Multi-compressor system with normally open valve in oil balance connection

Abstract

A multi-compressor system (7) includes: a plurality of compressors (8) connected in parallel; inlet connection lines (15), each inlet connection line being connected to a refrigerant suction port of a corresponding compressor (8); outlet connection lines (17), each outlet connection line being connected to a refrigerant discharge port of a corresponding compressor (8); a common oil balance line (18) and a balance connection line (19), each balance connection line connecting the common oil balance line (18) to an oil balance connection (21) of a corresponding compressor (8); and spring-loaded normally open valves (25), each spring-loaded normally open valve being disposed within a corresponding balance connection line (19) or within an oil balance connection (21) of a corresponding compressor (8), and each spring-loaded normally open valve being configured to close when the pressure difference between the main pressure in the low-pressure volume of the corresponding compressor (8) and the main pressure in the common oil balance line (18) reaches a predetermined value.

Description

Technical Field

[0001] This invention relates to a multi-compressor system, and more particularly to a multi-compressor refrigeration system. Background Technology

[0002] As is well known, a refrigeration system includes a refrigerant circulation loop, which consists of a condenser, an expansion unit, an evaporator, and a multi-compressor system connected in series. This multi-compressor system is also known as a manifold compressor system, and it includes:

[0003] - A plurality of compressors connected in parallel, the plurality of compressors including at least two compressors, each compressor including a compressor housing, the compressor housing being provided with a refrigerant suction port, a refrigerant discharge port and an oil balance connection;

[0004] - Common suction line and inlet connection line, each inlet connection line connects the common suction line to the refrigerant suction connector of the corresponding compressor;

[0005] - Common discharge line and outlet connection line, each outlet connection line connecting the common discharge line to the refrigerant discharge port of the corresponding compressor;

[0006] - Common oil balance line and balance connection line, each balance connection line connecting the common oil balance line to the oil balance connection of the corresponding compressor; and

[0007] - A controller configured to control the operation of the multi-compressor system.

[0008] When such a multi-compressor system operates with at least one compressor shut down (i.e., not in operation) and at least two compressors running, the pressure in the low-pressure volume of the shut-down compressor increases significantly and is higher than that of the running compressor. This causes refrigerant gas to flow from the shut-down compressor through the balance connection line and the common oil balance line connected to the shut-down compressor toward the running compressor.

[0009] In the balancing connection lines and common oil balancing lines connected to the stopped compressor, this gas bypass flow prevents oil from leaving the operating compressor through the corresponding balancing connection lines. Therefore, oil exchange between the two operating compressors is impossible, which may result in a low oil level in one operating compressor and an excessively high oil level in the other. A similar situation may occur in a multi-compressor system comprising four compressors when two compressors stop.

[0010] In a system with only two compressors, the increased pressure in the low-pressure volume of the stopped compressor will create both a bypass flow of refrigerant gas and a flow of oil from the oil sump of the stopped compressor toward the operating compressor. Therefore, there is a risk of oil loss from the stopped compressor and an increased oil circulation rate (OCR) due to excessive oil in the operating compressor. A similar situation may occur in multi-compressor systems with three, four, or even more compressors when only a single compressor is operating.

[0011] When a compressor that has experienced a significant drop in oil level is subsequently restarted, the amount of oil contained in the compressor's oil sump may be insufficient to ensure proper lubrication of the compressor's various moving parts. This could compromise the integrity of the compressor and, consequently, the relative stability of the aforementioned multi-compressor system.

[0012] US 10641268 discloses a multi-compressor system of the above type, wherein solenoid valves are arranged in a balancing connection line, and each solenoid valve is configured to isolate the low-pressure volume of the corresponding compressor from the common oil balancing line based on a control signal issued by a controller that receives signals from oil level detectors located in the respective compressors.

[0013] CN 21 0035940U illustrates a similar multi-compressor system with solenoid valves, each solenoid valve being arranged in a corresponding balancing connection line, and each solenoid valve being opened or closed based on the operating or stopped state of the corresponding compressor.

[0014] This configuration of the multi-compressor system disclosed in US 10641268 or CN 210035940 U prevents bypass flow of suction gas from idle compressors, thereby ensuring a good balance of oil level in the oil sump of the operating compressors.

[0015] However, this type of actively controlled valve (including valve installation and wiring) increases the cost of the multi-compressor system. Summary of the Invention

[0016] The purpose of this invention is to provide an improved multi-compressor system that overcomes the drawbacks encountered in conventional multi-compressor systems.

[0017] In particular, the purpose of this invention is to provide a multi-compressor system with good oil balance characteristics while reducing costs.

[0018] According to the present invention, such a multi-compressor system includes:

[0019] - A plurality of compressors connected in parallel, the plurality of compressors including at least two compressors, each compressor including a compressor housing, the compressor housing being provided with a refrigerant suction port, a refrigerant discharge port and an oil balance connection, each oil balance connection being fluidly connected to the low-pressure volume of the respective compressor and particularly fluidly connected to the oil sump of the respective compressor;

[0020] - A common suction line and an inlet connection line, each inlet connection line connecting the common suction line to the refrigerant suction connector of the corresponding compressor;

[0021] - Common discharge line and outlet connection line, each outlet connection line connecting the common discharge line to the refrigerant discharge port of the corresponding compressor;

[0022] - A common oil balance line and a balance connection line, each balance connection line connecting the common oil balance line to the oil balance connection of the corresponding compressor; and

[0023] - A plurality of spring-loaded normally open valves, each associated with a corresponding compressor, are configured to occupy an open configuration and a closed configuration. In the open configuration, the spring-loaded normally open valve fluidly connects the low-pressure volume of the corresponding compressor to the common oil balance line. In the closed configuration, the spring-loaded normally open valve fluidly isolates the low-pressure volume of the corresponding compressor from the common oil balance line at least partially. Each spring-loaded normally open valve is configured to shift to the closed configuration when the pressure difference between the primary pressure in the low-pressure volume of the corresponding compressor and the primary pressure in the common oil balance line reaches a predetermined value.

[0024] During partial load operation of this multi-compressor system, at least one compressor stops, and the pressure in the low-pressure volume of that compressor increases. When the pressure difference between the main pressure in the low-pressure volume of the non-operating compressor and the main pressure in the common oil balance line reaches a predetermined value, the corresponding spring-loaded normally open valve closes (i.e., shifts to a closed configuration), at least partially fluidly isolating the non-operating compressor from the common oil balance line.

[0025] Therefore, it prevents the formation of a bypass flow of suction gas through the balancing connection line connected to the non-operating compressor, and ensures a good balance of oil level in the oil sump of the operating compressor (when multiple compressors include three or more compressors) without using an active control valve.

[0026] Therefore, the multi-compressor system according to the present invention ensures good oil balance characteristics at a reduced cost.

[0027] Furthermore, preventing bypass flow from the idle compressor reduces the actual superheat seen by (one or more) operating compressors. In fact, without a spring-loaded normally open valve, the suction gas passing through the idle compressor heats the corresponding balancing connection line, thus increasing the actual superheat seen by (one or more) operating compressors. The presence of the spring-loaded normally open valve reduces the actual suction superheat, leading to a lower discharge temperature of the compressed refrigerant and thereby maximizing the operating range of the multi-compressor system.

[0028] Preventing this bypass flow from the idle compressor also reduces oil dilution in the idle compressor.

[0029] Furthermore, when the plurality of compressors comprises only two compressors, oil is prevented from flowing from the oil sump of the stopped compressor toward the operating compressor. This prevents the risk of oil loss from the stopped compressor and the risk of increased oil circulation rate (OCR) due to excessive oil in the operating compressor.

[0030] The multi-compressor system may also include one or more of the following features, either individually or in combination.

[0031] According to an embodiment of the invention, each spring-loaded normally open valve is configured to shift to a closed configuration when the corresponding compressor is shut down and at least one of the other compressors is running.

[0032] According to an embodiment of the invention, each spring-loaded normally open valve is configured to shift to an open configuration during operation of the corresponding compressor.

[0033] According to an embodiment of the present invention, each spring-loaded normally open valve is arranged in a corresponding balance connection line or in the corresponding oil balance connection of the compressor.

[0034] According to an embodiment of the invention, the predetermined value is between 5 mbar and 15 mbar, and for example, about 10 mbar.

[0035] According to an embodiment of the present invention, each oil balance connection includes an oil sump port disposed on the compressor housing of the corresponding compressor and an oil balance connector connected to the corresponding oil sump port, and each balance connection line is connected to the corresponding oil balance connector.

[0036] According to an embodiment of the present invention, at least one of the spring-loaded normally open valves is arranged in the oil sump port of the corresponding compressor, that is, embedded in the oil sump port of the corresponding compressor.

[0037] According to an embodiment of the present invention, at least one of the spring-loaded normally open valves is arranged within the oil balance joint of the corresponding compressor, that is, embedded in the oil balance joint of the corresponding compressor.

[0038] According to an embodiment of the present invention, each oil balance connector includes a first connector end portion connected to a corresponding oil sump port and a second connector end portion located away from the corresponding oil sump port.

[0039] According to an embodiment of the present invention, at least one of the spring-loaded normally open valves is arranged at the second connector end portion of the oil balance joint of the corresponding compressor.

[0040] According to an embodiment of the present invention, at least one of the spring-loaded normally open valves is arranged outside the compressor housing of the respective compressor.

[0041] According to an embodiment of the present invention, at least one of the balance connection lines includes a first tubular connection component connected to the common oil balance line and a second tubular connection component connected to the oil balance connection of the corresponding compressor, and a corresponding spring-loaded normally open valve is disposed between the first tubular connection component and the second tubular connection component.

[0042] According to an embodiment of the present invention, each spring-loaded normally open valve includes:

[0043] - Fluid flow channels;

[0044] - A valve seat surrounding the corresponding fluid flow passage; and

[0045] - A valve member movable between a closed position and an open position. In the closed position, the valve member abuts against a corresponding valve seat and at least partially closes the corresponding fluid flow passage. In the open position, the valve member moves away from the corresponding valve seat and opens the corresponding fluid flow passage.

[0046] According to an embodiment of the invention, the fluid flow passage of each spring-loaded normally open valve is configured to fluidly connect the low-pressure volume of the corresponding compressor to the common oil balance line.

[0047] According to an embodiment of the invention, each valve component is configured to move to the closed position when the pressure difference between the main pressure in the low-pressure volume of the respective compressor and the main pressure in the common oil balance line reaches a predetermined value.

[0048] According to an embodiment of the invention, each valve component includes an oil passage orifice configured to prevent excessive oil accumulation in the oil sump of the respective compressor when the compressor is shut down.

[0049] According to an embodiment of the present invention, each oil passage hole is arranged in the lower part of the corresponding valve component.

[0050] According to an embodiment of the present invention, each valve component has a disc shape.

[0051] According to an embodiment of the present invention, each spring-loaded normally open valve further includes a mounting component, which is provided with a corresponding valve seat and attached to a corresponding balance connection line or a corresponding oil balance connection.

[0052] According to an embodiment of the present invention, each mounting component is annular.

[0053] According to an embodiment of the invention, each valve component is pivotally mounted about a pivot axis that can extend substantially horizontally.

[0054] According to an embodiment of the invention, each spring-loaded normally open valve further includes a support shaft configured to support the corresponding valve member and non-rotatably fixed to the corresponding valve member, the support shaft being pivotally mounted to the corresponding mounting component about the corresponding pivot axis.

[0055] According to an embodiment of the invention, each spring-loaded normally open valve further includes a spring member (such as a torsion spring) configured to bias the corresponding valve member toward the open position of the valve member.

[0056] According to an embodiment of the invention, each spring member includes a first end member and a second end member, the first end member being, for example, a first end branch, configured to cooperate with a corresponding mounting member; the second end member being, for example, a second end branch, configured to cooperate with a corresponding valve member, and in particular with a first surface of the corresponding valve member oriented toward a corresponding valve seat.

[0057] According to an embodiment of the invention, each spring member further includes a central portion surrounding the corresponding support shaft.

[0058] According to an embodiment of the present invention, each mounting component includes a fixing slot in which a first end component of a corresponding spring member is received.

[0059] According to another embodiment of the invention, each valve member is slidably mounted along the displacement direction. Advantageously, each spring-loaded normally open valve includes at least one guide member (e.g., a guide rod) configured to guide the respective valve member between an open position and a closed position.

[0060] According to an embodiment of the present invention, the multi-compressor system includes a controller configured to control the operation of the multi-compressor system, the controller being configured to operate the multi-compressor system according to a plurality of predetermined operating configurations.

[0061] According to an embodiment of the present invention, the plurality of predetermined operating configurations include a partial load operating configuration, wherein at least one of the compressors stops while all other compressors of the plurality of compressors operate.

[0062] According to an embodiment of the invention, each predetermined operating configuration is configured to produce a predetermined output capacity for the multi-compressor system.

[0063] According to an embodiment of the invention, the controller is configured to control the plurality of compressors in response to the required output capacity of the multi-compressor system.

[0064] According to an embodiment of the present invention, the controller is configured to select a predetermined operating configuration from the plurality of predetermined operating configurations that corresponds to the output capacity required by the multi-compressor system.

[0065] According to an embodiment of the present invention, the plurality of predetermined operating configurations include a full-load operating configuration, wherein all of the plurality of compressors are running.

[0066] According to an embodiment of the present invention, each compressor includes a single oil balance connection.

[0067] According to an embodiment of the present invention, each balancing connection line includes a tubular connection component, the tubular connection component including a first end portion connected to the common oil balancing line and a second end portion connected to the oil balancing connection portion of the corresponding compressor.

[0068] According to an embodiment of the present invention, the mounting component of at least one spring-loaded normally open valve is configured to abut against the axial end surface of a corresponding oil balance joint.

[0069] According to an embodiment of the present invention, the mounting component of at least one spring-loaded normally open valve is configured to abut against the axial end surface of the second end portion of the corresponding tubular connecting component.

[0070] According to an embodiment of the present invention, each of the plurality of compressors is a scroll compressor.

[0071] According to an embodiment of the present invention, each of the compressors includes an oil sump located in the lower portion of the respective compressor housing.

[0072] According to embodiments of the invention, the inlet connection lines have consistent or similar dimensions. In this document, "similar dimensions" means that the ratio of any dimension of one inlet connection line to the corresponding dimension of any other inlet connection line is between 0.8 and 1.2, and advantageously between 0.9 and 1.1.

[0073] According to an embodiment of the invention, each of the plurality of compressors has a variable capacity and includes, for example, an electric motor with a variable speed.

[0074] According to an embodiment of the invention, each of the plurality of compressors has a fixed capacity and includes, for example, an electric motor with a fixed speed.

[0075] According to an embodiment of the present invention, the plurality of compressors includes both variable capacity compressors and fixed capacity compressors.

[0076] According to an embodiment of the invention, all oil balance connections are positioned at approximately the same vertical elevation relative to the bottom of the respective compressor housing. This configuration ensures proper oil level balance in the plurality of compressors.

[0077] According to an embodiment of the invention, the second end portion of each tubular connecting member includes an axial end surface that is substantially recessed from the inner surface of the compressor housing of the respective compressor.

[0078] According to an embodiment of the present invention, the plurality of compressors includes at least three compressors.

[0079] According to an embodiment of the present invention, the plurality of compressors includes at least four compressors.

[0080] The present invention also relates to a refrigeration system comprising a refrigerant circulation loop, and comprising, in sequence, a condenser, an expansion device, an evaporator, and a multi-compressor system according to the present invention connected in series. Attached Figure Description

[0081] The following detailed description of three embodiments of the invention will be better understood when read in conjunction with the accompanying drawings, however, the invention is not limited to the specific embodiments disclosed.

[0082] Figure 1 This is a schematic diagram of a refrigeration system including a multi-compressor system according to a first embodiment of the present invention.

[0083] Figure 2 yes Figure 1 A perspective view of a multi-compressor system.

[0084] Figure 3 yes Figure 1A perspective view of a multi-compressor system, in which one compressor is cut along a section extending through the corresponding oil sump port.

[0085] Figure 4 yes Figure 3 A magnified view of the details.

[0086] Figure 5 yes Figure 1 Front perspective view of a spring-loaded normally open valve in a multi-compressor system.

[0087] Figure 6 yes Figure 5 Rear perspective view of a spring-loaded normally open valve.

[0088] Figure 7 yes Figure 5 A cross-sectional view of a spring-loaded normally open valve.

[0089] Figure 8 This is a partial cross-sectional view of a multi-compressor system according to a second embodiment of the present invention.

[0090] Figure 9 This is a partial cross-sectional view of a multi-compressor system according to a third embodiment of the present invention. Detailed Implementation

[0091] Figure 1 A refrigeration system 2 is described, which includes a refrigerant circulation loop 3 and sequentially comprises a condenser 4, an expansion device 5, an evaporator 6, and a multi-compressor system 7 connected in series.

[0092] The multi-compressor system 7 includes multiple compressors 8 connected in parallel. The multiple compressors include at least three compressors 8, and for example, four compressors 8.

[0093] Each compressor 8 includes a compressor housing 9, which is provided with a refrigerant suction port 11 and a refrigerant discharge port 12. The refrigerant suction port 11 is configured to supply refrigerant gas to be compressed to the corresponding compressor 8, and the refrigerant discharge port 12 is configured to discharge compressed refrigerant gas.

[0094] Advantageously, each compressor 8 is a scroll compressor and includes a compression unit (not shown in the figure) disposed inside the respective compressor housing 9 and configured to compress refrigerant gas supplied by the respective refrigerant suction connector 11. Each compression unit includes a fixed scroll and a moving scroll, the fixed scroll being fixed relative to the respective compressor housing 9, and the moving scroll being configured to perform an oscillating motion relative to the respective fixed scroll during operation of the respective compressor 8.

[0095] Furthermore, each compressor 8 includes a drive shaft (not shown in the figure) and an electric motor (not shown in the figure). The drive shaft is vertically oriented and configured to drive a corresponding scroll plate in a revolute motion. The electric motor is arranged within the corresponding compressor housing 9 and connected to the corresponding drive shaft to rotate the corresponding drive shaft about a rotation axis. Each of the plurality of compressors 8 may have a variable capacity and may, for example, include an electric motor with a variable speed. However, each of the plurality of compressors 8 may have a fixed capacity and may, for example, include an electric motor with a fixed speed.

[0096] Each compressor 8 also includes an oil sump 13 located in the lower part of the corresponding compressor housing 9.

[0097] The multi-compressor system 7 also includes a common suction line 14 and inlet connection lines 15, each inlet connection line 15 connecting the common suction line 14 to the refrigerant suction connector 11 of the corresponding compressor 8. Figure 2 As shown, the inlet connection line 15 has uniform dimensions and can have uniform flow constraints. Advantageously, the inlet connection line 15 is substantially uniform and extends horizontally.

[0098] The multi-compressor system 7 also includes a common discharge line 16 and outlet connection lines 17, each outlet connection line 17 connecting the common discharge line 16 to the refrigerant discharge connector 12 of the corresponding compressor 8. Figure 2 As shown, the outlet connection line 17 has uniform dimensions. Advantageously, the outlet connection line 17 is substantially uniform and extends horizontally.

[0099] Furthermore, the multi-compressor system 7 includes a common oil balance line 18 and balance connection lines 19 (also referred to as balance branch lines), each balance connection line 19 connecting the common oil balance line 18 to an oil balance connection portion 21 disposed on the compressor housing 9 of the respective compressor 8. The common oil balance line 18 and the balance connection lines 19 are specifically configured to fluidly connect the low-pressure volumes of the compressors 8, and particularly the oil sump 13 of the compressors 8, thereby allowing oil to flow between the compressors 8 and balancing the oil level within the compressors 8. Advantageously, the common oil balance line 18 and the balance connection lines 19 extend horizontally, and all the oil balance connections 21 are at approximately the same vertical elevation relative to the bottom of the respective compressor housing 9.

[0100] like Figure 4Preferably shown, each oil balance connection 21 includes an oil sump port 22 and an oil balance connector 23. The oil sump port 22 is disposed on the compressor housing 9 of the corresponding compressor 8, and the oil balance connector 23 is connected to the corresponding oil sump port 22 and to the corresponding balance connection pipe 19. Each of the oil balance connectors 23 is tubular and includes a first connector end portion 23.1 connected to the corresponding oil sump port 22 and a second connector end portion 23.2 located away from the corresponding oil sump port 22.

[0101] according to Figures 1 to 7 In the embodiment shown, each balance connection line 19 includes a tubular connection component 24, which includes a first end portion 24.1 connected to the common oil balance line 18 and a second end portion 24.2 connected to the corresponding oil balance connector 23.

[0102] The multi-compressor system 7 also includes spring-loaded normally open valves 25, each arranged within the oil balance connection 21 of a corresponding compressor 8. Each spring-loaded normally open valve 25 is configured to open when the corresponding compressor 8 is running, such that the low-pressure volume of the corresponding compressor 8 is fluidly connected to the common oil balance line 18. Each spring-loaded normally open valve 25 is also configured to close when the corresponding compressor 8 is shut down and at least one of the other compressors 8 is running, such that the low-pressure volume of the corresponding compressor 8 is at least partially fluidly isolated from the common oil balance line 18 (in other words, the communication between the low-pressure volume of the corresponding compressor 8 and the common oil balance line 18 is cut off).

[0103] like Figures 4 to 7 As preferably shown, each spring-loaded normally open valve 25 includes a mounting member 26 attached to a corresponding oil balance connection 21, and is provided with a fluid flow passage 27 and a valve seat 28 surrounding the corresponding fluid flow passage 27. Advantageously, each mounting member 26 is annular.

[0104] according to Figures 1 to 7 In the illustrated embodiment, the mounting component 26 of each spring-loaded normally open valve 25 is embedded in the oil sump port 22 of the corresponding compressor 8 and is configured to abut against the axial end surface of the corresponding oil balance joint 23. The mounting component 26 of each spring-loaded normally open valve 25 can, for example, be securely fitted into the oil sump port 22 of the corresponding compressor 8.

[0105] Each spring-loaded normally open valve 25 also includes a valve member 29 movable between a closed position and an open position, in which the valve member 29 abuts against a corresponding valve seat 28 and closes the corresponding fluid flow passage 27, and in the open position, the valve member 29 moves away from the corresponding valve seat 28 and opens the corresponding fluid flow passage 27. Each valve member 29 specifically includes a first surface configured to be oriented toward the corresponding valve seat 28 and a second surface opposite to the corresponding first surface.

[0106] according to Figures 1 to 7 In the embodiment shown, each valve component 29 has a disc shape and is pivotally mounted about a pivot axis A, which advantageously extends substantially horizontally.

[0107] Each spring-loaded normally open valve 25 also includes a support shaft 31 configured to support the corresponding valve member 29 and non-rotatably fixed to the upper portion of the corresponding valve member 29, the support shaft 31 being pivotally mounted to the corresponding mounting component 26 about the corresponding pivot axis A.

[0108] Each spring-loaded normally open valve 25 also includes a spring member 32 (such as a torsion spring) configured to bias the corresponding valve member 29 toward the open position of the valve member. Figures 1 to 7 In the embodiment shown, each spring member 32 includes:

[0109] - A first end component 32.1, such as a first end branch, is configured to cooperate with a corresponding mounting component 26;

[0110] - A second end component 32.2, such as a second end branch, is configured to mate with a corresponding valve member 29, and in particular with a first surface of the corresponding valve member 29 oriented toward the corresponding valve seat 28; and

[0111] - The middle portion 32.3 surrounds the corresponding support shaft 31.

[0112] according to Figures 1 to 7 In the illustrated embodiment, each mounting component 26 advantageously includes a fixing slot 33 in which a first end component 32.1 of the corresponding spring member 32 is received.

[0113] The valve member 29 of each spring-loaded normally open valve 25 is specifically configured to move to the closed position when the pressure difference between the main pressure in the low-pressure volume of the corresponding compressor 8 and the main pressure in the common oil balance line 18 reaches a predetermined value, which is between 5 mbar and 15 mbar, and for example 10 mbar.

[0114] During partial load operation of the multi-compressor system 7, at least one compressor 8 stops (while the other compressors 8 operate), and the pressure in the low-pressure volume of the compressor 8 increases. When the pressure difference between the main pressure in the low-pressure volume of the non-operating compressor 8 and the main pressure in the common oil balance line 19 reaches a predetermined value, the main pressure in the low-pressure volume of the non-operating compressor 8 overcomes the opening force of the spring member 32 of the corresponding spring-loaded normally open valve 25, thereby moving the valve member 29 of the spring-loaded normally open valve 25 to the closed position and fluidly isolating the non-operating compressor from the common oil balance line 18.

[0115] Therefore, bypass flow of suction gas through the balancing connection line 19 connected to the inactive compressor 8 is prevented, and good oil level balance in the oil sump 13 of the operating compressor 8 is ensured. Thus, the multi-compressor system 7 according to the invention ensures good oil balance characteristics at a reduced cost.

[0116] according to Figures 1 to 7 In the illustrated embodiment, each valve member 29 includes an oil passage hole 34 disposed in the lower portion of the respective valve member 29. Such an oil passage hole 34 ensures that oil flows out of the respective compressor 8 when the compressor 8 is turned off. Therefore, the oil passage hole 34 provided on each valve member 29 is configured to prevent excessive oil accumulation in the oil sump 13 of the respective compressor 8 when the compressor 8 is turned off.

[0117] The multi-compressor system 7 also includes a controller 35 configured to control the operation of the multi-compressor system 7, i.e., to control the operation (start or stop) of the multiple compressors, and specifically to control which of the multiple compressors 8 is in operation. The controller 35 may, for example, include a microprocessor and memory.

[0118] Specifically, the controller 35 is configured to operate the multi-compressor system 7 according to a plurality of predetermined operating configurations. The predetermined operating configurations include specific on / off configurations of the compressors 8, depending on the required load, i.e., the required output capacity. Advantageously, each predetermined operating configuration is configured to result in a predetermined output capacity of the multi-compressor system 7, and the controller 35 is configured to control the plurality of compressors in response to the required output capacity of the multi-compressor system 7. In particular, the controller 35 is configured to select from the plurality of predetermined operating configurations the predetermined operating configuration corresponding to the required output capacity of the multi-compressor system 7.

[0119] The multiple pre-defined operation configurations mainly include:

[0120] - A partial load operation configuration in which at least one of the compressors 8 stops while all other compressors 8 of the plurality of compressors 8 are running;

[0121] ∑ A partial load operation configuration in which at least two compressors 8 stop while all other compressors 8 of the plurality of compressors are running; and

[0122] - A full-load operation configuration in which all 8 of the multiple compressors are running.

[0123] Figure 8 The multi-compressor system 7, representing a second embodiment of the present invention, is... Figures 1 to 7 The main difference in the illustrated embodiment is that the mounting part 26 of each spring-loaded normally open valve 25 is arranged at the second connector end portion 23.2 of the oil balance joint 23 of the corresponding compressor 8. Advantageously, the mounting part 26 of each spring-loaded normally open valve 25 is configured to abut against the axial end surface of the second end portion 24.2 of the corresponding tubular connection part 24.

[0124] Figure 9 The multi-compressor system 7, representing a third embodiment of the present invention, is... Figures 1 to 7 The main difference in the illustrated embodiment is that each spring-loaded normally open valve 25 is arranged outside the compressor housing 9 of the respective compressor 8, and specifically within the respective balancing connection line 19.

[0125] According to the third embodiment of the present invention, each balance connection line 19 includes a first tubular connection component 36 connected to the common oil balance line 18 and a second tubular connection component 37 connected to the oil balance connection portion 21 of the corresponding compressor 8, and the mounting component 26 of the corresponding spring-loaded normally open valve 25 is disposed between the first tubular connection component 36 and the second tubular connection component 37.

[0126] According to another embodiment of the invention, not shown in the figures, each valve member 29 may be slidably mounted along the displacement direction (e.g., substantially parallel to the central axis of the corresponding oil balance connection 21) and between the open and closed positions of the valve member. According to this embodiment of the invention, each spring-loaded normally open valve 25 may include at least one guide member (e.g., a guide rod) configured to guide the corresponding valve member 29 between the open and closed positions.

[0127] Of course, the present invention is not limited to the embodiments described above by way of non-limiting example; rather, the present invention covers all embodiments thereof.

Claims

1. A multi-compressor system (7), comprising: Multiple compressors (8) connected in parallel, the multiple compressors including at least two compressors (8), each compressor (8) including a compressor housing (9), the compressor housing (9) being provided with a refrigerant suction port (11), a refrigerant discharge port (12) and an oil balance connection (21), each oil balance connection (21) being fluidly connected to the low-pressure volume of the corresponding compressor (8); A common suction line (14) and an inlet connection line (15), each inlet connection line (15) connecting the common suction line (14) to the refrigerant suction connector (11) of the corresponding compressor (8). Common discharge line (16) and outlet connection line (17), each outlet connection line (17) connecting the common discharge line (16) to the refrigerant discharge connector (12) of the corresponding compressor (8). A common oil balance line (18) and a balance connection line (19), each balance connection line (19) connecting the common oil balance line (18) to the oil balance connection (21) of the corresponding compressor (8); and Multiple spring-loaded normally open valves (25), each spring-loaded normally open valve (25) is associated with a corresponding compressor (8), and each spring-loaded normally open valve (25) is configured to occupy an open configuration and a closed configuration, wherein, In the open configuration, the spring-loaded normally open valve (25) fluidly connects the low-pressure volume of the corresponding compressor (8) to the common oil balance line (18). In the closed configuration, the spring-loaded normally open valve (25) fluidly isolates the low-pressure volume of the corresponding compressor (8) from the common oil balance line (18) at least partially. Each spring-loaded normally open valve (25) is configured to shift to the closed configuration when the main pressure in the low-pressure volume of the corresponding compressor (8) is higher by a predetermined value than the main pressure in the common oil balance line (18).

2. The multi-compressor system (7) according to claim 1, wherein, The predetermined value is between 5 mbar and 15 mbar.

3. The multi-compressor system (7) according to claim 1 or 2, wherein, Each spring-loaded normally open valve (25) is arranged in the corresponding balance connection line (19) or in the corresponding oil balance connection part (21) of the compressor (8).

4. The multi-compressor system (7) according to claim 1 or 2, wherein, Each oil balance connection (21) includes an oil sump port (22) disposed on the compressor housing (9) of the corresponding compressor (8) and an oil balance connector (23) connected to the corresponding oil sump port (22), and each balance connection line (19) is connected to the corresponding oil balance connector (23).

5. The multi-compressor system (7) according to claim 4, wherein, At least one of the spring-loaded normally open valves (25) is arranged in the oil sump port (22) of the corresponding compressor (8).

6. The multi-compressor system (7) according to claim 4, wherein, At least one of the spring-loaded normally open valves (25) is arranged in the oil balance joint (23) of the corresponding compressor (8).

7. The multi-compressor system (7) according to claim 1 or 2, wherein, At least one of the balance connection lines (19) includes a first tubular connection component (36) connected to the common oil balance line (18) and a second tubular connection component (37) connected to the oil balance connection part (21) of the corresponding compressor (8), with a corresponding spring-loaded normally open valve (25) disposed between the first tubular connection component (36) and the second tubular connection component (37).

8. The multi-compressor system (7) according to claim 1 or 2, wherein, Each spring-loaded normally open valve (25) includes: Fluid flow channel (27); Valve seat (28), the valve seat (28) surrounding the corresponding fluid flow passage (27); and Valve component (29), which is movable between a closed position and an open position, In the closed position, the valve member (29) abuts against the corresponding valve seat (28) and at least partially closes the corresponding fluid flow passage (27). In the open position, the valve component (29) is away from the corresponding valve seat (28) and the corresponding fluid flow passage (27) is opened.

9. The multi-compressor system (7) according to claim 8, wherein, Each valve component (29) includes an oil passage hole (34) configured to prevent excessive oil accumulation in the oil sump (13) of the corresponding compressor (8) when the compressor (8) is shut down.

10. The multi-compressor system (7) according to claim 9, wherein, Each oil passage hole (34) is arranged in the lower part of the corresponding valve component (29).

11. The multi-compressor system (7) according to claim 8, wherein, Each spring-loaded normally open valve (25) also includes a mounting component (26) which is provided with a corresponding valve seat (28) and attached to a corresponding balance connection line (19) or a corresponding oil balance connection (21).

12. The multi-compressor system (7) according to claim 8, wherein, Each valve component (29) is pivotally mounted around the pivot axis (A).

13. The multi-compressor system (7) according to claim 1 or 2, wherein, Each of the plurality of compressors (8) is a scroll compressor.

14. A refrigeration system (2) comprising a refrigerant circulation loop (3), wherein, The refrigerant circulation loop (3) includes, in sequence, a condenser (4), an expansion device (5), an evaporator (6), and a multi-compressor system (7) according to any one of claims 1 to 13 connected in series.

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