EP2506664B1 - Cooking device - Google Patents

Description

The invention is based on a cooking device device according to the preamble of claim 1.

The publication EP 1 951 003 A1 discloses an induction hob having at least two heating frequency units operated according to a particular method to at least substantially avoid intermodulation noise. According to this method, both heating-frequency units are operated at an identical and fixed first frequency in a first time interval. In a second time interval, a heating frequency unit is switched off, while the other heating frequency unit is operated at a fixed second frequency. The two frequencies as well as the relative lengths of the two time intervals are adjusted so that an average output power of each heating frequency unit corresponds to a target power selected by an operator.

Other such induction hobs are from the documents WO 2006/117182 A1 . US 2010/0237065 A1 . US 2006/0289489 A1 and WO 2005/043737 A2 known.

The object of the invention is, in particular, to provide a cooking appliance device of the generic type which enables an advantageously flexible and easily implementable setting of an average output power. The object is achieved by the features of claim 1 and the method claim 8, while advantageous embodiments and modifications of the invention can be taken from the dependent claims.

The invention is based on a cooking device device with at least one first and at least one second heating frequency unit and with at least one control unit which is provided to operate the first heating frequency unit continuously with a fixed first frequency and to operate the second heating frequency unit in at least a first time interval and switch off in at least a second time interval.

It is proposed that the control unit be provided to operate the second heating frequency unit in the first time interval with at least one frequency which differs from the first frequency by at least 15 kHz, preferably at least 16 kHz and particularly advantageously at least 17 kHz. It can be provided in particular to operate the second heating frequency unit in the first time interval with a changing frequency. Preferably, however, it is provided to operate the second heating frequency unit in the first time interval with a fixed frequency, which differs particularly advantageously by exactly 17 kHz from the first frequency. The first frequency preferably corresponds to a nominal frequency of the first heating frequency unit for a given nominal power. A "target frequency" is to be understood in particular a frequency which supplies the desired power as output power during operation of the heating frequency unit with this frequency. An "output power" of one of the at least two heating-frequency units should in particular be understood to mean a power which is supplied by the heating-frequency unit in at least one heating operating state. The cooking device device is preferably designed as a hob device and particularly advantageously as an induction hob device. A "first time interval" and a "second" time interval are to be understood as meaning, in particular, two temporally successive time intervals of a length greater than 0. The designations "first" and "second" time intervals are intended exclusively for distinguishing the time intervals and, in particular, no statement about a time interval The term "provided" should in particular be understood to mean specially programmed and / or designed and / or equipped.

A "heating frequency unit" should in particular be understood to mean an electrical unit which generates an oscillating electrical current, preferably with a frequency of at least 15 kHz, in particular of at least 17 kHz and advantageously of at least 20 kHz, for operation of at least one heating unit. A "heating unit" is to be understood in particular as meaning a unit which is intended to convert electrical energy into heat, at least to a large extent, and thus in particular to heat a food to be cooked. Especially The heating unit comprises a radiant heater, a resistance heater and / or preferably an induction heater, which is intended to convert electrical energy into heat indirectly via induced eddy currents. The heating frequency unit comprises in particular at least one inverter, which preferably comprises two switching units. A "switching unit" is to be understood in particular as meaning a unit which is intended to interrupt a conduction path comprising at least part of the switching unit. Preferably, the switching unit is a bidirectional unipolar switch which in particular allows a current flow through the switch along the conduction path in both directions and in particular short-circuits an electrical voltage in at least one polarity direction. Preferably, the inverter comprises at least two bipolar transistors with insulated gate electrode and particularly advantageously at least one damping capacitor. A "conduction path" is to be understood as meaning, in particular, an electrically conductive conductor piece between two points. The term "electrically conductive" is to be understood in particular with a specific electrical resistance of at most 10 ^-4 ΩM, in particular of at most 10 ^-5 Ωm, advantageously of at most 10 ^-6 Ωm and particularly advantageously of not more than 10 ^-7 Ωm at 20 ° C.

A "control unit" is to be understood in particular as meaning an electronic unit which is preferably at least partially integrated in a control and / or regulating unit of a cooking appliance, in particular an induction hob, and which preferably has an arithmetic unit and in particular in addition to the arithmetic unit a storage unit with a stored therein Control program includes. Preferably, the control unit is provided to control and / or regulate the heating frequency units by means of control signals and preferably electrical control signals. A "control signal" should be understood in particular to mean a signal which, in particular in at least one operating state, triggers a switching operation of a heating frequency unit, in particular also indirectly. An "electrical control signal" is intended in particular to mean a control signal having an electrical potential of at most 30 V, preferably of at most 20 V, particularly advantageously at most 10 V and in particular at least 0.5 V, based on a reference potential. Preferably, the control signal has a periodicity at least at times, in particular with a period of at most 1 ms, in particular of at most 0.1 ms and advantageously of at most 0.05 ms. Particularly advantageously, the control signal is at least substantially a rectangular signal, which in particular has two discrete values, preferably a switch-on value and a switch-off value. Preferably, each of the two values corresponds to a switching position of the heating frequency units and in particular their inverter. A "frequency" of a heating frequency unit is to be understood in particular as the frequency of the control signal controlling the heating frequency unit.

By the fact that a heating frequency unit is "operated" should be understood in particular that the frequency of the heating frequency unit is different from zero. By the fact that a heating frequency unit is operated "continuously" should be understood in particular that the heating frequency unit is operated continuously during a heating mode, wherein the non-zero frequency of the control signal can change. The fact that a heating frequency unit is operated with a "fixed" frequency should in particular be understood to mean that the heating frequency unit is operated with a frequency that is at least substantially constant during a heating mode. An "at least largely immutable frequency" should be understood in particular to mean a frequency which during the heating mode has a fluctuation of at most 10%, in particular of at most 5%, preferably of at most 1% and particularly advantageously of 0%. The fact that a heating frequency unit is "switched off" in a time interval should in particular be understood to mean that the heating frequency unit has at least substantially a negligibly low output power in the relevant time interval. A "output power that is at least substantially insignificant in the relevant time interval" should be understood as meaning, in particular, an output power which is at most 100 W, in particular at most 50 W, preferably at most 25 W and particularly advantageously 0 W and / or which is delivered in the time interval exclusively during a period which corresponds to at most 50%, in particular at most 25%, preferably at most 15% and particularly advantageously at most 10% of a length of the time interval. The control unit is provided to control and / or regulate the at least two heating frequency units by means of the control signals in such a way that an average output power of one of the at least two heating frequency units corresponds at least largely to a nominal power selected by an operator. In this case, a relative deviation of the set by the control unit average output power of the target power should be at most 20%, preferably at most 10% and more preferably at most 5%. A "mean output power" is to be understood in particular a time-averaged output power. In a simultaneous operation of the at least two Heizfrequenzeinheiten the control unit is in particular provided to make an adjustment of the average output power to the desired power while largely avoiding Intermodulationsgeräuschen. A "substantial avoidance of intermodulation noise" should be understood in particular that intermodulation noises with a frequency of less than 17 kHz, in particular less than 16 kHz and preferably less than 15 kHz at a distance of 1 m from the cooking appliance device a sound pressure level of at most 20 dB, in particular of at most 10 dB, preferably of at most 5 dB, and particularly advantageously have a maximum of 0 dB. Preferably, the intermodulation sounds are inaudible by an average hearing operator.

By means of such a configuration, an advantageously flexible adjustment of the average output powers of the heating frequency units can be achieved, in particular since the frequency of the second heating frequency unit can be chosen to be greater or smaller than the first frequency. Furthermore, an easy implementation of the control method can be achieved, in particular by means of software. Furthermore, in particular even with greatly different desired powers for the at least two heating frequency units, an operation of both Heizfrequenzeinheiten be achieved with the required target performance under at least largely avoiding Intermodulationsgeräuschen. Furthermore, a simple scalability of the at least two heating frequency units can be made possible on any number of heating frequency units. Preferably, in at least one operating state, the control unit is provided for periodically operating the at least two heating frequency units with a period that corresponds to a sum of a length of the first time interval and a length of the second time interval. As a result, an advantageously simple control of the average output power can be achieved.

Advantageously, the control unit for the case that a frequency difference between a minimum of a desired power associated target frequency and a second smallest of a desired power associated target frequency is at least 17 kHz, provided to operate the Heizfrequenzeinheit with the smallest nominal frequency continuously with the fixed first frequency. It is then preferably provided to operate at least one further heating frequency unit in the first time interval with a frequency which is at least 15 kHz, in particular at least 16 kHz, preferably at least 17 kHz and particularly advantageously at a frequency which is exactly 17 kHz higher. In this way, a high level of operating comfort can be achieved since a difference between an output power of one of the at least two heating frequency units and a setpoint power can be minimized.

It is also proposed that the control unit in the event that a frequency difference between a minimum nominal power associated target frequency and a second smallest target power associated target frequency is less than 17 kHz, is provided to the heating frequency unit with the second smallest nominal frequency continuously at the fixed first frequency to operate. Preferably, it is then provided to operate at least one further heating frequency unit in the first time interval with a frequency which is at least 17 kHz and preferably at a frequency which is exactly 17 kHz smaller. As a result, an operation of the at least two heating frequency units each with one of the respective desired power corresponding average output power are made possible even in the case of a small frequency spacing.

In a further embodiment of the invention, it is proposed that the control unit is provided to control and / or regulate the at least two heating frequency units in each case by means of a control signal and to adapt a duty cycle of at least one of the control signals in at least one operating state. In particular, a ratio of a time duration in which the control signal assumes the switch-on value within a period duration to the period duration of the control signal is to be understood as a "duty cycle". Preferably, at a fixed frequency of one of the heating frequency units by changing the duty cycle, an output of the heating frequency unit can be changed. By the fact that the control unit is intended to "adjust a duty cycle of at least one of the control signals", it should be understood, in particular, that the control unit is intended to change the duty cycle of at least one of the control signals, thereby changing a fixed output power Frequency of a heating frequency unit. As a result, a flexibility in the setting of the average output powers of the at least two heating frequency units can be further advantageously increased.

Advantageously, the control unit is provided to adjust the duty cycle to minimize a patch characteristic. A "flicker characteristic" is to be understood in particular as a parameter that represents a measure of flicker. By "flicker" is meant, in particular, a subjective impression of an instability of a visual perception, which is caused in particular by a light stimulus whose luminance and / or spectral distribution varies with time. In particular, flicker can be caused by a voltage drop of a mains voltage. In particular, the patch characteristic is an overall output power difference, preferably between two time points of two time intervals and particularly advantageously two adjacent time intervals. Under a "total output" is in particular a Sum of the output powers of all heating-frequency units at a given time. A "total output power difference" is to be understood in particular as a difference of the total output powers at two different points in time. Preferably, the control unit is provided to lower the flicker characteristic below a threshold. The limit value is preferably a value defined by at least one statutory requirement and / or standard, in particular the standard DIN EN 61000-3-3. As a result, ease of use can be increased particularly advantageous and legal requirements and / or standards can be met.

In a further embodiment of the invention it is proposed that the cooking device device comprises at least a third heating frequency unit and that the control unit is provided in at least one operating state to at least temporarily switch off the third heating frequency unit. As a result, the control method according to the invention for a cooking device device with more than two heating frequency units and in particular to a cooking appliance device for a matrix hob can be scaled. A "matrix cooktop" is to be understood, in particular, as a cooktop in which heating units are arranged in a regular grid under a cooktop panel, and a region of the cooktop panel which can be heated by means of the heating units is preferably at least 60%, in particular at least 70%, advantageously at least 80%. and particularly advantageously comprises at least 90% of a total area of the hob plate. In particular, the matrix cooktop comprises at least 10, in particular at least 20, advantageously at least 30 and particularly advantageously at least 40 heating units.

Advantageously, the control unit is provided for operating the third heating frequency unit at least partially simultaneously with the second heating frequency unit and at the same frequency as the second heating frequency unit. As a result, intermodulation noises can be at least largely avoided, in particular with any number of simultaneously operated heating frequency units.

Furthermore, a method is proposed with a cooking device device with at least one first and at least one second heating frequency unit, in which the first heating frequency unit is operated continuously at a fixed first frequency and the second heating frequency unit is operated in at least a first time interval and switched off in at least a second time interval, wherein the second heating frequency unit is operated in the first time interval with at least one frequency which differs from the first frequency at least by 15 kHz, preferably by at least 16 kHz and particularly advantageously by at least 17 kHz. In this way, an advantageously flexible adjustment of the average output power of the heating frequency units can be achieved. Furthermore, easy implementation of the control method can be achieved. Furthermore, in particular even with greatly differing setpoint powers for the at least two heating frequency units, an operation of both heating frequency units with the required setpoint power can be achieved with at least largely avoiding intermodulation noise.

Furthermore, a cooking appliance, in particular a hob, proposed with a Gargerätevorrichtung invention. Preferably, the hob is an induction hob.

Further advantages emerge from the following description of the drawing. In the drawing, two embodiments of the invention are shown. The drawing, the description and the claims contain numerous features in combination. The person skilled in the art will expediently also consider the features individually and combine them into meaningful further combinations.

Fig. 1

ein Induktionskochfeld mit einer Gargerätevorrichtung mit zwei Heizfrequenzeinheiten,

Fig. 2

ein beispielhaftes, nicht maßstabsgetreues Steuersignal einer der zwei Heizfrequenzeinheiten,

Fig. 3a

beispielhafte, nicht maßstabsgetreue Leistungs-Frequenz-Kurven für die zwei Heizfrequenzeinheiten bei einem Frequenzabstand von zumindest 17 kHz zwischen einer kleinsten und einer zweitkleinsten Sollfrequenz der Heizfrequenzeinheiten,

Fig. 3b

je eine beispielhafte, nicht maßstabsgetreue Leistungs-Zeit-Kurve für die zwei Heizfrequenzeinheiten für den Fall aus Fig. 3a,

Fig. 4a

beispielhafte, nicht maßstabsgetreue Leistungs-Frequenz-Kurven für die zwei Heizfrequenzeinheiten bei einem Frequenzabstand von weniger als 17 kHz zwischen einer kleinsten und einer zweitkleinsten Sollfrequenz der Heizfrequenzeinheiten,

Fig. 4b

je eine beispielhafte, nicht maßstabsgetreue Leistungs-Zeit-Kurve für die zwei Heizfrequenzeinheiten für den Fall aus Fig. 4a,

Fig. 5

beispielhafte, nicht maßstabsgetreue Leistungs-Frequenz-Kurven einer der zwei Heizfrequenzeinheiten bei unterschiedlichen Tastgraden eines Steuersignals,

Fig. 6

beispielhafte, nicht maßstabsgetreue Gesamtleistungs-Zeit-Kurven,

Fig. 7a

beispielhafte, nicht maßstabsgetreue Leistungs-Frequenz-Kurven für drei Heizfrequenzeinheiten einer weiteren Gargerätevorrichtung bei einem Frequenzabstand von mehr als 17 kHz zwischen einer kleinsten und einer zweitkleinsten Sollfrequenz der Heizfrequenzeinheiten,

Fig. 7b

je eine beispielhafte, nicht maßstabsgetreue Leistungs-Zeit-Kurve für die drei Heizfrequenzeinheiten für den Fall aus Fig. 7a,

Fig. 8a

beispielhafte, nicht maßstabsgetreue Leistungs-Frequenz-Kurven für drei Heizfrequenzeinheiten der Gargerätevorrichtung aus Fig. 7a bei einem Frequenzabstand von weniger als 17 kHz zwischen einer kleinsten und einer zweitkleinsten Sollfrequenz der Heizfrequenzeinheiten und

Fig. 8b

je eine beispielhafte, nicht maßstabsgetreue Leistungs-Zeit-Kurve für die drei Heizfrequenzeinheiten für den Fall aus Fig. 8a.

Show it:

Fig. 1

an induction hob with a cooking appliance device with two heating frequency units,

Fig. 2

an exemplary, not to scale, control signal of one of the two heating frequency units,

Fig. 3a

exemplary, not to scale true power frequency curves for the two heating frequency units at a frequency spacing of at least 17 kHz between a minimum and a second smallest nominal frequency of the heating frequency units,

Fig. 3b

an exemplary, not to scale true power-time curve for the two heating frequency units for the case off Fig. 3a .

Fig. 4a

exemplary, not to scale true power frequency curves for the two heating frequency units at a frequency spacing of less than 17 kHz between a minimum and a second smallest nominal frequency of the heating frequency units,

Fig. 4b

an exemplary, not to scale true power-time curve for the two heating frequency units for the case off Fig. 4a .

Fig. 5

exemplary, not to scale power frequency curves of one of the two heating frequency units at different duty cycles of a control signal,

Fig. 6

exemplary, not to scale total power-time curves,

Fig. 7a

exemplary, not to scale true power frequency curves for three heating frequency units of another cooking appliance device at a frequency spacing of more than 17 kHz between a minimum and a second smallest nominal frequency of the heating frequency units,

Fig. 7b

depending on an exemplary, not to scale true power-time curve for the three heating frequency units for the case Fig. 7a .

Fig. 8a

exemplary, not to scale true power frequency curves for three heating frequency units of Gargerätevorrichtung off Fig. 7a at a frequency spacing of less than 17 kHz between a minimum and a second smallest nominal frequency of the heating frequency units and

Fig. 8b

depending on an exemplary, not to scale true power-time curve for the three heating frequency units for the case Fig. 8a ,

FIG. 1 shows a trained as induction hob 16a cooking appliance. The induction hob 16a comprises a hob plate 18a, in particular of a glass ceramic, on which two heating zones 20a, 22a are marked in a known manner. The hob plate 18a is horizontally disposed in an operative state of the induction hob 16a and provided for setting up cooking utensils. Furthermore, touch-sensitive operating elements 26a and display elements 28a of an operating and display unit 30a of the induction hob 16a are marked in a known manner on the hob plate 18a. The induction hob 16a further comprises a cooking appliance device having a first and a second heating frequency unit 10a, 12a arranged below the hob plate 18a and with a control unit 14a arranged below the hob plate 18a. In FIG. 1 are components which are arranged below the hob plate 18a, drawn schematically and dashed, with functional relationships are indicated by arrows. The control unit 14a is integrated in a control and regulation unit 32a of the induction hob 16a. An induction heating unit associated with and located below the heating zone 20a is energized by the first heating frequency unit 10a. An induction heating unit associated with and located below the heating zone 22a is energized by the second heating frequency unit 12a. An operator can select a heating stage for each of the heating zones 20a, 22a by means of the operating and display unit 30a, which results in a desired output P _obj1 , P _obj2 for the two heating frequency units 10a, 12a. The control unit 14a is provided to _adapt a respective average output power P _ave1 , P _{ave2 of} the heating frequency units 10a, 12a to the desired powers P _obj1 , P _obj2 while largely avoiding intermodulation noise, so that the selected heating levels of the heating zones 20a, 22a can be achieved. The control unit 14a controls the first heating frequency unit 10a by means of a control signal V ₁ (t) and the second heating frequency unit 12a by means of a control signal V ₂ (t).

FIG. 2 shows by way of example a not to scale control signal V ₂ (t) of the second heating frequency unit 12a in a Cartesian coordinate system. An ordinate axis 36 has a control voltage V ₂ and an abscissa axis 38 applied a time t. The control signal V ₂ (t) is during a first time interval T _A a period T a square wave signal with a switch-V ₀ and a switch-off of 0 volts. The switch-on value V ₀ is held during a switch-on time t ₀ . The square wave signal has a period T _0th During a period of time (T ₀ -t ₀ ), the turn-off value is held. A frequency f _{2 of} the control signal V ₂ (t) is calculated from a reciprocal of the period T ₀ . The frequency f ₂ is usually between 20 kHz and 100 kHz. A duty cycle D _{2A of} the control signal V ₂ (t) is calculated from a quotient of the switch-on time t ₀ divided by the period T ₀ . While V ₂ (t) takes the form of the square wave signal, a first of two switching units of the second heating frequency unit 12 a is periodically switched in accordance with a periodic change of the turn-on value V ₀ and the turn-off value. A second switching unit of the second heating frequency unit 12a is periodically switched in an analogous but time-shifted manner, so that a high-frequency alternating current results in an operation of the induction heating unit assigned to the heating zone 22a. During a second sub-interval T _{B of} the period T with T _B = TT _A , the control signal V ₂ (t) is identical to zero. A time x separates the first time interval T _A and the second time interval T _B. After the period T has elapsed, the control signal V ₂ (t) is repeated.

FIG. 3a shows in a Cartesian coordinate system by way of example two not-to-scale power frequency curves P ₁ (f) and P ₂ (f). On an ordinate axis 42, output powers P ₁ and P _{2 of} the heating frequency units 10a, 12a are plotted. On an abscissa axis 44, the frequency f is plotted. The target powers P _obj1 and P _{obj2 of} the heating frequency units 10a, 12a are set by an operator. In the present case, a frequency spacing of the nominal powers P _obj1 and P _obj2 associated _setpoint frequencies f _obj1 and f _{obj2 of} the heating frequency units 10a, 12a is at least 17 kHz. Without limiting the generality, let it be assumed that the first heating frequency unit 10a has the smallest _nominal frequency f _obj1 assigned to the desired powers P _obj1 , P _obj2 . This is then operated by the control unit 14a continuously with a fixed first frequency f _1, that of the target power P _obj1 associated nominal frequency f _obj1 equivalent. The second heating frequency unit 12a is operated by the control unit 14a in the first time interval T _A with a frequency f ₂ which is 17 kHz higher. Since the output power P _{2 of} the second heating frequency unit 12a at the frequency f ₂ exceeds the target power P _{obj2 of} the second heating frequency unit 12a, the second heating frequency unit 12a is switched off in the second time interval T _B.

FIG. 3b shows in a Cartesian coordinate system by way of example two not-to-scale power-time curves P ₁ (t) and P ₂ (t) for the in FIG. 3a described case. On an ordinate axis 46, the output powers P ₁ and P ₂ of the Heizfrequenzeinheiten 10a, 12a applied. The time t is plotted on an abscissa axis 48. An in FIG. 3b illustrated course of the power-time curves P ₁ (t) and P ₂ (t) is in a heating operation state of the heating-frequency units 10 a, 12 a periodically through the period T. The control unit 14a calculates the lengths of the time intervals T _A and T _{B of} the period T so that the average output power P _{ave2 of} the second heating frequency unit 12a corresponds to the desired power P _obj2 . The following applies: $${\mathrm{<figure-callout\; id="2"\; label="P\; ave"\; filenames="imgf0001.png,imgf0003.png"\; state="\{\{state\}\}">P\; </figure-callout>}}_{\mathrm{ave}}=\left({\mathrm{T}}_{\mathrm{A}}/\mathrm{T}\right)\times {\mathrm{<figure-callout\; id="2"\; label="P"\; filenames="imgf0001.png,imgf0003.png"\; state="\{\{state\}\}">P</figure-callout>}}_{\mathrm{2}}\left(\mathrm{0}\le \mathrm{t}\le \mathrm{x}\right)={\mathrm{<figure-callout\; id="2"\; label="P\; obj"\; filenames="imgf0001.png,imgf0003.png"\; state="\{\{state\}\}">P\; </figure-callout>}}_{\mathrm{obj}}\mathrm{,}$$

FIG. 4a shows in a Cartesian coordinate system by way of example two not-to-scale power frequency curves P ₁ (f) and P ₂ (f). On an ordinate axis 50, output powers P ₁ and P _{2 of} the heating frequency units 10a, 12a are plotted. On an abscissa axis 52, the frequency f is plotted. The target powers P _obj1 and P _{obj2 of} the heating frequency units 10a, 12a are set by an operator. In the present case, a frequency spacing of the nominal powers P _obj1 and P _obj2 associated desired frequencies f _obj1 and f _{obj2 of} the heating frequency units 10a, 12a is less than 17 kHz. Without limiting the generality, let it be assumed that the first heating frequency unit 10a has the second smallest, that is to say the highest _nominal frequency f _obj1 assigned to the desired powers P _obj1 , P _{obj2 here} . This is then operated by the control unit 14a continuously with a fixed first frequency f ₁ , which _corresponds to the target power P _obj1 associated target frequency f _obj1 . The second heating frequency unit 12a is operated by the control unit 14a in the first time interval T _A with a frequency f ₂ lower by 17 kHz. Since the output power P _{2 of} the second heating frequency unit 12a at the frequency f ₂ exceeds the target power P _{obj2 of} the second heating frequency unit 12a, the second heating frequency unit 12a is switched off in the second time interval T _B.

FIG. 4b shows in a Cartesian coordinate system by way of example two not-to-scale power-time curves P ₁ (t) and P ₂ (t) for the in FIG. 4a described case. The output powers P ₁ and P _{2 of} the heating frequency units 10a, 12a are plotted on an ordinate axis 54. The time t is plotted on an abscissa axis 56. An in FIG. 4b illustrated course of the power-time curves P ₁ (t) and P ₂ (t) is in a heating operation state of the heating-frequency units 10 a, 12 a periodically through the period T. The calculation of the lengths of the time intervals T _A and T _{B of} the period T by the control unit 14 a is carried out as described above.

FIG. 5 shows in a Cartesian coordinate system by way of example not true-to-scale power frequency curves P ₂ (f, d _j ) for different duty cycles D _2A = d _j (j = 1, ..., n) of the control signal V ₂ (t) of the second heating frequency unit 12a (see also FIG. 2 ). On an ordinate axis 58, the output power P _{2 of} the second heating frequency unit 12 a is plotted. On an abscissa axis 60, the frequency f is plotted. By adapting the duty cycle D _2A , for example from 0.5 to smaller values, the control unit 14a can adjust the output power P _{2 of} the second heating frequency unit 12a. In this way, in particular a lowering of the output power P ₂ at a fixed frequency f _{2 of} the second heating frequency unit 12a can be achieved. This fact has a special significance in minimizing a patch characteristic F.

zwischen den Zeitintervallen T_A und T_B identische Flickerkenngröße F durch die Wahl eines kleineren Tastgrads D_2A verkleinert werden. Die Steuereinheit 14a nutzt diesen Sachverhalt zur Minimierung der Flickerkenngröße F. FIG. 6 shows in two Cartesian coordinate systems by way of example two non-to-scale total power-time curves. On an ordinate axis 62 in each case the sum of the output powers P ₁ + P _{2 of} the heating frequency units 10a, 12a applied. On an abscissa axis 64, the time t is plotted during three periods T in each case. The top of the two coordinate systems FIG. 6 FIG. 15 shows a case where the duty D _{2A of} the second heating frequency unit 12 a has a value d ₁ . According to FIG. 5 results in the frequency f ₂ then an output P _{2 of} the second heating frequency unit 12a of P ₂ (f ₂ , d ₁ ). The bottom of the two coordinate systems FIG. 6 FIG. 12 shows a case where the duty D _{2A of} the second heating frequency unit 12a has a value d _n which is smaller than d ₁ . According to FIG. 5 at the frequency f ₂ , an output power P _{2 of} the second heating frequency unit 12a of P ₂ (f ₂ , d _n ), which is smaller than the output power P ₂ (f ₂ , d ₁ ), then results. As based on FIG. 6 To recognize that can be with a total power difference $$\mathrm{F}={\mathrm{P}}_{\mathrm{1}}\left(\mathrm{0}\le \mathrm{t}\le \mathrm{x}\right)+{\mathrm{<figure-callout\; id="2"\; label="P"\; filenames="imgf0001.png,imgf0003.png"\; state="\{\{state\}\}">P</figure-callout>}}_{\mathrm{2}}\left(\mathrm{0}\le \mathrm{t}\le \mathrm{x}\right)-\left[{\mathrm{P}}_{\mathrm{1}}\left(\mathrm{x}\le \mathrm{t}\le \mathrm{T}\right)+{\mathrm{P}}_{\mathrm{2}}\left(\mathrm{x}\le \mathrm{t}\le \mathrm{T}\right)\right]$$

between the time intervals T _A and T _B identical flicker characteristic F be reduced by the choice of a smaller duty cycle D _2A . The control unit 14a uses this fact to minimize the patch characteristic F.

Adjusting the output power P ₂ of the second Heizfrequenzeinheit 12a addition, the effect can be achieved by adjusting a duty cycle D _1A of the control signal V ₁ (t) of the first Heizfrequenzeinheit 10a in the time interval T _A and / or by adjusting a duty cycle D _1B of the control signal V ₁ (T) of the first heating frequency unit 10a in the time interval T _B, an adjustment of the output power P _{1 are} made. In this way, further setting options can be developed, in particular if an adjustment of the average output power P _ave1 and / or P _ave2 to the desired power P _obj1 and / or P _obj2 due to a possible minimum frequency and / or a possible maximum frequency at a duty cycle D _1A , D _1B of 0.5 would be impossible.

Alternatively, an induction hob can also have more than two induction heating units, wherein in each case a plurality of induction heating units can each be connected to a heating frequency unit via a respective switching unit.

In the FIGS. 7a, b and 8a, b a further embodiment of the invention is shown. The following descriptions are essentially limited to the differences between the embodiments, with respect to the same components, features and functions on the description of the other embodiment and in particular FIG. 1 can be referenced. To distinguish the embodiments, the letter a in the reference numerals of the embodiment in the FIGS. 1 to 5 by the letter b in the reference numerals of the embodiment of FIGS. 7a , b and 8a, b replaced.

The method described above can be easily extended to a cooking appliance device for an induction hob 16b with at least a first heating frequency unit 10b, a second heating frequency unit 12b and a third heating frequency unit.

Figure 7a shows in a Cartesian coordinate system, for example, three power-frequency curves P ₁ (f), P ₂ (f) and P ₃ (f) which are not true to scale. Output powers P ₁ , P ₂ and P _{3 of} the heating frequency units 10b, 12b are plotted on an ordinate axis 66. On an abscissa axis 68, the frequency f is plotted. The target powers P _obj1 , P _obj2 and P _{obj3 of} the heating frequency units 10b, 12b are set by an operator. Without loss of generality, it is assumed the first Heizfrequenzeinheit 10b, a smallest the Solleistungen P _obj1, P _obj2, P _obj3 associated nominal frequency f _obj1, and the second Heizfrequenzeinheit 12b, a second smallest to Solleistungen P _obj1, P _obj2, P _obj3 associated nominal frequency f _obj2 on. A frequency spacing between the smallest _nominal frequency f _obj1 and the second smallest _nominal frequency f _obj2 is at least 17 kHz. The first heating frequency unit 10b is then operated by a control unit 14b of the cooking appliance device continuously with a fixed first frequency f ₁ , which corresponds to the setpoint power P _obj1 associated _setpoint frequency f _obj1 . The second heating frequency unit 12b is controlled by the control unit 14b in a first time interval T _A with a 17 kHz higher frequency f ₂ operated. Since the output power P _{2 of} the second heating frequency unit 12b exceeds the nominal power P _obj2 at the frequency f ₂ , the second heating frequency unit 12b is switched off in a second time interval T _B following the first time interval T _A. The third heating frequency unit is operated by the control unit 14b in a first time interval T _A 'as well with the frequency f ₂ . Since the output power P _{3 of} the third heating frequency unit at the frequency f ₂ exceeds the setpoint power P _obj3 , the third heating frequency unit is switched off in a second time interval T _B 'following the first time interval T _A '.

FIG. 7b shows in a Cartesian coordinate system by way of example three not-to-scale power-time curves P ₁ (t), P ₂ (t) and P ₃ (t). The output powers P ₁ , P ₂ and P _{3 of} the heating frequency units 10b, 12b are plotted on an ordinate axis 70. The time t is plotted on an abscissa axis 72. The calculation of the lengths of the time intervals T _A , T _B , T _A 'and T _B ' of the period T by the control unit 14 _b is carried out as described in the previous embodiment. Like in the FIG. 7b shown, overlap the time intervals T _A and T _A 'at least partially.

FIG. 8a shows in a Cartesian coordinate system by way of example three not-to-scale power frequency curves P ₁ (f), P ₂ (f) and P ₃ (f). On an ordinate axis 74 are output powers P _1, P ₂ and P ₃ of the Heizfrequenzeinheiten 10b, 12b applied. On an abscissa axis 76, the frequency f is plotted. The target powers P _obj1 , P _obj2 and P _{obj3 of} the heating frequency units 10b, 12b are set by an operator. Without restricting the generality, let it be assumed that the first heating frequency unit 10b has a second smallest nominal frequency f _obj1 assigned to the nominal powers P _obj1 , P _obj2 , P _obj3 , and the second heating frequency unit 12b has a smallest nominal frequency f _associated with the nominal powers P _obj1 , P _obj2 , P _{obj3 obj2} on. A frequency spacing between the smallest _nominal frequency f _obj1 and the second smallest _nominal frequency f _obj2 is less than 17 kHz. The heating frequency unit 10b with the second smallest _nominal frequency f _obj1 , in the present case, the first heating frequency unit 10b, is then operated by the control unit 14b continuously with a fixed first frequency f ₁ , which _corresponds to the target power P _obj1 associated target frequency f _obj1 . The second heating frequency unit 12b is operated by the control unit 14b in the first time interval T _A with a frequency f ₂ lower by 17 kHz. Since the output power P _{2 of} the second heating frequency unit 12b at the frequency f ₂ exceeds the setpoint power P _obj2 , the second heating frequency unit 12b is switched off in the second time interval T _B. The third heating frequency unit is also operated by the control unit 14b in the first time interval T _A 'at the frequency f ₂ . Since the output power P, the target power P _{obj3 3} exceeds the third Heizfrequenzeinheit at the frequency f _2, the third Heizfrequenzeinheit in the second time interval is switched off T _B '.

FIG. 8b shows in a Cartesian coordinate system by way of example three not-to-scale power-time curves P ₁ (t), P ₂ (t) and P ₃ (t). The output powers P ₁ , P ₂ and P _{3 of} the heating frequency units 10b, 12b are plotted on an ordinate axis 78. The time t is plotted on an abscissa axis 80. The calculation of the lengths of the time intervals T _A , T _B , T _A 'and T _B ' of the period T by the control unit 14 _b is carried out as previously described. Like in the FIG. 8b shown, overlap the time intervals T _A and T _A 'at least partially.

Again, analogous to the previous embodiment, an adaptation of duty D _1A , D _2A , D _3A and D _1B may be provided, in particular for minimizing a Flickerkenngröße F. The control method described with reference to the second embodiment is scalable from three heating frequency units to a plurality of Heizfrequenzeinheiten , For example, for a trained as a matrix cooktop induction hob.

In all of the described embodiments, further, if no suitable set of frequencies f ₁ , f ₂ , time intervals T _A , T _B , T _A ', T _B ', etc. and duty cycles D _1A , D _1B , D _2A , D _3A etc. can be found, in particular to comply with a maximum possible maximum frequency and / or a minimum possible minimum frequency are, the control method described above with other, known to a person skilled and seem reasonable sense control method combined. It is thus conceivable, for example, for time intervals T _A and T _{B to be followed by} a further time interval T _C during which all or even only part of the heating frequency units are switched off or operated at a further common frequency f ₃ . reference numeral 10 Heizfrequenzeinheit 70 axis of ordinates 12 Heizfrequenzeinheit 72 abscissa 14 control unit 74 axis of ordinates 16 Induction hob 76 abscissa 18 Hotplate 78 axis of ordinates 20 heating zone 80 abscissa 22 heating zone d _j Duty cycle (j = 1, ..., n) 26 operating element D _1A duty cycle 28 display element D _1B duty cycle 30 Operating and display unit D _2A duty cycle 32 Control unit D _3A duty cycle 36 axis of ordinates F Flickerkenngröße 38 abscissa f frequency 42 axis of ordinates f ₁ frequency 44 abscissa f ₂ frequency 46 axis of ordinates f ₃ frequency 48 abscissa f _obj1 nominal frequency 50 axis of ordinates f _obj2 nominal frequency 52 abscissa f _obj3 nominal frequency 54 axis of ordinates P ₁ output 56 abscissa P ₁ (f) Power-frequency curve 58 axis of ordinates P ₁ (t) Power-time curve 60 abscissa P ₂ output 62 axis of ordinates P ₂ (f) Power-frequency curve 64 abscissa P ₂ (f, _dj ) Power-frequency curve 66 axis of ordinates P ₂ (t) Power-time curve 68 abscissa P ₃ output P ₃ (f) Power-frequency curve P ₃ (t) Power-time curve P _ave1 Average output power P _ave2 Average output power P _obj1 target power P _obj2 target power P _obj3 target power T period T ₀ period T _A time interval T _A ' time interval T _B time interval T _B ' time interval T _C time interval t Time t ₀ on time V ₀ Switch-on V ₁ (t) control signal V ₂ control voltage V ₂ (t) control signal x time x ' time

Claims (9)

1. Cooking device apparatus having at least one first and at least one second heat frequency unit (10a, 12a; 10b, 12b) and having at least one control unit (14a; 14b), which is provided to continuously operate the first heat frequency unit (10a; 10b) and to operate the second heat frequency unit (12a, 12b) in at least one first time interval (T_A ) and to switch it off in at least one second time interval (T_B ), wherein the control unit (14a; 14b) is provided to operate the second heat frequency unit (12a; 12b) in the first time interval (T_A ) with at least one frequency (f ₂), which differs at least by 15 kHz from a first frequency (f ₁) of the first heat frequency unit (10a; 10b), characterised in that the control unit (14a; 14b) is provided to continuously operate the first heat frequency unit (10a; 10b) with the fixed first frequency (f ₁), wherein in the event that a frequency interval between a smallest target frequency (f _obj1, f _obj2) assigned to a target output (P _obj1, P _obj2) and a second smallest target frequency (f _obj1, f _obj2) assigned to a target output (P _obj1, P _obj2) is smaller than 17 kHz, the control unit (14a; 14b) is provided to continuously operate the heat frequency unit (10a, 12a; 10b, 12b) with the second smallest frequency (f _obj1, f _obj2) with the fixed first frequency (f ₁).
2. Cooking device apparatus according to claim 1, characterised in that in the event that a frequency interval between a smallest target frequency (f _obj1, f _obj2) assigned to a target output (P _obj1, P _obj2) and a second smallest target frequency (f _obj1, f _obj2) assigned to a target output (P _obj1, P _obj2) amounts to at least 17 kHz, the control unit (14a; 14b) is provided to continuously operate the heat frequency unit (10a, 12a; 10b, 12b) with the smallest target frequency (f _obj1, f _obj2) with the fixed first frequency (f ₁).
3. Cooking device apparatus according to one of the preceding claims, characterised in that the control unit (14a; 14b) is provided to control and/or regulate the at least two heat frequency units (10a, 12a; 10b, 12b) by means of a control signal (V ₁(t), V ₂(t)) in each case and to adjust a pulse duty factor (D _1A ,D _1B ,D _2A ,D _3A ) of at least one of the control signals (V ₁(t), V ₂(t)) in at least one operating state.
4. Cooking device apparatus according to claim 3, characterised in that the control unit (14a; 14b) is provided to adjust the pulse duty factors (D _1A ,D _1B ,D _2A ,D _3A ) in order to minimise a flicker parameter (F).
5. Cooking device apparatus according to one of the preceding claims, characterised by at least one third heat frequency unit.
6. Cooking device apparatus according to claim 5, characterised in that the control unit (14b) is provided in at least one operating state to at least temporarily switch off the third heat frequency unit.
7. Cooking device apparatus according to claim 5 or 6, characterised in that the control unit (14b) is provided to operate the third heat frequency unit at least partially at the same time as the second heat frequency unit (12b) and with the same frequency (f ₂) as the second heat frequency unit (12b).
8. Method with a cooking device apparatus having at least one first and at least one second heat frequency unit (10a, 12a; 10b, 12b), in particular according to one of the preceding claims, in which the first heat frequency unit (10a; 10b) is operated continuously and the second heat frequency unit (12a; 12b) is operated in at least one first time interval (T_A ) and is switched off in at least one second time interval (T_B ), wherein the second heat frequency unit (12a; 12b) is operated in the first time interval (T_A ) with at least one frequency (f ₂) which differs at least by 15 kHz from a first frequency (f ₁) of the first heat frequency unit (10a; 10b), characterised in that the first heat frequency unit (10a; 10b) is continuously operated with the fixed first frequency (f ₁), wherein in the event that a frequency interval between a smallest target frequency (f _obj1, f _obj2) assigned to a target output (P _obj1, P _obj2) and a second smallest target frequency (f _obj1, f _obj2) assigned to a target output (P _obj1, P _obj2) is smaller than 17 kHz, the heat frequency unit (10a, 12a; 10b, 12b) with the second smallest target frequency (f _obj1, f _obj2) is continuously operated with the fixed first frequency (f ₁).
9. Cooking device, in particular hob, having a cooking device apparatus according to one of claims 1 to 7.

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