Cooking hob and method for operating such a cooking hob

Abstract

Cooking surface (11, 111) with a cooking surface (12, 112) and several induction heating coils (20, 120) arranged below it for heating a cooking vessel (25, 125) placed on the cooking surface (12, 112), characterized in that - the induction heating coils (20, 120) are designed to be non-movable and are stationary during operation of the hob (11, 111), - magnetic field steering elements (22, 122) are arranged above the induction heating coils (20, 120) and below the hob plate (12, 112), - the magnetic field steering elements (22, 122) are designed to be movable during operation of the cooktop (11, 111), - the magnetic field steering elements (22, 122) are designed to transmit or transport heating power or heating energy from at least one induction heating coil (20, 120) to the cooking vessel (25, 125).

Description

Area of ​​application and state of the art

[0001] The invention relates to a cooktop comprising a cooktop plate and a plurality of induction heating coils arranged underneath for heating a cooking vessel placed on the cooktop plate. Furthermore, the invention relates to a method for operating such a cooktop.

[0002] DE 10 2015 203 316 A1 discloses that the induction heating coils in an induction hob can be moved beneath the hob plate. They can be moved individually or in groups beneath a cooking vessel placed at essentially any location on the hob plate in such a way that they can heat it effectively or even optimally. This allows a cooking vessel to be placed at essentially any location on the hob plate and still be heated effectively or even optimally.

[0003] WO 2015 / 074 770 A1 discloses a method for operating such a cooktop. It involves using a pot detection sensor to determine whether and where a cooking vessel is placed on the cooktop.

[0004] However, moving induction heating coils or heating elements in general in a hob is considered disadvantageous or at least very complex, since they ultimately have to be connected to an electrical power supply and possibly to control cables.

[0005] DE 10 2008 064 731 A1 discloses another induction hob with induction heating coils, in which, as is usual, field guiding elements or magnetic field steering elements are fixedly arranged beneath the induction heating coils. These induction heating coils can be moved along certain predetermined paths.

[0006] DE 10 2014 224 051 A1 discloses a cooktop with a cooktop plate, in which several rectangular induction heating coils are arranged beneath a cooktop surface. Sensor coils are arranged above the induction heating coils. Spacers are provided above the coil windings of the induction heating coils, extending toward the underside of the cooktop surface.

[0007] DE 2 453 169 A1 discloses an induction heating device in the form of a hob. A ferromagnetic plate is attached to the base of a cooking vessel to be heated. Task and solution

[0008] The invention is based on the object of creating a hob as mentioned above and a method for its operation, with which problems of the prior art can be avoided and, in particular, it is possible to construct a hob that is suitable for use and, at the same time, to operate it comfortably and reliably.

[0009] This object is achieved by a hob having the features of claim 1 and by a method for its operation having the features of claim 8. Advantageous and preferred embodiments of the invention are the subject of the further claims and are explained in more detail below. Some of the features are mentioned and explained only for the hob or only for the method for its operation. However, they are intended to be able to apply independently and independently of one another both to such a hob and to a method for its operation. The wording of the claims is incorporated into the content of the description by express reference.

[0010] The cooktop is designed to have a cooking plate and several induction heating coils arranged underneath, allowing a cooking vessel placed on the plate to be heated. The induction heating coils are fixed and do not move during operation of the cooktop. Advantageously, several cooking vessels can also be placed and heated on them.

[0011] According to the invention, so-called passive heating elements in the form of magnetic field steering elements are arranged above the induction heating coils and below the hob plate, i.e., between the induction heating coils and a cooking vessel placed thereon. These magnetic field steering elements can advantageously be arranged in an intermediate plane that runs just below the hob plate and above the induction heating coils, or between the planes formed below by the induction heating coils and above by the hob plate or its underside. The magnetic field steering elements are arranged or designed to be movable during operation of the hob, advantageously in an aforementioned intermediate plane, i.e., laterally or in a lateral direction.

[0012] Above all, the magnetic field steering elements are designed to transmit or transport heating power or heating energy from at least one induction heating coil to or into the cooking vessel. They can therefore, in a simplified manner, direct an alternating magnetic field or its heating power or heating energy. If the induction heating coils are advantageously stationary or designed to be immobile, the magnetic field steering elements can be moved in such a way that they bring the heating power or heating energy from at least one induction heating coil, possibly also from several or at least two induction heating coils, to the cooking vessel or introduce it into the cooking vessel, in particular into the base of the cooking vessel. This makes it possible to achieve the result that the at least one induction heating coil does not necessarily have to be moved in order to adapt its position to that of a cooking vessel in place for the best possible heating.Since the magnetic field steering elements are advantageously passive in that they do not require any electrical power supply or control via electrical signals, their mobility is relatively easy to implement. They can then be designed without any electrical connections.

[0013] In a further embodiment of the invention, at least one magnetic field steering element can comprise or be a so-called Halbach array of magnets or permanent magnets. Reference is made, for example, to EP 2 953 424 A1 or DE 10 2016 206 477 A1. If this magnetic field steering element or the Halbach array is moved to the appropriate location between the induction heating coil and the cooking vessel, it can also focus the magnetic field at different locations and thus also transmit or transport the heating power or heating energy to the cooking vessel in the desired manner.

[0014] In an embodiment of the invention, at least one magnetic field steering element can consist of or comprise ferritic material. It can correspond to or comprise known flat ferrite rods, such as those currently used, for example, in induction heating coils for cooktops and are placed on the underside of an induction heating coil, with the magnetic field steering element or the ferritic material being placed flat on the top side of an induction heating coil. Such a flat, elongated rod shape is also considered advantageous in the present case because, among other things, it results in a low overall height. Particularly advantageously, a magnetic field steering element comprises several such parts made of ferritic material, which can be moved either individually or together, for example in a star-shaped arrangement.

[0015] It is possible for at least one magnetic field steering element to comprise a material for magnetic field shielding. This also allows the magnetic field of the induction heating coil, and thus the heating power or heating energy, to be directed or directed, at least to a certain extent, toward a cooking vessel.

[0016] In an advantageous embodiment of the invention, at least two of the above-described magnetic field steering elements can be provided per induction heating coil, advantageously even three or four. This also depends on how many induction heating coils are provided in the hob and how they are distributed. If, in accordance with conventional hobs, only four or only six induction heating coils are provided, which form their own discrete and precisely defined cooking zones, then in a first case, for example, two or three magnetic field steering elements can be provided for each induction heating coil. These can then be moved in spatial proximity to this induction heating coil in order to be able to heat cooking vessels in a targeted manner, even if they are not placed directly over this induction heating coil, as would be optimal, but with some offset from it. Such an offset can be 1 cm to 5 cm or a maximum of 10 cm.

[0017] In a second case, a total of six to ten magnetic field steering elements can be provided in the cooktop for such discrete induction heating coils, which are then freely movable. They can be moved to the exact location where a cooking vessel placed in the area of ​​an induction heating coil is to be heated.

[0018] In an alternative embodiment of the invention, a hob can have a plurality of distributed induction heating coils that are adjacent to one another or are adjacent to one another and essentially cover a large part of the hob, in particular at least one heating area. Such an induction hob is known, for example, from DE 10 2006 054 973 A1, to which explicit reference is hereby made. Since cooking vessels can be placed essentially freely or arbitrarily and can still be heated inductively, the magnetic field steering elements should be intended to conduct or transport the heating power or heating energy from at least one induction heating coil as effectively as possible to a cooking vessel placed on the hob plate. This induction heating coil has the greatest coverage by the cooking vessel of all induction heating coils.By moving magnetic field steering elements into this area, additional induction heating coils can then possibly be used to introduce heat output or heating energy into the cooking vessel for heating purposes.

[0019] In a further possible embodiment of the invention, the induction heating coils can be of similar design, preferably identical, particularly in the aforementioned alternative embodiment with a plurality of distributed induction heating coils that, adjacent to one another, cover a large portion of the heating area with only small gaps between them. In principle, the magnetic field steering elements can also be of similar or identical design, although not all magnetic field steering elements necessarily have to be movable. It may be sufficient if some or most of the magnetic field steering elements are movable.

[0020] In a further embodiment of the invention, it is generally possible for the magnetic field steering elements not to be provided in a single size, but in several different sizes, for example, two sizes. Thus, small and large magnetic field steering elements can be provided, with the small magnetic field steering elements being particularly movable and enabling, so to speak, finely graduated surface coverage and transmission of heating power.

[0021] As explained above, the mobility of the magnetic field steering elements can be provided such that some of them are only freely movable within a partial area of ​​the hob or within a partial area of ​​the heating area of ​​the hob. Such a partial area can be a quarter or a sixth of the area of ​​the heating area, with the heating area preferably being regularly divided into equally sized partial areas. For such a partial area, it can also be provided that at least one magnetic field steering element is stationary or fixed in place. At least one further magnetic field steering element per partial area can then have the mobility mentioned above and, in a suitable position, serve in addition to the other stationary magnetic field steering element for aligning the magnetic field or for transmitting or transporting the heating power.

[0022] In the invention, the induction heating coils are fixed and immovable under the hob plate.

[0023] In a method according to the invention for operating such a hob, a first step is provided for a hob control system to detect, via a pan detection sensor system in the hob mentioned above, whether a cooking vessel has been placed on the hob plate and, at least approximately, where it has been placed. Furthermore, the size of the cooking vessel can be detected under certain circumstances. A pan detection sensor system can, on the one hand, also use or draw on the induction heating coils. However, pan detection sensors are advantageously also used, for example in the form of small, flat coils arranged above the induction heating coils. This is known from EP 3 079 443 A1, to which explicit reference is made in this regard. Another pan detection sensor system can have different types of sensors, for example a camera outside the hob.

[0024] In a subsequent step, at least one induction heating coil is controlled to generate heating power for the cooking vessel. The induction heating coil used for this purpose is the one with the maximum coverage by the cooking vessel or the one closest to the cooking vessel, at least with respect to any point on its surface and the shortest possible distance to any point on the cooking vessel. A power level for the control can be entered by an operator in various ways on the hob.

[0025] Subsequently, at least one magnetic field steering element is moved between the at least one operated or activated induction heating coil and an area below the cooking vessel in order to introduce or direct the heat output or heat energy from the induction heating coil into the cooking vessel. Advantageously, at least two magnetic field steering elements are used for this purpose, although not all of them need to be moved. The at least one moving magnetic field steering element is then positioned in such a way that it ensures the best possible heating of the cooking vessel, possibly in conjunction with another stationary magnetic field steering element or another moving magnetic field steering element.

[0026] During operation of the hob, it is generally possible for at least movable magnetic field directing elements to actually be moved or to change their position. For example, the heat load on individual magnetic field directing elements can be better distributed if particularly heat-stressed magnetic field directing elements can be replaced with cooler ones through appropriate movement. On the one hand, replacement or movement is possible within a group of magnetic field directing elements that are responsible for heating a cooking vessel. Alternatively and advantageously, magnetic field directing elements that have not previously participated in the heating process and thus have a significantly lower temperature can be replaced. Such heating of the magnetic field directing elements can occur, on the one hand, through the forwarding or further transport of the heat energy.Furthermore, heating can occur by placing a cooking vessel that has already been heated to high temperatures and releasing heat downwards.

[0027] In an alternative embodiment, the magnetic field deflection element can be combined with a heat-insulating material or a heat-insulating molded part, which serves to prevent the flow of heat from the cooking vessel placed on the surface to the induction heating coil or the magnetic field deflection element. Such a heat-insulating material can, for example, be, or at least partially comprise, foam glass, pyrogenic silica, or vermiculite; see, for example, DE 10 2005 025 207 A1.

[0028] These and other features emerge not only from the claims but also from the description and the drawings. The individual features may be implemented individually or in combination in one embodiment of the invention and in other fields, and may represent advantageous and protectable embodiments for which protection is claimed here. The division of the application into individual sections and subheadings does not limit the generality of the statements made therein. Brief description of the drawings

[0029] Embodiments of the invention are illustrated schematically in the drawings and explained in more detail below. The drawings show: Fig. 1 a schematic plan view of a cooking hob according to the invention with four individual distributed induction heating coils, a number of magnetic field steering elements and three cooking vessels, Fig. 2 a schematic plan view of an alternative embodiment of a cooking hob according to the invention with eight induction heating coils that almost completely cover a heating area of ​​the cooking hob, a number of magnetic field steering elements and a cooking vessel, Fig. 3 a section through the hob according to the invention Fig. 1 and Fig. 4 a plan view of a possible design of a magnetic field steering element with flat ferrite rods. Detailed description of the implementation examples

[0030] In the Fig. Figure 1 shows a plan view of a hob 11 according to the invention in accordance with a first embodiment of the invention. The hob 11 has a hob plate 12, advantageously made of glass ceramic, as is typically used for such hobs or induction hobs. The hob 11 is divided by a horizontal dashed line into a rear heating area 14 and a front operating area 16, in which a schematically illustrated operating device 17 is arranged. This can be constructed, for example, with touch switches and needs no further explanation here. In addition to operating elements, it can also have display elements, possibly also a display or a graphics-capable display, for example as a touchscreen.

[0031] In the heating area 14, four induction heating coils 20a to 20d are arranged in a distributed arrangement as a type of square or rectangle. The heating area 14 is divided into a left half and a right half by a vertical dotted line. The two halves can advantageously form the aforementioned sub-areas. The two induction heating coils 20a and 20c in the left half are the same size and are arranged centrally one behind the other in the left half. In the right half, an elongated induction heating coil 20b is arranged at the rear, for example, to optimally heat elongated roasting pans or the like. The second induction heating coil 20d at the front in the right half is very large for particularly large cooking vessels, especially large pans.

[0032] The control and power adjustment of the induction heating coils 20a to 20d is not explained in detail here and can be carried out in a variety of ways using the operating device 17 in a manner known per se.

[0033] Shown in dashed lines are Fig. 1 several magnetic field steering elements 22 as described above, namely a total of 14. In the exemplary embodiment shown here, all magnetic field steering elements 22 are movable. In this case, it can be provided that only some of them, or possibly all of them, are movable only in the left half or only in the right half of the heating area 14. In this way, their mobility can possibly be designed in a simpler structural manner. However, under certain circumstances, they can also be completely movable. Since the induction heating coils 20a to 20d are clearly distributed here, spaced apart from one another and fixed or immovable, the invention provides that all magnetic field steering elements 22 are movable. As will be explained below in connection with the Fig. As explained in more detail in Figure 3, the magnetic field steering elements 22 are movable in an intermediate plane extending between the induction heating coils 20 and the underside of the cooktop plate 12. The precise mechanism for their movement is not shown here, but can be implemented easily and in a variety of ways by a person skilled in the art, for example, in accordance with DE 10 2015 203 316 A1, to which express reference is made in this regard. Other movement mechanisms can also be implemented structurally.

[0034] Since the magnetic field steering elements 22 are passive and do not require any independent power supply or control via electrical signals, their mobility is relatively easy to implement. They can be designed without any connections. They can also be moved by some kind of actuator or gripper and then placed, in which case they are fixed in position. Thus, a separate actuator or movement mechanism does not need to be provided for each magnetic field steering element.

[0035] From the presentation of the Fig. 1 shows that a cooking vessel 25a is placed on the hob plate 12, slightly offset to the left and upwards from the induction heating coil 20a. Normally, heating by means of the induction heating coil 20a in this position would not be possible, or only possible with limitations. In particular, heating of the bottom of the cooking vessel 25a could be uneven, which is undesirable. For this purpose, a control system (not shown here) of the hob 11, using pot detection sensors (also not shown), for which the induction heating coil 20a can also be used, determined the approximate position and size of this cooking vessel 25a. It then brought or moved four magnetic field steering elements 22 to the position shown, which then completely cover or cover the surface of the cooking vessel 25a.The heat generated inductively by the induction heating coil 20a is then transported or forwarded by the magnetic field steering elements 22 to the cooking vessel 25a, in particular, coupled into a base of the cooking vessel 25a, as is common with induction heating coils. Due to the illustrated placement of the four magnetic field steering elements 22, possibly slightly dependent on their precise design and function, the alternating magnetic field generated by the induction heating coil 20a is coupled into the base of the cooking vessel 25a with better directivity and efficiency, thus heating it.

[0036] Another cooking vessel 25b is placed to the right of the induction heating coil 20c, in such a way that it just does not cover it. Due to the size of the induction heating coil 20c and the size of the cooking vessel 25b, four magnetic field steering elements 22 have been positioned so that they are arranged almost exactly between or between the respective centers. Thus, as previously explained, the alternating magnetic field of the induction heating coil 20c can also be coupled into the cooking vessel 25b or its base, even though the cooking vessel 25b is not placed over the induction heating coil 20c or even overlaps it.

[0037] Another small cooking vessel 25c is placed in the right half of the heating area 14, exactly centrally above the induction heating coil 20d. Due to its relatively small size, a control system of the cooking surface 11 has decided that heating directly and solely with the induction heating coil 20d is not optimal, as its significantly larger diameter could potentially generate disruptive magnetic fields and stray fields. Therefore, a magnetic field steering element 22 has been moved directly beneath the cooking vessel 25c, which concentrates the entire alternating magnetic field of the induction heating coil 20d into the base of the cooking vessel 25c. Two or even more magnetic field steering elements 22 would clearly be disadvantageous here due to the small size of the cooking vessel 25c.

[0038] In the Fig. 1 right, using the example of the induction heating coil 20d with the cooking vessel 25c, shows that the magnetic field steering element 22 arranged centrally beneath the cooking vessel 25c can be moved, alternating with two magnetic field steering elements 22 arranged to the right of it, so to speak, so that they rotate clockwise. This makes it possible, if the magnetic field steering element 22 has become warm due to the forwarding or transporting of the heat output or has been heated by the reflected heat of the heated cooking vessel 25c, to replace it with another, even cooler one. This prevents excessive heating or possible damage to the magnetic field steering element 22. Likewise, excessive heating of the induction heating coil 20d arranged underneath can also be prevented. Finally, the temperature of the cooking plate 12 in this area can also be slightly reduced.The magnetic field steering elements 22 can be switched between each other either as soon as a temperature measurement (not shown here) indicates that a certain limit temperature has been reached. Alternatively, a controller can detect heating in the magnetic field steering element 22 due to the power level generated by the induction heating coil 20d and initiate a switchover after a certain time, for example, once per minute.

[0039] In the Fig. Figure 2 shows a slightly different hob 111 as a second embodiment of the invention. It also has a hob plate 112, which is divided by a horizontal line into a rear heating area 114 and a front operating area 116. A control device 117 is arranged at the front of the operating area 116, as previously described. Fig. 1 explained.

[0040] In the heating area 114, which is divided into a left half and a right half as sub-areas by a vertical dotted line, identical induction heating coils 120 are arranged on the left and right. They are rectangular in shape and placed so close to each other that they essentially cover the entire area of ​​the heating area 14 with only small gaps or spaces between them.

[0041] In the Fig. 2, a single cooking vessel 125 is shown, which is essentially arranged mainly above the right rear induction heating coil 120 of the left half of the heating area 114, but also covers the other three at least to a small extent. A special feature of this cooking surface 111 is that, in the left half of the heating area 114, three magnetic field steering elements 122 are arranged in a stationary manner along the vertical intermediate area between the two left induction heating coils and the two right induction heating coils. Due to the determined position and size of the cooking vessel 125, two magnetic field steering elements 122 are moved from the right, as indicated by the arrows. They are moved so close to the two stationary magnetic field steering elements 122 that a square arrangement is created, as in the Fig. 1 left rear. This then approximately covers the area of ​​the cooking vessel 125. For heating, either only the right rear induction heating coil 120 can be used, or the left rear one can be added. This depends on the required or desired power level for heating the cooking vessel 125, as well as the ability of the magnetic field steering elements 122 to transmit the alternating magnetic field of an induction heating coil 120 in a lateral direction, so to speak.

[0042] In the right half of the heating area 114 of the cooktop 111, magnetic field steering elements 122 are arranged centrally above each of the induction heating coils 120. If a cooking vessel is placed at least partially above one of these induction heating coils 120, another freely movable magnetic field steering element 122 or several of them can be moved closer. Thus, another position for stationary magnetic field steering elements 122 is shown here. Other possible positions could be along a horizontal gap between the front and rear induction heating coils 120. Likewise, further movable magnetic field steering elements 122, not shown here, could be provided in the right half of the heating area 114.

[0043] In the sectional view of the Fig. 3 is a section through the cooking surface 11 according to the invention from Fig. 1 in a very simplified form. The hob 11 has a housing 18 beneath the hob plate 12, which can be, for example, a type of plastic tub. The induction heating coils 20 and a control device (not shown) are inserted into this housing 18. An intermediate plate 19, also made of plastic, for example, runs above the induction heating coils 20. It can also be a textile fabric made of various materials, but the materials should above all be temperature-resistant. On this intermediate plate 19 or in an intermediate plane running parallel to and above the intermediate plate 19, several magnetic field steering elements 22 are shown. A movement mechanism for this is not shown here either, but is easily imagined based on the explanations given at the beginning.It can be seen that the magnetic field steering elements 22 are arranged just above the induction heating coils 20 and are at least partially movable in this intermediate plane. Furthermore, they are positioned just below the underside of the cooktop plate 12 and thus relatively close to a cooking vessel 25 placed on top of the cooktop plate 12. This allows for very effective transmission or transport of the heat output or heat energy.

[0044] In the Fig.Figure 4 shows an exemplary top view of a possible embodiment of a magnetic field steering element 22, which comprises six ferrite rods 23 arranged in a star shape. These are flat and advantageously identical in design. They can leave a small area free in their central region. Compared to conventional ferrite rods arranged above an induction heating coil, the ferrite rods 23 are somewhat longer and are drawn further toward the center. This allows for a better concentration effect and thus the transfer or transport of the heat output from an induction heating coil below to a cooking vessel above.

Claims

[1] Hob (11, 111) with a hob plate (12, 112) and a plurality of induction heating coils (20, 120) arranged underneath for heating a cooking vessel (25, 125) placed on the hob plate (12, 112), characterized by , that - the induction heating coils (20, 120) are not movable and are stationary during operation of the hob (11, 111), - magnetic field steering elements (22, 122) are arranged above the induction heating coils (20, 120) and below the hob plate (12, 112), - the magnetic field steering elements (22, 122) are designed to be movable during operation of the hob (11, 111), - the magnetic field steering elements (22, 122) are designed to transmit or transport heating power or heating energy from at least one induction heating coil (20, 120) to the cooking vessel (25, 125). [2] Hob according to claim 1, characterized bythat at least one magnetic field steering element (22, 122) has a Halbach array. [3] Hob according to claim 1 or 2, characterized by that at least one magnetic field steering element (22, 122) consists of ferritic material or has ferritic material, in particular in a flat, elongated rod shape (23). [4] Hob according to one of the preceding claims, characterized by that at least one magnetic field steering element (22, 122) has a material for magnetic field shielding. [5] Hob according to one of the preceding claims, characterized by that at least two magnetic field steering elements are provided per induction heating coil (20, 120), wherein in particular the induction heating coils (20, 120) and / or the magnetic field steering elements (22, 122) are of similar design, preferably identical. [6] Hob according to one of the preceding claims, characterized bythat at least one magnetic field steering element (22, 122) is freely movable within a partial area of ​​the cooking surface (11, 111), wherein a partial area is preferably part of a heating area (14, 114) of the cooking surface (11, 111), in particular a maximum of one quarter of the area of ​​the heating area (14, 114). [7] Hob according to one of the preceding claims, characterized by that at least one magnetic field steering element (22, 122) is stationary or immovable within a partial area of ​​the cooking surface (11, 111), in particular exactly a single magnetic field steering element (22, 122) per partial area, wherein preferably a partial area is part of a heating area (14, 114) of the cooking surface (11, 111), in particular a maximum of one quarter of the area of ​​the heating area (14, 114). [8] Method for operating a cooking hob (11, 111) according to one of the preceding claims, characterized byin that a control of the cooking surface (11, 111) detects via a pot detection sensor system whether a cooking vessel (25, 125) has been placed on the cooking surface (12, 112), where it has been placed and how large it is, wherein subsequently at least one induction heating coil (20, 120) is controlled with maximum coverage by the cooking vessel (25, 125) in order to generate heating power for the cooking vessel (25, 125), wherein subsequently at least one magnetic field steering element (22, 122) is moved between the at least one operated and stationary induction heating coil (20, 120) and an area beneath the cooking vessel (25, 125) in order to transmit or transport heating power or heating energy from the at least one induction heating coil (20, 120) into the cooking vessel (25, 125).

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