Method for regulating a cooking process

Abstract

The invention relates to a method for regulating a cooking process using an item of cookware having inductive properties on a cooking area, wherein a coil is arranged as part of an LC resonant circuit in the region of the cooking area and the natural frequency of the LC resonant circuit is measured repeatedly or continuously. The invention also relates to a cooking apparatus having at least one cooking area, a temperature sensor, a power controller, an LC resonant circuit having a coil, which is arranged in, around or in the region of the cooking area, and a controller, which is connected to the temperature sensor and a unit for measuring the frequency of the LC resonant circuit and which is programmed to carry out method, wherein the controller has access to a memory for storing the mathematically determined parameter function or vector function.

Claims

1. A method for regulating a cooking process using an item of cookware having inductive properties on a cooking area, wherein a coil is arranged as part of an LC resonant circuit in a region of the cooking area and a natural frequency of the LC resonant circuit is measured repeatedly or continuously, said method having the following method steps: A) alternately heating the cooking area with at least two different target powers, wherein a first target power is held longer than a second target power, and wherein the first target power is selected to be higher than the second target power, wherein during this process a temperature at a bottom of the item of cookware is repeatedly or continuously measured using a temperature sensor to generate a measured temperature profile and said natural frequency of the LC resonant circuit is repeatedly or continuously measured; B) determining a parameter function or vector function from the measured temperature profile over time of the temperature sensor and from the frequency of the LC resonant circuit depending on the time and depending on the least two target powers; and C) conducting the cooking process depending on the parameter function or vector function determined in method step B) and depending on the frequency of the LC resonant circuit and/or the change over time of the frequency of the LC resonant circuit.

2. The method according to claim 1, wherein an induction cooking zone is used as a cooking area, and an induction coil of the induction cooking zone or a separate coil is used as a coil.

3. The method according to claim 1, wherein with the alternate heating of the cooking area, at least one first target power is selected from 50% to 100% of a nominal power of the cooking area and at least one second target power is selected up to at most 25% of the nominal power of the cooking area.

4. The method according to claim 3, wherein the at least one second target power is selected up to at most 15% of the nominal power of the cooking area.

5. The method according to claim 1, wherein the temperature sensor after method step B) is no longer used to measure the temperature of the surface of the item of cookware.

6. The method according to claim 5, wherein the temperature sensor after method step B) the temperature sensor is detachable from the item of cookware and is removed from the item of cookware after method step B) or is placed in the food to be cooked or an instruction is provided to the user of the cooking apparatus, said instruction asking the user to remove the temperature sensor or to place said sensor in the food to be cooked.

7. The method according to claim 1, wherein the first target power is held longer than a second target power, and wherein the first target power is selected to be at least three times higher than the second target power.

8. The method according to claim 7, wherein the first target power is selected to be at least three times as high as the second target power.

9. The method according to claim 7, wherein the first target power is held between 30 and 120 seconds and the second target power is held between 15 and 60 seconds.

10. The method according to claim 1, wherein at least one variable selected from the group consisting of a profile over time of the temperature of the surface of the item of cookware measured using the temperature sensor, a profile over time of the measured power of the cooking area, a profile over time of the target power of the cooking area, and a profile over time of the frequency of the LC resonant circuit, or at least one of a first time derivative and a second time derivative of at least one said variable is used to determine the parameter function or vector function.

11. The method according to claim 1, wherein at least one variable selected from the group consisting of a profile over time of the measured power of the cooking area, a profile over time of the target power of the cooking area, and a profile over time of the frequency of the LC resonant circuit, or at least one of a first time derivative and a second time derivative of at least one said variable is used to conduct the cooking process depending on the frequency of the LC resonant circuit.

12. The method according to claim 1, wherein each determined parameter function or vector function is assigned to an item of cookware or a class of cookware, and the cooking process is conducted depending on the parameter function or vector function.

13. The method according to claim 12, wherein each determined parameter function or vector function is stored together with a labelling for the item of cookware or the class of cookware in an electronic memory.

14. The method according to claim 1, wherein after method step B) the item of cookware is heated to a first target temperature, wherein the temperature sensor and/or the frequency of the LC resonant circuit and/or the parameter or vector function for determining the current temperature of the item of cookware is used for this purpose.

15. The method according to claim 14, wherein different values are stored for the frequency of the LC resonant circuit or a variable calculated or derived therefrom, and the stored values or the variable is used as a reference for subsequent regulations on the basis of the frequency of the LC resonant circuit.

16. The method according to claim 1, wherein the temperature sensor, after reaching the target temperature, is removed from the item of cookware or placed in a food to be cooked, or an instruction is provided to the user of the cooking apparatus, asking the user to remove the temperature sensor or to place the temperature sensor in the food to be cooked.

17. The method according to claim 1, wherein in the event of a maintaining phase of the cooking process, in which the temperature of the item of cookware is to be kept constant, a two-point regulation or a multi-point regulation is used, wherein the at least two target powers in method step A) are used as power stages for the two-point regulation or multi-point regulation and the temperature is determined several times by calculation using the parameter function or the vector function from the measured frequency of the LC resonant circuit.

18. The method according to claim 1, wherein by evaluation of the frequency of the LC resonant circuit with the parameter function or the vector function, it is determined whether a food to be cooked or a cooking medium is introduced into the item of cookware during the cooking process, whether the food to be cooked is burning, whether the cooking medium is overcooking, whether the position of the item of cookware on the cooking area has changed and/or the manner in which the food to be cooked is arranged physically in the item of cookware, and the cooking process is controlled in accordance with this determination and/or an instruction is provided to the user of the cooking apparatus.

19. The method according to claim 1, wherein the cooking process is selectively controlled by an adjustment of the power of the cooking area depending on the progress of the cooking process, a target time and/or the desired result, wherein, to determine the temperature of the item of cookware, the frequency of the LC resonant circuit is used with application of the parameter function or the vector function for calculation of the temperature.

20. The method according to claim 1, wherein the method with method steps A) and B) is used to calibrate the item of cookware, wherein the parameter function or the vector function is stored, and when an item of cookware is placed on the cooking area (2) with method steps A) and B) a known item of cookware is identified on the basis of the parameter function or vector function and the previously stored parameter function or vector function is used to conduct the cooking process during the evaluation of the frequency of the LC resonant circuit in method step C).

21. A cooking apparatus comprising: (a) at least one cooking area, (b) a temperature sensor, (c) a power controller, (d) an LC resonant circuit having a coil arranged in a region of the at least one cooking area, and (e) a controller connected to the temperature sensor and to a unit for measuring a frequency of the LC resonant circuit and programmed to carry out a method for regulating a cooking process using an item of cookware having inductive properties on the at least one cooking area, the LC resonant circuit having a natural frequency, said method having the following method steps: i) alternately heating the cooking area with at least two different target powers, wherein a first target power is held longer than a second target power, and wherein the first target power is selected to be higher than the second target power, repeatedly or continuously measuring a temperature at a bottom of an item of cookware being heated using the temperature sensor to generate a measured temperature profile, and repeatedly or continuously measuring said natural frequency of the LC resonant circuit; ii) determining a parameter function or a vector function from the measured temperature profile over time of the temperature sensor and from the frequency of the LC resonant circuit depending on the time and depending on the least two target powers; and iii) conducting the cooking process depending on the parameter function or the vector function determined in method step ii) and depending on the frequency of the LC resonant circuit and/or the change over time of the frequency of the LC resonant circuit, wherein the controller has access to a memory for storing the mathematically determined parameter function or vector function for determining the temperature of an object.

22. The cooking apparatus according to claim 21, wherein the cooking apparatus has a temperature measuring probe, which is connected wirelessly to the controller and at a tip of which the temperature sensor for measuring the surface temperature of an item of cookware is arranged.

23. A cooking apparatus according to claim 21, wherein said at least one cooking area is at least one induction cooking zone.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) Exemplary embodiments of the invention will be explained hereinafter on the basis of three schematically illustrated figures and graphs, although the invention is not limited hereto. In the drawings:

(2) FIG. 1: shows a schematic illustration of a cooking apparatus according to the invention for carrying out a method according to the invention;

(3) FIG. 2: shows a graph, in which the target power P.sub.s (solid line) and the effectively applied power P.sub.act (dashed line) are illustrated over time during a method according to the invention; and

(4) FIG. 3: shows a graph of the resultant temperature signal T.sub.pwm(t) (solid line) for a pan as item of cookware and the regulated item of cookware temperature T.sub.pot(t) (dashed line) over time t.

DETAILED DESCRIPTION

(5) FIG. 1 shows a schematic illustration of a cooking apparatus according to the invention, which is suitable for carrying out a method according to invention and on the basis of which a method according to the invention will be explained.

(6) In order to carry out the invention, a cooking apparatus 1 having at least one cooking area 2 or cooking zone 2 is used, which cooking area or zone can be heated via a heating unit, ideally via an induction heating unit. The energy feed for each cooking area 2 is regulated here individually by a built-in microcontroller.

(7) In each cooking area 2, a coil 3 or induction coil 3 is embedded, which is mounted separately from the induction heating coil of the cooking area 2. The coils 3 are parts of separate LC resonant circuits 4 comprising the coil 3 for each cooking area 2 with coupled evaluation electronics 5, which measures the temperature-dependent permeability of the item of cookware (not shown). Besides the coil 3, the LC resonant circuit 4 also has a capacitor in the form of a condenser, which is electrically connected to the coil 3 and is illustrated schematically in FIG. 1.

(8) The evaluation electronics 5 is connected to a frequency measuring apparatus (not shown) for determining the frequency or the natural frequency of the LC resonant circuit 4. The measurement of permeability can be taken in a different manner by means of known methods. Here, it is advantageous to continuously measure the change of the oscillation period on the basis of the change of the impedance and of the resistance in the LC resonant circuit 4.

(9) The evaluation electronics 5 delivers a continuous temperature signal or a temperature signal updated at discrete time intervals T.sub.pwm, which is dependent on the set target power P.sub.s, the actually recorded power P.sub.act, the starting temperature of the coil 3, the starting temperature of the item of cookware, and the structure and material composition of the item of cookware. With use in an induction hob, the influences of the heating unit on the LC resonant circuit 4 or the measurements and measurement results can be minimised by the use of measures known to the technical experts or a person skilled in the art.

(10) As input unit the cooking apparatus 1 has a control panel 6. A receiver/transmitter 8 for an external operating unit 12 and a receiver 9 for a temperature measuring probe 14 are connected and can be controlled via the controller 5 of the cooking apparatus 1. With the aid of antennas 10, the receiver 9 and the receiver/transmitter 8 can receive data from the temperature measuring probe 14 or can exchange data with the operating unit 12 via radio, infrared, Bluetooth or another wireless communication. The radio waves for the wireless data transfer are illustrated in FIG. 1 in each case by three circular segments arranged inside one another.

(11) The cooking apparatus 1 has a bus system. The relevant data relating to the target power P.sub.s, the effectively applied power P.sub.act, the temperature signal T.sub.pwm, and the ambient temperature T.sub.u are transferred via this bus system. The cooking areas 2 can be operated manually at the cooking apparatus 1 via a control panel 6 or via an external operating unit 12, such as a Smartphone.

(12) The temperature is measured by the use of the temperature measuring probe 14, ideally wirelessly, which measures the temperature at the surface of the item of cookware T.sub.pot during the heating, without food to be cooked. Later, this temperature measuring probe 14 can also be used in the food to be cooked, as described for example in WO 2012/149997 A1, in order to determine further parameters of the food to be cooked and the progress of the cooking process.

(13) For the structure of the temperature measuring probe 14, it is advantageous here to place a suitable temperature sensor (not shown) directly in the tip of the temperature measuring probe 14. The signal is processed in the temperature measuring probe 14 in order to then be transferred wirelessly to a corresponding, external evaluation electronics 5. However, an evaluation electronics may also be built-in directly in the temperature measuring probe 14. It is also conceivable for the external operating unit 12 to be integrated directly into the housing of the temperature measuring probe 14.

(14) FIG. 2 shows a graph in which the target power P.sub.s (solid line) and the effectively applied power P.sub.act (dashed line) (as a percentage on the basis of the maximum power) are illustrated over time t (in seconds) during a method according to the invention, and FIG. 3 shows a graph of the resultant temperature signal T.sub.pwm(t) (solid line) for a pan as item of cookware and the regulated item of cookware temperature T.sub.pot(t) (in C.) over time t (in seconds).

(15) The first heating cycle as described lasts 50 seconds, wherein the heating phase is 30 seconds and the cooling phase is 20 seconds. With the aid of the determined parameter or vector function or of the temperature measuring probe, heating is then performed to the target temperature, in this example to 110 C. This lasts for 30 seconds. This surface temperature T.sub.pot is then kept constant by means of the described regulation of the determined T.sub.pwm value for a certain period of time. It can be clearly seen how the T.sub.pwm value in this example correlates with the item of cookware temperature T.sub.pot. The temperature signal T.sub.pwm resulting from the frequency of the LC resonant circuit can therefore be used to determine the temperature of the item of cookware or can be used directly to control the cooking process.

(16) The features of the invention disclosed in the above description and in the claims, figures and exemplary embodiments may be essential both individually and in any combination for the implementation of the invention in its various embodiments.

LIST OF ABBREVIATIONS

(17) T.sub.pwm temperature signal

(18) T.sub.pwm(t.sub.0), P.sub.1(t.sub.0) temperature signal at the moment t.sub.0 at predefined target power P.sub.1(t.sub.0)

(19) P.sub.s target power of the cooking zone

(20) P.sub.act effective applied power of the cooking zone

(21) T.sub.pot temperature at the item of cookware surface or in the cooking medium

(22) T.sub.u ambient temperature

(23) t time

(24) t.sub.0 moment 0

(25) t.sub.n moment n, for example 50 sec after t.sub.0

(26) t.sub.n+1 moment n+1, for example 55 sec t.sub.0

(27) P.sub.i actually P.sub.s at different stages, wobble power,

(28) T.sub.pot(t), T.sub.u(t) temperature depending on time

(29) T.sub.pot(t)/T.sub.pot(t) vector function or parameter function for the temperature at the item of cookware surface

(30) f(T.sub.pwm): t.sub.n, t.sub.n+1, P.sub.1 first derivative of the temperature signal between 2 moments with a predefined, constant target power during this period of time

(31) c.sub.pot specific heat of the item of cookware, determined from the recorded work (integral over P.sub.s) divided by the measured difference T.sub.pot

(32) T.sub.pwm(T.sub.pot) value for the temperature signal when a target temperature (measured or calculated) is reached.

LIST OF REFERENCE SIGNS

(33) 1 cooking apparatus 2 cooking area 3 coil/inductivity 4 LC resonant circuit 5 controller/microcontroller 6 control panel 8 operating unit receiver 9 temperature sensor receiver 10 antenna 12 operating unit 14 temperature measuring probe