EP3957915A1 - Pyrolytic cleaning of a cooking appliance - Google Patents

Abstract

The invention relates to a method for pyrolytic cleaning of a cooking appliance (2) and a corresponding cooking appliance (2). The cooking appliance (2) has at least one heatable cooking space (4), a heating device for heating up the cooking space (4) and a temperature control device (12) for controlling a cooking space temperature (T). The cooking chamber (4) is heated to a pyrolysis target temperature (ZT) of between 400 °C and 600 °C in a heating-up phase (A). It is proposed that the cooking space (4) be heated to a cooking space temperature (T) of 270°C. Starting from a cooking chamber temperature (T) of 270 °C, the cooking chamber (4) should be heated to a cooking chamber temperature (T) of 350 °C at an average heating rate of 2 K/min to 4 K/min.

Description

The present invention relates to a method for the pyrolytic cleaning of a cooking appliance with at least one heatable cooking space, a heating device for heating up the cooking space and a temperature control device for controlling a cooking space temperature, the cooking space being heated to a pyrolysis target temperature of between 400° C. and 600° C. in a heating-up phase is heated. Furthermore, the invention relates to a corresponding cooking appliance.

With pyrolytic cleaning, the cooking chamber is heated to high temperatures of up to 600°C in order to break down cooking chamber contamination from baking or roasting, such as leftover food or fat residue. After the pyrolysis process, which usually lasts several hours, the dirt has turned to ash and can then be easily wiped off. In the case of cooking appliances with a pyrolysis function, there is usually no need for time-consuming manual cleaning of the cooking chamber.

A disadvantage of the previously known pyrolysis cleaning processes is that, due to the constant exchange of air between the cooking chamber and the area surrounding the cooking appliance, they are accompanied by a strong odor that is perceived as unpleasant.

It is known from the prior art to provide catalysts, in particular in an exhaust air opening of the cooking appliance, which decompose and/or burn the odorous substances escaping from the cooking chamber. However, such catalysts are primarily designed for normal cooking operation and are therefore generally not able to adequately counteract the odor pollution produced during pyrolysis.

From the EP 1 837 601 B1 a method for controlling a pyrolytic cleaning process is known, in which the heating power and consequently the cooking chamber temperature is regulated on the basis of an oxygen content within the cooking chamber. The oxygen is thereby displaced by the odorous substances which cause the odor pollution and occur, for example, in the form of vapors, gases and/or smoke, so that a low oxygen concentration correlates with a high odorous substance concentration. If the oxygen concentration falls below a certain limit, the heating output is reduced so that less dirt is burned and thus fewer odors are produced. The limit value is set in such a way that the amount of odorous substance that is still produced can be converted by the catalyst and the odor pollution is thus kept within limits.

The disadvantage of this solution is that additional sensors have to be installed in the cooking chamber and these are susceptible to malfunction and destruction due to the loads associated with the high pyrolysis temperatures.

It is therefore the object of the present invention to provide a method for the pyrolytic cleaning of a cooking appliance in which the odor load is reduced in a process-reliable manner. The method should preferably be able to be carried out without an additional sensor system. Furthermore, it is 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. The object is also achieved by a cooking appliance having the features of claim 9. Preferred features are the subject matter of the dependent claims. Further advantages and features can be found in the general description and the exemplary embodiments.

Surprisingly, it has been found that the odor pollution can be greatly reduced if, after heating the cooking chamber to a cooking chamber temperature of 270°C and starting from a cooking chamber temperature of 270°C, the cooking chamber is heated to a cooking chamber temperature of 350°C with an average heating rate of 2 K/min to 4 K/min n is heated. It has been shown that especially in the critical temperature range of 270 °C to 350 °C, particularly odor-intensive molecules, such as a large number of fat residues, are converted to a greater extent. By providing such a moderate or throttled heating stage for this critical temperature interval, the odorous substances are converted more slowly and distributed over a longer period of time, so that the odor pollution that correlates with the odorous substance concentration is reduced, with the pyrolysis process as such not being unnecessarily in the length is pulled, which would be perceived as disadvantageous by users of the device.

The slower conversion of particularly odor-intensive molecules means that the odor load in the vicinity of the cooking appliance can be better reduced through adequate ventilation. If the cooking appliance is equipped with a catalytic converter, this can better counteract odor pollution since it is overloaded less frequently or no longer due to the lower concentration of odorous substances. Ovens/stoves and combination ovens with steam cooking and/or microwave functions can be considered as cooking appliances, as can ovens with high-frequency technology.

With the present method, the pyrolysis process can be at least partially, in particular completely, controlled or regulated using preset parameters without having to rely on additional sensitive sensors, for example for detecting oxygen, smoke or other gases or aerosols. As a result, the method can be implemented in a particularly simple manner and is also optimally suited as a retrofit solution for existing cooking appliances, for example as part of a software update.

As a temperature control device in the context of this invention, a particularly known device for controlling a cooking chamber temperature is understood Having a temperature sensor for detecting the cooking chamber temperature and at least regulates the power of the heating device in such a way that the cooking chamber temperature reaches a target cooking chamber temperature. In particular, the temperature control device can be controlled via software. The temperature control device can be at least partially part of a control unit that controls the cooking appliance. Alternatively, the temperature control 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 unit of the cooking appliance—wirelessly or by wire—for data transmission.

According to a preferred embodiment of the invention, at least in the heating-up phase, the target cooking chamber temperature is increased stepwise and/or continuously at least in sections. The heating rate of the cooking chamber temperature can be set particularly easily in this way. In this case, the setpoint cooking chamber temperature is preferably lowered a first time at the latest when the cooking chamber temperature reaches 270.degree.

According to a further preferred embodiment of the invention, starting from a cooking chamber temperature of 350° C., the cooking chamber is heated to the pyrolysis target temperature at an average heating rate of 4 K/min to 7 K/min. Surprisingly, it has been found that in a further critical temperature interval from 350° C. to the pyrolysis temperature of 400° C. to 600° C., some particularly odor-intensive molecules are still converted, leading to a strong odor nuisance. However, it has been shown that due to the preceding moderate heating stage in the temperature interval from 270 °C to 350 °C, a large proportion of odor-intensive molecules have already been converted when a cooking chamber temperature of 350 °C is reached, so that heating up with a still throttled, but higher heating rate is possible. The average heating rate in the temperature interval from 350°C to the pyrolysis temperature is preferably greater than in the temperature interval from 270°C to 350°C.

According to a further preferred embodiment of the invention, the method comprises a pyrolysis holding phase in which the pyrolysis target temperature is at a substantially constant temperature between 400° C. and 600° C., preferably between 410° C. and 500° C., particularly preferably between 420 °C and 470°C. In this pyrolysis holding phase, which is run through after the moderate heating stage in the temperature range from 270°C to 350°C and in particular following a further moderate heating stage in the temperature range from 350°C up to the pyrolysis target temperature, all remaining contamination residues turn to ash burned. A large part of the critical odorous substances has already been converted in the preceding moderate heating stage(s), so that the odor pollution in the pyrolysis holding phase, which is decisive for the cleaning result, is reduced keeps within limits. The pyrolysis holding phase preferably lasts at least 15 minutes and at most 5 hours.

According to a further preferred embodiment of the invention, the cooking chamber is briefly heated one or more times in the pyrolysis holding phase to a peak temperature above the pyrolysis target temperature. This results in temperature peaks at which there is increased conversion of the contamination, which means that the pyrolysis holding phase can be shorter overall. Furthermore, in this way, time losses that can be attributed to the at least one moderate heating stage can be compensated for. In particular, it can be achieved in this way that the total duration of the pyrolysis process remains within the scope of normal process durations and does not extend noticeably. This is particularly advantageous when retrofitting existing cooking appliances, since end customers generally disapprove of longer processing times. The pyrolysis holding phase can preferably be shortened in such a way that the total duration of the pyrolysis process is reduced compared to the usual process durations. In particular, heating takes place from the pyrolysis target temperature to a peak temperature with the maximum power of the heating device. The peak temperature is preferably at least 20 K, preferably at least 50 K, particularly preferably at least 100 K, and at most 200 K above the selected pyrolysis target temperature. In particular, the peak temperature corresponds to the maximum permissible cooking chamber temperature of the cooking appliance.

According to a further preferred embodiment of the invention, starting from a starting temperature at the beginning of the heating-up phase, the cooking chamber is heated to a cooking chamber temperature of 270° C. at an average heating rate of 15 K/min to 25 K/min. In this way, the cooking chamber heats up particularly quickly in the less critical temperature range below 270°C, which minimizes the overall duration of the pyrolysis process. A starting temperature is in particular a temperature below 270° C. that is present in the cooking chamber at the beginning of the pyrolysis process. For example, the starting temperature essentially corresponds to the temperature of the surroundings of the cooking appliance if the cooking appliance has not been in operation for a long period of time. However, it can also be a higher temperature, for example following a cooking process. In particular, the heating in this initial heating phase takes place with maximum conduction of the heating device.

According to a further preferred embodiment of the invention, odors produced during the pyrolytic cleaning in the cooking chamber, which occur for example in the form of vapors, gases and/or smoke, are preferably removed by means of an odor elimination device of the cooking appliance arranged in particular in an exhaust air opening of the cooking appliance a catalyst. In this way, the odor can be counteracted particularly efficiently. Due to the lower concentration of odorous substances due to the at least one moderate heating stage, the catalytic converter is overloaded less frequently or no longer and can thus largely, in particular almost completely, decompose and/or burn the odorous substances before they are released into the environment of the cooking appliance.

The cooking appliance according to the invention has at least one heatable cooking space, a heating device for heating up the cooking space and a temperature control device for controlling a cooking space temperature. In this case, the cooking appliance is suitable and designed to carry out pyrolytic cleaning, in which the cooking chamber is heated to a pyrolysis target temperature of between 400° C. and 600° C. in a heating-up phase. The cooking appliance is characterized in that it is suitable and designed to carry out a method according to one of Claims 1 to 8.

A temperature control device in the context of this invention is understood to be a device for controlling a cooking chamber temperature, which is known per se and has a temperature sensor for detecting the cooking chamber temperature and regulates at least the power of the heating device in such a way that the cooking chamber temperature reaches a target cooking chamber temperature. In particular, the temperature control device can be controlled via software. The temperature control device can be at least partially part of a control unit that controls the cooking appliance. Alternatively, the temperature control 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 unit of the cooking appliance—wirelessly or by wire—for data transmission. For example, the cooking appliance is configured by means of the temperature control device and/or the control unit to carry out a method according to one of claims 1 to 8.

Overall, the present invention provides a novel method for pyrolytic cleaning of a cooking chamber with reduced odor pollution, which can be implemented in a particularly simple manner and is therefore also optimally suited for retrofitting existing cooking appliances.

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.

Fig. 1

Eine Skizze eines Temperatur-Zeit-Diagramms eines erfindungsgemäßen Pyrolyseverfahrens,

Fig. 2

eine Skizze eines Temperatur-Zeit-Diagramms eines weiteren erfindungsgemäßen Pyrolyseverfahrens,

Fig. 3

ein Temperatur-Zeit-Diagramm eines weiteren erfindungsgemäßen Pyrolyseverfahrens,

Fig. 4

ein erfindungsgemäßes Gargerät.

Modifications and configurations of the invention as well as further advantages and details of the invention can be found in the following specific description and the drawings. In the schematic figures show:

1

A sketch of a temperature-time diagram of a pyrolysis process according to the invention,

2

a sketch of a temperature-time diagram of a further pyrolysis process according to the invention,

3

a temperature-time diagram of another pyrolysis process according to the invention,

4

a cooking appliance according to the invention.

Parts that function in the same or a similar way are provided with identical reference numbers where appropriate.

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.

Figures 1 to 3 show temperature curves of a cooking chamber temperature T in a cooking chamber 4 of a cooking appliance 2 in various embodiments of the method according to the invention. The cooking chamber 4 is heated to a pyrolysis target temperature ZT of between 400° C. and 600° C. in a heating-up phase A by a heating device that can be controlled via a temperature control device 12 . The cooking chamber 4 is first heated to 270.degree. Starting from a cooking chamber temperature T of 270° C., the cooking chamber 4 is then heated in a first moderate heating stage M to a cooking chamber temperature T of 350° C., the average heating rate being 2 K/min to 4 K/min. In this way, the particularly odor-intensive molecules that are formed in the critical temperature range of 270 °C to 350 °C are reacted more slowly and distributed over a longer period of time.

On the other hand, heating from a starting temperature (usually room temperature) up to 270 °C can take place at much higher heating rates of 15 K/min to 25 K/min and in particular at maximum power of the heating device in order to keep the total duration of the pyrolysis process as short as possible .

Following the first moderate heating stage M, starting from a cooking chamber temperature T of 350° C., the cooking chamber 4 is heated to the pyrolysis target temperature ZT in a second moderate heating stage M' at an average heating rate of 4 K/min to 7 K/min. Since a large part of odor-intensive molecules has already been converted by the preceding first moderate heating stage M when a cooking chamber temperature T of 350 °C is reached, heating can take place at a heating rate that is still throttled, but higher than the first moderate heating stage M, without that the odor load is significantly increased.

The second moderate heating stage M' is followed by the pyrolysis holding phase H, in which the cooking chamber temperature T is at the essentially constant pyrolysis target temperature ZT between 400° C. and 600° C., preferably between 410° C. and 500° C., in particular preferably between 420°C and 470°C. Since a large part of the critical odorous substances has already been converted in the preceding moderate heating stages M, M', the pyrolysis holding phase H, which is decisive for the cleaning result, can be carried out without the odor load being significantly increased. The pyrolysis holding phase H preferably lasts at least 30 minutes and at most 5 hours.

In the embodiment according to 2 the cooking chamber 4 in the pyrolysis holding phase H is briefly heated to a peak temperature above the pyrolysis target temperature ZT. At the temperature peak S that occurs in this way, there is increased conversion of the contamination, as a result of which the pyrolysis holding phase H can be shorter overall. The peak temperature is preferably at least 20 K, preferably at least 50 K, particularly preferably at least 100 K, and at most 200 K above the selected pyrolysis target temperature ZT and corresponds in particular to the maximum permissible cooking chamber temperature T of the cooking appliance 2.

3 shows a real measurement curve of the cooking chamber temperature T over time. To regulate the cooking chamber temperature T in the first moderate heating stage M, a target cooking chamber temperature is initially maintained at 270° C. and then increased in stages, here by approx. 30 K each time. After reaching the set cooking space temperature, the cooking space temperature T still slightly exceeds it (overshooting). In the second moderate heating stage M', too, the target cooking chamber temperature is increased in stages. The target cooking chamber temperature is then kept at a constant temperature of approx. 440 °C during the pyrolysis holding phase H.

4 shows a cooking appliance 2 according to the invention in the form of an oven with a heatable cooking chamber 4. The cooking appliance 2 has a heating device which, in this embodiment, has a top-heating element 6 and a bottom-heating element 8 below the cooking chamber floor and a circulating fan 10 equipped with a ring heater. A temperature control device 12, which is part of a control unit 14 of the cooking appliance 2, is used to control the cooking compartment temperature T recorded by a temperature sensor 16 in the cooking compartment 4. The cooking appliance 2 is suitable and designed for this purpose, in particular by means of the control unit 14 and/or the temperature control device 12 configured to carry out the inventive method for pyrolytic cleaning of the cooking chamber 4. The cooking appliance 2 also has an odor elimination device (not shown here) designed as a catalyst, which is arranged in an exhaust air opening of the cooking appliance 2 and treats odors produced during the pyrolytic cleaning carried out with the cooking chamber door 18 closed. In this way, the odorous substances can be largely, in particular almost completely, decomposed and/or burned before being released into an area surrounding the cooking appliance 2 .

Claims (9)

Process for the pyrolytic cleaning of a cooking appliance (2) with at least one heatable cooking space (4), a heating device for heating up the cooking space (4) and a temperature control device (12) for controlling a cooking space temperature (T), the cooking space (4) being in a heating-up phase (A) is heated to a pyrolysis target temperature (ZT) between 400 °C and 600 °C, characterized by the following steps: - heating up the cooking chamber (4) to a cooking chamber temperature (T) of 270 °C, - starting from a cooking chamber temperature (T) of 270 °C, heating the cooking chamber (4) to a cooking chamber temperature (T) of 350 °C at an average heating rate of 2 K/min to 4 K/min. Method according to Claim 1, characterized in that at least in the heating-up phase (A) a target cooking chamber temperature is increased stepwise and/or continuously at least in sections. Method according to Claim 1 or 2, characterized in that , starting from a cooking chamber temperature (T) of 350 °C, the cooking chamber (4) is heated to the pyrolysis target temperature (ZT) at a higher heating rate of 4 K/ on average than in the heating phase (A). min to 7 K/min, is heated. Method according to one of the preceding claims, characterized by a pyrolysis holding phase (H) in which the pyrolysis target temperature (ZT) is at a substantially constant temperature between 400 °C and 600 °C, preferably between 410 °C and 500 °C , more preferably between 420 °C and 470 °C. Method according to Claim 4, characterized in that the cooking chamber (4) in the pyrolysis holding phase (H) is briefly heated one or more times to a peak temperature above the pyrolysis target temperature (ZT). Method according to one of the preceding claims, characterized in that starting from a starting temperature at the start of the heating-up phase (A), the cooking chamber (4) is heated to a cooking chamber temperature (T) of 270°C at an average heating rate of 15 K/min to 25 K/min. minutes is heated. Method according to one of the preceding claims, characterized in that starting from a starting temperature at the beginning of the heating-up phase (A), the cooking chamber (4) is heated to a cooking chamber temperature (T) of 270°C essentially at maximum power of the heating device. Method according to one of the preceding claims, characterized in that odorous substances arising during the pyrolytic cleaning in the cooking chamber (4) are treated by means of an odor elimination device of the cooking appliance, in particular a catalytic converter. Cooking appliance (2) with at least one heatable cooking space (4), a heating device for heating up the cooking space (4) and a temperature control device (12) for controlling a cooking space temperature (T), the cooking device (2) being suitable and designed for this purpose, a pyrolytic Carry out cleaning in which the cooking chamber (4) is heated to a pyrolysis target temperature (ZT) of between 400 °C and 600 °C in a heating-up phase (A), characterized in that the cooking appliance (2) is suitable and designed for this purpose, to carry out a method according to any one of claims 1 to 8.

Images