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 or large-scale catering typically have, in addition to a heating device for generating hot air, a steam generator for generating steam to cook food placed in the cooking chamber. The heating device and the steam generator create a cooking chamber atmosphere, which can also be referred to as the cooking chamber climate. Food exposed to the cooking chamber climate is cooked accordingly by the convection-based energy being introduced into the food.

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

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

[0005] The absorption of microwave radiation fed into the cooking chamber can lead to damage, depending on the material and composition of the components. To prevent such damage, current technology proposes equipping cooking appliances with automatic safety shutoffs. These detect idle operation—i.e., operating the cooking appliance with an empty cooking chamber—and automatically shut off the microwave feed.

[0006] For example, DE 10 2004 015 993 A1 discloses a microwave oven which automatically detects idle operation and automatically switches off a device for generating microwaves when idle operation of the cooking appliance has been detected.

[0007] However, it has been found that even with small or even medium loads, wear and tear on cooking appliance components can occur under certain circumstances, even when microwave operation is generally permitted. This wear and tear or damage is undesirable, as the corresponding components must be replaced early, which increases costs.

[0008] In this respect, the object of the present invention is to eliminate the disadvantages of the prior art and to provide a method with 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 having a cooking chamber and a microwave source with a microwave power, the method comprising the following steps: Detecting a cooking chamber temperature present in the cooking chamber, determining a convection-relevant parameter, evaluating the detected cooking chamber temperature and the convection-relevant parameter in order 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 detected cooking chamber temperature and the determined convection-relevant parameter.

[0010] The invention is based on the basic 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 parameter and the detected cooking chamber temperature.

[0011] The maximum permissible microwave power may therefore be lower than the fundamentally possible microwave power (rated power of the microwave source). The actual maximum permissible microwave power therefore depends on the recorded cooking chamber temperature and the determined convection-relevant parameter. In other words, the maximum permissible microwave power is predetermined by the control system, namely, depending on the recorded cooking chamber temperature and the determined convection-relevant parameter. The maximum permissible microwave power is therefore variable, especially during an ongoing cooking process, since the cooking chamber temperature and / or the convection-relevant parameter change or will change during the cooking process.

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

[0013] It has been determined that microwave energy can couple into components of the combination cooking appliance that are located in or confined to the cooking chamber, causing these components to heat up. This leads to increased wear or even damage to the components, which is now effectively prevented, enabling reliable and safe operation of the combination cooking appliance. The components located in the cooking chamber include, in particular, wired core temperature sensors, which should not exceed a certain temperature.

[0014] If convection occurs around the respective component, i.e., if there is a flow around it, it can be cooled, which means the component heats up less. With strong convection or flow around the component, more thermal energy can be dissipated than with weak convection. If more thermal energy can be dissipated, i.e., if there is greater convection, more microwave energy can generally be fed in, all other conditions being equal. For this reason, in addition to the cooking chamber temperature, the convection-relevant parameter is also determined and taken into account in the evaluation.

[0015] Both parameters—the cooking chamber temperature and the convection-related parameter—influence the permissible energy input from microwaves, which determines the maximum permissible microwave power of the microwave source. Based on these parameters—the cooking chamber temperature and the convection-related parameter—it is possible to determine or estimate the maximum amount of energy a particular component can absorb without being damaged. This allows a maximum permissible microwave power to be determined, which is permissible for the given operating condition. The operating condition is determined by the cooking chamber temperature and the convection-related parameter.

[0016] In other words, it is possible to determine the maximum additional energy input by 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 actual maximum microwave power that can be used, 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 safety shutdowns known from the prior art, which merely provide for the complete prevention of microwave operation, the method according to the invention provides for the regulation or reduction of the microwave power of the microwave source, if necessary. According to the invention, the (theoretically possible) microwave power of the microwave source, i.e., the nominal power, is therefore reduced (situationally) to the maximum permissible microwave power instead of being set completely to zero. A situational reduction is understood to mean a reduction that depends on the recorded or determined parameters, namely the cooking chamber temperature and the convection-relevant parameter. This allows the combination cooking appliance to be operated safely without necessarily switching off the microwave source. In other words, microwave operation of the combination cooking appliance is still possible.

[0019] The maximum permissible microwave power depends particularly on the component being considered. If multiple components are being considered, the maximum permissible microwave power can be selected based on the component that allows the lowest maximum permissible microwave power. This ensures that none of the components considered are damaged. In this way, a global maximum permissible microwave power can be determined.

[0020] Furthermore, the load status of the combination cooking appliance cannot play a role in regulating the microwave power, so the microwave power is regulated independently of the load of the combination cooking appliance. Instead of using the load as an additional parameter, the convection-relevant parameter is used, which allows a statement to be made about any cooling effect of the component due to convection.

[0021] During the 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 input of energy to which a component of the combination cooking appliance may be supplied without the component being damaged by the absorption of the energy or reaching the maximum permissible temperature.

[0023] The maximum permissible temperature is the temperature that a component of the combination cooking appliance should not exceed, particularly when the microwave source is operating at the maximum permissible microwave power, for example when the cooking chamber is empty.

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

[0025] For example, the melting point of a sheath is used as the maximum permissible temperature for the core temperature sensor, especially its cable. In the case of the cooking chamber door's viewing window, the transition temperature of the pane installed in the viewing window, especially the 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 provides that the cooking chamber temperature is detected by a temperature sensor arranged in a core temperature probe, and / or that the cooking chamber temperature is detected by a temperature sensor arranged in the cooking chamber of the combination cooking appliance. The temperature sensor can be provided 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 to be cooked, any temperature sensor of the core temperature probe can be used, provided that it is not thermally insulated in the parked position. If the core temperature probe is inserted into a food to be cooked, i.e. is being used, the temperature sensor provided in the handle section can still be used. Alternatively or additionally, a temperature sensor can be used that is assigned to the cooking chamber but is located outside the core temperature probe.

[0028] Furthermore, the determined convection-relevant parameter can be a fan speed, a fan wheel rotation speed, a volume of air exchanged per unit time in the cooking chamber, or a circulation flow in the cooking chamber. In particular, the fan wheel speed is detected by a sensor, based on which the rotation speed, the volume of air exchanged per unit time in the cooking chamber, or the circulation flow in the cooking chamber are then determined. However, the sensor-detected fan wheel speed can also be directly considered in the evaluation in order to then determine the maximum permissible microwave power based, among other things, on the speed.

[0029] Another aspect requires that a model, a functional relationship, or a table has been determined, particularly empirically, on which the maximum permissible microwave power is determined depending on the convection-relevant parameter and the cooking chamber temperature. The model, functional relationship, or table is determined specifically for the respective component. If multiple components are involved to limit the microwave power of the microwave source in a specific situation, multiple models, functional relationships, or tables are used accordingly.

[0030] The model, functional relationship, or table is preferably based on data that has been determined in advance. For example, the data has been obtained from test series investigating the influence of varying microwave power on a cooking chamber with various convection-relevant parameters and / or different cooking chamber temperatures. For different combinations of a convection-relevant parameter and a cooking chamber temperature, a maximum permissible microwave power can be empirically determined that may 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 thus obtained can be used as a basis for the model, the functional relationship or the table in order to determine the maximum permissible microwave power as a function of the convection-relevant parameter and the cooking chamber temperature, i.e. as a function of 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, wherein exceeding and / or falling below the threshold value results in a changed dependency of the maximum permissible microwave power. For example, the threshold value can be provided for the speed of the fan impeller, since convection, which results in cooling of the component, only occurs above a certain speed. Also, above a certain speed of the fan impeller, such great convection may already be present that a higher speed would no longer result in better cooling. Furthermore, a different threshold value can exist depending on the respective component. The respective threshold value can be determined empirically. For the sheath of a core temperature sensor, in particular its cable, a threshold value for the fan speed of 1,000 revolutions per minute (rpm) can 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 at a speed above 1,000 rpm.

[0032] For example, the maximum permissible microwave power is determined based on the detected cooking chamber temperature and a microwave factor that depends on the at least one predetermined threshold. The threshold can therefore initially be used to determine a microwave factor, which is then used to calculate the maximum permissible microwave power. In particular, the microwave factor depends linearly on the at least one predetermined threshold when the temperature falls below the at least one predetermined threshold, whereas the microwave factor is otherwise a constant, i.e., 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 value for the convection-relevant parameter is exceeded: MW Faktor = Prop Faktor ∗ Parameter konvektionsrelevant + Offset , where Prop Factor is a proportionality factor that has been determined empirically or simulated, Parameters relevant to convection the convection-relevant parameter and Offset is a compensation value that determines 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 value 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 detected cooking chamber temperature reaches the temperature limit. This provides an additional level of safety, as it ensures that no additional microwave energy is introduced if the cooking chamber temperature is already so high that the maximum permissible temperature of the component of the combination cooking appliance should already have been reached, or if there is only a difference between the cooking chamber temperature and the maximum permissible temperature of the component that is smaller than a safety margin. The temperature limit can be 300°C. Therefore, once the cooking chamber temperature reaches 300°C, no further microwave energy may be introduced into the cooking chamber.

[0036] In particular, it is intended that the microwave source be operated 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 microwave power that can be applied is therefore adjusted depending on the situation. The microwave source can be operated at a microwave power that is 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 cooking appliance (and the combination cooking appliance's power connection) permits, the full rated power of the microwave source can be utilized. In other words, the maximum permissible microwave power can be between 0% and 100% of the rated power of the microwave source, depending on the operating condition of the combination cooking appliance, which depends on the recorded cooking chamber temperature and the convection-relevant parameter.

[0038] Another aspect provides for the maximum permissible microwave power to be determined several times during a cooking process, particularly regularly or periodically. Thus, the current operating status of the combination cooking appliance is continuously monitored, resulting in a (regular or periodic) adjustment of the maximum permissible microwave power.

[0039] A control system for the combination cooking appliance can take the previously determined maximum permissible microwave power into account when controlling the microwave source, particularly when specifying the microwave source's power level. 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 can be exceeded (for control purposes).

[0040] When executing a cooking program, the control system of the combination cooking appliance can also be configured to 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, for example, a cooking time adjustment, if it is determined that the maximum permissible microwave power is low for a certain period of time, making it impossible to shorten the cooking time by adding additional microwave energy.

[0041] The invention further relates to a combination cooking appliance for cooking food. The combination cooking appliance comprises a cooking chamber, a microwave source assigned to the cooking chamber for feeding microwaves with a specific microwave power into the cooking chamber, a temperature sensor for detecting a 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 in a signal-transmitting manner. 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 controller that is connected to the evaluation unit and the microwave source in a signal-transmitting manner.The control unit 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 carry out the aforementioned method. The corresponding properties and advantages apply analogously to the combination cooking appliance.

[0042] As explained above, the microwave source is controlled by the control system 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 cooking appliance. If the operating state changes, i.e., the cooking chamber temperature and / or the convection-relevant parameter, the maximum permissible microwave power also changes.

[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. In the drawings: 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 from Figure 1 , and Figure 3 an overview which illustrates the maximum permissible microwave power depending on the cooking chamber temperature and the convection-relevant parameter.

[0045] 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 assigned a cooking chamber door 16, which seals the cooking chamber 14 from the surroundings, so that a defined cooking chamber climate can be created 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 glass pane.

[0047] Separate from the cooking chamber 14, a technical room 20 is provided in which, among other things, components are at least partially accommodated which are necessary for generating and adjusting the cooking chamber climate, i.e. a cooking chamber atmosphere, in the cooking chamber 14 or which 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 room 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 cooking chamber 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 respect 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 cooking chamber climate, since this establishes convection within the cooking chamber 14.

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

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

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

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

[0054] The cooking chamber temperature in the cooking chamber 14 can therefore be detected using the cooking chamber sensor 32 and / or the core temperature sensor 34, in particular its temperature sensor 36.

[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] In addition, a sensor 40 is assigned to the fan wheel 28, via which a convection-relevant parameter can be determined. 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 arranged in the technical room 20, which is connected to the above-mentioned components in a signal-transmitting manner, i.e. in particular the cooking chamber sensor 32, the core temperature sensor 34 and the sensor 40. In this respect, the evaluation unit 42 is configured to receive information from the above-mentioned components and to evaluate it, i.e. the cooking chamber temperature and the convection-relevant parameters such as the 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 a rotational speed of the fan wheel 28, a volume of air exchanged per unit of time in the cooking chamber 14 or a circulation flow in the cooking chamber 14. Alternatively or additionally, a different type of sensor can also be used to directly detect a convection-relevant parameter other than the rotational speed, for example a flow sensor arranged in the cooking chamber 14.

[0059] The evaluation unit 42 can in principle also be connected to the heating device 22, the steam generator 24 and the microwave source 26 in a signal-transmitting manner in order to receive 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 parameter in order to determine a maximum permissible microwave power, as will be described in more detail below with reference to the Figures 2 and 3 is explained.

[0061] The evaluation unit 42 is also connected for signal transmission to a controller 44, which in turn is connected for signal transmission at least to the microwave source 26 such 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 of the evaluation unit 42.

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

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

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

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

[0066] In a first step, the cooking chamber temperature in the cooking chamber 14 is recorded (step S1). For this purpose, the cooking chamber sensor 32 and / or the core temperature probe 34 measures the cooking chamber temperature in the cooking chamber 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, the sensor 40 in the present embodiment measures according to Figure 1 the speed of the fan wheel 28, which is the convection-relevant parameter.

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

[0070] In a third step, the measured cooking chamber temperature and the convection-relevant parameter are evaluated by the evaluation unit 42 to determine a maximum permissible microwave power (step S3). During the evaluation, the evaluation unit 42 takes into account 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 such that when the microwave source 26 is operated 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 corresponding 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, specifies the maximum permissible microwave power to ensure that no component of the combination cooking appliance 10 is damaged.

[0074] In particular, the evaluation unit 42 uses a model, a functional relationship, or a table for the respective component of the combination cooking appliance 10. The model, the functional relationship, or the table has been determined, in particular, based on data that was previously empirically determined for a component of the combination cooking appliance 10. Using this data, the model, the functional relationship, or the table can then determine the maximum permissible microwave power as a function of the currently determined convection-relevant parameter and the currently recorded 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 rated power of the microwave source 26. This depends on the operating state of the combination cooking appliance 10, namely the recorded cooking chamber temperature and the convection-relevant parameter, for example the 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] In the first diagram, the maximum permissible microwave power (in %), referred to as "available MW", is compared to the recorded cooking chamber temperature GT is (in °C) for three different convection-relevant parameters, namely for a speed of the fan wheel 28 ("LR") of 500 rpm, 750 rpm and > 1000 rpm.

[0078] In the second diagram, the maximum permissible microwave power (in %), referred to as "available MW", is compared to the convection-relevant parameter in the form of the speed of the fan wheel 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 plotted against the recorded cooking chamber temperature GT is (in °C) and the speed of the fan wheel 28 LR speed (in rpm).

[0080] As already explained above, the maximum permissible microwave power is a limit value for the microwave source 26, which does not necessarily have to correspond to the microwave power actually generated 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] This particularly makes it clear 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, with exceeding and / or falling below the threshold value resulting in a changed dependency of the maximum permissible microwave power. 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 value 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 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 can result in a functional relationship 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 recorded cooking chamber temperature is also important in the functional context of the microwave factor MW factor 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 using the diagrams. The microwave factor MW factor can be represented as follows: If the predetermined threshold value (1,000 rpm) for the convection-relevant parameter is undercut, then the microwave factor MW factorfollowing connection: MW Faktor = Prop Faktor ∗ Parameter konvektionsrelevant + Offset , where Prop Factor is a proportionality factor that has been determined empirically or simulated, Parameters relevant to convection the convection-relevant parameter, for example the speed. The parameter Offset is a compensation value that determines the microwave factor MW factor determined when the convection-relevant parameter, for example the speed, is 0.

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

[0086] Furthermore, the evaluation unit stores that the maximum permissible microwave power has a value of 100 if the above functional relationship would result in a value greater than 100, and a value of 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 rated power of the microwave source 26, as already explained above.

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

[0088] The controller 44 then limits the actually output microwave power of the microwave source 26 to the maximum permissible microwave power (step S4). The microwave source 26 can either be controlled or regulated accordingly, or an attenuation element is switched on to limit the microwave power. The microwave power can be controlled or regulated via pulse width modulation by setting time intervals between microwave pulses, e.g., a PWM of 20%, in particular a pulse duration of 200 ms and a pause of 800 ms. The microwave source 26 is then operated such that its actually output microwave power never exceeds the currently available maximum permissible microwave power.However, the actual microwave power output may be below the maximum permissible microwave power, since this merely represents a limit value for the microwave source 26, which must not be exceeded in order to ensure that the component of the combination cooking appliance 10 is not damaged, for example a sheath of the core temperature sensor 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 intervals during the cooking process.

[0090] In other words, the maximum permissible microwave power can be determined several times during a cooking process. First, the operating state of the combination cooking appliance 10, i.e., the cooking chamber temperature and the convection-relevant parameters, are recorded several times during the cooking process, particularly regularly or periodically, so that these values ​​can be evaluated based on this data to determine the maximum permissible microwave power. This ensures that both efficiency and safety are maximized, since the theoretically maximum possible microwave power is adjusted depending on the 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 following steps: - detecting a cooking chamber temperature present in the cooking chamber (14), - determining a convection-relevant parameter, - evaluating the detected cooking chamber temperature and the convection-relevant parameter in order to determine a maximum permissible microwave power, and - limiting the microwave power of the microwave source (26) to the maximum permissible microwave power.

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

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

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

5. Method according to one of the preceding claims, characterized in that at least one predetermined threshold value is provided for the convection-relevant parameter, wherein exceeding and / or falling below the threshold value results in a changed dependence of the maximum permissible microwave power.

6. Method according to claim 5, characterized in thatthe 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. Method according to one of the preceding claims, characterized in that a temperature limit is provided, whereby the maximum permissible microwave power is zero when the detected cooking chamber temperature reaches the temperature limit.

8. Method according to one of the preceding claims, characterized in that the microwave source (26) is operated at most with 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 rated power of the microwave source (26).

9. Method according to one of the preceding claims, characterized in thatthe maximum permissible microwave power is determined several times during a cooking process.

10. A combination cooking appliance (10) for cooking food (12), wherein the combination cooking appliance (10) comprises 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, wherein the combination cooking appliance (10) has an evaluation unit (42) which is connected to the temperature sensor (32, 36) and the at least one sensor (40) in a signal-transmitting manner, wherein the evaluation unit (42) is configured 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 wherein the combination cooking appliance (10) has a control (44),which is connected to the evaluation unit (42) and the microwave source (26) in a signal-transmitting manner, wherein the controller (44) is configured to receive the maximum permissible microwave power determined by the evaluation unit (42) and, on the basis thereof, to limit the microwave power of the microwave source (26).

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