FIELD OF THE INVENTION

The present invention concerns a device for regulating the pressure and/or temperature of the refrigerant fluid entering a compressor of a refrigeration apparatus, respective refrigeration apparatus and method for operating said regulation device. In particular, this device is used in refrigeration apparatuses operating with refrigerant fluid of the carbon dioxide type or having similar characteristics.

It should, however, be emphasised that the solution object of the invention may also have application in the sector of the production of electric power.

KNOWN PRIOR ART

As known, a refrigeration apparatus for a refrigerant fluid of the type indicated above comprises a closed circuit within which the refrigerant fluid flows and along which a compressor, a refrigerant fluid cooler, an expansion valve and an evaporator are arranged.

In order to increase the efficiency of a refrigeration apparatus that uses carbon dioxide as refrigerant fluid, the use of one or more secondary economiser branches for the refrigerant fluid, which circulates within the closed circuit, is also known. It should be noted that, according to the known art, a secondary economiser branch is fluidically connected, on a side, to a section of the main branch of the closed circuit between the cooling device, or cooler, and the expansion valve and, on the other side, to the main compressor. This secondary economiser branch comprises an expansion valve and a heat exchanger for exchanging heat with the main circuit, whereas the flow rate coming from the secondary economiser branch has a pressure intermediate between the maximum and minimum pressure circulating within the circuit of the refrigeration device, i.e. between the pressure of the fluid at the cooling device and that at the evaporator.

In any case, even with the use of one or more secondary economiser branches, the refrigeration apparatuses adopting carbon dioxide as refrigerant fluid are not energy- efficient. In fact, their efficiency is still rather low.

Patent W02020084545, in the name of the applicant, describes a refrigeration apparatus which, in a circuit of the type described above, i.e. comprising at least one economiser branch, has also a device for regulating the pressure and temperature of the refrigerant fluid entering the main compressor of the apparatus. In practice, this regulation device comprises a reciprocating compressor functionally connected between the evaporator and the main compressor, and means for diverting at least one portion of the fraction of refrigerant fluid coming from the secondary economiser branch to control the displacement of the piston of the reciprocating compressor in order to compress the refrigerant fluid coming from the evaporator and contained in the cylinder of the same reciprocating compressor, and to reintroduce this portion of refrigerant fluid fraction into the secondary economiser branch during the displacement of the piston during the step of suctioning the refrigerant fluid coming from the evaporator, for the outflow of the portion of refrigerant fluid through the outlet section of the secondary economiser branch; wherein the outlet section of the secondary economiser branch is arranged downstream of the reciprocating compressor. The diversion means consist of piston cylinders keyed to a rod, the displacement of which is controlled by the piston in the reciprocating compressor of the regulation device instead. In particular, the displacement of this rod takes place when the piston reaches the end-stop inside the reciprocating compressor cylinder. In fact, there is a micro-switch on the cylinder head which, once pressed by the piston, allows the reciprocating compressor and diversion means to start the next operating cycle.

The reciprocating compressor used in such a solution is also known as free-piston expander-compressor, since the movement of the piston is not controlled by a connecting rod/crank mechanism but the piston is therefore free to move.

The solution above has the advantage of being mechanically very simple, however - on the other hand - it has the potential risk of collisions with the cylinder head. This is the reason why the oscillation frequency of the reciprocating compressor piston is kept low. However, the solution of using end-stops such as, e.g., the cylinders mentioned above, does not solve the problem of limiting the oscillation frequency of the reciprocating compressor’s piston and, in addition, does not allow certain parameters, which may be important for the correct operation of the refrigeration system in which this reciprocating compressor is installed, to be kept under control.

Object of the present invention is, therefore, to make a regulation device for a refrigeration apparatus which can be used without the risk of incurring possible mechanical breakages of the reciprocating compressor comprised therein due to piston knocks on the cylinder head.

Further object of the invention is to make a regulation device that allows easier control of the reciprocating compressor present therein.

Finally, object of the present invention is to implement a method that allows the regulation device in a refrigeration apparatus to be regulated more effectively and to be fine-tuned.

SUMMARY OF THE INVENTION

These and other objects are achieved by a device for regulating the pressure and/or temperature of the refrigerant fluid entering a compressor of a refrigeration apparatus having a closed circuit within which a flow rate of refrigerant fluid whose pressure and/or temperature has to be regulated, circulates, a cooling device and an evaporator, said regulation device comprising at least one reciprocating compressor equipped with at least one cylinder, at least one rod, at least one first piston integrally constrained to said rod and able to be translated within said cylinder, said cylinder being equipped with a first chamber comprising a first port for the suction inflow of a first flow rate of said refrigerant fluid coming from said evaporator and a second port for the outflow of said first flow rate of compressed refrigerant fluid contained in said first chamber and intended to reach said compressor, said cylinder further comprising a second chamber, which is fluidically separated from said first chamber by said first piston and equipped with at least one third port for the inflow of a second flow rate of said refrigerant fluid to displace said piston and compress said refrigerant fluid contained in said first chamber, said regulation device further comprising control means for controlling the actuation of said at least one rod, which are adapted to divert said at least one second flow rate of said refrigerant fluid for controlling the displacement of said at least one first piston and compressing the refrigerant fluid of said first flow rate, which is contained in said first chamber, and to re-enter said second flow rate of refrigerant fluid into said closed circuit during the displacement of said at least one first piston during the step of suctioning said first flow rate of refrigerant fluid, characterised in that said control means comprise a valve equipped with an inlet line and an outlet line for said second flow rate, and at least one first passage through said valve, said valve being rotatable in such a way as to assume at least one first radial position in which the fluidic communication between said inlet line to said rotary valve and said at least one second chamber is allowed through said at least one first passage, for the inflow of said second flow rate into said second chamber and the compression of said first flow rate contained in said at least one first chamber, and at least one second radial position in which the fluidic communication between said at least one second chamber and said outlet line of said rotary valve, for the suction of refrigerant fluid within said at least one first chamber, is allowed through said at least one passage. This device is used in particular in a refrigeration apparatus whose refrigerant fluid is carbon dioxide.

This solution allows to solve the problems of known art mentioned above.

Thanks to this solution, the oscillation frequency of the reciprocating compressor having a free piston, as in the case of the claimed compressor, is directly related to the rotation speed of the rotary valve. In practice, doubling the rotation speed of the valve, the oscillation frequency of the reciprocating compressor's piston doubles. Therefore, as the rotation speed of the valve increases, the piston stroke decreases and the flow rate of fluid processed by the reciprocating compressor increases. This means that through a device that regulates the speed of the rotary valve, e.g. a static inverter, it is possible to optimise the refrigeration cycle in order to maximise the efficiency or cooling power delivered by the system. Furthermore, the possibility of working at high frequency results in significant benefits in terms of the mechanical efficiency of the reciprocating compressor used. In fact, it is possible to use smaller reciprocating compressor displacements, hence more compact compressors, as the required displacement, under the same operating conditions, is inversely proportional to the oscillation frequency of the piston. This aspect becomes particularly relevant if we consider that, as high-pressure (even above 100 bars) refrigeration systems are involved, small displacements result in fewer safety problems.

In accordance with a further embodiment of the proposed solution, said reciprocating compressor comprises at least one further piston integrally constrained to said at least one rod and able to be translated within said cylinder, wherein said cylinder is equipped with a further first chamber comprising a further first port for the inflow of said first flow rate of said refrigerant fluid coming from said evaporator and a further second port for the outflow of said first flow rate of compressed refrigerant fluid contained in said further first chamber and intended to reach said compressor, said cylinder also comprising a further second chamber fluidically separated from said further first chamber by said further piston and equipped with at least one further third port for the inflow of a second flow rate of said refrigerant fluid to displace said piston and compress said refrigerant fluid contained in said further first chamber, said rotary valve being equipped with at least one second passage in such a way that, at least when said rotary valve assumes said first radial position, the fluidic communication between said at least one further second chamber and said outlet line of said rotary valve, for the suction of refrigerant fluid within said at least one further first chamber, is allowed through said at least one second passage, and at least when said rotary valve assumes said second radial position, the fluidic communication between said inlet line of said rotary valve and said at least one further second chamber for the inflow of said second flow rate into said further second chamber and the compression of said first flow rate contained in said at least one further first chamber, is allowed through said at least one second passage.

This further solution allows to have a continuous flow of the first flow rate and the second flow rate, from the relief line of the reciprocating compressor and from the outlet line of the rotary valve, respectively.

According to a particular aspect of the invention, the regulation device comprises means for regulating the rotation speed of said rotary valve and varying the switching frequency between said first and second radial positions.

In particular, said regulation means for said rotary valve comprise an electric motor mechanically combined with said rotary valve for its rotation, an inverter, which is adapted to regulate the rotation speed of said electric motor, and a control unit functionally connected to said inverter to control its operation.

In practice, based on the information from the control unit, the inverter allows to regulate the speed of the electric motor to which the rotary valve is mechanically connected.

In addition, the regulation device comprises a pressure sensor arranged along the inlet line at said rotary valve; said pressure sensor is functionally connected to said regulation means, in particular to said control unit, in such a way that the rotation speed of said valve is varied depending on the pressure measured by said pressure sensor.

In the case where, as however will be described below, the refrigeration system in which this device is installed has an economiser branch and this branch is at the inlet of the rotary valve, the oscillation frequency of the piston is controlled precisely by the pressure of the steam produced by the economiser (with pressure measurement coming from the aforementioned pressure sensor). The purpose, in this case, is to keep this pressure coming from the economiser constant (at the set-point value) because this way there is a double benefit. In fact, on the one hand, the maximum in terms of energy efficiency of the refrigeration cycle is achieved and, on the other hand, the risk that the system may become unstable, i.e. that the pressures and temperatures of the refrigerant fluid oscillate around the equilibrium value, is avoided.

In detail, in the event of an increase in pressure along the inlet line of the rotary valve of the refrigerant fluid with respect to the set point one, the control unit controls, by the inverter, an increase in the rotation speed of the rotary valve (therefore, of the electric motor to which the valve is integrally constrained) so as to result in a reduction in the pressure of the second flow rate of refrigerant fluid. When the pressure of the refrigerant fluid entering the rotary valve drops too low compared to the set-point value, the control unit controls, by the inverter, a decrease in the rotation speed of the rotary valve (therefore, of the electric motor to which the valve is integrally constrained) so as to result in an increase of the pressure of the second flow rate of refrigerant fluid. This allows to pursue the determined set-point pressure in order to achieve a certain level of refrigeration of the refrigeration apparatus in which the regulation device is installed.

Furthermore, the regulation device may comprise a pressure sensor and/or a temperature sensor which are arranged this time along the inlet line of said reciprocating compressor and functionally connected to said regulation means, in particular to said control unit, in such a way that the rotation speed of said valve is varied depending on the pressure and/or temperature measured by said pressure sensor and/or said temperature sensor.

Also in this case, the control of the rotation speed of the rotary valve is achieved by means of the pressure and/or temperature values of the fluid prior to its entry into the reciprocating compressor, therefore, at the evaporator outlet of the refrigeration apparatus in which the regulation device is installed.

Therefore, in the event of a change in the pressure and/or temperature values of the refrigerant fluid of the first flow rate that reaches the inlet line of the reciprocating compressor with respect to the set-point data, the control unit controls, through the inverter, an increase/decrease in the rotation speed of the rotary valve (therefore, of the electric motor to which the valve is integrally constrained) so as to result in an increase and/or decrease in the pressure of the first flow rate of refrigerant fluid.

Furthermore, in a further embodiment of the invention, the regulation device may comprise a position sensor for determining the position along said at least one cylinder of said first piston and/or said further first piston of said reciprocating compressor for determining the position reached by said first piston and/or said further piston. Said position sensor is functionally connected to said regulation means in such a way that the rotation speed of said valve is varied depending on the information obtained from said at least one position sensor. In practice, the control unit receives input information obtained from said at least one position sensor and controls the variation of the rotation speed of said valve depending on the information obtained from said at least one position sensor.

In particular, said position sensor comprises at least one proximity sensor.

This clearly allows to fine-control the position the piston must reach in order for it to function optimally. In fact, in the event that the piston, in its stroke, reaches the position in which the position sensor is located, then the control unit controls an increase in the rotation speed of the rotary valve and, therefore, at some point, there will be a reduction in the piston's stroke such that the proximity sensor will no longer be able to “sense” the presence of the piston. At that point, the control unit must control a decrease in the rotation speed of the rotary valve in order to increase the piston's stroke and thus reach the position of the pressure sensor again. In practice, in a sense, the position is continuously pursued along the cylinder where the position sensor is arranged.

As a result, the piston does not oscillate at a constant frequency but with a “slightly variable” frequency whose average value is the one that maximises the stroke.

According to a first embodiment of refrigeration apparatus, it comprises a closed circuit within which a flow rate of a refrigerant fluid circulates, a compressor, a cooling device, an evaporator from which a first flow rate flows out, and at least one expansion valve, and at least one regulation device according to one or more of claims 1 to 8, wherein said closed circuit further comprises at least one economiser branch along which a second flow rate of refrigerant fluid flows, said at least one economiser branch fluidically connecting a length of said closed circuit comprised between said cooling device and said expansion valve, and a length comprised between said evaporator and said compressor, and wherein said reciprocating compressor of said regulation device have said first flow rate exiting said evaporator at the inlet, said rotary valve have said second flow rate circulating along said economiser branch at the inlet, wherein said outlet line of said rotary valve is connected to the inlet line of said compressor, downstream of said reciprocating compressor.

As mentioned above, in this embodiment, the oscillation frequency of the piston can be controlled by the pressure of the steam produced by the economiser. The purpose, in this case, is to keep this pressure coming from the economiser constant (at the setpoint value) because this way there is a double benefit. In fact, on the one hand, the maximum in terms of energy efficiency of the refrigeration cycle is achieved and, on the other hand, the risk that the system may become unstable, i.e. that the pressures and temperatures of the refrigerant fluid oscillate around the equilibrium value, is avoided.

In accordance with a second embodiment of apparatus, it comprises a closed circuit within which a flow rate of a refrigerant fluid circulates, a compressor, a cooling device, an evaporator, and a regulation device according to one or more of claims 1 to 8, said reciprocating compressor of said regulation device having said first flow rate exiting from the evaporator at the inlet and said rotary valve having the flow rate exiting said refrigeration device at the inlet, the outlet line of said rotary valve being connected to said evaporator.

In particular, in this latter embodiment, said flow rate of refrigerant fluid circulating within said closed circuit is identical to said first flow rate of refrigerant fluid and said second flow rate of refrigerant fluid. Moreover, this embodiment is devoid of an expansion or metering valve.

Finally, the objects are also achieved by a method for operating a regulation device according to one or more of claims 1 to 8, said method comprising the step of: a) allowing the inflow of a first flow rate of refrigerant fluid within said at least one first chamber of said cylinder of said reciprocating compressor; b) allowing the inflow of a second flow rate of refrigerant fluid within said at least one second chamber of said cylinder of said reciprocating compressor to control the displacement of said at least one first piston and compress the refrigerant fluid of said first flow rate, which is contained in said first chamber; c) re-entering said second flow rate of refrigerant fluid into said closed circuit during the displacement of said at least one first piston during the step of suctioning said first flow rate of refrigerant fluid during said step a); characterised in that said step c) comprises the step cl) of rotating said rotary valve in said first position in such a way as to assume at least one first radial position in which the fluidic communication between said inlet line to said rotary valve and said at least one second chamber is allowed through said at least one first passage, for the inflow of said second flow rate into said second chamber and the compression of said first flow rate contained in said at least one first chamber, and the step c2) of rotating said rotary valve in said second radial position in which the fluidic communication between said at least one second chamber and said outlet line of said rotary valve is allowed through said at least one passage, for the suction of refrigerant fluid within said at least one first chamber.

Furthermore, the method comprises the step d) of regulating the switching speed of said rotary valve from said first radial position to said second radial position for the operation of a regulation device depending on the pressure of the refrigerant fluid entering said rotary valve, either depending on the pressure and temperature of the refrigerant fluid entering said first chamber of said reciprocating compressor or depending on the position of said at least one first piston within said cylinder.

DESCRIPTION OF THE FIGURES

Several particular embodiments of the present invention will now be described only by way of non-limiting example, with reference to the accompanying figures, in which:

Figure 1 is a schematic view of a refrigeration apparatus in which the regulation device according to the invention is installed;

Figure 2A is a longitudinal sectional schematic view of a regulation device according to the invention, at least when the rotary valve is in its first angular position;

Figure 2B is a longitudinal sectional schematic view of the regulation device of figure 2A, in which the rotary valve is in its second angular position;

Figure 3A is a longitudinal sectional schematic view of a regulation device in accordance with a second embodiment of the invention, at least when the rotary valve is in its first angular position;

Figure 3B is a longitudinal sectional schematic view of the regulation device of figure 3 A, in which the rotary valve is in its second angular position;

Figure 4 is a schematic view of a further refrigeration apparatus which comprises a regulation device according to the invention;

Figure 5 is a schematic view of a third refrigeration apparatus which comprises a regulation device according to the invention;

Figure 6 is a longitudinal sectional view of a third embodiment of the regulation device according to the invention.

DETAILED DESCRIPTION OF ONE OR MORE EMBODIMENTS OF THE PRESENT INVENTION

With particular reference to these figures, 1 denotes the generic regulation device according to the invention.

In particular, figure 1 shows a generic refrigeration apparatus 100 on which the regulation device 1 is installed.

In particular, this refrigeration apparatus 100 comprises a closed circuit C within which a flow rate P of a refrigerant fluid circulates, a compressor 101, a cooling device 102, an evaporator 103 from which a first flow rate XI flows out and at least one expansion valve 104. The compressor 101 is of the alternative type, however, in another embodiment, this compressor 101 may also be of another type without thereby departing from the scope of protection of the present invention. The closed circuit C further comprises an economiser branch 105 along which a second flow rate of refrigerant fluid X2 flows. This economiser branch 105 fluidically connects a length of the closed circuit comprised between the cooling device 102 and the expansion valve 104, and a length comprised between the evaporator 104 and the compressor 101. The economiser branch 105 comprises, in a known manner, a heat exchanger 106 and an expansion valve 107. Along this economiser branch 105, the pressure of the refrigerant fluid is lower than the pressure at the outlet of the cooling device 102. On the other hand, the pressure of the refrigerant fluid exiting the evaporator 103 is lower than the pressure of the refrigerant fluid of the second flow rate X2. The secondary branch 105 has an inlet manifold 105a of the flow rate X2 of refrigerant fluid within such secondary branch 105 and an outlet manifold 105b which connects to the closed circuit C upstream of the compressor 101.

A regulation device 1 for regulating the pressure and temperature of the refrigerant fluid entering the compressor 101 of the refrigeration apparatus 100 is shown in figure 2A.

In accordance with a first embodiment of the invention, the regulation device 1 comprises a reciprocating compressor 2 equipped with a cylinder 7, a rod 8, a first piston 9a integrally constrained to the rod 8 and able to be translated within the cylinder 7. This cylinder 7 is equipped with a first chamber 10 comprising a first port 11 for the suction inflow of a first flow rate XI of refrigerant fluid coming from the evaporator 103 and a second port 12 for the outflow of the first flow rate XI of compressed refrigerant fluid contained in the first chamber 10 and intended to reach the compressor 101 of the apparatus 100. The cylinder 7 further comprises a second chamber 20 fluidically separated from the first chamber 10 by the first piston 9a and equipped with a third port 21 for the inflow of a second flow rate X2 of refrigerant fluid to displace the piston 9a and compress the refrigerant fluid contained in the first chamber 10. It should be noted that, as however will also be clear from the description of the apparatuses 100’ and 100” of figures 4 and 5, the first flow rate XI of refrigerant fluid and the second flow rate X2 of refrigerant fluid could also be distinct, i.e. different, or else identical without thereby departing from the scope of protection of the present invention.

The regulation device 1 further comprises control means 50 for controlling the actuation of the rod 8, which are adapted to divert the second flow rate X2 of refrigerant fluid to control the displacement of the first piston 9a and compress the refrigerant fluid of the first flow rate XI contained in the first chamber 10, and to reenter the second flow rate X2 of refrigerant fluid into the closed circuit C during the displacement of the first piston 9a during the step of suctioning the first flow rate XI of refrigerant fluid. The control means 50 comprise a valve 51 equipped with an inlet line 51a and an outlet line 51b for the second flow rate X2, and a first passage 52a through the same valve 51. Additionally, this valve 51 is rotatable in such a way as to assume a first radial position Pl, in which the fluidic communication between the inlet line 5 la to the rotary valve 51 and the second chamber 20 for the inflow of the second flow rate X2 to the second chamber 20 and, simultaneously, the compression of the first flow rate XI contained in the first chamber 10 is allowed through the first passage 52a, and a second radial position P2 in which the fluidic communication between the second chamber 20 and the outlet line 51b of the rotary valve 51 for the suction of refrigerant fluid within the first chamber 10 is allowed through the first passage 52a. According to the above, the outlet line 51b of the rotary valve 51 is connected downstream of the reciprocating compressor 2 and upstream of the compressor 101. The outlet line 51b, in particular, connects to the manifold 105b of the economiser branch 105.

The rotary valve 51 has circular section and the passage 52a is formed within the body of the same rotary valve 51.

In practice, the rotary valve 51 is allowed to be rotated at a variable speed in such a way as to also control any possible and undesirable increases/decreases in the pressure of the refrigerant fluid of the second flow rate X2 during transients. In fact, the oscillation speed of the piston 9a of the reciprocating compressor 2 no longer depends, therefore, on the same piston but on the rotation speed of the rotary valve 51, i.e. its rotation frequency. However, the possibility of varying the speed of the rotary valve 51 and, therefore, switching this valve from the first Pl to the second P2 position, also allows to control the maximum oscillation of the piston 9a and, therefore, to prevent any possible excessive strokes of the piston 9a with undesirable knocks to the cylinder head of the reciprocating compressor 2.

Figure 2B shows the position reached by the piston 9b when the rotary valve 51 has moved from its first position Pl to its second position P2.

In a known manner, a suction valve 14 and a relief valve 15 are combined with the ports 11,12 of the reciprocating compressor 2, respectively. These valves 14,15 are opened and/or closed synchronously to the travel of the rod 8 in such a way as to cyclically have the step of suctioning the fluid into the first chamber 10 and the step of compressing and subsequently relieving the same refrigerant fluid contained in the first chamber 10. In practice, during the suctioning step of the reciprocating compressor 2, i.e. when the rotary valve 51 is located in its second position P2, the first port 11 allows the passage of the first flow rate XI within the first chamber 10 (therefore, the suction valve 14 is open), while the second port 12 prevents the outflow of the refrigerant fluid from the first chamber 10 (thus the relief valve 15 is closed).

In this step, through the third port 21, the outflow of the second flow rate X2 takes place from the second chamber 20.

Once the step of suctioning has been completed, when, therefore, the piston 9a reaches its rearmost position, the suction valve 14 closes, the rotary valve 51 assumes its first position Pl and the second flow rate X2, which will be at a pressure greater than the pressure of the fluid contained in the first chamber 10 in order to compress such fluid, begins to enter the second chamber 20. After the piston 9a has travelled a certain stroke, the relief valve 15 opens, thus allowing the first flow rate XI to flow along the relief line 2b. At this point, the relief valve 15 closes, the suction valve 14 opens, while the rotary valve 51 is displaced to its second position P2 to restart the cycle again. The speed between the suctioning and compressing steps of the reciprocating compressor 2 is clearly controlled by the switching speed of the rotary valve 51.

According to the embodiment described herein, the regulation device 1 comprises means 53 for regulating the rotation speed of the rotary valve 51 and varying the switching frequency between the first Pl and the second P2 radial positions.

These regulation means comprise, in particular, an electric motor 55 mechanically combined with said rotary valve 51 for its rotation, an inverter 56 adapted to regulate the rotation speed of said electric motor and a control unit 57 functionally connected to the inverter 56 to control its operation so as to regulate the rotation speed of the rotary valve 51 and the variation of the switching frequency between the first radial position Pl and the second P2 radial positions assumed by the rotary valve 51.

In particular, in figures 2A and 2B, the regulation device 1 comprises a pressure sensor 58 arranged along the inlet line 51a to the rotary valve 51. This pressure sensor 58 is functionally connected to the regulation means 53, in particular, to the control unit 57, in such a way that the rotation speed of the rotary valve 51 is varied depending on the pressure measured by the pressure sensor.

This allows to vary the speed of the rotary valve 51 in such a way as, e.g., to keep the pressure of the fluid of the second flow rate X2 circulating within the economiser branch 105 substantially constant. In fact, in the event of an increase in pressure along the inlet line of the rotary valve 51 of the refrigerant fluid with respect to that of the set point, the control unit 57 controls, by the inverter 56, an increase in the rotation speed of the rotary valve 51 (therefore, of the electric motor 55 to which the rotary valve 51 is integrally constrained) so as to result in a reduction in the pressure of the second flow rate X2 of refrigerant fluid. When the pressure of the refrigerant fluid entering the rotary valve 51 drops too low compared to the predetermined set-point value, the control unit 57 controls, by the inverter 56, a decrease in the rotation speed of the rotary valve 51 (therefore, of the electric motor 55 to which the rotary valve 51 is integrally constrained) so as to result in an increase of the pressure of the second flow rate X2 of refrigerant fluid. This allows to pursue the determined set-point pressure in order to achieve a certain level of refrigeration of the refrigeration apparatus 100 in which the regulation device is installed.

The purpose, in this case, is to keep the fluid pressure of the second flow rate X2 coming from the economiser 105 constant (at the set-point value) because this way there is a double benefit. In fact, on the one hand, the maximum in terms of energy efficiency of the refrigeration cycle is achieved and, on the other hand, the risk that the system 100 may become unstable, i.e. that the pressures and temperatures of the refrigerant fluid oscillate around the equilibrium value, is avoided.

In other embodiments, the device 1 comprises a pressure sensor 59 and a temperature sensor 60 which are arranged along the inlet line 2a of the reciprocating compressor 2 and functionally connected to the aforementioned control unit 57. In this embodiment, what controls the rotation speed of the rotary valve 51 is given by the temperature and pressure conditions of the refrigerant fluid coming from the evaporator 103. In practice, the system works in such a way that the behaviour of the evaporator 103 is optimised.

In accordance with a further embodiment of the invention, shown in figures 3A and 3B, the reciprocating compressor 2 comprises a further piston 9b integrally constrained to the rod 8 in a position opposite the piston 9a and able to be translated within the cylinder 7. This cylinder 7 is thus equipped with a further first chamber 10a comprising a further first port 11 a for the inflow of the first flow rate XI of refrigerant fluid coming from the evaporator 103 and a further second port 12a for the outflow of the first flow rate XI of compressed refrigerant fluid contained in the further first chamber 10a and intended to reach the compressor 101. The cylinder 7 further comprises a further second chamber 20a fluidically separated from the further first chamber 10a by the further piston 9b and equipped with a further third port 21a for the inflow of a second flow rate X2 of the refrigerant fluid to displace the further piston 9b and compress the refrigerant fluid contained in the further first chamber 10. The rotary valve 51 is further equipped with a second passage 52b in such a way that, at least when the rotary valve 51 assumes the first radial position Pl, the fluidic communication between the further second chamber 20a and the outlet line 51b of the rotary valve 51 for the suction of the refrigerant fluid within the further first chamber 10a is allowed through the second passage 52b, and at least when the rotary valve 51 assumes the second radial position P2, the fluidic communication between the inlet line 5 la of the rotary valve 51 and the further second chamber 20a, for the inflow of the second flow rate X2 of refrigerant fluid to the further second chamber 20a and the compression of the first flow rate contained in the further first chamber 10a, is allowed through the second passage 52b. This allows to have a continuous outlet flow rate from the reciprocating compressor 2, since in both the first radial position Pl and the second radial position P2 of the rotary valve 51, there will always be a first flow rate XI and a second flow rate X2 exiting the reciprocating compressor 2 to reach the compressor 101 of the refrigeration apparatus 100.

Also in this case, in a known manner, a suction valve 14a and a relief valve 15a are combined with the ports I la, 12a of the reciprocating compressor 2, respectively. These valves 14a, 15a are opened and/or closed synchronously to the travel of the rod 8 in such a way as to cyclically have the step of suctioning the fluid into the further first chamber 10a and the step of compressing and subsequently relieving the same refrigerant fluid contained in the further first chamber 10a. In practice, during the suctioning step of the reciprocating compressor 2 within the further first chamber 10a, i.e., when the rotary valve 51 is in its first position Pl (during which the compression of the fluid present in the further first chamber 10 takes place), the further first port I la is opened for the passage of the first flow rate XI within the further first chamber 10a (therefore, the suction valve 14a is opened), while the further second port 12a prevents the outflow of the refrigerant fluid from the further first chamber 10.

In this step, the outflow of the second flow rate X2 from the further second chamber 20 takes place through the further third port 21a.

Once the suctioning step has been completed, when, therefore, the piston 9b reaches its rearmost position, the further suction valve 14a closes (with the further relief valve 15a still closed), the rotary valve 51 assumes its second position P2 and the second flow rate X2, which will be at a pressure greater than the pressure of the fluid contained in the further first chamber 10a in order to compress such fluid, begins to enter the further second chamber 20. After the piston 9b has travelled a certain stroke, the relief valve 15a opens, thus allowing the first flow rate XI to flow along the relief line 2b. At this point, the further relief valve 15a closes, the further suction valve 14a opens, while the rotary valve 51 is displaced to its first position Pl to restart the cycle again. The speed between the suctioning and compressing steps of the reciprocating compressor 2 is clearly controlled by the switching speed of the rotary valve 51.

In this embodiment, however, due to the presence of two passages 52a and 52b, switching from the first position Pl to the second position P2 takes place at each rotation of 90° of the rotary valve 51.

Also in this embodiment, the rotary valve 51 is connected to an electric motor 55, an inverter 56 and a control unit 57 for regulating the rotation speed of the rotary valve 51 and varying the switching frequency between the first position Pl and the second radial position P2.

Moreover, as in the first embodiment, also in this embodiment the device 1 comprises a pressure sensor 58 arranged along the inlet line 51a of the rotary valve 51. This pressure sensor 58 is functionally connected to the control unit 57 in such a way as to regulate the speed of the rotary valve 51 (therefore of the motor 7 mechanically connected thereto) depending on the pressure of the refrigerant fluid detected by the sensor 58.

In figure 6 a device 1 is shown, albeit in an extremely simplified manner, which is quite similar to that of the second embodiment. It differs from the latter in that it comprises a position sensor 61 for determining the position along the cylinder 7 of the first piston 9a and, therefore, also of the further piston 9b of the reciprocating compressor 2 (since they are integrally and rigidly connected to the rod 8) for determining the position reached by the first piston 9a and, therefore, by the further piston 9b. In particular, this position sensor 61 comprises a proximity sensor. The position of the piston 9a is continuously transmitted to the control unit 57 so as to make the motor 55 (not shown herein, but present) controlling the rotation speed of the valve 51 pursue the correct position to be held by the pistons 9a, 9b, in their movement within the cylinder 7 and thus to avoid possible knocks of the pistons 9a and 9b within the cylinder 7.

In particular, it is possible to fine-control the position which the piston 9a (and therefore 9b) must reach in order for it to function optimally. In fact, in the event that the piston 9a, in its stroke, reaches the position in which the position sensor 61 is located, then the control unit 57 controls an increase in the rotation speed of the rotary valve 51 and, therefore, at some point, there will be a reduction in the piston's stroke 9a such that the proximity sensor 61 will no longer be able to “sense” the presence of the piston 9a. At that point, the control unit 57 must control a decrease in the rotation speed of the rotary valve 51 in order to increase the stroke of the piston 9a and thus reach the position of the pressure sensor 61 again. In practice, in a sense, the position is continuously pursued along the cylinder 7 where the position sensor 61 is arranged. As a result, the piston 9a does not oscillate at a constant frequency but with a “slightly variable” frequency whose average value is the one that maximises the stroke.

This embodiment is also clearly replicable with the first embodiment described above in which there is only one piston 9a, instead of two pistons 9a and 9b.

Figure 4 shows a second example of apparatus 100’ in which the regulation device 1 is present in its first embodiment or, alternatively, in its second embodiment.

In particular, this refrigeration apparatus 100’ comprises a closed circuit C within which a flow rate P of a refrigerant fluid circulates, a compressor 101, a cooling device 102, an evaporator 103 from which a first flow rate XI flows out and at least one expansion valve 104, and at least one regulation device 1 of the type described above, or in any case according to one or more of claims 1 to 8. The compressor 101 is of the reciprocating type, however in another embodiment this compressor 101 may also be of another type without thereby departing from the scope of protection of the present invention. The closed circuit C further comprises an economiser branch 105 along which a second flow rate of refrigerant fluid X2 flows. This economiser branch 105 fluidically connects a length of the closed circuit comprised between the cooling device 102 and the expansion valve 104, and a length comprised between the evaporator 104 and the compressor 101. The reciprocating compressor 2 of the regulation device 1 has, at the inlet, a first flow rate XI exiting the evaporator 104. The rotary valve 51 (in figure 4 only schematically shown) has the aforementioned second flow rate X2 circulating along the economiser branch 105 at the inlet, wherein said outlet line 51b of the rotary valve 51 is connected to the inlet line of the compressor 101 downstream of the reciprocating compressor 2. The economiser branch 105 comprises a heat exchanger 106 and a separator tank (or also known as a “flash tank”) for containing the refrigerant 107. Prior to the inflow to this tank 107, downstream of the heat exchanger 106, along the line there is a valve 120 for regulating the pressure of the refrigerant fluid entering the separator tank 120. Along this economiser branch 105, the pressure of the refrigerant fluid is identical to that present in the separating tank 107 but lower than that at the outlet of the cooling device 102. This apparatus 100’ also comprises a second economiser branch 110 along which a further flow rate X3 of refrigerant fluid flows. This second economiser branch 110, in a known manner, comprises a further expansion valve 111 and a heat exchanger 112. This further economiser branch 110 fluidically connects a length of the closed circuit C comprised between the inlet of the economiser branch 105 and the expansion valve 104, and a length comprised between the reciprocating compressor 2 and the compressor 101.

In this embodiment, the regulation device 1 comprises a pressure sensor 58 arranged along the inlet line 51a to the rotary valve 51, therefore, along the economiser branch 105 along which the second flow rate X2 flows. This pressure sensor 58 is functionally connected to the control unit 57. This allows to vary the speed of the rotary valve 51 and, thus, also to vary the pressure of the flow rate exiting the reciprocating compressor 2. The outlet line 51b of the rotary valve 51 is connected downstream of the reciprocating compressor 2 and upstream of the compressor 101. The outlet line 51b, in particular, is connected to the closed circuit upstream of the outlet line of the further economiser branch 110.

In figure 5, a further apparatus 100” is shown in which the regulation device 1 is used according to the invention.

This refrigeration apparatus 100" comprises a closed circuit C within which a flow rate P of a refrigerant fluid circulates, a compressor 101, a cooling device 102, an evaporator 103 and a regulation device 1 according to one of the embodiments described above and, in any case, according to one or more of claims 1 to 8. The reciprocating compressor 2 of the regulation device 1 has the first flow rate XI exiting the evaporator 103 at the inlet and the rotary valve 51 has the flow rate X2 exiting the refrigeration device 102 at the inlet, the outlet line 51b of the rotary valve 51 is connected to the evaporator 103. In practice, according to this configuration, the flow rate P of refrigerant fluid circulating within the closed circuit C is identical to the first flow rate XI of refrigerant fluid and the second flow rate X2 of refrigerant fluid. This apparatus 100” is devoid of an expansion valve, therefore the thermodynamic condition which would be implemented by means of such valve in the apparatus shown in figure 4, is implemented within the second chamber 20 and/or the further second chamber 20’ (in the case of use of the second embodiment of the invention).

In this embodiment, the regulation device 1 comprises a pressure sensor 59 and a temperature sensor 60 which are arranged along the inlet line 2a of the reciprocating compressor 2 and are functionally connected to the control unit 57 downstream of the evaporator 103.

This way, the regulation of the switching speed of the rotary valve 51 is based on the pressure and temperature parameters of the fluid exiting the evaporator 103. Therefore, the apparatus 100” is optimised to achieve the best possible performance at the evaporator 103.

The regulation device 1, in accordance with the first embodiment of the invention, operates according to a certain method. This method is also equivalently used for the device 1 in accordance with the second embodiment of the invention.

This method for operating the regulation device 1 comprises the steps of: a) allowing the inflow of a first flow rate XI of refrigerant fluid within the first chamber 10 of the cylinder 7 of the reciprocating compressor 2; b) allowing the inflow of a second flow rate X2 of refrigerant fluid within the second chamber 20 of the cylinder of the reciprocating compressor 2 to control the displacement of the first piston 9a and compress the refrigerant fluid of the first flow rate XI, which is contained in said first chamber 10; c) re-entering the second flow rate X2 of refrigerant fluid into the closed circuit C during the displacement of the first piston 9a during the step of suctioning said first flow rate of refrigerant fluid, during said step a); wherein step c) comprises step cl) of rotating the rotary valve 51 to the first position Pl in such a way as to assume at least one first radial position Pl, in which the fluidic communication between the inlet line 51a to the rotary valve 51 and the second chamber 20 for the inflow of the second flow rate X2 to the second chamber 20 and the compression of the first flow rate XI contained in the first chamber 10, is allowed through the passage 52a, and step c2) of rotating the rotary valve 51 to the second radial position P2, in which the fluidic communication between the second chamber 20 and the outlet line 51b of the rotary valve 51, is allowed through the passage 52a for the suction of refrigerant fluid within the first chamber 10.

Further, the method comprises step d) of regulating the switching speed of the rotary valve 51 from the first radial position Pl to the second radial position P2, depending on the pressure of the refrigerant fluid entering the rotary valve 51 or depending on the pressure and temperature of the refrigerant fluid entering the first chamber 10 of the reciprocating compressor 2, or depending on the position reached by the first piston 9a of the reciprocating compressor 2 within the cylinder 7.