DE102008008020B4 - Method for identifying error events in a cooking appliance with at least one nozzle and cooking appliance for carrying out such a method - Google Patents

Abstract

Method for identifying error events in a cooking appliance with at least one nozzle for injecting at least one fluid into an interior of the cooking appliance and at least one sensor for detecting measured values that are characteristic of the state of the nozzle in the interior, comprising the following steps:
- carrying out several condition checks, each of which records a temporal reaction of at least the measured value to at least one nozzle activity, for the same nozzle one after the other at certain time intervals;
- determining the condition of the nozzle as a result of the condition check depending on a characteristic quantity selected from at least one of the measured values;
- Saving the states as a state history in a memory of a control unit of the cooking appliance;
- Tracking the temporal development of the states based on the state history; and/or
- Perform multiple condition checks on different nozzles simultaneously
- Determining the condition of the respective nozzles as a result of the condition check depending on a characteristic value selected from at least one of the measured values;
- comparing the resulting states with each other; and identifying candidate fault events based on the state history of the health checks of the same nozzle and/or different fault events based on comparing multiple simultaneous health checks on different nozzles.

Description

The present invention relates to a method for identifying error events in a cooking appliance according to the preamble of patent claim 1 and a cooking appliance for carrying out such a method.

Cooking appliances, particularly for commercial kitchens, which can be operated with hot air, steam or in combination with hot air and steam, can work using a steaming nozzle to steam the food being cooked and a quenching nozzle to quench or condense hot steam and fumes, and are well known to experts. A steaming or quenching process usually requires at least a partial transfer of water from its liquid to its vaporous state. Depending on the hardness of the water, more or less pronounced calcification of the steaming and quenching nozzles and their supply lines can be observed. This calcification can significantly impair the functionality of the steaming or quenching nozzle.

Thus, the genre-forming DE 102 13 014 B4 a device and a method for monitoring the degree of clogging of a steam nozzle in a cooking chamber of a cooking appliance. Accordingly, the degree of clogging can be determined by recording the temporal progression of the temperature and/or humidity in the cooking chamber using suitable sensors during and/or after a steam burst. From the data obtained in this way, the gradient of the temperature drop and/or rise after the start of steaming is determined in a recording and evaluation unit of the cooking appliance. A slight gradient of the temperature drop or a temperature rise is an indication of the presence of an at least partially clogged or calcified steam nozzle. In the recording and evaluation unit, the determined gradient of the temperature drop and/or rise is compared with a predetermined reference value, whereby if a certain deviation from the reference value is exceeded, a signal is transmitted to a display unit of the cooking appliance, which, for example, triggers an optical or acoustic warning signal. Also proposed is the DE 102 13 014 B4 a method for decalcifying a humidification nozzle, which in particular comprises the use of ultrasonic waves.

In the unpublished EN 10 2007 05 9614 A method is described for checking the degree of clogging of a nozzle arrangement of a cooking appliance, in which the time for carrying out a condition check of a nozzle arrangement, in particular a steaming nozzle arrangement, is determined depending on the usage behavior of the nozzle, the cooking chamber temperature, the humidity in the cooking chamber, the degree of hardness and the pressure of the water applied to the nozzle, in order to reduce unnecessary calcification of the nozzle due to too frequent condition checks.

In addition, devices and methods are known from the prior art in which the reaching of a limit value for detecting calcification of a household appliance is monitored.

The DE 44 04 152 A a malfunction evaluation circuit for electrical devices. The malfunction evaluation circuit comprises a sensor unit that detects the operating functions of an electrical device to be monitored, as well as a memory unit, a display device and a counter circuit. The counter circuit adds up the measured values of the sensor unit and compares them with a predetermined fixed value stored in the memory unit. If the value of the counter circuit, for example a number of switching-on processes of a heating device of the electrical device that can be attributed to calcification of the heating device, exceeds the fixed value, a warning signal is issued.

In a similar way, the DE 199 60 497 A1 , which discloses a container for heating water. The container for heating water comprises a temperature sensor which is arranged in the area between a radiator and an interior of the container into which the water is introduced. The signal from the temperature sensor is compared with a fixed temperature value and as soon as this fixed temperature value is exceeded, it is concluded that the container is calcified.

Finally, the DE 36 29 662 A1 a control circuit of an electric instantaneous water heater. In order to avoid a time delay when heating water that flows through the instantaneous water heater and to avoid unnecessary water consumption, it is proposed that a delayed switching on of a radiator of the instantaneous water heater be limited to certain individual situations. It is proposed that after an initial application and after a failure of an operating voltage, a microprocessor only switches the radiators on after a delay time during the first subsequent tapping process.

The disadvantage of this state of the art is that such a condition check of the Although the degree of clogging or calcification of the nozzle can be determined, other possible error events that can occur during the generation or measurement of a steaming or extinguishing pulse cannot be detected. Examples of this include damage to the water supply line to the nozzle, incorrect installation of the nozzle and calcification of a temperature sensor involved.

It is the object of the present invention to further develop the generic method in such a way that the disadvantages of the prior art are overcome. In particular, a method is to be provided which enables the identification of as many error events as possible in a cooking appliance in a simple and cost-effective manner.

This object is achieved by the characterizing features of patent claim 1

Subclaims 2 to 19 relate to advantageous developments of the method according to the invention.

The invention also provides a cooking appliance according to patent claim 20, with patent claims 21 to 24 claiming further developments of this cooking appliance.

The present invention is therefore based on the surprising finding that by comparing at least two condition checks, additional information is available about a possibly faulty behavior of a nozzle and/or a sensor for recording measured values that are characteristic of the condition of the nozzle, whereby this information serves to identify various error events.

Such identification can be achieved by carrying out several status checks on the same nozzle one after the other at specific time intervals and storing the states, which represent the results of the status checks, as a so-called status history in a memory of a control unit of a cooking appliance. The status history can thus be used to track the temporal development of the states, which in the event of an error event enables the limitation and/or identification of possible error events.

On the other hand, identification of different error events can also be achieved by performing several condition checks on different nozzles simultaneously and comparing the resulting conditions.

When used in parallel, both variants lead to very reliable detection of the origin of an error.

As part of a status check, the temporal progression of at least one measured value, selected from a temperature value and/or a humidity value, is recorded, with the measured value being recorded in an interior of the cooking appliance, i.e. in particular in a cooking chamber, blower chamber, steam generator housing and/or in a quenching chamber of the cooking appliance using suitable sensors. The term interior here therefore refers to the interior of hollow spaces in the cooking appliance, which can also be attached to the outside of the cooking appliance, for example.

The result of the condition check, i.e. the condition, is determined depending on at least one characteristic variable. The characteristic variable is selected from at least one measured value and/or from at least one point in time, at least one gradient and/or a temporal derivative of a measured value during a drop in the measured value, in particular after the start of nozzle activity, and/or at least one extreme value of a measured value and/or a respective associated first point in time, wherein the at least one extreme value is reached in particular after the start or after the end of nozzle activity, and/or at least a second point in time, at least one gradient and/or a temporal derivative of a measured value during a rise in the measured value, in particular after the end of nozzle activity.

By storing a large number of states in the form of a state history, especially on a regular basis, the temporal development of any errors that may occur during operation of a nozzle can be tracked. This temporal development can often be read directly from the temporal development of characteristic variables.

For example, calcification of a nozzle in response to nozzle activity can be identified by the fact that the maximum temperature drop continuously decreases from one condition check to the next, while analogously in the case of calcification of a temperature sensor there is a continuous shift in the time of the maximum temperature drop relative to the start of nozzle activity to longer times.

In contrast, other fault events such as a lime fracture in a water Supply line to a nozzle or a break in the supply line mentioned, which both occur abruptly and essentially completely prevent the flow of fluid through the nozzle. Such an error can typically only be remedied by actively intervening in the cooking appliance. When comparing several status checks within a status history, this error event is characterized by the fact that the temperature no longer drops at all in response to nozzle activity, ie that the maximum temperature drop drops abruptly to zero and initially remains at this value for an indefinite period of time.

It is also possible to identify error events that produce characteristic values that fluctuate over time when several status checks are carried out one after the other. An example of this is the temporary appearance of air bubbles in a water supply network to which the cooking appliance and thus the pipe system leading to the nozzles is connected.

• 1 einen vertikalen Schnitt durch ein Gargerät zur Durchführung eines erfindungsgemäßen Verfahrens;
• 2a einen zeitlichen Verlauf einer normierten Garraumtemperatur und einer Feuchte als Reaktion auf einen Beschwadungsstoß für einen fehlerfreien Fall;
• 2b einen zeitlichen Verlauf einer normierten Garraumtemperatur und einer Feuchte als Reaktion auf ein Beschwadungsintervall, welches vier einzelne Beschwadungsstöße umfasst, für einen fehlerfreien Fall;
• 3 einen zeitlichen Verlauf einer normierten Ablöschtemperatur als Reaktion auf einen Ablöschstoß für den fehlerfreien Fall;
• 4a einen zeitlichen Verlauf einer normierten Garraumtemperatur mit reduziertem Temperaturabfall als Reaktion auf einen Beschwadungsstoß;
• 4b einen zeitlichen Verlauf einer Ablöschtemperatur mit reduziertem Temperaturabfall als Reaktion auf einen Ablöschstoß;
• 5a eine Zustandshistorie der relativen maximalen Abfälle einer normierten Garraumtemperatur und einer normierten Ablöschtemperatur aus 11 monatlich ausgeführten Zustandsüberprüfungen;
• 5b eine Zustandshistorie analog zu 5a, jedoch aus 11 täglich ausgeführten Zustandsüberprüfungen;
• 6a einen zeitlichen Verlauf der normierten Garraumtemperatur mit verschwindendem Temperaturabfall als Reaktion auf einen Beschwadungsstoß;
• 6b einen zeitlichen Verlauf der normierten Ablöschtemperatur mit verschwindendem Temperaturabfall als Reaktion auf einen Ablöschstoß;
• 7a eine weitere Zustandshistorie analog zu 5b;
• 7b eine andere Zustandshistorie analog zu 5b;
• 8a einen zeitlichen Verlauf einer normierten Garraumtemperatur mit verlängerter Antwortzeit als Reaktion auf einen Beschwadungsstoß;
• 8b einen schematischen zeitlichen Verlauf einer normierten Ablöschtemperatur mit verlängerter Antwortzeit als Reaktion auf einen Ablöschstoßstoß; und
• 9 eine Zustandshistorie der Zeitdifferenz zwischen dem Zeitpunkt eines maximalen Temperaturabfalls einer Garraum- oder Ablöschtemperatur und dem Beginn eines Beschwadungs- oder Ablöschereignisses aus 11 monatlich ausgeführten Zustandsüberprüfungen.

Further features and advantages of the invention will become apparent from the following description, in which embodiments of the invention are explained in detail using schematic drawings, by way of example.

• 1 a vertical section through a cooking appliance for carrying out a method according to the invention;
• 2a a time course of a standardized cooking chamber temperature and humidity in response to a steaming shock for a fault-free case;
• 2 B a time course of a standardized cooking chamber temperature and humidity in response to a humidification interval comprising four individual humidification pulses, for a fault-free case;
• 3 a time course of a normalized quenching temperature in response to a quenching shock for the fault-free case;
• 4a a temporal progression of a standardized cooking chamber temperature with reduced temperature drop in response to a steaming shock;
• 4b a time course of a quenching temperature with reduced temperature drop in response to a quenching shock;
• 5a a status history of the relative maximum drops in a standardised cooking chamber temperature and a standardised extinguishing temperature from 11 monthly status checks;
• 5b a status history analogous to 5a , but from 11 condition checks carried out daily;
• 6a a temporal progression of the standardized cooking chamber temperature with a vanishing temperature drop in response to a steam burst;
• 6b a time course of the standardized quenching temperature with vanishing temperature drop in response to a quenching shock;
• 7a another state history analogous to 5b ;
• 7b another state history analogous to 5b ;
• 8a a temporal progression of a standardized cooking chamber temperature with an extended response time in response to a steaming pulse;
• 8b a schematic temporal progression of a standardized quenching temperature with extended response time in response to a quenching shock; and
• 9 a status history of the time difference between the time of a maximum temperature drop of a cooking chamber or extinguishing temperature and the start of a steaming or extinguishing event from 11 monthly status checks.

In 1 a cooking appliance 1 for carrying out a method according to the invention is shown. The cooking appliance 1 comprises a cooking chamber 2 which is delimited by cooking chamber walls 3, a cooking chamber floor 4 and a flow guide plate 5. The flow guide plate 5 separates the cooking chamber 2 from a fan chamber 10 which is delimited by a fan chamber wall 6 opposite the flow guide plate 5 and comprises a fan wheel 14 for generating a recirculation mode. The said fan wheel 14 is mounted on an axle 15 which is guided through the fan chamber wall 6 and can be driven by a motor 16. When the fan wheel 14 is running, cooking chamber atmosphere is sucked from the cooking chamber 2 into the fan chamber 10 via a central opening 17 of the flow guide plate 5, in order to then be accelerated radially outwards by the rotating fan wheels 14 and then guided back into the cooking chamber 2 via outer recesses 18 of the flow plate 5, namely after passing a heater 19 arranged around the fan wheel 14.

A humidification nozzle 20 is attached laterally to the blower chamber wall 6 at a distance from the axis 15 of the blower wheel 14, whereby the spray direction V ₁ in the case of a correctly mounted Nozzle 20 points radially inwards towards the axis 15 of the fan wheel 14 and thus also in the direction of the heater 19. The steam nozzle 20 is supplied with water via a controllable valve 22 and a supply line 24, which in turn is connected to a main line 26 of a water network. With the help of the valve 22, which is operatively connected to a control unit 50 via a control line 23, well-dosed steam jets can be sprayed from the steam nozzle 20 in the direction of the fan wheel 14 and the heater 19. The rotation of the fan wheel 14 additionally atomizes the water droplets of the steam jet, and then they are carried along into the cooking chamber 2 with the circulating air flow of the cooking chamber atmosphere. When the heater 19 is switched on, steam is also generated. The temperature of the cooking chamber atmosphere can be adjusted via the heater 19 and can be measured by means of a temperature sensor 28, which is connected to the control unit 50 via a measuring line 29. The cooking chamber atmosphere in the cooking chamber 2 can also be supplied with steam to generate humidity in the cooking chamber 2, for example by steaming using the nozzle 20 and the heater 19 switched on, as already mentioned, or by means of a steam generator with a steam generator housing 40, from which steam is fed into the cooking chamber 2 or the blower chamber 10 via a steam generator nozzle 41. The steam generator is operatively connected to the control unit 50 via a control line 42, so that the amount of steam generated can be controlled by the control unit 50. The humidity generated in this way in the cooking chamber 2 can be measured by means of a humidity sensor (not shown) that communicates with the control unit 50.

The cooking chamber 2 opens into a drain 30 at the lowest point of the cooking chamber floor 4, the cooking chamber floor 4 being sloping towards the drain 30 to facilitate the drainage of liquids from the cooking chamber 2 into the drain 30. The cooking chamber 2 is connected to a quenching chamber 31 via the drain 30. The quenching chamber 31 serves to condense vapors and fumes escaping from the cooking chamber 2 by means of a quenching nozzle 32 mounted on a wall of the quenching chamber 31, so that liquids are led from the quenching chamber 31 via a drain 38 into a sewage pipe network (not shown), whereby gases and/or air can enter the ambient atmosphere via a vent pipe 39. To extinguish the hot vapors and fumes, an extinguishing nozzle 32 is used, which is supplied with water via a controllable valve 33 and a supply line 34 that is connected to the main line 26. The valve 33 is connected to the control unit 50 via a control line 35. If the extinguishing nozzle 32 is correctly installed, its spray direction V ₂ is perpendicular to the wall of the extinguishing chamber 31 in which the nozzle is installed, as well as to the longitudinal axis of the drain 30. A temperature sensor 36 is used to measure the temperature in the extinguishing chamber 31, which is also operatively connected to the control unit 50 via a measuring line 37. Depending on the extinguishing temperature measured in this way, the control unit 50 controls the activity of the extinguishing nozzle 32 so that, for example, if the temperature in the extinguishing chamber 31 is too high, ie if hot vapors and steam are present, the control unit 50 triggers an extinguishing pulse in order to condense the hot vapors and steam and to discharge them via the drain 38 and the vent pipe 39. In addition, it can be provided that the main line 26 supplies the steam generator with water via a supply line (not shown).

However, a quenching chamber is not limited to an embodiment according to 1 limited, but can also be designed, for example, as a floor pan arranged beneath the cooking chamber 2, wherein an extinguishing nozzle is used within the floor pan to extinguish hot vapors and fumes discharged from the cooking chamber 2. Other alternative embodiments of the extinguishing chamber are also conceivable.

The control unit 50 is preferably a microprocessor or computer. This microprocessor or computer is able to register temperature and/or humidity values, in particular actual values measured by temperature and/or humidity sensors of the cooking device, and to compare them with preset reference values, in particular target values. Furthermore, the microprocessor or computer can be set in such a way that the extent of the changes in temperature and/or humidity over the duration of a cooking process can be determined and compared with corresponding reference values.

In the following, in connection with the 2a to 3 The effects of steaming and extinguishing pulses on the measured values of the cooking appliance are initially explained for the ideal case, ie for the case in which all elements of the cooking appliance involved in the implementation and measurement of the steaming and extinguishing process are functioning perfectly.

When the steaming of the cooking chamber 2 begins, the actual cooking chamber temperature, which is for example in the range of about 130° to 260° C, drops more or less depending on the intensity and duration of the steaming and generally levels off at an essentially constant temperature level after a certain period of time. After the steaming has ended, the actual cooking chamber temperature, which is for example in the range of about 130° to 260° C, drops more or less depending on the intensity and duration of the steaming and generally levels off at an essentially constant temperature level after a certain period of time. The actual cooking chamber temperature rises again during the cooking process. This behavior can be determined by 2a This figure shows a standardized cooking chamber temperature GT* = GT _Ist / GT _Soll , which is formed from the quotient between the respective actual cooking chamber temperature GT _Ist and a target cooking chamber temperature GT _Soll , as a function of time t as a reaction to a steaming pulse. The function BD shown as a dotted line represents the nozzle activity of the steaming nozzle and takes the value 1 when the valve 22 of the steaming nozzle 20 is open, and the value 0 when the said valve 22 is closed. The actual cooking chamber temperature GT _Ist is determined using the 1 shown cooking chamber temperature sensor 28. In 2a It can be seen that after the start of the steaming pulse at time t ₀ and before its end at time t _1, the standardized cooking chamber temperature GT* drops and after the end of the steaming process it reaches a minimum value GT* - ΔGT*, which is reached at time t _2. The standardized cooking chamber temperature GT* then rises again and approaches its original value as time t progresses, which it had before the start of the steaming process for t < t _0. The maximum temperature drop ΔGT* is given by the distance between the two horizontal dash-dotted lines in 2a , where the time t ₂ for reaching the maximum temperature drop is given by the vertical dash-dotted line.

An exemplary course of the humidity F in response to a steaming shock is also shown in 2a shown as a dashed line as a function of time t. For example, before the start of a steaming process at t < t _0, the moisture content F of the cooking chamber atmosphere can be a = 45%. Shortly after the start of the steaming process at time t ₀ , the moisture increases due to the evaporation of at least some of the water droplets sprayed into the cooking chamber by the steaming nozzle. After the end of the steaming process at time t ₁ , the moisture F approaches a constant value b = 62%, for example. In addition, the moisture F can also be influenced by the activity of the steam generator.

This in 2a The humidification event shown comprises a humidification pulse of duration t ₁ - t ₀ . Alternatively, a humidification event can also comprise several humidification pulses that are carried out in quick succession and that can be combined into a so-called humidification interval. In 2 B is in a similar way as in 2a a humidification process is shown, where instead of the individual humidification pulse of duration t ₁ - t ₀ according to 2a a steaming interval of duration t _1' - t _0' comprising four equal length and equidistant individual steaming pulses is used to steam the cooking chamber. All sizes not further specified here are analogous to 2a defined. In a similar way to 2a the temporal behavior of the standardized cooking chamber temperature GT* and the humidity F is determined by the duration t _1' - t _0' of the entire humidification event, whereby the duration of the individual humidification pulses of the humidification interval and their respective distances from one another also have an influence on the temporal courses of the aforementioned quantities GT* and F.

The temporal behavior of the temperature in the extinguishing chamber 31 in response to an extinguishing impact with the extinguishing nozzle 32 also provides information about the functionality of the elements of the cooking appliance 1 involved in the extinguishing event. For example, in 3 a standardized quenching temperature AT* is shown as a function of time t as a reaction to a quenching pulse of the quenching nozzle for the error-free case. The standardized quenching temperature AT* = AT _Ist /AT ₀ is calculated from the quotient of the actual quenching temperature AT _Ist measured by the quenching temperature sensor 36 and a standardized temperature AT ₀ , which can be around 80° C, for example. The activity of the quenching nozzle 32 is in 3 as a function AD by a dotted line. The function AD takes the value 1 when the valve 33 of the extinguishing nozzle 32 is open and the value 0 when the valve 33 is closed. After the extinguishing event begins at time t ₃ , the standardized extinguishing temperature AT* drops to a minimum value AT* - ΔAT* until the end of the extinguishing event at time t _4. After that, the standardized extinguishing temperature AT* typically rises again to its original value before the extinguishing event began at time t _3. In a similar way to 2a and 2 B is in 3 the maximum temperature drop of the standardized quenching temperature AT* is represented by the distance ΔAT* between two dashed horizontal lines, whereby the time t ₅ for reaching the maximum temperature drop is represented by the vertical dashed line.

In general, depending on the food, load and cooking process, much more complicated temporal progressions of the humidity and the cooking chamber temperature in response to a steaming event and/or a quenching event are possible compared to the 2a to 3 possible.

1. 1. Eine schleichende Verstopfung oder Verkalkung der Beschwadungsdüse oder der Ablöschdüse;
2. 2. eine falsch montierte Beschwadungs- oder Ablöschdüse;
3. 3. ein Kalkbruch in der Wasser-Zuleitung zur Beschwadungs- oder Ablöschdüse;
4. 4. ein Ausfall der Wasser-Zuleitung zur Beschwadungs- oder Ablöschdüse;
5. 5. zeitweise auftretende Luftblasen im Wasserleitungsnetz;
6. 6. eine Verkalkung des Beschwadungs- oder Ablöschtemperatursensors; und/oder
7. 7. ein Ausfall der Wasser-Hauptleitung oder des Wasseranschlußnetzes.

The 2a to 3 The ideal temporal behavior of the cooking chamber temperature, humidity and extinguishing temperature described changes if one or more of the people involved in the implementation and measurement of the steaming and extinguishing processes may be impaired in their functionality by an error event. The following error events are possible:

1. 1. A gradual blockage or calcification of the humidification nozzle or the extinguishing nozzle;
2. 2. an incorrectly installed humidification or extinguishing nozzle;
3. 3. a limescale deposit in the water supply line to the steaming or extinguishing nozzle;
4. 4. a failure of the water supply line to the humidification or extinguishing nozzle;
5. 5. temporary air bubbles in the water supply network;
6. 6. calcification of the steaming or extinguishing temperature sensor; and/or
7. 7. a failure of the main water line or the water supply network.

The above-mentioned error events can be distinguished by tracking the status history of at least one nozzle of the cooking appliance stored in the control unit of the cooking appliance. The maximum temperature drops ΔGT ₀ *, ΔAT ₀ * for the error-free case can be used as reference or target values.

4a shows analogous to 2a the temporal progression of the standardized cooking chamber temperature GT* (solid line) as a reaction to a steaming surge BD for a faulty case. Additionally shown is the corresponding progression of the standardized cooking chamber temperature GT* ₀ for the fault-free case (dashed line) analogous to 2a . Out of 4a it can be seen that the maximum temperature drop ΔGT* is reduced compared to the maximum temperature drop ΔGT ₀ * in the error-free case and occurs at an earlier time t ₂ . This behavior suggests a reduced flow of water through the humidification nozzle 20 during the humidification process.

An Indian 4a The temporal progression of the standardized cooking chamber temperature GT* shown with a reduced, but not zero, maximum temperature drop ΔGT* can occur in the case where the steam nozzle 20 is partially blocked, for example by calcification. In this case, a smaller amount of water is injected into the cooking chamber 2 due to the reduced flow of water during the steaming pulse. The quantities ΔGT* as well as ΔAT* thus represent characteristic quantities that are characteristic of the state of a nozzle. This behavior of the cooking chamber temperature as a reaction to a steaming pulse is already known from the DE 102 13 014 B4 known.

The 4a However, the course shown could also be caused by an incorrectly installed steam nozzle 20. In this case, the steam nozzle 20 typically no longer sprays optimally into the fan wheel 14 in the spray direction V ₁ , so that the water droplets of the steam jet are no longer completely transported into the cooking chamber 2, cf. 1 In particular, if the humidification nozzle 20 is incorrectly installed, the injected water can pass through the cooking chamber floor 4 directly into the drain 30 without evaporating and thus contributing to a drop in the cooking chamber temperature.

Analogous to 4a is in 4b a status check of the extinguishing nozzle 32 is shown in the case of a partially blocked extinguishing nozzle, for example due to calcification, or incorrectly mounted. The status check of the extinguishing nozzle 32 is to be understood here as the measurement of the temporal progression of the standardized extinguishing temperature AT* in response to an extinguishing shock, which is determined by the function AD in 4b which is already associated with 3 was defined. Here too, the maximum temperature drop ΔAT* is reduced compared to the maximum temperature drop ΔAT* ₀ in the error-free case (dashed line), but not vanishingly so. Incorrect assembly of the extinguishing nozzle 32 means that the water injected into the extinguishing chamber 31 in the direction of V ₂ no longer contributes optimally to extinguishing hot vapors and fumes and possibly less water or water droplets are sprayed directly onto the extinguishing temperature sensor 36, so that a reduced temperature drop ΔAT* takes place at the extinguishing temperature sensor 36, cf. 1 .

The two condition checks of the humidification nozzle 20 ( 4a) and the extinguishing nozzle 32 ( 4b) is that a reduced temperature drop ΔGT*, ΔAT* compared to the fault-free state of the nozzle indicates a reduced efficiency of the respective nozzle, which will vary depending on the nature of the error (clogging or incorrect assembly). Therefore, no clear statement about the underlying error event can be made based on just one condition check.

A clear assignment to a specific error event can be made by comparing several consecutively performed status checks of the respective nozzle in order to determine the temporal progression of the error to be able to make a statement about the error event.

For this purpose, 5a and 5b exemplary embodiments of a state history in the form of temporal progressions of the relative maximum temperature drop δGT* = ΔGT* / ΔGT* ₀ or δAT* = ΔAT* / ΔAT* ₀ of a total of 11 state checks, which are plotted over time T. Based on the 5a and 5b The previously mentioned error events (calcification, incorrect assembly) can now be distinguished from the status history for a humidification or extinguishing nozzle.

In 5a It can be seen that starting from a nozzle that initially functions perfectly with a relative maximum temperature drop of 1, a gradual or continuous reduction in the relative maximum temperature drop takes place. It is assumed here that a condition check of the respective nozzle takes place once a month, since calcification takes place on a relatively slow time scale.

5b shows another condition history, in which 11 condition checks were carried out on a steaming or extinguishing nozzle at intervals of one day. The diagram is analogous to the 5a the relative maximum temperature drop over time T. After an initial relative temperature drop of 1, after the fifth day there is an abrupt reduction in the relative temperature drop to approximately 60% of the initial value. In this case, the condition history can be interpreted as meaning that after the condition check on the fifth day, the humidification or extinguishing nozzle was incorrectly installed by an operator or service technician and thus optimal injection of the nozzle is no longer guaranteed.

In the 6a and 6b status checks for the humidification nozzle 20 and for the extinguishing nozzle 32 are shown in the event of a failure of the water supply line 24, 34 of the respective nozzle, see also 1 . The sizes shown are analogous to the 4a and 4b defined, i.e. solid line for error case and dashed line for error-free case. In the cases of solid lines according to 6a and 6b no more water passes through the respective nozzle during a steaming or extinguishing process. Accordingly, there is no drop in temperature of the standardized cooking chamber temperature GT* or standardized extinguishing temperature AT* in response to a steaming or extinguishing pulse. The 6a and 6b However, the condition checks shown could be caused either by a sudden failure of the water supply line, for example due to a limescale break in the water supply line, or by temporary air in a possibly unreliable water supply network to which the cooking appliance is connected for a long time. Another possibility would be that the respective nozzle is completely calcified, which corresponds to the 5a shown nozzle condition after 11 days.

Here too, a distinction between the error events mentioned is possible by taking into account the status history, as in 7a and 7b A fault signature for a sudden failure of the water supply to a nozzle can be identified by the relative maximum temperature drop δGT*, δAT* suddenly dropping to zero. In 7a Such an error event would have occurred between the condition checks on the fifth and sixth day. This is a long-term error that must be resolved through active intervention. In contrast, air bubbles in a water supply network can appear temporarily and then disappear again. This provides an error signature in a condition history, such as in 7b Here it can be seen that air bubbles appeared during the measurements on the fifth and ninth day, but disappeared again on the following day. Thus, by comparing the condition history of the condition checks according to 7a and 7b a clear assignment of the respective error event (failure of the water supply line, temporary air bubbles in the water connection) can be achieved. If air bubbles are detected in the water connection network in the manner described above and do not disappear quickly, this error event can be actively remedied by releasing air from the water connection network by opening at least one nozzle valve of a nozzle. A subsequent status check can be used to check whether the error event mentioned has actually been remedied.

Analogous to 4a and 4b show the 8a and 8b the condition checks of the steam nozzle 20 in the case of a calcified cooking chamber temperature sensor 28 ( 8a) and the extinguishing nozzle 32 in the case of a calcified extinguishing temperature sensor 36 ( 8b) . In comparison to the error-free condition check GT ₀ *, AT ₀ * shown in dashed lines, the respective maximum temperature drop ΔGT*, ΔAT* is essentially the same, although the time t ₂ or t ₅ at which the maximum temperature drop is reached is shifted to longer times t. This behavior can be explained by the fact that a layer of limescale forms over the temperature sensors due to calcification, which on the one hand shields the temperature sensor from its environment and on the other hand reduces the heat capacity. ity of the respective temperature sensor. This results in a generally slower response of the temperature sensor. As can be seen from the 8a and 8b As can be seen, the standardized cooking chamber temperature GT* or the standardized extinguishing temperature AT* will therefore fall more slowly in response to a steaming or quenching pulse, reach its minimum at a later time t ₂ and also rise again more slowly. Depending on the load in the cooking chamber and the type of food being cooked, the time t ₂ may also be shifted without a fault event having preceded a steaming nozzle.

In order to be able to clearly identify calcification of a temperature sensor, it can be helpful to look at the condition history of the steaming or extinguishing nozzle. 9 a status history in the form of a time difference (t ₂ - t ₀ ), (t ₅ - t ₃ ) between the time of the maximum temperature drop t ₅ , t ₂ and the beginning of the steaming or extinguishing event t ₀ , t ₃ plotted as a function of time T over 11 months, with a status check taking place once a month. While the respective temperature sensors are still completely free of calcification during the status check on the first day, the respective time interval (t2 - t0), (t5 - t2) increases gradually or continuously from approx. 30 seconds to approx. 40 seconds after eleven months. In a similar way to 5a Thus, a gradual change in a characteristic parameter of a nozzle condition check can indicate the occurrence of calcification.

It is also possible to detect incorrectly installed humidification or extinguishing temperature sensors, which, however, produce similar error signatures as incorrectly installed humidification or extinguishing nozzles, cf. 5b . First of all, these error events have in common that after their occurrence they result in an abrupt change in the maximum temperature drop ΔGT*, ΔAT*, which would be recognizable in a status history. To distinguish a mismounted nozzle from a mismounted temperature sensor, the exact geometry can be taken into account, compare 1 , the cooking chamber 2, the quenching chamber 31 and the exact positions of the temperature sensors 28, 36 as well as those of the respective nozzle 20, 32 provide a distinguishing criterion. Since the spray direction V ₁ , V ₂ changes when the nozzle is incorrectly installed, the geometric path of the water droplets to their location will also change. The changed path also results in a change in the travel time of the water droplets to their location, depending on the spray speed of the nozzle, the water pressure applied to the nozzle and the effective speed of spread of the water droplets in the cooking chamber or in the quenching chamber. From the time the nozzle is incorrectly installed, this effect leads to an abrupt shift in the time interval between the time of the maximum temperature drop and the start of the humidification or quenching event in a state history. In contrast, such a time shift does not occur with an incorrectly installed temperature sensor because it does not cause any change in the travel time of the water droplets. By taking into account two characteristic quantities (δGT* and (t ₂ - t ₀ ) or δAT* and (t ₅ - t ₃ ) in a state history, a distinction can be made between two error events (incorrect assembly of a nozzle, incorrect assembly of a temperature sensor).

In addition to tracking characteristic variables over time in a nozzle's status history, additional error events can be identified by performing status checks on several nozzles of a cooking appliance simultaneously and then comparing them with each other. 1 As can be seen, for example, a failure of the main water line 26, which causes a malfunction in both the humidification nozzle 20 and the extinguishing nozzle 32, can be distinguished from a failure of a single water supply line 24, 34, if the very unlikely case of the simultaneous failure of several water supply lines 24, 34 is disregarded.

An additional limitation of the error event can be achieved by taking into account the fluid flow through the individual fluid lines, in particular the main fluid line 26 or the nozzle feed lines 24, 34, and/or the pressure of the fluid in at least one of the fluid lines 24, 26, 34 mentioned. At least one flow sensor or pressure sensor can be attached to at least one fluid line, which records a flow measurement value, in particular determined from the fluid volume per unit of time, or a pressure measurement value and makes it available to the control unit 50 for further processing via a measuring line. The flow measurement values or pressure measurement values obtained in this way can also be stored in a memory of the cooking appliance as part of a corresponding status history, whereby the status here refers to the status of the respective fluid line. For example, if the 1 shown nozzle supply line 24, 34 and on the fluid main line 26, a flow sensor (not shown in 1 shown), the simultaneous failure of the two nozzle feed lines 24, 34 can be distinguished from a failure of the main fluid line 26. In this case, the state histories of the two nozzle feed lines 24, 34 would show an abrupt drop of the flow to zero. This would in turn affect the status history of the fluid main line 26 as a reduced flow. However, since the fluid main line 26 typically also supplies other components of the cooking appliance with water (in 1 not shown), such as the steam generator, it will continue to have a non-zero flow. In this way, failure of the main fluid line 26 can be excluded.

Depending on the design and loading of the cooking appliance, there may be a correlation between the characteristic values of a status check on a nozzle and the simultaneous activity of other nozzles. This is typically the case when checking the status of an extinguishing nozzle if the cooking chamber is steamed by a steaming nozzle during or shortly before the extinguishing process. The hot vapors caused by the steaming process can thus enter a quenching chamber of the cooking appliance and lead to an increased temperature at the extinguishing temperature sensor during the status check of the extinguishing nozzle and thus to a smaller drop in the extinguishing temperature.

In all the above-mentioned embodiments of the invention, the check time at which a status check of a nozzle is carried out by a control unit of the cooking appliance can be set with regard to various optimization criteria. For example, a status check can be carried out at regular intervals of, for example, one day or one month, or after the expiry of a period specified in the unpublished EN 10 2007 059 614 described limescale account, which indicates the degree of progressive calcification of a nozzle depending on the individual user behavior.

In addition, it is possible for the control unit to determine the time of the check depending on previously identified error events in the cooking appliance, so that certain error scenarios can be better responded to. For example, if an abrupt change in a characteristic value of a status check is detected, further status checks can be triggered by the control unit at short intervals in succession to determine whether the detected abrupt change persists or, as in the case of temporarily occurring air bubbles in the pipe network, quickly disappears again.

If the control unit uses additional intelligent fault detection systems, for example a system for checking the status of a steam generator of the cooking appliance, the results of this additional fault detection can also be used to control the time of the check.

The features of the invention disclosed in the above description, in the claims and in the drawings may be essential for the realization of the invention in its various embodiments both individually and in any combination.

List of reference symbols

1

Cooking appliance

2

Cooking chamber

3

Cooking chamber wall

4

Cooking chamber floor

5

Flow baffle

6

Blower room wall

10

Blower room

14

Blower wheel

15

axis

16

engine

17

opening

18

Recess

19

Heating

20

jet

22

Valve

23

Control line

24

Supply line

26

Main line

28

Temperature sensor

29

Measurement line

30

Sequence

31

Extinguishing chamber

32

jet

33

Valve

34

Supply line

35

Control line

36

Temperature sensor

37

Measurement line

38

Drain

39

Vent pipe

40

Steam generator

41

Steam generator nozzle

42

Control line

50

Control unit

t, T

Time

t0, t0', t3

Time at which the fogging event began

t1, t1', t4

Time of end of the humidification event

t2, t5

Time of maximum temperature drop

away

constant

GT*, GT0*

standardized cooking chamber temperature

ΔGT*, ΔGT0*

maximum temperature drop in the cooking chamber

AT*, AT0*

standardized quenching temperature

ΔAT*, ΔAT0*

maximum temperature drop in the quenching chamber

δGT*, δAT*

relative maximum temperature drop

BD

Switch-on characteristics of the humidification nozzle

AD

Switch-on characteristics of the extinguishing nozzle

V1, V2

Spray direction

Claims (24)

Method for identifying error events in a cooking appliance with at least one nozzle for injecting at least one fluid into an interior of the cooking appliance and at least one sensor for recording measured values that are characteristic of the state of the nozzle in the interior, comprising the following steps: - carrying out several state checks, each of which records a temporal reaction of at least the measured value to at least one nozzle activity, for the same nozzle one after the other at certain time intervals; - determining the state of the nozzle as a result of the state check depending on a characteristic variable selected from at least one of the measured values; - storing the states as a state history in a memory of a control unit of the cooking appliance; - tracking the temporal development of the states based on the state history; and/or - simultaneously carrying out several state checks on different nozzles - determining the state of the respective nozzles as a result of the state check depending on a characteristic variable selected from at least one of the measured values; - comparing the resulting states with one another; and identifying candidate fault events based on the state history of the health checks of the same nozzle and/or different fault events based on comparing multiple simultaneous health checks on different nozzles. Procedure according to Claim 1 , characterized in that a cooking chamber, a blower chamber, a steam generator housing and/or a quenching chamber of the cooking appliance is selected as the interior, and a measured value is formed by a temperature value or a humidity value. Procedure according to Claim 1 or 2 , characterized in that nozzle activity occurs when the fluid flows through the nozzle in the form of at least one pulse or an interval comprising several successive pulses, wherein the nozzle activity is preferably limited in time to the time difference between the beginning and the end of the pulse. Procedure according to Claim 3 , characterized in that the measured value acquisition extends in time at least from the beginning to at least the end of the shock or the interval. Method according to one of the preceding claims, characterized in that the characteristic variable is selected from at least a first point in time and at least a first and/or second temporal derivative of the measured value during a drop in the measured value after the start and before the end of a nozzle activity, and/or at least one extreme value of the measured value and a respective associated point in time, wherein the at least one extreme value is reached after the start or after the end of a nozzle activity, and/or from at least a second point in time and at least a second first and/or second temporal derivative of the measured value during a rise in the measured value after the end of a nozzle activity. Method according to one of the preceding claims, characterized in that the hardness of the fluid applied to the nozzle, the pressure of the fluid, the duration of the nozzle activity, the duration between successive nozzle activities and/or the duration between successive condition checks are taken into account during the condition check. Method according to one of the Claims 2 until 6 , characterized in that in the state When checking, the loading of the cooking chamber with food to be cooked, the time within a work program running in the cooking appliance and/or the type and/or length of operation of the cooking appliance before the nozzle activity is/are taken into account. Method according to one of the preceding claims, characterized in that the control unit of the cooking appliance controls, in particular regulates, the nozzle activity by communication with a corresponding nozzle valve and/or the sensor, depending on at least one working program of the cooking appliance. Method according to one of the preceding claims, characterized in that the multiple status checks are carried out at different times during activity of a nozzle and/or at a nozzle Method according to one of the preceding claims, characterized in that a blockage and/or calcification of the nozzle and/or a calcification of the sensor is identified as the first error event if a continuous, in particular slow or gradually increasing, change in the characteristic variable between two successive states is detected in the state history. Method according to one of the preceding claims, characterized in that a lime break or line defect in a nozzle supply line is identified as a second error event if an unsteady, in particular rapid or abrupt, change in at least one characteristic variable between two successive states is detected in the state history. Method according to one of the preceding claims, characterized in that a temporary occurrence of air bubbles in a fluid connection network to which the cooking appliance is connected is identified as a third error event if an unsteady, in particular rapid or abrupt, change in at least one characteristic variable between two successive states is determined in the state history, and this change disappears again in a third subsequent state. Method according to one of the preceding claims, characterized in that the error event which is detected is automatically remedied, wherein preferably in the case of a detected third error event, air is discharged from the fluid connection network by opening at least one nozzle valve of a nozzle. Method according to one of the preceding claims, characterized in that contamination or calcification of the sensor is identified as a fourth error event if a shift of at least one characteristic behavior of the measured value, in particular a characteristic point in time, between two successive states is observed at later points in time in the state history. Method according to one of the preceding claims, characterized in that, when several condition checks are carried out simultaneously on different nozzles, a line defect in a main fluid line which branches into several nozzle feed lines is identified as a fifth error event if all condition checks result in a condition which indicates a blockage of the fluid flow in the respective nozzle. Method according to one of the preceding claims, characterized in that , in order to identify error events, at least one flow measurement value which indicates the fluid flow, in particular the fluid volume per unit of time, in a fluid line, in particular a fluid main line or nozzle feed line, and/or at least one pressure measurement value which indicates the pressure of the fluid guided in such a fluid line is taken into account. Method according to one of the preceding claims, characterized in that the fluid is selected as water, and a first nozzle is used as a steaming nozzle for steaming food in the cooking chamber and/or a second nozzle is used as a quenching nozzle for quenching or condensing hot, steam-containing cooking chamber atmosphere in the quenching chamber and/or a third nozzle is used as a steam generator nozzle for filling the steam generator housing. Method according to one of the preceding claims, characterized in that the fluid is selected as a cleaning agent, and a fourth nozzle is used as a cleaning agent nozzle for cleaning the interior, wherein in particular the cleaning agent comprises a cleaner, descaler, rinse aid and/or water. Method according to one of the preceding claims, characterized in that the specific state, the specific state history and/or the identified error event is displayed, wherein such a display can be made as a display with a warning signal or instructions for an operator and/or as a service message for a service technician. Cooking appliance with at least one nozzle (20, 32, 41) for injecting at least one fluid into an interior space, comprising a cooking chamber (2), a blower chamber (10), a steam generator housing (40) and/or an extinguishing chamber (31), with at least one sensor (28, 36) for detecting at least one measured value, in particular determined from a temperature value (GT _ist , AT _ist ) and/or a humidity value (F), and with a control unit (50) which is set up to carry out a method according to one of the preceding claims and which communicates with the sensor (28, 36) via corresponding measuring lines (29, 37) and at least one nozzle valve (22, 33) via corresponding control lines (23, 35). Cooking appliance after Claim 20 , characterized by a nozzle supply line (24, 34) for connecting the nozzle to a fluid supply device, in particular a water supply network, preferably via a main line (26). Cooking appliance after Claim 20 or 21 , characterized in that the nozzle is selected from a humidification nozzle (20), extinguishing nozzle (32), steam generator nozzle (41) and cleaning nozzle. Cooking appliance according to one of the Claims 20 until 22 , characterized by a storage device for storing the detected state, the detected state history and/or the identified error event and/or a display device for displaying a detected state, a detected state history and/or a detected error event. Cooking appliance according to one of the Claims 20 until 23 , characterized by at least one flow sensor and/or at least one pressure sensor, which is in operative connection with the control unit (50).

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