises, in known manner, a conductor disposed at proximity to a surface connected to an electrical ground, the conductor and ground generally being isolated by a dielectric material.
  • a line is used coaxial comprising a conductor 25 surrounded by a circular peripheral shield 26, said conductor 25 being connected to the collecting antenna 11 and to the antenna transmitter 12.
  • the connection to transmitter 12 is produced by connecting the conductor 25 to an eccentric point (27,27 ') of the radiating plate 15.
  • a coaxial line is used comprising an outer shield of tinned aluminum 3.58 mm diameter with PTFE insulation. This line has a small footprint and good ability to the deformation which allow to integrate it easily in the structure of a microwave oven.
  • the power transmissible by such a line is 350 W, which is sufficient for an oven type application of microwave cooking for household use.
  • the microwaves coming from the waveguide 2 and the microwaves emitted by the transmitting antenna 12 are superimposed in the heating enclosure 4 with a certain phase shift.
  • This phase shift at a determined point of the enclosure, depends on the difference between the electromagnetic distance traveled by the microwaves emitted by the waveguide 2 and the electromagnetic distance traveled by the microwaves emitted by the transmitting antenna. 12 from the generator 1.
  • the length L of the propagation line 13 is calculated so as to obtain, at a point 29 of the enclosure, called the focal point, a constructive superposition of the microwaves diffused by the guide waves 2 and microwaves emitted by the transmitting antenna 12. This makes it possible to obtain at the focal point 29 a heating energy equal to the sum of the microwave energies coming from the waveguide and from the transmitting antenna .
  • the length L can be determined so that the focal point 29 of the antenna is located in a known area of the enclosure which normally receives little microwave energy.
  • the focal point 29 can also be chosen so as to obtain a heating peak in a particular zone of the enclosure. For example, to defrost a food it is particularly advantageous to obtain a heating peak in the center of the food generally placed on a dish supported by the plate 18.
  • the propagation line 13 comprises a device making it possible to vary the length of said line between the length L and a length L + ⁇ L .
  • the focus point 29 can be moved along an axis perpendicular to the plate 15 of the antenna depending on the type of heating to be carried out or the shape of the food. For example to defrost a roast of meat, it is preferable that the focal point 29 is located a few centimeters above the protective plate 18. While for baking a pizza, it is preferable to lower the focal point so that it is located in the thickness of the dough.
  • FIG. 3 represents such a device inserted on the coaxial propagation line 13 between the collecting antenna and the transmitting antenna.
  • the two ends (30,31) of the conductor 25 of the propagation line 13 are curved inside a metal housing 32 connected to the peripheral shielding 26 of the coaxial line, so as to be arranged in parallel.
  • a U-shaped conductive part 33 comprising in each of its branches a bore (34,35), is arranged so as to be able to slide along the ends (30,31) while ensuring electrical contact between the conductors.
  • An electromechanical linear actuator 36 located outside of the housing 32, comprises a control rod 37 which makes it possible to move the part the U-shaped part 33.
  • the control rod 37 is made of dielectric material and transparent to microwaves.
  • the displacement of the U- shaped part with a length ⁇ L / 2 of makes it possible to vary the length of the propagation line 13 by ⁇ L . But of course, the length variation device can be produced differently without departing from the scope of the invention.
  • the electromechanical actuator 36 can be connected to the programming means 3 of the oven so that the variation in length of the propagation line 13 is automatic.
  • the programming means 3 of the oven then comprise means for controlling the device for varying the length of the propagation line and means for storing different lengths of the propagation line adapted to the running of different heating programs.
  • the programming means 3 of the oven automatically modify the length L of the propagation line 13.
  • the length L can remain constant during a cooking program, but it can also vary continuously or cyclically, either so that the focal point scans the entire volume of the food, or to take account of changes in the dielectric properties of the food during heating.
  • the collecting antenna 11 arranged in the waveguide 2 can be produced in different forms adapted to capture part of the microwave energy and to transmit this energy to the propagation line 13.
  • the collecting antenna 11 comprises a conductive rod 40 disposed substantially perpendicular to the interior wall of the waveguide 2 and has an apparent height h in the waveguide.
  • the conductive rod 40 can be constituted by the extension of the conductor 25 of the coaxial line 13.
  • the power picked up by the antenna 11 depends on the apparent height h . For example, a rod with a height of 22 mm, placed in the middle of one of the interior faces of the waveguide, makes it possible to collect a power of 150 W.
  • the collecting antenna 11 comprises an actuator making it possible to modify the apparent height h of the collecting antenna in the waveguide 2 so as to capture a quantity of microwave energy more or less important.
  • a collecting antenna 11 of variable height can be produced in a simple manner, as shown in FIG. 4.
  • the antenna 11 comprises a hollow metal cylinder 41 adapted to slide along the rod 40 of the antenna while ensuring electrical contact therewith.
  • An electromechanical linear actuator 42 located outside the waveguide 2 comprises a control rod 43 made of dielectric material and transparent to microwaves which makes it possible to move the hollow cylinder 41 along the rod 40 and thus varies the apparent height h of the collecting antenna 11.
  • the height h of the collecting antenna can vary from a height of 20 mm allowing to pick up a power of 100 W, to a height of 25 mm allowing to capture a power of 200 W.
  • the actuator 42 is connected to the programming means 3 of the oven for the purpose of automatically controlling the power picked up by the collecting antenna 11.
  • the programming means 3 of the oven then comprise means for controlling said actuator and means for memorizing the different heights h of the collecting antenna adapted to the progress of the different heating programs.
  • the microwave energy scattered by the transmitting antenna is automatically adjusted according to the heating program selected by the user. For example, if the user chooses a defrosting program, the programming means increase the height h to the maximum in order to obtain a higher heating intensity in the center of the food. While for a vegetable cooking program, the programming means reduce the height h in order to obtain the most homogeneous distribution of microwave energy possible.
  • the invention provides a solution to the problem of "cold zones" created by standing waves in the heating chamber of previous microwave ovens.
  • it allows automatic modification, importantly and precisely, the distribution of microwave energy, based on information user data on the type of cooking effect, the form or nature of the food.
  • each transmitting antenna can be connected to a collecting antenna by a line of electromagnetic propagation, but we can also use a collecting antenna connected to a line of propagation with ramifications connected to transmitting antennas.

Abstract

The oven has a collector antenna (11) fitted in the waveguide so as to capture a part of the micro-wave energy diffused in the guide. The oven has a emitting antenna (12) designed to emit microwaves which is fitted in the heating enclosure (4). Both antennas are connected by an electromagnetic propagation line (13) of length. Transmitting antenna has radiating plaque (15) of geometric shape designed to emit circular polarized electromagnetic field. Transmitting antenna is arranged in central region of oven base and separated from the heating zone by protection (18) transparent to microwaves. The radiating plaque is maintained parallel at distance (d) from part (19) of the wall by support conductor (20) extending from a neutral electromagnetic point (21) of the plaque to the wall (19). The wave guide outlets into the heating enclosure delimited by a door and wall (5) which includes at least a space (6) and base (7).

Description

La présente invention concerne un four de chauffage par micro-ondes comprenant un générateur de micro-ondes diffusant l'énergie micro-ondes dans un guide d'ondes et commandé par des moyens de programmation du fonctionnement du four, ledit guide d'ondes débouchant dans une enceinte de chauffage délimitée par une porte et par une paroi comprenant au moins une voûte et une sole.The present invention relates to a heating oven by microwave comprising a microwave generator diffusing microwave energy in a waveguide and controlled by means of programming the operation of the oven, said waveguide emerging in a heating enclosure delimited by a door and by a wall comprising at least one arch and one sole.

Un tel four est connu par le document EP 1 329 135.Such an oven is known from document EP 1 329 135.

Les fours de chauffage de ce type se heurtent au problème de la répartition de l'intensité de l'énergie micro-ondes dans l'enceinte de chauffage. En effet il est difficile d'obtenir une répartition homogène de l'énergie micro-ondes. De plus, les réflexions des micro-ondes sur la paroi entraínent la présence d'ondes stationnaires avec des zones où l'intensité de l'énergie micro-ondes est faible, et par conséquent où le chauffage est peu important.Heating ovens of this type collide with problem of energy intensity distribution microwave in the heating enclosure. Indeed it is difficult to obtain a homogeneous distribution of energy microwave. In addition, the microwave reflections on the wall cause the presence of standing waves with areas where the intensity of microwave energy is weak, and therefore the heating is weak important.

Une première solution pour palier ce problème consiste à placer un brasseur d'ondes appelé "stirrer" dans le champ de micro-ondes. Un stirrer classique comporte une hélice rotative dont les pales brassent et réfléchissent de manière aléatoire les ondes dans la cavité du four. Une autre solution couramment employée de nos jours consiste à placer l'aliment sur un plateau rotatif de manière à ce qu'il traverse successivement les zones de faible et haute énergie micro-ondes.A first solution to overcome this problem consists in placing a stirrer called "stirrer" in the microwave field. A classic stirrer has a rotating propeller whose blades move and randomly reflect the waves in the oven cavity. Another commonly used solution of nowadays involves placing the food on a platter rotatable so that it successively crosses low and high energy microwave areas.

Ces solutions ne sont pas pleinement satisfaisantes, notamment dans la région centrale de la cavité où ne règne pas une énergie suffisante. Ainsi, il est pratiquement impossible de réaliser la cuisson d'une pizza sans utiliser un accessoire spécial permettant une meilleure répartition des ondes. Ces solutions ne permettent pas non plus de modifier la répartition de l'énergie micro-ondes en fonction du type d'aliment ou au cours du déroulement de la cuisson. De plus, le moteur et le mécanisme d'entraínement d'un plateau rotatif entraínent un surcoût de fabrication non négligeable.These solutions are not fully satisfactory, especially in the central region of cavity where there is not sufficient energy. So, he is practically impossible to cook a pizza without using a special accessory allowing better wave distribution. These solutions do also do not allow the distribution of microwave energy depending on the type of food or at during the cooking process. In addition, the engine and the drive mechanism of a turntable entail a significant additional manufacturing cost.

Le but de la présente invention est de remédier à ces inconvénients en améliorant la répartition de l'énergie micro-ondes dans l'enceinte de chauffage. Un objectif supplémentaire de l'invention est de pouvoir modifier la répartition de l'énergie micro-ondes en fonction du type d'aliment à cuire ou à décongeler.The object of the present invention is to remedy these disadvantages by improving the distribution of microwave energy in the heating enclosure. A additional objective of the invention is to be able change the distribution of microwave energy into depending on the type of food to be cooked or defrosted.

Selon l'invention, le four comprend au moins une antenne collectrice agencée dans le guide d'onde de manière à capter une partie des micro-ondes diffusées dans ledit guide d'ondes, et au moins une antenne émettrice adaptée à émettre des micro-ondes agencée dans l'enceinte de chauffage, lesdites antennes collectrice et émettrice étant reliées par une ligne de propagation électromagnétique de longueur L.According to the invention, the oven comprises at least one collecting antenna arranged in the waveguide so as to pick up a part of the microwaves diffused in said waveguide, and at least one transmitting antenna adapted to emit micro- waves arranged in the heating enclosure, said collecting and transmitting antennas being connected by an electromagnetic propagation line of length L.

Ainsi l'antenne collectrice permet de prélever une partie de l'énergie micro-ondes générée par le four pour diffuser cette énergie à partir de l'antenne émettrice dans une zone précise de l'enceinte de chauffage. On comprendra donc aisément que l'antenne émettrice, agencée à proximité d'une zone où le guide d'ondes ne permet pas d'obtenir une énergie micro-ondes suffisante, permet d'augmenter la densité d'énergie dans cette zone et d'améliorer la répartition générale des micro-ondes dans l'enceinte.Thus the collecting antenna makes it possible to take a part of the microwave energy generated by the oven for broadcast this energy from the transmitting antenna in a specific area of the heating enclosure. We will therefore easily understand that the transmitting antenna, arranged near an area where the waveguide does not allow to obtain sufficient microwave energy, allows increase the energy density in this area and improve the general distribution of microwaves in the enclosure.

De manière préférentielle, l'antenne émettrice est une antenne du type à plaque de forme géométrique adaptée à émettre un champ électromagnétique à polarisation circulaire. Ce type d'antenne permet d'émettre, en un point précis, un champ d'énergie micro-onde animé d'un mouvement tournant qui assure un chauffage plus homogène qu'un champ stationnaire.Preferably, the transmitting antenna is an antenna of the plate type with a suitable geometric shape emitting a polarized electromagnetic field circular. This type of antenna transmits in one precise point, a microwave energy field animated by a rotating movement which ensures more uniform heating than a stationary field.

En outre, on observe que le déphasage, en un point donné de l'enceinte, entre les micro-ondes provenant du guide d'ondes et celles provenant de l'antenne émettrice dépend de la longueur L de la ligne de propagation. De manière avantageuse cette longueur L est calculée de façon à obtenir en ce point de l'enceinte, appelé point de focalisation, une superposition constructive des micro-ondes qui permet d'intensifier la puissance de chauffage.In addition, it is observed that the phase shift, at a given point of the enclosure, between the microwaves coming from the waveguide and those coming from the transmitting antenna depends on the length L of the propagation line. Advantageously, this length L is calculated so as to obtain at this point of the enclosure, called focal point, a constructive superposition of the microwaves which makes it possible to intensify the heating power.

Selon un mode de réalisation particulièrement avantageux de l'invention, la longueur de la ligne de propagation est variable entre la longueur L et une longueur L+ΔL au moyen d'un actionneur. Grâce à cette disposition le point de focalisation peut être placé en différentes positions selon la nature ou la forme de l'aliment à cuire, mais le point de focalisation peut aussi être déplacé de manière continue au cours d'un programme de chauffage de manière à balayer tout le volume de l'aliment.According to a particularly advantageous embodiment of the invention, the length of the propagation line is variable between the length L and a length L + ΔL by means of an actuator. Thanks to this arrangement, the focus point can be placed in different positions depending on the nature or shape of the food to be cooked, but the focus point can also be moved continuously during a heating program so as to sweep the entire volume of the food.

Selon une autre caractéristique de l'invention, l'antenne collectrice est déplaçable dans le guide d'ondes grâce à un actionneur de manière à capter une quantité d'énergie micro-ondes plus ou moins importante. Ainsi, on peut adapter l'intensité de l'énergie micro-ondes rayonnée par l'antenne émettrice en fonction du type de chauffage à effectuer ou du type d'aliment. Par exemple on peut passer d'une répartition homogène particulièrement appropriée pour cuire des légumes, à une répartition présentant un pic de puissance de chauffage appliquée au centre de l'aliment qui est plus efficace pour effectuer une opération de décongélation. According to another characteristic of the invention, the collecting antenna can be moved in the guide waves thanks to an actuator so as to pick up a more or less amount of microwave energy. So we can adjust the intensity of microwave energy radiated by the transmitting antenna depending on the type of heating to be carried out or type of food. Through example we can go from a homogeneous distribution particularly suitable for cooking vegetables, at a distribution with a peak in heating power applied to the center of the food which is more effective to carry out a defrosting operation.

D'autres caractéristiques et avantages de l'invention ressortiront de la description qui va suivre, donnée à titre d'exemple non limitatif, en référence aux dessins annexés dans lesquels :

  • la figure 1 est une coupe verticale simplifiée d'un four de chauffage par micro-ondes réalisé suivant l'invention;
  • les figures 2a et 2b sont des vues de dessus de deux formes d'antenne à plaque mises en oeuvre pour réaliser l'invention;
  • la figure 3 représente une vue en coupe d'un mode particulier de réalisation d'un dispositif de variation de la longueur d'une ligne de propagation électromagnétique ;
  • la figure 4 représente une vue en coupe d'un mode particulier de réalisation d'une antenne collectrice mise en oeuvre pour réaliser l'invention.
Other characteristics and advantages of the invention will emerge from the description which follows, given by way of nonlimiting example, with reference to the appended drawings in which:
  • Figure 1 is a simplified vertical section of a microwave heating oven produced according to the invention;
  • Figures 2a and 2b are top views of two forms of plate antenna used to realize the invention;
  • Figure 3 shows a sectional view of a particular embodiment of a device for varying the length of an electromagnetic propagation line;
  • FIG. 4 represents a sectional view of a particular embodiment of a collecting antenna used to carry out the invention.

Comme représenté à la figure 1, le four de chauffage par micro-ondes comprend un générateur de micro-ondes 1 diffusant l'énergie micro-ondes dans un guide d'ondes 2 et commandé par des moyens de programmation 3 du fonctionnement du four. Le guide d'ondes 2 débouche dans une enceinte de chauffage 4 de forme générale parallélépipédique délimitée par une porte non représentée, et par une paroi 5 comprenant au moins une voûte 6 et une sole 7. Le débouché du guide d'ondes 2 est protégé par une plaquette 8 transparente aux micro-ondes. Pour le générateur de micro-ondes 1 on utilise, de manière bien connue, un magnétron relié à une alimentation en courant 9. Dans le mode de réalisation décrit le magnétron 1 délivre dans le guide d'ondes 2 une puissance de 900 W à une fréquence de 2,45 GHz. L'ensemble de ces éléments est logé dans un carter 10 qui forme le boítier de l'appareil.As shown in Figure 1, the microwave heating includes a generator microwave 1 diffusing microwave energy into a waveguide 2 and controlled by means of programming 3 for oven operation. Guide of waves 2 opens into a heating enclosure 4 of general parallelepiped shape delimited by a door not shown, and by a wall 5 comprising at least a vault 6 and a sole 7. The outlet of the waveguide 2 is protected by a plate 8 transparent to microwaves. For microwave generator 1, well known way, a magnetron connected to a power supply 9. In the embodiment describes the magnetron 1 delivers in the waveguide 2 a 900 W power at a frequency of 2.45 GHz. All of these elements are housed in a casing 10 which forms the housing of the device.

Selon l'invention, une antenne collectrice 11 est agencée dans le guide d'onde 2 de manière à capter une partie de l'énergie micro-ondes diffusée dans ledit guide d'ondes, une antenne émettrice 12 adaptée à émettre des micro-ondes est agencée dans l'enceinte de chauffage 4, lesdites antennes collectrice et émettrice étant reliées par une ligne de propagation électromagnétique 13 de longueur L. Cette disposition permet de prélever une partie de l'énergie micro-ondes produite pour la diffuser dans une zone choisie de l'enceinte 4 et déterminée par la position de l'antenne émettrice 12.According to the invention, a collecting antenna 11 is arranged in the waveguide 2 so as to pick up part of the microwave energy scattered in said waveguide, a transmitting antenna 12 adapted to emit microwaves is arranged in the heating enclosure 4, said collecting and transmitting antennas being connected by an electromagnetic propagation line 13 of length L. This arrangement makes it possible to take a part of the microwave energy produced to diffuse it in a chosen area of the enclosure 4 and determined by the position of the transmitting antenna 12.

L'antenne émettrice 12 peut être agencée dans n'importe quelle région de l'enceinte de chauffage 4. Mais pour réaliser une répartition homogène de l'énergie micro-ondes, l'antenne est placée à proximité d'une région où l'énergie diffusée par le débouché du guide d'ondes 2 est plus faible. De manière générale dans les fours micro-ondes c'est dans la zone centrale de l'enceinte 4 que l'énergie micro-ondes est plus faible, et surtout dans la partie inférieure de la zone centrale si le guide d'ondes débouche à proximité de la voûte 6. Il est donc judicieux de placer l'antenne émettrice dans la région centrale de la sole 7.The transmitting antenna 12 can be arranged in any region of the heating cabinet 4. But to achieve a homogeneous distribution of energy microwave, the antenna is placed near a region where the energy diffused by the guide outlet wave 2 is lower. Generally in microwave ovens this is in the central area of enclosure 4 that the microwave energy is lower, and especially in the lower part of the central area if the waveguide opens near the arch 6. It is therefore a good idea to place the transmitting antenna in the central region of sole 7.

Pour l'antenne émettrice 12, on utilise de préférence une antenne du type à plaque appelée "patch antenna" en anglais. Ce type d'antenne comprend généralement une ou plusieurs plaques rayonnantes 15 sensiblement planes, en matériau conducteur, disposées parallèlement à une surface conductrice reliée à la masse, appelée plan de masse. L'isolation entre la plaque rayonnante, formant l'antenne proprement dite, et le plan de masse peut être réalisé par un matériau diélectrique ou de l'air. Les dimensions principales de l'antenne dépendent de la longueur d'ondes λ des micro-ondes émises et sont généralement comprises entre λ/4 et λ.For the transmitting antenna 12, preferably a plate type antenna called "patch antenna "in English. This type of antenna includes usually one or more radiating plates 15 substantially flat, of conductive material, arranged parallel to a conductive surface connected to the mass, called the ground plane. The insulation between the plate radiant, forming the antenna proper, and the plane mass can be realized by a dielectric material or air. The main dimensions of the antenna depend on the wavelength λ of the microwaves emitted and are generally between λ / 4 and λ.

La forme de l'antenne à plaque servant d'antenne émettrice 12 peut être rectangulaire, mais il est particulièrement avantageux d'utiliser une antenne avec une plaque rayonnante 15 de forme géométrique adaptée à émettre un champ électromagnétique à polarisation circulaire. Il existe diverses formes d'antennes à plaque permettant d'obtenir un tel champ. Ces antennes sont en général caractérisées par des dimensions longitudinale et transversale sensiblement égales, comme le montre les figures 2a et 2b représentant deux formes d'antenne à polarisation circulaire 15,15'. La première forme d'antenne 15 représentée à la figure 2a est carrée avec deux coins opposés coupés 16,17. La deuxième forme d'antenne 15' représentée à la figure 2b est circulaire avec deux encoches rectangulaires 16',17' diamétralement opposées. Le champ créé par ce type d'antenne effectue un mouvement de rotation autour d'un axe perpendiculaire à la plaque de l'antenne qui permet une bonne répartition de l'énergie micro-ondes dans la zone de travail. Ainsi, il est possible de réaliser un four micro-ondes sans plateau tournant.The shape of the antenna plate serving as antenna transmitter 12 can be rectangular but it's particularly advantageous to use an antenna with a radiating plate 15 of geometric shape adapted to emit a polarized electromagnetic field circular. There are various forms of plate antennas to obtain such a field. These antennas are in general characterized by longitudinal dimensions and substantially equal in cross-section, as shown by Figures 2a and 2b showing two forms of antenna 15.15 'circular polarization. The first form antenna 15 shown in Figure 2a is square with two opposite corners cut 16,17. The second form antenna 15 'shown in Figure 2b is circular with two rectangular notches 16 ', 17' diametrically opposed. The field created by this type of antenna performs a rotational movement about an axis perpendicular to the antenna plate which allows a good distribution microwave energy in the work area. So, it is possible to make a microwave oven without turntable.

L'antenne émettrice 12 est séparée de la zone de chauffage par une protection 18 transparente aux micro-ondes, telle qu'une plaque de verre disposée parallèlement à la sole 7. Ceci permet de protéger l'antenne 12 des chocs et facilite le nettoyage de l'enceinte de chauffage 4, notamment lorsque le four est un four à usage domestique. The transmitting antenna 12 is separated from the area of heating by a protection 18 transparent to microwaves, such as a glass plate arranged parallel to the sole 7. This protects the shock antenna 12 and facilitates cleaning of the heating chamber 4, in particular when the oven is an oven for domestic use.

Dans le mode de réalisation décrit, la paroi 5 de l'enceinte de chauffage est reliée à une masse électrique afin d'éviter toute fuite des micro-ondes. On peut tirer avantageusement profit de cette caractéristique en utilisant une portion 19 de la paroi 5 pour constituer le plan de masse de l'antenne à plaque 12. Cette disposition minimise l'encombrement de l'antenne dans l'enceinte et. réduit les coûts de fabrication.In the embodiment described, the wall 5 of the heating enclosure is connected to an electrical ground to prevent microwave leakage. We can shoot advantage of this characteristic by using a portion 19 of the wall 5 to constitute the ground plane of the plate antenna 12. This arrangement minimizes the size of the antenna in the enclosure and. reduces manufacturing costs.

La plaque rayonnante 15 de l'antenne émettrice 12 peut être isolée de la portion 19 de la paroi formant le plan de masse, par un matériau diélectrique interposé tel que du PTFE. Mais selon un mode préférentiel de réalisation la plaque rayonnante 15 de l'antenne 12 est maintenue parallèlement à une distance d de la paroi 19 par un support conducteur 20 s'étendant d'un point électromagnétiquement neutre 21 de la plaque rayonnante 15 à la paroi 19. Ce point électromagnétiquement neutre correspond généralement au centre géométrique de l'antenne comme le montre les références 21 et 21' des figures 2a et 2b. La distance d est choisie de manière à obtenir une bonne adaptation en impédance de l'antenne. L'isolation entre la plaque rayonnante 15 ainsi agencée et la partie de la paroi 19 constituant le plan de masse est assurée par de l'air qui ne présente pas les problèmes de vieillissement des matériaux polymères. De plus, l'utilisation d'un support conducteur 20 simplifie l'assemblage qui peut être réalisé par un point de soudure entre la plaque et le support, et entre le support et la sole.The radiating plate 15 of the transmitting antenna 12 can be isolated from the portion 19 of the wall forming the ground plane, by an interposed dielectric material such as PTFE. But according to a preferred embodiment the radiating plate 15 of the antenna 12 is held parallel to a distance d from the wall 19 by a conductive support 20 extending from an electromagnetically neutral point 21 of the radiating plate 15 to the wall 19. This electromagnetically neutral point generally corresponds to the geometric center of the antenna as shown by references 21 and 21 'in Figures 2a and 2b. The distance d is chosen so as to obtain a good adaptation in impedance of the antenna. The insulation between the radiating plate 15 thus arranged and the part of the wall 19 constituting the ground plane is provided by air which does not present the problems of aging of the polymer materials. In addition, the use of a conductive support 20 simplifies the assembly which can be carried out by a welding point between the plate and the support, and between the support and the sole.

La ligne de propagation électromagnétique 13 comprend, de manière connue, un conducteur disposé à proximité d'une surface reliée à une masse électrique, le conducteur et la masse étant généralement isolés par un matériau diélectrique. Dans le but de pouvoir facilement déformer la ligne de propagation tout en garantissant une étanchéité absolue aux micro-ondes, on utilise une ligne coaxiale comprenant un conducteur 25 entouré d'un blindage périphérique circulaire 26, ledit conducteur 25 étant connecté à l'antenne collectrice 11 et à l'antenne émettrice 12. La connexion à l'antenne émettrice 12 est réalisé en reliant le conducteur 25 à point excentré (27,27') de la plaque rayonnante 15. Dans le mode de réalisation décrit, on utilise une ligne coaxiale comportant un blindage extérieur en aluminium étamé d'un diamètre de 3,58 mm avec un isolant en PTFE. Cette ligne présente un encombrement réduit et une bonne aptitude à la déformation qui permettent de l'intégrer facilement dans la structure d'un four micro-ondes. La puissance transmissible par une telle ligne est de 350 W, ce qui est suffisant pour une application de type four de cuisson à micro-ondes pour usage domestique.The electromagnetic propagation line 13 comprises, in known manner, a conductor disposed at proximity to a surface connected to an electrical ground, the conductor and ground generally being isolated by a dielectric material. In order to be able to easily distort the propagation line while ensuring absolute microwave resistance, a line is used coaxial comprising a conductor 25 surrounded by a circular peripheral shield 26, said conductor 25 being connected to the collecting antenna 11 and to the antenna transmitter 12. The connection to transmitter 12 is produced by connecting the conductor 25 to an eccentric point (27,27 ') of the radiating plate 15. In the embodiment described, a coaxial line is used comprising an outer shield of tinned aluminum 3.58 mm diameter with PTFE insulation. This line has a small footprint and good ability to the deformation which allow to integrate it easily in the structure of a microwave oven. The power transmissible by such a line is 350 W, which is sufficient for an oven type application of microwave cooking for household use.

Les micro-ondes provenant du guide d'ondes 2 et les micro-ondes émisses par l'antenne émettrice 12 se superposent dans l'enceinte de chauffage 4 avec un certain déphasage. Ce déphasage, en un point déterminé de l'enceinte, dépend de la différence entre la distance électromagnétique parcourue par les micro-ondes diffusées par le guide d'ondes 2 et la distance électromagnétique parcourue par les micro-ondes émises par l'antenne émettrice 12 depuis le générateur 1. Avantageusement, la longueur L de la ligne de propagation 13 est calculée de manière à obtenir en un point 29 de l'enceinte, appelé point de focalisation, une superposition constructive des micro-ondes diffusées par le guide d'ondes 2 et des micro-ondes émises par l'antenne émettrice 12. Ceci permet d'obtenir au point de focalisation 29 une énergie de chauffage égale à la somme des énergies micro-ondes provenant du guide d'ondes et de l'antenne émettrice. The microwaves coming from the waveguide 2 and the microwaves emitted by the transmitting antenna 12 are superimposed in the heating enclosure 4 with a certain phase shift. This phase shift, at a determined point of the enclosure, depends on the difference between the electromagnetic distance traveled by the microwaves emitted by the waveguide 2 and the electromagnetic distance traveled by the microwaves emitted by the transmitting antenna. 12 from the generator 1. Advantageously, the length L of the propagation line 13 is calculated so as to obtain, at a point 29 of the enclosure, called the focal point, a constructive superposition of the microwaves diffused by the guide waves 2 and microwaves emitted by the transmitting antenna 12. This makes it possible to obtain at the focal point 29 a heating energy equal to the sum of the microwave energies coming from the waveguide and from the transmitting antenna .

La longueur L peut être déterminée pour que le point de focalisation 29 de l'antenne soit situé dans une zone connue de l'enceinte qui normalement reçoit peu d'énergie micro-ondes. Mais le point de focalisation 29 peut aussi être choisi de manière à obtenir un pic de chauffage dans une zone particulière de l'enceinte. Par exemple, pour décongeler un aliment il est particulièrement avantageux d'obtenir un pic de chauffage au centre de l'aliment placé généralement sur un plat supporté par la plaque 18.The length L can be determined so that the focal point 29 of the antenna is located in a known area of the enclosure which normally receives little microwave energy. However, the focal point 29 can also be chosen so as to obtain a heating peak in a particular zone of the enclosure. For example, to defrost a food it is particularly advantageous to obtain a heating peak in the center of the food generally placed on a dish supported by the plate 18.

Selon une caractéristique particulièrement avantageuse de l'invention, la ligne de propagation 13 comporte un dispositif permettant de faire varier la longueur de ladite ligne entre la longueur L et une longueur L+ΔL. Ainsi le point de focalisation 29 peut être déplacé selon un axe perpendiculaire à la plaque 15 de l'antenne en fonction du type de chauffage à réaliser ou de la forme de l'aliment. Par exemple pour décongeler un rôti de viande, il est préférable que le point de focalisation 29 soit situé à quelques centimètres au-dessus de la plaque de protection 18. Tandis que pour cuire une pizza, il est préférable d'abaisser le point de focalisation pour qu'il soit situé dans l'épaisseur de la pâte.According to a particularly advantageous characteristic of the invention, the propagation line 13 comprises a device making it possible to vary the length of said line between the length L and a length L + ΔL . Thus the focus point 29 can be moved along an axis perpendicular to the plate 15 of the antenna depending on the type of heating to be carried out or the shape of the food. For example to defrost a roast of meat, it is preferable that the focal point 29 is located a few centimeters above the protective plate 18. While for baking a pizza, it is preferable to lower the focal point so that it is located in the thickness of the dough.

La figure 3 représente un tel dispositif inséré sur la ligne de propagation coaxiale 13 entre l'antenne collectrice et l'antenne émettrice. Les deux extrémités (30,31) du conducteur 25 de la ligne de propagation 13 sont recourbées à l'intérieur d'un boítier métallique 32 relié au blindage périphérique 26 de la ligne coaxiale, de manière à être disposées parallèlement. Une pièce conductrice en U 33, comportant dans chacune de ses branches un alésage (34,35), est agencée de manière à pouvoir coulisser le long des extrémités (30,31) tout en assurant un contact électrique entre les conducteurs. Un actionneur linéaire électromécanique 36, situé à l'extérieur du boítier 32, comporte une tige de commande 37 qui permet de déplacer la pièce la pièce en U 33. La tige de commande 37 est réalisé en matériau diélectrique et transparent aux micro-ondes. Le déplacement de la pièce en U d'une longueur ΔL/2 de permet de faire varier la longueur de la ligne de propagation 13 de ΔL. Mais bien entendu, le dispositif de variation de longueur peut être réalisé différemment sans sortir du cadre de l'invention.FIG. 3 represents such a device inserted on the coaxial propagation line 13 between the collecting antenna and the transmitting antenna. The two ends (30,31) of the conductor 25 of the propagation line 13 are curved inside a metal housing 32 connected to the peripheral shielding 26 of the coaxial line, so as to be arranged in parallel. A U-shaped conductive part 33, comprising in each of its branches a bore (34,35), is arranged so as to be able to slide along the ends (30,31) while ensuring electrical contact between the conductors. An electromechanical linear actuator 36, located outside of the housing 32, comprises a control rod 37 which makes it possible to move the part the U-shaped part 33. The control rod 37 is made of dielectric material and transparent to microwaves. The displacement of the U- shaped part with a length ΔL / 2 of makes it possible to vary the length of the propagation line 13 by ΔL . But of course, the length variation device can be produced differently without departing from the scope of the invention.

L'actionneur électromécanique 36 peut être relié aux moyens de programmation 3 du four afin que la variation de longueur de la ligne de propagation 13 soit automatique. Les moyens de programmation 3 du four comportent alors des moyens de commande du dispositif de variation de longueur de la ligne de propagation et des moyens de mémorisation de différentes longueurs de la ligne de propagation adaptées au déroulement de différents programmes de chauffage. Ainsi, selon le programme de chauffage sélectionné par l'utilisateur, les moyens de programmation 3 du four modifient automatiquement la longueur L de la ligne de propagation 13. La longueur L peut demeurer constante au cours d'un programme de cuisson, mais elle peut aussi varier continûment ou cycliquement, soit pour que le point de focalisation balaye tout le volume de l'aliment, soit pour tenir compte des modifications des propriétés diélectrique de l'aliment au cours du chauffage.The electromechanical actuator 36 can be connected to the programming means 3 of the oven so that the variation in length of the propagation line 13 is automatic. The programming means 3 of the oven then comprise means for controlling the device for varying the length of the propagation line and means for storing different lengths of the propagation line adapted to the running of different heating programs. Thus, according to the heating program selected by the user, the programming means 3 of the oven automatically modify the length L of the propagation line 13. The length L can remain constant during a cooking program, but it can also vary continuously or cyclically, either so that the focal point scans the entire volume of the food, or to take account of changes in the dielectric properties of the food during heating.

L'antenne collectrice 11 agencée dans le guide d'ondes 2 peut être réalisée sous différentes formes adaptées à capter une partie de l'énergie micro-ondes et à transmettre cette énergie à la ligne de propagation 13. Dans le mode de réalisation décrit, l'antenne collectrice 11 comprend une tige conductrice 40 disposée sensiblement perpendiculaire à la paroi intérieure du guide d'onde 2 et présente une hauteur apparente h dans le guide d'ondes. La tige conductrice 40 peut être constitué par le prolongement du conducteur 25 de la ligne coaxiale 13. La puissance captée par l'antenne 11 dépend de la hauteur apparente h. A titre d'exemple, une tige d'une hauteur de 22 mm, disposée au milieu d'une des faces intérieures du guide d'ondes, permet de collecter une puissance de 150 W.The collecting antenna 11 arranged in the waveguide 2 can be produced in different forms adapted to capture part of the microwave energy and to transmit this energy to the propagation line 13. In the embodiment described, the collecting antenna 11 comprises a conductive rod 40 disposed substantially perpendicular to the interior wall of the waveguide 2 and has an apparent height h in the waveguide. The conductive rod 40 can be constituted by the extension of the conductor 25 of the coaxial line 13. The power picked up by the antenna 11 depends on the apparent height h . For example, a rod with a height of 22 mm, placed in the middle of one of the interior faces of the waveguide, makes it possible to collect a power of 150 W.

Selon une caractéristique particulièrement avantageuse de l'invention, l'antenne collectrice 11 comporte un actionneur permettant de modifier la hauteur apparente h de l'antenne collectrice dans le guide d'ondes 2 de manière à capter une quantité d'énergie micro-ondes plus ou moins importante. Une telle antenne collectrice 11 de hauteur variable peut être réalisée de manière simple, comme le montre la figure 4. Pour ce mode de réalisation, l'antenne 11 comprend un cylindre métallique creux 41 adapté à coulisser le long de la tige 40 de l'antenne tout en assurant un contact électrique avec celle-ci. Un actionneur linéaire électromécanique 42 situé à l'extérieur du guide d'ondes 2 comporte un barreau de commande 43 en matériau diélectrique et transparent aux micro-ondes qui permet de déplacer le cylindre creux 41 le long de la tige 40 et fait varier ainsi la hauteur apparente h de l'antenne collectrice 11. A titre d'exemple, la hauteur h de l'antenne collectrice peut varier d'une hauteur de 20 mm permettant de capter une puissance de 100 W, à une hauteur de 25 mm permettant de capter une puissance de 200 W.According to a particularly advantageous characteristic of the invention, the collecting antenna 11 comprises an actuator making it possible to modify the apparent height h of the collecting antenna in the waveguide 2 so as to capture a quantity of microwave energy more or less important. Such a collecting antenna 11 of variable height can be produced in a simple manner, as shown in FIG. 4. For this embodiment, the antenna 11 comprises a hollow metal cylinder 41 adapted to slide along the rod 40 of the antenna while ensuring electrical contact therewith. An electromechanical linear actuator 42 located outside the waveguide 2 comprises a control rod 43 made of dielectric material and transparent to microwaves which makes it possible to move the hollow cylinder 41 along the rod 40 and thus varies the apparent height h of the collecting antenna 11. By way of example, the height h of the collecting antenna can vary from a height of 20 mm allowing to pick up a power of 100 W, to a height of 25 mm allowing to capture a power of 200 W.

L'actionneur 42 est relié aux moyens de programmation 3 du four dans le but de commander automatiquement la puissance captée par l'antenne collectrice 11. Les moyens de programmation 3 du four comportent alors des moyens de commande dudit actionneur et des moyens de mémorisation des différentes hauteurs h de l'antenne collectrice adaptées au déroulement des différents programmes de chauffage. Ainsi l'énergie micro-ondes diffusée par l'antenne émettrice est automatiquement ajustée en fonction du programme de chauffage sélectionné par l'utilisateur. Par exemple, si l'utilisateur choisi un programme de décongélation, les moyens de programmation augmentent la hauteur h au maximum afin d'obtenir une intensité de chauffage plus importante au centre de l'aliment. Tandis que pour un programme de cuisson de légumes, les moyens de programmations réduisent la hauteur h dans le but d'obtenir une répartition de l'énergie micro-ondes la plus homogène possible.The actuator 42 is connected to the programming means 3 of the oven for the purpose of automatically controlling the power picked up by the collecting antenna 11. The programming means 3 of the oven then comprise means for controlling said actuator and means for memorizing the different heights h of the collecting antenna adapted to the progress of the different heating programs. Thus the microwave energy scattered by the transmitting antenna is automatically adjusted according to the heating program selected by the user. For example, if the user chooses a defrosting program, the programming means increase the height h to the maximum in order to obtain a higher heating intensity in the center of the food. While for a vegetable cooking program, the programming means reduce the height h in order to obtain the most homogeneous distribution of microwave energy possible.

L'invention apporte une solution au problème des "zones froides" créées par les ondes stationnaires dans l'enceinte de chauffage des fours micro-ondes antérieurs. De plus elle permet de modifier automatiquement, de manière importante et précise, la répartition de l'énergie micro-ondes, en fonction des informations données par l'utilisateur concernant le type de cuisson à effectuer, la forme ou la nature de l'aliment.The invention provides a solution to the problem of "cold zones" created by standing waves in the heating chamber of previous microwave ovens. In addition, it allows automatic modification, importantly and precisely, the distribution of microwave energy, based on information user data on the type of cooking effect, the form or nature of the food.

Le mode de réalisation décrit ci-dessus n'est pas limitatif, de nombreux aménagements peuvent être apportés sans sortir du cadre de l'invention. Par exemple, il est possible de multiplier le nombre d'antenne émettrice dans l'enceinte de chauffage afin de contrôler la répartition de l'énergie micro-ondes dans différentes zones. Ces antennes émettrices multiples peuvent être alimentées de différentes manières. Chaque antenne émettrice peut être reliée à une antenne collectrice par une ligne de propagation électromagnétique, mais on peut aussi utiliser une antenne collectrice reliée à une ligne de propagation comportant des ramifications connectées aux antennes émettrices.The embodiment described above is not restrictive, many adjustments can be made without departing from the scope of the invention. For example, it is possible to multiply the number of transmitting antenna in the heating chamber to control the distribution microwave energy in different areas. These multiple transmitting antennas can be powered from different ways. Each transmitting antenna can be connected to a collecting antenna by a line of electromagnetic propagation, but we can also use a collecting antenna connected to a line of propagation with ramifications connected to transmitting antennas.

Claims (14)

  1. A microwave oven comprising a microwave generator (1) delivering microwave energy into a waveguide (2) and controlled by programming means (3) for programming operation of the oven, said waveguide (2) opening out into a heating chamber (4) defined by a door and by a wall (5) which comprises at least a ceiling (6) and a soleplate (7),
       the oven being characterized in that at least one pick-up antenna (11) is arranged in the waveguide (2) so as to pick up a fraction of the microwave energy delivered into said waveguide, and that at least one transmitter antenna (12) adapted to transmit microwaves is arranged in the heating chamber (4), said pick-up and transmitter antennas being interconnected by an electromagnetic propagation line (13) of length L.
  2. A microwave oven according to claim 1, characterized in that the transmitter antenna (12) is a plate type antenna.
  3. A microwave oven according to claim 2, characterized in that the transmitter antenna (12) has a radiating plate (15) of a geometrical shape adapted to transmit an electromagnetic field that is circularly polarized.
  4. A microwave oven according to claim 2 or claim 3, characterized in that the transmitter antenna (12) is disposed in the central region of the soleplate (7).
  5. A microwave oven according to any one of claims 2 to 4, characterized in that the transmitter antenna (12) is separated from the heating zone by protection (18) that is transparent to microwaves.
  6. A microwave oven according to any one of claims 2 to 5, in which the wall (5) of the chamber (4) is connected to electrical ground, the oven being characterized in that the ground plane of the transmitter antenna (12) is constituted by a portion (19) of the wall of the chamber (4).
  7. A microwave oven according to claim 6, characterized in that the radiating plate (15) of the transmitter antenna (12) is held parallel to the wall portion (9) at a distance d by a conductive support (20) extending from an electromagnetically neutral point (21) of the radiating plate (15) to the wall (19).
  8. A microwave oven according to any one of claims 1 to 7, characterized in that the electromagnetic propagation line (13) is a coaxial line comprising a conductor (25) surrounded by peripheral shielding (26), said conductor (25) being connected to the pick-up antenna (11) and to the transmitter antenna (12).
  9. A microwave oven according to any one of claims 1 to 8, characterized in that the length L of the propagation line (13) is calculated in such a manner as to obtain constructive superposition of the microwaves delivered by the waveguide (2) and the microwaves transmitted by the transmitter antenna (12) at a point (29) within the enclosure referred to as a focus point.
  10. A microwave oven according to any one of claims 1 to 9, characterized in that the propagation line (13) includes a device enabling the length of said line to be varied between the length L and a length L + ΔL.
  11. A microwave oven according to claim 10, characterized in that the programming means (3) of the oven include means for controlling the device for varying the length of the propagation line (13) and means for storing different lengths for the propagation line adapted to performing different heating programs.
  12. A microwave oven according to any one of claims 1 to 11, characterized in that the pick-up antenna (11) comprises a conductor rod (40) disposed substantially perpendicularly to the inside wall of the waveguide (2) and presenting an apparent height h within the waveguide.
  13. A microwave oven according to claim 12, characterized in that the pick-up antenna (11) includes an actuator enabling the apparent height h of the pick-up antenna within the waveguide to be modified.
  14. A microwave oven according to claim 13, characterized in that the programming means (3) of the oven include means for controlling said actuator and means for storing different heights h for the pick-up antenna adapted to performing different heating programs.
EP02356051A 2001-03-13 2002-03-13 Microwave oven Expired - Lifetime EP1241923B1 (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
FR0103426A FR2822337B1 (en) 2001-03-13 2001-03-13 MICROWAVE HEATING OVEN
FR0103426 2001-03-13

Publications (2)

Publication Number Publication Date
EP1241923A1 EP1241923A1 (en) 2002-09-18
EP1241923B1 true EP1241923B1 (en) 2004-07-07

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EP02356051A Expired - Lifetime EP1241923B1 (en) 2001-03-13 2002-03-13 Microwave oven

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EP (1) EP1241923B1 (en)
AT (1) ATE270813T1 (en)
DE (1) DE60200699D1 (en)
ES (1) ES2222439T3 (en)
FR (1) FR2822337B1 (en)

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US8941040B2 (en) 2006-02-21 2015-01-27 Goji Limited Electromagnetic heating

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DE102006007734B3 (en) * 2006-02-20 2007-10-25 Topinox Sarl Microwave antenna structure for a cooking appliance and cooking appliance with such a microwave antenna structure
US10674570B2 (en) 2006-02-21 2020-06-02 Goji Limited System and method for applying electromagnetic energy
US8653482B2 (en) 2006-02-21 2014-02-18 Goji Limited RF controlled freezing
DE102007035359B4 (en) * 2007-07-27 2012-09-20 Rational Ag Coupling device for microwave transmission in a food processing device
DE102007035357B4 (en) 2007-07-27 2012-08-30 Rational Ag Antenna structure for a cooking appliance and cooking appliance with such an antenna structure
EP2187702A1 (en) 2008-11-17 2010-05-19 Topinox Sarl Cooking device with microwave heating
EP3177109A1 (en) * 2015-12-04 2017-06-07 Electrolux Appliances Aktiebolag Microwave oven
CN113300097A (en) * 2021-05-12 2021-08-24 北京梦之墨科技有限公司 Communication glass, door body with box-type structure and microwave oven
CN116033613A (en) * 2021-10-25 2023-04-28 青岛海尔电冰箱有限公司 Heating device
CN116033611A (en) * 2021-10-25 2023-04-28 青岛海尔电冰箱有限公司 Heating device
DE102022109511A1 (en) * 2022-04-20 2023-10-26 Muegge Gmbh Device for supplying microwaves into a treatment room

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JPH04188592A (en) * 1990-11-20 1992-07-07 Sharp Corp Microwave oven
KR950016447A (en) * 1993-11-15 1995-06-17 사토 후미오 High frequency heating device and control method
US6175104B1 (en) * 1998-09-04 2001-01-16 Cem Corporation Microwave probe applicator for physical and chemical processes
JP2000133433A (en) * 1998-10-29 2000-05-12 Sharp Corp High frequency heating device
FR2815512B1 (en) * 2000-10-18 2008-06-06 Moulinex Sa DEVICE FOR HEATING A MATERIAL BY APPLYING MICROWAVES

Cited By (1)

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Publication number Priority date Publication date Assignee Title
US8941040B2 (en) 2006-02-21 2015-01-27 Goji Limited Electromagnetic heating

Also Published As

Publication number Publication date
ATE270813T1 (en) 2004-07-15
EP1241923A1 (en) 2002-09-18
DE60200699D1 (en) 2004-08-12
FR2822337A1 (en) 2002-09-20
ES2222439T3 (en) 2005-02-01
FR2822337B1 (en) 2003-10-17

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