US20190310004A1

US20190310004A1 - Method for operating a rotational-speed-variable refrigerant compressor

Info

Publication number: US20190310004A1
Application number: US16/465,936
Authority: US
Inventors: Ulrich Gries; Jürgen Ewald Gläser; Allan Haue SLOT; Hans-Erik Fogh
Original assignee: Nidec Global Appliance Germany GmbH
Current assignee: Secop GmbH
Priority date: 2016-12-01
Filing date: 2017-12-01
Publication date: 2019-10-10
Also published as: EP3548812A1; CN110234942A

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.

Description

FIELD OF THE INVENTION

The invention concerns a method for operating a refrigerant compressor having a variable rotary speed for cooling a cooled volume of a refrigeration system, wherein the refrigeration system comprises at least one thermostat for direct or indirect monitoring of a temperature state of the cooled volume and wherein the refrigerant compressor is operated cyclically and a cooling cycle of the refrigerant compressor begins when the refrigerant compressor is set to an ON state by a switching signal triggered by the thermostat, and the cooling cycle ends when the refrigerant compressor is set to an OFF state by another switching signal triggered by the thermostat, wherein an operating cycle comprises, in addition to the cooling cycle, a rest cycle that follows the cooling cycle, and wherein the rotary speed behavior of the refrigerant compressor is controlled during a cooling cycle by means of a preset rotary speed control that is stored in an electronic control device of the refrigerant compressor; and an electronic control device for controlling the cyclic operation of a variable-speed refrigerant compressor. The electronic control device of the refrigerant compressor is frequently also called the electronic control and regulation device of the refrigerant compressor.
Preferably, the rotary speed behavior of the refrigerant compressor during a cooling cycle is controlled on the basis of at least one predefined parameter by means of a preset rotary speed control stored in an electronic control device of the refrigerant compressor, by monitoring the at least one predefined parameter with regard to a current parameter of a current cooling cycle exceeding and/or falling short of it.
Variable-speed refrigerant compressors can be used in connection with many various refrigeration systems and refrigeration equipment, thus, for example, refrigerators or refrigerated display cases, freezers, air conditioners, or heat pumps. They offer the advantage over fixed-speed refrigerant compressors that they are able to operate in an energy optimized way and can adjust the delivered cooling output to the cooling requirement relative to the cooled volume.
Optimally, variable-speed refrigerant compressors are used in refrigerant systems that have their own electronic control device and components for monitoring the operating state of the refrigerant systems. As a consequence, such refrigerant systems are called smart refrigerant systems. In this case, various switching signals, parameters, and measurements are processed in the electronic control unit of the refrigeration system, which is different from the electronic control device of the refrigerant compressor, and a control signal is generated from said input parameters and transmitted to the electronic control device of the refrigerant compressor. This control signal can, for example, be a rotary speed setting, which, depending on the current temperature or the path of the temperature of the cooled volume, tells the electronic control device of the refrigerant compressor the rotary speed with which the refrigerant compressor is to be operated, or if the electronic control device of the refrigerant compressor is to turn it on or off.
Therefore, the operation, in particular the rotary speed behavior of a variable-speed refrigerant compressor, is controlled in smart refrigerant systems by the interplay of the electronic control unit of the refrigeration system with the electronic control device of the refrigerant compressor, wherein the electronic control unit of the refrigeration system as a rule sends already specified refrigeration requirements to the electronic control device of the refrigerant compressor.
The current invention, however, concerns a different kind of refrigeration system, namely ones that do not have an electronic control unit that can communicate with the electronic control device of the refrigerant compressor and that do not have electronic components for monitoring the operating state of the refrigeration system. Such refrigeration systems therefore are called simple refrigeration systems in what follows. They comprise at least one thermostat, which monitors the temperature state of the cooled volume and, depending on the current temperature state, triggers a switching signal that sets the refrigerant compressor to the ON state or sets it to the OFF state. Simple refrigeration systems do not communicate a rotary speed setting to the electronic control device of the refrigerant compressor or any other data. They are also not capable of recording other operating parameters such as the temperature of the cooled space or the path of the temperature and calculating the refrigeration requirements on the refrigerant compressor from them.
Cooling output is either demanded or not demanded by the thermostat, but without quantifying it, i.e., the rotary speed regulation of the refrigerant compressor is solely undertaken by the electronic control device of the refrigerant compressor, thus by its programming.
In order to nevertheless be able to use the fundamental advantage of variable-speed refrigerant compressors over fixed-speed refrigerant compressors, it is necessary that the rotary speed behavior of the refrigerant compressor controlled by the electronic control device of the refrigerant compressor be as optimized as possible with respect to a defined parameter, for example with respect to energy consumption.
“As energy optimized as possible” is in this case to be understood to mean that the current consumption or energy consumption of the refrigerant compressor is particularly low at the cooling of the cooled volume required for the relevant application and the refrigerant compressor therefore can be operated in a resource-conserving way.
The fact that the electronic control device of the refrigerant compressor does not obtain any information from the refrigeration system about its operating state, in particular it does not receive a rotary speed setting, is seen as a complicating factor here.
This disadvantage is compensated in practice by the fact that simple refrigeration systems are characterized by having a lower purchase price than smart refrigeration systems, due to which they are nevertheless very popular worldwide.

PRIOR ART

Both variable-speed and fixed-speed refrigerant compressors produce a circulation of a refrigerant in a closed refrigerant system. The refrigerant becomes heated by absorption of energy from the cooled volume in an evaporator and in the end becomes superheated and is pumped to a higher pressure by a piston moving back and forth in a cylinder housing in a piston-cylinder unit, wherein the refrigerant releases heat via a condenser and is transported back to the evaporator via a choke, in which a reduction of pressure and cooling of the refrigerant takes place. The movement of the piston is implemented via a crank mechanism comprising a crankshaft that is driven by an electric drive unit.
The refrigeration process described above runs during a cooling cycle of the refrigerant compressor, wherein the refrigerant compressor is driven during the cooling cycle and has a rotary speed behavior controlled by the electronic control device of the refrigerant compressor, wherein the electronic control device controls the electric drive unit of the refrigerant compressor.
A cooling cycle starts via a switching signal triggered by the thermostat of the refrigeration system, which sets the refrigerant compressor to the ON state. For example, the thermostat triggers a switching signal for the ON state of the refrigerant compressor when the temperature level in the cooled volume or a cooled volume temperature or a temperature representative of the cooled volume temperature exceeds a preset maximum value. For purposes of monitoring the temperature state of the cooled volume, the thermostat can, for example, be made as a vapor pressure-based thermostat, in particular as a bellows thermostat, or can have a bimetallic strip or an NTC (negative temperature coefficient) element as temperature sensor.
The refrigerant compressor is driven or remains in the cooling cycle, in which the refrigeration process takes place, until the electronic control unit of the refrigerant compressor receives another switching signal triggered by the thermostat, which sets the refrigerant compressor to the OFF state. Said signal in this case can be triggered, for example, when the temperature level or a cooled volume temperature or a temperature representative of the cooled volume temperature has fallen below a preset minimum value because of cooling in the cooled volume that has taken place in the cooling cycle.
In order to enable the cooling of the cooled volume to be as energy optimized as possible, the electronic control device of the refrigerant compressor operates according to a programmed specification during the cooling cycle, which controls the rotary speed behavior of the refrigerant compressor during a cooling cycle. This preset rotary speed control enables variable-speed refrigerant compressors to be controlled individually, or energy optimized, within the scope of the programmed specification even in simple refrigeration systems, which, as noted above, do not themselves have an electronic control unit that is capable of communicating with the electronic control device of the refrigerant compressor.
The preset rotary speed control is set so that at least one current parameter that can be detected by the electronic control of the refrigerant compressor during a cooling cycle is compared with at least one predefined parameter stored in the electronic control device and the rotary speed behavior of the refrigerant compressor is controlled in dependence on it. In other words, the refrigerant compressor is controlled by means of the preset rotary speed control stored in the electronic control device on the basis of at least one predefined parameter, by monitoring the at least one predefined parameter with regard to a current parameter of a current cooling cycle exceeding or falling short of it.
The at least one predefined parameter can involve various parameters, for example the electric load of the refrigerant compressor, which is determined by measuring the electric current through the refrigerant compressor, in particular the electric current flowing through the electric drive unit of the refrigerant compressor during the cooling cycle.
More preferably, however, the predefined parameter is the duration of a cooling cycle. The predefined parameter in this case stands for the value of the parameter at which a cyclic operation that is as energy optimized as possible is enabled for a preset rotary speed behavior during a cooling cycle, preferably at as low as possible a rotary speed at which the electric motor driving the refrigerant compressor can be operated with high efficiency.
In other words, a temperature level in the cooled volume of the refrigeration system is to be permanently kept as energy optimized as possible by the preset rotary speed control. If the duration of a cooling cycle is the predefined parameter, the preset rotary speed control causes the electronic control device of the refrigerant compressor to change its rotary speed either immediately or in the next cycle if the preset duration is exceeded or not reached, thus if the time between the demand of the thermostat of the simple refrigeration system to switch the refrigerant compressor on or off is longer or shorter than the predefined parameter, with the goal of subsequent cooling cycles again having a duration that corresponds to the predefined parameter (duration), so that the refrigerant compressor can again be operated as energy optimized as possible in every cooling cycle.
Such a preset rotary speed control for operation of a variable-speed refrigerant compressor in a simple refrigeration system is known, for example, from DE 1092013114374. In this case, the control of the rotary speed behavior takes place either during the current cooling cycle, wherein the rotary speed of the refrigerant compressor is increased if it was detected that the current parameter exceeded the at least one predefined parameter (the duration of a cooling cycle in that patent). Such an increase can also take place several times during a cooling cycle if the current parameter exceeds a plurality of predefined parameters, i.e., if, for example, in spite of increasing the rotary speed the thermostat still does not initiate a switching signal to switch off the refrigerant compressor, because the temperature level or a cooled volume temperature or a temperature representative of the cooled volume temperature in the cooled volume is still too high.
The increase can take place, for example, progressively, regressively, linearly, or stepwise.
If the electronic control unit detects, for example after multiple cooling cycles of the refrigerant compressor, that the, also multiple, increases of the rotary speed in each cooling cycle still does not result in the predefined parameter, for example the predefined duration of a cooling cycle, being able to be maintained, then it can also be provided according to the prior art that the starting rotary speed of one or more subsequent cooling cycles will already be set to be higher than is envisaged in the energy optimized case.
It can equally be provided that the starting rotary speed of a subsequent cooling cycle is reduced if the at least one predefined parameter is not reached.
How accurately the rotary speed behavior of the refrigerant compressor is represented on the basis of the preset rotary speed control is dependent on the individual programming that is provided by the refrigerant compressor manufacturer upon delivery of the refrigerant compressor. In any case, it is important that the preset rotary speed control, which controls the rotary speed during a cooling cycle, takes place as a function of a predefined parameter.
The at least one predefined parameter is selected by the manufacturer of the refrigerant compressor so that known operating parameters of the refrigeration system such as heat or cold losses in the cooled volume and/or in the refrigerant system and possibly expected ambient temperatures are taken into account, so that the variable-speed refrigerant compressor runs as energy optimized as possible during the cooling cycle due to the preset rotary speed control. If there are deviations of a current parameter corresponding to at least one predefined parameter from the at least one predefined parameter during a current cooling cycle, the preset rotary speed control serves to control the rotary speed behavior of the refrigerant compressor so that the current parameter essentially again corresponds to the predefined parameter as quickly as possible, either during the current cooling cycle or at least in a subsequent cooling cycle or within a few subsequent cooling cycles.
A disadvantage of the control of the prior art lies in the fact that the electronic control device of the refrigerant compressor is not capable of reacting to any special operating states such as an increased cooling demand after a defrost operation or after a power outage. These special operating states and the problems connected with them are briefly described below.
Even simple refrigeration systems run a defrost operation at certain time intervals, wherein the area around the evaporator is heated during a defrost operation, for example by heating elements, so as to remove or defrost ice or frost deposits that have built up in the vicinity of the evaporator in the cooled volume of the refrigeration system. This ensures maintenance of an efficient cooling of the cooled volume, since the ice or frost deposits, in particular if they have built up a solid layer, act as an insulating layer and prevent the exchange of heat between the cooled volume and the evaporator. The refrigerant that is in the evaporator unavoidably becomes heated during the defrost operation.
Simple refrigeration systems in this case are controlled as a rule so that a timer initiates a defrost operation at periodic intervals, provided the refrigerant compressor was set into the OFF state due to the further switching signal triggered by the thermostat. During the defrost operation, the thermostat does not trigger a switching signal to set the refrigerant compressor to the ON state, so that the refrigerant compressor remains in the OFF state during the defrost operation. When the defrost operation is over, the switching signal is triggered by the thermostat because of the deviation of the temperature level in the cooled volume or the cooled volume temperature or the temperature representative of the cooled volume temperature detected due to the heating of the evaporator and the refrigerant compressor starts a cooling cycle in accordance with the preset rotary speed control.
Another problem in simple refrigeration systems results from the fact that simple refrigeration systems are often operated in regions with weak infrastructure, in which a steady supply of electricity is not guaranteed, rather interruptions of the electricity supply are the order of the day. In each case according to the duration of the power outage, the temperature in the cooled volume rises. As soon as the power supply is restored, the switching signal is triggered by the thermostat and the refrigerant compressor starts a cooling cycle in accordance with the preset rotary speed control.
Since simple refrigerant compressors [sic; systems] themselves do not have an electronic control unit that is capable of communicating with the electronic control device of the refrigerant compressor, a cooling cycle in which the rotary speed is controlled in accordance with the preset rotary speed control is triggered in the electronic control device of the refrigerant compressor in both special operating states, thus after the end of a defrost operation and after a power outage. This results in the rotary speed of the refrigerant compressor being increased stepwise, thus the available cooling output rises slowly, even though the cooling demand for cooling the cooled volume is considerably higher after the defrost operation or because of the warming as a consequence of the power outage than in the case of a normal operation-related increase of the cooling demand, for which the preset rotary speed control is designed. This results in the length of the cooling cycle that follows the special operating state being disproportionately higher than the duration of the preceding cooling cycles and an increased energy consumption of the refrigerant compressor resulting from the long duration of the cooling cycle.

OBJECT OF THE INVENTION

Therefore, it is an object of the invention to overcome the disadvantages of the prior art and to propose a method for operating a variable-speed refrigerant compressor having an electronic control device so that in the operation of such a variable-speed refrigerant compressor with a simple refrigeration system, which does not have its own electronic control unit that can communicate with the electronic control device of the refrigerant compressor, which method enables an adjustment of the rotary speed behavior in reaction to a special operating state that has occurred, in order to lower the cooled space temperature as quickly as possible and as energy-optimized as possible.

DESCRIPTION OF THE INVENTION

The invention concerns a method for operating a variable-speed refrigerant compressor as a part of a simple refrigeration system that does not have its own control unit, of the kind mentioned at the start.
In order to detect, in the electronic control device of the refrigerant compressor, a special operating state of the refrigeration system that has occurred, it is provided according to the invention that at least one comparison parameter is stored in the electronic control device of the refrigerant compressor, and an exceeding or falling short of the comparison parameter by a current measured parameter value is monitored. While the monitoring of the at least one characteristic parameter in the preset rotary speed control is aimed only at a normal operation of the refrigerant compressor and is aimed for an operation of the refrigerant compressor that is as energy optimized as possible during such a normal operation, the monitoring of the comparison parameter is designed to detect a special operating state of the refrigeration system that has occurred, in particular a defrost operation or a power outage, and therefore represents a second monitoring state that is separate from the monitoring state necessary for the preset rotary speed control. However, it is conceivable that the at least one comparison parameter is the same measured parameter as in the case of the at least one parameter, but the measured parameter is monitored in different methods.
When the comparison parameter and the characteristic parameter are the same measured parameter, it is necessary that the specifically established values or value ranges of the comparison parameter and characteristic parameter differ from each other. In particular, it can be provided that the comparison parameter is a value of the measured parameter that is not associated with the normal operation or at which the normal operation is no longer the optimum operating state, since, for example, the required cooling capacity can no longer be made available by means of the preset rotary speed control. In other words, the comparison parameter can be a value of the measured parameter that lies outside of the normal operation controlled by means of the preset rotary speed control.
The at least one comparison parameter is a quantity that the electronic control device of the refrigerant compressor can detect and monitor itself without being dependent on additional data from a control unit of the refrigeration system, which is not present in simple refrigeration systems. The duration of the operating cycles of the refrigerant compressor, in particular the cooling cycle and rest cycle, and also the load of the refrigerant compressor measured as the current of the refrigerant compressor or another temperature that is independent of the temperature of the cooled volume are in this case conceivable as the at least one comparison parameter. The monitoring of two or three different comparison parameters, for example thus the load and duration of an operating cycle or the load and/or duration of an operating cycle and an additional temperature, is also conceivable, wherein the at least one comparison parameter in this case comprises two or three comparison parameters, each of which represent different measured quantities.
This also applies correspondingly to the relevant current measured parameter value, which in each case is associated with a comparison parameter and correspondingly refers to the same measured quantity as the associated comparison parameter, in order to be able to detect an exceeding or falling short of the comparison parameter or the value of the comparison parameter. In other words, the current parameter value is a currently measured value of the measured quantity, which can be compared with the comparison parameter.
The comparison parameter in this case can be stored in the electronic control unit as a preset value, thus already defined by the manufacturer, but can also be redetermined continuously in operation, in order to enable the detection of the defrost operation as a departure from the preset rotary speed control, as described below in more detail. The value of the at least one comparison parameter is in this case a limit value, which is set so that if the comparison parameter is exceeded or fallen short of by the current parameter value, an inference can be made with respect to a special operating state that has occurred, in particular a defrost operation or a power outage.
As soon as a preceding special operating state has been detected, the refrigerant compressor is operated with a special cooling cycle that is different from the preset rotary speed control in order to be able to adjust the rotary speed behavior of the refrigerant compressor to the effects of the special operating state and possibly to send a high cooling output to the cooled volume after the detection of the special operating state. This is why it is provided according to the invention that a special cooling cycle that is different from the preset rotary speed control is triggered when the currently measured parameter value exceeds or falls short of the comparison parameter. The detection of the special operating state can take place at any time point in the operating cycle, for example during the rest cycle, directly at the start of a cooling cycle, or during a cooling cycle, in each case according to which comparison parameter is being monitored. For example, it can be provided in the case of a detection that has taken place during the rest cycle or at the start of the cooling cycle that the special cooling cycle is started instead of an originally intended standard cooling cycle. In this case, the switching signal triggered by the thermostat, which sets the refrigerant compressor to the ON state, triggers the special cooling cycle. If the detection of the special operating state takes place during a cooling cycle, the cooling cycle is interrupted and the special cooling cycle is started.
As a rule, the special cooling cycle is characterized by a rotary speed behavior having an average rotary speed that is higher than the average rotary speed of the preset rotary speed control. An increased cooling output of the refrigerant compressor results directly from the increase of the average rotary speed. Here, the average rotary speed means the rotary speed averaged over the duration of the cooling cycle, for instance as the arithmetic, geometric, or harmonic average.
Therefore, the object stated above is solved for a simple refrigeration system in a method according to the invention of the kind described at the start in that

- at least one comparison parameter is stored in the electronic control device of the refrigerant compressor and an exceeding or falling short of the comparison parameter by a current measured parameter value is monitored,
- a special cooling cycle that is different from the preset rotary speed control is initiated if the current measured parameter value exceeds or falls short of the comparison parameter,
- optionally, a current cooling cycle controlled by the preset rotary speed control is interrupted by the special cooling cycle.

Analogously, the invention also concerns an electronic control device for control of the cyclic operation of a variable-speed refrigerant compressor, wherein the electronic control device is configured

- to switch on 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 and to end a rest cycle and
- to switch off again an additional switching signal triggered by the thermostat in order to end the cooling cycle and to begin a rest cycle and
- to control the rotary speed behavior of the refrigerant compressor during a cooling cycle by means of a preset rotary speed control stored in the electronic control device.

The object stated at the start is solved in this case in that at least one comparison parameter 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 by a current measured parameter value,
- to initiate a special cooling cycle that is different from the preset rotary speed control when the current measured parameter value exceeds or falls short of the comparison parameter,
- optionally, to interrupt a current cooling cycle controlled by the preset rotary speed control in order to begin the special cooling cycle.

In an embodiment of the method according to the invention it is provided that the at least one monitored comparison parameter is a load of the refrigerant compressor in a starting phase of a cooling cycle. On the one hand, the load of the refrigerant compressor is suitable as an operating parameter, since it can easily be detected by measuring the electric current through the refrigerant compressor, in particular through the electric current flowing through the electric drive unit of the refrigerant compressor during the cooling cycle. The starting phase of the cooling cycle begins as soon as the refrigerant compressor has been set to the ON state due to reception of the switching signal triggered by the thermostat.
The principle will be briefly explained using a preceding defrost operation as an example: Because of the heating of the refrigerant in the evaporator during the defrost operation or because of the high cooling demand, the load of the refrigerant compressor is especially high after a preceding defrost operation. If the currently measured load therefore exceeds the comparison value of the load that has been stored as comparison parameter, the electronic control device of the refrigerant compressor will infer that a defrost operation has taken place and the special cooling cycle will be started. As a rule, a current cooling cycle will be interrupted in order to start the special cooling cycle, thus, in other words, the preset rotary speed control will be switched off in order to be able to conduct the special cooling cycle. The electronic control device of the refrigerant compressor in this case comprises switches or electronic components via which the at least one operating parameter can be determined or measured.
Similarly, it is also provided in an embodiment of the electronic control device according to the invention that 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 and the currently measured parameter value are loads.
If the monitored comparison parameter is the load, it is advantageous not to set a specific value of the load as comparison parameter, since the danger of an error detection would be elevated. Rather, it is purposeful to employ an average load, which is measured over a defined starting phase of the refrigerant compressor. The average load in this case is understood to be the average value of the loads, thus the sum of all detected individual loads measured during the starting phase, for example as arithmetic, geometric, or harmonic averages, over the duration of the starting phase. In this way, individual outliers of the load value can be neglected and a load behavior can be modelled. In addition, the preceding special operating state can be better monitored while monitoring the average load, since because of the heating of the refrigerant in the refrigeration system, the load of the refrigerant compressor over the starting phase of the cooling cycle, as a rule at least over the first 30 s of the cooling cycle, is relatively high. Therefore, in another embodiment of the method according to the invention it is provided that the load is monitored as the average load measured over the duration of the start phase, wherein the duration of the start phase is preferably between 10 s and 90 s, in particular between 30 s and 80 s, especially preferably between 40 s and 70 s.
The duration of the rest cycle is also especially suitable as comparison parameter, since during the normal operation according to the preset rotary speed control, the duration of the rest cycle does not as a rule exceed a maximum value. Therefore, in another embodiment of the method according to the invention it is provided that the at least one monitored comparison parameter is a duration of the rest cycle. In other words, because of the cooling losses and/or insulation losses in the cooled volume, a duration is set, within which the target temperature state of the cooled volume is again exceeded after the end of the cooling cycle and thus the next cooling cycle is initiated. As a rule, however, the special operating state leads to a longer duration of the rest cycle, for example up to 15 minutes. If the monitored operating parameter is the duration of the rest cycle, the comparison parameter is defined, for example, as the maximum value of the duration of the rest cycle. If the actual duration of the current rest cycle exceeds the comparison parameter, the electronic control unit will infer from this deviation that the refrigeration system is conducting a defrost operation. Therefore, upon input of the next switching signal triggered by the thermostat, the special cooling cycle can immediately be started. Of course, it is conceivable that both the load and the duration of the rest cycle are monitored by the electronic control device and the special cooling cycle is initiated when, at least from the monitoring of one of the two monitored parameters, preferably both of the monitored parameters, a preceding defrost operation is inferred and the special cooling cycle is initiated.
Similarly, it is also provided in an embodiment of the electronic control device according to the invention that the electronic control device is configured to determine a duration of the rest cycle and that the stored comparison parameter and the currently measured parameter value are the duration of a rest cycle.
In particular to detect an interruption of the power supply as a preceding special operating state, it is provided in a preferred embodiment of the invention that

- an additional temperature independent of the temperature of the cooled volume is measured,
- the currently measured parameter value is the additional temperature,
- the at least one monitored comparison parameter is a comparison temperature.

The detection and averaging of the additional temperature, which is independent of the temperature level of the refrigerant compressor monitored by the thermostat, represents information in addition to the switching signals of the thermostat for the electronic control device of the refrigerant compressor. As a result, the additional temperature is measured by a temperature measuring device, which is a component of the electronic control device of the refrigerant compressor or is disposed on a housing of the refrigerant compressor. Thus, the additional temperature provides an inference about the operating temperature of the electronic control device of the refrigerant compressor. By comparing the currently measured additional temperature as the currently measured parameter value and the comparison temperature as comparison parameter, it is possible, for example, to establish that the refrigerant compressor was not in operation over a long period of time if the currently measured additional temperature is above the comparison temperature. Thus, the monitoring of the additional temperature can indicate a previous special operating state, thus a defrost operation or a power outage.
Similarly, in another preferred embodiment of the electronic control device according to the invention it is provided that the electronic control device is connected to a temperature measuring device to measure an additional temperature that is independent of the temperature of the cooled volume and that the stored comparison parameter is a comparison temperature and the currently measured parameter value is the additional temperature. The temperature measuring device can be, for example, made as a measurement probe, a resistance thermometer, a thermoelement, or a temperature sensor.
Normally, electronic control devices are capable of establishing a preceding power outage. However, they are not able to determine how long the power supply was interrupted. If the outage was short, it would not be purposeful to initiate a special cooling cycle, since only a small additional cooling demand exists in the cooled volume. Therefore, a special cooling cycle is only initiated if the electronic control device of the refrigerant compressor has established a power outage and the comparison parameter is exceeded or fallen short of by the currently measured parameter value. In this way, it can be ensured that the special cooling cycle is only initiated when an interruption of the power supply has been established and it has been verified on the basis of the exceeding or falling short of the comparison parameter by the currently measured parameter value that indeed an elevated cooling demand exists in the cooled volume.
Preferably, either the load, especially the average load, or the additional temperature is employed as the currently measured parameter value for the inference of a power outage, wherein the comparison parameter is likewise a load, in particular an average load in the former case, or is a comparison temperature in the second case. For example, an inference can be made about the duration of the power outage from the deviation of the currently measured temperature from the comparison temperature, which deviation results from the cooling of the electronic control device of the refrigerant compressor or the cooling of the refrigerant compressor itself.
Therefore, in an especially preferred embodiment of the method according to the invention it is provided that

- the electronic control device of the refrigerant compressor monitors to determine if a power supply of the electronic control device has been interrupted,
- and the special cooling cycle is initiated if both an exceeding or falling short of the comparison parameter by the currently measured parameter value and a preceding power outage are detected.

Likewise, said advantageous method is also achieved in an electronic control device according to the invention in that
the electronic control device is configured

- to detect a power outage and
- to initiate a special cooling cycle, if both an exceeding or falling short of the comparison parameter by the currently measured parameter and a preceding power outage have been detected.

In an especially preferred embodiment of the electronic control device according to the invention it is provided that 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, in order to be able to determine an operating temperature of the electronic control device of the refrigerant compressor or of the refrigerant compressor.
Normally, the electronic control device of the refrigerant compressor already comprises a temperature measuring device for other purposes, for example for monitoring the temperature of the electronic control device to prevent overheating, so that the electronic control device does not become more expensive due to implementation of this aspect of the invention and the measured values of said temperature measuring device can be employed as the additional temperature according to the invention.
An additional advantage of the use of the measured values of a temperature measuring device already provided in a traditional electronic control device as the additional measured temperature lies in the fact that only the programming of the electronic control device of the refrigerant compressor needs to be altered and not the structure of the electronic control device itself. In this way, refrigerant compressors already in use can be easily adapted for carrying out the method according to the invention.
Likewise, it is provided in a second especially preferred embodiment of the invention that the additional temperature is measured by a temperature measuring device and the temperature measuring device is mounted on a housing of the refrigerant compressor. Since the refrigerant compressor and electronic control device of the refrigerant compressor are usually manufactured as a module and are supplied to the manufacturer of a refrigeration system, the functioning of the method according to the invention can also be ensured when the temperature measuring device is disposed on the housing of the refrigerant compressor. Thereby, the temperature measuring device is a part of the supplied module and the functionality of the method is guaranteed to be independent of any assembly or connection errors of the manufacturer of the refrigeration system. Especially preferably, the temperature measuring device is disposed on an outer side of the housing, while the components of the refrigerant compressor, thus at least the electric drive unit and the piston-cylinder unit, are disposed within the housing of the refrigerant compressor.
In order to enable the detection of a special operating state in a simple way on the basis of a change of the current operating state of the refrigerant compressor without having to rely on a stored comparison parameter that was predefined in the as-supplied state and stored in the control device of the refrigerant compressor, in another preferred embodiment of the method according to the invention it is provided that the at least one measured current parameter value is stored as the stored parameter value in the electronic control device of the refrigerant compressor over at least two operating cycles. This allows a special operating state to be inferred from the development of the stored parameter values. Preferably, the stored parameter values are stored over 3, 4, 5, 8, or 10 operating cycles in order to be able to monitor and model the operating behavior as accurately as possible.
If the currently measured parameter value is the additional temperature, the measured additional temperature can, for example, be stored at the start of the cooling cycle and/or the measured additional temperature can be stored at the end of the cooling cycle. For example, a cooling rate can be determined via the stored temperatures at the beginning of a cooling cycle and/or at the end of a cooling cycle, via which rate an expected additional temperature is determined at the start of the next cooling cycle, wherein the expected additional temperature is defined as the comparison temperature, optionally while employing a multiplicative deviation factor.
Thus, it is advantageous if the comparison parameter is not predefined as a fixed value in the electronic control device of the refrigerant compressor, but rather is continuously modified in dependence on an extreme value, thus a maximum value or a minimum value, of the stored parameter values, possibly taking into account a multiplicative deviation factor. It is also conceivable that the extreme value of the stored parameter values is determined and used directly as comparison parameter. Therefore, in an especially preferred embodiment of the invention it is provided that an extreme value of the stored parameter values in the electronic control device of the refrigerant compressor is selected and the comparison parameter is determined in dependence on the extreme value of the stored parameter values, preferably it corresponds to the extreme value.
Instead of the extreme value, an average value of the stored parameter values is also suitable for the most accurate modelling and monitoring of the operating behavior of the refrigerant compressor. The average value can be calculated, for example, as the geometric, arithmetic, or harmonic mean value of the stored parameter values. Also, the comparison value can be continuously modified in dependence on the average value, for example taking into account a multiplicative deviation factor. Likewise, it is again conceivable that the average value of the stored parameter values is determined and used directly as comparison parameter.
For example, the current load or the current average load and/or the current duration of the rest cycle and/or the measured additional temperature can be compared with the corresponding extreme values and/or average values determined from the stored parameter values in order to be able to infer reliably that a special operating state has occurred and correspondingly to initiate the special cooling cycle.
Here it should be seen as particularly advantageous that the comparison parameter can take into account possible variations of the operating state in that a predefined deviation factor stored in the electronic control device of the refrigerant compressor is multiplied by the extreme value or the average value in order to define the comparison parameter. Thus, operation-related variations in the current parameter values do not initiate a special cooling cycle. Therefore, in another especially preferred embodiment it is provided that the comparison parameter is determined by multiplying the extreme value or the average value by a deviation factor, wherein the deviation factor is at least 1.25, preferably at least 1.50, especially preferably 1.75, especially 2.0.
According to the prior art, the preset rotary speed control can be configured so that a new starting rotary speed for the next cooling cycle can be set in dependence on the rotary speed behavior of a current operating cycle, for example the maximum rotary speed or average rotary speed. If the special operating state is not detected and thus a special cooling cycle cannot be initiated, but rather, a normal cooling cycle follows the special operating state, the long duration of said cooling cycle and the high rotary speed will also have a negative effect on the following operating cycles: The increased cooling demand results solely from the effects of the special operating state and not from a fundamentally higher cold demand of the cooled volume. Nonetheless, according to the preset rotary speed control, the rotary speed of the next cooling cycle will be increased so that the refrigerant compressor is not driven in an energy optimized way. The higher the average rotary speed was in the cooling cycle following the special operating state, the larger the number of cooling cycles that must be run through before the rotary speed has adjusted to the required rotary speed. Since, however, a detection of the special operating state takes place according to the invention, said disadvantage of the prior art can be overcome in that the special cooling cycle is not taken into account in the setting of the starting rotary speed of the next cooling cycle after the special cooling cycle, rather, it is set to a starting rotary speed setting from the last completed cooling cycle that is stored in the electronic control device. Therefore, in an especially preferred embodiment of the invention it is provided that a starting rotary speed of the refrigerant compressor is set to a value stored in the electronic control device for the cooling cycle following the special cooling cycle.
An especially effective cooling of the cooled volume as a response to a special operating state like a defrost operation or power outage is achieved in another embodiment of the invention in that the refrigerant compressor is operated during the special cooling cycle so that a higher average cooling output is supplied to the cooled volume than in a comparable cooling cycle controlled in accordance with the preset rotary speed control. The increased cooling output is achieved through an increased rotary speed of the refrigerant compressor.
A preferred embodiment of the method according to the invention calls for the refrigerant compressor to be operated during the special cooling cycle so that the rotary speed does not go below a defined rotary speed until the end of the special cooling cycle, wherein the defined rotary speed is at least 75%, preferably at least 85%, especially preferably at least 90%, in particular between 95% and 100%, of a maximum rotary speed of the refrigerant compressor. A high value of the defined rotary speed, which is to be understood as a minimum rotary speed, with respect to the maximum rotary speed of the refrigerant compressor, ensures the provision of a high cooling capacity or cooling output by the refrigerant compressor. Here, the refrigerant compressor can be operated, for example, at a first defined rotary speed of 95% of the maximum rotary speed over a first defined time period [and] at a second defined rotary speed of 80% of the maximum rotary speed over a second defined time period, wherein the cycles repeat alternatingly until the special cooling cycle ends.
In order to be able to lower the temperature of the cooled volume that was raised because of the special operating state as promptly as possible, thus to be able to produce a high cooling output immediately after the detection of the special operating state, it is provided in another embodiment of the invention that the refrigerant compressor is accelerated to a predefined rotary speed at the beginning of the special cooling cycle, wherein the at least one defined rotary speed is at least 70%, more preferably at least 80%, especially preferably at least 90%, in particular between 95% and 100% of a maximum rotary speed of the refrigerant compressor.
The object stated at the start is also solved by a module comprising

- a variable-speed refrigerant compressor having 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 in accordance with the invention for control of the cyclic operation of the variable-speed refrigerant compressor according to a method according to the invention. Such a module can be easily installed in a refrigeration system without a control unit of the refrigeration system transmitting a control signal or a rotary speed setting to the electronic control device of the refrigerant compressor.

BRIEF DESCRIPTION OF THE FIGURES

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.

Here:

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

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

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;

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;

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;

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;

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

FIG. 1 shows a simple refrigeration system 1 with a variable-speed refrigerant compressor 2, a refrigerant line 5, and an evaporator 5 a. Refrigerant compressor 2, refrigerant line 5, and evaporator 5 a form a closed refrigerant system in which refrigerant circulates during the operation, thus during a cooling cycle C_Kof 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 5 a by evaporating the refrigerant in evaporator 5 a.
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_Kaccording to a programmed setting, which controls the rotary speed behavior C_Kof the refrigerant compressor 2 during a cooling cycle C_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.
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.
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 5 a 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.
According to one aspect of the invention, a temperature measuring unit 7 is provided, via which an additional temperature T_wthat 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.
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 8 a and an upper housing section 8 b. In this embodiment example, the temperature measuring unit 7 is mounted on an outer surface of the upper housing part 8 b. The reference numbers 7′ and 7″ designate alternative attachment positions, shown as dashed lines, on an outer side of the housing lower part 8 a, 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

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_v, which is stored in the electronic control device 6 of the refrigerant compressor 2, during a cooling cycle C_K, and the at least one parameter value K_vis monitored with respect to its being exceeded and/or fallen short of by a current parameter K_aof a current cooling cycle C_Ka.
In this embodiment example, the at least one predefined parameter K_vis the duration of a cooling cycle C_K. Here, the current running time and the actual duration of the cooling cycle C_Kare monitored by the electronic control device 6.
FIG. 3 shows, as an example, three operating cycles C₁, C₂, C₃, 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_Rand a cooling cycle C_K, wherein the refrigerant compressor 2 is in operation during a cooling cycle C_Kand force-circulates refrigerant through the refrigeration system to cool the cooled volume 4. On the other hand, in the rest cycle C_R, the refrigerant compressor 2 is not driven and essentially no cooling of the cooled volume 4 takes place.
The first cooling cycle C_K1is begun at time t₁by 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 t₁. 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 v₁. At time t₂, which corresponds to the predefined duration of the cooling cycle C_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.
Thus, a further cooling requirement exists in the cooled volume 4 at time t₂. 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 v₁, to a first increased rotary speed v₂. 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_Kcan be quickly ended.
At time t₃, which corresponds to a limit value of a data record stored in the predefined running time K_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 v₃takes place for the reasons given above.
At time t₄, 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_R2is initiated. The time that has passed between times t₁and t₄corresponds to the actual duration K₁of the first cooling cycle C_K1. Since the actual duration K₁is greater than the predefined duration K_v, it can be provided either that the next cooling cycle C_K2is begun without change in accordance with the preset rotary speed control, with the risk that it must be readjusted as in C_K1, or it can be provided that the electronic control device 6 starts from an increased cold demand in the next cooling cycle C_K2. The latter can be the case in particular when cooling cycles C_Kwhose duration was longer than the predefined running time K_valready exist before the cooling cycle C_K1.
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_vof the next cooling cycle C_K2, the next cooling cycle C_K2, which again is triggered by the switching signal, will be operated at an increased starting rotary speed v₄. The increased starting rotary speed v₄can, for example, correspond to the last rotary speed v of the preceding cooling cycle C_K1or can be calculated as the average value of the rotary speeds v₁, v₂, v₃of the preceding cooling cycle C_K1.
In the second cooling cycle C_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 t₆. The actual duration K₂of the second cooling cycle C_K2is, however, less than the predefined duration K_v, so that the actual cooling demand of the cooled volume 4 has already been satisfied before the predefined duration K_vis reached at time t₇. From this, the electronic control device 6 can infer that a lower cooling demand is necessary in the next cooling cycle C_K3.
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_vof the next cooling cycle C_K3, the third cooling cycle C_K3is started with a rotary speed v that is lower than the rotary speed v₄of the preceding cooling cycle C_K2, the lower rotary speed v in this embodiment example corresponding to the starting rotary speed v₁. In the third cooling cycle C_K3, the predefined duration K_vcorresponds with the duration K₃of the third cooling cycle C₃, so that the cooling demand of the cooled volume 4 is reached with the rotary speed v₁within the predefined duration K_v. In the third cooling cycle C_K3, an especially energy-conserving operation of the refrigerant compressor 2 is achieved.
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.
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 5 a 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 5 a. In this case, at least the refrigerant in the evaporator 5 a also becomes heated. The defrost operation is initiated in a rest cycle C_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.
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_K1, C_K2run according to the preset rotary speed control, as described above. For the sake of simplicity, the two cooling cycles C_K1, C_K2are shown as operating cycles in which the predefined duration K_vcorresponds to the actual duration K₁, K₂, and the refrigerant compressor 2 is operated at the rotary speed v₁. A defrost operation, indicated as DEFROST in the figure, is initiated during the third rest cycle C_R3, which follows the second cooling cycle C_K2.
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_K3is begun. Said cooling cycle starts with the starting rotary speed v₁. As soon as the running time exceeds the predefined duration K_v, the rotary speed v of the refrigerant compressor 2 is raised to the first increased rotary speed v₂. Since the actual duration of the third cooling cycle C_K3also exceeds the limit values of the predefined duration K_v1, K_v2, K_v3, the rotary speed v is increased stepwise to the increased rotary speeds v₃, v₄, and finally to a maximum rotary speed v_max. Only after the third limit value has exceeded the predefined duration K_v3is the maximum rotary speed v_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.
Another disadvantage is seen in the previously described setting of a starting rotary speed v_sfor the next cooling cycle C_K4in the third cooling cycle C_K3. Since the maximum rotary speed v_maxis reached and the predefined duration K_vis clearly exceeded by the current duration K₃of the third cooling cycle C_K3, the starting rotary speed v_sof the fourth cooling cycle C_K4is greatly increased over the starting rotary speed v₁of the third cooling cycle C_K3in accordance with the preset rotary speed control. While the increase of the starting rotary speed v_sof the next cooling cycle C_Kbecause 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.
According to the invention, therefore, at least one comparison parameter P_vis stored in the electronic control device 6 of the refrigerant compressor 2, and an exceeding or falling short of the comparison parameter P_vby a current parameter value P_ais 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_vof the rest cycle C_R. For this reason, monitoring to determine if the current duration P_aof the current rest cycle C_Rexceeds the comparison duration P_vis continuously carried out. As soon as an exceeding of the comparison duration P_vis detected, a cooling cycle C_Kwill be not be started upon reception of the switching signal triggered by the thermostat 3, but rather a special cooling cycle C_Dthat differs from the preset rotary speed control will be initiated.
Since the rotary speed behavior in the special cooling cycle C_Dis 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_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_Dis reduced by comparison with the duration of the cooling cycle C_K3conducted 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_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_D. In this example variation, the refrigerant compressor 2 is driven at the maximum rotary speed v_maxover the duration C_D1and then driven at the third elevated rotary speed v₄over the duration C_D2, before the refrigerant compressor 2 has been accelerated back to the maximum rotary speed v_max. Basically, any progressive, regressive, or stepwise paths of the speed curve during the special cooling cycle C_Dare conceivable.
In this embodiment example, the starting rotary speed v_sof the following third cooling cycle C_K3is not affected by the rotary speed behavior during the special cooling cycle C_D, rather, the refrigerant compressor 2 is operated in the following third cooling cycle C_K3at the rotary speed v₁specified for it in the second cooling cycle C_K2, since the special cooling cycle C_Dis not taken into consideration in establishing the starting rotary speed v_sof the following third cooling cycle C_K3.
FIG. 6 shows a second embodiment variation of the method according to the invention. While the duration of the rest cycle C_Rfunctioned as a comparison parameter P_vin the previously discussed embodiment example, in this embodiment example, an average load L_mof the refrigerant compressor 2 in a starting phase of the cooling cycle C_Kserves as the comparison parameter P_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_Kcontrolled by the preset rotary speed control is started. During the starting phase of the cooling cycle C_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_mis calculated over the duration of the starting phase of the cooling cycle C_K. This current average load L_mis, as the currently measured parameter value P_a, then compared with the comparison parameter P_vstored in the electronic control device 6 of the refrigerant compressor 2. Since the currently measured average load L_mexceeds the stored comparison parameter P_vbecause of the heating of the refrigerant in the evaporator 5 a 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_Kis interrupted after the end of the starting phase and the special cooling cycle C_Dis started. Since the load L can only be measured each time during the cooling cycle C_K, the special cooling cycle C_Dcannot 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_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.
FIG. 7 shows another aspect of the invention, in which, because of the monitoring of the comparison parameter P_vby 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_Dis 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_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_Dis 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_D.
Therefore, in the electronic control device 6, besides the power outage, the additional temperature T_wis employed as a currently measured parameter value P_a, wherein the additional temperature T_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_vis a comparison temperature T_v, with which the currently measured additional temperature T_wis compared.
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_wwith the comparison temperature T_v. During the normal operation, in which the electronic control device 6 and housing 8 become heated during the cooling cycle C_K, only a partial cooling takes place in the rest cycle C_Rbefore the next cooling cycle C_Kis initiated. If the currently measured additional temperature T_wtherefore is below the comparison temperature T_v, it can be inferred from this that a cooling cycle C_Khas 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_Khas taken place over an above-average period of time, the special cooling cycle C_Dwill 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.
For the sake of clarity, one is referred to the description of FIG. 5 for the details of the special cooling cycle C_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_Rand/or the average load L_mand/or the additional temperature T_w.
It can be provided in alternative embodiment variations of the invention that the additional temperature T_wfunctions as the currently measured parameter value P_aand the comparison parameter P_vis a comparison temperature T_v, and upon the detection of a deviation of the currently measured additional temperature T_wfrom the comparison temperature T_v, a special cooling cycle C_Dis 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_w, and the corresponding special cooling cycle C_Dcan be initiated. Likewise, it is conceivable that a special cooling cycle C_Dwill be initiated if the currently measured parameter P_ais not the additional temperature T_wand 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_ais the currently measured load L or the currently determined average load L_mand an exceeding or falling short of the comparison parameter P_vwas detected.
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_maxduring the special cooling cycle C_D, but rather at a percentage of said rotary speed, for example at 85% of the maximum rotary speed v_max. It can further be advantageous if the refrigerant compressor 2 does not exceed a predefined rotary speed v_Dduring the special cooling cycle C_D, wherein the predefined rotary speed v_Dis again defined as a percentage of the maximum rotary speed v_max, for example 75%. It is also advantageous if the refrigerant compressor 2 is operated at a high predefined rotary speed v_Dimmediately after the initiation of the special cooling cycle C_D, wherein the predefined v_Dis, for example, 92% of the maximum rotary speed v_max.
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_aare 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_Vis adjusted on the basis of the stored parameter values P_S. For instance, the comparison parameter P_Vcan, for example, be varied in dependence on an extreme value P_E, thus a minimum or maximum, of the stored parameter values P_Sor, for example, in dependence on an average value P_M. The comparison parameter P_Vcan correspond either directly to the extreme value P_Eor to the average value P_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_V, thus the extreme value P_Eor the average value P_Mis multiplied by the deviation factor in order to set the value of the comparison parameter P_V. If the stored parameter values P_Schange during operation, the comparison parameter P_Vwill be automatically adjusted.

REFERENCE NUMBERS

1 Refrigeration system
2 Refrigerant compressor
3 Thermostat
4 Cooled volume
5 Cooling line
- 5 a Evaporator
6 Electronic control device of refrigerant compressor 2
7 Temperature measuring device
8 Housing of refrigerant compressor 2
- 8 a Lower housing section
- 8 b Upper housing section
K_vPredefined parameter
K_aCurrent parameter
v Rotary speed
C_RRest cycle
C_KCooling cycle
C Operating cycle

Claims

What is claimed is:

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_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_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_K), a rest cycle (C_R) following the cooling cycle (C_K),

and where the rotary speed behavior of the refrigerator compressor is controlled during a cooling cycle (C_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_V) is stored in the electronic control device of the refrigerant compressor and an exceeding or falling short of the comparison parameter (P_V) by a currently measured parameter value (P_a) is monitored,

a special cooling cycle (C_D) that is different from the preset rotary speed control is initiated if the current measured parameter value (P_a) exceeds or falls short of the comparison parameter (P_V),

optionally, a current cooling cycle (C_K) that is controlled by the preset rotary speed control is interrupted by the special cooling cycle (C_D).

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

3. The method as in claim 2, wherein the load (L) is monitored as the average load (L_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_V) or one of the monitored comparison parameters (P_V) is a duration of the rest cycle (C_R).

5. The method as in claim 1, wherein

an additional temperature (T_w) that is independent of the temperature of the cooled volume is measured,

the currently measured parameter value (P_a) or one of the currently measured parameter values (P_a) is the additional temperature (T_w),

the at least one monitored comparison parameter (P_V) or one of the monitored comparison parameters (P_V) is a comparison temperature (T_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_D) is initiated if both an exceeding or falling short of the comparison parameter (P_V) by the currently measured parameter value (P_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_a) is stored in the electronic control device of the refrigerant compressor over at least two operating cycles (C) as stored parameter value (P_S).

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

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

10. The method as in claim 8, wherein the comparison parameter (P_V) is determined by multiplying the extreme value (P_E) or the average value (P_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_s) of the refrigerant compressor is established for the cooling cycle (C_K) following the special cooling cycle (C_C) [sic; C_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_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_K).

13. The method as in claim 1, wherein the refrigerant compressor is operated during the special cooling cycle (C_D) so that a defined rotary speed (v_c) is not exceeded before the end of the special cooling cycle (C_D), wherein the defined rotary speed (v_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_D) to a predefined rotary speed (v_c), wherein the at least one defined rotary speed (v_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_K) and to end a rest cycle (C_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_K) and to begin a rest cycle (C_R), and

to control the rotary speed behavior of the refrigerant compressor during a cooling cycle (C_K) by means of a preset rotary speed control stored in the electronic control device,

wherein

at least one comparison parameter (P_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_V) by a current measured parameter value (P_a),

to initiate a special cooling cycle (C_D) that is different from the preset rotary speed control if the current measured parameter value (P_a) exceeds or falls short of the comparison parameter (P_V),

optionally to interrupt a current cooling cycle ( ) [sic; (C_K)] controlled by the preset rotary speed control in order to start the special cooling cycle ( ) [sic; (C_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_v) and the currently measured parameter value (P_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_R) and that the stored comparison parameter (P_v) and the currently measured parameter value (P_a) are the duration of a rest cycle (C_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_w) that is independent of the temperature of the cooled volume,

and that the stored comparison parameter (P_v) is a comparison temperature (T_v) and the currently measured parameter value (P_a) is the additional temperature (T_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_D) if both an exceeding or falling short of the comparison parameter (P_V) by the currently measured parameter value (P_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_V) is determined in dependence on the extreme value (P_E), which corresponds to a maximum value of the extreme value (P_E).

25. The method as in claim 9, wherein the comparison parameter (P_V) is determined in dependence on the average value (P_M), which corresponds to the average value (P_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_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_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_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_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_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_c) is between 95% and 100% of a maximum rotary speed of the refrigerant compressor.

35. A module comprising

an electronic control device for control of the cyclic operation of the rotary speed-variable refrigerant compressor as in the method of claim 1.