Improved screw compressor for air conditioning system

Abstract

Screw compressor (1) for a conditioning system comprising a housing (2) defining a space (3) and comprising a compressor stage (4) dividing space (3) into a high-pressure space (3'') and a low pressure space (3'), the screw compressor (1) comprising a control system (20) configured to control actuator means (12) in function of a control signal (O) to control the movement of a valve body (11a), the control system (20) comprising elaboration means configured to generate a control signal (O) in function of a pair of operative configurations: - A first configuration corresponding to a maximum efficiency configuration; and - A second configuration corresponding to a minimum noise configuration, wherein the first configuration valve body (11a) is set in first position and wherein in second configuration valve body (11a) is set in a second position.

Description

[0001] " IMPROVED SCREW COMPRESSOR FOR AIR CONDITIONING SYSTEM"

[0002] DESCRIPTION

[0003] Cross-Reference to Related Applications

[0004] This Patent Application claims priority from Italian Patent Application No . 102024000010726 filed on May 13 , 2024 , the entire disclosure of which is incorporated herein by reference .

[0005] Technical Field

[0006] The present invention concerns a compressor, in particular a screw compressor .

[0007] The present invention finds its preferred, although not exclusive , application in an air conditioning system . Reference will be made to this application by way o f example below .

[0008] Background of the Invention

[0009] Conventionally, screw compressors are widely used in conditioning system in order to compress refrigerant and air . In detail , JP2004137934 A or JP2015036512 A di sclose a screws compressor provided with a screw rotor . The main issues related to such typology of screw compressor are energetic ef ficiency and noise , as detailed below .

[0010] Speci fically, JP2004137934 discloses a single screw compressor equipped with a slide valve movable in the axial direction of the screw rotor . In this screw compressor, when the screw rotor rotates , fluid is sucked into a compression chamber formed by a spiral groove of the screw rotor and is compressed .

[0011] Further, when the compression chamber communicates with the discharge port of the slide valve , compressed fluid is discharged from the compression chamber through the discharge port .

[0012] In such screw compressor, when the slide valve moves , the discharge port formed there also moves . When the position of the discharge port changes , the volume of the compression chamber at the time it starts communicating with the discharge port changes . Therefore , when the slide valve is moved, the internal volume ratio changes accordingly .

[0013] JP2015036512 A discloses a power consumption reduction operation that adj usts the internal volume ratio Vi according to the pressure ratio of the high-pressure space and the low-pressure space and the rotational speed of the screw rotor, and screw compression in order to reduce the energy required to drive the screw rotor . In order to suppress the noise caused by the operation of the machine , an adj ustment device is provided which is configured to be able to perform a noise reduction operation of adj usting the internal volume ratio according to the pressure ratio and the rotational speed of the screw rotor .

[0014] However, both JP2004137934 A or JP2015036512 A still need improvements for further reducing the noise of the screw compressor while increasing its ef ficiency according to the speci fic operational need of the conditioning system .

[0015] Further examples of known compressors are disclosed in publications EP4067659 Al , EP3981987 Al or WO2022244219 Al .

[0016] Therefore , the need is felt to improve existing screw compressors for reducing noise while improving their ef ficiency .

[0017] An aim of the present invention is to satis fy the above mentioned needs in a cost-ef fective and optimi zed manner .

[0018] Summary of the Invention

[0019] The aforementioned aim is reached by a screw compressor, a refrigeration system and control method as claimed in the appended set of claims that are integral part of the present description .

[0020] Brief Description of Drawings

[0021] For a better understanding of the present invention, a preferred embodiment is described in the following, by way of a non-limiting example , with reference to the attached drawings wherein :

[0022] • Figure 1 is a schematic sectional representation of a screw compressor according to the present invention in a first operational configuration;

[0023] • Figure 2 is a schematic sectional representation of a screw compressor according to the present invention in a second operational configuration; and

[0024] • Figure 3 is a diagram showing operational curves related to the operation of the screw compressor .

[0025] Detailed Description of the Invention

[0026] Figures 1 and 2 disclose a screw compressor 1 for a refrigerator system (not shown) according to the invention comprising a housing 2 that extends along a longitudinal axis A and separates an inner space 3 with respect to the environment .

[0027] The compressor 1 comprises a compressor stage 4 housed within the inner space 3 and defining a compression chamber 5 . The compressor stage 4 divides the inner space 3 into a low-pressure space 3 ' upstream to the compressor stage 4 and a high-pressure space 3 ' ’ downstream to the compressor stage 4 .

[0028] In detail , the low-pressure space 3 ' is fluidly connected to an evaporator of the refrigeration system, while the high-pressure space 3 ' ’ is fluidly connected to a condenser of the refrigerator system .

[0029] The screw compressor 1 further comprising an electric motor 6 comprising an operative shaft 6a configured to carry the compression stage 4 . In detail , as shown in figures 1 and 2 the electric motor 6 comprises a stator 6 ' carried by housing 2 and a rotor 6 ' ’ coupled to the operative shaft 6a and configured to interact electromagnetically with the stator 6 ' to make the operative shaft 6a rotate , as per se known .

[0030] The operative shaft 6a is rotatably free supported, on the extremity opposed to the electric motor 6 , to a disk portion 2a fixedly carried by housing 2 within inner space 3 .

[0031] The screw compression stage 4 comprises essentially a screw rotor 7 fixedly carried by the operative shaft 6a and a pair of gate rotors 8 configured to mesh with the screw rotor 7 thereby defining the compression chamber 5 precedingly defined .

[0032] In detail , the screw rotor 7 is coaxial to the operative shaft 6a and both are configured to rotate about longitudinal axis A. The gate rotors 8 , are configured to rotate about respective axis that are transversal , in particular coincident and preferably perpendicular to the longitudinal axis . In particular, gate rotors 8 rotate about a transversal axis B perpendicular to longitudinal axis A.

[0033] As per se known the screw rotor 7 defines a spiral groove that is engaged, by meshing by gate rotors that are shaped as gears thereby defining the aforementioned compression chamber . Since such compressor stage 4 , screw roto 7 and gate rotors 8 are known, they not will be described further for sake of brevity .

[0034] The compressor 1 further comprise a regulation valve 11 that is configured to vary the internal volume ratio , i . e . the ratio between the high-pressure space 3 ' ’ and the low- pressure space 3 ' between a maximum and minimum value depending on the position of regulation valve 11 .

[0035] In detail , regulation valve 11 comprises a valve body I la housed about longitudinal axis A and configured to slide in contact to a shoulder 2b extending radially from housing 2 within space 3 from between a first limit position ( figure 1 ) and a second limit position ( figure 2 ) .

[0036] The movement of the valve body I la varies , clearly, the volume of the high-pressure space 3 ' ’ and low-pressure space 3 ' therefore varying the internal volume ratio . In the first limit position the low-pressure space 3 ' has its maximum volume while in the second limit position the low-pressure space 3 ' ha its minimum volume , conversely the high-pressure space 3 ' ' .

[0037] The compressor 1 comprises a wall portion 2c fixedly carried by the housing 2 and housed in the low-pressure space 3 ' . The first position limit position is the farthest position of the valve body I la with respect to wall portion 2c along longitudinal axis A while the second limit position is a contact position of the valve body I la to the wall portion 2c .

[0038] The compressor 1 comprises actuator means 12 configured to move the valve body I la between the first and second limit positions along longitudinal axis A.

[0039] In detail , actuator means 12 are fluid-actuated actuator means . In further detail , actuator means 12 comprises a piston 13 configured to slide within a chamber 14 that is defined by an actuator housing 15 . The actuator housing 15 is housed within space 3 , in detail within high- pressure space 3 ' ’ and delimits with this latter the chamber 14 .

[0040] Piston 13 is configured to slide in fluid-tight manner within chamber 14 so that this latter is divided into a first and a second portions 14 ' , 14 ' ’ fluidically separated one with respect to the other .

[0041] In detail , the first portion 14 ' is fluidly connected to the high-pressure space 3 ' ’ via a connection conduits ( sketched in the drawings ) while the second portion 14 ' ’ s fluidly connectable to the low-pressure space 3 ' as detailed in the following .

[0042] Piston 13 is connected to a support element 16 connecting an actuation rod 17 to the valve body 14 . In detail , it is noticed that piston can slide over longitudinal axis A, preferably, coaxial to this latter and similarly the support element 16 and the actuation rod 17 can move over longitudinal axis A according to the movement of the piston 13 .

[0043] The actuator means 12 further comprises elastic means 18 configured to exert a force suitable to maintain the valve body 14 in the first limit position. In detail, the elastic means 18 are operatively interposed between the support element 16 and the actuator housing 15. Preferably, elastic means 18 comprise a helicoidal spring that is housed coaxially about the actuation rod 17.

[0044] In detail, the actuator housing 15 is connected, or at least axially adjacent, to the disk portion 2a. The actuation rod 17 extends therefore radially about the disk portion 2a and through a wall of the actuator housing 15.

[0045] Preferably, a guide element 19 can be between housing 2 and the disk portion 2a in order to guarantee proper sliding of the actuation rod 17, i.e. to avoid bending of the actuation rod 17 due to its length.

[0046] The second portion 14' ’ of the chamber 14, as said, is selectively connected to the low-pressure space 3' .

[0047] In detail, the screw compressor 1 comprises a control system 20 configured to control the actuator means 12. Consequently to the above, control system 20 regulates the passage of fluid from the low-pressure space 3' towards the second portion 14' ’ of the chamber 14. In particular, such passage of fluid is regulated in order to define a specific position of the piston 13, i.e. of the valve body Ila between the first and second limit positions.

[0048] The control system 20 comprises valve means 21 configured to regulate the passage of the fluid via a bypass conduit ( sketched in the drawings ) under a preset control signal . In detail , valve means 21 comprise a proportional valve , or as limit option an ON-OFF valve , and more preferably an electro-actuated proportional valve , or as limit option an electro-actuated ON-OFF valve .

[0049] According to the above , the control system 20 comprises an electronic control unit 22 configured to generate a control signal 0 configured to control the actuator means 12 , i . e . via valve means 21 according to the above described embodiment .

[0050] The control system 20 comprise elaboration means configure to generate control signal 0 in function of a pair of operative configurations :

[0051] • A first operative configuration - maximum ef ficiency configuration - provide the control signal 0 to maintain minimi ze the energy consumption of the screw compressor 1 ; and

[0052] • A second operative configuration - minimum noise configuration - provide the control signal 0 to minimi ze the noise cause by the screw compressor 1 .

[0053] In detail , the first operative configuration corresponds to the valve body I l a set in the first limit position while the second operative configuration corresponds to the valve body I la set in the second limit position .

[0054] The operation of the embodiment of the invention as described above is the following .

[0055] In function of the control signal 0 provided by the control unit 22 , the valve means 21 allows the passage of fluid towards the second portion 14 ' ’ of chamber 14 . Then, the pressure acting on piston 13 allows the latter to move against the force exerted by elastic means 18 thereby moving the valve body I la .

[0056] I f no pressure acts on the piston 13 , the action of the elastic means and the high-pressure fluid acting in the first portion 14 ' maintain the valve body I l a in the first limit position .

[0057] In function of the position of the valve body 11 , the volume of compres sion chamber 5 varies at discharge timing, thereby varying the internal volume ratio .

[0058] Making reference to the diagram of figure 3 , it is plotted the working area W of the screw compressor 1 , i . e . the points wherein the screw compressor may operatively work wherein the x-axi s of the diagram relates to temperature of the evaporator of the conditioning system while the y-axis of the diagram relates to the temperature of the condenser of the conditioning system .

[0059] Two inclined lines are present :

[0060] - A maximum ef ficiency line E ( dot-dot-dash) relating to the operation of the screw compressor 1 according to the first operative configuration; and

[0061] - A minimum noise line N ( dot-dash-dot ) relating to the operation of the screw compressor 1 according to the second operative configuration .

[0062] The inclined lines represent the couples of points of evaporator and condenser temperature at which the screw compressor operates , thereby corresponding pressures in low- pressure space 3 ' and high-pressure space 3 ' ’ .

[0063] The diagram further comprises a limit line L, extending parallel to x-axis , therefore corresponding to points having the same condenser temperature , noise maximum temperature . The limit line L cross the minimum noise line N, thereby avoiding its operation for condenser temperature greater than the noise maximum temperature .

[0064] In other words , over the noise maximum temperature the electronic control unit allows the operation of screw compressor depending on the condition j udging by line "E" .

[0065] Clearly, other parameters related to the operation of the conditioning system and related to a noise condition that overcome the noise of the screw compressor may be used for inhibiting the possibility of using the second operative configuration, such as fan speed, other temperatures , a range of temperatures .

[0066] In particular, the electronic control unit control the screw compressor 1 , i . e . the actuator means 12 , based on a pressure ratio between the pressure in high-pressure space and the pressure in low-pressure space .

[0067] Accordingly, the internal volume ratio is adj usted in function of such pressure ratio thereby providing the operative points above or below lines E or N and L according to the set operational configuration .

[0068] In view of the above description, the present invention further relates to a control method for controlling a screw compressor as described compris ing the following steps : i ) Receiving a signal for passing between the first and second operative configuration; iii ) Controlling the actuator means 12 for moving valve body I la in between the first and second limit positions .

[0069] The signal received may be imparted by the user or calculated automatically based on the operation of the conditioning system, e . g . based quantities of the conditioning system for instance on the condenser and evaporator temperatures .

[0070] The step iii ) further comprises the following sub-step : iii-a ) sending an output signal 0 to the valve means for allowing or denying the passage of fluid from high- pressure space towards the second portion 14 ' ’ of the chamber 14 .

[0071] The control method further comprises an intermediate step : ii ) veri fying i f a parameter of the conditioning system is within a preset range , i f yes , allow the use of the second operative configuration, i f not , deny the use of the second operative configuration, thereby passing / maintaining forcedly to the first operative configuration .

[0072] In particular, the parameter of the conditioning system used is the condenser temperature , in greater detail , the parameter should be maintained below a preset condenser temperature to allow the use of the minimum noise configuration .

[0073] The control steps may be executed continuously or a preset time interval by the electronic control unit 20 .

[0074] In view of the foregoing, the advantages of a compressor according to the invention are apparent .

[0075] Thanks to the proposed screw compressor it is possible to pass between the first and second operative conf igurations thereby allowing to guarantee the maximum ef ficiency or the minimum noise according to the operation of the conditioning system .

[0076] Indeed, in the maximum ef ficiency, the valve body minimi ze the space of discharge portion of the valve , i . e . the closer portion near to the valve body in the high- pressure space , thereby allowing over compression that helps to reduce needed to carry the screw rotor 7 , even i f increasing pulsation and therefore noise . On the other hand, in the minimum noise configuration the valve body is seated against the wall portion 2c . In particular, since the discharge portion of the valve is larger, less pul sation is present thereby leading to less noise . Moreover, the pressure exerted between the valve body 11 , the wall portion 2c and the shoulder 2b, allows to maintain the valve body I la substantially fixed to the housing, therefore reducing deeply the vibrations occurring and therefore noise .

[0077] The possibility of controlling automatically the passage between the first and second configuration is particularly useful since minimi ze the energetic consumption while reducing the noise generated by the screw-compressor according to the operation od the conditioning system .

[0078] Moreover, the fact that the noise temperature is limited according to a pre-set condition, i . e . the condenser temperature , allows to increase energetic ef ficiency when the noise reduction would be not beneficial .

[0079] Indeed, i f the condenser temperature is greater than a pre-set temperature , then the ventilation means would generate more noi se than the compressor' s noise and therefore any noise reduction of the compressor would be not beneficial for reducing the overall noise of the conditioning system It is clear that modi fications can be made to the described compressor which do not extend beyond the scope of protection defined by the claims .

[0080] For example , shape , dimensions and constructional characteristics of the housing and the elements housed within the inner space may vary . Clearly, other mechanical elements may be present and not represented for sake of clarity or brevity such as tight- means , screws etc .

[0081] Other parameters can be used for limiting the passage to the second operational configurations .

Claims

CLAIMS1.- Screw compressor (1) for a conditioning system comprising a housing (2) defining a space (3) and comprising a compressor stage (4) dividing said space (3) into a high- pressure space (3, f) and a low pressure space (3' ) , said compressor stage (4) comprising a screw rotor (7) and a pair of gate rotors (8) , said screw rotor (7) being operatively carried by an operative shaft (6a) to rotate about a first axis (A) and to engage said gate rotors (8) to suck a fluid from said low-pressure space (3' ) and discharge at a higher pressure into high-pressure space (3' ' ) , said screw compressor (1) further comprising a regulation valve (11) comprising a valve body (Ila) configured to move along said first axis (A) between a first limit position and a second limit position, said screw compressor (1) comprising a wall portion (2c) fixedly carried by said housing (2) within said low- pressure space (3' ) , said valve body (Ila) being in contact said wall portion (2c) in said second limit position and being distanced with respect to said wall portion (2c) along said first axis (A) in said first limit position, so that in said first limit position said low-pressure space (3' ) defines a maximum volume while in said second limit position said low-pressure space (3' ) defines a minimum volume while said high-pressure space (3, f) in said firstlimit position defines a minimum volume while in said second limit position said high-pressure space (3, f) defines a maximum volume. said screw compressor (1) comprising actuator means (12) configured to move said valve body (Ila) between said first and second limit positions, said screw compressor (1) comprising a control system (20) configured to control said actuator means (12) in function of a control signal (0) , said control system (20) comprising elaboration means configured to generate said control signal (0) in function of a pair of operative configurations:- A first configuration corresponding to a maximum efficiency configuration, wherein in said first configuration said valve body (Ila) is set in said first limit position; and- A second configuration corresponding to a minimum noise configuration, wherein in said second configuration said valve body (Ila) is set in said second limit position .2.- Screw compressor according to claim 1, wherein said control signal (0) is imparted by a user of said conditioning system.3.- Screw compressor according to claim 1, wherein said control signal (0) is elaborated on the base of operativequantities of the conditioning system.4.- Screw compressor according to claim 3, wherein said operative quantities comprises the temperatures of a condenser and of an evaporator of said conditioning system.5.- Screw compressor according to any of the preceding claims, wherein said actuator means (12) comprise fluid- actuated actuator means .6.- Screw compressor according to claim 5, wherein said actuator means (12) are controlled by valve means (21) configured to regulate the passage of fluid between said low-pressure space (3' ) and said high pressure space (3, f) said control signal (0) controlling said valve means (21) .7.- Screw compressor according to any of the preceding claims, wherein said housing (2) defines a shoulder (2b) slidingly in contact to said valve body (Ila) radially with respect to said first axis (A) , said wall portion (2c) contacting axially along said first axis (A) said valve body (Ha) .8.- Conditioning system comprising an evaporator, a condenser and a screw compressor according to any of the preceding claims.9.- Method for controlling a screw compressor (1) according to any of claims 1 to 7 in a conditioning system according to claim 8, comprising the following steps: i) Receiving a signal for passing between the first andsecond operative configuration; iii) Controlling said actuator means (12) for moving valve body (Ila) in between the first and second limit positions .10.- Method according to claim 9, wherein the received signal received is imparted by a user of said conditioning system.11.- Method according to claim 9, wherein the received signal received is calculated automatically by said control system (20) on the base of operative quantities of the conditioning system.12.- Method according to claim 11, wherein said quantities comprises the temperatures of said condenser and said evaporator of said conditioning system.13.- Method according to any of claims 9 to 12, further comprises the following sub-step: iii-a) sending an output signal 0 to valve means for controlling said valve means.14.- Method according to any of claims 9 to 13, further comprising an intermediate step: ii) verifying if a parameter of the conditioning system is within a preset range, if yes, allow the use of the second operative configuration, if not, deny the use of the second operative configuration, thereby passing / maintaining forcedly to the first operative configuration.15.- Method according to claim 14, wherein said parameter of the conditioning system used is a pre-set condenser temperature.

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