EP2570732B1 - Method for cooking a food product in a cooking oven - Google Patents

Description

The invention relates to a method for cooking food in a cooking appliance which has a heater and a fan that can be operated at intervals.

Such a procedure is from the DE 10 2010 012 368 A1 known. In order to save energy, the fan is always switched off there when a hot air heater provided for heating the cooking space is switched off. However, the method disclosed in this publication is not variable, since a fixed cycle ratio, that is to say a fixed ratio of operating to standstill phases of the fan, is provided.

From the DE 43 19 613 C1 a method is known in which a fan switches between two operating modes with an active fan, depending on the cooking space temperature, a circulating air mode and a top and bottom heating mode.

In the DE 10 2009 024 546 A1 a method is shown which comprises an energy-saving mode in which a fan can be switched to a standstill phase and the standby temperature is still maintained in the cooking chamber.

DE 10 2008 040 981 A1 describes a method in which a fan actively flows cold air against a temperature sensor so that it measures a lower temperature than the actual temperature in the cooking space.

From the DE 26 21 927 a method for cooking food is known in which a circulating air fan is switched on and off as a function of fixed, predetermined temperature threshold values.

In the EP 2 287 533 A1 describes a method for operating a cooking appliance, in which a cooling fan is controlled which is assigned to a control unit, the control taking place via a temperature sensor provided in an installation space.

The DE 20 2004 015 290 U1 describes a method and a device in which the energy input into a food to be cooked is to take place uniformly by applying a stream of air evenly to the food.

The object of the invention is to develop the cooking method in such a way that a better, reproducible quality of the cooked food is achieved.

To achieve this object, the invention provides for a method of the type mentioned at the outset that the ratio of operating to standstill phases of the fan (cycle ratio) is varied as a function of the heat consumption in the cooking chamber of the cooking appliance. This enables the cycle ratio to be optimally adapted to different foods and different cooking programs, the cycle ratio depending on the cooking program, and the core temperature of a product to be cooked being monitored and the proportion of standstill phases being increased when the difference between the actual core temperature and either the target core temperature or the cooking space temperature and / or the shaft temperature of a temperature sensor and / or the cooking space target temperature falls below a predetermined threshold.

In the case of a drying program for almonds, for example, depending on the cooking program, a cycle ratio with long standstill phases of the fan can be used to ensure a calm cooking space climate. The standstill phases are only interrupted by short operating phases of the fan, which ensure a minimum air circulation so that sufficient energy input into the tonsils is ensured.

In a cooking program that provides for longer holding phases, a cycle ratio with longer standstill phases can also be used. This ensures that the food does not dry out.

Falling below the predetermined threshold indicates that the core temperature of the product to be cooked is approaching the target value, so that the proportion of phases during which energy is supplied to the cooking chamber can be reduced.

The clock ratio therefore depends on the temperature. For example, longer standstill phases can be used at cooking temperatures below 100 ° C, such as those used for drying food. At temperatures above 240 ° C, on the other hand, either short standstill phases or no standstill phases at all are used, since in these temperature ranges there is a maximum energy input into the food to be cooked arrives, for which the air circulation is advantageous.

For example, the proportion of standstill phases increases when the oven temperature rises. An increase in the cooking space temperature indicates that a sufficient amount of energy is currently being introduced into the cooking space. This allows the fan to be switched off temporarily.

It is preferably provided that the proportion of standstill phases is first doubled, then the course of the cooking space temperature is evaluated over a certain time and then the proportion of standstill phases is doubled again if the cooking space temperature continues to rise. With such a control strategy, the cycle ratio can be adapted very quickly to the respective requirements by extending the standstill phases in very large steps until the desired influence on the cooking space temperature is achieved.

The cycle ratio can depend on the derivative of the measured temperature with respect to time, i.e. on the slope of the temperature curve. This allows additional parameters to be used to adapt the currently used cooking program to the requirements. For example, if the slope of the temperature curve is low and at the same time the measured temperature, for example the core temperature, is still a long way from the setpoint, the proportion of standstill phases can be reduced so that the cooking process does not take too long.

If the temperature is measured on the shaft of a core temperature probe and the slope of the temperature curve has negative values, the proportion of standstill phases can be reduced. In this case, negative values of the derivative of the temperature with respect to time mean that the cooking product transfers temperature to the cooking space.

According to one embodiment it is provided that the cycle ratio depends on the loading of the cooking appliance. A high load of the cooking device leads to a high heat consumption in the cooking device, so that in principle a lower proportion of standstill phases makes sense.

It can be provided that when the cooking appliance is loaded above an upper threshold value, the proportion of standstill phases is reduced, in particular halved. This results in an approximately adapted starting value for the cycle ratio, which can, however, be further individually adapted depending on further parameters, for example the course of the cooking temperature. The same applies when the cooking appliance is loaded below a lower threshold value; then the proportion of standstill phases is increased, in particular quadrupled.

It can also be provided that the cycle ratio depends on the caliber of the products to be cooked in the cooking space. It can thus be provided that a higher proportion of standstill phases is used in the case of large calibres, for example by quadrupling the pause times.

To determine the caliber, it can be provided that the course of the core temperature is evaluated over time. This can be integrated into intelligent cooking programs with little effort.

The size of the products to be cooked can be taken into account to the effect that a larger proportion of standstill phases is used if the size is above a predetermined threshold.

The core temperature is preferably also taken into account to the effect that the caliber-dependent extension of the standstill phases is only permitted when the core temperature has already risen. Otherwise the cooking process would take too long.

It is preferably provided that the heat consumption in the cooking space is determined on the basis of the temperature profile during a standstill phase of the fan. In this way, disruptive factors, such as the energy input from the fan, are eliminated.

Provision is preferably made here for the proportion of standstill phases to be reduced in the event of a heat consumption that is above a predetermined threshold. A higher proportion of operating phases of the fan ensures that a lot of energy can be supplied to the cooking space, so that the large heat consumption in the cooking space is compensated for.

According to one embodiment, it is provided that it is determined how much energy has to be supplied to the cooking chamber until a target temperature is reached again, and that the proportion of standstill phases is subsequently reduced if the required energy was above a predetermined threshold. This also makes it possible to adapt the cycle ratio to the heat consumption in the cooking chamber with little effort and in this way to achieve a high, reproducible quality of the cooked products.

According to one embodiment of the invention, it is provided that the gradient of the course of the core temperature of a product to be cooked is monitored and the proportion of standstill phases is reduced if the gradient is below a predetermined threshold at a predetermined distance between the actual core temperature and the target core temperature lies. With this constellation, the fan is operated more frequently in order to counteract an undesirable increase in the total cooking time.

According to one embodiment of the invention, an energy-saving button is provided on the cooking appliance, the proportion of standstill phases being increased, in particular doubled, when the energy-saving button has been pressed. This enables an operator to influence the currently used cooking process in such a way that the focus is placed on saving energy, while in return an extension of the cooking time is tolerated.

It can also be provided that a low-noise operating phase can be selected by the operator, in which case the proportion of standstill phases is increased. In this way, if the operating noises generated by the cooking appliance are perceived as annoying by the operator, a quieter operating mode can be set temporarily.

According to one embodiment of the invention, it is provided that the proportion of standstill phases is reduced when the temperature in the electrical installation space of the cooking appliance is above a predetermined threshold. This ensures that a high proportion of standstill phases of the fan, which are desirable for the current cooking program, do not lead to a build-up of heat in the electrical installation space of the cooking appliance.

According to one embodiment of the invention it is provided that the fan can be operated with alternating directions of rotation and that standstill phases be adjusted by changing the direction of rotation. This prevents the fan from starting again after a standstill phase and shortly afterwards, since the direction of rotation is reversed, first decelerates and then starts again in the opposite direction. Instead, in such a case, the fan would be put into operation immediately in the new direction of rotation.

According to one embodiment of the invention, two or more temperature sensors are evaluated and the standstill phases are shortened or canceled if the difference between the temperatures recorded by the two temperature sensors, in particular the shaft temperature and cooking chamber temperature, exceeds a threshold value. If the threshold value is exceeded, this indicates an uneven temperature distribution in the cooking space, which is counteracted by longer operating phases of the fan.

The invention is described below with reference to an exemplary embodiment, which is shown in the accompanying single drawing.

In general terms, it is provided in the method according to the invention that the cycle ratio of the fan, that is to say the ratio of operating to standstill phases, can be variably adapted to the respective requirements. The main parameter that determines the cycle ratio selected in each case is the heat consumption in the cooking space, i.e. the amount of heat generated by the food in the cooking space, the accessories in the cooking space and the boundaries of the cooking space (i.e. side walls, floor, ceiling and door) is recorded. In other words, the heat consumption in the cooking space corresponds to the amount of energy that must be supplied to the cooking space in order to maintain a constant temperature in the cooking space. Other parameters that influence the cycle ratio are the cooking space temperature, the food to be cooked, the cooking program and various temperature profiles.

The cycle ratio can basically be set freely. Examples are a switch-on time of 25 seconds and a switch-off time of 360 seconds or a switch-on time of 15 seconds and a switch-off time of 1,000 seconds. In addition, the speed of the fan can be varied during the operating phase, either continuously or in predefined steps. The respective cycle ratio can be stored in the control of the cooking appliance and, if necessary, integrated into a cooking program or a cooking process.

The particular advantage of an automatically adapting cycle ratio becomes clear when one considers the effects of different feed quantities. Surprisingly, it was found that it is advantageous to use a larger proportion of standstill phases in the cycle ratio with small amounts of feed. This not only reduces energy consumption, since the drive motor of the fan is operated less often, but it also reduces heat losses on the cooking chamber walls and the door. With maximum loading, however, the proportion of standstill phases should be reduced, as otherwise the temperature in the cooking space can be stratified, which leads to uneven cooking (the food placed at the top receive more energy).

The load can be identified using existing load detections (for example, due to the temperature drop after loading, based on the gradient of the rise in temperature after loading or through weight measurement, customer input or other data input such as barcode scanning, moisture development in the cooking chamber, energy consumption and / or energy consumption).

For example, half a load in the cooking space can be regarded as the standard value. A high load then leads, for example, to halving the standstill phases of the fan, while a low load leads to a quadrupling of the standstill phases of the fan. Specifically, this can mean that with a low load, an operating phase of 10 seconds is followed by a standstill phase of 440 seconds.

Another parameter that has an influence on the cycle ratio is the type of food to be cooked. If, for example, almonds are roasted or damp fruit slices, e.g. apple rings or orange slices, are dried, a small amount of standstill phases is preferably used at the beginning of the drying process to remove the moisture from the food surface so that the moisture can flow in from the inside and then also is discharged. In order to quickly remove the high humidity that is present at the beginning of a drying process, the fan is best running continuously. If, on the other hand, the drying process has progressed further, the limiting parameter of the drying speed is the moisture flow from the inside of the food. Therefore, in this phase the fan is reduced or clocked, i.e. with a high one Proportion of standstill phases in order to maintain a calm cooking space climate. Only a small minimum number of operating phases of the fan is used, which ensures sufficient energy transfer, but prevents overdrying of the food surface, which could lead to a porous structure.

Another parameter that influences the cycle ratio is the type of cooking. For example, when cooking at low temperatures, less air circulation is desired, i.e. a higher proportion of fan standstill phases in order to prevent the surface of the food from drying out. In drying processes, it is also not necessary to permanently maintain a flow of air on the surface of the product to be dried, since the removal of moisture on the surface is limited by the transport of water inside the cooking appliance, at least in an advanced drying phase. If a high air flow were to force a high level of moisture away from the surface, this would lead to a brittle end product. Even with weight-saving cooking, it is desirable that the product to be cooked does not dry out. A high proportion of standstill phases of the fan is advantageous here, so as not to disturb the microclimate around the food to be cooked.

It is preferably provided that the user can save the cycle ratios that he has tested and found to be good and can incorporate them into the cooking programs or processes, specifically for each cooking program step.

The cooking program currently in use also has an impact on the appropriate cycle ratio. If, for example, steaming is carried out, a small proportion of the fan standstill phases is used, since otherwise no steam mixing is guaranteed in the cooking space. In the searing and crusting phases of a cooking program, on the other hand, brief stoppage phases of the fan are advisable at best in order to ensure maximum energy input into the product to be cooked. During the holding phases of a cooking program, however, long standstill phases can be interposed without this having a negative effect on the quality of the products to be cooked. In a cleaning program, standstill phases can be used if excessive foaming is detected.

In principle, the cycle ratio used in each case is not linked to the switching on and off of the heating of the cooking appliance. In other words, there are none forced coupling to the effect that the fan must also be switched on when the heating is switched on, or that the heating must also be operated when the fan is switched on.

The attached figure shows how the cycle of the fan changes as a function of the heat consumption in the cooking space. The operation of the fan is plotted in the lower part of the diagram, it being assumed here for the sake of simplicity that the fan is operated at constant speed. The status thus changes between an operating phase (the curve has the value "1") and a standstill phase (the curve has the value "0"). The cooking space temperature T is used here as a specific parameter that correlates with the heat consumption in the cooking space. During a first standstill phase of the fan, the temperature in the cooking chamber drops from temperature level T ₁ to temperature T ₂ . The difference between these two temperatures is recognized as being above a predefined threshold. Thereupon, in a subsequent operating phase, the cycle ratio is changed in such a way that longer operating phases and shorter standstill phases of the fan are used. After three operating phases of the fan, a longer standstill phase is then inserted again, quasi as a test, in order to check how great the heat loss in the cooking chamber (and thus the temperature drop) is. After the end of the standstill phase, the temperature in the cooking chamber has dropped to a value T ₃ , the difference between the temperatures T ₁ and T _{3 being} below a predetermined threshold. The control of the cooking appliance recognizes from this that a clock ratio with a larger proportion of standstill phases can now be used.

Alternatively, to adjust the cycle ratio, it is also possible to evaluate how much energy is required to reach a target temperature again after a standstill phase. The fan is preferably operated continuously until the target temperature is reached again.

With the method according to the invention, the energy of the resulting moisture can also be determined by measuring the moisture in the cooking space and / or measuring the evaporation rate (heat of evaporation). This moisture comes from the food. The fan is now controlled in such a way that the heat consumption is reduced by the heat of evaporation.

The heat consumption in the cooking space can also be determined using the core temperature. A thermal gradient of the food can be determined by measuring the core temperatures. The smaller the gradient of this thermal gradient, the less energy flows into the food. This means that the heat consumption in the cooking space must be reduced.

It can also be provided that the change or the absolute value of the weight loss during a standstill phase is compared with that of an active phase. The heat consumption is set so that they are identical.

The heat consumption can also be adapted to frozen products. If the device receives the information that there is a frozen product in the cooking space (this has a lower thermal conductivity than a product with an initial temperature above freezing point), the heat consumption is reduced.

Claims (10)

1. A method of cooking a food in a cooking appliance which includes a heater and a fan that can be operated at intervals, characterized in that the ratio between operating phases and standstill phases of the fan (clock ratio) is varied as a function of the decrease in heat in the cooking chamber of the cooking appliance, the clock ratio being dependent on the cooking program, characterized in that the core temperature of a product to be cooked is monitored and the portion of the standstill phases is increased when the difference between the actual core temperature and either the set-point core temperature or the cooking chamber temperature and/or the shank temperature of a temperature sensor and/or the set-point cooking chamber temperature falls below a predetermined threshold.
2. The method according to claim 1, characterized in that longer standstill phases are used in a cooking program that provides a dry cooking.
3. The method according to claim 2, characterized in that longer standstill phases are used in a cooking program that provides long holding phases.
4. The method according to any of the preceding claims, characterized in that the temperature is measured at the shank of a core temperature sensor and the portion of the standstill phases is reduced if the derivative has negative values.
5. The method according to any of the preceding claims, characterized in that it is determined how much energy has to be supplied to the cooking chamber until a set-point temperature is reached again, and in that subsequently the portion of the standstill phases is reduced if the required energy was above a predetermined threshold.
6. The method according to any of the preceding claims, characterized in that the gradient of the profile of the core temperature of a product to be cooked is monitored and the portion of the standstill phases is reduced if the gradient is below a predetermined threshold at a pre-defined distance between the actual core temperature and the set-point core temperature.
7. The method according to any of the preceding claims, characterized in that a power save key is provided and in that the portion of the standstill phases is increased, in particular doubled, when the power save key has been pressed.
8. The method according to any of the preceding claims, characterized in that a low-noise operating phase can be selected and in that the portion of the standstill phases is increased when the low-noise operating phase has been selected.
9. The method according to any of the preceding claims, characterized in that the fan can be operated with alternating directions of rotation and in that standstill phases are coordinated with a change of the direction of rotation.
10. The method according to any of the preceding claims, characterized in that two or more temperature sensors are evaluated and the standstill phases are shortened or discontinued if the difference between the temperatures detected by the two temperature sensors, in particular the shank temperature and the cooking chamber temperature, exceeds a threshold value.

Images