Classifications

• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F24—HEATING; RANGES; VENTILATING
  • F24C—DOMESTIC STOVES OR RANGES ; DETAILS OF DOMESTIC STOVES OR RANGES, OF GENERAL APPLICATION
  • F24C7/00—Stoves or ranges heated by electric energy
  • F24C7/08—Arrangement or mounting of control or safety devices
  • F24C7/082—Arrangement or mounting of control or safety devices on ranges, e.g. control panels, illumination
  • F24C7/083—Arrangement or mounting of control or safety devices on ranges, e.g. control panels, illumination on tops, hot plates
• • 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
  • H05B6/02—Induction heating
  • H05B6/06—Control, e.g. of temperature, of power
  • H05B6/062—Control, e.g. of temperature, of power for cooking plates or the like
• • 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
  • H05B2213/00—Aspects relating both to resistive heating and to induction heating, covered by H05B3/00 and H05B6/00
  • H05B2213/05—Heating plates with pan detection means

Definitions

• the present invention refers to a device for detecting cooking vessel characteristics at a cooking hob, in particular at an induction cooking hob, comprising a carrier plate for supporting a heating element, an upper cover plate disposed above said heating element, a temperature sensor, and at least one capacitive sensing layer disposed between said heating element and said upper cover plate.
• capacitive sensor techniques which detect when a cooking vessel is not centred over the cooking zone and, for example, turn off the power of the heating element to prevent uneven heating of the cooking vessel and damage to the cooking vessel. All those mentioned techniques are mainly limited to their specific detection and just differentiate a few states, for example centred or not centred, big or small, and similar, and not offering a more accurate information for a further usage as it is needed for example for the improvement of the cooking hob’s driving system.
• the main drawback of the aforementioned techniques is, that they do not allow for a measurement of all the characteristics which this invention allows for, as named by features of claim 1 and the respective sub-claims.
• the invention solves the problem of requiring high numbers of electrodes and connections. Further the described invention allows an implementation in cooking hobs, particularly in induction cooking hobs, without heating up significantly or significantly reducing the efficiency of any embodiment of the cooking hob system.
• a device for detecting cooking vessel characteristics comprises at least one evaluation unit, which can forward its data to other components of the induction cooking hob, preferably to the induction cooking hob’s driving unit.
• the evaluation unit may also be able to receive data from the driving unit or any other component of the induction cooking hob.
• the evaluation unit is the central system for measuring and evaluating multiple variables inside of the induction cooking hob system, also those which are not explicitly mentioned in the further description.
• only one microcontroller is used in the induction cooking hob for multiple tasks, as for example driving, measuring, and evaluating data, to reduce complexity and cost.
• the invention comprises a capacitive sensing layer containing at least three, preferably more sensing electrodes, positioned between the cover plate and the inductive heating element.
• Said plurality of sensing electrodes can be disposed on a single substrate, or each of the sensing electrodes can be disposed on a separate substrate.
• This substrate can be a separate substrate or any substrate already existing inside induction cooking hobs, as for example the cover plate or the mica sheet of the induction heating element, on which the electrodes can be applied with known technologies, as for example printing, vaporizing, or gluing.
• the sensing electrodes are arranged symmetrically in a way, that the sensing area, respectively formed by the outer edges of the sensing electrodes, is centred over the cooking zone, respectively formed by the outer edges of the induction heating elements.
• Each sensing electrode is separately connected to the evaluation unit by means of suitable wiring.
• the size of the sensing area is equal to the size of the cooking zone, especially preferred larger than the cooking zone size.
• multiple induction heating elements may be placed close to each other to allow a combined operation to form an extended cooking zone.
• two or more capacitive sensing layers may be combined in a way, that one or more sensing electrodes are part of multiple capacitive sensing layers.
• the plurality of sensing electrodes, not related to which capacitive sensing layer each belongs can be disposed on a single substrate, or multiple substrates, or each electrode can be disposed on a separate substrate.
• said evaluation unit can select which sensing electrodes are to be used and to be combined, while measuring the capacitance according to the further description.
• the evaluation unit can measure the capacitance between the different sensing electrodes separately and/or multiple electrically combined sensing electrodes. In one embodiment it uses a system such as a multiplexer or any similar device according to the know techniques to connect or disconnect different sensing electrodes, between which the capacitance is measured. This allows the evaluation unit to measure capacitance and changes in the electrical field between the different sensing electrodes and uses these data to estimate different characteristics of a placed cooking vessel over the sensing electrodes. The evaluation unit is also able to electrically or mechanically disconnect the sensing electrodes.
• the measurements done by the evaluation unit with different sensing electrodes can be made in different time events.
• the capacitance can be measured just once in a cooking process, advantageous at the beginning. It may also measure multiple times in a fixed period, and/or by request of any event interrupts of components of the induction cooking hob, and/or by changes caused by the user interaction.
• the power of the induction heating element is shortly reduced, more preferably stopped, while the evaluation unit switches between the sensing electrodes and measures the different capacitances. After the measurement the heating process is continued.
• each used sensing electrode is connected in one or more points.
• One method for said measurement of the capacitance is to apply a voltage step on the sensing electrode pair and measuring the speed of the voltage rise to determine the measured capacitance.
• Another method uses at least two connections per sensing electrode by applying a predetermined voltage frequency. By measuring the amplitude or form of current, voltage or both, the capacitance can be determined.
• the temperature measured by a temperature sensor may be used by the evaluation unit to compensate the influence of the changing cover plate temperature which might result in changes of the sensing electrode’s capacitance.
• the capacitive sensing layer has one or more holes at each position where the one or more temperature sensors are positioned, not to block them from directly touching the cover plate and therefore not to reduce their sensing response.
• the sensing electrodes are preferred to be constructed of thin conductive or partially conductive material, preferably with a maximum thickness of 1 mm, especially preferably 50 pm or lower, and made of material with low magnetic permeability. This reduces power losses created by the eddy currents flowing in the sensing electrodes and allows for the changing magnetic field to pass easier through the sensing electrodes to the cooking vessel.
• the sensing electrode is preferably constructed as a thin wire. Therefore, the resistance of the sensing electrode’s material, where the eddy currents are induced, increases. In the preferred embodiment constructed as described above, the induced eddy currents are reduced so the power loss becomes insignificant. This solves the technical problem of using conductive electrodes in a presence of a changing magnetic field while allowing the magnetic field to pass through it with reduced losses.
• the sensing electrode For the capacitance measurement of the evaluation unit it is advantageous to design the sensing electrode in the way, that the enclosing area is mainly filled by the wires. This means, that the area which is covered by electrically conductive wire is preferably larger then the free space in between, related to the enclosing area of the sensing electrode formed by the electrically conductive wire.
• the large filling ratio is advantageous to achieve a measurable capacitance value for a proper evaluation.
• the covered area could have a lower filling ratio, accordingly the accuracy of measurements will be low.
• the present invention improves the induction cooking hob driving unit’s estimation of the required power for the used cooking vessel to reach a specific temperature.
• the invention also determines characteristics of the cooking vessel to improve automatic cooking programs and similar functions.
• the driving unit can benefit from more information about the physical properties of the used cooking vessel for the regulation.
• One such property is the size of the cooking vessel. For example, too much delivered power to a small cooking vessel can burn the food quickly or damage the cooking vessel. If the cooking vessel is of big size the heat up time might be longer, so higher power is preferred to reach the desired cooking vessel temperature. Measuring the cooking vessel bottom size therefore helps to improve the temperature regulation performed by the driving unit. Another benefit of determining the cooking vessel size is the improved possibility to estimate the food quantity inside the cooking vessel.
• the evaluation unit can determine the area which is covered by the cooking vessel bottom. While the cooking vessel is positioned inside the sensing area, the determined area is proportionally equal to the size of said cooking vessels’ bottom surface.
• the evaluation unit uses a technique of combining sensing electrodes in a preferred way according to this invention. Using at least three sensing electrodes placed circularly, the evaluation unit is able to measure capacitance between the sensing electrodes in different combinations. In addition, the evaluation unit is able to combine one or more sensing electrodes into a one or more combined sensing electrode a more preferred embodiment the capacitive sensing layer comprises an even number of sensing electrodes. Hereby the evaluation unit preferably combines the sensing electrodes in an alternating combination. In this manner, the cooking vessel bottom size can be determined even when the cooking vessel is not precisely centred over the sensing area.
• the capacitive value increases on one side of the sensing area, while it mostly equally decreases on the other side of the sensing area.
• the average value of the evaluated capacitances mostly remains the same.
• the cooking vessel must be completely inside the sensing area, if not, the part of the cooking vessel outside of the sensing area is not detected.
• Detecting the cooking vessels position over the induction heating element is beneficial as the heat generated in a not centrically placed cooking vessel is not symmetrical and leads to higher temperature on one side and lower temperature at the other side of the cooking vessel. This can result in poor cooking experience. If a not centred cooking vessel is detected, a possible system reaction can be a notification on the user interface and/or an audible signal, so the user can adjust the position. This is especially useful as some cooking zone marking appeal to a more artistic appearance instead of practical, so the user might place the cooking vessel unknowingly in a not centred position.
• detecting the position of the cooking vessel is beneficial when using multiple induction heating elements for one extended cooking zone to determine, how much of the cooking vessel is placed over each induction heating element. This can help to achieve a more even heat distribution on the cooking vessel, if the cooking vessel is not placed symmetrically over each induction heating element. This is because if the cooking vessel covers one induction heating element more than the other, the system should reduce the power in the induction heating element which is less covered by said cooking vessel to maintain even heating.
• Another characteristic, which can be determined by the evaluation unit, is movement of the cooking vessel, the movement direction and a quantity of how much the cooking vessel was moved.
• Certain measurement techniques which may be implemented in the induction cooking hob but not further described, can measure electrical characteristics with similar responses from various physical changes, like movement of the cooking vessel caused by the user, and a temperature change caused for example by pouring hot or cold water into the cooking vessel. Those electrical characteristics are used to determine, if the temperature of the cooking vessel bottom is constant, increasing or decreasing.
• the presented solution according to this invention can detect a movement, movement direction and amount of movement of the cooking vessel, and therefore prevent other induction cooking hob devices as described or mentioned above of a wrong interpretation.
• each with a sensor setup according to the presented invention can determine a movement from one sensing area to another sensing area by comparing the movement direction and the cooking vessel size to determine where or from which to which cooking zone a cooking vessel has been moved. This can be used for example to transfer power settings from one induction heating element to another, as it is implemented in known existing functions. Because the evaluation unit can compare the characteristics of the cooking vessel, the moved cooking vessel can be more accurately detected than in the mentioned existing solutions, mainly in the case if the user moves, adds or removes multiple cooking vessels in short time window.
• the temperature sensor in an induction cooking hob is usually placed under the cover plate inside the cooking zone.
• Some cooking vessels are concave and/or have an indent in the centre because of construction technology. In this case they don’t directly touch the cover plate and the heat transfer to the cover plate is different compared to for example a flat cooking vessel.
• the temperature sensor is located in the approximate centre where such indents more often occur, or the concavity is the strongest, the measured temperature of the temperature sensor may vary. This reduces the accuracy and functionality of the driving unit’s regulation based on this temperature value.
• the capacitive sensing layer described in this invention can be expanded by one or more additional sensing electrodes, preferably symmetrical around the temperature sensors position.
• those sensing electrodes are always covered by the cooking vessel in case a suitable cookware is used. Therefore, their capacitive value is not influenced by different cooking vessel sizes, but by the distance to the cooking vessel bottom. This distance is representative of the cooking vessel concavity and/or indent at the position of those additional sensing electrodes. By adding more additional sensing electrodes over the sensing area, a more detailed information about the cooking vessel bottom construction can be detected.
• the detection of the cooking vessel concavity improves the accuracy of cooking vessel bottom size detection too. Because a concave cooking vessel has an increased average distance between the sensing electrodes and the cooking vessel bottom, the capacitance value measured for the cooking vessel size will be smaller. By measuring the degree of cooking vessel concavity, it improves the accuracy of cooking vessel bottom size detection.
• capacitive sensors can be used for the detection of a cooking vessel presence. Integrating an embodiment according to this invention reduces the need for other systems for detecting the same.
• the evaluation unit has a calibration function of the sensing electrodes. This function may just be activated once, possibly after integrating an embodiment as described in this invention into an induction cooking hob, for example, at the end of the production process of the same or at the first run of the induction cooking hob after installation at the customers home.
• the calibration function may also be available on request, for example from one component of the induction cooking hob or on user request.
• the evaluation unit measures multiple capacitances of the sensing electrodes in different advantageous combinations while no cooking vessel or other objects are present, to eliminate the influences of other induction cooking hob components on the electrical field of the sensing electrodes.
• This offers the possibility to use one design of a capacitive sensing layer in any form as described in this invention in different induction cooking hobs and on different induction heating elements without requiring specific changes and adjustments.
• Fig. 1 shows an induction cooking hob in a schematic side view
• Fig. 2 shows a partial top view of the induction cooking hob of Fig. 1,
• Fig. 3 shows another embodiment of the induction cooking hob
• Fig. 4 shows yet another embodiment of the induction cooking hob
• Fig. 5 shows detail V of Fig. 4,
• Fig. 6 shows an embodiment of an additional sensing electrode
• Fig. 7 shows yet another embodiment of the induction cooking hob.
• An induction cooking hob 1 comprises an assembly board 7 on which the inductive heating element 3 is mounted with a temperature sensor 6 in its approximate centre. Above it a cover plate 2 is located, made of an insulating material such as glass, on which a cooking vessel 10 can be placed. Between the cover plate 2 and the inductive heating element 3 the capacitive sensing layer 4 is placed. It comprises of one or more connectors 8 to connect via a connection 9 to the evaluation unit 5. The connector(s) 8 should be placed at a free spot, possibly next to the induction heating element 3 or in the approximate centre of the induction heating element 3 where the temperature sensor 6 is positioned.
• Fig. 2 illustrates one possible setup of the capacitive sensing layer 4 from the top view. It comprises four separate electrodes 20a connected via electrical connections 11a to the evaluation unit 5a. Exemplary the dimension of the below placed inductive heating element 12a is displayed, showing that the electrodes together are larger than the inductive heating element. In this case the sensing area 13a is larger too.
• Fig. 3 illustrates another more preferred setup of the capacitive sensing layer 4 from a top view, as the electrodes are placed symmetrically circular. It comprises six separate electrodes 20b in a wired structure, connected via connections lib to the evaluation unit 5b.
• the electrodes themselves can be in shaped of rectangles, or triangles, rhombus or similar. Their dimensions relate to a sensing area 13b. Exemplary the dimension of the below placed inductive heating element 12b is displayed, showing that the electrodes together are larger than the inductive heating element. In this case the sensing area 13b is larger too.
• Fig. 4 illustrates another even more preferred setup of the capacitive sensing layer 4 from a top view, as the electrodes are placed symmetrically circular with a larger filling ratio compared to Fig. 3. It comprises eight separate electrodes 20c in a wired structure, connected via a connection 9c from one joint connector 8c to the evaluation unit 5c. Exemplary the dimension of the below placed inductive heating element 12c is displayed, showing that the electrodes together are larger than the inductive heating element. In this case the sensing area 13c is larger too. In its centre two additional electrodes 21c are placed, which are also connected via the connector 8c to the evaluation unit 5c. They are used to detect indents or a concavity of a cooking vessel 10, as it is schematically illustrated in Fig. 6. The sector view V is shown in Fig. 5.
• the sector view V of Fig. 4 is illustrated in Fig. 5. It exemplary displays the wired structure of the electrodes 20 and their approximate proportions.
• the electrodes 20 are formed by electrically conductive wires 15, 18 which are preferably larger than the gaps 16 in between to achieve a sufficient filling ratio.
• the connection wires 17 which connect the electrode to the connector 8c are preferably smaller than the electrode wires 15 to reduce their influence on the capacitive value. Each electrode is separated by a gap 19.
• FIG. 6 An example of the additional electrodes 21c is shown in Fig. 6, comprising sensing electrode part 30, displayed in a top view, in a wired structure and a connection 31. Those are used to detect inside the sensing area 32 different distances to the cooking vessel 10a, 10b, displayed in a side view, which may occur by an indent 33 or concave bottom structure.
• the Fig. 7 shows a setup, in which multiple induction heating elements are used, in this case three, displayed as a dashed line. Those may be used in a combined operation to extend the cooking zone.
• two capacitive sensing layers shown as full line and as dashed line triangles, are combined in a way, that the two electrodes in the middle, shown as dash-dotted triangles, are part of both capacitive sensing layers.
• the setup as displayed in this figure is exemplary but not limited to. Also, a similar with less or more electrodes and induction heating elements is possible to be realized in such a setup.

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• Engineering & Computer Science (AREA)
• Chemical & Material Sciences (AREA)
• Combustion & Propulsion (AREA)
• Mechanical Engineering (AREA)
• General Engineering & Computer Science (AREA)
• Physics & Mathematics (AREA)
• Electromagnetism (AREA)
• Induction Heating Cooking Devices (AREA)

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• 2019
  • 2019-01-23 WO PCT/IB2019/050548 patent/WO2020152499A1/en unknown
  • 2019-01-23 EP EP19708148.2A patent/EP3914862A1/de not_active Withdrawn

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