EP2769155B1 - Refrigeration appliance comprising an evaporation tray and a heating device for promoting evaporation - Google Patents

Description

The present invention relates to a refrigeration appliance, in particular a household refrigeration appliance such as a refrigerator or freezer, with an evaporation tray for the evaporation of condensate derived from a storage chamber of the device and a heater which is operable to, if necessary, the evaporation of condensate in the evaporation tray promote.

The condensate, which is reflected in the storage chamber, reaches there via stored refrigerated goods as well as in the form of water vapor, which is contained in the entering each time the door of the refrigerator in the storage chamber ambient air. The extent of the water entry, and thus the rate at which it flows out of the storage chamber of the evaporation tray, is difficult to estimate, as it depends on numerous factors such as type of refrigerated goods and its packaging, temperature and percentage humidity of the ambient air and the amount of Door opening between the environment and storage chamber exchanged air dependent, and various of these sizes are barely measurable with reasonable effort.

The construction of the refrigeration unit must ensure that the condensation water of the evaporation tray evaporates quickly enough to reliably prevent overflow, which could damage the refrigeration unit and its surroundings.

Conventionally, such an evaporation tray is usually mounted on a compressor of the refrigerator to heat with its waste heat the condensation in the evaporation tray and to promote its evaporation. Improvements in insulation and cooling, however, in modern refrigerators result in the ratio of accumulating condensate to the waste heat available at the compressor becoming increasingly unfavorable. In order to still keep the evaporation tray at a sufficient evaporation to ensure a temperature, it has been proposed to use an electric heater for heating the condensed water. However, the power consumption of such affects Heating device massively the overall energy efficiency of the refrigerator. Their use is therefore to be limited to times when this is essential for preventing the overflow of the evaporation tray. In order to control the heater suitable, it is therefore necessary to monitor the water level in the evaporation tray.

A refrigerator according to the preamble of claim 1 is made WO 2005/090878 known.

Out JP 2009-085473 A a refrigeration device has become known in which a arranged on the evaporation tray temperature sensor is used to gain information about the water level. If, during the defrosting of this conventional refrigeration appliance, condensate enters the evaporating dish in large quantities, a heating device is started in order to evaporate the resulting water, and the resulting heating is monitored. As long as there is water in the shell, the warming is slow. The shell is heated to a maximum temperature, then allowed to cool to a minimum temperature, and reheated. When the rate of temperature rise in the heating phase exceeds a threshold, it is considered that there is no more water in the evaporation tray, and heating of the tray is stopped. To remove condensation that enters the evaporation tray between defrosts, it is heated from time to time, and the temperature rise rate measured determines whether or not the tray contains water that needs to be evaporated.

This regular check requires a considerable amount of energy, which affects the efficiency of the refrigeration device. In particular, the larger the shell, the larger the amount of energy required to heat the shell. However, a large shell is desirable to provide a large evaporation surface over which condensation can evaporate without additional electrical heating.

Since during the evaporation operation, the temperature must fluctuate greatly to check at regular intervals by the rate of increase in temperature, whether the shell still contains water, the average temperature during the evaporation operation is significantly lower than the maximum temperature. Accordingly, the average evaporation rate is also significantly lower than the evaporation rate at the maximum temperature. Furthermore, the one needed to achieve the maximum temperature Heating device significantly more powerful than a heater that achieves the same evaporation effect by keeping the evaporation tray constant at a medium temperature.

The object of the present invention is to minimize the energy consumption of the heating device in a refrigeration device with a heatable by a heater evaporation tray.

The object is achieved by providing in a refrigeration appliance, in particular a household refrigeration appliance, with at least one storage chamber, an evaporation tray for evaporating condensate discharged from the storage chamber, a temperature sensor arranged on the evaporation tray, a control unit connected to the temperature sensor, and a heating device which is heated by the Control unit is operable to increase the evaporation rate in the evaporation tray, the control circuit is arranged to decide on a continuation or non-operation of the heater by changing the temperature detected by the temperature sensor during a measurement operation phase of the heater and an evaporation operation phase of the heater in which the Evaporating tray is heated above the highest measured in the measuring phase of operation temperature, only to initiate when the change is weaker than a first limit. In this way, since the temperature rise in the measurement operation phase can be limited to a few degrees, checking whether the evaporation tray contains dew water in an amount that requires heating requires little energy.

If the measurement operation phase results in sufficient water in the evaporation tray to justify operation of the heater then the evaporation operation phase should be as promptly as possible, without intermediate cooling of the evaporation tray, following the measurement operation phase so that the heat energy expended for the measurement operation phase is not lost unused ,

The extent to which the measured temperature change is below the first limit is a quantitative measure of the amount of water in the evaporation tray. The control circuit can therefore be set up expediently, the duration of an evaporation operating phase following the measurement operation phase the heating device on the basis of the level below the limit. In this way it can be ensured that a single evaporation operating phase is sufficient to reduce the amount of water in the evaporation tray to a permissible level, and energy losses due to a cooling of the tray between two short consecutive evaporation operating phases can be avoided. Moreover, with a continuously high evaporation temperature, a higher evaporation rate is achievable than with a fluctuating temperature, so that a high level of water in the evaporation tray can be allowed before the heater must be used to clear the water. Thus, especially when other sources of heat, in particular waste heat, are available for heating the evaporation tray, the frequency with which the heating device must be operated is reduced.

In order to use the waste heat, which is generated in particular by a compressor of the refrigerator, the evaporation tray is preferably mounted on the compressor.

Preferably, the control circuit is further configured to determine, after an evaporation operation phase, the rate of decrease of the temperature sensed by the sensor, and to begin another phase of evaporation operation when the rate of decrease is below a second limit. Too slow a decrease in temperature indicates the presence of a large amount of water in the shell. Such a measurement of the rate of decrease of the temperature is particularly useful if the duration of the evaporation operating phase has not been determined as described above as a function of the results of the measurement operation phase, but is fixedly predetermined.

It is also conceivable to define a third limit value for the temperature change in the measuring operation phase and, if the deviation has fallen below the third limit value, after a short time, if the third limit value is not exceeded after a longer time, to repeat the measuring operation phase. If a shortfall of the third limit value indicates a large amount of water in the evaporation tray which can not be eliminated in a single phase of the evaporation operation, then after a short time recheck if the water level in the evaporation tray is at a critical level, and re-heat if necessary to accelerate evaporation.

The third limit may be equal to the first limit or lower.

The duration of the measurement operation phase can be fixed, and as a measure of the change in the temperature in the measurement operation phase, the difference between the temperature at the beginning of the measurement operation phase and the temperature at the end of the measurement operation phase can be formed.

A temperature change in the measuring operation phase of less than 10 K, preferably even less than 6 K, has proven to be sufficient to reliably assess the water level in the evaporation tray can.

The duration of the measuring operation phase can then be selected between 5 and 30 minutes.

Alternatively, the control unit may also be arranged to terminate a measurement operation phase if the difference between the measured and the actual temperature measured at the beginning of the measurement operation phase is a target value of e.g. has reached up to 10 K or up to 6 K, and the shorter the measurement operation phase has been, the more the temperature change is judged. In this way, since the time required to reach the target value of the temperature is shorter, the less water the shell contains, the energy expenditure for a filling level assessment can be accelerated by the heating device, in particular in cases where the water level is low and the evaporation must be reduced.

Also, a fluctuating supply voltage can greatly affect the rate of increase of the temperature in a measuring operation phase or the temperature increase achieved over a given period of time. In order to avoid a falsification of water level measurements, the control unit comprises means for estimating the supply voltage, and the first limit value or the duration of the measuring operating phase is predetermined as a function of the supply voltage.

• in einer Messbetriebsphase Beheizen der Verdunstungsschale und Beurteilen des Wasserstands anhand der aus dem Beheizen resultierenden Änderung einer an der Verdunstungsschale gemessenen Temperatur;
• Einleiten einer Verdunstungsbetriebsphase der Heizeinrichtung, in der die Verdunstungsschale über die höchste in der Messbetriebsphase gemessene Temperatur hinaus erhitzt wird, wenn die Änderung schwächer als ein erster Grenzwert ist.

The object is further achieved by a method for monitoring the water level in an evaporation tray of a refrigeration appliance, in particular as is carried out by the control unit of the refrigeration appliance described above, with the following steps:

• in a measuring operation phase, heating the evaporation tray and evaluating the water level based on the change of a temperature measured at the evaporation tray resulting from the heating;
• Initiating an evaporation operation phase of the heater in which the evaporation tray is heated above the highest temperature measured during the measurement operation phase when the change is weaker than a first limit value.

Fig. 1

einen schematischen Schnitt in Breitenrichtung durch ein Haushaltskältegerät gemäß der vorliegenden Erfindung;

Fig. 2

einen Schnitt in Tiefenrichtung durch das Kältegerät;

Fig. 3

einen exemplarischen zeitlichen Verlauf der Temperatur der Verdunstungsschale des Kältegeräts aus Fig. 1 und 2;

Fig. 4

ein Flussdiagramm eines Verfahrens zum Steuern der Heizeinrichtung des Kältegeräts, durch das sich der in Fig. 3 gezeigte Temperaturverlauf ergeben kann, gemäß einer ersten Ausgestaltung der Erfindung;

Fig. 5

ein Flussdiagramm eines Verfahrens zum Steuern der Heizeinrichtung gemäß einer zweiten Ausgestaltung; und

Fig. 6

einen alternativen Ablauf der Messbetriebsphase des Verfahrens gemäß Fig. 4 oder Fig. 5.

Further features and advantages of the invention will become apparent from the following description of embodiments with reference to the accompanying figures. From this description and the figures also show features of the embodiments, which are not mentioned in the claims. Such features may also occur in combinations other than those specifically disclosed herein. Therefore, the fact that several such features are mentioned in the same sentence or in a different type of textual context does not justify the conclusion that they can occur only in the specific combination disclosed; instead, it is generally to be assumed that it is also possible to omit or modify individual ones of several such features, provided this does not call into question the functionality of the invention. Show it:

Fig. 1

a schematic section in the width direction by a household refrigerator according to the present invention;

Fig. 2

a section in the depth direction by the refrigerator;

Fig. 3

an exemplary time profile of the temperature of the evaporation tray of the refrigerator Fig. 1 and 2 ;

Fig. 4

a flowchart of a method for controlling the heating device of the refrigerator, through which the in Fig. 3 shown temperature profile, according to a first embodiment of the invention;

Fig. 5

a flowchart of a method for controlling the heating device according to a second embodiment; and

Fig. 6

an alternative sequence of Meßbetriebsphase the method according to Fig. 4 or Fig. 5 ,

Fig. 1 and 2 show schematic sections through a household refrigerator, in which the present invention is applicable. The sectional planes of the two figures are shown in the other figure as a dotted line II or II-II.

The household refrigerator, here a refrigerator, has in the usual way a heat-insulating housing with a body 1 and a door 2, which limit a storage chamber 3. The storage chamber 3 is here cooled by a coldwall evaporator 4 arranged on its rear wall between an inner container of the body 1 and an insulating foam layer surrounding it, but it should be immediately obvious to the person skilled in the art that the special features of the invention explained below also apply in connection with FIG any other types of evaporator, in particular a Nofrost evaporator, are applicable. Also conceivable is the application to a Nofrost freezer, since this, at least in a defrosting phase of the evaporator, also discharges condensation.

In the case of the Coldwall refrigeration device considered here, at the foot of the rear wall of the storage chamber 3 cooled by the evaporator 4, there extends a collecting channel 7, which collects condensed water, which deposits on the region of the inner container cooled by the evaporator 4 and flows downwards there. A pipeline 8 leads from the lowest point of the gutter 7 through the insulating foam layer through to an evaporation tray 9, which is mounted in a machine room 5 on a housing of a compressor 6 to be heated by waste heat of the compressor 6. In a Nofrost refrigeration appliance, a corresponding pipeline could emanate from the bottom of a chamber receiving the evaporator.

An electric heater 10 is shown here in the form of a heating loop extending in the interior of the evaporation tray 9; it could also be mounted, for example, in the form of a film heater on an outer wall 11 of the evaporation tray 9, in which case an insulation layer can still be provided around the film heater outside, in order to ensure that the heater essentially releases its heat into the evaporation tray 9 ,

In order to promote the evaporation of condensate in the evaporation tray 9, in addition to the heater 10, a fan 12 may be arranged in the engine room 5 so that it drives an air flow over the water level of the evaporation tray 9.

Heating device 10 and fan 12 are controlled by an electronic control unit 13, which is shown here for simplicity in the engine room 5, but in practice largely arbitrarily on the refrigerator and in particular adjacent to a - not shown - control panel can be arranged. In the simplest case, the control unit 13 switches the heating device 10 and the fan 12 on and off at the same time; It is also conceivable to let the fan 12 run after switching off the heating device 10 for a while to exploit heat that is still present in the water of the evaporation tray 9 at this time, for the evaporation. The control unit 13 is connected to a temperature sensor 15, which is mounted in or on the evaporation tray 9 and is in thermal contact with condensation water in the evaporation tray 9, if any.

The same control unit 13 can also control the operation of the compressor 6 on the basis of a temperature sensor 14 arranged on the bearing chamber 3.

Condensation can more or less continuously, or, if the evaporator 4 cools in an operating phase of the compressor 6 below 0 ° C and thawed again during the standstill of the compressor 6, in time of the operating phases of the compressor 6 flow from the storage chamber 3 into the evaporation tray 9 , In order to use the waste heat of the compressor 6 efficiently, it is expedient to store a large amount of water in the evaporation tray, which keeps the heat long and has a large free surface for evaporation. On the other hand, the water level should not be so high be that in the case of a strong inflow from the storage chamber 3, the evaporation tray 9 overflows. It is therefore necessary to be able to estimate the amount of water in the evaporation tray 9 to judge whether it is necessary to heat the water in the evaporation tray 9 by the heater 10 so as to accelerate the evaporation and avoid overflow. For this purpose, the control unit 13 tests from time to time the water level in the evaporation tray by turning on the heater 10 and monitored by means of the temperature sensor 15, the resulting change in temperature of the evaporation tray 9.

In the simplest case, this measurement of the water level can take place at regular intervals. In a preferred embodiment, the waiting time between two measurements may vary under certain conditions: If at a time when the nominal waiting time has expired, the compressor is in operation, it also contributes to the heating of the water in the evaporation tray, so that one this time measurement would give a wrong result. Even some time after the compressor is switched off, this still gives off heat to the evaporation tray and possibly drives a convection movement of the water in the tray, which can lead to heat emitted by the heater 10 reaching the temperature sensor 15 faster or slower than in the case in that, when the heating device 10 is switched on, the compressor 6 is cold and the water in the evaporation tray 9 is at rest.

Therefore, waiting for the end of the nominal waiting time of the compressor 6 in operation or even from a previous hive, waiting for a predetermined period of time from turning off the compressor 6 before it turns on the heater 10 for measuring the water level.

Alternatively, the water level measuring control unit 13 may turn on the heater 10 each at a compressor start or at a predetermined delay to a compressor start. Thus, the waste heat from the compressor 6 contributes to the measured temperature rise, and the power of the heater 10 needed to achieve a given temperature rise is lower, which in turn improves the overall efficiency of the device. In addition, a scarce and Accordingly, inexpensive compressor can be used, which is frequently and long lasting in operation, since no long periods of inactivity of the compressor for the water level measurement are needed.

If the refrigerator has an automatic defrost, especially in a NoFrost device, condensate enters the evaporation tray 9 every time the evaporator is defrosted. As a result, the temperature of the water in the evaporation tray 9 can drop significantly below that of the surrounding machine room 5, and heating the water takes place without the help of the heater 10 by temperature compensation with the surrounding engine room. Also this temperature compensation can falsify a measurement of the water level. Therefore, in these refrigerators, the control unit 13 is set up, a water level measurement, which is pending at a time to be expected because of a current or recent defrosting temperature changes in the evaporation tray 9, suspend until these temperature changes are subsided again.

Since a power failure depending on its duration can lead to the defrosting of the evaporator, but does not have to, there is a risk that the water level in the evaporation tray 9 after a power failure is significantly higher than before. To possibly counteract too high a level of water in time, according to another development, the control unit 13 has means for detecting a past power failure and is set up when a power failure has been detected, immediately perform a measurement of the water level.

Fig. 3 shows the temperature profile of the evaporation tray 9 detected by the sensor 15 in the course of several water level measurements. For the sake of clarity of presentation, times in which the temperature of the evaporation tray is increased by the operation of the compressor 6 and therefore water level measurements are excluded are shown in the diagram of FIG Fig. 3 hidden. At time t0, when the heating device 10 is switched on by the control unit 13, a first measuring operating phase begins. The water level in the evaporation tray 9 is low, and the evaporation tray heats up accordingly fast. At the end of the measurement phase, the temperature has increased by more than dTmin. The water level is considered uncritical assessed. The heater 10 is turned off again, and the evaporation tray 9 cools down again.

Until the beginning of a further measuring operation phase at time t2, a little more condensed water has collected in the evaporation tray, and the temperature rise is visibly slowed down. However, it is still fast enough to exceed the threshold dTmin at the end of the measurement operation phase, at time t3 (= t2 + Δt1), and so again at the end of the measurement operation phase at time t3, the heater 10 is turned off.

At the beginning of a third measuring operation phase, at the time t4, the amount of condensed water is increased so much that until the time t5 (= t4 + .DELTA.t1), a temperature increase by dTmin is no longer achieved. Only now joins an evaporation operation phase in which the heater 10 remains turned on. In a first part of the evaporation phase of operation, the heater runs continuously at high power, and the temperature continues to rise to a maximum permitted value Tmax. While dTmin is generally below 10K, and preferably even below 6K, the temperature rise in the vaporization phase of operation may easily be as high as 10K.

In order to keep the temperature of the evaporation tray approximately constant at Tmax in the second part of the evaporation phase of operation, a thermostat control can take place based on the measurement value of the temperature sensor 15, i. the control unit 13 switches off the heating device 10 when Tmax is exceeded, and switches it on again if Tmax - ε is undershot, where ε is a small positive value, and preferably smaller than dTmin.

At time t6, the control unit 13 terminates the evaporation operation phase by turning off the heater 10. The temperature goes back to T0 over time, and the temperature in Fig. 3 cycle shown repeats itself.

Fig. 4 FIG. 4 is a flowchart showing a working procedure of the control unit 13 whose execution is similar to that in FIG Fig. 3 can show the temperature profile shown. The process starts measuring the exit temperature T0 of the evaporation tray 9 at the beginning of a measuring operation phase in step S1. The heating device 10 is switched on (step S2) and the control unit 13 waits for the predetermined duration .DELTA.t1 of the measuring operation phase (step S3), before it receives a further temperature measurement T1 in step S4. In step S5, the temperature change T1-T0 attained during the measuring operation phase is subtracted from the threshold value dTmin. If the difference dT thus obtained is negative, then in the course of the measurement operation phase, the temperature in the evaporation tray has increased more than dTmin, corresponding to the measurement operation phases [t0, t1] and [t2, t3] Fig. 2 , In this case, the method branches from step S6 to S7, where the heater 10 is turned off again, and in step S8, a predetermined period of time .DELTA.t2 that is many times longer than .DELTA.t1 is awaited before the start of a new measurement phase.

If it is determined in step S6 that dT is greater than or equal to 0, corresponding to the case of the measuring operation phase [t4, t5] Fig. 3 , then the process goes into an evaporation operation phase by the heater remains switched on at the end of the measuring operation phase. In step S9, a time period .DELTA.t3 is awaited before the process goes to step S7 and thus ends the Heizbetriebsphase. As in Fig. 3 For a first part of the period .DELTA.t3, the heater can operate continuously to heat the shell to Tmax and intermittently operate in a second part to maintain it at that temperature.

The duration .DELTA.t3 of the evaporation operating phase can be fixed. In this case, at the end of the evaporation operation phase, it is not certain that the water level in the evaporation tray 9 has been lowered to a safe level. Therefore, in this case, it is appropriate to make the waiting time Δt2 of the step S8 considerably shorter following an evaporation operation phase than in the case that no evaporation operation phase has taken place.

Another possibility is in Fig. 5 shown. The steps S1 to S9 of the flowchart shown there are with those of Fig. 4 identical and will not be described again. When the heater 10 is turned off after the end of the evaporation operation phase in step S10, a temperature reading T0 is also taken in again (step S11), and a second temperature reading T1 is taken after waiting the time period Δt1 (S12) in step S13. In step S14, the difference T0-T1 becomes a second limit dTmin 'compared. If the difference is smaller than the limit dTmin ', ie, the temperature slowly decreases, then this is an indication that the amount of water in the evaporation tray 9 is still large. In this case, as shown, the method may jump back directly from S14 to S1 to repeat the measurement operation phase and finally decide at the end of it in step S6 whether an evaporation operation phase is still to be connected. Alternatively, if the step falls below the threshold value dTmin ', the heater 10 may unconditionally be turned on again and jumped back to the step S9 to repeat the evaporation operation phase.

However, if the comparison of step S14 indicates a rapid drop in temperature, the amount of residual water in the evaporation tray 9 is apparently small, and the process returns to step S8.

Another alternative is in the process of Fig. 4 determine the duration .DELTA.t3 of the evaporation phase of operation as a function of dT: the larger dT is, the more the temperature rise in the measuring operation phase has lagged behind the limit value dTmin, and the larger the amount of water in the evaporation tray 9 must be. The relationship between dT and the amount of water in a given refrigerator model can be determined empirically. Based on such empirical data, it is possible to set Δt3 as a function of dT such that the time period Δt3 is exactly sufficient to lower the water level in the evaporation tray 9 to an uncritical value.

Fig. 6 shows an alternative embodiment of the measuring operation phase, which is applicable to all the above-described embodiments of the operating method of the control unit 13. Steps S1 and S2 of measuring the output temperature T0 and turning on the heater 10 at the beginning of the measuring operation phase are the same as those described with reference to FIG Fig. 4 described. In addition, simultaneously with turning on the heater and measuring the temperature T0, a timer is started (step S3 '). The temperature T of the evaporation tray 9 is then continuously monitored until it has risen by at least dTmin (S4 '). Once this is the case, the timer is read in step S5 '. A low measured value t of the timer, below a limit value tmax, shows a rapid increase in temperature or a Low water level, and it follows the step S7, as with reference to Fig. 4 described. A time reading t> tmax, corresponding to a slow rise, indicates the exceeding of the critical water level in the evaporation tray 9, so that the process proceeds to step S9 as described with reference to FIG Fig. 4 or 5 described.

The power of the electric heater 10 is proportional to the square of the supply voltage applied thereto. If this voltage is the mains voltage or a voltage derived from the mains voltage proportional to it, fluctuations in the mains voltage have a strong effect on the measured rate of temperature change and can significantly falsify the estimation of the amount of water in the evaporation tray 9. According to a further developed embodiment, therefore, the control unit is equipped with a voltage sensor for detecting the supply voltage of the heating device. Variations in the supply voltage can then be compensated in different ways. For example, in the method according to Fig. 4 or 5 the duration .DELTA.t1 of the measuring operation phase are set in inverse proportion to the square of the supply voltage, so that the amount of heat released in each measuring operation phase is the same regardless of the exact value of the supply voltage. Alternatively, the limit value dTmin can be set directly proportional to the square of the supply voltage. Then, the duration of the measuring operation phase is independent of the value of the operating voltage, but at low voltage, the limit value of the temperature rise, below which an excessively high, heating water level is detected, adjusted according to the reduced amount of heat released.

Claims (16)

1. Refrigeration appliance, in particular domestic refrigeration appliance, having at least one storage chamber (3), an evaporation tray (9) for evaporating condensation water discharged from the storage chamber (3), a temperature sensor arranged on the evaporation tray (9), a control unit (13) connected to the temperature sensor and a heating device (10), which can be operated by the control unit (13), in order to increase the evaporation rate in the evaporation tray (9), wherein the control circuit (13) is configured to make a decision on a further operation or non-operation of the heating device (10) (S6, S6') on the basis of a change (T1-T0) in the temperature (T0, T1) acquired by the temperature sensor (15) during a measuring operation phase ([t0, t1], [t2, t3], [t4, t5]; S1-S5, S1-S5') of the heating device (13), characterised in that the control circuit (13) is configured to only introduce an evaporation operation phase ([t5, t6]; S9) of the heating device (10), in which the evaporation tray (9) is heated to beyond the highest temperature (T1) measured in the measuring operation phase if the change (T1, T0) is weaker than a first limit value (dTmin).
2. Refrigeration appliance according to claim 1, characterised in that the control circuit is configured to allow the evaporation operation phase ([t5, t6]; S9) to follow the measuring operation phase ([t4, t5]; S1-S5, S1-S5') without intermediate cooling of the evaporation tray (9).
3. Refrigeration appliance according to claim 1 or 2, characterised in that the control circuit is configured to define the duration (Δt3) of an evaporation operation phase ([t5, t6]; S9) of the heating device (10) following the measuring operation phase ([t4, t5]; S1-S5, S1-S5') on the basis of the extent (dT) of the exceedence of the limit value (dTmin).
4. Refrigeration appliance according to one of the preceding claims, characterised in that the evaporation tray (9) is mounted on a compressor (6).
5. Refrigeration appliance according to one of claims 1 to 4, characterised in that the control circuit (13) is configured, after an evaporation operation phase ([t5, t6]; S9), to determine the take-up speed of the temperature acquired by the sensor (S11-S13) and to begin a further evaporation operation phase (S 14) if the take-up speed lies below a second limit value (dTmin').
6. Refrigeration appliance according to one of claims 1 to 4, characterised in that the control circuit (13) is configured to select the time interval (Δt2) between the measuring operation phase ([t0, t1], [t2, t3], [t4, t5]; S1-S5, S1-S5') and a subsequent measuring operation phase ([t2, t3], [t4, t5], S1-S5, S1-S5') to be long if the change has not reached a third limit value and to select the time interval (Δt2) to be short if the deviation has not reached the third limit value (dTmin).
7. Refrigeration appliance according to one of the preceding claims, characterised in that the duration (Δt1) of the measuring operation phase ([t0, t1], [t2, t3], [t4, t5]; S1-S5) is predetermined and that the change between temperatures (T0, T1) acquired by the temperature sensor (15) during a measuring operation phase ofthe heating device (10) is the difference (T1-T0) between the temperature (T0) at the start (t0, t2, ...) of the measuring operation phase and the temperature (T1) at the end (t1, t3,...) of the measuring operation phase.
8. Refrigeration appliance according to claim 7, characterised in that the first limit value (dTmin) is below 10K, preferably below 6K.
9. Refrigeration appliance according to claim 7 or 8, characterised in that the predetermined duration (Δt1) of the measuring operation phase is selected in the range between 5 and 30 min.
10. Refrigeration appliance according to one of claims 7 to 9, characterised in that the control unit (13) comprises means for estimating a supply voltage and that the first limit value (dTmin) or the duration (Δt1) of the measuring operation phase ([t0, t1], [t2, t3], [t4, t5]; S1-S5) is predetermined as a function of the supply voltage.
11. Refrigeration appliance according to one of claims 1 to 6, characterised in that the control unit is configured to terminate a measuring operation phase (S1-S5') if the difference (T1-T0) between the temperature (T0) measured at the start of the measuring operation phase and the current temperature (T) has reached a desired value (dTmin) (S4'), and the temperature change is considered to be more significant, the shorter the measuring operation phase (S1-S5').
12. Refrigeration appliance according to one of the preceding claims, characterised in that the control unit is configured not to implement a measuring operation phase with an operating compressor (6).
13. Refrigeration appliance according to one of claims 1 to 11, characterised in that the control unit is configured to perform a measuring operation phase with a predetermined time offset at the start of the compressor (6).
14. Refrigeration appliance according to one of the preceding claims, characterised in that the control unit is configured not to perform a measuring operation phase during a condensation process.
15. Refrigeration appliance according to one of the preceding claims, characterised in that the control unit is configured to perform a measuring operation phase after a power failure in each case.
16. Method for monitoring the water level in an evaporation tray of a refrigeration appliance having the steps:

    - in a measuring operation phase ([t0, t1], [t2, t3], [t4, t5]; S1-S5, S1-S5'), heating the evaporation tray (9) and assessing the water level based on the change (T1-T0, T-T0) in a temperature measured on the evaporation tray (9) as a result of the heating process;

    - introducing an evaporation operation phase ([t5, t6]; S9) of the heating device (10), in which the evaporation tray (9) is heated to beyond the highest temperature (T1) measured in the measuring operation phase ([t0, t1], [t2, t3], [t4, t5], S1-S5, S1-S5') if the change is weaker than a first limit value (dTmin).

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