EP4359707A1

EP4359707A1 - Method for operating a cooking appliance, and cooking appliance

Info

Publication number: EP4359707A1
Application number: EP22731665.0A
Authority: EP
Inventors: Helge Nelson
Original assignee: Miele und Cie KG
Current assignee: Miele und Cie KG
Priority date: 2021-06-23
Filing date: 2022-06-03
Publication date: 2024-05-01
Also published as: BE1029519B1; BE1029519A1; WO2022268482A1

Abstract

The invention relates to a method for operating a cooking appliance (2) and to a corresponding cooking appliance (2). The cooking appliance (2) comprises a cooking chamber (4) for holding food (5), a treatment device for treating the food (5), a control device (16) for controlling at least the treatment device, and a vapor fan (18), by means of which a gas mixture can be conveyed from the cooking chamber (4) into an environment outside of the cooking appliance (2). The moisture of the gas mixture is determined indirectly on the basis of at least one captured parameter of the gas mixture and on the basis of at least one captured operating parameter of the vapor fan (18) to which the gas mixture is applied, the at least one captured parameter of the gas mixture comprising at least one captured temperature of the gas mixture.

Description

Method for operating a cooking appliance and cooking appliance

The present invention relates to a method for operating a cooking appliance and a corresponding cooking appliance.

When cooking food, especially when baking food, not only the cooking cabinet temperature but also the humidity in the cooking cabinet has a major impact on the cooking result. For example, when baking, to achieve a nice crust and browning, it is advantageous to have a relatively low level of humidity in the cooking space. The starting point for humidity control is reliable recording of the current humidity in the cooking chamber.

For measuring the humidity in the cooking chamber, specially designed humidity sensors are known from the prior art. However, such humidity sensors are expensive to manufacture and prone to failure because they are exposed to strong contaminants, especially at higher cooking temperatures.

As an alternative to the humidity sensors, indirect measurement methods have been proposed in which, based on recorded parameters of the gas mixture in the cooking chamber, such as e.g. B. its temperature and / or pressure, and detected operating parameters of the Umluftgeblä ses such. B. the power consumption and / or the speed of the circulating air fan antrei existing motor, the humidity in the cooking chamber is determined.

The humidity of the gas mixture influences its density. The density of the gas mixture influences the flow resistance against which the air circulation fan has to work. By absorbing water vapor, the density of the gas mixture decreases because, given the same total pressure, an added number of water molecules displaces the same number of heavier nitrogen and oxygen molecules. If, for example, the temperature and pressure of the gas mixture and the motor power of the blower are constant, an increase in the motor speed indicates a reduction in the density of the gas mixture and thus an increase in humidity. The same applies if a reduced power consumption of the motor can be observed at constant temperature, constant pressure and constant motor speed.

EP 1 342 414 A1 shows such an indirect measurement method, in which only the temperature of the gas mixture and the speed of the motor driving the circulating air fan are measured and compared with characteristic curves created beforehand under defined conditions.

The current humidity of the gas mixture can be determined from a deviation of the measured engine speed from the stored engine speed. A disadvantage of these solutions is that a moisture measurement is only possible when the circulating air fan is operated or running, since otherwise no change in the operating parameters of the fan can be detected. As a result, in operating modes in which circulation of the gas mixture in the cooking chamber is undesirable, for example because this would have a negative effect on the cooking result, moisture measurement cannot take place or can only take place to a limited extent.

It is therefore the object of the present invention to provide a method for operating a cooking device in which the moisture can be reliably detected--particularly independently of the selected operating mode--with the disadvantages of the prior art being at least partially reduced or avoided. It is also the object of the present invention to provide a corresponding cooking appliance.

This object is achieved by a method having the features of claim 1. Furthermore, this object is achieved by a cooking appliance with the features of claim 9. Preferred features are the subject of the dependent claims. Further advantages and features can be found in the general description and the exemplary embodiments.

In the method according to the invention for operating a cooking appliance, which has a cooking chamber for accommodating food to be cooked, a treatment device for treating the food to be cooked, a control device for controlling at least the treatment device and a fume fan, with which a gas mixture from the cooking chamber into an environment outside the Garge The humidity of the gas mixture is determined indirectly on the basis of at least one recorded parameter of the gas mixture and on the basis of at least one recorded operating parameter of the vapor blower to which the gas mixture is applied, the at least one recorded parameter of the gas mixture being at least one recorded Includes temperature of the gas mixture.

The vapor fan is used exclusively to convey gas mixture from the cooking chamber in a surrounding environment outside of the cooking appliance, ie it is only used for vapor removal. Since the gas mixture flows around or is applied to the fume fan essentially permanently or at least over long periods of time, a change in the humidity in the gas mixture has a direct effect on the operating parameters of the fume fan, which means that humidity can be measured reliably. In contrast to a circulating air fan, the vapor fan, which is usually smaller, is not used to circulate the gas mixture in the cooking chamber. A circulating effect possibly caused by the operation of the vapor fan in the cooking space is only minimal and in any case significantly lower than a circulating effect caused by a circulating fan. Consequently, a moisture measurement using a vapor fan has no or hardly any negative effects on the cooking result. nis and can therefore be carried out without any problems regardless of the selected operating mode. The cooking appliance preferably has a circulating air fan, different from the vapor fan, for circulating the gas mixture in the cooking chamber.

The vapor fan is also not used to transport cooling air that be certain components of the cooking appliance to cool, z. B. the electronics, is sucked from the vicinity of the Garge rats. In a preferred embodiment of the invention, the cooking appliance has a cooling fan that is different from the vapor fan. This has the advantage that the vapor removal and cooling processes can be optimized independently of one another for the desired operating mode. For example, when baking a cake at lower temperatures (e.g. in the range of 160 °C), only a low cooling capacity is required, while the vapors still have to be removed for better crust formation and browning. On the other hand, a pyrolysis process (temperatures around 450 °C and more) requires strong cooling, while at the same time only a small amount of gas mixture and thus energy should be removed from the cooking chamber. In cooking appliances in which the cooling fan is designed both for cooling and for vapor removal, the flow rate of the cooling fan is set based on the more important for the selected mode of the two functions (cooling, vapor removal). A non-optimal setting of the other function is accepted. By using different blowers, each function can be optimally adjusted to the selected operating mode.

Cookers, ovens, combination ovens with steamer and/or microwave function, ovens with high-frequency technology and microwave ovens can be considered as cooking appliances for the purposes of this invention. The treatment device of the cooking appliance preferably comprises at least one thermal heating source for thermal treatment of the food to be cooked and/or at least one high-frequency generator for dielectric heating of the food to be cooked. The treatment device can include bottom heat, top heat, grill heating and/or a circulating air fan equipped with a ring heater as a thermal heat source. In particular, the treatment device includes a steam generator.

The cooking appliance preferably has a temperature sensor with which the temperature of the gas mixture is measured. In particular, the temperature sensor is arranged inside the cooking space. In particular, the cooking appliance has suitable sensors for detecting further parameters of the gas mixture, such as e.g. B. a pressure sensor for detecting the current pressure in the cooking chamber.

The cooking appliance preferably has suitable sensors for detecting the operating parameter or parameters of the vapor fan, e.g. B. a tachometer for measuring the speed of the steam blower driving engine and / or means for detecting the power intake of the engine. Other factors influencing the operating parameters of the Wrasengebläse such. B. the temperature of the motor, can also be recorded using suitable means and taken into account when calculating the humidity. Alternatively, the engine temperature curve over time can be estimated using a suitable model and taken into account when calculating the humidity.

To determine the humidity, the speed and power consumption of a motor driving the steam blower and/or a speed difference from the synchronous speed, i.e. the slip, of an asynchronous motor driving the steam blower are preferably determined as operating parameters of the steam blower.

The cooking appliance preferably has an evaluation device which uses the at least one detected parameter of the gas mixture and the at least one operating parameter of the vapor fan to calculate the humidity. The evaluation device is designed to receive and evaluate the measurement signals from the sensors used to record the parameters of the gas mixture or the operating parameters of the vapor blower. In addition to the temperature, the evaluation device can also take other parameters of the gas mixture, such as e.g. B. its density, take into account. In particular, characteristic curves created under defined conditions are stored in the evaluation unit for the respective cooking appliance. These characteristics can be in a form that allow a determination of the humidity with the smallest possible number of parameters of the gas mixture or operating para meters of the vapor blower, so that z. B. can be dispensed with a detection of the current pressure of the gas mixture. The evaluation unit can transmit the determined moisture value to the control device. Depending on the moisture determined, the control device can control certain components of the cooking appliance, such as the treatment device. In particular, the evaluation device is part of the control device or the control device simultaneously serves as an evaluation device. Alternatively, the evaluation device can be designed as an independent unit with a processor, a memory, communication interfaces and/or other components for electronic data processing and can be connected to the control device of the cooking appliance—wirelessly or by wire—for data transmission.

In a preferred embodiment of the invention, the fume fan is arranged in a fume duct of the cooking appliance, with the fume duct toward the cooking chamber at least has an inlet opening and at least one outlet opening towards the surroundings of the cooking appliance or towards a cooling air duct which is open towards the surroundings of the cooking appliance. In this way, the vapor blower is charged with the gas mixture under defined flow conditions, so that a more reliable humidity measurement is possible. In addition, the physical separation of the fume fan from the cooking chamber ensures that the operation of the fume fan does not cause any significant circulation of the gas mixture in the cooking chamber. The vapor duct can open into an area outside the cooking chamber, preferably in the vicinity of an outlet opening of the cooling duct, so that the gas mixture, which is usually hot, mixes with cooling air as it exits. The vapor duct can also open into the cooling air duct, which is open to the surroundings of the cooking appliance, so that the gas mixture mixes with cooling air before it is discharged into the surroundings of the cooking appliance.

If the temperature is not recorded in the immediate vicinity of the vapor extractor, i. H. if they e.g. B. is measured inside the cooking chamber by means of the temperature sensor installed on a rear wall of the muffle to regulate the cooking chamber temperature, the temperature of the gas mixture at the vapor fan may differ from the measured temperature. In a further preferred embodiment of the invention, the vapor blower is arranged closer to the at least one inlet opening than to the at least one outlet opening. This ensures that the temperature difference between the gas mixture at the vapor fan and the gas mixture at the location of the temperature measurement is minimized. Alternatively or additionally, the fume duct can be thermally insulated and/or heated at least in certain areas, in particular in a region from the at least one inlet opening to the fume fan. The fume fan is preferably arranged in the vicinity of the at least one inlet opening, i. H. at the inlet opening or immediately behind it.

The humidity is preferably regulated on the basis of the determined humidity of the gas mixture. For regulation, the currently determined moisture value can be compared with a moisture value specified by the current treatment step (target/actual comparison), with the target moisture value being specified by the operator or by the selected operating mode and/or the selected cooking program.

For regulation purposes, the cooking appliance can be equipped with a device for supplying moisture and/or a controllable device for removing moisture. The device for supplying moisture can include an evaporator, which is connected to the cooking chamber via a fluid line that can be closed with a controllable closure element. The device for removing moisture can include a controllable closure element, with which an air duct running from the cooking chamber into an area surrounding the cooking appliance can be closed. If the humidity value falls below or exceeds the specified value, the humidity of the gas mixture can be adjusted by activating the device for supplying moisture or the device for removing moisture.

In a further preferred embodiment of the invention, an air flow rate of the vapor blower is set as a function of the moisture determined. In this way, a particularly simple and reliable way of controlling the humidity is created. For example, a higher air flow rate and thus a higher air exchange rate leads to greater dehumidification and thus to a reduction in the humidity of the gas mixture in the cooking chamber. A low air flow rate, in turn, leads to less dehumidification, so that moisture, e.g. B. from the food itself, can accumulate in the gas mixture in the cooking chamber. The air flow rate can be adjusted steplessly by adjusting the speed of the vapor fan and/or by varying the angle of attack of the rotor blades of the vapor fan, so that the humidity can be precisely regulated to achieve optimal cooking results. For example, the control device can transmit specific control signals to the vapor blower as a function of the moisture determined and thus regulate its speed and/or the angle of attack of its rotor blades.

Furthermore, in this way the functions of moisture measurement and moisture control are combined in a compact component or a compact assembly, which enables a particularly simple and cost-effective implementation in different types of cooking appliances. Not only can an expensive and fault-prone humidity sensor be dispensed with. Since the vapor blower is now also used to control the humidity, other devices for controlling the humidity (such as valves, flaps and evaporators) can be dimensioned smaller or one or all of these devices can be dispensed with. For example, in an oven combination appliance with a steam cooking function (combi-steam cooker), in which moisture can be released into the cooking chamber by means of an evaporator, a moisture sensor and ventilation flaps can be dispensed with. Furthermore, in cooking appliances that are used primarily for the treatment of food to be cooked, which emit a relatively large amount of moisture during the cooking process - as z. B. is the case when baking bread or rolls - the humidity sensor and ventilation flaps as well as an evaporator are dispensed with.

In a further preferred embodiment of the invention, the recorded parameters of the gas mixture and the recorded operating parameters of the vapor blower are recorded several times in succession over a certain period of time, in particular at regular or irregular time intervals, and the humidity of the gas mixture is determined on the basis of the temperature averaged over time and the time averaged determined at least one operating parameter. There the humidity in the gas mixture in some cases reacts rather sluggishly to a variation in the air flow rate of the vapor fan, this enables reliable humidity control. For example, the recorded parameters of the gas mixture and the recorded operating parameters of the vapor fan or the resulting humidity value can be averaged over a period of at least 30 s, preferably at least 60 s, particularly preferably at least 90 s, before the air flow rate is adjusted.

The cooking appliance according to the invention has a cooking chamber for accommodating food to be cooked, a treatment device for treating the food to be cooked, a control device for controlling at least the treatment device, a vapor fan with which a gas mixture can be conveyed from the cooking chamber to an environment outside of the cooking device, and a temperature sensor for detecting a temperature of the gas mixture. The cooking appliance is characterized in that it is configured to carry out a method according to one of Claims 1 to 8.

The cooking appliance according to the invention therefore also has the advantages relevant to the method according to the invention.

Overall, the present invention provides a novel possibility for humidity control, in which both the detection and the control can be implemented inexpensively and in a particularly simple manner using just one component or assembly. It is expressly pointed out that the configurations of the invention explained above can each be combined with the subject matter of one of the independent claims either individually or in any technically meaningful combination.

Modifications and refinements of the invention as well as further advantages and details of the invention can be found in the following description of the subject matter and the undersigned statement. In the schematic figure shows:

Fig. 1 A cooking appliance according to the invention.

Individual technical features of the exemplary embodiments described below can also be combined with the exemplary embodiments described above and the features of the independent claims and any further claims to form objects according to the invention.

Fig. 1 shows a cooking appliance 2 according to the invention with a cooking chamber 4 for accommodating the cooking good 5. The cooking chamber 4 can be closed by a cooking chamber door 6. The cooking appliance 2 has a Treatment device for treating the food to be cooked 5, which in this embodiment includes a top-heating element 8, a bottom-heating element 10 below the cooking chamber floor and a circulation fan 14 equipped with a ring heater 12.

The cooking device 2 also has a control device 16 for controlling the treatment device and other components of the cooking device 2 . In addition, the cooking device 2 includes a fume fan 18 which is used exclusively to convey a gas mixture, in particular in the form of air 19 containing vapor, from the cooking chamber 4 to an environment outside of the cooking device 2 . The vapor blower 18 is driven by a controllable vapor blower motor 20 which is connected to the control device 16 in a signal-transmitting manner. The vapor blower motor 20 can be, for. B. be a brushless DC motor (BLDC).

The cooking appliance 2 has a temperature sensor 21 which is connected to the control device 16 in a signal-transmitting manner and measures the temperature of the gas mixture in the cooking chamber 4 . The cooking appliance 2 is, in particular by means of the control device 26, configured so that based on the temperature of the gas mixture and detected operating parameters of the mixture with the Gasge applied vapor blower 18, such. B. the speed and the power consumption of the vapor blower motor 20, the humidity of the gas mixture is determined. A change in the humidity in the gas mixture has a direct effect on the operating parameters of the vapor blower 18, as a result of which humidity measurement can take place in a reliable manner. The control device 16 serves as an evaluation unit, i. H. it is designed to receive and evaluate the measurement signals from the sensors and means used to record the parameters of the gas mixture or the operating parameters of the vapor blower 18 and to calculate the humidity of the gas mixture from them.

In contrast to the circulating air fan 14 , the vapor fan 18 , which has a smaller design, is not used to circulate the gas mixture in the cooking chamber 4 . Compared to a moisture measurement using a circulating air fan 14, the moisture measurement according to the present invention does not therefore have a negative effect on the cooking result. By arranging the fume fan 18 in a fume duct 24 that is accessible from the cooking chamber 4 only through an inlet opening 22 , the fume fan 18 is further shielded from the cooking chamber 4 . The vapor channel 24 is open to the surroundings of the cooking appliance 2 via an outlet opening 26 . Air 19 containing vapor is sucked into the vapor channel 24 by means of the vapor fan via the inlet opening 22 and discharged to the environment via the outlet opening 26 . The vapor blower 18 is here arranged outlet opening 26 immediately behind the inlet opening 22 and thus closer to it than to the outlet. In this way it is ensured that the temperature difference between the gas mixture at the vapor blower 18 and the gas mixture at the location of the temperature measurement is as small as possible. Alternatively, with a further from the inlet opening 22 remote arrangement of the fume fan 18, the region of the fume duct 24 in between is thermally insulated and/or heated.

The vapor fan 18 is not used to transport cooling air 28 . For this purpose, the Garge advises 2 equipped with a separate cooling fan 30, which in a conventional manner from the environment of the cooking appliance 2, z. B. through various openings in the housing of the cooking appliance 2, sucks in cooling air 28 and lets it flow past certain components of the cooking appliance 2 to be cooled. The cooling fan 30 is driven by a controllable cooling fan motor 32 which is connected to the control device 16 in a signal-transmitting manner.

The fact that the fume fan 18 and the cooling fan 30 can be controlled independently of one another has the advantage that the processes of fume removal and cooling can be optimized independently of one another for the desired operating mode.

The outlet opening 26 of the vapor channel 24 is located in the vicinity of an outlet opening 34 for the cooling air 28, so that the usually hot gas mixture is mixed with the cooling air 28 on exit.

In the present embodiment, the vapor blower 18 is not only used to detect the humidity of the gas mixture, it also serves to regulate the humidity. For this purpose, the cooking appliance 2 is configured in such a way that, depending on the humidity determined, an air conveying capacity of the vapor fan 18 is set. When the air flow rate is low, the cooking chamber 4 is dehumidified to a small extent, so that moisture from the food 5 to be cooked accumulates in the cooking chamber 4 . An increase in the air flow rate leads to greater dehumidification and thus to a reduction in the humidity of the gas mixture in the cooking chamber 4. For control, the currently determined humidity value can be compared with a humidity value specified by the current treatment step and precisely adjusted by stepless regulation of the speed of the steam blower motor 20 be adjusted to this. In the embodiment shown here, both an expensive and fault-prone humidity sensor and humidity control devices that are complicated to implement, such as ventilation flaps or evaporators, can therefore be dispensed with.

By using the vapor fan 19 both for measuring and for controlling the humidity, a simple, cost-effective and elegant way of implementing these functions in a large number of cooking appliance types is created compared to previous solutions.

In the following, cooking processes are described based on exemplary embodiments, as they can be carried out with a cooking appliance 2 according to the invention: In a first exemplary embodiment, the fume fan 18 is operated at a low speed in an initial phase, so that the fume fan 18 sucks about 5 liters of gas mixture per minute out of the cooking chamber 4 . The food to be cooked 5 is heated by the treatment device and releases water. The humidity in the gas mixture increases. A cooking phase then follows. Depending on the type and/or quantity of the item to be cooked 5, an operator of the cooking appliance 2 can specify a value for optimum moisture content through the selected operating mode and/or the selected cooking program. After reaching this optimum humidity value, the speed of the vapor blower 18 is increased so that the optimum humidity value is not exceeded. Depending on the type and/or quantity of the food 5 to be cooked and in particular the moisture release rate determined thereby, intake volumes of 15 to 30 liters of gas mixture per minute can be set. The cooking phase ends when the food 5 has reached the desired degree of doneness.

In a second exemplary embodiment, before the initial phase and the subsequent cooking phase, a browning phase is initiated, in which low humidity is ensured in the cooking chamber 4 by the high speed of the steam blower 18, while at the same time a high cooking chamber temperature is provided to prevent browning and crust formation in the food to be cooked 5 to be optimized. An initial phase and a subsequent cooking phase can then be initiated as in the first exemplary embodiment.

In a further exemplary embodiment, which is not shown in the drawings, an evaporator unit is also controlled in addition to the dehumidification capacity by the vapor fan in order to set a target humidity value in the cooking chamber. Well-known procedures are, for example, in a first step, the addition of steam when baking bread, in which almost complete water vapor saturation is achieved in the cooking chamber at the beginning of the baking process. In this first step, the vapor blower only removes a minimal amount of vapor and the evaporator ensures that the vapor is saturated. In the second baking step, the moisture content in the cooking chamber is reduced to a target value by switching off the evaporator and increasing the flow rate of the vapor fan. If this target value is reached, it is kept constant, e.g. The baking process is then often completed by a crust formation step in which another, lower target value for the cooking chamber humidity is set. The evaporator does not have to be switched on during this phase and the delivery rate of the steam blower is regulated in such a way that this target value is quickly reached and then kept constant.

Claims

patent claims

1. A method for operating a cooking appliance (2), wherein the cooking appliance (2) has a cooking chamber (4) for accommodating the food to be cooked (5), a treatment device for treating the food to be cooked (5), a control device (16) for controlling at least the treatment device and a vapor fan (18) with which a gas mixture can be conveyed from the cooking chamber (4) to an area outside the cooking appliance (2), the humidity of the gas mixture being measured indirectly using at least one recorded parameter of the cooking mixture and using at least one recorded operating parameter of the vapor blower (18) to which the gas mixture is applied is determined, the at least one recorded parameter of the gas mixture comprising at least one recorded temperature of the gas mixture.

2. The method according to claim 1, characterized in that the vapor fan (18) is arranged in a vapor channel (24) of the cooking appliance (2), the vapor channel (24) towards the cooking chamber (4) having at least one inlet opening (22) and towards Has at least one outlet opening (26) in the area surrounding the cooking device (2) or toward a cooling air duct that is open to the area surrounding the cooking device (2).

3. The method according to claim 2, characterized in that the vapor blower (18) is arranged closer to the at least one inlet opening (22) than to the at least one outlet opening (26).

4. The method according to claim 2 or 3, characterized in that the vapor duct (24) is thermally insulated and/or heated at least in regions, in particular in a region from the at least one inlet opening (22) to the vapor fan (28).

5. The method according to any one of claims 2 to 4, characterized in that the vapor blower (18) is arranged in the vicinity of the at least one inlet opening (22).

6. The method according to any one of claims 1 to 5, characterized in that in depen dence on the determined humidity, an air flow rate of the vapor blower (18) is set.

7. The method according to any one of claims 1 to 6, characterized in that the detected th parameters of the gas mixture and the detected operating parameters of the vapor blower (18) are repeatedly detected over a certain period of time and the

Humidity of the gas mixture is determined using time-averaged values of the parameters of the gas mixture mixture and the operating parameters of the vapor blower (18).

8. The method according to any one of claims 1 to 7, characterized in that to determine the humidity as operating parameters of the vapor fan (18), the speed and the power consumption of a vapor fan (18) driving vapor fan motor (20) are determined.

9. Cooking appliance (2) with a cooking chamber (4) for receiving food to be cooked (5), a treatment device for treating the food to be cooked (5), a control device (16) for controlling at least the treatment device, a vapor fan (18) with which a Gasge mixture from the cooking chamber (4) in an environment outside of the cooking device (2) can be conveyed, and a temperature sensor (21) for detecting a temperature of the Gasgemi- sches, characterized in that the cooking device (2) for carrying out a procedural rens configured according to any one of claims 1 to 8.