WO2022106164A1

WO2022106164A1 - Domestic cooking appliance and method for operating the same

Info

Publication number: WO2022106164A1
Application number: PCT/EP2021/079793
Authority: WO
Inventors: Christian Böttcher; Hans-Martin Eiter; Bastian Grass; Michael Heinz; Markus Kuchler
Original assignee: BSH Hausgeräte GmbH
Priority date: 2020-11-20
Filing date: 2021-10-27
Publication date: 2022-05-27
Also published as: EP4248134A1; DE102020214636A1

Abstract

A domestic cooking appliance has a cooking chamber and has at least one heat-introduction apparatus for introducing thermal energy into the cooking chamber and has a data-processing device which is designed so that a quantity of heat absorbed by a product treated in the cooking chamber by means of the thermal energy is calculated on the basis of an energy consumption (Ea, Ea_a, Ea_r) by the at least one heat-introduction apparatus, wherein the domestic cooking appliance is designed to control a cooking process based on the quantity of heat absorbed. A method serves for operating a domestic cooking appliance, wherein a quantity of heat absorbed by a product treated in a cooking chamber by means of thermal energy is calculated on the basis of an energy consumption (Ea, Ea_a, Ea_r) by at least one heat-introduction apparatus, and a cooking process is controlled based on the quantity of heat absorbed. The invention is particularly advantageously applicable to ovens.

Description

Household cooking appliance and method for operating the same

The invention relates to a domestic cooking appliance, having a cooking chamber and at least one heat input device for introducing thermal energy into the cooking chamber, the domestic cooking appliance being set up to control a cooking process. The invention also relates to a method for operating such a domestic cooking appliance. The invention can be applied particularly advantageously to ovens and/or steamers.

The prior art includes weight measurement directly via weight-detecting sensors, specifically in microwave ovens, since there are no high temperatures in the cooking chamber, as described in JP 2012 247145 A, for example.

JP H 0317429 A describes an indirect weight detection via a speed variation of a turntable motor with different load states of a microwave oven.

It is also known to calculate the estimated cooking time based on a weight measured by a sensor, as described in JP 2001173961 A, for example.

CN 100334395 C describes a weight estimation based on temperature changes of an item to be cooked over time, through which the weight is estimated and divided into the classes “small”, “medium” and “large”.

US 2017071393 A discloses a method for controlling a cooking process of a food. The method includes a step of detecting a change in weight of a first vaporizable component in the food over a first period of time. The method also includes a step of determining an initial condition of the foodstuff based at least in part on the sensed change in weight of the first vaporizable component in the foodstuff. The method also includes a step of controlling the cooking process based at least in part on the determined initial status of the food. CN 1540233 A discloses a method for determining the cooked weight in a microwave oven. It includes setting several reference voltage values after switching on the power supply with increasing cooking chamber temperature.

DE 10 2007 011 565 A1 discloses a method for determining the initial state of an item to be cooked, in particular baked goods, for the purpose of guiding a cooking process depending on the initial state determined, in which at least one surface temperature of the item to be cooked is recorded over at least one time interval, and at least one maximum value and/or at least one turning point of the profile of the surface temperature over time is determined.

It is the object of the present invention to at least partially overcome the disadvantages of the prior art and in particular to provide an improved possibility for controlling a household cooking appliance, specifically for more cost-effective determination of the weight of a load heated in a cooking chamber of a cooking appliance.

This object is solved according to the features of the independent claims. Preferred embodiments can be found in particular in the dependent claims.

The object is achieved by a cooking appliance having a cooking chamber and at least one heat introduction device for introducing thermal energy into the cooking chamber and a data processing device which is set up to calculate a quantity of heat absorbed by a load that has been treated in the cooking chamber using the thermal energy on the basis of an energy consumption of the at least one To calculate heat input device, wherein the domestic cooking appliance is adapted to control a cooking process based on the amount of heat absorbed.

This achieves the advantage that an operating parameter that can be measured with high accuracy and that reflects the cooking state of the item to be treated can be used with simple and inexpensive means to control or adapt cooking processes. which in turn makes it possible to achieve a particularly high degree of certainty that the item to be treated will succeed.

However, automatic programs other than cooking processes can also be controlled on the basis of the determined heat absorption, for example a pyrolysis operation. Here the device can, for example, use the determined heat absorption to recognize whether there is a load in the cooking compartment during pyrolysis operation and then cancel the pyrolysis operation. It can thus be prevented that food stored in the cooking chamber is burned.

The heat input device is intended to generate thermal energy that is used to heat the items to be treated located in the cooking chamber. The thermal energy can include thermal radiation radiated directly onto the item to be treated, conventional heat and/or thermal energy introduced into the cooking space with steam, etc. The at least one heat input device can comprise at least one heat radiator, for example at least one IR radiator and/or at least one electrically operated resistance heating element, e.g. a bottom heating element, a top heating element, a grill heating element and/or a ring heating element. The at least one heat input device may additionally or alternatively include a steam generator, etc. It is also possible, depending on the process, to radiate microwaves (energy) into the cooking chamber in addition to thermal energy, in which case energy consumption by the microwave generator required for carrying out the above method can also be taken into account, but is not necessary.

The data processing device can be an independent device or functionally integrated into another device of the cooking appliance, e.g. in a control device of the cooking appliance.

The cooking appliance may be an oven, a steamer, a warming drawer or any combination thereof, e.g. Loads can be understood as meaning any objects that are brought into the cooking chamber to carry out a heat treatment process, e.g.

It is a development that the cooking appliance is a domestic cooking appliance.

The energy consumption corresponds to the energy or power fed into the at least one heat input device to operate it, in particular electrical energy or power in the case of electrically operated heat input devices, minus design-related heat losses from the cooking chamber and/or for heating the cooking chamber.

In one configuration, the data processing device is set up to use the amount of heat absorbed to determine a weight of the load and the domestic cooking appliance is set up to control a cooking process based on the weight determined.

In this way, the advantage is achieved that a more precise automatic determination of the weight of the load, in particular the food to be cooked, can be carried out during a cooking process than was previously the case without weight sensors. This in turn allows cooking processes to be reliably adapted to the weight of the food to be cooked. For example, cooking processes can advantageously be carried out in a particularly energy-saving manner, and the success of the cooking process can be achieved in a particularly reliable manner. The adjustment may include, for example, changing a cooking cavity temperature, turning certain heat input devices on or off, changing a cooking time end, and so on. In particular, conventional cooking processes that include the weight of the items to be treated can also be used, e.g. to determine the end of a cooking time.

This determination of the weight is particularly advantageous for the process control by means of automatic cooking processes or automatic programs. These often use the automatically determined weight information to select suitable operating parameters and cooking times. Using the cooking device, it is possible to pass on an increasingly accurate weight estimate to the automatic programs during operation, so that they Be able to adapt to the weight better and better over the course of the operation, which increases the certainty of success, for example avoids undercooking or overcooking. In particular, use is made of the fact that food initially only cooks very little, so that this process can be implemented in practice, since it is not decisive whether during the first twenty minutes, for example (of which a large part typically falls during the heating-up phase), the exact time for a certain weight suitable operating parameters are set. Only after some time - usually only after about half of the entire cooking process - does it become more and more important for a good cooking result and for a precise prediction of the end of the cooking time, which cooking chamber temperature prevails in the cooking chamber and/or whether it is best for the cooking process at hand suitable process technology is used (e.g. the right combination of heating elements such as top and bottom heat and/or a precisely tailored additional proportion of microwave energy, etc.). The general approach may therefore include cooking with default process settings at the beginning of a cooking session until a first rough estimate of the weight is obtained, and then adjusting for more and more precise process control with a more and more precise weight estimate. At the latest when a steady state (which is described in more detail below) is reached, an exact prediction of the end of the cooking time can also be made and communicated to the user via the display.

This procedure can be used in the same way for manually set cooking processes.

In a further development, the weight of the load, in particular the item to be cooked, is not yet known at the start of operation. The weight can then be calculated during the cooking process, with the weight initially being roughly determinable and then being able to be determined more and more precisely. This is particularly user-friendly. However, it is also possible that the weight has initially been entered by a user and is adjusted to the measured (actual) weight by the method. This can also be particularly advantageous if the weight of the item to be treated changes during the cooking process, e.g. due to water loss.

In one embodiment, the weight or, equivalently, the mass m of the load is calculated from the amount of heat Q absorbed, based on the relationship m = f (Q, Tsoii, ...) with Tsoii a set desired cooking chamber temperature and f an experimentally and/or numerically determined function. The function f can, for example, take into account thermal properties of the cooking space such as heat losses, etc., which may depend on the current temperature of the cooking space.

It can be used here that the specific heat capacity c _w can be assumed as an undifferentiated, general value for many different loads (in particular food), since c _w is surprisingly roughly the same for many different loads. The weight m of the item to be cooked can therefore be used advantageously even without knowing the type of item being loaded, in particular even without precise knowledge of its specific thermal capacity c _w .

In addition to the cooking chamber target temperature T _S0 _u , the function f can also include other parameters, if known, e.g load, a type of activated heat input device, etc., as also explained in more detail below.

The weight m can be determined particularly easily from one of the relationships m = f (Tsoii, ...) ■ Q or m = (1 / c _w ) • f" (Tsoii, ...) ■ Q, since then the Function f (which no longer depends on the amount of heat Q) and in particular the function f" (which no longer depends on the amount of heat Q and the specific thermal capacity c _w of the load) can be calculated more easily and, moreover, only once for the set cooking chamber temperature T _S0 H and possibly the other parameters need to be determined, while the absorbed heat amount Q and, in the case of f", the specific heat capacity c _w are easily variable as factors.

In one configuration, the data processing device is set up to calculate the determined heat absorption, and in particular the weight therefrom, on the basis of an energy consumption accumulated over time. This is particularly advantageous since the amount of heat introduced into the load can be determined particularly precisely in this way.

In one configuration, the data processing device is set up to calculate the determined heat absorption, and in particular the weight from it, using a difference between a current (i.e., during an ongoing cooking process) accumulated energy consumption and an accumulated reference energy consumption ("energy difference") . This advantageously increases the accuracy of a weight determination considerably since this energy difference can be equated with the amount of heat absorbed by the load, in particular the food to be cooked, because the thermal effects of the cooking chamber and energy losses from the cooking chamber are taken into account by the reference energy consumption.

The energy or power difference can be calculated, for example, by forming the difference between currently measured energy consumption values and temporally corresponding reference energy consumption values and adding these differences. This corresponds to a determination of a difference in a time course ("curve") of the current energy consumption from the reference curve. A further advantage is that the energy difference typically increases in the course of a cooking process and the ascertained heat absorption, and in particular the weight derived therefrom, can be determined more and more precisely. This advantageously enables an initial rough determination of the determined heat absorption, and in particular of the weight therefrom, which can be refined as the cooking process progresses.

A reference energy consumption can in particular be understood to mean an energy consumption which occurs under predetermined reference conditions, for example when the cooking space is empty, when a container for cooking is loaded or loaded with an empty container cooking chamber, etc. The reference curves correspond to the progress of such energy consumption over time.

There can be one or more reference energy consumption curves or reference curves. If there are several reference curves, these can correspond to heating in the presence of different food containers or cooking vessels, possibly different food storage surfaces (e.g. baking tray, grating, telescopic rails) and/or under different operating parameters (e.g. different target cooking space temperatures), which determine the determined heat absorption, and especially from the weight, further improved.

Some or all of the reference curves can be determined by a manufacturer for certain predetermined cooking containers and can then be selected by a user for similar cooking containers. In a further development, the reference curves are recorded for a specific appliance type of household appliance ("normal appliance type") and then are or are stored on all household appliances of this appliance type. It is an advantageous development for the provision of particularly precisely fitting reference curves that the power of at least one energy supply device for each household appliance is measured precisely during ongoing production, for example in the case of clocked resistance heating elements, the power consumed can be determined device-specifically from the on/off cycle of the switching relay or to be able to determine the amount of energy. A deviation from a preceding “device type normal” can then be determined on an individual device basis. This deviation can be expressed by a device-specific correction factor, which is used to correct the device type normal.

Alternatively or additionally, a user can record reference curves for their own food containers and/or operating parameters they have set themselves, which further improves weight determination.

In the simplest case, these reference curves only need to be carried out once for a specific cooking product container and/or a specific set of operating parameters. However, a user can also record the reference curves again, which then take the place of the previous reference curves. This can be useful, for example, to take into account aging effects of the heat input devices or the like. Al Alternatively or additionally, the household appliance can prompt the user to record the reference curve(s) again. For this purpose, the household appliance can, for example, have an operating hours counter and, after a predetermined operating time of the heat input devices has expired, give the user a suggestion to record the reference curves again.

In one development, a reference curve includes a reference curve for an empty cooking space.

The energy difference can be considered or determined from different points in time of the heating process: a) In one embodiment, which is particularly relevant if no separate preheating phase (in which the cooking chamber is heated up when it is not loaded) is provided, the energy difference can start at the beginning of the cooking process to be determined. This has the advantage that energy inputs into the load can be taken into account particularly easily, which occur during the heating-up phase (in which the cooking chamber is heated to its specified setpoint temperature). This makes use of the fact that the higher the thermal mass of the load, the later the setpoint temperature is reached. By means of this configuration, energy differences in the temporal transition area between the heating-up phase and the following heating phase at the target cooking space temperature ("constant heating phase") can then also be taken into account particularly precisely. Since during the heating-up phase the at least one heat input device - typically independently of the load - is operated with high, in particular maximum, heating power until the target cooking chamber temperature is reached, the energy difference until the target cooking chamber temperature of the reference curve is reached will be at least approximately zero. However, the energy difference will already be noticeably different from zero in the period of time between reaching the target cooking chamber temperature in the reference configuration and reaching the target cooking chamber temperature in the current configuration with food to be cooked, since once the target cooking chamber temperature has been reached in the reference configuration, the energy consumption at the at least one heat input device is lowered to a level sufficient to maintain the target cooking cavity temperature. A further advantage of this configuration is that this point in time can be determined in a particularly simple manner and, in particular, does not have to be calculated in a complex manner. b) In one embodiment, which is particularly relevant if no separate preheating phase (in which the cooking chamber is heated up when it is not loaded) is provided, the energy difference can be determined at the start of a constant heating phase. The start of the constant heating phase can be determined by the target temperature being reached and/or the energy consumption of the at least one heat input device being noticeably lower or reduced compared to the energy consumption during the heating phase. The fact that the energy consumption is noticeably lower can be determined, for example, by the fact that at least one energy consumption sensor is present, which measures the energy consumed by the at least one heat introduction device, when the heat introduction device is operated in a clocked manner, a duty cycle of the energy or power introduced into the heat introduction device drops noticeably, in particular is noticeably lower than a, often maximum, duty cycle typically used during a warm-up phase; and/or to determine a point in time of greatest curvature in an energy consumption curve and to use this point in time as the starting point for determining the energy difference.

The use of an energy consumption sensor generally results in the advantage that the energy consumption can be determined particularly precisely by direct measurement. Disturbances with potentially negative effects on the accuracy of the energy consumption determination, such as aging effects of the heat input device, mains voltage fluctuations, etc. can be excluded or compensated for in this way. The energy consumption sensor can be designed, for example, as a shunt resistor or inductive current sensor, from which, with an associated voltage measurement, an electrical energy or power P fed into a heat input device can be calculated, for example simply via P=U·I.

The duty cycle is also a sufficiently reliable measure of the energy consumption, since the energy fed into a heat input device typically has a constant pulse height of the supply voltage and the duty cycle or, analogously, the switch-on time can therefore be directly converted into the consumed electrical energy is. When using the duty cycle, an energy consumption sensor can be dispensed with, which saves components and thus costs. Consequently, one possibility is to determine when the constant heating phase has been reached from a setpoint cooking chamber temperature being reached or from a reduction in a duty cycle of at least one heat introduction device operated in a clocked manner. A correction factor can be used to correct the above-mentioned disturbance variables and their influence on the accuracy.

In one configuration, the achievement of the constant heating phase is determined from a curvature of the currently recorded energy consumption curve, in particular from the point in time of the greatest curvature of the energy consumption curve. In this case, use is made of the fact that in a cooking process the energy consumption curve runs linearly during the heating-up phase and then runs in a curved manner at the start of or with the transition to the constant heating phase. The curvature steadily decreases as the heating time increases, since the load is heated more and more. If the change in gradient remains below a certain threshold value (e.g. 10% of the maximum value determined so far), the energy or power supplied to the cooking appliance can be assumed to be approximately constant: stability has been reached and the heat capacity of the food to be cooked (as well as the cooking chamber or cooking appliance ) is saturated. If the food to be cooked can no longer absorb any additional heat or the heat absorption of the food has been greatly reduced, the slope of the current energy consumption curve will match the slope of the reference curve. It can run at least approximately linearly in the steady state. The strongest curvature thus occurs at the transition from the heating phase to the constant heating phase and is therefore a suitable measure for determining the point in time at which the constant heating phase begins. It can be determined particularly reliably by forming the second time derivation of the energy consumption curve or the first derivation of the power consumption, since a peak or minimum forms at the time of the strongest curvature, which can be determined comparatively easily by automatic curve evaluation.

The start of the constant heating phase of the currently measured energy consumption curve or the start of the constant heating phase of the reference energy consumption curve can be used as the start of the constant heating phase. Determining the start of the constant heating phase from the energy consumption generally has the advantage that this is largely independent of brief thermal effects within the cooking chamber.

However, the reaching or beginning of the constant heating phase can in principle also be equated with the point in time at which the target cooking chamber temperature is reached. c) In one embodiment, which is particularly relevant when a separate preheating phase is provided or carried out, the energy difference can be calculated from a point in time when a cooking phase that follows a preheating phase begins. This point in time can be determined, for example, by a door being opened. The spread between the current energy consumption curve and the reference curve, which is dependent on the thermal load of the load, is significant here particularly quickly, and accordingly the accuracy of the energy quantity or weight determination. In one configuration, the energy difference is corrected by means of a correction value that takes account of the door opening, which further increases the accuracy of the energy quantity or weight determination. The correction value can be a multiplicative correction factor or an additive correction value. In particular, the additive correction value can be subtracted from the measured energy consumption when a door is opened. The size of the correction value can be determined, for example, as a function of the cooking chamber temperature, a difference in the cooking chamber temperature immediately before and after the door is opened, a humidity in the cooking chamber and/or a difference in the humidity in the cooking chamber immediately before and after the door is opened, etc., e.g. based on corresponding characteristics.

In all the cases described, the energy consumption can be determined by means of an energy consumption sensor or, in the case of heat input devices operated in a clocked manner, from their switch-on times.

In one configuration, the cooking appliance, in particular the data processing device, is set up to determine whether the load is thawed and to take into account the amount of heat absorbed only after the end of a thawing process. Therefore, only the energy consumption after thawing should be taken into account when determining the amount of energy or weight (advantageously with a (further) additive correction value, which in particular depends on the measured energy consumption consumption is deducted, since the cooking chamber is already being heated through). This enables a particularly reliable determination of the amount of energy or weight even when the food to be cooked is initially frozen. In this configuration, use is made of the fact that frozen food to be cooked or stored usually has frozen water, for the melting and evaporation of which a great deal of thermal energy is required, which must not be added to the heat capacity of the food to be cooked. The presence of a frozen state can be detected, for example, by means of an IR sensor (eg, a thermal camera) that senses the load. If there is no such temperature information, it can nevertheless be recognized from an initially unusually flat course of the temperature curve of the cooking chamber temperature with a subsequent transition to a significantly greater gradient that the food to be cooked was evidently frozen. A consequence of being in a frozen state may include a time or temperature adjustment for further cooking. In addition, a message can be issued to the user, which could improve his user behavior in the future.

In one configuration, the cooking appliance, in particular the data processing device, is set up to additionally calculate the weight based on a type of load. This further increases the accuracy and reliability of the weight determination. This configuration can be implemented, for example, by using a more precise specific heat capacity c _w to determine the weight m from the thermal energy Q absorbed if the type of food to be cooked is known. The type of food can be a relatively coarse food category, such as "meat", "fish", vegetables", etc., a finer food category, such as "Schnitzel", "Geschnetzeltes", etc., or even more precisely a dish, such as "Pizza", "Potato casserole", etc. The corresponding specific heat capacities and/or the functions f and/or f can be stored in a database which can be called up.The functions f and/or f can alternatively be recalculated for each cooking process.

In order to determine or specify the type of food to be cooked, it is possible for this to be entered by a user and/or determined automatically, e.g. by evaluating an object using an image recorded by a camera.

In one configuration, the cooking appliance, in particular the data processing device, is set up to additionally calculate the weight based on a volume or a To calculate the size and/or shape of the load. This further increases the accuracy and reliability of the weight determination. This exploits the knowledge that, for example, for large items to be cooked with a rather spherical shape, the weight is usually calculated too low without taking the shape into account, and for light items to be cooked in a flat, spread-out shape, the weight is usually calculated too high without taking the shape into account. The volume and/or the shape can be determined, for example, by object evaluation using an image recorded by a camera, contour detection with a laser or ultrasound.

In one embodiment, in the course of the cooking process, the weight is determined several times in succession and the cooking process is adapted to the weight determined last to determine the weight. In this case, use is made of the fact that the weight of the item to be treated can generally be determined more precisely as the cooking process or course of cooking progresses. The present method for determining the weight thus enables, in particular, a rapid rough determination of the weight, which can be refined during the course of the cooking process.

In particular, operating parameters of the cooking appliance, such as the target cooking chamber temperature, the end of a cooking time, etc., can be adjusted. This is particularly advantageous when the cooking process takes place as part of an automatic or cooking program.

In addition to the weight, the cooking process can also be adjusted based on one or more of the following input variables and/or the end of the cooking time can be determined more precisely:

degree of browning of the food,

Surface temperature of the food (e.g. can be determined using an IR sensor), core temperature of the food (e.g. can be determined using a core temperature probe), humidity of the cooking compartment and/or the food, etc.

For example, cooking devices that can have a moisture sensor can also use the measured values to determine the end of the cooking time more precisely, since the moisture has an influence on the cooking speed. With the help of the moisture value the cooking time can be extended or shortened via stored correction values in order to achieve better cooking results.

The object is also achieved by a method for operating a household cooking appliance, in which the amount of heat absorbed by a load being treated in a cooking chamber using thermal energy is calculated based on the energy consumption of at least one heat input device, and a cooking process is controlled based on the calculated amount of heat absorbed. The method can be designed analogously to the cooking appliance and vice versa, and results in the same advantages.

For example, a cooking process can be controlled or adjusted based on the weight of the load derived from the amount of heat absorbed.

In one development, a user can also record their own reference energy consumption curve, for example as follows:

The user places an empty food container on a food storage surface (eg a grating or a baking tray) and starts a reference program that is specially provided for this purpose and possibly operating mode-specific for this load status. Within the framework of this reference program, the cooking appliance heats up to a specified target cooking chamber temperature and then continues to operate until the flow of energy into the cooking chamber is constant. The cooking chamber is then in a state of equilibrium with regard to the energy absorbed from the heating elements and the energy flowing away via the walls of the cooking chamber and, if present, a vapor outlet. The curve of energy consumption recorded over time represents the reference curve for this loading condition. The user saves the reference curve in the device for this loading condition and can use it later. Optionally, the associated temperature profile can also be saved. This process is only carried out once and is related to the load status and the set cooking cabinet temperature. The reference program can be run again for different loading states (eg for different desired cooking space temperatures and/or different cooking product containers). Alternatively (but less precisely tunable to the user's specific cooking vessels), at least some of the reference curves can be determined by the manufacturer for common cooking vessels and can be selected by the customer to suit their cooking vessels.

The weight of food to be cooked can be determined during a cooking process, for example, as follows, assuming that at least one energy consumption reference curve is available:

In the event that the food to be cooked is placed in the cooking compartment and the cooking operation is only then started, i.e. separate preheating without food to be cooked is not carried out:

The food to be cooked is placed in the cooking chamber and the cooking appliance is then started with a specified setpoint temperature for the food to be cooked.

From the start of the cooking process, the energy consumption of the at least one heat input device is recorded and stored as the current energy consumption curve.

The gradient of the energy consumption curve accumulated over time is continuously determined. During the heating-up phase, the at least one heat input device is typically fed with full energy or power, resulting in a linear progression of the energy consumption curve. When the heating-up phase is completed when the setpoint cooking chamber temperature is reached, the energy or power introduced into the at least one heat input device is reduced in order to keep the setpoint cooking chamber temperature within the scope of a constant heating phase. This causes a curvature of the energy consumption curve, which then flattens out steadily at first, the curvature being greatest at the transition to the constant heating phase. If the change in the slope of the accumulated energy consumption curve remains below a certain threshold value (e.g. 10% of the maximum value determined so far), the power flow supplied to the cooking appliance can be assumed to be approximately constant, persistence is achieved and the heat capacity of the food to be cooked is saturated. Since the food in the steady state can no longer absorb any additional heat or the heat absorption of the food may even be reduced. device, the slope of the currently recorded energy absorption curve will match the slope of the reference curve.

The second derivative (i.e. the rate of change of its slope) is determined from the currently recorded energy consumption curve and monitored for the occurrence of a negative peak or a minimum peak. The point in time at which this peak occurs corresponds to the point in time at which the transition to the constant heating phase takes place. The formation of the second derivation of the energy consumption curve results in a point in time of the transition to the constant heating phase that can be determined more precisely than the determination of the slope (ie the first derivation of the energy consumption curve). Determining the transition to the constant heating phase from the energy consumption curve is more precise than determining using the cooking chamber temperature, since overshoots and other thermal disruptive effects are suppressed or not taken into account.

The difference between the currently recorded energy consumption and the reference energy consumption is then calculated from the time of the transition to the constant heating phase previously determined from the curve evaluation and the weight of the food is calculated from this.

At the beginning of the energy difference calculation, the weight can still be determined comparatively imprecisely, but this is already sufficient to provide a rough estimate sufficient for adapting the cooking process to the weight. As the cooking process continues, the weight can be determined more precisely and the cooking process can be better adapted to the weight of the food to be cooked.

In the event that the cooking chamber is preheated and the food to be cooked is only placed in the cooking chamber after the preheating phase, the energy difference can be calculated immediately after closing the cooking chamber door or - to rule out thermal effects due to heat loss when the door is open - after a predetermined time delay . For example, in the first case, a compensatory reaction to the opening of the cooking chamber door during operation can be achieved by determining the opening time and subtracting a correction value from the measured energy consumption. The correction value can be determined in the laboratory for each type of basic device and differs depending on the cooking situation (e.g. in which cooking phase the door was opened, whether the escaping, warm air already has a high or low moisture content, etc.).

The characteristics, features and advantages of this invention described above, and the manner in which they are achieved, will become clearer and more clearly understood in connection with the following schematic description of an exemplary embodiment, which will be explained in more detail in connection with the drawings.

1 shows a plot of an accumulated energy of a cooking process without preheating for a cooking chamber loaded with food and for reference conditions over time;

FIG. 2 shows a plot of the pulse duty factor of the switch-on times of the heat input device for the cooking process from FIG. 1 for the cooking chamber loaded with food and for reference conditions over the same time axis as in FIG. 1; and

FIG. 3 shows a plot of a cooking chamber temperature of the cooking process from FIG. 1a for the cooking chamber loaded with food over the same time axis as in FIG.

The description of the following figures is based on an example of an oven (not illustrated) with a cooking chamber that can be closed by a door, which is heated by one or more heat input devices in the form of clocked resistance heating elements (e.g. a bottom heating element, a top heating element, a grill heating element and a ring heating element ) can be heated. The oven also has a temperature sensor for detecting a cooking chamber temperature. The resistance heaters are controlled by a control device of the oven, taking into account the cooking chamber temperature. The control device is set up to run automatic programs that are selected by a user at a corresponding user interface. The control device is also set up as a data processing device for carrying out a weight determination.

To carry out the weight determination, the control device is specially set up to record user-specific reference curves of accumulated energy consumption men. To do this, a user can call up a corresponding routine on the user interface, which can be configured, for example, in such a way that a user is instructed to place a specific food container in the cooking chamber, to select a target cooking chamber temperature and a specific operating mode (e.g. hot air mode, grill mode, top/bottom heat mode, etc.). The oven then heats the initially cold cooking chamber to the target cooking chamber temperature and, based on the switch-on times of the resistance heaters, registers their energy consumption, possibly taking into account a correction factor. The energy consumption reference curve recorded for a reference condition is stored together with the associated setting variables and possibly together with the curve of the cooking chamber temperature.

1 shows a plot of an accumulated energy Ea of a cooking process without preheating for a cooking chamber loaded with food, Ea_a, and for reference conditions, Ea_r, over time t, based on a corresponding curve Ka for the current cooking process and a reference curve Kr. The conditions of the current cooking process differ from the reference conditions, for example, only in that there is additional food to be cooked in the cooking chamber of the oven during the current cooking process, e.g. in the food container also used for the reference conditions.

During an initial heating phase, beginning at tO, of both the current cooking process and the heating under reference conditions, the resistance heaters corresponding to the selected operating mode are operated at high, in particular maximum, power until the target or desired cooking chamber temperature T _S0 u (see Fig. 3) is reached. The curves Ka and Kr therefore initially do not differ. However, the food to be cooked represents a thermal load or heat sink, which means that in the current cooking process or with the food to be cooked, the target cooking chamber temperature at t1a is reached later than under reference conditions at t1r.

If the target cooking chamber temperature T _S0 u is reached, the heating phase changes to a constant heating phase in which the duty cycle of the resistance heaters is reduced to a level that is sufficient to maintain the target cooking chamber temperature T _S0 u . Fig. 2 shows the associated duty cycles as a plot of an operating voltage applied to a selected resistance heating element versus time, with it being reduced later when food is present (upper timing diagram) than in the reference state (lower res timing diagram). Based on the reduction in the duty cycle, it can therefore be determined when the setpoint cooking chamber temperature T _S0 u has been reached, more precisely than based on a temperature curve.

3 shows the temperature curve Ta of the cooking chamber temperature T _g as an example for the cooking chamber loaded with food to be cooked. The temperature curve for the reference state (not shown) is qualitatively similar, although the target cooking chamber temperature T _S0 u is reached earlier. Otherwise, the temperature curves differ little since they are regulated to the same desired cooking chamber temperature Tsoii.

When the desired cooking chamber temperature T _S0 u is reached and thus the constant heating phase, a noticeable temperature overshoot occurs, from which point the cooking chamber temperature Tg approaches the desired cooking chamber temperature T _S0 u . Not shown, but typically present, is a ripple in the temperature curve Ta during the constant heating phase t>t1a, which results from the temperature regulation carried out by the control unit.

Returning to FIG. 1, both the curve Ka and the reference curve Kr flatten out when the setpoint cooking chamber temperature T _S0 u is reached, due to the then lower energy input. The curve Ka for the cooking chamber loaded with food to be cooked initially falls less sharply than the reference curve Kr, since the food to be cooked is still absorbing thermal energy. If the food to be cooked is warmed through in the further course of the cooking process (indicated here by time t2a), the gradients of curves Ka and Kr equalize. The (accumulated) energy difference AE between the curves Ka and Kr thus corresponds to the heat energy Q absorbed by the food to be cooked. The energy difference AE at a specific point in time t corresponds to the difference between the curves Ka and Kr at this point in time t).

In one variant, the energy difference AE can be calculated from the time t1a from the switch-on times of the resistance heaters. The point in time t1a can be precisely determined by means of a determination of a negative peak or minimum in the second derivative of the curve Ka. The weight m of the food to be cooked can be calculated from the energy difference AE, for example according to m=(1/c _w )·f(T _so ii, ■■■)·AE.

Initially, the weight can usually be at least roughly estimated from the energy difference AE. As a result, the accuracy of the weight calculation gets better and better, until the food to be cooked has been heated through and thus reached a steady state at t > t2a and the time course of the energy difference AE is approximately constant from then on.

The cooking process can be adjusted on the basis of the weight calculated from the energy difference AE, e.g. by varying the associated operating parameters, for example by reducing or increasing the target cooking chamber temperature T _S0 u , switching on or off resistance heating elements, a fan, adding microwave energy and/or steam, etc.

The initially only rough knowledge of the weight is typically not critical, since food initially cooks very little and it is therefore not yet decisive whether e.g. during the first twenty minutes (of which a large part usually falls into the heating-up phase) the exact suitable cooking space temperature Tg for a specific weight is set. Only after some time (usually only after about half of the total cooking time) does it become more and more important for a good result what cooking chamber temperature Tg prevails in the cooking chamber and/or whether the most suitable process technology is used for the cooking process at hand, e.g "Right" combination of heating elements such as top and bottom heat, or the right amount of microwave, etc. One rule can therefore be: cook with initially specified process settings until the first rough estimate of the weight is available, then adjust the operating parameters if necessary and subsequently carry out more and more precise process control as the weight estimation becomes more and more precise. In this way it is possible to pass on an ever more accurate weight estimate to an automatic cooking program or to a user-defined cooking process during the cooking process, so that the cooking process can be better and better adapted to the current cooking situation during operation.

If operating parameters are changed during the cooking process, a different energy consumption reference curve can be used from this point in time, which corresponds better to the changed operating parameters. If, for example, the target cooking space temperature Tsoii is reduced, a reference curve can be used from this point in time to determine the energy difference, which corresponds to the reduced target cooking space temperature Tsoii, if necessary using a correction factor that takes into account the thermal inertia of the cooking space and, if applicable, the food container . As already described above, the weight can be calculated from the energy difference, for example by assuming a proportional relationship, possibly using proportionality factors that take into account the type, volume and/or shape of the food to be cooked.

Of course, the present invention is not limited to the embodiment shown.

A step can also be provided for calculating the energy difference only once a previously frozen item to be cooked is in a thawed state. In addition, the type, volume and/or shape of the food to be cooked can be determined automatically and used to adjust the proportionality factor.

In general, "a", "an" etc. can be understood as a singular or a plural number, in particular in the sense of "at least one" or "one or more" etc., as long as this is not explicitly excluded, e.g. by the expression "exactly a" etc.

A numerical specification can also include exactly the specified number as well as a usual tolerance range, as long as this is not explicitly excluded.

reference list

Ea Accumulated energy consumption

Ea_a Accumulated energy consumption with food to be cooked Ea_r Accumulated energy consumption under reference conditions

Ka Energy consumption curve of the current cooking process

Kr Energy consumption reference curve

Tg cooking chamber temperature

Tset Target cooking chamber temperature t Time tO Beginning of the cooking process t1a Beginning of a constant heating phase of the cooking process currently being carried out t1r Beginning of a constant heating phase under reference conditions t2a Achievement of thorough heating within the constant heating phase of the currently carried out cooking process

voltage

Claims

24

PATENT CLAIMS Household cooking appliance, having a cooking chamber and at least one heat input device for introducing thermal energy into the cooking chamber and a data processing device which is set up to calculate an amount of heat absorbed by a load treated in the cooking chamber by means of the thermal energy on the basis of an energy consumption (Ea, Ea_a, Ea_r) of to calculate at least one heat input device, wherein the household cooking appliance is set up to control a cooking process based on the amount of heat absorbed. Domestic cooking appliance according to claim 1, wherein the data processing device is set up to determine a weight of the load based on the amount of heat absorbed and the domestic cooking appliance is set up to control a cooking process based on the determined weight. Domestic cooking appliance according to claim 2, wherein the weight, m, at least with knowledge of the amount of heat absorbed, Q, and the set cooking chamber target temperature, Tsoii, from m = f (Q, Tsoii, ...), with f an experimental and / or numerically determined function, from m = f (Tsoii, ...) ■ Q with a function f independent of the quantity of heat, Q, or from m = (1 / C _w ) • f" (Tsoii, ...) ■ Q, is calculated with a function f" that is independent of the amount of heat, Q, and that of the assumed specific heat capacity of the load, c _w .

4. Domestic cooking appliance according to one of the preceding claims, wherein the data processing device is set up to calculate the amount of heat absorbed based on an accumulated energy consumption (Ea, Ea_a, Ea_r).

5. Domestic cooking appliance according to claim 4, wherein the data processing device is set up to calculate the amount of heat absorbed using a difference between a currently accumulated energy consumption (Ea_a) and an accumulated reference energy consumption (Ea_r).

6. Domestic cooking appliance according to claim 5, wherein the cooking appliance, in particular the data processing device, is set up to calculate the difference for a cooking process without a preheating phase from a point in time (t1a; t1r) of reaching a constant heating phase following a heating phase.

7. Domestic cooking appliance according to claim 6, wherein the data processing device is set up to determine when the constant heating phase has been reached from a curvature of a currently recorded energy consumption curve (Ka).

8. Domestic cooking appliance according to one of claims 1 to 5, wherein the data processing device is set up to determine when the constant heating phase has been reached from a desired cooking chamber temperature (T _S0 n) being reached or from a reduction in a duty cycle of at least one clocked heat input device.

9. Domestic cooking appliance according to one of claims 1 to 5, wherein the data processing device is set up to calculate the difference from the start of a cooking phase following a preheating phase and wherein the difference is corrected using a correction value taking into account the door opening.

10. Domestic cooking appliance according to one of the preceding claims, wherein the data processing device is set up to determine the energy consumption (Ea, Ea_a, Ea_r) from switch-on times of the at least one heat input device. Domestic cooking appliance according to one of the preceding claims, wherein the data processing device is set up to determine a thawed state of a previously frozen load placed in the cooking chamber and to determine the amount of heat absorbed (Ea, Ea_a, Ea_r) only after the end of a thawing process. Domestic cooking appliance according to one of claims 2 to 11, wherein the data processing device is set up to additionally calculate the weight based on a type, a shape and/or a volume of the load. Domestic cooking appliance according to one of the preceding claims, in which the at least one heat input device comprises at least one heat radiator and/or at least one steam generator. Domestic cooking appliance according to one of the preceding claims, in which the domestic cooking appliance is set up to adapt a cooking process on the basis of the calculated amount of heat absorbed, the amount of heat absorbed being determined several times in succession over the course of the cooking process and the cooking process being adapted to the last determined amount of heat absorbed. A method for operating a domestic cooking appliance, in which the amount of heat absorbed by a load treated in a cooking chamber using thermal energy is calculated based on an energy consumption (Ea, Ea_a, Ea_r) of at least one heat input device, and a cooking process is controlled based on the calculated amount of heat absorbed.