Method for safely operating a combination cooking device and combination cooking device

Abstract

The invention relates to a method for the safe operation of a combination cooking appliance (10) comprising a cooking chamber (14) and a microwave source (26) with a microwave power output. The cooking chamber temperature (14) is measured. A convection-relevant parameter is determined. The measured cooking chamber temperature and the convection-relevant parameter are evaluated to determine a maximum permissible microwave power output. The microwave power output of the microwave source (26) is limited to the maximum permissible microwave power output. Furthermore, a combination cooking appliance (10) is described.

Description

[0001] The invention relates to a method for the safe operation of a combination cooking appliance. Furthermore, the invention relates to a combination cooking appliance.

[0002] Cooking appliances used in professional and large-scale catering typically feature a heating element for generating hot air and a steam generator to produce steam for cooking food placed in the cooking chamber. The heating element and steam generator create a specific cooking atmosphere within the chamber, also known as the cooking chamber climate. Food exposed to this climate is cooked by the convection-based transfer of energy into the food.

[0003] In addition to the heating element and steam generator, such cooking appliances may also include a microwave source, which serves to accelerate the cooking process by introducing (additional) energy in the form of microwaves into the food. Generally, cooking appliances that have a microwave source alongside a heating element and an optional steam generator are also referred to as combination cooking appliances.

[0004] It has been found that when no food is present in the cooking chamber, the microwave radiation introduced into the chamber primarily interacts with the chamber itself, i.e., it couples into components of the cooking appliance that define the cooking chamber, such as the chamber walls or a glass panel in the oven door. However, the microwave radiation can also be partially absorbed by additional components placed in the cooking chamber, such as cooking accessories or a core temperature probe, particularly the cable of a wired core temperature probe.

[0005] Depending on the material and composition of the components, the absorption of microwave radiation fed into the cooking chamber can lead to damage. To prevent such damage, current technology envisions equipping cooking appliances with automatic safety shut-offs. These shut-offs detect when the appliance is running empty, i.e., when the cooking chamber is empty, and automatically switch off the microwave supply.

[0006] For example, DE 10 2004 015 993 A1 discloses a microwave oven which automatically detects idle operation and automatically switches off a microwave-generating device when idle operation of the cooking appliance is detected. US2016 / 283822 A1 discloses a method for the safe operation of a combination cooking appliance according to the preamble of claim 1.

[0007] However, it has been found that even with light or medium loads, wear and tear or damage to components of the microwave oven can occur, even though microwave operation is generally permitted. This wear and tear or damage is undesirable, as the affected components must be replaced prematurely, thus increasing costs.

[0008] Therefore, the object of the present invention is to eliminate the disadvantages of the prior art and to provide a method by which a cooking appliance can be operated safely.

[0009] The object is achieved according to the invention by a method for the safe operation of a combination cooking appliance which has a cooking chamber and a microwave source with a microwave power, wherein the method comprises the following steps: Determining the cooking chamber temperature, identifying a convection-relevant parameter, evaluating the determined cooking chamber temperature and the convection-relevant parameter to determine a maximum permissible microwave power, and limiting the microwave power of the microwave source to the maximum permissible microwave power, in particular to a maximum permissible microwave power for the determined cooking chamber temperature and the identified convection-relevant parameter.

[0010] The invention is based on the fundamental idea that the combination cooking appliance can be operated safely with the microwave source by limiting the microwave power of the microwave source to the maximum permissible microwave power for the determined convection-relevant parameters and the measured cooking chamber temperature.

[0011] The maximum permissible microwave power can therefore be lower than the theoretically possible microwave power (nominal power of the microwave source). The actual maximum permissible microwave power thus depends on the measured cooking chamber temperature and the determined convection-relevant parameter. In other words, the maximum permissible microwave power is predetermined by the control system, namely as a function of the measured cooking chamber temperature and the determined convection-relevant parameter. The maximum permissible microwave power is therefore variable, especially during the cooking process, since the cooking chamber temperature and / or the convection-relevant parameter change during the cooking process.

[0012] This allows the energy fed into the cooking chamber in the form of microwaves to be limited, thus reducing the amount of microwave energy that can interact with the components of the combination cooking appliance and effectively preventing damage to the components due to the microwaves.

[0013] It was found that microwave energy could couple into components of the combination oven located within or bordering the cooking chamber, causing these components to heat up. This led to increased wear and tear or even damage to the components, which is now effectively prevented, thus ensuring reliable and safe operation of the combination oven. The components located within the cooking chamber include, in particular, wired core temperature probes, which should not exceed a certain temperature.

[0014] If convection occurs around a component, meaning there is a flow of air around it, this can cool the component, thus reducing its heat buildup. Strong convection allows for greater thermal energy dissipation compared to weak convection. Therefore, if more thermal energy can be dissipated (i.e., if there is higher convection), more microwave energy can be supplied, all other things being equal. For this reason, in addition to the cooking chamber temperature, the convection-relevant parameter is also determined and considered in the evaluation.

[0015] Both parameters—the cooking chamber temperature and the convection-relevant parameter—influence the maximum permissible energy input from microwaves, thus determining the maximum permissible microwave power of the microwave source. Based on these parameters, the cooking chamber temperature and the convection-relevant parameter, it is possible to determine or estimate the maximum amount of energy a given component may absorb without being damaged. Therefore, a maximum permissible microwave power can be determined for the operating conditions. These operating conditions are defined by the cooking chamber temperature and the convection-relevant parameter.

[0016] In other words, it is possible to determine the maximum amount of additional energy input from the microwave source into the component so that a threshold or limit value for the temperature of the component is not reached and / or exceeded.

[0017] The maximum achievable microwave power, which is defined by the maximum permissible microwave power, can therefore be regulated depending on the cooking chamber temperature and the convection-relevant parameter.

[0018] In contrast to prior art safety shutdowns, which merely provide for completely preventing microwave operation, the method according to the invention provides for regulating or reducing the microwave power of the microwave source as necessary. The (theoretically possible) microwave power of the microwave source, i.e., the nominal power, is therefore reduced (situationally) to the maximum permissible microwave power according to the invention, instead of being completely set to zero. Situational reduction is understood to mean a reduction that depends on the detected or determined parameters, namely the cooking chamber temperature and the convection-relevant parameter. This allows the combination oven to be operated safely without necessarily switching off the microwave source. In other words, microwave operation of the combination oven is still possible.

[0019] The maximum permissible microwave power depends primarily on the component being considered. If multiple components are involved, the maximum permissible microwave power can be selected based on the component with the lowest maximum permissible microwave power. This ensures that none of the components are damaged. Therefore, a globally applicable maximum permissible microwave power can be determined.

[0020] The load status of the combination oven, moreover, plays no role in the regulation of the microwave power, meaning that the microwave power control is independent of the load. Instead of using the load as an additional parameter, the convection-related parameter is used, which allows for an assessment of any cooling effect of the component due to convection.

[0021] During evaluation, a maximum permissible energy input into a component of the combination cooking appliance and / or a maximum permissible temperature of a component of the combination cooking appliance can be taken into account. The maximum permissible microwave power is determined such that, when the microwave source is operated at the maximum permissible microwave power, the maximum permissible energy input into the component of the combination cooking appliance and / or the maximum permissible temperature of the component of the combination cooking appliance are not exceeded.

[0022] The maximum permissible energy input is understood to be the amount of energy that may be supplied to a component of the combination cooking appliance without the component being damaged by the energy absorption or reaching the maximum permissible temperature.

[0023] The maximum permissible temperature is understood to be the temperature that a component of the combination cooking appliance should not exceed, particularly during operation of the microwave source at the maximum permissible microwave power, for example in an empty cooking chamber.

[0024] The component of the combination oven can be any component or part of the combination oven within the cooking chamber, for example, a cooking chamber wall, a core temperature probe located in the cooking chamber, a core temperature probe cable, a sensor, a rack, lighting, and / or a viewing window in the cooking chamber door, in particular a glass pane. Each component of the combination oven has a maximum permissible energy input or a maximum permissible temperature above which damage to the components may occur. The maximum permissible energy input is therefore individual for each component. This applies equally to the maximum permissible temperature.

[0025] For example, the melting point of the insulation is used as the maximum permissible temperature for the core temperature probe, especially its cable. In the case of the viewing window in the oven door, the transition temperature of the pane installed in the viewing window, especially a glass pane, can be defined as the maximum permissible temperature.

[0026] By taking into account the maximum permissible energy input and / or the maximum permissible temperature, damage to a component during operation can be easily prevented.

[0027] One aspect stipulates that the cooking chamber temperature is measured by a temperature sensor located within a core temperature probe, and / or that the cooking chamber temperature is measured by a temperature sensor located within the cooking chamber of the combination oven. The temperature sensor can be located in a handle section or a measuring section of the core temperature probe. If the core temperature probe is in a parked position, i.e., not inserted into the food, any temperature sensor of the core temperature probe can be used, provided it is not thermally insulated in the parked position. If the core temperature probe is inserted into the food, i.e., in use, the temperature sensor located in the handle section can still be used. Alternatively or additionally, a temperature sensor that is part of the cooking chamber but located outside the core temperature probe can be used.

[0028] Furthermore, the determined convection-relevant parameter can be the rotational speed of a fan wheel, the volume of air exchanged per unit of time in the cooking chamber, or the air circulation within the cooking chamber. Specifically, the rotational speed of the fan wheel is measured by a sensor, and the air circulation, volume of air exchanged per unit of time, or air circulation within the cooking chamber is then determined based on this measurement. Alternatively, the sensor-measured rotational speed of the fan wheel can be directly considered in the evaluation to determine, among other things, the maximum permissible microwave power based on this speed.

[0029] Another aspect stipulates that a model, functional relationship, or table, preferably empirically determined, is used to calculate the maximum permissible microwave power based on the convection-relevant parameter and the cooking chamber temperature. The model, functional relationship, or table is specifically determined for each component. If multiple components are involved in limiting the microwave power of the microwave source to suit the situation, several models, functional relationships, or tables are used accordingly.

[0030] The model, functional relationship, or table is preferably based on data that has been determined beforehand. For example, the data may have been obtained from test series investigating the influence of varying microwave power on a cooking chamber with different convection-relevant parameters and / or different cooking chamber temperatures. In this way, a maximum permissible microwave power can be empirically determined for different combinations of a convection-relevant parameter and a cooking chamber temperature. This maximum permissible microwave power can be fed into the cooking chamber without exceeding a maximum permissible energy input into a component of the combination cooking appliance and / or a maximum permissible temperature of a component of the combination cooking appliance.The data obtained in this way can be used as a basis for the model, the functional relationship or the table in order to determine the maximum permissible microwave power depending on the convection-relevant parameter and the cooking chamber temperature, i.e. depending on the operating state of the combination cooking appliance, which is determined, among other things, by the convection-relevant parameter and / or the cooking chamber temperature.

[0031] In particular, at least one predetermined threshold value is provided for the convection-relevant parameter, whereby exceeding and / or falling below the threshold value results in a change in the relationship between the maximum permissible microwave power and the temperature. For example, the threshold value may be for the fan speed, since convection that cools the component only occurs above a certain speed. Convection may also be so strong at a certain fan speed that a higher speed would no longer improve cooling. Furthermore, a different threshold value may apply depending on the specific component. The respective threshold value may have been determined empirically. For the casing of a core temperature sensor, especially its cable, a fan speed threshold of 1,000 revolutions per minute (rpm) may be provided.The dependence of the maximum permissible microwave power on the speed of the fan, which serves as a convection-relevant parameter, is therefore different below a speed of 1,000 rpm than above a speed of 1,000 rpm.

[0032] For example, the maximum permissible microwave power is determined via the measured oven temperature and a microwave factor that depends on at least one predetermined threshold. The threshold can therefore first be used to determine a microwave factor, which is then used to calculate the maximum permissible microwave power. Specifically, the microwave factor depends linearly on the at least one predetermined threshold when the temperature falls below it, whereas it remains constant when the at least one predetermined threshold is exceeded.

[0033] For example, the dependence of the microwave factor MW factor as follows, if the predetermined threshold for the convection-relevant parameter is undershot: MW Faktor = Prop Faktor ∗ Parameter konvektionsrelevant + Offset , where Prop factor a proportionality factor that has been determined empirically or simulated, for example Parameters relevant to convection the convection-relevant parameter is and Offset A compensation value is used to determine the microwave factor when the convection-relevant parameter is 0.

[0034] In contrast, the microwave factor MW factor a constant ( const .), if the predetermined threshold for the convection-relevant parameter is exceeded: MW Faktor = const .

[0035] Furthermore, a temperature limit can be provided, whereby the maximum permissible microwave power is zero when the measured cooking chamber temperature reaches this limit. This provides an additional safety feature, as it ensures that no additional microwave energy is introduced when the cooking chamber temperature is already so high that the maximum permissible temperature of the component of the combination oven should already be reached, or when the difference between the cooking chamber temperature and the maximum permissible temperature of the component is only less than a safety margin. The temperature limit can be 300°C. Therefore, no further microwave energy may be introduced into the cooking chamber once the cooking chamber temperature reaches 300°C.

[0036] Specifically, it is stipulated that the microwave source will operate at no more than the maximum permissible microwave power, so that microwaves generated by the microwave source are fed into the cooking chamber. The actual maximum usable microwave power is therefore subject to change depending on the situation. The microwave source can be operated at a microwave power lower than the maximum permissible microwave power. In any case, the microwave power emitted by the microwave source cannot exceed the maximum permissible microwave power.

[0037] The maximum permissible microwave power can be greater than or equal to 0% and less than or equal to 100% of the rated power of the microwave source. Provided the operating condition of the combination oven (and its power supply) allows it, the full rated power of the microwave source can be utilized. In other words, the maximum permissible microwave power can range between 0% and 100% of the rated power of the microwave source, depending on the operating condition of the combination oven, which in turn depends on the measured cooking chamber temperature and the convection-related parameters.

[0038] Another aspect stipulates that the maximum permissible microwave power is determined several times during a cooking process, particularly regularly or periodically. This involves continuous monitoring of the current operating state of the combination oven, resulting in a (regular or periodic) adjustment of the maximum permissible microwave power.

[0039] The control system of a combination oven can take into account the maximum permissible microwave power, which has been previously determined, when controlling the microwave source, particularly when setting the power level for the microwave source. As explained above, the maximum permissible microwave power is not necessarily the actual microwave power of the microwave source, but rather a limit that must not be exceeded or (from a control perspective) can be exceeded.

[0040] Furthermore, when running a cooking program, the control system of the combination oven may take into account the specifications for the cooking chamber temperature (target cooking chamber temperature) and the convection-relevant parameter (target value for the convection-relevant parameter). This allows for adjustments to the cooking processes, such as an adjustment of the cooking time, if it is determined that the maximum permissible microwave power is low for a certain period, so that a reduction in cooking time by adding more microwave energy is not possible.

[0041] Furthermore, the invention relates to a combination cooking appliance for cooking food. The combination cooking appliance comprises a cooking chamber, a microwave source associated with the cooking chamber for supplying microwaves with a specific microwave power into the cooking chamber, a temperature sensor for detecting the cooking chamber temperature, and at least one sensor for detecting a convection-relevant parameter. The combination cooking appliance has an evaluation unit that is connected to the temperature sensor and the at least one sensor via signal transmission. The evaluation unit is configured to determine a maximum permissible microwave power for the microwave source based on the cooking chamber temperature detected by the temperature sensor and the convection-relevant parameter determined by the sensor. The combination cooking appliance has a control unit that is connected to the evaluation unit and the microwave source via signal transmission.The control system is configured to receive the maximum permissible microwave power determined by the evaluation unit and, based on this, to limit the microwave power of the microwave source. The combination cooking appliance is fundamentally designed and configured to perform the aforementioned procedure. The corresponding properties and advantages apply analogously to the combination cooking appliance.

[0042] As explained above, the microwave source is controlled by the control unit in such a way that the actual microwave power is less than or equal to the maximum permissible microwave power, which depends on the operating state of the combination oven. Therefore, a change in the operating state, i.e., the cooking chamber temperature and / or the convection-relevant parameter, also results in a different maximum permissible microwave power.

[0043] In particular, the maximum permissible microwave power is determined several times during a cooking process, especially regularly or periodically.

[0044] Further advantages and features of the invention will become apparent from the following description and the drawings, to which reference is made. The drawings show: Figure 1 a schematic representation of a combination cooking appliance according to the invention, Figure 2 the steps of a method according to the invention for the safe operation of the combination cooking appliance Figure 1 , and Figure 3 An overview illustrating the maximum permissible microwave power depending on the cooking chamber temperature and the convection-relevant parameter.

[0045] Figure 1 Figure 1 shows a combination cooking appliance 10 for cooking food 12, which has been placed in a cooking chamber 14 of the combination cooking appliance 10 to be cooked there.

[0046] Furthermore, the cooking chamber 14 is equipped with a cooking chamber door 16, which seals the cooking chamber 14 from the surrounding environment, thus creating a defined cooking climate within the cooking chamber 14 for cooking the food 12. The cooking chamber door 16 also has a viewing window 18, which serves to ensure a clear view of the food 12 from the outside during the cooking process. The viewing window 18 is, in particular, a pane of glass.

[0047] Separated from the cooking chamber 14 is a technical room 20, in which, among other things, components are at least partially housed that are necessary for generating and adjusting the cooking chamber climate, i.e. a cooking chamber atmosphere, in the cooking chamber 14 or that provide the energy for cooking the food 12.

[0048] In the embodiment shown, the combination cooking appliance 10 comprises a heating device 22, a steam generator 24, a microwave source 26 and a fan wheel 28.

[0049] The steam generator 24 and the heating device 22 are at least partially housed in the technical compartment 20 and serve, among other things, to provide the defined cooking chamber atmosphere in the cooking chamber 14, in particular the cooking chamber temperature and humidity. The cooking chamber atmosphere or climate generated in the cooking chamber 16 is thus defined, among other things, as a specific temperature in combination with a specific humidity. Additionally, a flow velocity and / or pressure can be provided with regard to the cooking chamber atmosphere, provided the fan wheel 28 is operated accordingly. In principle, the fan wheel 28 can therefore also contribute to the cooking chamber atmosphere or climate, since it regulates convection within the cooking chamber 14.

[0050] The microwave source 26 has at least one antenna 30 facing the cooking chamber 14 in order to couple microwaves generated by the microwave source 26 into the cooking chamber 14 and thus impart (additional) energy to the food 12 being cooked.

[0051] The combination oven 10 also has at least one oven chamber temperature sensor 32, which is configured to measure the oven chamber temperature in the oven chamber 14. The oven chamber temperature sensor 32 can also be referred to as an oven chamber sensor. In the illustrated embodiment, two oven chamber temperature sensors or oven chamber sensors 32 are shown, which can be arranged, in particular, distributed within the oven chamber 14. For example, an average value of the oven chamber temperatures recorded by the respective oven chamber sensors 32 is then used for further processing.

[0052] In addition, a core temperature probe 34 is provided in the cooking chamber 14, which has at least one temperature sensor 36.

[0053] If the core temperature probe 34 is not inserted into the food 12, the temperature sensor 36, which is integrated into the core temperature probe 34, could also be used to detect a cooking chamber temperature present in the cooking chamber 14, especially as a backup if the cooking chamber sensor 32 fails.

[0054] The cooking chamber sensor 32 and / or the core temperature probe 34, in particular its temperature sensor 36, can therefore be used to detect the cooking chamber temperature present in the cooking chamber 14.

[0055] In the embodiment shown, the core temperature sensor 34 is a wired core temperature sensor which has a cable 38 arranged in the cooking chamber 14, which, like the core temperature sensor 34 itself, is exposed to the cooking chamber climate, i.e. the cooking chamber temperature.

[0056] Furthermore, a sensor 40 is assigned to the fan wheel 28, which can be used to determine a convection-relevant parameter. The sensor 40 can be configured to measure the rotational speed of the fan wheel 28, which corresponds to the convection-relevant parameter, since the convection generated by the fan wheel 28 depends on its rotational speed.

[0057] Furthermore, the combination cooking appliance 10 has an evaluation unit 42 located in the technical compartment 20, which communicates with the aforementioned components via signal transmission, in particular the cooking chamber sensor 32, the core temperature probe 34 and the sensor 40. The evaluation unit 42 is therefore designed to receive and evaluate information from the aforementioned components, namely the cooking chamber temperature and the convection-relevant parameter such as the rotational speed.

[0058] The evaluation unit 42 can also be configured to determine another convection-relevant parameter based on the rotational speed detected by the sensor 40, for example, the rotational speed of the fan wheel 28, the volume of air exchanged per unit of time in the cooking chamber 14, or the circulation flow in the cooking chamber 14. Alternatively or additionally, a different type of sensor can be used to directly detect a convection-relevant parameter other than the rotational speed, e.g., a flow sensor arranged in the cooking chamber 14.

[0059] The evaluation unit 42 can also be connected to the heating device 22, the steam generator 24 and the microwave source 26 via signal transmission in order to obtain information or data from these components.

[0060] Basically, the evaluation unit 42 is designed and configured to evaluate the recorded cooking chamber temperature and the convection-relevant parameters in order to determine a maximum permissible microwave power, as detailed below with reference to the Figures 2 and 3 will be explained.

[0061] The evaluation unit 42 is also connected via signal transmission to a controller 44, which in turn is connected via signal transmission to at least the microwave source 26 in such a way that the microwave source 26 can be controlled by the controller 44. In other words, the controller 44 is designed and configured to control the microwave source 26, in particular depending on an evaluation result from the evaluation unit 42.

[0062] Accordingly, the control unit 44 is configured to limit the microwave power of the microwave source 26 to the maximum permissible microwave power, as will be explained below.

[0063] The control unit 44 can also be connected to the heating device 22, the steam generator 24 and / or the fan wheel 28 via signal transmission, such that the corresponding components can be controlled by the control unit 44. These connections are not shown here for the sake of clarity.

[0064] In principle, it is conceivable that the evaluation unit 42 and the control unit 44 are designed as a single combined unit, namely a control and / or evaluation unit.

[0065] The combination cooking appliance 10 is designed to carry out the inventive method for the safe operation of the combination cooking appliance 10 as explained below.

[0066] In a first step, the cooking chamber temperature 14 is recorded (step S1). For this purpose, the cooking chamber sensor 32 and / or the core temperature probe 34 measure the cooking chamber temperature 14.

[0067] The measured cooking chamber temperature is transmitted to the evaluation unit 42.

[0068] In a second step, the convection-relevant parameter is determined (step S2). For this purpose, sensor 40 measures in the present embodiment according to Figure 1 the rotational speed of the fan wheel 28, which is the convection-relevant parameter.

[0069] The rotational speed is transmitted to the evaluation unit 42. Based on the sensor-detected rotational speed, the evaluation unit 42 can calculate another convection-relevant parameter, provided that this parameter is usable for later evaluation.

[0070] In a third step, the evaluation unit 42 analyzes the recorded cooking chamber temperature and the convection-relevant parameter to determine a maximum permissible microwave power (step S3). During the evaluation, the evaluation unit 42 considers a maximum permissible energy input into at least one component of the combination cooking appliance 10 and / or a maximum permissible temperature of at least one component of the combination cooking appliance 10.

[0071] The maximum permissible microwave power is determined in such a way that, when operating the microwave source 26 with the maximum permissible microwave power, the maximum permissible energy input into the component of the combination cooking appliance 10 and / or the maximum permissible temperature of the component of the combination cooking appliance 10 are not exceeded.

[0072] The relevant component is, for example, the viewing window 18 or the core temperature sensor 34, in particular the cable 38 of the core temperature sensor 34.

[0073] In principle, several components can be considered when determining the maximum permissible microwave power, with each component having its own individual maximum permissible microwave power. The component with the lowest individual maximum permissible microwave power then, for example, determines the maximum permissible microwave power to ensure that no component of the combination oven 10 is damaged.

[0074] In particular, the evaluation unit 42 uses a model, a functional relationship, or a table for each component of the combination oven 10. The model, functional relationship, or table is specifically derived from data empirically obtained beforehand from a component of the combination oven 10. Using this data, the model, functional relationship, or table can then determine the maximum permissible microwave power as a function of the currently determined convection-relevant parameter and the currently measured cooking chamber temperature. In other words, the cooking chamber temperature and the convection-relevant parameter serve as input values ​​that the evaluation unit 42 uses to determine the maximum permissible microwave power with the aid of an algorithm or logic.

[0075] The maximum permissible microwave power is greater than or equal to 0% and less than or equal to 100% of the nominal power of the microwave source 26. This depends on the operating state of the combination cooking appliance 10, namely on the detected cooking chamber temperature and the convection-relevant parameter, for example the rotational speed.

[0076] In Figure 3 Diagrams are shown that illustrate how the maximum permissible microwave power depends on the cooking chamber temperature and the convection-relevant parameter.

[0077] The first diagram shows the maximum permissible microwave power (in %), referred to there as "available MW", compared to the measured cooking chamber temperature. GT is (in °C) shown for three different convection-relevant parameters, namely for a fan wheel speed of 28 ("LR") of 500 rpm, 750 rpm and > 1000 rpm.

[0078] In the second diagram, the maximum permissible microwave power (in %), referred to there as "available MW", is compared to the convection-relevant parameter in the form of the fan wheel speed 28 LR speed (in rpm) for five different cooking chamber temperatures GT is shown, namely for cooking chamber temperatures GT is of 270°C, 280°C, 285°C, 290°C and 295°C.

[0079] The third diagram shows a three-dimensional diagram, where the maximum permissible microwave power (in %), referred to there as "available MW", is compared to the measured cooking chamber temperature. GT is (in °C) and the speed of the fan wheel 28 LR speed (in rpm) is shown.

[0080] As explained above, the maximum permissible microwave power is a limit value for the microwave source 26, which does not necessarily correspond to the microwave power actually supplied by the microwave source 26. Rather, the theoretically possible microwave power is limited under certain circumstances, namely depending on the cooking chamber temperature and the convection-relevant parameter, as can be clearly seen from Figure 3 emerges.

[0081] It is particularly clear from this that a temperature limit is provided, whereby the maximum permissible microwave power is zero when the detected cooking chamber temperature reaches the temperature limit. In the illustrated embodiment, the temperature limit is set at 300°C.

[0082] The diagrams also show that at least one predetermined threshold value is provided for the convection-relevant parameter, whereby exceeding and / or falling below this threshold value results in a change in the relationship between the maximum permissible microwave power and the fan speed. In the illustrated embodiment, the threshold value corresponds to a fan speed of 1,000 revolutions per minute (rpm). Above this speed, i.e., the threshold of 1,000 rpm, the maximum permissible microwave power is 100%, whereas below this speed, the maximum permissible microwave power decreases with decreasing speed.

[0083] Furthermore, the diagrams show that there is a linear relationship between the cooking chamber temperature and the maximum permissible microwave power, whereby the linearity in turn depends on the convection-relevant parameter, i.e. the rotational speed.

[0084] In principle, the maximum permissible microwave power can be determined via the measured cooking chamber temperature and a microwave factor that depends on at least one predetermined threshold value. This allows for a functional relationship to be established for the maximum permissible microwave power. MW max which can be expressed as follows: MW max = 300 − GT ist MW Faktor ∗ 100 , where GT is The measured cooking chamber temperature is also relevant. Furthermore, the microwave factor is important in this functional context. MW factor The microwave factor is provided, which describes the linear dependence of the maximum permissible microwave power on the cooking chamber temperature and itself depends on the convection-relevant parameter, as already explained above with reference to the diagrams. MW factor This can be represented as follows: If the predetermined threshold (1,000 rpm) for the convection-relevant parameter is undershot, then the microwave factor is... MW factorThe following connection: MW Faktor = Prop Faktor ∗ Parameter konvektionsrelevant + Offset , where Prop factor a proportionality factor that has been determined empirically or simulated, for example Parameters relevant to convection The parameter relevant to convection is, for example, the rotational speed. Offset is a compensation value that adjusts the microwave factor MW factor determined when the convection-relevant parameter, for example the rotational speed, is 0.

[0085] In contrast, the microwave factor MW factor a constant ( const .), if the predetermined threshold (1,000 rpm) for the convection-relevant parameter is exceeded: MW Faktor = const . = 20

[0086] Furthermore, the evaluation unit is programmed to set the maximum permissible microwave power to 100 if the above functional relationship would result in a value greater than 100, and to 0 if the above functional relationship would result in a value less than 0. This ensures that the maximum permissible microwave power lies between 0% and 100% of the nominal power of the microwave source 26, as explained above.

[0087] Once the evaluation unit 42 has determined the maximum permissible microwave power, this is then sent to the control unit 44.

[0088] The controller 44 then limits the actual microwave power output of the microwave source 26 to the maximum permissible microwave power (step S4). This can be achieved either by controlling or regulating the microwave source 26 accordingly, or by activating an attenuator that limits the microwave power. The microwave power can be controlled or regulated via pulse-width modulation (PWM) by setting time intervals between microwave pulses, for example, a PWM of 20%, specifically a pulse duration of 200 ms and a pause of 800 ms. The microwave source 26 is then operated in such a way that its actual microwave power output never exceeds the currently applicable maximum permissible microwave power.However, the actual emitted microwave power may be below the maximum permissible microwave power, as this only represents a limit for the microwave source 26, which must not be exceeded to ensure that the component of the combination cooking appliance 10 is not damaged, for example, the casing of the core temperature probe 34, in particular the cable 38.

[0089] The procedure described here can be carried out both at the start of a cooking process and at regular time intervals during the cooking process.

[0090] In other words, the maximum permissible microwave power can be determined multiple times during a cooking process. First, the operating state of the combination oven 10, i.e., the cooking chamber temperature and the convection-relevant parameter, is recorded several times during the cooking process, particularly regularly or periodically. Based on this data, the maximum permissible microwave power can be determined. This ensures that both efficiency and safety are maximized, as the theoretically maximum possible microwave power is adjusted to the specific situation.

Claims

1. A method for the safe operation of a combination cooking appliance (10) having a cooking chamber (14) and a microwave source (26) with a microwave power, the method comprising the steps of: - detecting a cooking chamber temperature prevailing in the cooking chamber (14), characterized by: - determining a convection-relevant parameter, - evaluating the detected cooking chamber temperature and the convection-relevant parameter to determine a maximum permissible microwave power, and - limiting the microwave power of the microwave source (26) to the maximum permissible microwave power.

2. The method according to claim 1, characterized in that the cooking chamber temperature is detected by a temperature sensor (36) arranged in a core temperature probe (34), and / or in that the cooking chamber temperature is detected by a temperature sensor (32) arranged in the cooking chamber (14) of the combination cooking appliance (10).

3. The method according to claim 1 or 2, characterized in that the determined convection-relevant parameter is a rotational speed of a fan wheel (28), a rotating velocity of a fan wheel (28), a volume per time unit of exchanged air in the cooking chamber (14) or a circulating flow in the cooking chamber (14).

4. The method according to any of the preceding claims, characterized in that a model, a functional relationship or a table has been determined, in particular empirically, based on which the maximum permissible microwave power is determined as a function of the convection-relevant parameter and the cooking chamber temperature.

5. The method according to any of the preceding claims, characterized in that at least one predetermined threshold value is provided for the convection-relevant parameter, exceeding and / or falling below the threshold value resulting in a modified dependency of the maximum permissible microwave power.

6. The method according to claim 5, characterized in that the maximum permissible microwave power is determined via the detected cooking chamber temperature and a microwave factor which depends on the at least one predetermined threshold value.

7. The method according to any of the preceding claims, characterized in that a temperature limit is provided, the maximum permissible microwave power being zero when the detected cooking chamber temperature reaches the temperature limit.

8. The method according to any of the preceding claims, characterized in that the microwave source (26) is operated at most at the maximum permissible microwave power, so that microwaves generated by the microwave source (26) are fed into the cooking chamber (14) and / or that the maximum permissible microwave power is greater than 0% and less than or equal to 100% of the nominal power of the microwave source (26).

9. The method according to any of the preceding claims, characterized in that the maximum permissible microwave power is determined several times during a cooking operation.

10. A combination cooking appliance (10) for cooking a cooking product (12), the combination cooking appliance (10) having a cooking chamber (14), a microwave source (26) associated with the cooking chamber (14) for feeding microwaves with a specific microwave power into the cooking chamber (14), a temperature sensor (32, 36) for detecting a cooking chamber temperature, and at least one sensor (40) for detecting a convection-relevant parameter, the combination cooking appliance (10) having an evaluation unit (42) which is connected in a signal-transmitting manner to the temperature sensor (32, 36) and to the at least one sensor (40), the evaluation unit (42) being set up to determine a maximum permissible microwave power for the microwave source (26) based on the cooking chamber temperature detected by the temperature sensor (32, 36) and the convection-relevant parameter determined by the sensor (40), and the combination cooking appliance (10) having a control unit (44) which is connected in a signal-transmitting manner to the evaluation unit (42) and to the microwave source (26), the control unit (44) being set up to receive the maximum permissible microwave power determined by the evaluation unit (42) and to limit the microwave power of the microwave source (26) on the basis thereof.

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