REFRIGERANT COMPRESSOR SYSTEM

Description

[0001] The invention relates to a refrigerant compressor assembly for a refrigerant system, comprising at least two piston compressors operating in parallel between a common low-pressure connection and a common high-pressure connection, which can be operated individually and each have an electric motor and cylinder units driven by the latter.

[0002] The invention is based on the object of operating such a refrigerant compressor system under different requirements.

[0003] This object is achieved according to the invention in a refrigerant compressor network of the type described above in that in the refrigerant compressor network a total mass flow rate of the refrigerant compressor network which is variable in the range from a minimum mass flow rate to a maximum mass flow rate can be set in that in at least one of the piston compressors its mass flow rate can be set by selecting the speed using a frequency converter for the electric motor and in that in at least one of the piston compressors its mass flow rate can be set by selecting the cylinder and in that an operating state control is provided for the refrigerant compressor network which controls or regulates the total mass flow rate based on a power requirement signal of the refrigeration system transmitted thereto by specifying the cylinder selection and the speed selection.

[0004] The advantage of the solution according to the invention is that, due to the use of at least two piston compressors in the refrigerant compressor system, a great variability is possible with regard to providing a required total mass flow rate while at the same time achieving a high maximum mass flow rate through the use of at least two piston compressors due to the speed selection and the cylinder selection in these piston compressors.

[0005] The variability of the total mass flow rate can be optimally designed if the operating state control specifies at least one temporally constant, i.e. temporally unmodulated, cylinder selection for at least one piston compressor in order to achieve at least one total mass flow rate of the refrigerant compressor network.

[0006] A time-unmodulated cylinder selection means that for the respective piston compressor, a certain number of cylinders of the respective piston compressor are activated and the others are deactivated during the period during which a certain total mass flow rate of the refrigerant compressor system is to be achieved.

[0007] This ranges from activating all cylinders to deactivating all cylinders, which can also be achieved by switching off the respective piston compressor.

[0008] In addition or alternatively, the variability can be further improved if the operating state control specifies at least one time-modulated, i.e. time-varying, in particular pulse-width modulated or modulated according to WO 2017 / 129224 A1, cylinder selection in order to achieve the respective total mass flow rate of the refrigerant compressor network.

[0009] A time-modulated cylinder selection means that for the respective piston compressor, during the period during which a certain total mass flow rate of the refrigerant compressor system is to be achieved, a certain number of cylinders of the respective piston compressor are activated and deactivated in a time-varying manner in order to reduce the mass flow compressed by them in relation to the mass flow when they are permanently activated.

[0010] This can be a time-varying activation and deactivation of all cylinders of the respective piston compressor or only a subset of all cylinders.

[0011] Such a time-modulated cylinder selection makes it possible to vary and reduce the mass flow rate of this piston compressor to a very large extent and thus also to reduce the total mass flow rate of the refrigerant compressor system to the lowest possible values, especially when the non-time-modulated piston compressor is switched off.

[0012] Furthermore, it is preferably provided that the operating state control specifies a speed selection in order to achieve the respective total mass flow rate of the refrigerant compressor system.

[0013] In principle, the option of speed selection can be provided for each of the piston compressors in the refrigerant compressor system and can thus also be specified by the operating state control.

[0014] However, a particularly practical solution provides that a speed selection can only be specified for one piston compressor of the refrigerant compressor system.

[0015] A simple solution provides that the operating state control operates a first of the piston compressors with speed selection and a second of the piston compressors with cylinder selection in order to achieve the respective total mass flow rate.

[0016] In principle, the operating state control can only operate the second piston compressor with a time-constant speed selection.

[0017] It is even more advantageous, in particular in order to achieve the greatest possible variability with regard to a low total mass flow rate, if the operating state control operates the second piston compressor with time-modulated and / or time-unmodulated cylinder selection in order to achieve the respective total mass flow rate.

[0018] In this case, selected cylinders are operated in a time-modulated manner and the other cylinders are operated in a time-unmodulated manner, ie switched on or off.

[0019] This provides increased variability, particularly in combination with the first piston compressor operated with speed selection, in order to be able to optimize operation at the respective total mass flow rate.

[0020] Another advantageous solution provides that the operating state control operates a first of the piston compressors with speed selection and cylinder selection and a second of the piston compressors with cylinder selection in order to achieve the respective total mass flow rate.

[0021] In principle, it would be possible in this case to operate both piston compressors with time-unmodulated cylinder selection and / or time-modulated cylinder selection.

[0022] However, in order to structure the operating mode as simply as possible, an advantageous solution provides that the operating state control operates the first piston compressor and the second piston compressor with time-unmodulated cylinder selection and one of the piston compressors also with time-modulated cylinder selection in order to achieve the respective total mass flow rate.

[0023] In order to enable flexible operation, particularly at low total mass flow rates, it is provided that the operation of at least one of the piston compressors with speed selection includes both operation at zero speed and operation at a speed range suitable for the required mass flow rate, i.e. the piston compressor to be operated with speed selection can also be switched off.

[0024] Furthermore, in order to achieve the best possible variability, it is advantageous if the operation of at least one of the piston compressors, through cylinder selection, includes operation with all cylinder units, or a subset of all cylinder units, or operation with the cylinder units switched off or the electric motor switched off.

[0025] With regard to the operation of the refrigerant compressor system using operating state control, a wide variety of options are conceivable.

[0026] An advantageous solution provides that the operating state control operates only one of the piston compressors when the total mass flow rate is close to the minimum mass flow rate.

[0027] For example, this is achieved by the operating state control only operating the refrigerant compressor that can be operated with time-modulated cylinder selection at the lowest possible total mass flow rate.

[0028] In addition or alternatively, it is preferably provided in this case that the operating state control operates only the refrigerant compressor that can be operated with speed selection at a total mass flow rate close to the lowest possible total mass flow rate, in particular at the total mass flow rate following the lowest possible total mass flow rate.

[0029] Another advantageous solution provides that the operating state control operates only the piston compressor with speed selection and cylinder selection at the lowest total mass flow rate, whereby the cylinder selection can be, for example, a time-unmodulated cylinder selection or, for example, additionally combined with time-modulated cylinder selection.

[0030] In addition, the operating state control opens up the possibility of optimizing the speed selection and the cylinder selection with regard to the highest quality factor or COP and / or the lowest electrical power consumption at the respective total mass flow rate.

[0031] Another practical solution provides that the operating state control determines the quality factor or COP or the electrical power consumption for the possible operating modes in the case of several operating modes possible by selecting the speed and cylinder selection in order to achieve the respective total mass flow rate and selects the operating mode with the highest quality factor or COP or the lowest electrical power consumption.

[0032] The quality level or electrical power consumption can be determined in a variety of ways.

[0033] One possibility is that the operating state control has stored the data required to determine the quality level or the COP or the electrical power consumption for the respective speed selection and / or cylinder selection.

[0034] This data can be determined, for example, as part of a calibration operation of the refrigerant compressor system.

[0035] Another possibility is that the operating state control for determining the quality level or the COP or the electrical power consumption for the respective speed selection and / or cylinder selection determines and stores the data during initial operation and / or during ongoing operation of the refrigerant compressor system.

[0036] Another advantageous possibility is that the operating state control for determining the quality level or the COP or the electrical power consumption for the respective speed selection or cylinder selection determines these values ​​during the current operation of the refrigerant compressor network.

[0037] With regard to the way in which the optimal conditions are determined, an advantageous solution provides that the determination of the efficiency or COP or the electrical power consumption is carried out by the operating state control by detecting the low pressure and / or the high pressure of the refrigerant compressor network.

[0038] A further advantageous solution provides that the operating state control uses the refrigerant, the total mass flow rate, the electrical power consumption and / or the speed of the electric motors to determine the quality level or the COP or the electrical power consumption.

[0039] Another solution provides that the operating state control, in order to optimize the quality factor or COP or the electrical power consumption of the possible operating modes, including speed selection and cylinder selection, assigns all total mass flow rates that can be achieved by the refrigerant compressor network to different total mass flow ranges and assigns certain operating modes, including speed selection and cylinder selection, to each total mass flow range.

[0040] In the context of the previous explanation of the solution according to the invention, no further details were given as to how the activation and deactivation of each cylinder bank should take place.

[0041] An advantageous solution provides that the activation and deactivation of each cylinder bank is carried out by means of a mechanical power control unit controlled by the operating state control.

[0042] This means that, in particular, the operating state control controls the mechanical power control unit of each of the cylinder banks which is provided with such a mechanical power control unit.

[0043] In principle, the mechanical power control unit can be arranged at any location in the refrigerant compressor.

[0044] It is particularly advantageous if the mechanical power control unit is assigned to a cylinder head of the respective cylinder bank.

[0045] Furthermore, it is advantageously provided that the mechanical power control unit controls an inlet flow into the inlet chamber of the cylinder head to activate or deactivate the respective cylinder bank.

[0046] This means that the power control unit in particular interrupts the intake flow into the intake chamber and thus deactivates the respective cylinder bank or vice versa.

[0047] Another advantageous solution provides that the power control unit connects the exhaust chamber to the intake chamber for activating or deactivating the respective cylinder bank in the cylinder head.

[0048] This means that in this case, in particular, the power control unit short-circuits the outlet chamber and the inlet chamber, so that the drive of the cylinder bank is possible without torque fluctuations, a solution that is particularly suitable for CO2 as a refrigerant.

[0049] With regard to the operating state control, for example, it is intended that this can be a separate control from the frequency converter.

[0050] This means that, for example, when the frequency converter is integrated into the refrigerant compressor, the operating state control is arranged separately, for example on the refrigerant compressor or independently of it.

[0051] Alternatively, it is also possible for the operating state control to be arranged in a housing that houses the frequency converter, which in the simplest case is arranged on the compressor housing or in the compressor housing.

[0052] An advantageous design of the refrigerant compressor system provides that the cylinder banks of the piston compressors operate in parallel.

[0053] A favorable power output can be achieved particularly when the respective piston compressor has at least two cylinder units per cylinder bank.

[0054] The number of operating modes can be made as large as possible if the piston compressor has more than two cylinder banks.

[0055] Furthermore, the invention relates to a refrigeration system comprising a refrigerant compressor assembly, a high-pressure side heat exchanger, an expansion element, and a low-pressure side heat exchanger.

[0056] According to the invention, in such a refrigeration system, in order to optimize its operation, the refrigerant compressor assembly is designed according to one of the preceding embodiments.

[0057] Furthermore, it is preferably provided that the refrigeration system has a system control which generates the power request signal for the operating state control, for example depending on the goods to be cooled.

[0058] In this case, it is also possible for the operating state control to be located in a housing of the system control system.

[0059] Further features and advantages of the invention are the subject of the following description and the drawings of some embodiments.

[0060] The drawing shows: Fig. 1 is a schematic representation of a refrigeration system according to the invention with a refrigerant compressor assembly according to the invention; Fig. 2 is a cross-section along line 2-2 in Fig. 1 through a first piston compressor of the refrigerant compressor assembly of the refrigeration system according to the invention; Fig. 3 a longitudinal section along line 3-3 in Fig. 2 through the first reciprocating compressor; Fig. 4 a cross section along line 4-4 in Fig. 1 by a second piston compressor of the refrigerant system; Fig. 5 a longitudinal section along line 5-5 in Fig. 4 through the second piston compressor; Fig. 6 a section through a mechanical power control unit integrated into a cylinder head in the open position of a valve body of the mechanical power control unit; Fig. 7 a section similar Fig. 6 in a closed position of the valve body of the mechanical power control unit; Fig. 8 a schematic representation of a switching interval comprising an opening interval and a closing interval; Fig. 9 a schematic representation of the temperature behavior of the low-pressure side heat exchanger in the refrigeration system when the compression of refrigerant is interrupted; Fig. 10 a representation of the mass flow rate of the first piston compressor when speed is selected; Fig. 11 a representation of the mass flow rate of the second piston compressor when cylinder is selected; Fig. 12 a flow diagram illustrating the procedure according to the invention; Fig. 13 a representation of the total mass flow rate of the refrigerant compressor network according to Fig. 1 with different cylinder selection of the second piston compressor and speed selection of the first piston compressor; Fig. 14 a representation of a second embodiment of a refrigerant compressor combination; Fig. 15 a view of a piston compressor according to the third embodiment of a refrigerant compressor combination according to the invention; Fig. 16 a side view of a piston compressor of a fourth embodiment of a refrigerant compressor combination according to the invention; Fig. 17 a front view of the fourth embodiment of the refrigerant compressor combination according to the invention; Fig. 18 a half-offset section along line 18-18 in Fig. 16 ; Fig. 19 a longitudinal section through the piston compressor according to the third embodiment of the refrigerant compressor according to the invention; Fig. 20 a section along line 20-20 in Fig. 16 with an open connecting channel between inlet chamber and outlet chamber and Fig. 21 a section similar Fig. 20 with the connecting channel between the outlet chamber and the inlet chamber closed.

[0061] An embodiment of a refrigeration system according to the invention, designated as a whole by 10, comprises a refrigerant compressor assembly 12, from whose high-pressure connection 14 a high-pressure line 16 leads to a high-pressure side heat exchanger, designated as a whole by 18, in which the compressed refrigerant condenses by dissipating heat to a heat sink, for example circulated ambient air or other cooling media.

[0062] From the high-pressure side heat exchanger 18, liquid refrigerant flows to an expansion element 20 and from there to a low-pressure side heat exchanger 22.

[0063] For example, between the heat exchanger 18 and the expansion element 20 there is a collector 26 which is connected to the heat exchanger 18 by means of a line, in which the liquid refrigerant collects and from which it then flows via a line to the expansion element 20.

[0064] After flowing through the low-pressure side heat exchanger 32, the evaporated refrigerant flows via a line to a low-pressure connection 24 of the refrigerant compressor assembly 12.

[0065] The refrigerant compressor assembly 12 comprises at least two piston compressors 30 and 32 operating in parallel between the low-pressure connection 24 and the high-pressure connection 14, whose suction connections 34a and 34b are connected to the low-pressure connection 24 and whose pressure connections 36a, 36b are connected to the high-pressure connection 14.

[0066] As in Fig. 2 and 3As shown, the first piston compressor 30 comprises a compressor housing 40 in which, for example, two cylinder banks 42a and 42b arranged in a V-shape relative to one another and operating in parallel are provided, each of which comprises at least one, in particular two or more cylinder units 44.

[0067] Each of these cylinder units 44 is formed from a cylinder housing 46 in which a piston 48 is movable in an oscillating manner in that the piston 48 is driven by a connecting rod 50, which in turn is seated on an eccentric 52 of an eccentric shaft 54 ​​or is driven by a crankshaft, which is driven, for example, by an electric motor 60, which can be designed as a synchronous or asynchronous motor.

[0068] The cylinder housing 46 of each of the cylinder units 44 is closed by a valve plate 56, on which a cylinder head 58a, 58b is arranged for each of the cylinder banks 42a, 42b.

[0069] Preferably, the valve plate 56 covers not only one cylinder housing 46 of a cylinder unit 44, but all cylinder housings 46 of the respective cylinder bank 42a, 42b, and in the same way the cylinder head 58a, 58b also covers all cylinder housings 46 of the respective cylinder bank 42a, 42b.

[0070] In addition, a frequency converter 62 for speed-controlled or speed-regulated operation of the electric motor 60 is arranged on the compressor housing 40, which frequency converter operates the electric motor 60 with a voltage that varies according to a drive frequency, which leads to a speed that is substantially proportional to the drive frequency.

[0071] The compressor housing 40 further comprises an inlet channel 64 connected to the suction connection 34a, which is, for example, integrated in the compressor housing 40, and the pressure connection 36a.

[0072] Thus, the first piston compressor 30 can be operated by means of the frequency converter 62 in a speed selection mode with a predeterminable speed selection D, so that its mass flow rate from the suction connection 34a to the pressure connection 36a also varies according to the speed.

[0073] The second piston compressor 32 also has a compressor housing 40 with cylinder banks 42a and 42b, each of which also comprises at least one, in particular two or more cylinder units 44.

[0074] The cylinder units 44 are designed in the same way as in the first piston compressor 30, as shown in Fig. 4 shown, and also driven by an electric motor 60, as in Fig. 4 and 5 shown.

[0075] Furthermore, the cylinder units 44 are also closed off by a valve plate 56 and cylinder heads 58, as in the first piston compressor 30.

[0076] However, in the second piston compressor 32, the electric motor 60 cannot be operated by means of a frequency converter 62 but can only be operated at a constant speed.

[0077] As in Fig. 4 As shown in an enlarged manner, in the piston compressor 32, at least one cylinder bank 42, in particular each cylinder bank 42, is assigned a mechanical power control unit, designated as a whole by 70, which serves to allow an inlet flow 74 of refrigerant passing from the inlet channel 64 into the respective cylinder head 58, namely into an inlet chamber 72 thereof, through the valve plate 56, in order to thereby activate the respective cylinder bank 42, or to interrupt it, in order to thereby deactivate the respective cylinder bank 42, as in Fig. 6 und 7 shown.

[0078] If the mechanical power control unit 70 is open - as in Fig. 6 shown - the inlet flow 74 has the possibility of entering a cylinder chamber 80 delimited by the respective piston 48 and the respective cylinder housing 46 as well as the valve plate 56 via an inlet opening 76 provided in the valve plate 56 and an inlet valve 78 provided on the valve plate 56, in order to be compressed in this by the oscillating movement of the piston 48, so that an outlet flow 86 exits the cylinder chamber 80 via an outlet opening 82 and an outlet valve 84 and enters an outlet chamber 88 of the cylinder head 58.

[0079] The mechanical power control unit 70 is designed, for example, as a servo valve which is integrated in the respective cylinder head 58 and has a valve body 90 with which an inflow opening 92 of the inlet chamber 72 provided in the valve plate 56 can be closed.

[0080] The valve body 90 is further arranged on a switching piston 94, which is guided in a switching cylinder housing 96, so that the switching piston 94 can be moved in the direction of the valve plate 56 by a pressure present in a switching cylinder chamber 98 in order to close the inflow opening 92 in the same.

[0081] A switching cylinder unit 100 formed from the switching cylinder housing 96, the switching piston 94 and the switching cylinder chamber 98, which is integrated into the cylinder head 58, can be controlled via a control valve 110 which comprises an electromagnetically movable control piston 112 with which a control valve seat 114 can be closed, wherein the control piston 112 and the control valve seat 114 are provided to interrupt or release a connection between a high-pressure channel 116 leading to the outlet chamber 88 and a pressure supply channel 118 leading to the switching cylinder chamber 98 for the switching cylinder 100.

[0082] If the connection between the high-pressure channel 116 and the pressure supply channel 118 is released, the switching cylinder chamber 98 is under the high pressure prevailing in the outlet chamber 88 and consequently the switching piston 94 moves in the direction of the valve plate 56 and presses the valve body 90 against it in order to close the inlet opening 92 in the valve plate 56 ( Fig. 7 ).

[0083] In this case, the force acting on the switching piston 94 due to the high pressure in the switching cylinder chamber 98 is counteracted by the force of an elastic energy accumulator 120, which is supported on the switching cylinder housing 96 on the one hand and on the other hand acts on the switching piston 94 in such a way that the latter moves away from the valve plate 56 and thus moves the valve body 90 into a position that releases the inflow opening 92.

[0084] In particular, the switching piston 94 is provided with a pressure relief channel 122, which leads from an opening facing the switching cylinder chamber 98 to a Fig. 7 shown outlet opening 124, which opens into the inlet chamber 72 when the valve body 90 and the switching piston 94 are in the position closing the inlet opening 92. The pressure relief channel 124 causes the pressure in the switching cylinder chamber 98 to collapse quickly when the connection between the high-pressure channel 116 and the pressure supply channel 118 is interrupted, and thus the switching piston 94, under the action of the elastic energy accumulator 120, together with the valve body 90, to move into a position which releases the inlet opening 92 and is in Fig. 6 move to the position shown.

[0085] The respective mechanical power control unit 70 is provided by a Fig. 1 The operating state control 130 shown can be controlled in such a way that the mechanical power control unit 70 can be closed or opened by it in order to activate or deactivate the respective cylinder bank 42a, 42b and thus to operate the refrigerant compressor 12 with a cylinder selection Z defining the scope of the activation and deactivation of the cylinder banks 42.

[0086] In addition, the electric motor 60 of the first piston compressor 30 can also be controlled by the operating state control 130, in particular by controlling a frequency converter 62 of the electric motor 60, in order to be able to operate it at a variable speed according to the speed selection D and thereby achieve a defined mass flow rate.

[0087] In addition, the operating state control 130 detects the respective total mass flow rate of the refrigerant compressor assembly 12, for example by measuring the low pressure PN by means of a low-pressure sensor 134 arranged near or at the low-pressure connection 24 of the refrigerant compressor assembly 12 and a high pressure PH by means of a high-pressure sensor 136 arranged near or at the high-pressure connection 14.

[0088] Furthermore, the electrical power consumed by the electric motor 60 of the first piston compressor 30 can also be measured by means of the frequency converter 62.

[0089] In addition, a power request signal LA is transmitted to the operating state controller 130, which is generated, for example, by a higher-level system controller 138, which detects the cooling power requested at the low-pressure side heat exchanger 32 for cooling an object 146, for example a cooling chamber, for example by temperature sensors 142 and 144 assigned to the low-pressure side heat exchanger 32, which allow the temperatures of a medium 148 flowing through the low-pressure side heat exchanger 32 and the object 146, for example before and after the low-pressure side heat exchanger 32, to be detected and compared with a required temperature of the medium 146.

[0090] The operating state controller 130 is able to adapt the cooling capacity of the refrigeration system 10 to the cooling capacity required for cooling the object 146, specified by the power request signal LA, by adjusting the total mass flow rate on the one hand by means of cylinder selection Z of the second piston compressor 32, which in the first exemplary embodiment is operated at a constant speed, for example with a drive frequency of 50 Hz corresponding to the mains frequency, and on the other hand by means of speed selection D, that is to say by regulating the speed of the electric motor 60 of the first piston compressor 30 by means of the frequency converter 62.

[0091] As in Fig. 10 As shown, the electric motor 60 of the piston compressor 30 can be operated in a limited speed range, for example, predetermined by drive frequencies between 25 Hz and 70 Hz generated by the frequency converter 62, so that, as in Fig. 10 shown, the mass flow rate of the piston compressor 30 is variable by the speed selection D from approximately 30% of the maximum value up to the maximum value of 100%.

[0092] The mass flow rate of the second piston compressor 32 is controlled by the cylinder selection Z, Z' carried out by controlling the power control units 70.

[0093] The activation or deactivation of at least one of the cylinder banks 42a, 42b by the cylinder selection Z can be carried out in the piston compressor 32 with a temporally unmodulated cylinder selection unchanged over the entire period of the respective required mass flow rate, so that, for example, during a certain period, when the piston compressor 32 is operated with the cylinder selection Z1, i.e. with both cylinder banks 42a and 42b, the maximum mass flow rate of 100% of the piston compressor can be achieved, while with the cylinder selection Z2, i.e. when operating with only one of the cylinder banks 42a, 42b, a mass flow rate of 50% can be achieved, as in Fig. 11 shown.

[0094] Alternatively, with a time-modulated cylinder selection Z', it is also possible to activate or deactivate at least one cylinder bank 42a, 42b or both cylinder banks 42 in a time-modulated manner, i.e., for example, in a clocked manner, during the period of a required mass flow rate.

[0095] The mechanical power control unit 70 is, for example, designed for this purpose by the Fig. 1 The operating state control 130 shown can be controlled in such a way that, as shown in Fig. 8 shown, in continuously successive switching intervals SI, the mechanical power control unit 70 closes and opens, each of the switching intervals SI having an opening interval O in which the valve body 90 in its releasing position allows the inlet flow 74 to pass through the inlet opening 92 and activates the corresponding cylinder bank 42, as in Fig. 6 shown, as well as a closing interval S, in which the valve body 90, as shown in Fig. 7 shown, in its closing position blocks the flow of the inlet stream 74 through the inlet opening 92 and thus deactivates the corresponding cylinder bank 42.

[0096] Within the duration of the respective switching interval SI, the duration of the opening interval O and the closing interval S can now be variably adjusted relative to each other, so that either the opening interval O is longer than the closing interval or vice versa.

[0097] In the extreme case, the opening interval O can extend essentially over the entire duration of the switching interval SI, while the closing interval S becomes arbitrarily small, or conversely, the closing interval S can extend essentially over the entire duration of the switching interval SI, so that the opening interval O becomes arbitrarily small.

[0098] Since in the refrigeration system 10 according to the invention, liquid refrigerant is generally constantly evaporated via the expansion valve 20, an interruption or strong variation in the compression of refrigerant by the refrigerant compressor assembly 12 would lead to an increase in the temperature T in the low-pressure side heat exchanger 22.

[0099] However, the system is provided with a reaction inertia, so that in case of an interruption or a strong variation in the extraction of refrigerant from the low-pressure side heat exchanger 22, the temperature T of the low-pressure side heat exchanger 32 does not rise immediately, but, as in Fig. 9 shown, a time period Z is required to increase by a value SA.

[0100] As long as the value SA is less than 10% of an output temperature TA of the low-pressure side heat exchanger, these fluctuations are irrelevant for the function of the refrigeration system according to the invention.

[0101] For this reason, the switching interval SI is selected such that it is shorter than the time period tA which elapses until the temperature T of the low-pressure side heat exchanger 32, starting from a temperature TA, of the low-pressure side heat exchanger 32 has risen by a value SA of approximately 10%, more preferably approximately 5%, when there is a sudden interruption in the extraction of refrigerant from the low-pressure side heat exchanger 32 and the supply of medium under high pressure at the high-pressure connection 14.

[0102] This ensures that the opening intervals 0 and the closing intervals S within the respective switching interval SI have an insignificant effect on the function of the refrigeration system and only lead to minor temperature fluctuations of the low-pressure side heat exchanger 32 of the refrigeration system according to the invention.

[0103] Typically, the durations of the switching intervals SI are shorter than approximately 10 seconds, and even better, shorter than approximately 5 seconds.

[0104] On the other hand, in order to ensure sufficient opening intervals O, the switching intervals are longer than approximately 1 second, even better longer than 2 seconds.

[0105] A preferred operating range provides switching intervals SI with a duration between 2 and 10 seconds.

[0106] In order to ensure such short switching intervals SI, it is preferably provided that the switching pistons 94 together with the valve body 90 and the elastic energy accumulators 120 have a natural frequency that is higher than the frequency corresponding to the maximum switching intervals SI, so that the switching pistons 94 are able to realize the opening intervals O and the closing intervals S within the switching intervals SI essentially without delay.

[0107] Preferably, the natural frequencies of the systems comprising switching piston 94, valve body 90 and elastic energy accumulator 120 are higher by a factor of at least 5 or, even better, at least 10 than the frequencies corresponding to the switching intervals SI.

[0108] Alternatively, it is also possible to activate or deactivate one or both cylinder banks 42a according to WO 2017 / 129224 A1 using the operating state control.

[0109] By means of time-modulated cylinder selection Z', the piston compressor 32 can be operated, for example with cylinder selection Z2', with only one modulated cylinder bank 42a, while the other cylinder bank 42b is switched off. This allows, for example, the mass flow rate to be variably adjusted from 50% to 10% of the maximum mass flow rate of the piston compressor 32, depending on how the duration of the opening interval 0 is selected relative to the closing interval S ( Fig. 11 ).

[0110] Based on the first exemplary embodiment of the refrigerant compressor combination according to the invention with the first piston compressor 30 and the second piston compressor 32, and assuming that with the first piston compressor 30 with speed selection D, a maximum of approximately 60% of the maximum mass flow rate of the refrigerant compressor combination 12 can be achieved, and with the second piston compressor 32 at a constant speed, for example at the drive frequency of 50 Hz corresponding to the mains frequency, a maximum of approximately 40% of the maximum mass flow rate of the refrigerant compressor combination 12 can be achieved, the following operating modes are possible: In order to set the smallest possible total mass flow rate of the refrigerant compressor system, the first piston compressor 30 is switched off and the second piston compressor 32 is operated at a constant speed, for example at a drive frequency corresponding to the mains frequency, with the cylinder selection Z2', so that the total mass flow rate can be varied from approximately 5% to approximately 20% based on the maximum mass flow rate of the refrigerant compressor system 12, so that a quasi-continuous variation of the total mass flow rate in this range is possible with the second piston compressor 32 as the lead compressor.If the first piston compressor 30 is operated with speed selection D, a total mass flow rate of approximately 18% to approximately 60% of the maximum mass flow rate of the refrigerant compressor network 12 can be variably set with the second piston compressor 32 switched off, with the first piston compressor 30 operating as the lead compressor. If the first piston compressor 30 and the second piston compressor 32 are operated together, a total mass flow rate of approximately 38% to approximately 100% of the maximum mass flow rate of the refrigerant compressor network 12 can be variably set with them, depending on the speed selection D of the first piston compressor 30 and cylinder selection Z or Z' of the second piston compressor 32, with the first piston compressor 30 operating as the lead compressor in these cases.

[0111] In the simplest case, the operating state control 130 operates the refrigerant compressor network 12 at a total mass flow rate of approximately 5% to 15% or more, with a maximum of approximately 20%, with the second piston compressor 32 at a constant speed and cylinder selection Z2' as the lead compressor and the first refrigerant compressor 30 switched off.

[0112] Thereafter, the second refrigerant compressor 32 is switched off and the first refrigerant compressor 30 is switched on as the lead compressor at a total mass flow rate starting at approximately 15% or at the latest at approximately 20% up to a total mass flow rate between 38% and 60% of the maximum mass flow rate of the refrigerant compressor system 12.

[0113] Starting from a range between 38% and 60% of the total mass flow rate, both piston compressors 30 and 32 are operated with the combination of speed selection D for the first piston compressor 30 as the lead compressor and cylinder selection Z, Z' for the second piston compressor 32 at a constant speed, initially with cylinder selection Z2 until approximately 60% of the maximum mass flow rate of the refrigerant compressor assembly 12 is reached and then with a cylinder selection Z1, ie use of all cylinder banks 42a, b of the second piston compressor 32 at a constant speed until the total mass flow rate of 100% of the maximum mass flow rate of the refrigerant compressor assembly 12 is reached, wherein in this case the first and second piston compressors 30, 32 each generate their maximum mass flow rate of 50% of the maximum mass flow rate of the refrigerant compressor assembly 12.

[0114] In a further embodiment, the operating state controller 130 is capable of detecting or recording the performance factor or COP of the refrigerant compressor network 12 as a function of the respective cylinder selection Z or Z' for the second piston compressor 32 and the speed selection D for the first piston compressor 30 at the respective total mass flow rate, wherein the performance factor or COP is dependent in particular on the refrigerant used, the speed of the electric motors 60 of the piston compressors 30 and 32, the number of active cylinder banks 42 and the ratio of high pressure PH to suction pressure PS.

[0115] The performance factor or COP is calculated in the case of an exact calculation, for example according to the publication: Compressors and condensing units for refrigeration - Performance testing and test methods - Part 1, Refrigerant compressors, in particular Chapter 4.1.5.2 and, for example, Equation 7, by European Standard, CEN / TC 113, Date 2014-04, prEN 13 771-1:2014.

[0116] Alternatively or additionally, the operating state control 130 is also capable of detecting the electrical power consumption of the compressor network 12 as a function of the respective cylinder selection Z or Z' for the piston compressor 32 and the speed selection D for the piston compressor 30 in the respective operating state.

[0117] By means of the operating state control 130, it is thus possible for the refrigerant compressor network 12, in a case in which several options for the cylinder selection Z or Z' of the piston compressor 32 and the speed selection D of the piston compressor 30 are available to realize a total mass flow rate required by the power request signal LA, to optimize the operation of the refrigerant compressor network 12 with regard to the greatest possible efficiency, which is expressed in the highest possible quality factor or COP or the lowest possible electrical power consumption of the electric motor 60, at the respective total mass flow rates, namely by suitable cylinder selection Z or Z' and speed selection D in order to carry out the operation at the required total mass flow rate.

[0118] This consideration or determination of the quality level or COP or the electrical power consumption for the respective total mass flow rate can be carried out in advance or during ongoing operation of the refrigerant compressor system 12 by querying data previously determined during test runs and stored in the operating state control 130.

[0119] For this purpose, the respective possible operating modes, comprising cylinder selection Z or Z' and speed selection D, are determined for the respective total mass flow rate, and a quality level or COP or an electrical power consumption is assigned to each of these, so that the operating state control 130 can select the cylinder selection Z or Z' and speed selection D with the respectively most favorable quality level or COP for the total mass flow rate required by the power request signal LA and can operate the refrigerant compressor network 12 accordingly.

[0120] A further possibility provides for operating the refrigerant compressor network 12 at the respective total mass flow rate and recording the power consumed by the electric motors 60 of the piston compressors 30 and 32 at each total mass flow rate, so that the operating state control 130 can then evaluate the cylinder selection Z or Z' and speed selection D with the lowest electrical power consumption with the greatest efficiency, save it, and in the future use only this cylinder selection Z or Z' and speed selection D as the one with the greatest efficiency for this total mass flow rate.

[0121] The procedure for selecting the possible operating mode B by the operating state control 130 is described in Fig. 12 shown.

[0122] First, when a power request LA is received by the operating state control 130, it is checked whether only one operating mode, i.e. only one cylinder selection Z or Z' and speed selection D, or several operating modes, i.e. several cylinder selections Z or Z' and speed selections D, are available to realize this power request LA.

[0123] As a rule, with a total mass flow rate that is close to the maximum output of the refrigerant compressor system 12, only one cylinder selection Z and speed selection D is available, namely a cylinder selection in which all cylinder banks 42 of the piston compressor 32 are fully activated and the adjustment to the total mass flow rate is carried out by controlling the speed of the drive motor 60 of the piston compressor 30.

[0124] For total mass flow rates in the medium or low range, there are generally several operating modes to choose from, i.e. cylinder selections Z or Z' and speed selections D, depending on how many cylinder banks 42 are present and whether the refrigerant compressor system 12 can be operated with unmodulated or time-modulated cylinder selections Z or Z'.

[0125] For these cylinder selections Z or Z' of the piston compressor 32, the determination of the

[0126] To achieve the required total mass flow rate, the required speed selection D of the electric motor 60 of the piston compressor 30 is required, and based on this, the quality level or the COP or the electrical power consumption is then taken into account or determined for the respective operating mode in the manner described above.

[0127] With the performance level or COP or the electrical power consumption assigned to the respective operating mode, comprising a cylinder selection Z or Z' and speed selection D, it is possible to select the operating mode with the best performance level or COP or the lowest electrical power consumption, which is then used by the operating state controller 130 to operate the refrigerant compressor network 12 in order to realize the total mass flow rate required by the power request signal LA.

[0128] The general procedure explained above can be explained below using a simple example of the first embodiment of the refrigerant compressor assembly 12 described at the beginning according to Fig. 1 using a simplified procedure for determining the performance factor or COP or the electrical power consumption.

[0129] In the refrigerant compressor network 12, which according to the first embodiment has two cylinder banks 42a and 42b per piston compressor 30, 32, there is only the possibility for the total mass flow rate when the second piston compressor 32 is limited to operation at a constant speed and the unmodulated cylinder selection Z, to operate it with a first cylinder selection Z1, in which both cylinder banks 42a and 42b are active, or to operate it with a second cylinder selection Z2, in which only one of the cylinder banks 42a, 42b is active and the other is inactive, wherein the contribution of such cylinder selections Z1, Z2 to the total mass flow rate in Fig. 13 is shown.

[0130] For each unmodulated cylinder selection Z1 and Z2 of the second piston compressor 32, it is possible to vary the speed of the electric motor 60 of the first piston compressor 30 by means of the frequency converter 62 by means of speed selection D, for example by varying the drive frequency of the frequency converter 62 between 25 Hz and 70 Hz, whereby the contribution of the piston compressor 30 to the total mass flow rate at the respective speed selection D is also Fig. 13 is shown.

[0131] Since all cylinder banks 42a, 42b must be active for a total mass flow rate above 80%, these can only be achieved by means of cylinder selection Z1, and a total mass flow rate below 80% can also be achieved by deactivating one of the cylinder banks 42a, 42b and thus by means of cylinder selection Z2, so that for total mass flow rates between 65% and 80%, optimization is possible by taking into account the quality factor or COP or the electrical power consumption, since the piston compressor 32 of the refrigerant compressor network 12 can be operated with either the first cylinder selection Z1 or the second cylinder selection Z2 for total mass flow rates between 65% and 80%.

[0132] The selection between the time-unmodulated first cylinder selection Z1 and the time-unmodulated second cylinder selection Z2 is therefore possible by determining the performance factor or COP or the electrical power consumption, whereby the piston compressor 30 can be operated with the appropriate speed selection D.

[0133] In order to be able to carry out a simplified consideration of the quality factor or COP or the electrical power consumption, for example, the possible power states between 65% and 80% are divided into two groups, for example in the simplest case depending on the high pressure PH detected by the high pressure sensor 136.

[0134] For example, if the high pressure PH for a certain refrigerant is above a high pressure limit PHG, the time-unmodulated cylinder selection Z2 is selected; if the high pressure PH is below the limit PHG, the time-unmodulated cylinder selection Z1 is selected.

[0135] A similar consideration of the performance factor or COP or the electrical power consumption is possible at a total mass flow rate between approximately 40% and approximately 60% of the maximum mass flow rate, namely either by operating the first piston compressor 30 with speed selection D and a speed of the electric motor 60 that can be predetermined by a drive frequency between approximately 50 Hz and approximately 70 Hz and the second piston compressor 32 switched off, or by operating the first refrigerant compressor 30 with speed selection D and a drive frequency between approximately 25 Hz and approximately 45 Hz and combined with the second piston compressor 32 at a constant speed and the unmodulated cylinder selection Z2.

[0136] For the unmodulated cylinder selections Z1 and Z2, the corresponding cylinder bank is activated or deactivated at a constant time during the entire time during which a total mass flow rate is realized.

[0137] However, due to the fact that time-modulated cylinder selections Z' can also be realized, in which an activation or deactivation of the respective cylinder bank 42 can take place proportionally during successive switching intervals SI, the first embodiment of the refrigerant compressor network according to the invention offers the possibility, for example, when selecting only one of the cylinder banks 42 and by synchronizing the activation and deactivation of this one cylinder bank 42 within the switching intervals SI, as well as continuous deactivation of the other cylinder bank 42, to select a cylinder selection Z2' of the second piston compressor 32 operated at a constant speed, in which even lower power states are possible, wherein then, for example, in a total mass flow rate between 5% and 25%, it is possibleto optimise the operation of the refrigerant compressor network 12 also with regard to the performance level or COP or the electrical power consumption by selecting between cylinder selection Z2 or the time-modulated cylinder selection Z2' with variations in the time modulation (, Fig. 13 ).

[0138] In addition, there is the possibility of optimization between the total mass flow rate of 25% and 80% by varying the temporal modulation of the cylinder selection Z2' of the second piston compressor 32 operated at constant speed when combined with the first piston compressor operated with speed selection D.

[0139] In simplified terms, cylinder selection Z2' can also be selected for a high pressure PH that is above the high pressure limit PHG, while cylinder selection Z2 is selected for a high pressure PH that is below the limit PHG.

[0140] However, these conditions can also be reversed depending on the refrigerant used.

[0141] In a second embodiment of a refrigeration system according to the invention, shown in Fig. 14 , those elements which are identical to those of the first embodiment are provided with the same reference numerals, so that with regard to the description thereof, reference can be made to the explanations of the first embodiment.

[0142] In contrast to the first embodiment, in the second embodiment the compressor assembly 12' is formed from the piston compressor 30' and the piston compressor 32, which is identical to the first piston compressor.

[0143] In contrast to the first embodiment, the piston compressor 30' is not only provided with the frequency converter 62, but, as shown in the Fig. 4 As shown, both cylinder banks 42a and 42b are each provided with a mechanical power control unit designated as a whole by 70, so that the respective cylinder bank 42a and 42b can be switched off, as explained in connection with the piston compressor 32 of the first embodiment.

[0144] Thus, in the compressor combination 12' of the second embodiment, it is possible to operate each of the piston compressors 30' and 32 with a cylinder selection Z1 or Z2 or Z2' and additionally to operate the piston compressor 30' with the aid of the frequency converter 62 with speed selection D, which has a multiplicative effect on the cylinder selection Z1, Z2 or Z2' of the piston compressor 30'.

[0145] Thus, in the second exemplary embodiment, it is possible to adjust the total mass flow rate by, on the one hand, adjusting the mass flow rate for the second piston compressor 32 operating at a fixed speed by selecting the cylinder Z1, Z2, or Z2', in the same way as described in connection with the first exemplary embodiment. In addition, however, in the second exemplary embodiment, for the first piston compressor 30', not only the speed selection is decisive for the total mass flow rate, but also the cylinder selection Z1, Z2, or Z2'. Thus, in the second exemplary embodiment of the refrigerant compressor network according to the invention, there are even more options for optimizing the total mass flow rate required by the power request signal LA with regard to the refrigerant output with regard to the COP or the electrical power consumption.

[0146] According to a third embodiment of a refrigerant compressor assembly 12, for example, both piston compressors 30 and 32 or only one of them are provided with three cylinder banks 42a, 42b and 42c ( Fig. 15 ), for example with two cylinders per cylinder bank 42, wherein each of the cylinder banks 42a, 42b, and 42c can be activated or deactivated individually by means of an associated mechanical power control unit 70, three cylinder selections Z1, Z2, Z3 are possible, namely the first cylinder selection Z1 with all cylinder banks 42a, 42b and 42c in the activated state, a second cylinder selection Z2 with two of the cylinder banks 42 in the activated state and a third cylinder selection Z3 with only one of the cylinder banks 42 in the activated state.

[0147] In terms of the detailed structure, the third embodiment corresponds to the first embodiment.

[0148] This opens up a wide range of possibilities for realising the total mass flow rate required by the power requirement LA.

[0149] If, for example, only the second piston compressor 32 is provided with three switchable cylinder banks 42a, 42b and 42c, this already opens up the possibility, with an unmodulated cylinder selection Z, of varying the mass flow rate of this piston compressor 32 between 33%, 66% and 100% of the possible mass flow rate thereof and of supplementing the mass flow rate of the first piston compressor 30 accordingly.

[0150] In the simplest case, the first piston compressor 30 may not have any switchable cylinder banks 42 and thus only generate a variable refrigerant output by selecting the speed, which can be varied, for example, between approximately 50 and 100% of the refrigerant output thereof.

[0151] However, if the first piston compressor 30 is also provided with three cylinder banks 42a, 42b and 42c which can each be switched on and off, its mass flow rate can be adjusted between a maximum of 33%, a maximum of 66% and a maximum of 100% by means of the cylinder selection Z alone, and in addition, by reducing the speed due to the speed selection D for each cylinder selection, its mass flow rate can be reduced by 70%, i.e. a minimum mass flow rate of approximately 11% with one cylinder bank, approximately 22% with two cylinder banks and a minimum of 33% with three switched-on cylinder banks.

[0152] Likewise, additional variations can be achieved by a time-modulated cylinder selection Z'.

[0153] A fourth embodiment of a refrigerant compressor system, which is particularly suitable for CO2 as a refrigerant, comprises piston compressors 30" and 32", each with a suction connection 34" and a pressure connection 14".

[0154] As in Fig. 16 bis 21 As shown, the respective piston compressor comprises a compressor housing 40", in which, for example, two V-shaped, parallel-operating cylinder banks 42"a and 42"b are provided, each of which comprises at least one, in particular two or more cylinder units 44".

[0155] Each of these cylinder units 44" is formed from a cylinder housing 46", in which a piston 48" is movable in an oscillating manner in that the piston 48" is driven by a connecting rod 50", which in turn is seated on an eccentric 52" of an eccentric shaft 54", which is driven, for example, by an electric motor 60", which can be designed as a synchronous or asynchronous motor.

[0156] The cylinder housing 46" of each of the cylinder units 44" is closed by a valve plate 56" on which a cylinder head 58" is arranged.

[0157] Preferably, the valve plate 56" covers not only one cylinder housing 46" of a cylinder bank 42", but all cylinder housings 46" of the respective cylinder bank 42", and in the same way, the cylinder head 58" also covers all cylinder housings 46" of the respective cylinder bank 42".

[0158] The compressor housing 40" further comprises an inlet channel 62" which is connected to the low-pressure connection 36" and is, for example, integrated in the compressor housing 40".

[0159] In each of the cylinder heads 42"a and 42"b, as shown in the Fig. 20 and 21 As shown, an inlet chamber 162 and an outlet chamber 164 are arranged, which are assigned to the two cylinder units 44" of the respective cylinder bank 42".

[0160] In particular, the inlet chamber 162 is located above inlet openings 172 of the cylinder units 44" of the cylinder bank 42".

[0161] Furthermore, the outlet chamber 164 is located above outlet openings 174 of the cylinder units 44" arranged in the valve plate 56", which are provided with outlet valves 176 seated on the valve plate 56", and in particular is directly adjacent to these.

[0162] As in Fig. 20 and 21As shown, each cylinder head 42" comprises an outer body 182 which engages over the respective valve plate 56" and encloses the inlet chamber 162 and the outlet chamber 164, which in turn are separated from one another by a separating body 184 running within the outer body 182, wherein the separating body 184 rises from the respective valve plate 56" and extends over and across the inlet chamber 162.

[0163] Thus, the outlet chamber 164 is located in the region of the valve plate 56" laterally next to the inlet chamber 162 and extends between the outer body 182 and the separating body 184, at least in part, above the inlet chamber 162.

[0164] For the operating state control of the total mass flow rate of the refrigerant compressor system, each cylinder head 58" is assigned the mechanical power control unit 70" which is actively controlled by the operating state control 130 and with which a connecting channel 192 between the outlet chamber 164 and the inlet chamber 162 can be closed or opened, wherein the cylinder units 44" assigned to the cylinder head 58" when the connecting channel 192 is closed ( Fig. 21 ) compress refrigerant at full power and do not compress refrigerant when the connecting channel 192 is open, since the refrigerant flows back from the outlet chamber 164 into the inlet chamber 162.

[0165] The connecting channel 192 runs through an insert part 194 inserted into the separating body 184, which insert part forms a sealing seat 196 facing the outlet chamber 164 and which adjoins a part of the outlet chamber 164 surrounding the sealing seat 196 and adjoining it.

[0166] Furthermore, the sealing seat 196 faces a closure piston 202, which can be placed onto the sealing seat 196, for example with a metallic sealing region 204, in order to tightly close the connecting channel 192 and which can be lifted away from the sealing seat 196 to such an extent that the sealing region 204 is spaced from the sealing seat 196 and thus refrigerant can flow from the outlet chamber 164 into the inlet chamber 162.

[0167] Preferably, the closure piston 202 is guided coaxially to the insert part 194 with the sealing seat 196 and sealed by means of a piston ring 206 in a guide bore 208 which is formed by a guide sleeve body 212 of the cylinder head 58" which is integrally formed on the outer body 182.

[0168] Preferably, the closure piston 202 itself or at least the sealing region 204 is made of a metal, for example a non-ferrous metal, which has a lower hardness than the metal of the sealing seat 196, which is made of steel, in particular hardened steel, for example.

[0169] In order to enable a rapid movement of the closure piston 202, in particular a stroke of the closure piston 202 between a closed position and an open position lies in the range between a quarter and half of an average diameter of the connecting channel 192.

[0170] The closure piston 202 delimits a pressure chamber 214, which is arranged on a side of the closure piston 202 facing away from the sealing area 204 and is closed on a side opposite the closure piston 202 by a closing body 216.

[0171] The volume of the pressure chamber 216 is in particular so small that in the open position of the closure piston it is less than one third, preferably less than one quarter, even better less than one fifth, advantageously less than one sixth and even more advantageously less than one eighth of the maximum volume of the pressure chamber 216 in the closed position of the closure piston 202.

[0172] Furthermore, a compression spring 218 is arranged in the pressure chamber 216, which on the one hand is supported on the closing body 216 and on the other hand acts on the closing piston 202 in the direction of its closing position resting on the sealing seat 196.

[0173] Depending on the pressure applied to the pressure chamber 216, the closure piston 202 is in its Fig. 20 shown open position or in its Fig. 21 shown locking position movable.

[0174] For this purpose, the closure piston 202 is penetrated by a throttle channel 222 which extends from the pressure chamber 214 through the closure piston 202 to an orifice opening which is arranged radially outside the sealing area on a side facing the sealing seat 196, but because it lies radially outside the sealing area 204, in the closed position of the closure piston 202, allows the entry of refrigerant which is under pressure in the outlet chamber 164 and flows around the sealing seat 196 and supplies this in a throttled manner to the pressure chamber 214.

[0175] In addition, a relief channel 224 leads into the pressure chamber 214, for example through the closing body 216, which can be connected by a solenoid valve designated as a whole by 226 to a pressure relief channel 228 which is connected to the inlet chamber 162.

[0176] For example, the solenoid valve 226 is designed to have a valve body 232 with which the connection between the pressure relief channel 228 and the relief channel 224 can be interrupted or established.

[0177] If the connection between the relief channel 224 and the pressure relief channel 228 is established, the suction pressure predominates in the pressure chamber 214, while the closure piston 202 is acted upon by the pressure in the outlet chamber 164 on its side facing the outlet chamber 164 and is thus moved into its open position.

[0178] However, if the connection between the pressure relief channel 228 and the relief channel 224 is interrupted by the valve body 232, the compression spring 218 presses the closure piston 202 onto the sealing seat 196 and, in addition, high pressure flows through the throttle channel 222 into the pressure chamber 214, so that high pressure builds up in the pressure chamber 214, which, in addition to the effect of the compression spring 218, presses the closure piston 202 with the sealing element 204 onto the sealing seat 196.

[0179] In particular, the closure piston 202 is designed in such a way that it extends radially beyond the sealing seat 196, so that even when the closure piston 202 is in the closed position, the piston surface located radially outside the sealing seat 196 and subjected to high pressure causes the closure piston 202 to move into the open position, shown in Fig. 20 is moved, provided that the valve body 232 of the solenoid valve 226 establishes the connection between the relief channel 224 and the pressure relief channel 228, which leads to a suction pressure being established in the pressure chamber 214.

[0180] The supply of refrigerant under suction pressure takes place via a supply channel 64" formed in the compressor housing 40", which leads to an inlet opening leading to the valve plate 56", through which refrigerant under suction pressure flows to a passage opening 236 in the valve plate 56" and passes through this into the inlet chamber 162.

[0181] In addition, as in Fig. 20 and 21 shown, the outlet chamber 164 leads to an outlet opening 242 arranged in the valve plate 56" through which the refrigerant under pressure in the outlet chamber 164 passes into an outlet channel 244 provided in the compressor housing and can flow to the high-pressure connection 16".

[0182] In particular, the outlet opening 242 of the valve plate 56" is assigned a check valve 246, which is held on the valve plate 56" and ensures that in the case of the open position of the closure piston 202 and thus in the case of an overflow of the refrigerant from the outlet chamber 164 into the inlet chamber 162, the pressure in the outlet channel 244 does not drop, but is maintained by the closing check valve 246.

[0183] The fourth embodiment of the refrigerant compressor assembly 12" can be operated in the same way as the first or second or third embodiment, so that with regard to the operation of the same with the cylinder selection Z and speed selection D, reference can be made in full to the explanations of the preceding embodiments.

[0184] In all embodiments of a compressor combination according to the invention, in addition to the two piston compressors 30, 32, further piston compressors can be provided, which can be additionally used by the operating state control, preferably without cylinder selection Z and without speed selection D.

Claims

1. A refrigerant compressor group (12) for a refrigeration system (10), comprising at least two piston compressors (30, 32) that operate in parallel between a common low-pressure connector (24) and a common high-pressure connector (14), are operable individually and each have an electric motor (60) and cylinder units (44) that are driven by this, characterised in that, in the refrigerant compressor group (12), an overall mass flow throughput in the refrigerant compressor group (12) that is variable within the range from a minimum mass flow throughput to a maximum mass flow throughput is adjustable in that, in the case of at least one of the piston compressors (30), its mass flow throughput is adjustable by speed selection (D) with the aid of a frequency converter (62) for the electric motor (60), and in that, in the case of at least one of the piston compressors (30, 32), its mass flow throughput is adjustable by cylinder selection (Z), and in that an operating condition controller (130) for the refrigerant compressor group (12) is provided which, on the basis of a performance request signal (LA) of the refrigeration system (10) that is transmitted to the operating condition controller (130), controls the overall mass flow throughput by open or closed-loop control by predetermining the cylinder selection (Z) and the speed selection (D).

2. A refrigerant compressor group according to Claim 1, characterised in that, for the purpose of achieving at least one overall mass flow throughput in the refrigerant compressor group (12), in at least one piston compressor (30, 32) the operating condition controller (130) predetermines at least one cylinder selection (Z) that is constant over time, and / or in that, for the purpose of achieving the respective overall mass flow throughput in the refrigerant compressor group (12), the operating condition controller (130) predetermines at least one time-modulated cylinder selection (Z'), and / or in that, for the purpose of achieving the respective overall mass flow throughput in the refrigerant compressor group (12), the operating condition controller (130) predetermines a speed selection (D).

3. A refrigerant compressor group according to one of the preceding claims, characterised in that, for the purpose of achieving the respective overall mass flow throughput, the operating condition controller (130) operates a first one of the piston compressors (30) with speed selection (D) and a second one of the piston compressors (32) with cylinder selection (Z) and / or in that in particular, for the purpose of achieving the respective overall mass flow throughput, the operating condition controller (130) operates the second of the piston compressors with cylinder selection (Z, Z') that is time-modulated and / or not time-modulated.

4. A refrigerant compressor group according to one of the preceding claims, characterised in that, for the purpose of achieving the respective overall mass flow throughput, the operating condition controller (130) operates a first one of the piston compressors (30) with speed selection (D) and cylinder selection (Z), and a second one of the piston compressors (32) with cylinder selection (Z), and / or in that in particular, for the purpose of achieving the respective overall mass flow throughput, the operating condition controller (130) operates the first piston compressor (30) and the second piston compressor (32) with cylinder selection (Z) that is not time-modulated, and also operates one of the piston compressors (30, 32) with cylinder selection (Z') that is time-modulated.

5. A refrigerant compressor group according to one of the preceding claims, characterised in that operation of at least one of the piston compressors (30, 32) with speed selection (D) comprises both operation at a speed of zero and also operation in a speed range (D) that is suitable for the required mass flow throughput.

6. A refrigerant compressor group according to one of the preceding claims, characterised in that operation of at least one of the piston compressors (30, 32) by cylinder selection (Z) comprises operation with all the cylinder units (44), or some of these cylinder units (44), or operation with the cylinder units (44) switched off or the electric motor switched off.

7. A refrigerant compressor group according to one of the preceding claims, characterised in that, with an overall mass flow throughput close to the minimum mass flow throughput, the operating condition controller (130) operates only one of the piston compressors (30, 32), and / or in that in particular, with the lowest possible overall mass flow throughput, the operating condition controller (130) operates only the refrigerant compressor (30, 32) that is operable with time-modulated cylinder selection (Z'), and / or in that in particular, with an overall mass flow throughput close to the lowest possible overall mass flow throughput, the operating condition controller (130) operates only the refrigerant compressor (30) that is operable with speed selection (D), and / or in that in particular, with the lowest overall mass flow throughput, the operating condition controller (130) operates only the piston compressor (30) with speed selection (D) and cylinder selection (Z).

8. A refrigerant compressor group according to one of the preceding claims, characterised in that, with the respective overall mass flow throughput, the operating condition controller (130) optimises the speed selection (D) and the cylinder selection (Z, Z') in respect of the highest quality grade or the highest COP value or the lowest electrical power consumption of the refrigerant compressor group (12).

9. A refrigerant compressor group according to one of the preceding claims, characterised in that, where there are a plurality of possible operating modes as a result of speed selection (D) and cylinder selection (Z), for the purpose of achieving the respective overall mass flow throughput, the operating condition controller (130) determines the quality grade or COP value or electrical power consumption for the possible operating modes and selects the operating mode with the highest quality grade or COP value or the lowest electrical power consumption.

10. A refrigerant compressor group according to one of the preceding claims, characterised in that the operating condition controller (130) has stored data that is required for determining the quality grade or COP value or electrical power consumption for the respective speed selection (D) and / or cylinder selection (Z).

11. A refrigerant compressor group according to one of Claims 8 to 10, characterised in that the quality grade or COP value or electrical power consumption is determined by the operating condition controller (130) by detecting the low pressure (PS) and / or high pressure (PH) of the refrigerant compressor group (12) and / or in that in particular, for the purpose of determining the quality grade or COP value or electrical power consumption, the operating condition controller (130) makes use of the refrigerant, the overall mass flow throughput, the electrical power consumption and / or the speed of the electric motors (60).

12. A refrigerant compressor group according to one of the preceding claims, characterised in that, for the purpose of optimising the quality grade or COP value or electrical power consumption of the possible operating modes comprising speed selection (D) and cylinder selection (Z), all the overall mass flow throughputs that are achievable by the refrigerant compressor group (12) are associated with different overall mass flow throughput ranges, and in that certain operating modes are associated with each overall mass flow throughput range.

13. A refrigerant compressor group according to one of the preceding claims, characterised in that activation and deactivation of each cylinder bank (42) is performed with the aid of a mechanical performance control unit (70) that is controlled by the operating condition controller (130), and / or in that in particular the mechanical performance control unit (70) is associated with a cylinder head (58) of the cylinder bank (42) and / or in that in particular the mechanical performance control unit (70) controls an inlet stream (74) into the inlet chamber (72) of the cylinder head (58) for the purpose of activating or deactivating the respective cylinder bank (42).

14. A refrigerant compressor group according to one of the preceding claims, characterised in that the performance control unit (70) connects the outlet chamber (164) to the inlet chamber (162) in the cylinder head (58) for the purpose of activating or deactivating the respective cylinder bank (42').

15. A refrigerant compressor group according to one of the preceding claims, characterised in that the operating condition controller (130) is an operating condition controller (130) that is separate from the frequency converter (132).

16. A refrigerant compressor group according to one of the preceding claims, characterised in that the operating condition controller (130) is arranged in a housing (40) that receives the frequency converter (132).

17. A refrigerant compressor group according to one of the preceding claims, characterised in that the cylinder banks (42) of the piston compressors (30, 32) work in a parallel operation and / or in that in particular the piston compressors (30, 32) have at least two cylinder units (44) per cylinder bank (42) and / or in that in particular the piston compressors (30, 32) have more than two cylinder banks (42).

18. A refrigeration system, comprising a refrigerant compressor group (12), a heat exchanger (18) on the high-pressure side, an expansion member (30), and a heat exchanger (32) on the low-pressure side, characterised in that the refrigerant compressor group (12) takes a form according to one of the preceding claims, in that in particular the refrigeration system (10) has a system controller (138) that generates the performance request signal (LA) for the operating condition controller, in that in particular the operating condition controller (130) is arranged in a housing of the system controller (138).