DE102020127559A1 - Cooking appliance, preferably oven or steam cooker - Google Patents

Abstract

The invention relates to a cooking appliance (1), preferably an oven (1) or a steam cooker (1), with at least one cooking chamber (11) for accommodating the food to be cooked, with at least one fan (16) which is designed to blow a gas of the cooking chamber (11), with an electric motor (17) which is designed to drive the fan (16) and with at least one temperature sensor (18) which is designed to detect a temperature of the cooking chamber (11). The cooking appliance (1) is characterized in that the cooking appliance (1), preferably a control unit (15) of the cooking appliance (1), is designed to measure the humidity of the cooking chamber (11) based at least • on a power consumption of the electric motor (17) ,• on a temperature of the windings of the electric motor (17) and• on a temperature of the cooking chamber (11)

Description

The invention relates to a cooking appliance, preferably an oven or a steam cooker, according to the preamble of patent claim 1.

In the case of kitchen appliances which are intended for cooking food and can therefore also be referred to as cooking appliances, it can be of interest to know the humidity in the cooking chamber. Humidity can also be referred to as air humidity or simply as moisture. Humidity describes the proportion of water vapor, or steam for short, in the gas mixture in the air.

Such a cooking space can be closed in particular during the cooking process. Such cooking devices can be steam cookers, ovens, microwaves and combinations of these, in particular. Depending on the cooking appliance, the cooking chamber can be made accessible by opening a door, a flap, a panel and the like. Such cooking devices can be designed as individual devices, for example to be set up on a worktop in a kitchen, or as built-in devices for integration into kitchen furniture. Cooking utensils such as pots, pans and the like with lids can also be counted among the cooking appliances.

Oxygen sensors, for example, which are arranged completely or at least with their sensor element in the cooking chamber, can be used for sensory determination of the air humidity in the closed cooking chamber during the cooking process. This is usually done as a fixed, i.e. permanent, arrangement. As a result, the air humidity can be directly detected by sensors and the detected sensor data can be evaluated and used, for example, by a control unit of the cooking appliance. For example, in the case of a steam cooker, the steam generation or the steam supply into the closed cooking chamber during the cooking process can be regulated by its control unit by means of the humidity determined by sensors to a predetermined steam content of the cooking chamber.

However, the disadvantage of using a sensor such as an oxygen sensor is that the acquisition and installation of the sensor can cause additional costs. This applies accordingly to its wiring.

It is also disadvantageous that if the sensor fails, the corresponding functions of the cooking appliance, which require the air humidity detected by sensors in the closed cooking chamber during the cooking process, can no longer be used.

Another disadvantage is that an inner housing of the cooking appliance, which at least essentially forms the cooking chamber, usually has to be perforated in order to supply and operate the sensor arranged entirely in the cooking chamber electrically using a cable and to feed the detected sensor data to the control unit. The corresponding passage opening of the inner housing of the cooking appliance has to be provided on the one hand and sealed vapor-tight around the cable of the sensor on the other hand after it has been installed, which can also represent an additional expense. Otherwise steam from the interior can get into an intermediate space of the cooking appliance and endanger electrical and electronic elements of the cooking appliance in particular. If only one sensor element of the sensor is passed through the inner housing into the cooking chamber, this also applies to the seal around the sensor with respect to the passage opening of the inner housing of the cooking appliance.

the EP 1 342 414 A1 relates to a method for detecting the humidity in an apparatus for treating and preparing food and an apparatus for treating and preparing food. In the method, current temperature values and speed values of the asynchronous motor driving a gas conveying and circulation device are compared with at least one characteristic curve stored in a computer, and the current humidity in the gas mixture is calculated from the deviation ΔN of the measured speed from the speed of the stored characteristic curve definitely.

The disadvantage of this is that the accuracy of the method of EP 1 342 414 A1 depends on the quality of the characteristic curve stored in the computer and on the quality of the recorded speed values of the asynchronous motor. If one of these values and, in particular, both of these values themselves are imprecise, this leads to a correspondingly imprecise conclusion about the humidity in the closed cooking space during the cooking process.

The invention therefore addresses the problem of providing a cooking appliance, preferably an oven or a steam cooker, of the type described above, so that the humidity in the cooking chamber can be determined more precisely, more reliably, more easily and/or more cost-effectively than previously known. At the very least, an alternative to known cooking appliances of this type should be created.

According to the invention, this problem is solved by a cooking appliance having the features of patent claim 1 . Advantageous refinements and developments of the invention result from the following dependent claims.

The present invention thus relates to a cooking appliance, preferably an oven or a steam cooker, with at least one cooking space for accommodating food to be cooked, with at least one fan which is designed to draw a gas such as air or an air-steam mixture from the cooking space to promote, with an electric motor, which is designed to drive the fan, and with at least one temperature sensor, which is designed to detect a temperature of the cooking chamber, ie a current temperature of the air or the air-steam mixture in the cooking chamber .

• • auf einer Aufnahmeleistung des elektrischen Motors,
• • auf einer Temperatur der Wicklungen des elektrischen Motors und
• • auf einer Temperatur des Garraums

zu bestimmen. Ggfs. können zusätzlich noch weitere Einflussgrößen bzw. Parameter wie zum Beispiel die Drehzahl des elektrischen Motors verwendet werden, um die Feuchte des Garraums zu bestimmen.The cooking appliance is characterized in that the cooking appliance, preferably a control unit of the cooking appliance, is designed to be based at least on a humidity level in the cooking chamber

• • on an input power of the electric motor,
• • on a temperature of the windings of the electric motor and
• • on a cooking chamber temperature

to determine. possibly In addition, other influencing variables or parameters such as the speed of the electric motor can also be used to determine the humidity of the cooking chamber.

Thus, according to the invention, the power consumption of the electric motor of the fan can be used to determine the humidity of the gas inside the cooking chamber without a corresponding sensor. This gas can be dry air in the form of ambient air or a mixture of ambient air and water vapor, or steam for short.

The invention is based on the finding that the power consumption of the electric motor is proportional to the gas density of the gas in the cooking chamber, i.e. inside the cooking chamber. The humidity of the cooking chamber can be determined from the gas density of the gas in the cooking chamber if the temperature of the cooking chamber is known.

The input power of the electric motor of the blower can depend not only on the moisture but also on the temperature of the windings of the electric motor. The power consumption of the electric motor increases as the temperature of the windings of the electric motor increases, since the motor losses, i.e. the current heat losses of the windings of the electric motor, increase. This can lead to inaccuracies when determining the humidity based on the input power of the electric motor. Therefore, if the heating of the windings of the electric motor during operation is also taken into account, the disturbing influence of the temperature of the windings of the electric motor on the measurement inaccuracy of the humidity in the cooking chamber can be reduced. Accordingly, the accuracy and/or the reliability of the determination of the humidity in the cooking space can be increased. This can be done easily and/or inexpensively in this way.

It can be advantageous to keep the speed of the electric motor constant in order to exclude changes in the speed of the electric motor, which can also lead to changes in the pickup power of the electric motor, as an influencing variable. This can further increase the accuracy and/or the reliability of the determination of the humidity in the cooking space.

Alternatively, both the input power of the electric motor of the fan and its speed can be variable during operation. In this case, conclusions can be drawn about the gas density of the gas in the cooking chamber from the input power of the electric motor and from its speed by means of characteristic curves or the like. This can make it possible to implement the invention without speed control, which can keep effort and costs low. However, this can have a disadvantageous effect on the accuracy and/or the reliability of the determination of the humidity in the cooking chamber.

According to one aspect of the invention, the cooking appliance, preferably the control unit of the cooking appliance, is designed to operate the electric motor at a constant speed. This can provide the benefits previously described.

According to a further aspect of the invention, the cooking appliance, preferably the control unit of the cooking appliance, is designed to determine from the temperature of the windings of the electric motor a proportion of the power consumption of the electric motor, which is caused by a temperature increase in the windings of the electric motor compared to its idle state , and to determine the humidity of the cooking chamber based at least on the input power of the electric motor minus the determined proportion and on the temperature of the cooking chamber. As a result, the recorded power consumption of the electric motor can be corrected by the proportion that is caused by the current heat losses of the electric motor and not by the moisture in the cooking chamber before this corrected power consumption of the electric motor is further processed or used. This can enable easy implementation of the aspects of the invention described above.

According to a further aspect of the invention, the cooking appliance, preferably the control unit of the cooking appliance, is designed to determine a gas density of the cooking chamber at least from the input power of the electric motor and from the temperature of the cooking chamber and to determine the humidity of the cooking chamber from the determined gas density of the cooking chamber . As a result, the corresponding linear or proportional relationships can be used to determine the humidity in the cooking chamber. This can make the determination correspondingly easy and/or accurate.

According to a further aspect of the invention, the cooking appliance, preferably the control unit of the cooking appliance, is designed to determine the power consumption of the electric motor from the electric current of the electric motor. This may make it possible to obtain the input power of the electric motor. This can be done in this way with little effort.

• • auf einer Drehzahl des elektrischen Motors,
• • auf einer Temperatur der Wicklungen des elektrischen Motors und
• • auf einer Temperatur des Garraums

zu bestimmen.The invention also relates to a cooking appliance, preferably an oven or a steam cooker, with at least one cooking chamber for accommodating the food to be cooked, with at least one fan which is designed to convey a gas from the cooking chamber, with an electric motor which is designed to drive the fan, and with at least one temperature sensor, which is designed to detect a temperature of the cooking chamber, characterized in that the cooking appliance, preferably a control unit of the cooking appliance, is designed to based at least one humidity of the cooking chamber

• • on a speed of the electric motor,
• • on a temperature of the windings of the electric motor and
• • on a cooking chamber temperature

to determine.

Hereby the respective aspects of the invention described above can be implemented based at least on the speed of the electric motor.

According to one aspect of the invention, the cooking appliance, preferably the control unit of the cooking appliance, is designed to operate the electric motor with a constant electric voltage. As a result, changes in the electrical voltage of the electric motor, which can lead to changes in the pickup line of the electric motor, can be excluded or reduced as an influencing variable. This can further increase the accuracy and/or the reliability of the determination of the humidity in the cooking space.

According to a further aspect of the invention, the cooking appliance, preferably the control unit of the cooking appliance, is designed to determine from the temperature of the windings of the electric motor a proportion of the speed of the electric motor, which is caused by a temperature increase in the windings of the electric motor compared to its idle state , and to determine the humidity of the cooking chamber based at least on the speed of the electric motor minus the determined proportion and on the temperature of the cooking chamber. As a result, the corresponding aspects of the invention described above can be applied to the determination of the humidity of the cooking chamber based at least on the speed of the electric motor.

According to a further aspect of the invention, the cooking appliance, preferably the control unit of the cooking appliance, is designed to determine a gas density of the cooking chamber at least from the speed of the electric motor and from the temperature of the cooking chamber and to determine the humidity of the cooking chamber from the determined gas density of the cooking chamber . As a result, the corresponding aspects of the invention described above can be applied to the determination of the humidity of the cooking chamber based at least on the speed of the electric motor.

According to a further aspect of the invention, the cooking appliance, preferably the control unit of the cooking appliance, is designed to detect the temperature of the windings of the electric motor by sensors. Although this may necessitate a corresponding sensor, it makes the temperature of the windings of the electric motor available with a high level of accuracy.

According to a further aspect of the invention, the cooking appliance, preferably the control unit of the cooking appliance, is designed to determine the temperature of the windings of the electric motor using a thermal model of the windings of the electric motor. Although this means that a corresponding sensor can be dispensed with, it may be necessary to create and, if necessary, adapt a corresponding thermal model of the windings of the electric motor that is as accurate as possible, which is to be used during operation of the cooking appliance, which can also lead to increased effort .

• • Erfassen oder Bestimmen einer Aufnahmeleistung des elektrischen Motors,
• • Erfassen einer Temperatur der Wicklungen des elektrischen Motors,
• • Erfassen einer Temperatur des Garraums und
• • Bestimmen einer Feuchte des Garraums basierend wenigstens
  • ◯ auf der erfassten oder bestimmten Aufnahmeleistung des elektrischen Motors,
  • ◯ auf der erfassten Temperatur der Wicklungen des elektrischen Motors und
  • ◯ auf der erfassten Temperatur des Garraums.

The invention also relates to a method for operating a cooking appliance, preferably an oven or a steam cooker, with at least one cooking chamber for accommodating a food to be cooked Food to be cooked, with at least one fan, which is designed to convey a gas from the cooking space, with an electric motor, which is designed to drive the fan, and with at least one temperature sensor, which is designed to detect a temperature of the cooking space, wherein the Method has at least the steps:

• • detecting or determining an input power of the electric motor,
• • detecting a temperature of the windings of the electric motor,
• • detecting a temperature of the cooking chamber and
• • Determining a humidity of the cooking space based at least
  • ◯ on the detected or determined input power of the electric motor,
  • ◯ on the recorded temperature of the windings of the electric motor and
  • ◯ on the detected temperature of the cooking compartment.

The properties and advantages of the corresponding cooking appliance described above can be implemented by means of such a method.

• • Erfassen oder Bestimmen einer Drehzahl des elektrischen Motors,
• • Erfassen einer Temperatur der Wicklungen des elektrischen Motors,
• • Erfassen einer Temperatur des Garraums und
• • Bestimmen einer Feuchte des Garraums basierend wenigstens
  • ◯ auf der erfassten oder bestimmten Drehzahl des elektrischen Motors,
  • ◯ auf der erfassten Temperatur der Wicklungen des elektrischen Motors und
  • ◯ auf der erfassten Temperatur des Garraums.

The invention also relates to a method for operating a cooking appliance, preferably an oven or a steam cooker, with at least one cooking chamber for accommodating the food to be cooked, with at least one fan which is designed to convey a gas from the cooking chamber, with an electric motor, which is designed to drive the fan, and with at least one temperature sensor, which is designed to detect a temperature of the cooking chamber, the method having at least the following steps:

• • detecting or determining a speed of the electric motor,
• • detecting a temperature of the windings of the electric motor,
• • detecting a temperature of the cooking chamber and
• • Determining a humidity of the cooking space based at least
  • ◯ on the detected or determined speed of the electric motor,
  • ◯ on the recorded temperature of the windings of the electric motor and
  • ◯ on the detected temperature of the cooking compartment.

The properties and advantages of the corresponding cooking appliance described above can be implemented by means of such a method.

In other words, the invention is based on the knowledge that the following applies to the power requirement of a fan or blower when the air density changes: $${\text{P}}_2={\text{<figure-callout id="1" label="P" filenames="DE102020127559A1\_0010.png" state="{{state}}">P</figure-callout>}}_1\cdot \frac{{\mathrm{\rho }}_2}{{\mathrm{<figure-callout\; id="1"\; label="\rho "\; filenames="DE102020127559A1\_0010.png"\; state="\{\{state\}\}">\rho </figure-callout>}}_1}.$$

The power P and the density ρ of the gas mixture that is conveyed by the blower are therefore proportional to each other.

The power P of a fan or its electric motor depends, among other things, on the speed of the electric motor. Measurements show that when the speed of the electric motor is constant, there is a mathematical relationship between the power P of the electric motor and density ρ, so that a high density ρ requires more power P from the electric motor than a low density p. If the speed of the electric motor is controlled in a stationary manner, then the power of the electric motor adjusts itself at the operating point.

lässt sich die Dichte ρ eines Gases durch Einsetzen von $V=\frac{m}{\mathrm{\rho }}$

mit der folgenden Formel berechnen: $$\mathrm{\rho }=\frac{p}{R_{S}T}.$$

According to the general gas equation $$p\cdot V=m\cdot R_S\cdot T$$

the density ρ of a gas can be calculated by inserting $V=\frac{m}{\mathrm{\rho }}$

calculate with the following formula: $$\mathrm{\rho }=\frac{p}{R_{S}T}.$$

und für Wasserdampf $R_{\text{S}\text{,Dampf}}=\mathrm{461,5}\frac{\text{J}}{\text{kg}\cdot \text{K}}.$

Aufgrund der höheren spezifischen Gaskonstante R_S weist Wasserdampf bei gleicher Temperatur T und bei gleichem Druck ρ stets eine geringere Dichte ρ als trockene Luft auf.P is the pressure or the air pressure, T is the temperature of the gas and R _S is the specific gas constant of the gas under consideration. For dry air, the specific gas constant $R_{\text{S}\text{,Air}}=287\frac{\text{J}}{\text{kg}\cdot \text{K}}$

and for water vapor $R_{\text{S}\text{,Steam}}=461.5\frac{\text{J}}{\text{kg}\cdot \text{K}}.$

Due to the higher specific gas constant R _S , water vapor always has a lower density ρ than dry air at the same temperature T and at the same pressure ρ.

The basis of the moisture sensing according to the invention, ie the inventive determination of the humidity of the air in the cooking chamber, is therefore the different densities p of dry air and water vapor. If steam is introduced into the cooking chamber, it displaces the air and the density ρ of the gas mixture of air and steam decreases. From this it follows that with a constant speed of the electric motor of the blower, a lower power P of the electric motor is required. This power change of the electric motor can affect the supply current of the electronics or the control unit of the cooking appliance can be measured or recorded and used to evaluate or determine the humidity in the cooking chamber. Dry air in the cooking chamber corresponds to the gas mixture of the earth's atmosphere of nitrogen (approx. 78.08% by volume) and oxygen (approx. 20.95% by volume). The remaining approx. 1% by volume consists of various gases and water vapour. The air density in the cooking chamber depends on the temperature T and the air pressure p there. If the air pressure p is assumed to be constant (p = 101330 Pa), the air density p in the cooking chamber depends only on the temperature T.

At a constant temperature T, the density ρ of gas mixtures can be calculated by adding the specific densities ρ _air and ρ _steam multiplied by their relative ratio to the total volume r: $${\mathrm{\rho }}_{\text{mixture}}={\mathrm{\rho }}_{\text{Air}}\cdot {\text{right}}_{\text{Air}}+{\mathrm{\rho }}_{\text{steam}}\cdot {\text{right}}_{\text{steam}}$$

This equation can be rearranged by inserting r _air = 1 - r _steam in order to determine the proportion of steam, ie the humidity: $${\text{right}}_{\text{steam}}=\frac{{\mathrm{\rho }}_{\text{mixture}}\mathrm{-}{\mathrm{\rho }}_{\text{Air}}}{{\mathrm{\rho }}_{\text{steam}}\mathrm{-}{\mathrm{\rho }}_{\text{Air}}}$$

berechnet werden, wenn Temperatur T und Druck p bekannt sind. Ist auch die Dichte ρ bzw. ρ_Gemisch des vorliegenden Gasgemisches bekannt, so kann der relative Anteil von Wasser r_Dampf im Gasgemisch berechnet werden. Um dies zu realisieren, kann ρ_Gemisch aus der Leistungsaufnahme bzw. aus dem Versorgungsstrom des elektrischen Motors ermittelt bzw. bestimmt werden.The specific densities ρ _air and ρ _steam for gas mixtures consisting of 100% by volume air or 100% by volume water vapor are known or can be found in $\mathrm{\rho }=\frac{\text{p}}{{\text{R}}_{\text{S}}\text{T}}$

can be calculated if the temperature T and pressure p are known. If the density ρ or ρ _mixture of the existing gas mixture is also known, the relative proportion of water r _steam in the gas mixture can be calculated. In order to realize this, ρ _mixture can be determined or determined from the power consumption or from the supply current of the electric motor.

As the temperature rises, the ohmic resistance of the motor windings increases, which can lead to higher power consumption in the form of a higher supply current in the case of speed control and a constant voltage supply. A change in the supply current can therefore not only be caused by changes in the density ρ or the speed of the electric motor, but also by a change in the motor temperature. For humidity sensing, this means that the heating of the electric motor during operation represents an interference.

One possibility according to the invention for detecting the heating of the electric motor can be seen in measuring the motor winding temperature directly using a temperature sensor. The advantage here is that the temperature of the electric motor can be recorded directly and the density or moisture measurement can be corrected directly. The disadvantage of this, however, is that an additional temperature sensor can be required if the electric motor does not already have a temperature sensor, for example for monitoring overheating, which can also be used to implement the invention.

Another possibility according to the invention can be to calculate or estimate the motor temperature using a thermal model. A thermal model that describes the physical thermal properties of the electric motor or the cooking appliance with sufficient accuracy is formed and the motor winding temperature is calculated as a function of other input variables or parameters, which are preferably measured anyway. The advantage here is that an additional temperature sensor can be dispensed with. The disadvantage, however, is that a corresponding modeling must be carried out. Furthermore, when the cooking appliance is in operation, the thermal model must be operated continuously and the motor temperature must be calculated or determined, which can represent an additional outlay for the control unit, for example. Furthermore, the motor temperature can only be determined from the thermal model as precisely as the thermal model depicts the windings of the electric motor or the cooking appliance. This can lead to inaccuracies in the calculated motor temperature.

In any case, by correcting the motor winding temperature, a mathematical relationship between the density of the mixture in the cooking chamber and the power consumption of the electric motor can be obtained at a constant speed of the electric motor. This also applies to the speed of the electric motor at a constant input power. Based on this, the humidity in the cooking chamber can be determined and used, for example, for the process technology in the cooking appliance.

This procedure can be used for electric motors of the cooking appliance, in which the speed can be regulated to a constant value. It is also possible to regulate the input power of the electric motor to a constant value and to determine the humidity in the cooking chamber based on changes in the speed of the electric motor, taking into account the motor winding temperature. If no control of the electric motor is used, for example characteristic curves can be used to determine the humidity be controlled to a constant value (power or speed) can lead to a higher accuracy of the determined humidity.

A thermal model of the windings of the electric motor of the blower can be created or derived to correct the humidity sensing by detecting the corresponding influencing variables and mathematically simulating their thermal effect on the windings of the electric motor. The heating of the electric motor itself and thus also its windings can be attributed to the rising temperature in the cooking chamber due to the thermal coupling between the cooking chamber and the electric motor. Furthermore, the current flow in the windings of the electric motor during operation can lead to heating of the windings and thus also of the electric motor. In addition to the temperature in the cooking chamber, which is already recorded or measured in an oven using a PT100 as a temperature sensor, for example, the motor current can be recorded or measured in the form of a voltage via a shunt resistor in order to record the power consumption of the electric motor or to be determined from this. This relates to the implementation of the invention as well as an experimental setup for creating the thermal model of the windings of the electric motor of the fan.

To derive a thermal model, an additional temperature sensor can be attached to the windings of the electric motor of the fan, but this is not present in the practical implementation in the cooking appliance.

The behavior of the heat flow can be described by a PT1 element. Since the temperature of the cooking chamber and the input power of the electric motor of the fan or its current are two input variables, the thermal model of the windings can be formed with two PT1 elements whose output variables are superimposed to obtain the temperature of the motor windings. The transfer functions of the two PT1 elements can be determined from the measured values recorded. The thus obtained thermal model of the windings of the electric motor of the fan can then be used in operation instead of the additional temperature sensor on the windings of the electric motor of the fan.

An additional influence on the heating of the electric motor or its windings can be the heat of condensation of the water vapor in the cooking chamber. This can remain unconsidered in the thermal model of the windings of the electric motor, since the proportion of water vapor in the cooking chamber has to be determined. possibly However, the heat of condensation of the water vapor in the cooking chamber can still be taken into account when creating the model. More complex models can also be created and used to increase accuracy.

• 1 eine seitliche Schnittdarstellung eines erfindungsgemäßen Gargeräts mit geschlossenem Garraum.

An embodiment of the invention is shown purely schematically in the drawing and is described in more detail below. It shows

• 1 a lateral sectional view of a cooking appliance according to the invention with a closed cooking chamber.

The above figure is viewed in Cartesian coordinates. A longitudinal direction X, which can also be referred to as depth X or length X, extends. A transverse direction Y (not shown), which can also be referred to as width Y, extends perpendicularly to the longitudinal direction X. A vertical direction Z, which can also be referred to as the height Z and corresponds to the direction of gravity, extends perpendicularly both to the longitudinal direction X and to the transverse direction Y. The longitudinal direction X and the transverse direction Y together form the horizontal X, Y, which can also be referred to as the horizontal plane X, Y.

A cooking appliance 1 such as, in particular, an oven 1 or a steam cooker 1 has an outer housing 10, which can also be referred to as the outer housing 10 and essentially closes off or encloses the cooking appliance 1 on the outside. An inner housing 12 , which can also be referred to as the inner housing 12 , is arranged inside the outer housing 10 . The inner housing 12 closes in the longitudinal direction X to the front, i.e. from the perspective of a user, upwards and downwards in the vertical direction Z with the outer housing 10, so that an intermediate space 13 is formed between the outer housing 10 and the inner housing 12, which can also be referred to as housing space 13 . This gap 13 represents the interior of the built-in cooking appliance 1.

Furthermore, the inner housing 12 essentially encloses an interior space 11 in which a cooking process can be carried out. Accordingly, the interior 11 can also be referred to as the cooking chamber 11 . The interior 11 is accessible to a user in the longitudinal direction X from the front of the built-in cooking appliance 1 through a through opening (not labeled) as an access opening, which can be opened and closed by the user through a flap 14 or through a door 14 . A current temperature in the interior 11 or in the cooking chamber 11 of the cooking appliance 1 can be detected by means of a temperature sensor 18 arranged there.

There is a blower 16 in the interior 11 or in the cooking chamber 11 in order to convey or circulate the air or an air-steam mixture located there and thereby ensure the most uniform possible temperature or steam distribution in the interior 11 or . The fan 16 can be operated in a speed-controlled manner by means of an electric motor 17 , the electric motor 17 being arranged in the intermediate space 13 . A control unit 15 which can receive temperature data from the temperature sensor 18 is also arranged in the intermediate space 13 . Furthermore, the control unit 15 can operate the electric motor 17 in a speed-controlled manner with a constant electric voltage and can detect the electric current of the electric motor 17 and the temperature of the windings of the electric motor 17 by sensors.

Based on a power consumption of the electric motor 17, which the control unit 15 can determine from the detected electric current of the electric motor 17 and the constant electric voltage of the electric motor 17 or a supply voltage source, on the sensor-detected temperature of the windings of the electric motor 17 and The control unit 15 can determine the humidity of the air or the air-steam mixture in the cooking chamber 11 based on the temperature of the cooking chamber 11 detected by the temperature sensor 18 .

For this purpose, the control unit 15 can determine from the temperature of the windings of the electric motor 17 a proportion of the power consumption of the electric motor 17, which is caused by a temperature increase in the windings of the electric motor 7 during operation compared to its cooled down state or at rest at ambient temperature. In other words, conclusions can be drawn from the temperature of the windings of the electric motor 17 about the Joule heat losses which occur when the windings of the electric motor 17 are energized during operation. This proportion can then be subtracted from the power consumption of the electric motor 17 determined from the detected electric current of the electric motor 17 and the constant electric voltage of the electric motor 17 in order to take into account the heating of the electric motor 17 or exclude it as a disturbance variable or at least to to reduce.

The control unit 15 can now determine a gas density of the cooking chamber 11 from this power consumption of the electric motor 17, which has been corrected for the effects of the current heat losses of the windings of the electric motor 17, and from the temperature of the cooking chamber 11 recorded by the temperature sensor 18, for which purpose a linear or proportional relationship is used can be. From the determined gas density of the cooking chamber 11, the control unit 15 can then determine the humidity of the cooking chamber 11, for which a linear or proportional relationship can also be used. This can enable the humidity of the cooking chamber 11 to be determined with comparatively high accuracy without a corresponding sensor.

Reference List

X

longitudinal direction; Depth; length

Y

transverse direction; Broad

Z

vertical direction; Height

X, Y

Horizontal; horizontal plane

1

cooking appliance; Oven; steamer

10

outer casing; outer casing

11

Inner space; cooking chamber

12

inner case; inner casing

13

space; housing space

14

Flap; door

15

control unit

16

fan

17

electric motor

18

Interior temperature sensor 11

QUOTES INCLUDED IN DESCRIPTION

This list of documents cited by the applicant was generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Patent Literature Cited

• EP 1342414 A1 [0008, 0009]

Claims (13)

Cooking appliance (1), preferably oven (1) or steam cooker (1), with at least one cooking chamber (11) for accommodating the food to be cooked, with at least one fan (16) which is designed to blow a gas into the cooking chamber (11). promote, with an electric motor (17), which is designed to drive the fan (16), and with at least one temperature sensor (18), which is designed to detect a temperature of the cooking chamber (11), characterized in that the cooking appliance (1), preferably a control unit (15) of the cooking appliance (1), a humidity of the cooking chamber (11) based at least on a power consumption of the electric motor (17), on a temperature of the windings of the electric motor (17) and to determine a temperature of the cooking chamber (11). Cooking appliance (1) after claim 1 , characterized in that the cooking appliance (1), preferably the control unit (15) of the cooking appliance (1), is designed to operate the electric motor (17) at a constant speed. Cooking appliance (1) after claim 1 or 2 , characterized in that the cooking appliance (1), preferably the control unit (15) of the cooking appliance (1), is designed to determine a proportion of the power consumption of the electric motor (17) from the temperature of the windings of the electric motor (17), which is caused by a temperature increase in the windings of the electric motor (7) compared to its idle state, and the humidity of the cooking chamber (11) based at least on the power consumption of the electric motor (17) minus the specific proportion and on the temperature of the cooking chamber (11) to determine. Cooking appliance (1) according to one of the preceding claims, characterized in that the cooking appliance (1), preferably the control unit (15) of the cooking appliance (1), is designed at least from the input power of the electric motor (17) and from the temperature of the Cooking chamber (11) to determine a gas density of the cooking chamber (11) and from the determined gas density of the cooking chamber (11) to determine the humidity of the cooking chamber (11). Cooking appliance (1) according to one of the preceding claims, characterized in that the cooking appliance (1), preferably the control unit (15) of the cooking appliance (1), is designed to derive the input power of the electric motor (17) from the electric current of the electric motor (17) to determine. Cooking appliance (1), preferably oven (1) or steam cooker (1), with at least one cooking chamber (11) for accommodating the food to be cooked, with at least one fan (16) which is designed to blow a gas into the cooking chamber (11). promote, with an electric motor (17), which is designed to drive the fan (16), and with at least one temperature sensor (18), which is designed to detect a temperature of the cooking chamber (11), characterized in that the cooking appliance (1), preferably a control unit (15) of the cooking appliance (1), a humidity of the cooking chamber (11) based at least on a speed of the electric motor (17), on a temperature of the windings of the electric motor (17) and to determine a temperature of the cooking chamber (11). Cooking appliance (1) after claim 6 , characterized in that the cooking appliance (1), preferably the control unit (15) of the cooking appliance (1), is designed to operate the electric motor (17) with a constant electric voltage. Cooking appliance (1) after claim 6 or 7 , characterized in that the cooking appliance (1), preferably the control unit (15) of the cooking appliance (1), is designed to determine a proportion of the speed of the electric motor (17) from the temperature of the windings of the electric motor (17), which is caused by a temperature increase in the windings of the electric motor (7) compared to its idle state, and the humidity of the cooking chamber (11) based at least on the speed of the electric motor (17) minus the specific proportion and on the temperature of the cooking chamber (11) to determine. Cooking appliance (1) according to one of Claims 6 until 8th , characterized in that the cooking appliance (1), preferably the control unit (15) of the cooking appliance (1), is designed to determine a gas density of the cooking chamber ( 11) and to determine the humidity of the cooking chamber (11) from the determined gas density of the cooking chamber (11). Cooking appliance (1) according to one of the preceding claims, characterized in that the Cooking appliance (1), preferably the control unit (15) of the cooking appliance (1), is designed to detect the temperature of the windings of the electric motor (17) by sensors. Cooking appliance (1) according to one of Claims 1 until 9 , characterized in that the cooking appliance (1), preferably the control unit (15) of the cooking appliance (1), is designed to determine the temperature of the windings of the electric motor (17) by means of a thermal model of the windings of the electric motor (17). . Method for operating a cooking device (1), preferably an oven (1) or a steam cooker (1), with at least one cooking chamber (11) for receiving an item to be cooked, with at least one blower (16) which is designed for a gas of the cooking chamber (11), with an electric motor (17), which is designed to drive the fan (16), and with at least one temperature sensor (18), which is designed to detect a temperature of the cooking chamber (11), the method comprising at least the steps: detecting or determining an input power of the electric motor (17), detecting a temperature of the windings of the electric motor (17), detecting a temperature of the cooking chamber (11) and Determining a humidity of the cooking chamber (11) based at least on the detected or determined input power of the electric motor (17), on the detected temperature of the windings of the electric motor (17) and on the detected temperature of the cooking chamber (11). Method for operating a cooking device (1), preferably an oven (1) or a steam cooker (1), with at least one cooking chamber (11) for receiving an item to be cooked, with at least one blower (16) which is designed for a gas of the cooking chamber (11), with an electric motor (17), which is designed to drive the fan (16), and with at least one temperature sensor (18), which is designed to detect a temperature of the cooking chamber (11), the method comprising at least the steps: detecting or determining a speed of the electric motor (17), detecting a temperature of the windings of the electric motor (17), detecting a temperature of the cooking chamber (11) and Determining a humidity of the cooking chamber (11) based at least on the detected or determined speed of the electric motor (17), on the detected temperature of the windings of the electric motor (17) and on the detected temperature of the cooking chamber (11).

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