DE102019209075A1 - Operating a household cooking appliance with a cooling fan - Google Patents

Abstract

A method is used to operate a household cooking appliance (1) with at least one cooling fan (11) for cooling at least one component (8, 9) arranged outside a cooking space (3), in which at least one cooling fan (11) with a Speed target profile (P1, P2), which is specified in the operating sequence, starts up with a delay. A domestic cooking appliance (1) has a cooking space (3), at least one cooling fan (11) for cooling components (8, 9) arranged outside a cooking space (3) and a control device (8), the control device (8) is set up to carry out the procedure. The invention is particularly advantageously applicable to baking ovens, microwave ovens and any combinations thereof.

Description

The invention relates to a method for operating a household cooking appliance with at least one cooling fan for cooling at least one component arranged outside of a cooking space. The invention also relates to a domestic cooking appliance with a cooking chamber, at least one cooling fan for cooling components arranged outside a cooking chamber, and a control device, the control device being set up to carry out the method. The invention is particularly advantageously applicable to baking ovens, microwave ovens and any combinations thereof.

The cooling of components and entire assemblies in ovens is usually done with cooling fans. The components to be cooled are installed in an air shaft and cooled by a flow of cooling air generated by a cooling fan. Since ovens are usually built into furniture, the flow of cooling air must be blown out of the front of the device. The cooling fans are often operated at a very high speed immediately at the start of an operating sequence (which is triggered, for example, by pressing a start button). The particular disadvantage here is that the user typically remains in front of the device for some time in the first few seconds after the start of the operating sequence, e.g. to check settings and / or a positioning of the food, and is blown by a strong air current. Since the user is also directly in front of the oven and the oven is completely at rest before pressing the start button, a noise difference between an off state and an operating sequence with fan activity is clearly perceptible.

It is a typical feature of inexpensive and simple baking ovens that their cooling fans cannot be controlled with variable speed and their device controls do not provide any control sequences for the cooling fans.

DE 101 28 370 A1 discloses a cooking appliance with at least one heating unit, via which a cooking space can be heated, and with at least one cooling fan, of which at least one parameter can be controlled to different parameter values depending on a selected heating mode via a control unit.

EP 2 287 533 A1 discloses a method of controlling the operation of a furnace. A cooling fan is turned on to circulate air in a space between the muffle of the furnace and an outer casing of the furnace. The cooling fan is controlled as a function of a selected cooking program and of a temperature which is measured in the vicinity of a control unit of the oven which is arranged within the space.

EP 2 705 305 B1 discloses an oven comprising an outer body, a cooking cavity in which the cooking process is carried out, a heating device that ensures that food that is placed in the cooking cavity is cooked, a cooling fan arranged between the outer body and the cooking cavity and provides air circulation around the cooking cavity, and a control unit that carries out the cooking process in at least three phases, namely the first phase, the second phase and the third phase, from the beginning to the end of cooking, in the first phase at one first temperature which is determined by the user at the beginning of the cooking process for a first phase duration, in the second phase at a second temperature which is lower than the first temperature and is determined by the user for a second phase duration, and in the third phase at a third temperature, which is higher than in the first or second phase, for a third phase duration, wherein the activation of the cooling fan is delayed by the control unit until the end of the first phase and the cooling fan is only activated in the second phase.

WO 2013/098002 A1 discloses an oven with an outer body, a cooking space in which the cooking process is carried out, a door that allows access to the cooking space, a front panel which is arranged on the top of the door, a control unit which is arranged behind the front panel, a Air duct, which is arranged at the top of the cooking chamber, and an outlet opening that opens between the door and the front panel to the outside, wherein a moisture sensor detects the moisture rate released by the food, the control unit depending on the moisture rate inside the Air duct arranged cooling fan operates according to a predetermined algorithm in successive stop and operating periods to ensure the cooling of the control unit.

U.S. 5,777,897 discloses a method of controlling cooling fans for variable electrical loads. A controller monitors the fan performance, the ambient temperature and the electrical load. The controller then adjusts the fan speed and the resulting cooling to the existing electrical load and ambient temperature. As a result, fan speed is kept to the minimum required to maintain an adequate level of cooling. This minimizes the generation of structure-borne noise and air flow noise.

U.S. 5,688,422 discloses a cooking device for cooking food with a cooking space, a heating element arranged in the cooking space, a temperature sensor for determining the temperature in the cooking device and a fan that operates in at least three modes, namely an OFF mode, a HI mode and a LO -Mode can be operated to move air in the cooking appliance. A fan control device is provided to operate the fan in LO mode by switching the fan on for a first predetermined period of time every other predetermined period of time in order to ensure continuous movement of the fan.

It is the object of the present invention to at least partially overcome the disadvantages of the prior art and in particular to increase user satisfaction and longevity of a household cooking appliance that can be implemented at low cost.

This object is achieved according to the features of the independent claims. Advantageous embodiments are the subject matter of the dependent claims, the description and the drawings.

The object is achieved by a method for operating a household cooking appliance with at least one cooling fan for cooling at least one component arranged outside a cooking chamber, in which at least one cooling fan starts up with a delay with a target speed profile that is fixed at the beginning of the operating sequence. The delayed run-up can also be referred to as a "soft start".

This method has the advantage that the generation of noise from the at least one cooling fan at the beginning of the operating sequence is significantly reduced or even avoided entirely. The user is also advantageously not blown by a strong flow of cooling air immediately at the start of the operating sequence. In the further course of the operating sequence, the user often moves away from the device, which is why the noise development and air blowout, which increases with the start-up, are then no longer perceived as annoying. In addition, a soft start has a positive effect on mechanical loading of the at least one cooling fan and thus on its service life.

The method is based on the knowledge that device components only emit significant thermal energy to a cooling air flow when a sufficiently high temperature difference has been established between a component surface and the cooling air. Operating a cooling fan at high speed directly at the start of the operating sequence produces the disadvantages described above, but no significant cooling effect.

The household cooking appliance can be an oven, steamer, microwave oven or any combination thereof, e.g. an oven with an additional - also independently usable - microwave function and / or steam function or a microwave device with at least one additional IR radiator such as an electrical resistance heating element, etc.

The domestic cooking appliance has a cooking space with a loading opening, typically on the front, which can be closed by means of a door. The cooking space is surrounded by a housing, with various components or functional parts of the domestic cooking appliance being arranged in the space between a cooking space wall or “muffle” and the housing. In particular, there are electrical and electronic components such as resistors, coils, capacitors, diodes, integrated semiconductor components, etc. These can be combined in assemblies or "electronics", e.g. to control electronics, etc. For example, a central control device can be formed by one or more control electronics. In particular, electrical and electronic components or the associated electronics can be sensitive to heat and are therefore often cooled by a flow of cooling air. However, the cooling air flows can also be used to cool other components of the domestic cooking appliance such as the cooking chamber door, screens, a microwave generator, motors, lighting devices, etc.

To generate the at least one cooling air stream, one or more cooling fans can be present that suck in ambient air as cooling air, generate one or more cooling air streams within the appliance and blow the used cooling air out of the domestic cooking appliance again. In particular, the cooling air can be sucked in and / or blown out at the front. A structural design of a household cooking appliance with cooling fan (s) is generally known and is therefore not described further below.

The fact that a cooling fan starts up or is started up with a delay includes, in particular, that its setpoint speed is increased in a deliberately delayed manner from a low value at the beginning of the operating sequence or at the beginning of a control sequence for the cooling fan to a high setpoint (“target speed”). The target speed is therefore not set to the target speed immediately at the start of the operating sequence.

That a cooling fan with a fixed speed at the beginning of the operating sequence Setpoint profile starts up with a delay, includes in particular that the speed setpoint profile is or is established with or at the beginning of the operating sequence. As described in more detail below, the target speed profile can have different courses, one of these courses being selected or determined at the beginning of the operating sequence and then being maintained unchanged during the operating sequence. The time required to determine the shape of the target speed profile is typically negligibly short (eg less than a few seconds), so that the cooling fan can be controlled by means of the target speed profile practically immediately at the start of the operating sequence.

The fact that a target speed profile that is fixedly specified at the beginning of the operating sequence is used to ramp up to the high speed value or the target speed includes in particular that after the start of the activation of the cooling fan by means of the target speed profile or with the start of a corresponding activation sequence, it is no longer changed becomes. In other words, the speed setpoint profile that has been established or predefined for this (current) operating sequence is not varied during its course. This means that the target speed profile is not adapted to measured values, transitions between the cooking phase, etc. determined during its run. The target speed profile is run through independently of the measured value and the food being cooked.

The start of the operating sequence can correspond, for example, to a user (e.g. manual) starting of the household cooking appliance, a starting of the operating sequence at a time specified by the user, or a program-controlled start. An operating sequence can be understood to mean, for example, a (e.g. manually set or program-controlled) cooking sequence, a cleaning sequence (e.g. a pyrolysis sequence), etc. The cooking process can include a selection of certain heating elements and / or a microwave function and / or a steam treatment function and an adjustment of their heating power.

The domestic cooking appliance can have one or more cooling fans. If there are several cooling fans, one, several or all of them can be controlled using the above method. If several or all cooling fans are controlled using the above method, they can be controlled using the same and / or different speed profiles.

• - einer Betriebsart des Betriebsablaufs;
• - einer Zeitdauer seit Beendigung eines vorherigen Betriebsablaufs und/oder
• - mindestens einem unmittelbar vor Beginn des Betriebsablaufs gemessenen Sensormesswert

bestimmt oder ausgewählt wird. Das so bestimmte Drehzahlprofil ist dann folgend für die Ansteuerung mindestens eines Kühllüfters des aktuellen Betriebsablaufs ohne weitere Änderung vorgegeben. Diese Ausgestaltung ergibt den Vorteil, dass das Drehzahlprofil besonders effektiv an einen wahrscheinlichen Temperaturverlauf mindestens einer zu kühlenden Komponente anpassbar ist.It is an embodiment that the speed profile at the beginning of the operating sequence is based on:

• - an operating mode of the operating sequence;
• - a period of time since the termination of a previous operating sequence and / or
• - at least one sensor reading measured immediately before the start of operation

determined or selected. The speed profile determined in this way is then specified for controlling at least one cooling fan of the current operating sequence without any further change. This configuration results in the advantage that the speed profile can be adapted particularly effectively to a probable temperature profile of at least one component to be cooled.

For example, a degree of a delay in the fan run-up and / or a value of a target speed can be set depending on the selected operating mode, whereby different cooking space temperatures and thus also different thermal loads on the components located outside the cooking space can advantageously be taken into account. The selection based on the operating mode can include a selection based on the heating devices used (radiators, microwave ovens, superheated steam generators) and their set power. The delay time (duration) can be reduced if a top heat heater and / or a grill heater are activated, a high set cooking space temperature is set, a steam treatment mode and / or a pyrolysis mode is set.

It is a further development that at least one cooling fan with a speed target profile that is fixedly predetermined at the beginning of the operating sequence only starts up with a delay when a certain operating mode is selected or set. For example, in an oven / microwave combination device, the soft start can only be used if the operating sequence at least initially comprises pure microwave operation (i.e. without activation of heating elements such as an electrical resistance heater). This makes use of the fact that in pure microwave operation, no strong IR radiation is generated in the cooking space, but above all the microwave generator has to be cooled. However, this is not as time-critical as cooling with activated heating elements. If, on the other hand, heating elements are already activated initially, the delayed start-up can be dispensed with and at least one cooling fan can be operated at maximum speed at the start of the operating sequence.

This can be achieved by taking into account a period of time since the end of a previous operating sequence and / or a sensor measured value measured immediately before the start of a fan control or activation of the speed profile Additionally or alternatively, select the speed profile according to whether the cooking appliance or the cooking space is cold or is still warm from a previous operation. As a result, a current thermal load on the components at the beginning of the operating sequence can be taken into account. If the cooking appliance or the cooking space is still warm, the at least one cooling fan can, for example, be brought to its target speed more quickly by reducing the delay.

It is an embodiment that the at least one sensor measured value comprises a value of a cooking space temperature. This has the advantage that it can be determined particularly effectively whether the cooking appliance or the cooking space is cold or is still warm from a previous operation.

It is an embodiment that the at least one sensor measured value comprises a value of a temperature of an ambient air. This has the advantage that the speed profile can be specified based on an estimate of the cooling effect of the ambient air. The cooler the temperature of the surrounding air, the greater the delay can be.

It is a further development that the at least one sensor measured value comprises a value of a temperature of a device component. The device component is basically arbitrary and can for example be a sheet metal part, e.g. a case of a magnetron. It is a further development that the device component is an electrical component and thus the at least one sensor measured value is a value of a temperature of an electrical component, e.g. an electronic component. The temperature sensor can be an NTC resistor or NTC thermistor, for example.

Conversely, the speed profile can be defined independently of one, several or all of these settings. It is generally an embodiment that the target speed profile (hereinafter also simply referred to as “speed profile”) of at least one cooling fan is the same for all operating sequences. This speed profile is therefore also independent of the environment (i.e. independent of the measured value, independent of the length of time since the end of a previous operating sequence, etc.). In this case, there is only one speed profile for the respective cooling fan. This configuration has the advantage that it can be implemented in a particularly simple and inexpensive manner.

In one embodiment, the target speed profile includes a delay time (duration) between the start of the operating sequence or activation of the control (sequence) of the cooling fan and the start of the cooling fan running up to its target speed. This has the advantage that within the delay time the at least one cooling fan is not in operation or is only in operation at a low speed and therefore generates no or only little noise and also no or only a small flow of cooling air. In addition, mechanical stress on the cooling fan can be kept low or even avoided entirely within the delay time.

It is an embodiment that the delay time is up to 45 seconds, in particular up to 30 seconds. This has the advantage that for typical times a user stays at a cooking device after the start of an operating sequence, at least one cooling fan does not generate any disturbing noises or air blow-out currents, but the delay time is still so short that device components are cooled compared to continuous operation of the cooling fan high speeds is sufficiently high from the start to avoid harmful thermal loads, especially peak loads. It is a further development that the delay time is at least 5 seconds, in particular at least 10 seconds, in particular at least 20 seconds.

It is an embodiment that at least one cooling fan is a fan with a fixed or non-variable target speed, e.g. a cooling fan whose drive motor is a shaded pole motor that can be switched on and off by means of a switching relay. A particularly inexpensive configuration is thus provided. Such a fan has in particular two states, namely a configured state and an activated state, the fan rotating at its maximum speed (corresponding to the single target speed) in the activated state. Allowing such a cooling fan to run up thus corresponds to a speed profile in which the cooling fan first remains switched off for the duration of the delay time and is then switched on when the delay time is reached or expired. However, a speed-controlled cooling fan can also be controlled using such a speed profile.

It is an embodiment that the cooling fan is a variable speed cooling fan, e.g. a cooling fan whose drive motor is a BLDC motor controlled by means of a PWM signal. This results in the advantage that a particularly diverse speed profile can be specified.

In the event that the cooling fan is a variable-speed cooling fan, one embodiment is that the speed profile is specified such that the cooling fan is started up with a delay by means of a specified increase in speed or “ramp”, in particular to its target speed. This ramp therefore corresponds to a time segment of the speed profile with a slope of the target speed greater than zero. The use of a ramp has the advantage that the cooling fan is started up mechanically very gently. In comparison to a sudden increase in the setpoint speed after a previous delay time, a stronger cooling effect is achieved with still little noise.

It is a further development that, when the cooling fan is a variable-speed cooling fan, the speed profile is predetermined so that its target speed is below its maximum speed. As a result, energy savings can be achieved and mechanical wear and tear on the cooling fan can be reduced. The target speed of the speed setpoint profile can in particular be determined as a function of one or more of the influencing factors described above, such as the selected operating mode, a setpoint cooking space temperature, etc.

It is an embodiment that the target speed corresponds to at least 70%, in particular at least 80%, in particular at least 90%, of a maximum speed of the cooling fan. In this way, a high cooling performance is achieved with a noticeably lower mechanical load and a noticeable reduction in noise. However, even with a variable-speed cooling fan, the target speed can correspond to the maximum speed, which results in a maximum cooling capacity.

It is a development that the target speed corresponds to a target speed that is reached after the targeted or defined run-up. The target speed can in particular correspond to a setpoint speed that is held for a noticeable period of time after starting up (and in particular after reaching or exceeding at least 70% of the maximum speed), that is to say represents the value of a speed plateau. This holding period can e.g. at least 30 seconds, in particular at least one minute, in particular five minutes, in particular 10 minutes, in particular 15 minutes. After reaching the target speed, the target speed can basically be set as desired, e.g. can be reduced again for fan run-on after cooking has ended, etc.

In a further development, the speed profile is specified in such a way that the cooling fan is ramped up to its target speed at the start of the operating sequence or at the start of its activation sequence.

It is a further development that the speed profile is specified in such a way that the cooling fan is ramped up to its target speed only after a delay time has elapsed.

It is a further development that the ramp has a linearly rising shape. However, the speed profile is not limited to this, and the ramp can take any increasing, in particular continuously increasing, form, e.g. a parabolic shape.

In the event that at least one cooling fan is a variable-speed cooling fan, one embodiment is that the cooling fan is operated at a low initial target speed between the start of the operating sequence and the end of the delay time or during the delay period. This has the advantage that a cooling air flow, albeit only a comparatively small one, is generated right from the start of the operating sequence, which develops a cooling effect with little user nuisance from the blown cooling air flow and the noise development.

It is an embodiment that the initial target speed corresponds to no more than 40%, in particular no more than 30%, in particular no more than 25%, in particular no more than 20%, of a maximum speed of the cooling fan. It has been found that this initial target speed results in a particularly good compromise between cooling performance and low user annoyance. It is a further development that the initial target speed corresponds to more than 10%, in particular more than 20%, in particular more than 25%, of a maximum speed of the cooling fan. An initial target speed in a range between 25% and 35% of the maximum speed of the cooling fan, in particular around 30%, is particularly advantageous.

1. a) Mit Beginn des Betriebsablaufs bleibt der Kühllüfter zunächst für eine Verzögerungszeit ausgeschaltet oder wird nur mit einer geringen initialen Drehzahl betrieben. Mit Ablauf der Verzögerungszeit(dauer) wird dem Kühllüfter sprunghaft seine Maximaldrehzahl vorgegeben bzw. dieser auf seine Maximaldrehzahl eingestellt.
2. b) Mit Beginn des Betriebsablaufs wird die Solldrehzahl des Kühllüfters mittels einer definierten Rampe auf seine Maximaldrehzahl hochgefahren.
3. c) Mit Beginn des Betriebsablaufs bleibt der Kühllüfter zunächst für eine Verzögerungszeit ausgeschaltet oder wird nur mit einer geringen initialen Drehzahl betrieben und folgend mittels einer definierten Rampe auf seine Maximaldrehzahl hochgefahren.
4. d) Abhängig davon, ob der Garraum kalt ist oder ein Folgebetrieb mit noch warmem Garraum / elektrischen Komponenten gestartet wird, wird mindestens ein Kühllüfter verzögert (mit einer Verzögerungszeit und/oder Rampe) hochgefahren, oder nicht.

Using the method described above, the following speed profiles in particular can be run through for at least one cooling fan:

1. a) When the operating sequence begins, the cooling fan initially remains switched off for a delay time or is only operated at a low initial speed. When the delay time (duration) has expired, the cooling fan is suddenly given its maximum speed or it is set to its maximum speed.
2. b) At the start of the operating sequence, the set speed of the cooling fan is increased to its maximum speed by means of a defined ramp.
3. c) At the start of the operating sequence, the cooling fan initially remains switched off for a delay time or is only operated at a low initial speed and then increased to its maximum speed using a defined ramp.
4. d) Depending on whether the cooking space is cold or a subsequent operation with the cooking space still warm / electrical components are started, at least one cooling fan is started up with a delay (with a delay time and / or ramp) or not.

The object is also achieved by a household cooking appliance with a cooking chamber, at least one cooling fan for cooling components arranged outside a cooking chamber, and a control device, the control device being set up to carry out the method as described above. The household cooking appliance can be designed analogously to the method and has the same advantages.

It is an embodiment that the at least one component comprises at least one electronic component, e.g. an electrical or electronic component (such as a diode, a capacitor, a battery, an integrated circuit, etc.), a motor, a light source, etc. It is a further development that the at least one component represents a component of an electronic circuit board. It is a development that the at least one component represents a component of a control device.

• 1 zeigt als Schnittdarstellung in Seitenansicht eine vereinfachende Skizze eines Haushalts-Gargeräts;
• 2 zeigt zwei mögliche Drehzahl-Sollprofile;
• 3 zeigt ein Diagramm einer Temperatur einer Gerätekomponente unter verschiedenen Kühlungssituationen.

The properties, features and advantages of this invention described above and the manner in which they are achieved will become clearer and more clearly understood in connection with the following schematic description of an exemplary embodiment which is explained in more detail in connection with the drawings.

• 1 shows, as a sectional illustration in side view, a simplified sketch of a household cooking appliance;
• 2 shows two possible speed target profiles;
• 3 shows a diagram of a temperature of a device component under different cooling situations.

1 shows a domestic cooking appliance as a sectional illustration in side view 1 with an outer casing 2 . The case 2 surrounds a cooking space 3 , the one by means of a door 4th lockable front loading opening 5 having. In a space 6th between a cooking chamber wall or muffle 7th and the case 2 various device components are housed, as shown here using a control device 8th and a microwave generator 9 shown as an example.

By means of the microwave generator 9 Microwaves can be generated that are used to cook food in the oven 3 fed in (not shown). The microwave generator 9 can be an inverter controlled microwave generator. The household cooking appliance can also 1 have one or more electrical resistance heating elements, one of which here is an upper heating element 10 is drawn. The microwave generator 9 and the resistance heating elements 10 can by means of the control device 8th controlled or activated.

The control device 8th and for example an inverter of the microwave generator 9 can have one or more electrical and / or electronic components or elements (not shown), which can be combined to form respective assemblies.

The control device 8th also controls at least one cooling fan, with exactly one cooling fan here 11 is drawn. The cooling fan switched on 11 sucks in ambient air, for example from a front side, a rear side, a left side and / or or a right side of the domestic cooking appliance 1 . Here, purely as an example, a suction on the front is shown. This ambient air flows as cooling air K through the space 6th and can cool one or more device components, eg the control device 8th , the microwave generator 9 etc. The used cooling air K is then back out of the household cooking appliance 1 blown out, advantageously from the front. The cooling fan 11 here is a variable-speed cooling fan.

The household cooking appliance 1 also has a temperature sensor for sensing a cooking space temperature (not shown) and a temperature sensor 12th for sensing a temperature of an ambient air.

mit n der Drehzahl des Kühllüfters 11, n_i einer initialen Drehzahl, ̇ṅ einer Steigung dn/dt der Drehzahl, n_Ziel einer Zieldrehzahl, t einer Zeitdauer seit Beginn des Betriebsablaufs, t_v einer Verzögerungszeit und t1 einer Zeit bis zum Erreichen der Zieldrehzahl n_Ziel . Dabei kann vorteilhafterweise $${\text{n}}_{\text{i}}=\left[0;\mathrm{0,3}\cdot {\text{n}}_{\text{max}}\right];$$

$${\text{t}}_{\text{v}}=\left[0;30\text{s}\right];$$

$${\text{n}}_{\text{Ziel}}=\left[\mathrm{0,7}\cdot {\text{n}}_{\text{max}};{\text{n}}_{\text{max}}\right]$$

$$\dot{\text{n}}\text{=}]0;\infty ]$$

gelten, und zwar mit nmax der maximalen Drehzahl des Kühllüfters 11. Speziell kann für mindestens einen Betriebsablauf erfüllt sein, dass nicht gleichzeitig t_v = 0 und ̇ṅ = ∞ (entsprechend einem sofortigen Einstellen der Drehzahl n nach Betriebsbeginn auf einen Sollwert n > 0,7 ·n_Ziel) gelten. Besonders vorteilhaft gelten t_v ≥ 5 s und/oder n_Ziel = nmax.The control device is set up, for example programmed, for a method for operating the domestic cooking appliance 1 to the effect that at least one cooling fan (here: the cooling fan 11 ) runs up or is run up with a delay with a speed setpoint profile that is fixedly predetermined at the beginning of an operating sequence. In particular, the target speed profile can have the following form (see also 2 ): $$\begin{array}{cc}n\left(t\right)=\{\begin{array}{l}{n}_i\hfill \\ \dot{n}\cdot \left(t-t_v\right)+n_i\hfill \\ n_{Ziel}\hfill \end{array}& \begin{array}{l}f\ddot{u}rt=\left[0;t_v\right]\hfill \\ f\ddot{u}rt=]t_v;t1\hfill \\ f\ddot{u}rt=[t1;\mathrm{...}\hfill \end{array}\end{array}$$

where n is the speed of the cooling fan 11 , n _i an initial speed, ̇ṅ a slope dn / dt of the speed, n _goal a target speed, t a period of time since the start of the operating sequence, t _v a delay time and t1 a time until the target speed is reached n _goal . It can be advantageous $${\text{n}}_{\text{i}}=\left[0;0.3\cdot {\text{n}}_{\text{Max}}\right];$$

$${\text{t}}_{\text{v}}=\left[0;\mathrm{30th}\text{s}\right];$$

$${\text{n}}_{\text{target}}=\left[0.7\cdot {\text{n}}_{\text{Max}};{\text{n}}_{\text{Max}}\right]$$

$$\dot{\text{n}}\text{=}]0;\infty ]$$

apply, namely with nmax the maximum speed of the cooling fan 11 . In particular, for at least one operating sequence it can be fulfilled that t _v = 0 and ̇ṅ = ∞ (corresponding to an immediate setting of the speed) are not simultaneously n after the start of operation to a nominal value n> 0.7 · n _target ) apply. It is particularly advantageous that t _v 5 s and / or n _target = nmax.

• - einer Betriebsart des Betriebsablaufs;
• - einer Zeitdauer seit Beendigung eines vorherigen Betriebsablaufs und/oder
• - mindestens einem unmittelbar vor Beginn des Betriebsablaufs gemessenen Sensormesswert, insbesondere einer Temperatur einer Umgebungsluft, einer Garraumtemperatur und/oder einer Komponententemperatur (insbesondere Elektrokom ponententem peratu r),

bestimmt werden. Ist das Drehzahl-Sollprofil bestimmt, wird es ab t = 0 (ggf. zuzüglich einer vernachlässigbar geringen Zeitdauer zu seiner Bestimmung) ohne weitere Änderungen durchgeführt.The fan operating parameters n , t _v , n _goal , t1 and / or ̇ṅ can for example be based on:

• - an operating mode of the operating sequence;
• - a period of time since the termination of a previous operating sequence and / or
• - at least one sensor measurement value measured immediately before the start of the operating sequence, in particular a temperature of an ambient air, a cooking space temperature and / or a component temperature (in particular electrical component temperature),

to be determined. Once the target speed profile has been determined, it is carried out from t = 0 (possibly plus a negligibly short period of time for its determination) without any further changes.

2 shows as a plot of a set target speed n as a percentage of a maximum speed nmax versus time t two possible speed target profiles since the start of an operating sequence P1 and P2 of the cooling fan 11 that follow the form described above.

For example, the target speed profile P1 can be selected if the cooking space is cold 3 present. Then, with the start of an operating sequence, here: a cooking sequence, the cooling fan is initially operated for t _v = 10 s at an initial speed n _i = 0.3 · n _max . After that the speed is n within 15 s to the maximum speed nmax as the target speed n _goal elevated. The associated slope ̇ṅ is constant here, purely as an example.

The speed target profile P2 can be selected if the cooking space is warm 3 present. That this is the case can be determined, for example, by measuring a cooking space temperature, a temperature of a device component and / or taking into account a period of time since the end of a previous operating sequence. In this case the delay time can be set to t _v = 0, and the cooling fan 11 immediately ramps up to the maximum speed n _max .

3 shows a diagram of a plot of an outside temperature text of a device component (eg a high-voltage diode) in ° C against time t in minutes since the start of an operating sequence under different cooling situations. The cooling situations are based on temperature curves for different delay times t _v shown, namely for t _v = 0 s, 30 s, 45 s, 60 s and 90 s. It is assumed that the cooling fan 11 when the delay time is reached or expired t _v is set abruptly to its maximum speed nmax. The temperature curves shown have been calculated using a thermal equivalent model, but can alternatively or additionally also be determined experimentally.

The temperature curves each show a temperature overshoot that occurs in the first few minutes, the height of which is more pronounced the greater the delay time t _v is. The temperature profiles then asymptotically approach the same final temperature Tend.

The delay time is advantageously t _v Designed until the fan starts so that the component end temperature Tend is not exceeded in the initial overshoot. In the family of curves shown, this is fulfilled by t _v = approx. 30 s.

In contrast to known solutions, the performance of the cooling fan or cooling fan is not affected here 11 a measured temperature signal is tracked, but it is based on the fixed specifications of the device components to be cooled, a waiting or delay time that is as long as possible t _v and / or a minimum required initial target speed n _i determined so that the thermal specification limits of all components are adhered to in the further course of operation. In order to be able to approach the thermal limits as closely as possible, it is advantageous to initially record the temperature of the ambient air sucked in once before the start of operation, since the cooling efficiency is lower at higher ambient temperatures. However, this does not represent a temperature-controlled fan operation, but only serves for a more precise advance calculation of the fan operating parameters n _i , t _v , n _goal , t1 and or n .

Of course, the present invention is not limited to the embodiment shown.

In general, “a”, “one” etc. can be understood to mean a singular or a plurality, in particular in the sense of “at least one” or “one or more” etc., unless this is explicitly stated excluded, e.g. by the expression "exactly one" etc.

A number can also include exactly the specified number and a customary tolerance range, as long as this is not explicitly excluded.

List of reference symbols

1

Household cooking appliance

2

casing

3

Cooking space

4th

door

5

Loading opening

6th

Space

7th

Grouch

8th

Control device

9

Microwave generator

10

Top heat radiator

11

Cooling fan

12

Temperature sensor

K

Cooling air

n

Speed of the cooling fan

n _i

Initial speed

n _max

Maximum speed

n _goal

Target speed

̇Ṅ

Increase in speed

P1

Speed target profile

P2

Speed target profile

T _ext

External component temperature

T _end

Asymptotic external component end temperature

t

time

t _v

Delay Time

t1

Time to reach the target speed.

QUOTES INCLUDED IN THE DESCRIPTION

This list of the documents listed 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

• DE 10128370 A1 [0004]
• EP 2287533 A1 [0005]
• EP 2705305 B1 [0006]
• WO 2013/098002 A1 [0007]
• US 5777897 [0008]
• US 5688422 [0009]

Claims (15)

Method for operating a household cooking appliance (1) with at least one cooling fan (11) for cooling at least one component (8, 9) arranged outside a cooking space (3), in which at least one cooling fan (11) is fixed at the start of the operating sequence specified speed target profile (P1, P2) starts up with a delay. Procedure according to Claim 1 , the speed setpoint profile (P1, P2) at the start of the operating sequence based on: - an operating mode of the operating sequence; - a period of time since the termination of a previous operating sequence and / or - at least one sensor measurement value measured immediately before the start of the operating sequence is determined. Procedure according to Claim 2 , in which the at least one sensor measured value comprises a value of a temperature of an ambient air. Method according to one of the Claims 2 to 3 , in which the at least one sensor measured value comprises a value of a cooking space temperature. Method according to one of the Claims 2 to 4th , in which the at least one measured sensor value comprises a value of a temperature of a device component (8, 9). Procedure according to Claim 1 , in which the target speed profile is the same for all operating sequences. Method according to one of the preceding claims, in which the target speed profile (P1) comprises a delay time (t _v ) between the start of the operating sequence and the start of the cooling fan (11) running up. Procedure according to Claim 7 , in which the delay time (t _v ) is up to 45 seconds, in particular up to 30 seconds. Method according to one of the preceding claims, in which the cooling fan is a fan with a fixed setpoint speed. Method according to one of the Claims 1 to 8th , wherein the cooling fan (11) is a variable-speed cooling fan and is started up with a predetermined speed gradient (ṅ). Procedure according to the Claims 7 or 8th and Claim 10 , in which the cooling fan (11) is operated between the start of the operating sequence and the end of the delay time (t _v ) at a low initial setpoint speed (n _i ). Procedure according to Claim 11 , at which the initial target speed (n _i ) corresponds to no more than 40%, in particular no more than 30%, of a maximum speed (nmax) of the cooling fan (11). Method according to one of the Claims 10 to 12th , wherein a target target speed (n _target ) reached after starting up a speed (n) of at least 70%, in particular of at least 80%, in particular of at least 90%, in particular of 100%, of a maximum speed (nmax) of the cooling fan (11 ) corresponds. Domestic cooking appliance (1) with a cooking chamber (3), at least one cooling fan (11) for cooling components (8, 9) arranged outside a cooking chamber (3) and a control device (8), the control device (8) being set up for this purpose is to carry out the method according to one of the preceding claims. Household cooking appliance (1) according to Claim 14 wherein the at least one component (8) comprises at least one electronic component.

Images