EP4019848A1

EP4019848A1 - Method for operating a cooking oven

Info

Publication number: EP4019848A1
Application number: EP20216537.9A
Authority: EP
Inventors: Sorin Tcaciuc
Original assignee: Electrolux Appliances AB
Current assignee: Electrolux Appliances AB
Priority date: 2020-12-22
Filing date: 2020-12-22
Publication date: 2022-06-29
Anticipated expiration: 2040-12-22
Also published as: EP4019848B1

Abstract

Method for operating a cooking appliance, in particular a domestic cooking appliance, including at least one food treatment chamber (2), at least one temperature sensor for sensing the temperature within the food treatment chamber (2), at least one heating element (3, 5, 6) for supplying heating energy into the food treatment chamber (2) and at least one control unit (8) for controlling operation of the cooking appliance, wherein the method includes the following steps:a) Receiving user input including setting of a set temperature value (TSet) that is desired to be reached within the food treatment chamber (2);b) Initially supplying heating energy into the food treatment chamber (2) to increase the temperature within the food treatment chamber (2) by controlling the at least one heating element (3, 5, 6) to operate at least at a predetermined first energy output level (P1) ;c) Determining whether the temperature within the food treatment chamber (2) reaches an upper temperature threshold (UTT) that is defined above the set temperature value (TSet);d) In response to reaching the upper temperature threshold (UTT), selecting a predetermined second energy output level (P2) based on a variable parameter dependent on a thermal load present in the food treatment chamber (2);e) Reducing the supply of heating energy into the food treatment chamber (2) such that the temperature within the food treatment chamber (2) decreases by controlling the heating element (3, 5, 6) to operate at the predetermined second energy output level (P2).

Description

The present invention relates to a method for operating a cooking appliance and to a cooking appliance for carrying out the method.
There are ways commonly known in the art, e.g. with respect to convection heating ovens, to control the temperature in an oven. Specifically, it is known to provide an initial heat up phase by operating a heating element at full without interruption until a desired set temperature, e.g. as set be a user. Upon reaching the set temperature, the heating element is controlled by means of a temperature sensor included in a closed loop control causing switch on and switch off of the heating element upon reaching a lower and an upper switching temperature.
EP 2 045 532 B1 discloses a method of controlling heaters of an electric cooking apparatus, wherein a temperature of a cooking cavity is detected and wherein a temperature increasing mode is performed in which a supply of power and a cutoff of power to the heaters are alternately performed while increasing a ratio of a power-off period to a power-on period if the detected temperature of the cooking cavity is not equal to a set temperature and performing a temperature maintaining mode in which the heaters are operated according to preset power-on and power-off periods to be maintained at a temperature within a certain range around a certain temperature if the detected temperature of the cooking cavity reaches the set temperature.
EP 1 394 472 B1 discloses a method for operating a cooking appliance with a cooking chamber, to which a quantity of heat is fed by means of a heating device, in which method a cooking chamber temperature is regulated to a target temperature in a regulating period, the cooking chamber temperature is not regulated in a control period following the regulating period, but no or a defined heat quantity is fed to the cooking chamber independently of the target value, and the cooking chamber is regulated in a post-regulation to the target value after the end of the control period, wherein the control period is prematurely interrupted if there is change in at least one influencing variable which influences the behavior over time of the cooking chamber temperature in the regulating period and/or in the control period, wherein the post-regulation is set to the target value directly after the premature interruption of the control period.
EP 2 662 630 B1 discloses a method for preparing food in a cooking chamber of a cooking appliance by means of a cooking process, wherein, during an initial phase of the cooking process, a high total heating power is introduced into the cooking chamber, and wherein, during a compensation phase of the cooking process which follows the initial phase, at most a low total heating power is introduced into the cooking chamber, and wherein, during a connecting phase of the cooking process which follows the compensation phase, a mean total heating power is introduced into the cooking chamber such that the high total heating power during the initial phase originates at least substantially from at least one thermal heat source, and that the total heating power introduced into the cooking chamber during the compensation phase is at most a fraction of the high total heating power, and that a total heating power is introduced into the cooking chamber during the connecting phase, which heating power is higher than during the compensation phase and lower than during the initial phase.
DE 10 2014 217 637 A1 discloses a method used for heating a cooking chamber of a domestic cooking appliance, wherein the cooking chamber is heated during an initial cooking phase with an uncontrolled heating power during an initial cooking phase and then during a phase with a heating power controlled to a setpoint temperature value and wherein the initial cooking phase has a first initial cooking phase comprises a first partial section and a second partial section adjoining it and wherein at the transition from the first partial section to the second partial section, at least one characteristic of the introduced heating power is changed.
The object of the present invention is to provide a method for operating a cooking appliance in an energy efficient way and a cooking appliance that can be energy efficiently operated.
This object is solved by a method according to claim 1 and by a cooking appliance according to claim 14.
According to the invention, a method is provided for operating a cooking appliance, in particular a domestic cooking appliance, including at least one food treatment chamber, at least one temperature sensor for sensing the temperature within the food treatment chamber, at least one heating element for supplying heating energy into the food treatment chamber and at least one control unit for controlling operation of the cooking appliance. T method includes the following steps:

a) Receiving user input including setting of a set temperature value that is desired to be reached within the food treatment chamber;
b) Initially supplying heating energy into the food treatment chamber to increase the temperature within the food treatment chamber by controlling the at least one heating element to operate at least at a predetermined first energy output level;
c) Determining whether the temperature within the food treatment chamber reaches an upper temperature threshold that is defined above the set temperature value;
d) In response to reaching the upper temperature threshold, selecting a predetermined second energy output level based on a variable parameter dependent on a thermal load present in the food treatment chamber;
e) Reducing the supply of heating energy into the food treatment chamber such that the temperature within the food treatment chamber decreases by controlling the heating element to operate at the predetermined second energy output level.

Initially supplying heating energy into the food treatment chamber shall be in particular understood as supplying heating energy into the food treatment chamber when the temperature in food treatment chamber is substantially equal to or at least not substantially higher than the temperature of the environment. Further, a variable parameter dependent on a thermal load present in the food treatment chamber shall be understood as a parameter that varies dependent on the volume, type, weight, liquid content, form, or the like, of the thermal load present in the food treatment chamber. The positive effect achieved by the matter of the invention is that temperature profile is achieved within the food treatment chamber that has the same result with respect to a cooking performance in comparison with commonly known temperature control, but that includes energy saving. In particular, the cooking appliance can be operated after the initial heating up phase with the second energy output level in a very energy efficient way. Additionally, it is possible in such way to achieve a temperature profile within the food treatment chamber that is very close to the set temperature value over the overall cooking time and in particular to avoid switching events for the heating element. Furthermore, the intended temperature profile within the food treatment chamber can be achieved irrespective of food stuff is present initially within the not-heated up food treatment chamber or if the empty food treatment chamber is initially heated up and the food stuff is inserted after the initial heating up phase.
According to an advantageous embodiment of the invention, additionally the following steps are included:

f) Determining whether the temperature within the food treatment chamber reaches a lower temperature threshold that is defined below the set temperature value;
g) In response to reaching the lower temperature threshold, increasing the supply of heating energy into the food treatment chamber such that the temperature within the food treatment chamber increases by controlling the heating element to operate at predetermined energy output level higher than the second predetermined energy output level, in particular at the predetermined first energy output level.

In this embodiment, the temperature profile within the food treatment chamber, in particular the average temperature over the overall length of the cooking time, matches the set temperature value advantageously.
According to a further advantageous embodiment of the invention, the thermal load present in the food treatment chamber is the empty volume of the interior of the food treatment chamber or is one or more pieces of food stuff and/or cookware being inserted into the food treatment chamber.
In other words, the second energy output level is selected depending on whether there is any food stuff within the food treatment chamber or not or, e.g. depending on the volume, weight or liquid content of the food stuff placed in the food treatment chamber. This allows to achieve the same temperature profile with the method irrespective of there is food stuff initially placed in the food treatment chamber or nor and irrespective of the volume, weight or liquid content of food stuff initially placed in the food treatment chamber.
According to an advantageous embodiment, selecting a predetermined second energy output level based on a variable parameter includes determining a time interval from a start point in time when the supply of heating energy is started or changed to a point in time when the temperature within the food treatment chamber reaches a temperature above the set temperature value, in particular reaches the upper temperature threshold, wherein the predetermined second energy output level is selected dependent on the length of the time interval.
A high thermal load shows a delay in the increase of the temperature value compared to a low thermal load. The time interval between the temperature passing the set temperature value and reaching the upper temperature threshold is advantageously suitable for being taken as a basis for determination of the thermal load within the food treatment chamber.
According to an additional advantageous embodiment, the predetermined second energy output level is selected the higher, the longer the length of the determined time interval is.
Thus, the second energy output can be adapted to the thermal load present in the food treatment chamber. This reflects the relation that a high thermal load causes a greater delay in the time interval compared to a lower thermal load, thus, automatically adapting the necessary energy output for cooking the high thermal load properly by providing a higher energy output.
According to a further advantageous embodiment of the invention, at least one data set is accessible for or is accessed by the control unit, in particular wherein the at least one data set is stored in a storage of the control unit or in a storage being accessible for the control unit, wherein the data set includes:

a first data type related to a variety of time intervals that may be determined by the control unit;
a second data type related to a variety of energy output levels allowed for the predetermined second energy output level and which may be set for the at least one heating element;

Such a data set simplifies the control of the cooking appliance. The data included in the data set may be evaluated in experiments for one specific cooking appliance having predefined properties, e.g. the volume of the food treatment chamber, the maximum output of the heating elements, etc. Different data sets may be evaluated for different types of cooking appliances. Additionally, it may be possible to make the data set interchangeably, such that an update of the data set is possible in order to achieve optimized performance of the cooking appliance.
According to a further advantageous embodiment, the initial supply of heating energy at a predetermined first energy output level includes determining whether the temperature in the food treatment chamber exceeds the set temperature value, wherein, in response to exceeding the set temperature value, the at least one heating element is controlled to operate at a predetermined third energy output level being lower than the predetermined first energy output level, in particular wherein the predetermined first energy output level corresponds to an energy output of 100% of the maximum energy output possible for the specific at least one heating element and wherein the predetermined third energy output level lies within a range between 30% to 70%, preferably at 50%, of the maximum energy output possible by the specific at least one heating element.
Thus, the increase in the temperature profile in the food treatment chamber can be slowed down upon passing the set temperature value, thus, enabling the differences in the time intervals for reaching the upper threshold temperature for different thermal loads to become greater. This simplifies the detection of the variable parameter with respect to the specific thermal load, making the detection of the thermal load more robust.
According to an advantageous embodiment of the invention, the cooking appliance further may include a fan being provided within the food treatment chamber for generating a hot air flow within the food treatment chamber, wherein the fan may be continuously operated during the phase of initial supply heating energy into the food treatment chamber with the predetermined first energy output level and/or during the phase of reduced supply of heating energy into the food treatment chamber with predetermined second energy output level and/or during the phase of increased supply of heating energy into the food treatment chamber at the predetermined energy output level higher than the second predetermined energy output level.
By operating the fan continuously, the hot air is distributed quicker within the food treatment chamber which causes in particular during the initial heat up phase a quicker increase in temperature. It may be specifically advantageous if the fan is operated until the temperature within the food treatment chamber exceeds the set temperature value, wherein the fan is stopped when the temperature passes the set temperature value until it reaches the upper threshold temperature. In this case, the differences in the time intervals for reaching the upper threshold temperature for different thermal loads become even greater.
In a further advantageous embodiment, a cooking cycle is defined by including the steps a) to e), in particular additionally including the steps f) and g), wherein the cooking cycle is further defined by having a predetermined length, wherein the cooking cycle is terminated automatically upon expiration of the predetermined length and wherein the temperature within the food treatment chamber passes the set temperature value not more than three times, in particular not more than two times, before expiration of the predetermined length.
The method is particular advantageous for cooking appliances applying automatic cooking programs having predetermined or predefined length. In such cases, the temperature profile achieved within the food treatment chamber can be held in conformity with the set temperature value irrespective of the thermal load present in the food treatment chamber.
Furthermore advantageous is an embodiment wherein a cooking cycle is defined by including the steps a) to e), in particular additionally including the steps f) and g), wherein the cooking cycle is further defined by having a, in particular predetermined, length, wherein an average temperature within the food treatment chamber calculated over the length of the cooking cycle has a value within a range from 5°C below to 5°C above the set temperature value.
It is particularly advantageous if the method is operated in that an average temperature is achieved to be within a range from 5°C below to 5°C above the set temperature value. This meets the requirements of the user's needs who intends a certain set temperature value, wherein the food stuff to be cooked becomes subject to a very precise temperature control over the full length of the cooking cycle.
Advantageously, the upper threshold temperature lies within a range between 10°C to 35°C, in particular between 15°C to 25°C, preferably between 15°C to 20°C above the set temperature value and/or wherein the lower threshold temperature (LTT) lies within a range between 10°C to 35°C, in particular between 15°C to 25°C, preferably between 15°C to 20°C below the set temperature value.
Those limits have been proven as being sufficient in achieving the intended temperature profile, wherein the quality of the cooked food stuff is not affected. At the same time, energy savings are optimized by using these limits.
According to a further advantageous embodiment of the invention, the control unit receives information from the temperature sensor and determines whether the temperature within the food treatment chamber reaches the upper temperature threshold or the lower temperature threshold, in particular wherein the control unit calculates reference temperature values being different from a current temperature value based on the information received from the temperature, based on the set temperature value and based on the predetermined first energy output level and the predetermined second energy output level and/or predetermined third energy output level, preferably wherein the control unit instructs a display of the cooking appliance to display the calculated reference temperature.
Thus, the user may receive information about a reference temperature related to the temperature within the food treatment chamber, that reflects the temperature profile over the overall length of the cooking cycle better than information about the current temperature within the food treatment chamber would do. The user, thus, may be enabled to anticipate the cooking results better compared to a case in which only the current temperature would be displayed.
Furthermore, according to an advantageous embodiment, the cooking appliance further includes at least one door for selectively opening and closing the food treatment chamber, wherein, in response to opening and closing of the door, determining whether the temperature within the food treatment chamber is above or below the lower temperature threshold, wherein the supply of heating energy into the food treatment chamber is increased when the temperature is determined to be below the lower temperature threshold and wherein the supply of heating energy into the food treatment chamber is maintained when the temperature is determined to be above the lower temperature threshold.
The door may be an oven door, but may be a lid of a cookware or a pot, also. This behavior allows the method to be properly carried out without being affect by opening and closing of the door and irrespective of the length of the opened status of the cooking appliance.
Further, according to the invention, a cooking appliance in particular a domestic cooking appliance, preferably a cooking oven including at least one food treatment chamber, at least one temperature sensor for sensing the temperature within the food treatment chamber, at least one heating element for supplying heating energy into the food treatment chamber and at least one control unit for controlling operation of the cooking oven, or
preferably a cooking hob including at least one piece of cookware defining at least one food treatment chamber being placed on a cooking zone of the cooking hob, at least one temperature sensor for sensing the temperature within the food treatment chamber, at least one heating element for supplying heating energy into the food treatment chamber and at least one control unit for controlling operation of the cooking hob, wherein the cooking appliance is configured to carry out the method according to the invention.
Such a cooking appliance is very energy efficient and allows to apply a temperature profile within a food treatment chamber that is very precise with respect to a set temperature preset by a user.
According to an advantageous embodiment, the cooking oven or the cooking hob comprise an electronic control unit including or enabled to carry out at least one or two or a plurality of automatic cooking programs, in particular wherein at least one automatic cooking program comprises the cooking cycle having the predetermined length.
The method according to the invention is particularly suitable for being embedded in an automatic cooking program to be carried out by an electronically controlled cooking appliance.
According to a further an advantageous embodiment, the control unit is configured to receive or comprises a data set including:

Such data set may be stored in a registry or a storage medium being connected with or comprised by the control unit or in an internet server being connected with the control unit and may be adapted to the respective type of cooking appliance.
The invention will be explained in further detail with reference to the accompanying drawings, in which:

Fig. 1 is a schematic view of a cooking oven suitable for carrying out a method according to an exemplary embodiment of the invention;
Fig. 2 is a diagram illustrating a temperature profile achieved by a method according to an exemplary embodiment of the invention; and
Fig. 3 is a diagram illustrating differences in the temperature profile of Fig. 2 for different thermal loads.

The cooking oven 1 provides an insulated food treatment chamber 2 in which the user may introduce food stuff to be cooked. Before or after the introduction of the foodstuff, the user may select a cooking program from the control panel 9 or may preset isolated cooking parameters such as cooking temperature and/or cooking time or may select specific heating elements 3, 5, 6.
Based on user requirements and the nature of the foodstuff, the user will choose a specific cooking function that may employ one or more of the heating elements 3, 5 and/or 6 with or without the convection fan 4, so that a multitude of options enables the user to match required cooking process criteria, e.g. by forced convection or in a traditional cooking mode. An oven thermostat 7, including a temperature sensor and the control unit 8 create all the proper conditions that the oven needs for operation according to the user's wishes.
For a commonly known preheating phase, preheating time depends on the cooking function and the set value for the oven thermostat, usually being shorter with forced air convection (i.e. with the heater 3 and the fan 4 switched on, but longer with traditional mode, or natural convection, i.e. with the heating elements 5 and 6 to the same value of the temperature setting.
Generally, in a cooking process, the forced air convection is more energy efficient, with respect to temperature performance and energy consumption related to the overall duration of the full cooking process.
The considerations on which the invention is based include recognizing that a temperature profile achieved by conventional closed loop control within a food treatment chamber is not ideal with respect to energy efficiency. A temperature profile that can be found for conventional closed loop control, e.g. within two switching phases, i.e. the temperature increases past a set temperature value and reaches an upper switching temperature, upon which the supply of heating energy is cutoff, which leads to a decrease in temperature below the set temperature value until a lower switch temperature is reached, which causes switching on of the heating element, wherein the temperature alternates between the upper and the lower switching temperature.
The inventors have found that the temperature profile as found for conventional closed loop control can be geometrically extended over the entire duration or length of the cooking process, resulting in the temperature profile according to Fig. 2.
In such an optimized cooking mode, the result of the integral of the process variable, i.e. the temperature within the food treatment chamber 2 can be indicated as a reference temperature T_ref that comes close to a set temperature value T_Set set by the user at the beginning of the cooking process, if taken over the complete length of the cooking process. It is possible that a display of the oven (not referenced) can show in real time the referenced temperature T_ref.
An upper temperature threshold UTT and a lower temperature threshold LTT are defined between which the current temperature value T_cur is held during the cooking phase with the intent to achieve proper cooking appliance performances, so that the food quality at the end of the cooking phase to be not affected. Empirical tests have shown that the upper temperature threshold UTT and a lower temperature threshold LTT, e.g. each comprised within a temperature band between 30°C and 40°C from the set temperature value T_Set are proper to hold a calculated average value of the oven temperature close to the set temperature value T_Set chosen by the user.
For each set temperature value T_Set selectable by the user, there is a temperature band in which the current temperature value T_cur follows the intended temperature. However, it is not necessary for a set temperature value T_Set set by the user to match exactly centrally the temperature band. In any case, at the end of the cooking phase the calculated average temperature demonstrates that the set temperature value T_Set was hold at least in the middle of the temperature band that offers the value selected by the user within a precise tolerance of maximum ± 5°C.
As shown in Fig. 2 and Fig. 3, there is a preheating phase provided in which the control unit 8 operates the heating element 3 and optionally the fan 4, wherein forced convection heating is used, at a starting point t₀. Starting with the initial ambient temperature, the heating element 3 is controlled by the control unit 8 to operate at a predetermined first energy output level P₁ = 100% of the maximum possible output level of the heating element 3. The oven thermostat 7 or, more precisely, the temperature sensor comprised by the oven thermostat 7, measures the temperature within the food treatment chamber 2. Thus, the temperature sensor detects when the temperature within the food treatment chamber 2 passes or exceeds a set temperature value T_Set set by the user at the beginning of the cooking process.
In response to passing or exceeding the set temperature value T_Set, the heating element 3 is controlled to operate at a reduced energy output level, namely a predetermined third output level P₃. The predetermined third output level P₃ may lie within a range between 30% to 70%, preferably at 50%, of the maximum energy output possible for the specific type of the at least one heating element 3.
Fig. 3 illustrates the difference in the temperature profiles for a high thermal load HTL, e.g. a large piece food including a high amount of water, e.g. a piece of meat to be cooked in broth, in comparison to a low thermal load LTL, e.g. a small piece of food including only small amount of water such as a small and dry cake. In both cases, the initial heat up phase is carried out by applying a predetermined first energy output level P₁ of 100% of the power possible for the heating element 3.
The food treatment chamber 2 comprising the low thermal load LTL is heated up slightly faster than the food treatment chamber 2 comprising the high thermal load HTL. Also in both cases, in response to passing the set temperature value T_Set, the energy output of the heating element 3 is reduced to a predetermined third energy output level P₃, e.g. of 50% of the maximum power possible for the heating element 3.
In the phase, when only a reduced energy output level P₃ is applied, the difference in time necessary for heating up the food treatment chamber 2 and the respective food load comprised therein enlarges for the high thermal load HTL compared to the low thermal load LTL.
In both cases, the heating element 3 is operated at the predetermined third energy output level P₃ until the temperature within the food treatment chamber 2 is determined to reach the upper temperature threshold UTT. As can be seen, the time interval Δt = t₂-LTL - t₁-LTL for the low thermal load LTL for the time interval necessary for reaching the upper temperature threshold UTT is significantly shorter than the time interval Δt = t₂-HTL - t₁-HTL for the high thermal load for reaching the upper temperature threshold UTT.

Also in both cases, in response to reaching the upper temperature threshold UTT, the control unit 8 controls the heating element 3 to operate at a predetermined second energy output level P₂. However, the selected predetermined second energy output level P₂ is different for each of the above outlined cases. The predetermined second energy output level P₂ is selected by the control unit 8 from a data set included in table 1:

Table 1

INPUT CONSTRAINTS		VARIABLE PARAME - TER	DEFAULT	SELECTION IN DEPENDANCE FROM ΔT	DEFAULT
Tset 175°C	Thermal load	Δt	Energy output level P₃	Energy output level P₂	Energy output level P ₄
1	Exceed HTL	Δt_Ex-ceed_HTL	50% of maximum possible	P_{2_}Exceed_HTL = 30% of maximum possible	50% of maximum possible
2	HTL	Δt_HTL	...	P₂_HTL = 30% of maximum possible	...
3	Load A	Δt_A	...	P₂_Load_A = 27% of maximum possible	...
4	Load B	Δt_B	...	P₂_Load_B = 25% of maximum possible	...
5	Load C	Δt_C	...	P₂_Load_C = 23% of maximum possible	...
6	...	...	...	...	...
7	Load N	Δt_N	...	P₂_Load_N = 17% of maximum possible	...
8	LTL	Δt_LTL	...	P₂_LTL = 15% of maximum possible	...
9	Below LTL	Δt_Be-low_LTL	50% of maximum possible	P₂_Below_LTL = 15% of maximum possible	50% of maximum possible

The control unit 8 may include a microprocessor for carrying out an algorithm using the dataset as exemplarily illustrated in table 1. The algorithm may be programmed to select from the given values of P₂ the value needed to achieve the temperature profile according to Fig. 2 for a given set temperature value T_set.
E.g. if a user selects a set temperature value of T_SET = 175°C to be reached within the food treatment chamber and inserts e.g. 1kg of a specific food including a specific amount of water being categorized as "Load B", the control unit determines the time interval Δt during the initial heating up phase when the oven is heated up with P₁=100% of the maximum possible power of the heating element 3 and, upon passing T_SET = 175°C, the power of the heating element 3 is reduced to P₃=50% of the maximum possible power of heating element 3. The determined time interval Δt is the time interval Δt_Load_B. Alterntatively formulated, the control unit 8 determines the load category of the thermal load by determining the time interval Δt and selects the value for the energy output level that is adapted to the determined load category. Accordingly, the algorithm is carried out to select P₂ as predetermined for the time interval Δt_Load_B, namely P₂=25% of the maximum possible for the specific heating element 3.
Data sets according to table 1 may be prepared and stored to be accessed by the control unit 8 for a plurality of possible set temperature values T_SET. E.g. several data sets may be compiled and stored in a library for a specific cooking appliance and, e.g., may be stored in an internal storage of the control unit 8 or may be stored outside the control unit 8, but may still be accessible for the control unit 8. Different data compilations of data sets may be stored in further libraries for other specific cooking appliances.

LIST OF REFERENCE NUMERALS

1: Cooking oven
2: Food treatment chamber
3: Heating element
4: Fan
5: Heating element
6: Heating element
7: Thermostat
8: Control unit
9: Operation panel

T: Temperature
t: Time
UTT: Upper temperature threshold
LTT: Lower temperature threshold
HTL: High thermal load
LTL: Low thermal load
Tref: Reference temperature
TSet: Set temperature value
Tcur: Current temperature value
Δt: Time interval
P1: Predetermined first energy output level
P2: Predetermined second energy output level
P3: Predetermined third energy output level
P4: Predetermined fourth energy output level

Claims

Method for operating a cooking appliance, in particular a domestic cooking appliance, including at least one food treatment chamber (2), at least one temperature sensor for sensing the temperature within the food treatment chamber (2), at least one heating element (3, 5, 6) for supplying heating energy into the food treatment chamber (2) and at least one control unit (8) for controlling operation of the cooking appliance, wherein the method includes the following steps:
a) Receiving user input including setting of a set temperature value (T_Set) that is desired to be reached within the food treatment chamber (2);

b) Initially supplying heating energy into the food treatment chamber (2) to increase the temperature within the food treatment chamber (2) by controlling the at least one heating element (3, 5, 6) to operate at least at a predetermined first energy output level (P₁);

c) Determining whether the temperature within the food treatment chamber (2) reaches an upper temperature threshold (UTT) that is defined above the set temperature value (T_Set);

d) In response to reaching the upper temperature threshold (UTT), selecting a predetermined second energy output level (P₂) based on a variable parameter dependent on a thermal load present in the food treatment chamber (2);

e) Reducing the supply of heating energy into the food treatment chamber (2) such that the temperature within the food treatment chamber (2) decreases by controlling the heating element (3, 5, 6) to operate at the predetermined second energy output level (P₂).
Method according to claim 1, characterized by:
f) Determining whether the temperature within the food treatment chamber (2) reaches a lower temperature threshold (LTT) that is defined below the set temperature value (T_Set);

g) In response to reaching the lower temperature threshold (LTT), increasing the supply of heating energy into the food treatment chamber (2) such that the temperature within the food treatment chamber (2) increases by controlling the heating element (3, 5, 6) to operate at predetermined energy output level higher than the second predetermined energy output level (P₂), in particular at the predetermined first energy output level (P₁).
Method according to any one of the preceding claims, characterized in that the thermal load present in the food treatment chamber (2) is the empty volume of the interior of the food treatment chamber (2) or is one or more pieces of food stuff and/or cookware being inserted into the food treatment chamber (2).
Method according to any one of the preceding claims, characterized in that selecting a predetermined second energy output level (P₂) based on a variable parameter includes determining a time interval (Δt) from a start point in time when the supply of heating energy is started or changed to a point in time when the temperature within the food treatment chamber (2) reaches a temperature above the set temperature value (T_Set), in particular reaches the upper temperature threshold (UTT), wherein the predetermined second energy output level (P₂) is selected dependent on the length of the time interval (Δt).
Method according to claim 4, characterized in that the predetermined second energy output level (P₂) is selected the higher, the longer the length of the determined time interval (Δt) is.
Method according to claim 4 or 5, characterized in that at least one data set is accessible for or is accessed by the control unit (8), in particular wherein the at least one data set is stored in a storage of the control unit (8) or in a storage being accessible for the control unit (8),
wherein the data set includes:
- a first data type related to a variety of time intervals that may be determined by the control unit (8);

- a second data type related to a variety of energy output levels allowed for the predetermined second energy output level (P₂) and which may be set for the at least one heating element (3, 5, 6);
wherein the control unit (8) determines the time interval (Δt) and, upon determination of the time interval (Δt), selects from the second data type the predetermined second energy output level (P₂) being related with the determined time interval (Δt) according to the data set;
Method according to any one of the preceding claims, characterized in that the initial supply of heating energy at a predetermined first energy output level (P₁) includes determining whether the temperature in the food treatment chamber (2) exceeds the set temperature value (T_Set), wherein, in response to exceeding the set temperature value (T_Set), the at least one heating element (3, 5, 6) is controlled to operate at a predetermined third energy output level (P₃) being lower than the predetermined first energy output level (P₁), in particular wherein the predetermined first energy output level (P₁) corresponds to an energy output of 100% of the maximum energy output possible for the specific at least one heating element (3, 5, 6) and wherein the predetermined third energy output level (P₃) lies within a range between 30% to 70%, preferably at 50%, of the maximum energy output possible by the specific at least one heating element (3, 5, 6) .
Method according to any one of the preceding claims, characterized in that the cooking appliance further includes a fan (4) being provided within the food treatment chamber (2) for generating a hot air flow within the food treatment chamber (2), wherein the fan (4) is continuously operated during the phase of initial supply of heating energy into the food treatment chamber (2) with the predetermined first energy output level (P₁) and/or during the phase of reduced supply of heating energy into the food treatment chamber (2) with the predetermined second energy output level (P₂) and/or during the phase of increased supply of heating energy into the food treatment chamber (2) at the predetermined energy output level higher than the second predetermined energy output level.
Method according to any one of the preceding claims, characterized in that a cooking cycle is defined by including the steps a) to e), in particular additionally including the steps f) and g), wherein the cooking cycle is further defined by having a predetermined length, wherein the cooking cycle is terminated automatically upon expiration of the predetermined length and preferably wherein the temperature within the food treatment chamber (2) passes the set temperature value (T_Set) not more than three times, further preferably not more than two times, before expiration of the predetermined length.
Method according to any one of the preceding claims, characterized in that a cooking cycle is defined by including the steps a) to e), in particular additionally including the steps f) and g), wherein the cooking cycle is further defined by having a, in particular predetermined, length, wherein an average temperature within the food treatment chamber (2) calculated over the length of the cooking cycle has a value within a range from 5°C below to 5°C above the set temperature value (T_Set).
Method according to any one of the preceding claims, characterized in that the upper threshold temperature (UTT) lies within a range between 10°C to 35°C, in particular between 15°C to 25°C, preferably between 15°C to 20°C above the set temperature value (T_Set) and/or wherein the lower threshold temperature (LTT) lies within a range between 10°C to 35°C, in particular between 15°C to 25°C, preferably between 15°C to 20°C below the set temperature value (T_Set).
Method according to any one of the preceding claims, characterized in that the control unit (8) receives information from the temperature sensor and determines whether the temperature within the food treatment chamber (2) reaches the upper temperature threshold (UTT) or the lower temperature threshold (LTT), in particular wherein the control unit (8) calculates reference temperature values (T_ref) being different from a current temperature value (T_cur) based on the information received from the temperature, based on the set temperature value (TSet) and based on the predetermined first energy output level (P₁) and the predetermined second energy output level (P₂) and/or the predetermined third energy output level (P₃), preferably wherein the control unit (8) instructs a display of the cooking appliance to display the calculated reference temperature value (T_ref).
Method according to any one of the preceding claims, characterized in that the cooking appliance further includes at least one door for selectively opening and closing the food treatment chamber (2), wherein, in response to opening and closing of the door, determining whether the temperature within the food treatment chamber (2) is above or below the lower temperature threshold (LTT), wherein the supply of heating energy into the food treatment chamber (2) is increased when the temperature is determined to be below the lower temperature threshold (LTT) and wherein the supply of heating energy into the food treatment chamber (2) is maintained when the temperature is determined to be above the lower temperature threshold (LTT).
Cooking appliance, in particular domestic cooking appliance, preferably cooking oven (1) including at least one food treatment chamber (2), at least one temperature sensor for sensing the temperature within the food treatment chamber (2), at least one heating element (3, 5, 6) for supplying heating energy into the food treatment chamber (2) and at least one control unit (8) for controlling operation of the cooking oven (1),
or
preferably cooking hob including at least one piece of cookware defining at least one food treatment chamber (2) being placed on a cooking zone of the cooking hob, at least one temperature sensor for sensing the temperature within the food treatment chamber (2), at least one heating element (3, 5, 6) for supplying heating energy into the food treatment chamber (2) and at least one control unit (8) for controlling operation of the cooking hob,
wherein the cooking appliance is configured to carry out a method according to any one of the preceding claims.
Cooking appliance according to claim 14, characterized in that the cooking oven (1) or the cooking hob comprise an electronic control unit (8) including or enabled to carry out at least one or two or a plurality of automatic cooking programs, in particular wherein at least one automatic cooking program comprises the cooking cycle having the predetermined length.