DE102015211961A1 - Refrigeration appliance and operating method for it - Google Patents

Abstract

A refrigeration appliance, in particular a household refrigerating appliance, comprises at least one storage chamber (2), a temperature sensor (10) for detecting the temperature (Ti) of the storage chamber (2), an evaporator (6) for cooling the storage chamber (2), a compressor (3 ) and a control unit (9) for switching on the compressor (3) when the temperature (Ti) of the storage chamber (2) rises above a switch - on threshold (Tein) and for switching off the compressor (3) when the temperature (Ti) of the compressor Storage chamber (2) falls below a switch-off threshold (Taus). A hysteresis (H) between the switch-on threshold (Tein) and the switch-off threshold (Taus) is variable, in particular depending on at least one of the following criteria:
- outside temperature,
Ratio of switch-on times to switch-off times of the compressor (3),
- Time elapsed since the evaporator last defrosted.

Description

The present invention relates to a refrigeration device, in particular a household refrigerator such as a refrigerator, a freezer or a fridge-freezer combination, and an operating method for such a refrigerator.

Conventional refrigerators usually have a refrigerant circuit in which a compressor, a condenser and an evaporator are connected in series, and in which the compressor is turned on when the temperature in the storage chamber of the refrigerator exceeds a switch-on, and is switched off again as soon as a Switch-off threshold of the temperature is exceeded. The hysteresis of the temperature, i. the difference between the switch-on threshold and the switch-off threshold determines the duration of the switch-on times or switch-off times of the compressor. The greater the hysteresis, the longer the turn-on and turn-off times, and the less likely it is to equalize the pressure between the high-pressure and low-pressure parts of the refrigerant circuit when the compressor is switched off, which affects the efficiency of the refrigeration because, on the one hand, warm refrigerant enters the evaporator On the other hand, the pressure difference between the high-pressure and low-pressure parts of the refrigerant circuit, which is required for refrigeration, has to be rebuilt each time the compressor is started.

It is therefore desirable for a good efficiency of the refrigerator that the turn-on and off times are not too short; However, an excessively long switch-on time of the compressor is again disadvantageous for the efficiency of the refrigeration, since in the course of such a long operating time the evaporator can reach a temperature which is significantly below the temperature of the storage chamber to be cooled. One consequence of the low evaporator temperature is on the one hand an increased heat flow through the heat-insulating housing of the refrigerator from the environment to the evaporator and on the other hand a high pressure difference in the refrigerant circuit against which the compressor has to work. Both lead to increased energy consumption.

Conventional refrigerators therefore operate with a value of the hysteresis, which in the simplest case, taking into account the above-explained aspects roughly estimated, is optimally optimized empirically for a given model of refrigerator.

Even the most careful optimization must be based on assumptions about the operating conditions of the refrigeration device, in particular on the ambient temperature, with the result that a value of the hysteresis obtained in such an optimization achieves a high level of efficiency even under the conditions assumed for the optimization can guarantee. If the operating conditions of the refrigeration device deviate from the conditions of optimization, then it is to be expected that only sub-optimal efficiency will be achieved.

The object of the invention is to provide a refrigeration device and an operating method for it, which enable operation of the refrigeration device with high efficiency even under different environmental conditions.

The object is achieved in which in a refrigerator, in particular a household refrigerator, with at least a first storage chamber, a temperature sensor for detecting the temperature of the first storage chamber, in the first evaporator for cooling the first storage chamber, a compressor and a control unit that turns on the compressor if the temperature of the first storage chamber rises above a switch-on threshold and the compressor switches off again when the temperature of the first storage chamber falls below a switch-off threshold, a hysteresis between the switch-on threshold and the switch-off threshold is variable. Thus, depending on the conditions under which the refrigeration device operates, in each case a value of the hysteresis can be selected, which enables energy-efficient operation.

If, for example, the control unit can be switched over between a normal cooling mode and a rapid cooling mode, the hysteresis in the rapid cooling mode can be greater than in the normal cooling mode, in order to achieve long compressor switch-on times and correspondingly rapid cooling in the rapid cooling mode.

Further, when the control unit is connected to an outside temperature sensor, it may be configured to set a larger hysteresis at a high outside temperature than at a lower outside temperature. If, at low outside temperature, a low ratio of switch-on times to switch-off times is sufficient to keep the bearing chamber at a setpoint temperature between switch-on threshold and switch-off threshold, then it is also possible to reduce the comparatively small amount of switch-on time on the total operating time of the refrigerator by reducing the hysteresis to several so as to distribute shorter on-time intervals, so that in the course of a single such Einschaltzeitintervall the condenser cools only slightly below the temperature of the storage chamber to be cooled and thus favors an energy-efficient refrigeration. When the ambient temperature is high, on the other hand, if the hysteresis is too low, the compressor on and off times will follow so quickly on each other, that the evaporator does not fully reheat in the course of a turn-off time and thus over several switch-on times, the evaporator temperature is always lower. The advantage associated with a small hysteresis thus no longer occurs here, and the above-mentioned disadvantages of pressure compensation and displacement of refrigerant between the evaporator and condenser predominate, so that it is expedient at high outside temperature to increase the hysteresis and thereby the frequency with which the compressor is switched on and off.

In order to adapt the operation in the above-described manner to different ambient temperatures, it is not absolutely necessary to measure them directly. As an alternative to the consequence, the control unit may also be equipped with means for measuring the duration of switch-on times and switch-off times of the compressor and be set to set a higher hysteresis for a high ratio of switch-on times to switch-off times than for a low ratio for a high ambient temperature.

Furthermore, the fact that an ice layer forming on the evaporator during operation isolates it from the storage chamber to be cooled and thus leads to the fact that, although the evaporator reaches a low temperature, this only benefits to a limited extent the cooling of the storage chamber in that after a defrosting of the evaporator, the control unit initially sets a high hysteresis and later, if it can be assumed that an ice layer has again formed on the evaporator, sets a low hysteresis. The shortening of the switch-on times resulting from the reduced hysteresis can, if the switch-on times do not follow one another too closely, prevent excessive cooling of the evaporator.

If, in order to keep the temperature of the storage chambers in the desired range between switch-on and switch-off, the pauses between the switch-on must be made too short and a strong cooling of the evaporator thus can no longer be prevented, this can be taken as an occasion, in a selbstabtauenden Refrigeration device to trigger a defrosting or, in a non self-defrosting device to alert the user to the need for defrosting.

A simple control can be realized, in particular, if the control unit is set up to choose between a plurality of discrete values of the hysteresis.

In order to achieve a significant effect, at least two of these values should differ by a factor of at least 2.

Typically, the values of the hysteresis adjustable by the control unit are in the interval between 0.25 ° C and 2.0 ° C.

The invention is applicable both to refrigerators with a single storage chamber as well as those with several storage chambers. In a refrigeration device having a plurality of storage chambers, in particular a NoFrost device, a single evaporator can be switchable between a first operating mode in which it cools the first storage chamber and a second operating mode in which it cools the second storage chamber. In both operating modes, the temperature of the evaporator must be slightly lower than the temperature that is to reach each of the storage chamber to be cooled. In the first mode of operation, energy can be saved by keeping the evaporator at a relatively high temperature by choosing a small hysteresis, which may be even higher than that of the second storage chamber. An energy-consuming cooling of the evaporator to a temperature which is deep enough to cool the second storage chamber can then be limited to the second operating mode.

According to another embodiment, two evaporators can be connected in series in a refrigerant circuit of the refrigerator according to the invention, one of which cools one of the storage chambers. Preferably, the second evaporator is connected upstream of the first evaporator, so that when the compressor is turned on, the second evaporator is first charged with liquid refrigerant. If, as mentioned above, a lower hysteresis is set in such a refrigerator at low ambient temperature than at high ambient temperature, then the consequent shortening of the compressor on-time results in the proportion of liquid refrigerant being available to the second evaporator is, in proportion larger than with a large hysteresis and correspondingly long compressor switch-on time. Thus, an undesirable heating of the second storage chamber can be prevented at low ambient temperature.

• a) Einschalten des Verdichters, wenn die Temperatur der ersten Lagerkammer des Kältegeräts über eine Einschaltschwelle steigt,
• b) Ausschalten des Verdichters, wenn die Temperatur der ersten Lagerkammer unter eine Ausschaltschwelle fällt, und
• c) Festlegen einer Hysterese zwischen der Einschalt- und der Ausschaltschwelle anhand wenigstens eines der folgenden Kriterien: – Außentemperatur, – Verhältnis von Einschaltzeiten zu Ausschaltzeiten des Verdichters, – seit dem letzten Abtauen des Verdampfers verstrichene Zeit.

The invention also provides a method for operating a refrigeration appliance, in particular a domestic refrigeration appliance as described above, with the steps

• a) switching on the compressor when the temperature of the first storage chamber of the refrigerator rises above a switch-on threshold,
• b) switching off the compressor when the temperature of the first storage chamber falls below a switch-off threshold, and
• c) Setting a hysteresis between the switch-on and switch-off threshold based on at least one of the following criteria: - ambient temperature, - ratio of switch-on times to switch-off times of the compressor, - time elapsed since the evaporator was last defrosted.

Further features and advantages of the invention will become apparent from the following description of embodiments with reference to the accompanying figures. Show it:

1 a block diagram of a refrigerator according to a first embodiment of the invention;

2 a flowchart of a method of operation of the refrigeration device off 1 ;

3 a block diagram of a refrigerator according to a second embodiment of the invention;

4 a schematic section through a refrigerator according to a third embodiment of the invention; and

5 a flowchart of another operating method.

1 schematically shows a household refrigerator with a heat-insulating housing 1 , a storage chamber 2 surrounds. A refrigerant circuit for cooling the storage chamber 2 includes a compressor 3 , a liquefier 4 connected to a pressure port of the compressor 3 connected, one of the condenser 4 outgoing throttle pipe 5 as well as an evaporator 6 into the throttle tube 5 at an injection point 7 opens and the via a suction line 8th with a suction port of the compressor 3 connected is. A control unit 9 for switching the compressor on and off 3 is with a temperature sensor 10 connected to the temperature of the storage chamber 2 recorded and for the purpose eg between a the storage chamber 2 surrounding inner container and a mounted around the inner container insulation layer of the housing 1 can be arranged. A second temperature sensor 11 is outside of the housing 1 attached to monitor the temperature in the environment of the refrigerator.

A temperature of the storage chamber 2 that should not be significantly exceeded during operation of the refrigerator is at a user interface of the control unit 9 adjustable. In a conventional manner, such a user interface by a knob in the storage chamber 2 be formed.

2 FIG. 12 shows a flowchart of an operating procedure performed by the control unit 9 of in 1 shown refrigeration device is running. It is believed that at the beginning of the process of 2 the compressor 3 is off. In step S1, the control unit asks 9 that of the temperature sensor 10 measured temperature Ti of the storage chamber 2 and compares it with a switch-on threshold Tein, which can be the same as the temperature set on the user interface.

As long as Ti remains below the switch-on threshold Tein, the process returns to the output again, so that step S1 is repeated periodically and the temperature Ti is checked. Once Tein is exceeded, in step S2, the compressor 3 switched to the storage chamber 2 to cool again.

Subsequently, in step S3, the outside temperature Ta from the temperature sensor 11 queried. If the refrigerator is in a cool environment with Ta ≦ 20 ° C, a hysteresis parameter H is set to 0.5 ° C in step S4.

In a warmer environment, at Ta> 20 ° C, the process branches to step S5 to compare Ta with a second threshold, here 35 ° C. If Ta is below this threshold, the hysteresis parameter H is set to 1.0 ° C (S6), otherwise, in a hot environment above 35 ° C, to 1.25 ° C (S7).

Subsequently, a switch-off threshold Tout is set in step S8, which is lower by the hysteresis parameter H than the switch-on threshold Tein. The compressor 3 remains in operation until it is determined in step S9 that the temperature Ti of the storage chamber 2 has fallen below the turn-off threshold Toff (S10). The flow chart of 2 that is, as long as this condition is not met, only step S9 is repeated in an endless loop; Alternatively, it would be conceivable to jump back to step S3 in this case in order, if during the switch-on of the compressor 3 the ambient temperature Ta has changed to take account of this fact by adjusting the hysteresis H.

The lower the ambient temperature Ta, the smaller the temperature gradient between the environment and the storage chamber 2 , and the longer it takes with a given hysteresis H, until the compressor is switched off 3 the storage chamber has heated from Taus to Tein. By selecting a small hysteresis H at low ambient temperature Ta in step S4, both the turn-off time and the turn-on time, ie, the time from step S2 to step S10, are shortened. At the beginning of the switch-on time corresponds to the temperature of the evaporator 6 essentially the temperature Ti of the storage chamber 2 ; during the switch-on time it decreases. The shorter the turn-on time, the higher the average temperature of the evaporator 6 during the turn-on time, and hence the better the refrigeration efficiency.

A variant to consequence, the temperature sensor 11 in 1 also omitted; instead, the control unit is 9 set up, in each case the switch-on time of the compressor 3 , from step S2 to S10, and to measure the switch-off time, from step S10 to step S2, and to calculate therefrom a ratio - possibly averaged over several switch-on and switch-off times. The ratio obtained in this way has a clear relationship to the ambient temperature, so that the ratio is converted into the ambient temperature Ta either on the basis of an empirically determined function and based on this ambient temperature, the method of 2 or the comparison of the ambient temperature with thresholds in steps S3 and S5 is replaced by a comparison of the calculated ratio of switch-on to switch-off times with correspondingly defined threshold values.

In a completely equivalent manner, the switch-on time or the switch-off time can also be compared with the total operating time of the refrigerating appliance, and this ratio can be compared with suitably defined thresholds in order to switch the compressor on and off 3 to decide.

3 shows in one too 1 analog block diagram of a refrigerator according to a second embodiment of the invention. In the case 1 are storage chambers 2 and 12 recessed, and each storage chamber is each an evaporator 6 respectively. 13 assigned. The throttle tube 5 opens here into the evaporator 13 one, and the evaporator 6 is the evaporator 13 connected in series. The temperature of the storage chamber 12 is lower than that of the storage chamber 2 Typically, the former may be a freezer and the latter a standard refrigerator. A temperature sensor 10 is like in the case of 1 at the storage room 2 arranged, and for detecting the ambient temperature Ta, a temperature sensor 11 be provided outside the housing, or it may, as explained above, means for measuring the on and off times be provided.

The working method of the control unit 9 is the refrigeration device of 3 with the in 2 shown identical. In addition to the effects already explained above, the method has the refrigeration of the 3 the effect that when a low value of hysteresis H is set, liquid refrigerant initially only the evaporator 13 achieved so that it cools down quickly, the evaporator 6 but only with a certain delay. The greater this delay in relation to the turn-on time, the greater is the proportion of the total cooling power that is on the storage chamber 12 eliminated. By setting a small hysteresis H here at low ambient temperature Ta, it is thus possible to counteract the known problem that, in a single-circuit refrigeration appliance controlled by a temperature sensor in the warmer storage compartment, the colder compartment in a cool environment tends to overheat become.

The user interface of this refrigeration device may, according to a further development, have an operating element that can be actuated by a user in order to activate a rapid-cooling operating mode. In this quick cooling mode, the control unit resets 9 Tein down and H to the highest available value of here eg 1.25 ° C to reach a low evaporator temperature.

4 shows a schematic section through a NoFrost refrigeration device in the housing 1 a warmer storage room 2 , a colder storage room 12 and an evaporator chamber 14 are omitted. The evaporator chamber 14 contains in a conventional manner an evaporator 15 , a fan 16 and an air guide 17 which is reversible to one from the fan 16 driven air flow optionally through the storage chamber 2 or the storage room 12 to steer. Both storage chambers 2 . 12 is each a temperature sensor 10 respectively. 18 assigned, and the control unit 9 is programmed to the (in 4 not shown) to turn compressor when in one of the chambers 2 . 12 the temperature exceeds the switch-on threshold of the relevant chamber, and turn it off again at the latest when the switch-off threshold is reached again in both chambers. The hysteresis H between on and off thresholds is for the colder chamber 12 higher than for the warmer chamber 2 , with the result that the turn-on times when cooling the colder chamber 12 are significantly longer than when cooling the warmer chamber 2 , Due to the long switch-on times the evaporator reaches 15 when cooling the colder chamber 12 relatively low temperatures necessary for cooling this chamber 12 also necessary. When cooling the chamber 2 the switch-on time for such a deep cooling is not sufficient; the temperature of the evaporator 15 is therefore when the chamber 2 is cooled, on average higher than when cooling the chamber 12 what the energy efficiency when cooling the chamber 2 improved.

If cooling demand in both chambers 2 . 12 occurs at the same time, he should first in the chamber 2 be satisfied, and once in this chamber 2 the switch-off threshold Toff is reached, the control unit provides the air guiding element 17 on cold air supply to the chamber 12 and keeps the compressor running. So it is right at the beginning of a cooling phase of the chamber 12 a reasonably low evaporator temperature available, and this decreases while the chamber 12 is cooled, even further off.

5 shows a flowchart of a working method of the control unit 9 that is used both in the refrigeration device of the 4 as well as in a NoFrost refrigerator with a single storage chamber executable. In the first step S11 of the process, the evaporator 15 defrosted, a timer t is set to 0, and the hysteresis H is set to a high value of, for example, 1 ° C.

In step S12 is repeated cyclically until the temperature Ti in a (or one) storage chamber of the refrigerator exceeds the switch-on threshold Tein. As soon as this happens, the compressor is switched on (S13) and the switch-off threshold Toff is set to Tein-H (S14). The compressor will remain in operation until the storage chamber has cooled down to Dew (S15). As soon as this has happened, the time measured by the timer, which has elapsed since the defrost, is compared with a waiting time tmin (S16). If the waiting time has not elapsed yet, then the process returns to step S12.

If, on the other hand, the waiting time tmin has elapsed in step S16, then in S17 a new, smaller value of the hysteresis H, here for example 0.5 ° C., is set. In this way, the fact is taken into account that in all likelihood at the end of the waiting time again ice on the evaporator 15 has formed, which delays the heat exchange with the storage chamber. That the evaporator 15 Cooling rapidly to a low temperature under these conditions, in which the efficiency of the cooling generation is unsatisfactory, is prevented by the shortening of the compressor switch-on times associated with the low hysteresis H.

In step S18, it is checked whether a second waiting time tmax has elapsed since the last defrost, which is longer than tmin. If not, then the method returns to S12, if so, then to step S11 to the evaporator 15 defrost again.

Of course, in this method, instead of just once in step S17, the hysteresis H could also be reduced in several successive steps in order to prevent the continuous increase in the thickness of the ice layer on the evaporator 15 To bear the bill.

LIST OF REFERENCE NUMBERS

1

 casing

2

 storage chamber

3

 compressor

4

 condenser

5

 choke tube

6

 Evaporator

7

 Injection site

8th

 suction

9

 control unit

10

 temperature sensor

11

 temperature sensor

12

 storage chamber

13

 Evaporator

14

 evaporator chamber

15

 Evaporator

16

 fan

17

 air guide

Claims (10)

Refrigerating appliance, in particular household refrigerating appliance, with at least one first storage chamber ( 2 ), a temperature sensor ( 10 ) for detecting the temperature (Ti) of the first storage chamber ( 2 ), a first evaporator ( 6 . 15 ) for cooling the first storage chamber ( 2 ), a compressor ( 3 ) and a control unit ( 9 ) for switching on the compressor ( 3 ), when the temperature (Ti) of the first storage chamber ( 2 ) rises above a switch-on threshold (Tein), and to switch off the compressor ( 3 ), when the temperature (Ti) of the first storage chamber ( 2 ) falls below a switch-off threshold (Taus), characterized in that a hysteresis (H) between the switch-on threshold (Tein) and the switch-off threshold (Toff) is variable. Refrigerating appliance according to claim 1, characterized in that the control unit ( 9 ) is switchable between a normal cooling mode and a rapid cooling mode and that the hysteresis (H) in the rapid cooling mode is greater than in the normal cooling mode. Refrigerating appliance according to claim 1 or 2, characterized in that the control unit ( 9 ) with an outside temperature sensor ( 11 ) and is set to set a higher hysteresis (H) at a high outside temperature (Ta) than at a lower outside temperature (Ta). Refrigerating appliance according to one of the preceding claims, characterized in that the control unit ( 9 ) Means for measuring the duration of switch-on times and switch-off times of the compressor ( 3 ) and is arranged to set a larger hysteresis (H) with a high ratio of switch-on times to switch-off times than with a low ratio. Refrigerating appliance according to one of the preceding claims, characterized in that the control unit ( 9 ) after defrosting the evaporator ( 15 ) first set a large hysteresis (H) and later a low hysteresis. Refrigerating appliance according to one of the preceding claims, characterized in that the control unit ( 9 ) is arranged to choose between a plurality of discrete values of hysteresis (H). Refrigerating appliance according to one of the preceding claims, characterized in that the control unit ( 9 ) adjustable values of the hysteresis (H) in the interval between 0.25 ° C and 2.0 ° C. Refrigerating appliance according to one of claims 1 to 7, characterized in that it has a second storage chamber ( 12 ) whose temperature is lower than that of the first storage chamber ( 2 ), wherein the evaporator ( 15 ) between a first operating mode for cooling the first storage chamber ( 2 ) and a second operating mode for cooling the second storage chamber ( 12 ) is switchable and the hysteresis (H) in the second operating mode is greater than in the first operating mode. Refrigerating appliance according to one of claims 1 to 7, characterized in that it has a second storage chamber ( 12 ) whose temperature is lower than that of the first storage chamber ( 2 ), and that a second evaporator ( 13 ) for cooling the second storage chamber ( 12 ) the first evaporator ( 3 ) is connected upstream in a refrigerant circuit. Method for operating a refrigerating appliance, in particular household refrigerating appliance, with at least one first storage chamber ( 2 ), a temperature sensor ( 10 ) for detecting the temperature (Ti) of the first storage chamber ( 2 ), a first evaporator ( 6 . 15 ) for cooling the first storage chamber ( 2 ) and a compressor ( 3 ), with the steps a) switching on (S2) of the compressor ( 3 ), when the temperature (Ti) of the first storage chamber rises above a switch-on threshold (Tein) (S1), b) switching off (S10) the compressor ( 3 ), when the temperature (Ti) of the first storage chamber ( 2 ) falls below a switch-off threshold (Taus), and c) setting a hysteresis (H) between the switch-on and switch-off thresholds based on at least one of the following criteria: - outside temperature (Ta), - ratio of switch-on times to switch-off times of the compressor ( 3 ), - since the last defrost of the evaporator ( 15 ) elapsed time (t).

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