METHOD FOR OPERATING A ROTATIONAL-SPEED-VARIABLE REFRIGERANT COMPRESSOR

Abstract

The invention relates to a method for operating a rotational-speed-variable refrigerant compressor (2) for cooling a cooling volume (4) of a refrigeration system (1), which refrigeration system does not have its own control unit, wherein the refrigeration system (1) comprises at least one thermostat (3) for directly or indirectly monitoring a temperature state of the cooling volume (4) and wherein the rotational-speed behavior of the refrigerant compressor (2) during a cooling cycle is controlled by means of a specification rotational-speed control stored in an electronic control device (6) of the refrigerant compressor (2). According to the invention, in order to enable adjustment of the rotational-speed behavior in reaction to a preceding special operating state and to enable energy-optimized cooling of the cooling volume (4) that is as fast as possible, at least one comparison parameter is stored in the electronic control device (6) of the refrigerant compressor (2) and exceedance or undershooting of the comparison parameter by a current measured parameter value is monitored, a special cooling cycle different from the specification rotational-speed control is triggered if the current measured parameter value exceeds or undershoots the comparison parameter, possibly, a current cooling cycle controlled by means of the specification rotational-speed control is interrupted by the special cooling cycle.

Claims

1. A method for operation of a rotary speed-variable refrigerant compressor for cooling a cooled volume of a refrigeration system, wherein it comprises a thermostat for direct or indirect monitoring of a temperature state of the cooled volume and where the refrigerant compressor is operated cyclically, and a cooling cycle (C.sub.K) of the refrigerant compressor begins when the refrigerant compressor is set into an ON state by a switching signal triggered by a thermostat, and the cooling cycle (C.sub.K) ends when the refrigerant compressor is set to an OFF state by an additional signal triggered by the thermostat, where an operating cycle (C) comprises, besides the cooling cycle (C.sub.K), a rest cycle (C.sub.R) following the cooling cycle (C.sub.K), and where the rotary speed behavior of the refrigerator compressor is controlled during a cooling cycle (C.sub.K) by means of a preset rotary speed control stored in an electronic control device of the refrigerant compressor, wherein at least one comparison parameter (P.sub.V) is stored in the electronic control device of the refrigerant compressor and an exceeding or falling short of the comparison parameter (P.sub.V) by a currently measured parameter value (P.sub.a) is monitored, a special cooling cycle (C.sub.D) that is different from the preset rotary speed control is initiated if the current measured parameter value (P.sub.a) exceeds or falls short of the comparison parameter (P.sub.V), optionally, a current cooling cycle (C.sub.K) that is controlled by the preset rotary speed control is interrupted by the special cooling cycle (C.sub.D).

2. The method as in claim 1, wherein the at least one monitored comparison parameter (P.sub.V) or one of the monitored comparison parameters (P.sub.V) is a load (L) of the refrigerant compressor in a starting phase of a cooling cycle (C.sub.K).

3. The method as in claim 2, wherein the load (L) is monitored as the average load (L.sub.m), averaged over the duration of the starting phase.

4. The method as in claim 1, wherein the at least one monitored comparison parameter (P.sub.V) or one of the monitored comparison parameters (P.sub.V) is a duration of the rest cycle (C.sub.R).

5. The method as in claim 1, wherein an additional temperature (T.sub.w) that is independent of the temperature of the cooled volume is measured, the currently measured parameter value (P.sub.a) or one of the currently measured parameter values (P.sub.a) is the additional temperature (T.sub.w), the at least one monitored comparison parameter (P.sub.V) or one of the monitored comparison parameters (P.sub.V) is a comparison temperature (T.sub.V).

6. The method as in claim 1, wherein the electronic control device of the refrigerant compressor monitors to see if a power supply of the electronic control device has been interrupted, and the special cooling cycle (C.sub.D) is initiated if both an exceeding or falling short of the comparison parameter (P.sub.V) by the currently measured parameter value (P.sub.a) and a preceding interruption of the power supply are detected.

7. The method as in claim 1, wherein the at least one measured current parameter value (P.sub.a) is stored in the electronic control device of the refrigerant compressor over at least two operating cycles (C) as stored parameter value (P.sub.S).

8. The method as in claim 7, wherein an extreme value (P.sub.E) of the stored parameter values (P.sub.S) is selected in the electronic control device of the refrigerant compressor and the comparison parameter (P.sub.V) is determined in dependence on the extreme value (P.sub.E).

9. The method as in claim 7, wherein an average value (P.sub.M) of the stored parameter values (P.sub.S) is calculated in the electronic control device of the refrigerant compressor and the comparison parameter (P.sub.V) is determined in dependence on the average value (P.sub.M).

10. The method as in claim 8, wherein the comparison parameter (P.sub.V) is determined by multiplying the extreme value (P.sub.E) or the average value (P.sub.M) by a deviation factor, wherein the deviation factor is at least 1.25.

11. The method as in claim 1, wherein a starting rotary speed (v.sub.s) of the refrigerant compressor is established for the cooling cycle (C.sub.K) following the special cooling cycle (C.sub.C) [sic; C.sub.D] on the basis of a value stored in the electronic control device.

12. The method as in claim 1, wherein the refrigerant compressor is operated during the special cooling cycle (C.sub.D) so that a higher average cooling capacity is sent to the cooled volume than in the case of a comparable cooling cycle controlled in accordance with the preset rotary speed control (C.sub.K).

13. The method as in claim 1, wherein the refrigerant compressor is operated during the special cooling cycle (C.sub.D) so that a defined rotary speed (v.sub.c) is not exceeded before the end of the special cooling cycle (C.sub.D), wherein the defined rotary speed (v.sub.c) is at least 75%, of a maximum rotary speed of the refrigerant compressor.

14. The method as in claim 1, wherein the refrigerant compressor is accelerated at the beginning of the special cooling cycle (C.sub.D) to a predefined rotary speed (v.sub.c), wherein the at least one defined rotary speed (v.sub.c) is at least 70%, of a maximum rotary speed of the refrigerant compressor.

15. An electronic control device for control of the cyclic operation of a rotary speed-variable refrigerant compressor, where the electronic control device is configured to switch the refrigerant compressor on due to a switching signal triggered by a thermostat for direct or indirect monitoring of a temperature state of a cooled volume of a refrigeration system in order to begin a cooling cycle (C.sub.K) and to end a rest cycle (C.sub.R), and to switch the refrigerant compressor off again on the basis of an additional switching signal triggered by the thermostat in order to end the cooling cycle (C.sub.K) and to begin a rest cycle (C.sub.R), and to control the rotary speed behavior of the refrigerant compressor during a cooling cycle (C.sub.K) by means of a preset rotary speed control stored in the electronic control device, wherein at least one comparison parameter (P.sub.V) is stored in the electronic control device and the electronic control device is configured to detect an exceeding or falling short of the comparison parameter (P.sub.V) by a current measured parameter value (P.sub.a), to initiate a special cooling cycle (C.sub.D) that is different from the preset rotary speed control if the current measured parameter value (P.sub.a) exceeds or falls short of the comparison parameter (P.sub.V), optionally to interrupt a current cooling cycle ( ) [sic; (C.sub.K)] controlled by the preset rotary speed control in order to start the special cooling cycle ( ) [sic; (C.sub.D)].

16. The electronic control device as in claim 15, wherein the electronic control device is configured to measure a load of the refrigerant compressor as the current through the refrigerant compressor and that the stored comparison parameter (P.sub.v) and the currently measured parameter value (P.sub.a) are loads.

17. The electronic control device as in claim 15, wherein the electronic control device is configured to determine a duration of the rest cycle (C.sub.R) and that the stored comparison parameter (P.sub.v) and the currently measured parameter value (P.sub.a) are the duration of a rest cycle (C.sub.R).

18. The electronic control device as in claim 15, wherein the electronic control device is connected to a temperature measuring device for measurement of an additional temperature (T.sub.w) that is independent of the temperature of the cooled volume, and that the stored comparison parameter (P.sub.v) is a comparison temperature (T.sub.v) and the currently measured parameter value (P.sub.a) is the additional temperature (T.sub.w).

19. The electronic control device as in claim 18, wherein the temperature measuring device is a component of the electronic control device of the refrigerant compressor or that the temperature measuring device is disposed on a housing of the refrigerant compressor.

20. The electronic control device as in claim 15, wherein the electronic control device is configured to detect an interruption of the power supply and to initiate a special cooling cycle (C.sub.D) if both an exceeding or falling short of the comparison parameter (P.sub.V) by the currently measured parameter value (P.sub.a) and a preceding interruption of the power supply were detected.

21. A module comprising a rotary speed-variable refrigerant compressor with an electric drive unit and a piston-cylinder unit that can be driven by the electric drive unit for compression of refrigerant; an electronic control device as in claim 15 for control of the cyclic operation of the rotary speed-variable refrigerant compressor.

22. The method as in claim 3, wherein the duration of the starting phase is between 10 s and 90 s.

23. The method as in claim 22, wherein the duration of the starting phase is between 40 s and 70 s.

24. The method as in claim 8, wherein the comparison parameter (P.sub.V) is determined in dependence on the extreme value (P.sub.E), which corresponds to a maximum value of the extreme value (P.sub.E).

25. The method as in claim 9, wherein the comparison parameter (P.sub.V) is determined in dependence on the average value (P.sub.M), which corresponds to the average value (P.sub.M).

26. The method as in claim 10, wherein the deviation factor is at least 1.50.

27. The method as in claim 26, wherein the deviation factor is 1.75.

28. The method as in claim 26, wherein the deviation factor is 2.0.

29. The method as in claim 13, wherein the defined rotary speed (v.sub.c) is at least 85% of a maximum rotary speed of the refrigerant compressor.

30. The method as in claim 29, wherein the defined rotary speed (v.sub.c) is at least 90% of a maximum rotary speed of the refrigerant compressor.

31. The method as in claim 30, wherein the defined rotary speed (v.sub.c) is between 95% and 100% of a maximum rotary speed of the refrigerant compressor.

32. The method as in claim 14, wherein the at least one defined rotary speed (v.sub.c) is more than at least 80% of a maximum rotary speed of the refrigerant compressor.

33. The method as in claim 32, wherein the at least one defined rotary speed (v.sub.c) is at least 90% of a maximum rotary speed of the refrigerant compressor.

34. The method as in claim 33, wherein the at least one defined rotary speed (v.sub.c) is between 95% and 100% of a maximum rotary speed of the refrigerant compressor.

35. A module comprising a rotary speed-variable refrigerant compressor with an electric drive unit and a piston-cylinder unit that can be driven by the electric drive unit for compression of refrigerant; an electronic control device for control of the cyclic operation of the rotary speed-variable refrigerant compressor as in the method of claim 1.

Description

BRIEF DESCRIPTION OF THE FIGURES

[0091] The invention will now be explained in more detail by means of embodiment examples. The drawings are merely examples and are intended to present the ideas of the invention, but not to limit it in any way or to reproduce it conclusively.

[0092] Here:

[0093] FIG. 1 shows a schematic representation of the back of a refrigeration system;

[0094] FIG. 2 shows a schematic representation of a refrigerant compressor with another embodiment of the electronic control device;

[0095] FIG. 3 shows a schematic representation of the rotary speed behavior of three different cycles of the refrigerant compressor in a preset rotary speed control;

[0096] FIG. 4 shows a schematic representation of the rotary speed behavior after a defrost operation according to the preset rotary speed control per the prior art;

[0097] FIG. 5 shows a schematic representation of the rotary speed behavior after a defrost operation according a first embodiment of the method according to the invention;

[0098] FIG. 6 shows a schematic representation of the rotary speed behavior after a defrost operation according to a second embodiment of the method according to the invention;

[0099] FIG. 7 shows a schematic representation of the rotary speed behavior after a power outage according to a third embodiment of the method according to the invention.

WAYS OF IMPLEMENTING THE INVENTION

[0100] FIG. 1 shows a simple refrigeration system 1 with a variable-speed refrigerant compressor 2, a refrigerant line 5, and an evaporator 5a. Refrigerant compressor 2, refrigerant line 5, and evaporator 5a form a closed refrigerant system in which refrigerant circulates during the operation, thus during a cooling cycle C.sub.K of the refrigerant compressor 2. The refrigeration system 1 has a cooled volume 4, wherein heat can be removed or cooling output delivered by the evaporator 5a by evaporating the refrigerant in evaporator 5a.

[0101] The individual components of the refrigerant compressor 2, thus at least one piston-cylinder unit in which the refrigerant is cyclically compressed and an electric drive unit, via which the piston-cylinder unit can be driven, are disposed within a housing 8 of the refrigerant compressor 2. The variable-speed refrigerant compressor 2 additionally has an electronic control device 6 for control of the rotary speed behavior of the refrigerant compressor 2, which is connected to the electric drive unit and controls it. In order to enable of the cooling of the cooled volume 4 to be as energy optimized as possible, the electronic control device 6 of the variable-speed refrigerant compressor 2 operates during the cooling cycle C.sub.K according to a programmed setting, which controls the rotary speed behavior C.sub.K of the refrigerant compressor 2 during a cooling cycle C.sub.K. This preset rotary speed control enables the variable-speed refrigerant compressor 2 to be operated in the simple refrigeration system 1 and at the same time ensures operation is as energy optimized as possible. The programmed setting in this case is already implemented in the programming of the electronic control device 6 of the refrigerant compressor and represents, so to say, a standardized as-delivered state, which enables operation to be as energy optimized as possible in a large number of standard conditions of use. Usually, the variable-speed refrigerant compressor 2 and the electronic control device 6 are assembled as a module by a refrigerant compressor manufacturer and sold as a unit to the manufacturer of refrigeration systems.

[0102] The method according to the invention or the electronic control device of the refrigerant compressor according to the invention for adjusting the operation of the refrigerant compressor to special operating states, which require a high cooling output of the refrigerant compressor 2, is described in detail below.

[0103] The refrigeration system 1 does not itself have an autonomous control unit that can make available switching signals, characteristic parameters, and measured parameters available to the control device 6 of the refrigerant compressor 2 or that transmits a control signal that contains a rotary speed setting. The only switching signal that the simple refrigeration system 1 transmits to the control device 6 of the refrigerant compressor 2 derives from a thermostat 3 as a function of the temperature level of the cooled volume 4. For this, the thermostat 3 as a rule has a temperature sensor, for example a bimetallic strip or a vapor pressure-based measurement element or an NTC (negative temperature coefficient) element, which is disposed in the cooled volume 4 in order to measure the temperature of the cooled volume 4 directly, or is disposed on the evaporator 5a in order to determine the temperature of the cooled volume 4 indirectly. Preferably, the thermostat 3 is designed as a vapor pressure-based bellows thermostat. The thermostat 3 is designed to trigger a switching signal, which is transmitted to the control device 6 of the refrigerant compressor 2, or to transmit a switching signal to the control device 6, which switching signal sets the refrigerant compressor 2 to an ON state, in which the drive unit is activated and refrigerant is compressed in the piston-cylinder unit. The thermostat 3 is designed to trigger an additional switching signal, which is transmitted to the control device 6 in order to transmit an additional switching signal to the control device 6, which additional switching signal sets the refrigerant compressor 2 to an OFF state in which the piston-cylinder unit is not subject to any drive torque.

[0104] According to one aspect of the invention, a temperature measuring unit 7 is provided, via which an additional temperature T.sub.w that is independent of the temperature of the cooled volume 4 is measured. In this embodiment, the temperature measuring unit 7 is made as a component of the control device 6, for example as an onboard sensor on a circuit board of the control device 6.

[0105] FIG. 2 shows a second embodiment of the invention, in which the temperature measuring unit 7 is mounted on the housing 8 of the refrigerant compressor 2. The housing 8 of the refrigerant compressor 2 can be, for example, a hermetically sealable housing 8, which comprises a lower housing section 8a and an upper housing section 8b. In this embodiment example, the temperature measuring unit 7 is mounted on an outer surface of the upper housing part 8b. The reference numbers 7 and 7 designate alternative attachment positions, shown as dashed lines, on an outer side of the housing lower part 8a, whereas the reference number 7 designates an alternative attachment position, represented as a dashed line, on a support leg of the refrigerant compressor 2.

Functioning of the Invention

[0106] A method for operating the variable-speed refrigerant compressor 2 in a simple refrigeration system 1, as is already known from the prior art, is described below by means of FIG. 3. In particular, the control of the rotary speed behavior of the variable-speed refrigerant compressor 2, the so-called preset rotary speed control, in which the rotary speed behavior of the refrigerant compressor 2 is controlled on the basis of at least one predefined parameter K.sub.v, which is stored in the electronic control device 6 of the refrigerant compressor 2, during a cooling cycle C.sub.K, and the at least one parameter value K.sub.v is monitored with respect to its being exceeded and/or fallen short of by a current parameter K.sub.a of a current cooling cycle C.sub.Ka.

[0107] In this embodiment example, the at least one predefined parameter K.sub.v is the duration of a cooling cycle C.sub.K. Here, the current running time and the actual duration of the cooling cycle C.sub.K are monitored by the electronic control device 6.

[0108] FIG. 3 shows, as an example, three operating cycles C.sub.1, C.sub.2, C.sub.3, which represent different rotary speed behaviors of the variable-speed refrigerant compressor 2 that can be set during its operation. An operating cycle C is composed in each case of a rest cycle C.sub.R and a cooling cycle C.sub.K, wherein the refrigerant compressor 2 is in operation during a cooling cycle C.sub.K and force-circulates refrigerant through the refrigeration system to cool the cooled volume 4. On the other hand, in the rest cycle C.sub.R, the refrigerant compressor 2 is not driven and essentially no cooling of the cooled volume 4 takes place.

[0109] The first cooling cycle C.sub.K1 is begun at time t.sub.1 by the switching signal triggered by the thermostat 3, wherein the refrigerant compressor 2 is set to an ON state by the electronic control device 6. The thermostat 3 triggers the switching signal when a deviation of the temperature level of the cooled volume 4 from a preset temperature level is detected, which indicates a cooling demand in the cooled volume 4, so that cooling output can be sent to the cooled volume 4 by the refrigerant compressor 2. In this case, an exceeding of the preset temperature level is detected by thermostat 3 or by the temperature feeler of thermostat 3 at time t.sub.1. The temperature in the cooled volume 4 is thus too high. As soon as the variable-speed refrigerant compressor 2 is set to the ON state, it is operated at a starting rotary speed v.sub.1. At time t.sub.2, which corresponds to the predefined duration of the cooling cycle C.sub.K1, the preset temperature level in the cooled volume 4 has not yet been reached, and the thermostat 3 accordingly has not triggered a switching signal to set the refrigerant compressor 2 to the OFF state.

[0110] Thus, a further cooling requirement exists in the cooled volume 4 at time t.sub.2. Since the actual cooling requirement of the cooled volume 4 is not known to the electronic control device 6, the rotary speed v is increased by a preset value, for example 10%, 20%, 30%, or 50%, of the current rotary speed v.sub.1, to a first increased rotary speed v.sub.2. This ensures that the cold demand in the cooled volume 4 can be recovered faster, or if the cold demand is generally very high, or the cooling cycle C.sub.K can be quickly ended.

[0111] At time t.sub.3, which corresponds to a limit value of a data record stored in the predefined running time K.sub.v, the cold demand of the cooled volume 4 has still not yet been satisfied, so that in this example, an additional increase of the rotary speed v to a second increased rotary speed v.sub.3 takes place for the reasons given above.

[0112] At time t.sub.4, the electronic control device 6 receives the additional switching signal triggered by the thermostat 3, which signals that the cold demand in the cooled volume 4 has been satisfied and the temperature in the cooled volume 4 lies within the predefined temperature level needed for cooling. On the basis of the additional switching signal, the electronic control device 6 sets the refrigerant compressor 2 to the OFF state, so that the second rest cycle C.sub.R2 is initiated. The time that has passed between times t.sub.1 and t.sub.4 corresponds to the actual duration K.sub.1 of the first cooling cycle C.sub.K1. Since the actual duration K.sub.1 is greater than the predefined duration K.sub.v, it can be provided either that the next cooling cycle C.sub.K2 is begun without change in accordance with the preset rotary speed control, with the risk that it must be readjusted as in C.sub.K1, or it can be provided that the electronic control device 6 starts from an increased cold demand in the next cooling cycle C.sub.K2. The latter can be the case in particular when cooling cycles C.sub.K whose duration was longer than the predefined running time K.sub.v already exist before the cooling cycle C.sub.K1.

[0113] In order to take care of the expected higher cold demand of the cooled volume 4 and to be able to provide it within the predefined duration K.sub.v of the next cooling cycle C.sub.K2, the next cooling cycle C.sub.K2, which again is triggered by the switching signal, will be operated at an increased starting rotary speed v.sub.4. The increased starting rotary speed v.sub.4 can, for example, correspond to the last rotary speed v of the preceding cooling cycle C.sub.K1 or can be calculated as the average value of the rotary speeds v.sub.1, v.sub.2, v.sub.3 of the preceding cooling cycle C.sub.K1.

[0114] In the second cooling cycle C.sub.K2, the electronic control device 6 receives an additional switching signal triggered by the thermostat 3 to switch off the refrigerant compressor 2 at time t.sub.6. The actual duration K.sub.2 of the second cooling cycle C.sub.K2 is, however, less than the predefined duration K.sub.v, so that the actual cooling demand of the cooled volume 4 has already been satisfied before the predefined duration K.sub.v is reached at time t.sub.7. From this, the electronic control device 6 can infer that a lower cooling demand is necessary in the next cooling cycle C.sub.K3.

[0115] In order to take care of the expected lower cooling demand of the cooled volume 4 and to reach it within the predefined duration K.sub.v of the next cooling cycle C.sub.K3, the third cooling cycle C.sub.K3 is started with a rotary speed v that is lower than the rotary speed v.sub.4 of the preceding cooling cycle C.sub.K2, the lower rotary speed v in this embodiment example corresponding to the starting rotary speed v.sub.1. In the third cooling cycle C.sub.K3, the predefined duration K.sub.v corresponds with the duration K.sub.3 of the third cooling cycle C.sub.3, so that the cooling demand of the cooled volume 4 is reached with the rotary speed v.sub.1 within the predefined duration K.sub.v. In the third cooling cycle C.sub.K3, an especially energy-conserving operation of the refrigerant compressor 2 is achieved.

[0116] The above described control of the rotary speed behavior of the refrigerant compressor 2 in the electronic control device 6 corresponds to the preset rotary speed control, which is configured to enable operation that is as energy optimized as possible over the entire operating time of the refrigerant compressor 2.

[0117] In the case of simple refrigeration systems 1 with automatic defrosting, the refrigeration system 1 carries out a defrost operation at preset, as a rule periodic, intervals. During the defrost operation the evaporator 5a is heated, for example via heating elements provided for this, in order to remove layers of frost or ice that have built up in the cooled volume 4 in the region of the evaporator 5a. In this case, at least the refrigerant in the evaporator 5a also becomes heated. The defrost operation is initiated in a rest cycle C.sub.R, so that the refrigerant compressor 2 is in the OFF state during the defrost operation. During the defrost operation, a switching signal that sets the refrigerant compressor 2 to the ON state is not triggered by the thermostat 3. Only after the end of the defrost operation does the thermostat 3 trigger the switching signal, so that the refrigerant compressor 2 is set to the ON state by the electronic control device 6 of the refrigerant compressor 2.

[0118] The disadvantages of the prior art are explained by means of the rotary speed behavior depicted in FIG. 4. The first two cooling cycles C.sub.K1, C.sub.K2 run according to the preset rotary speed control, as described above. For the sake of simplicity, the two cooling cycles C.sub.K1, C.sub.K2 are shown as operating cycles in which the predefined duration K.sub.v corresponds to the actual duration K.sub.1, K.sub.2, and the refrigerant compressor 2 is operated at the rotary speed v.sub.1. A defrost operation, indicated as DEFROST in the figure, is initiated during the third rest cycle C.sub.R3, which follows the second cooling cycle C.sub.K2.

[0119] After the end of the defrost operation, the thermostat 3 triggers the switching signal and the refrigerant compressor 2 is set to the ON state. Since the electronic control device 6 of the refrigerant compressor 2 does not receive a control signal from the simple refrigeration system 1 that allows it to infer that a defrost cycle has taken place, the rotary speed behavior of the refrigerant compressor 2 is controlled via the preset rotary speed control, and a third cooling cycle C.sub.K3 is begun. Said cooling cycle starts with the starting rotary speed v.sub.1. As soon as the running time exceeds the predefined duration K.sub.v, the rotary speed v of the refrigerant compressor 2 is raised to the first increased rotary speed v.sub.2. Since the actual duration of the third cooling cycle C.sub.K3 also exceeds the limit values of the predefined duration K.sub.v1, K.sub.v2, K.sub.v3, the rotary speed v is increased stepwise to the increased rotary speeds v.sub.3, v.sub.4, and finally to a maximum rotary speed v.sub.max. Only after the third limit value has exceeded the predefined duration K.sub.v3 is the maximum rotary speed v.sub.max, at which the refrigerant compressor 2 produces the maximum cooling output, reached in this embodiment example. The cooling demand of the cooled volume 4 of the refrigeration system 1, which has increased because of the defrost operation, is thus not reached after the preset rotary speed control according to the prior art has run. In this way, on the one hand, the temperature level in the cooled volume, which has increased because of the defrost operation, is not reduced to a lower temperature level in a timely way with the full cooling output of the refrigerant compressor 2.

[0120] Another disadvantage is seen in the previously described setting of a starting rotary speed v.sub.s for the next cooling cycle C.sub.K4 in the third cooling cycle C.sub.K3. Since the maximum rotary speed v.sub.max is reached and the predefined duration K.sub.v is clearly exceeded by the current duration K.sub.3 of the third cooling cycle C.sub.K3, the starting rotary speed v.sub.s of the fourth cooling cycle C.sub.K4 is greatly increased over the starting rotary speed v.sub.1 of the third cooling cycle C.sub.K3 in accordance with the preset rotary speed control. While the increase of the starting rotary speed v.sub.s of the next cooling cycle C.sub.K because of increased cooling demand in the cooled volume 4 as a rule leads to an operation that is as energy optimized as possible, the refrigerant compressor 2 in the case described above will be operated at a rotary speed that is too high for the cooling demand of the cooled volume 4.

[0121] According to the invention, therefore, at least one comparison parameter P.sub.v is stored in the electronic control device 6 of the refrigerant compressor 2, and an exceeding or falling short of the comparison parameter P.sub.v by a current parameter value P.sub.a is monitored in order to detect a preceding defrost operation. In the embodiment example shown in FIG. 5, the comparison parameter is a comparison duration P.sub.v of the rest cycle C.sub.R. For this reason, monitoring to determine if the current duration P.sub.a of the current rest cycle C.sub.R exceeds the comparison duration P.sub.v is continuously carried out. As soon as an exceeding of the comparison duration P.sub.v is detected, a cooling cycle C.sub.K will be not be started upon reception of the switching signal triggered by the thermostat 3, but rather a special cooling cycle C.sub.D that differs from the preset rotary speed control will be initiated.

[0122] Since the rotary speed behavior in the special cooling cycle C.sub.D is controlled according to parameters stored in the electronic control device 6 of the refrigerant compressor 2, it is possible to operate the refrigerant compressor 2 at a high rotary speed v immediately after the end of the defrost operation, in this case already at the maximum rotary speed v.sub.max. Thus, as a direct result of the defrost operation, a high cooling output, in particular a maximum cooling output, is made available by the refrigerant compressor in order to reduce the temperature level of the cooled volume 4 as fast as possible. Through this, on the one hand, the duration of the special cooling cycle C.sub.D is reduced by comparison with the duration of the cooling cycle C.sub.K3 conducted according to the preset rotary speed control (see FIG. 3), and on the other hand, the energy consumption is also lowered through this. It can, for example, be provided that the rotary speed v is kept constant during the entire special cooling cycle C.sub.D, as shown by the solid rotary speed curve in FIG. 5. However, it can also be provided that the refrigerant compressor 2 is operated with a rotary speed behavior like the dashed speed curve illustrates during the special cooling cycle C.sub.D. In this example variation, the refrigerant compressor 2 is driven at the maximum rotary speed v.sub.max over the duration C.sub.D1 and then driven at the third elevated rotary speed v.sub.4 over the duration C.sub.D2, before the refrigerant compressor 2 has been accelerated back to the maximum rotary speed v.sub.max. Basically, any progressive, regressive, or stepwise paths of the speed curve during the special cooling cycle C.sub.D are conceivable.

[0123] In this embodiment example, the starting rotary speed v.sub.s of the following third cooling cycle C.sub.K3 is not affected by the rotary speed behavior during the special cooling cycle C.sub.D, rather, the refrigerant compressor 2 is operated in the following third cooling cycle C.sub.K3 at the rotary speed v.sub.1 specified for it in the second cooling cycle C.sub.K2, since the special cooling cycle C.sub.D is not taken into consideration in establishing the starting rotary speed v.sub.s of the following third cooling cycle C.sub.K3.

[0124] FIG. 6 shows a second embodiment variation of the method according to the invention. While the duration of the rest cycle C.sub.R functioned as a comparison parameter P.sub.v in the previously discussed embodiment example, in this embodiment example, an average load L.sub.m of the refrigerant compressor 2 in a starting phase of the cooling cycle C.sub.K serves as the comparison parameter P.sub.v (not shown). Here, the load L of the refrigerant compressor 2 is determined by measuring the electric current through the refrigerant compressor 2, in particular the electric current flowing through the electric drive unit of the refrigerant compressor 2. After the end of the defrost operation, which again is indicated as DEFROST, a cooling cycle C.sub.K controlled by the preset rotary speed control is started. During the starting phase of the cooling cycle C.sub.K, in this example during the first 50 s after the refrigerant compressor 2 was set to the ON state, the current load L is continuously measured and a current average load L.sub.m is calculated over the duration of the starting phase of the cooling cycle C.sub.K. This current average load L.sub.m is, as the currently measured parameter value P.sub.a, then compared with the comparison parameter P.sub.v stored in the electronic control device 6 of the refrigerant compressor 2. Since the currently measured average load L.sub.m exceeds the stored comparison parameter P.sub.v because of the heating of the refrigerant in the evaporator 5a during the defrost operation and/or because of the high cooling demand of the cooled volume 4, and the electronic control device 6 thus infers that a defrost operation has taken place, the cooling cycle C.sub.K is interrupted after the end of the starting phase and the special cooling cycle C.sub.D is started. Since the load L can only be measured each time during the cooling cycle C.sub.K, the special cooling cycle C.sub.D cannot be started directly on the basis of the switching signal triggered by the thermostat 3, but rather only after the end of the starting phase of the cooling cycle C.sub.K. However, a comparison with the rotary speed behavior in FIG. 4 clearly shows that the refrigerant compressor 2 in this embodiment variation also promptly makes available a high cooling output after the defrost operation, in this case even the maximum cooling output, and the cooled space temperature is accordingly reduced to a lower temperature level faster.

[0125] FIG. 7 shows another aspect of the invention, in which, because of the monitoring of the comparison parameter P.sub.v by the electronic control device 6 of the refrigerant compressor 2 for an interruption of the power supply that has occurred (indicated as POWER BREAK in the drawing), the special cooling cycle C.sub.D is initiated. In order to be able to infer a preceding power outage, the electronic control device 6 monitors the current supply of the refrigerant compressor 2 and thus detects a current outage. However, this information by itself is not enough to make an inference about the initiation of the special cooling cycle C.sub.D, since the electronic control device 6 does not have any information about the duration of the power outage. In the case of a short power outage, the initiation of the special cooling cycle C.sub.D is not purposeful, since the cooled volume temperature will only negligibly rise during the outage. However, if the current interruption lasts longer, the cooled volume 4 will become heated and should be rapidly cooled down by means of the special cooling cycle C.sub.D.

[0126] Therefore, in the electronic control device 6, besides the power outage, the additional temperature T.sub.w is employed as a currently measured parameter value P.sub.a, wherein the additional temperature T.sub.w, as shown in FIGS. 1 and 2, is measured by a temperature measuring device 7, which is either an integral component of the electronic control device 6 of the refrigerant compressor 2 or is disposed on the housing 8 of the refrigerant compressor 2. In this embodiment example, the comparison parameter P.sub.v is a comparison temperature T.sub.v, with which the currently measured additional temperature T.sub.w is compared.

[0127] How much the electronic control device 6 or the housing 8 of the refrigerant compressor 2 has cooled can be tested by comparing the currently measured additional temperature T.sub.w with the comparison temperature T.sub.v. During the normal operation, in which the electronic control device 6 and housing 8 become heated during the cooling cycle C.sub.K, only a partial cooling takes place in the rest cycle C.sub.R before the next cooling cycle C.sub.K is initiated. If the currently measured additional temperature T.sub.w therefore is below the comparison temperature T.sub.v, it can be inferred from this that a cooling cycle C.sub.K has not taken place over a period of time that is longer than average. Because of the information that, on the one hand, a power outage has taken place and, on the other hand, no cooling cycle C.sub.K has taken place over an above-average period of time, the special cooling cycle C.sub.D will be initiated by the electronic control device 6 of the refrigerant compressor 2, since it can be inferred that a lengthy power outage has occurred.

[0128] For the sake of clarity, one is referred to the description of FIG. 5 for the details of the special cooling cycle C.sub.D. It goes without saying here that a plurality of parameters can also be monitored at the same time, thus the duration of the rest cycle C.sub.R and/or the average load L.sub.m and/or the additional temperature T.sub.w.

[0129] It can be provided in alternative embodiment variations of the invention that the additional temperature T.sub.w functions as the currently measured parameter value P.sub.a and the comparison parameter P.sub.v is a comparison temperature T.sub.v, and upon the detection of a deviation of the currently measured additional temperature T.sub.w from the comparison temperature T.sub.v, a special cooling cycle C.sub.D is initiated without a power outage having been detected at the same time, thus in other words a preceding defrost operation can be inferred from the monitoring of the additional temperature T.sub.w, and the corresponding special cooling cycle C.sub.D can be initiated. Likewise, it is conceivable that a special cooling cycle C.sub.D will be initiated if the currently measured parameter P.sub.a is not the additional temperature T.sub.w and a preceding power outage was detected by the electronic control device 6 of the refrigerant compressor 2. For example, a long power outage can be inferred if the currently measured parameter value P.sub.a is the currently measured load L or the currently determined average load L.sub.m and an exceeding or falling short of the comparison parameter P.sub.v was detected.

[0130] Basically, it can be provided in any of the described embodiment variations that the refrigerant compressor 2 is not driven constantly at the maximum rotary speed v.sub.max during the special cooling cycle C.sub.D, but rather at a percentage of said rotary speed, for example at 85% of the maximum rotary speed v.sub.max. It can further be advantageous if the refrigerant compressor 2 does not exceed a predefined rotary speed v.sub.D during the special cooling cycle C.sub.D, wherein the predefined rotary speed v.sub.D is again defined as a percentage of the maximum rotary speed v.sub.max, for example 75%. It is also advantageous if the refrigerant compressor 2 is operated at a high predefined rotary speed v.sub.D immediately after the initiation of the special cooling cycle C.sub.D, wherein the predefined v.sub.D is, for example, 92% of the maximum rotary speed v.sub.max.

[0131] In order to be able to detect the detection [sic] of special operating states better and more reliably, it can be provided in any of the previously described embodiment variations that the currently measured parameter values P.sub.a are stored in the electronic control device 6 of the refrigerant compressor 2 over a plurality of operating cycles C. This is especially advantageous if the value of the comparison parameter P.sub.V is adjusted on the basis of the stored parameter values P.sub.S. For instance, the comparison parameter P.sub.V can, for example, be varied in dependence on an extreme value P.sub.E, thus a minimum or maximum, of the stored parameter values P.sub.S or, for example, in dependence on an average value P.sub.M. The comparison parameter P.sub.V can correspond either directly to the extreme value P.sub.E or to the average value P.sub.M. However, it is advantageous if a multiplicative deviation factor, for example a factor of 1.5, is taken into account in setting the comparison parameter P.sub.V, thus the extreme value P.sub.E or the average value P.sub.M is multiplied by the deviation factor in order to set the value of the comparison parameter P.sub.V. If the stored parameter values P.sub.S change during operation, the comparison parameter P.sub.V will be automatically adjusted.

REFERENCE NUMBERS

[0132] 1 Refrigeration system [0133] 2 Refrigerant compressor [0134] 3 Thermostat [0135] 4 Cooled volume [0136] 5 Cooling line [0137] 5a Evaporator [0138] 6 Electronic control device of refrigerant compressor 2 [0139] 7 Temperature measuring device [0140] 8 Housing of refrigerant compressor 2 [0141] 8a Lower housing section [0142] 8b Upper housing section [0143] K.sub.v Predefined parameter [0144] K.sub.a Current parameter [0145] v Rotary speed [0146] C.sub.R Rest cycle [0147] C.sub.K Cooling cycle [0148] C Operating cycle