MULTIPLE-COMPRESSOR SYSTEM

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit and priority of INSN202321071933, filed Oct. 20, 2023. The entire disclosure of the above application is incorporated herein by reference.

FIELD

The present disclosure relates to a climate-control system, and more particularly, to a multiple-compressor system.

BACKGROUND

This section provides background information related to the present disclosure and is not necessarily prior art.

A climate-control system such as, for example, a heat-pump system, a refrigeration system, or an air conditioning system, may include a fluid circuit having an outdoor heat exchanger, an indoor heat exchanger, an expansion device disposed between the indoor and outdoor heat exchangers, and one or more compressors circulating a working fluid (e.g., a refrigerant) between the indoor and outdoor heat exchangers. During operation of a multiple-compressor system, an oil level in one or more of the compressors may decrease while an oil level in another one or more of the compressors may increase. The present disclosure provides means for and method steps for equalizing the oil levels between the multiple compressors and/or reducing (or eliminating) an oil deficit in one or more of the compressors. Maintaining adequate oil levels in the compressors will improve efficiency and reliability of the compressors and will enable the climate-control system to effectively and efficiently provide a cooling and/or heating effect on demand.

SUMMARY

This section provides a general summary of the disclosure and is not a comprehensive disclosure of its full scope or all of its features.

In one form, the present disclosure provides a climate-control system that may include a first compressor, a second compressor, a suction manifold, and a pressure-control flow path. The first compressor may include a first shell and a first compression mechanism. The first shell may include a first suction inlet through which working fluid is drawn into the first compressor for compression in the first compression mechanism. The second compressor may include a second shell and a second compression mechanism. The second shell may include a second suction inlet through which working fluid is drawn into the second compressor for compression in the second compression mechanism. The suction manifold may have a first arm and a second arm. The first arm may be coupled to the first suction inlet and may be configured to provide working fluid to the first suction inlet. The second arm may be coupled to the second suction inlet and may be configured to provide working fluid to the second suction inlet. The pressure-control flow path may be coupled to a discharge-pressure region of the climate-control system and to a suction-pressure region of the second compressor. The pressure-control flow path may include a conduit and a valve (e.g., a solenoid valve or an expansion valve, for example) that provide working fluid to the suction-pressure region of the second compressor at a pressure that is higher than pressure of working fluid in the first arm of the suction manifold.

In some configurations of the climate-control system of the above paragraph, the valve is movable between a first position in which fluid flow through the pressure-control flow path is prevented and a second position in which fluid flow through the pressure-control flow path is allowed.

In some configurations of the climate-control system of either of the above paragraphs, the pressure-control flow path includes an expansion device.

In some configurations of the climate-control system of any one or more of the above paragraphs, the climate-control system includes a control module in communication with the valve and controlling a position of the valve to control lubricant levels in the first and second shells.

In some configurations of the climate-control system of any one or more of the above paragraphs, the control module controls the position of the valve based on which of the first and second compressors are operating and which are in a shutdown state.

In some configurations of the climate-control system of any one or more of the above paragraphs, the control module controls the position of the valve based on capacity levels of the first and second compressors.

In some configurations of the climate-control system of any one or more of the above paragraphs, the control module controls the position of the valve based on data received from a high-side sensor and a low-side sensor.

In some configurations of the climate-control system of any one or more of the above paragraphs, the position of the valve is determined based on a predefined operating-envelope map.

In some configurations of the climate-control system of any one or more of the above paragraphs, the first shell includes a first discharge outlet through which working fluid from the first compression mechanism is discharged from the first compressor; the second shell includes a second discharge outlet through which working fluid from the second compression mechanism is discharged from the second compressor; and the climate-control system includes a discharge conduit in fluid communication with the first and second discharge outlets and is configured to receive working fluid discharged from the first and second compressors.

In some configurations of the climate-control system of any one or more of the above paragraphs, a first portion of the working fluid discharged from the second compression mechanism bypasses the discharge conduit and flows from the second compression mechanism to the pressure-control flow path; and a second portion of the working fluid discharged from the second compression mechanism bypasses the pressure-control flow path and flows to the discharge conduit.

In some configurations of the climate-control system of any one or more of the above paragraphs, the pressure-control flow path extends from the second shell of the second compressor to the second arm of the suction manifold.

In some configurations of the climate-control system of any one or more of the above paragraphs, wherein the pressure-control flow path extends from a first portion of the second shell defining a discharge chamber within the second shell to a second portion of the second shell defining a suction chamber of the second shell.

In some configurations of the climate-control system of any one or more of the above paragraphs, the climate-control system includes a first discharge tube that fluidly connects the first discharge outlet with the discharge conduit; the climate-control system includes a second discharge tube that fluidly connects the second discharge outlet with the discharge conduit; and the pressure-control flow path extends from the second discharge tube to the second arm of the suction manifold.

In some configurations of the climate-control system of any one or more of the above paragraphs, the climate-control system includes a first heat exchanger that receives working fluid from the discharge conduit; the climate-control system includes an expansion device that receives working fluid from the first heat exchanger; the climate-control system includes a second heat exchanger that receives working fluid from the expansion device; the expansion device is disposed fluidly between the first and second heat exchangers; a first portion of the working fluid discharged from the second compression mechanism bypasses the expansion device and the second heat exchanger and flows from the second compression mechanism to the pressure-control flow path and back to the second compression mechanism; and a second portion of the working fluid discharged from the second compression mechanism bypasses the pressure-control flow path and flows to the first heat exchanger, the expansion device and the second heat exchanger.

In some configurations of the climate-control system of any one or more of the above paragraphs, the pressure-control flow path extends from the discharge conduit to a portion of the second shell that defines a suction chamber of the second shell.

In some configurations of the climate-control system of any one or more of the above paragraphs, the pressure-control flow path extends from a location between the first heat exchanger and the expansion device.

In some configurations of the climate-control system of any one or more of the above paragraphs, the pressure-control flow path extends to the second arm of the suction manifold.

In some configurations of the climate-control system of any one or more of the above paragraphs, the pressure-control flow path extends to a portion of the second shell that defines a suction chamber of the second shell.

In some configurations of the climate-control system of any one or more of the above paragraphs, the first portion of the working fluid discharged from the second compression mechanism bypasses the first heat exchanger.

In some configurations of the climate-control system of any one or more of the above paragraphs, the climate-control system includes a third heat exchanger including a first conduit and a second conduit in a heat transfer relationship with the first conduit; the first conduit fluidly connects the first heat exchanger and the expansion device; the second conduit fluidly connects the first heat exchanger and the pressure-control flow path; and the first and second conduits are fluidly isolated from each other.

Further areas of applicability will become apparent from the description provided herein. The description and specific examples in this summary are intended for purposes of illustration only and are not intended to limit the scope of the present disclosure.

DRAWINGS

The drawings described herein are for illustrative purposes only of selected embodiments and not all possible implementations and are not intended to limit the scope of the present disclosure.

FIG. 1 is a schematic representation of a climate-control system according to the principles of the present disclosure;

FIG. 2 is a schematic representation of a portion of the climate-control system of FIG. 1;

FIG. 3 is a diagram depicting a control module of the climate-control system in communication with sensors and a valve of the climate-control system;

FIG. 4 is a perspective view of first and second compressors and a pressure-control flow path of the climate-control system;

FIG. 5 is a flowchart showing steps performed by the control module to control the valve of the pressure-control flow path;

FIG. 6 is an example operating-envelope map according to the principles of the present disclosure;

FIG. 7 is a perspective view of the first and second compressors and an alternative pressure-control flow path;

FIG. 8 is a perspective view of the first and second compressors and another alternative pressure-control flow path;

FIG. 9 is a perspective view of the first and second compressors and yet another alternative pressure-control flow path;

FIG. 10 is a perspective view of the first and second compressors and yet another alternative pressure-control flow path;

FIG. 11 is a perspective view of the first and second compressors and yet another alternative pressure-control flow path;

FIG. 12 is a perspective view of the first and second compressors and yet another alternative pressure-control flow path;

FIG. 13 is a schematic representation of another climate-control system according to the principles of the present disclosure;

FIG. 14 is a perspective view of first and second compressors and a pressure-control flow path of the climate-control system of FIG. 13;

FIG. 15 is a perspective view of first and second compressors and an alternative pressure-control flow path of the climate-control system of FIG. 13; and

FIG. 16 is a schematic representation of yet another climate-control system according to the principles of the present disclosure.

Corresponding reference numerals indicate corresponding parts throughout the several views of the drawings.

DETAILED DESCRIPTION

Example embodiments will now be described more fully with reference to the accompanying drawings.

Example embodiments are provided so that this disclosure will be thorough and will fully convey the scope to those who are skilled in the art. Numerous specific details are set forth such as examples of specific components, devices, and methods, to provide a thorough understanding of embodiments of the present disclosure. It will be apparent to those skilled in the art that specific details need not be employed, that example embodiments may be embodied in many different forms and that neither should be construed to limit the scope of the disclosure. In some example embodiments, well-known processes, well-known device structures, and well-known technologies are not described in detail.

The terminology used herein is for the purpose of describing particular example embodiments only and is not intended to be limiting. As used herein, the singular forms “a,” “an,” and “the” may be intended to include the plural forms as well, unless the context clearly indicates otherwise. The terms “comprises,” “comprising,” “including,” and “having,” are inclusive and therefore specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof. The method steps, processes, and operations described herein are not to be construed as necessarily requiring their performance in the particular order discussed or illustrated, unless specifically identified as an order of performance. It is also to be understood that additional or alternative steps may be employed.

When an element or layer is referred to as being “on,” “engaged to,” “connected to,” or “coupled to” another element or layer, it may be directly on, engaged, connected or coupled to the other element or layer, or intervening elements or layers may be present. In contrast, when an element is referred to as being “directly on,” “directly engaged to,” “directly connected to,” or “directly coupled to” another element or layer, there may be no intervening elements or layers present. Other words used to describe the relationship between elements should be interpreted in a like fashion (e.g., “between” versus “directly between,” “adjacent” versus “directly adjacent,” etc.). As used herein, the term “and/or” includes any and all combinations of one or more of the associated listed items.

Although the terms first, second, third, etc. may be used herein to describe various elements, components, regions, layers and/or sections, these elements, components, regions, layers and/or sections should not be limited by these terms. These terms may be only used to distinguish one element, component, region, layer or section from another region, layer or section. Terms such as “first,” “second,” and other numerical terms when used herein do not imply a sequence or order unless clearly indicated by the context. Thus, a first element, component, region, layer or section discussed below could be termed a second element, component, region, layer or section without departing from the teachings of the example embodiments.

Spatially relative terms, such as “inner,” “outer,” “beneath,” “below,” “lower,” “above,” “upper,” and the like, may be used herein for ease of description to describe one element or feature's relationship to another element(s) or feature(s) as illustrated in the figures. Spatially relative terms may be intended to encompass different orientations of the device in use or operation in addition to the orientation depicted in the figures. For example, if the device in the figures is turned over, elements described as “below” or “beneath” other elements or features would then be oriented “above” the other elements or features. Thus, the example term “below” can encompass both an orientation of above and below. The device may be otherwise oriented (rotated 90 degrees or at other orientations) and the spatially relative descriptors used herein interpreted accordingly.

With reference to FIG. 1, a climate-control system 10 is provided that may include a first compressor 12, a second compressor 14, a first heat exchanger (e.g., a condenser or gas cooler) 16, an expansion device (e.g., an expansion valve or capillary tube) 18, a second heat exchanger (e.g., an evaporator) 20, and a pressure-control flow path 21. The climate-control system 10 may be a refrigeration system, an air-conditioning system, a heat-pump system, etc. While the climate-control system 10 shown in FIG. 1 includes two compressors, in some configurations, the climate-control system 10 may include more than two compressors.

Referring now to FIG. 2, each of the first and second compressors 12, 14 may include a shell 22, a motor 24, and a compression mechanism 26. The shell 22 defines a compressor housing in which the motor 24 and compression mechanism 26 are disposed. The shell 22 may include a partition 28 that separates a suction chamber 30 from a discharge chamber 32. A discharge outlet 34 may be attached to the shell 22 and may receive compressed working fluid (refrigerant) from the discharge chamber 32. The partition 28 may include a discharge passage 38 that provides fluid communication between the compression mechanism 26 and the discharge chamber 32. The shell 22 includes a suction inlet 36 that may provide working fluid to the suction chamber 30.

A suction manifold 39 may be fluidly coupled to the suction inlets 36 of both of the compressors 12, 14. The suction manifold 39 may include an inlet 40, a first arm 41, and a second arm 42. The inlet 40 of the suction manifold 39 may receive working fluid from a suction conduit 56. The first arm 41 may extend from the inlet 40 to the suction inlet 36 of the first compressor 12 and fluidly connects the inlet 40 with the suction inlet 36 of the first compressor 12. The second arm 42 of the suction manifold 39 may extend from the inlet 40 to the suction inlet 36 of the second compressor 14 and fluidly connects the inlet 40 with the suction inlet 36 of the second compressor 14. In this manner, working fluid from the inlet 40 can flow to the first compressor 12 via the first arm 41 and to the second compressor 14 via the second arm 42.

As shown in FIG. 2, a lower end of the shell 22 of each of the compressors 12, 14 may define a lubricant sump 46 containing a volume of liquid lubricant (e.g., oil). A lubricant equalization conduit 48 may extend between the first and second compressor 12, 14 and may be fluidly coupled with oil fittings attached to the shells 22 such that the lubricant equalization conduit 48 is in fluid communication with the lubricant sumps 46 of both of the compressors 12, 14 (i.e., so that lubricant can flow between the lubricant sumps 46 of the first and second compressors 12, 14 through the lubricant equalization conduit 48). A gas equalization conduit 49 may extend between the first and second compressor 12, 14 and may be fluidly coupled with fittings attached to the shells 22 such that the gas equalization conduit 49 is in fluid communication with the suction chambers 30 of both of the compressors 12, 14.

The motor 24 (FIG. 2) of each compressor 12, 14 may include a stator and a rotor. The stator may be press fit into the shell 22, for example. The rotor may be fixed to a driveshaft 50, and the driveshaft 50 may drive the compression mechanism 26. The compression mechanism 26 may be a scroll compression mechanism including first and second scrolls (e.g., an orbiting scroll and a non-orbiting scroll or a pair of co-rotating scrolls) that include spiral wraps that cooperate to define compression pockets therebetween. It will be appreciated that the compression mechanism 26 could be any other type of compression mechanism, such as a rotary compression mechanism (e.g., with an eccentric rotor rotating within a cylinder, and with a reciprocating vane extending into the cylinder) or a reciprocating compression mechanism (e.g., with a piston reciprocating within a cylinder), for example.

The first compressor 12 may be operable at a lower capacity than the second compressor 14. In some examples, one or both of the compressors 12, 14 may be variable-capacity compressors. That is, one or both of the compressors 12, 14 could be or include one or more of: a multi-stage compression mechanism, a multi-speed or variable-speed motor, a vapor-injection system (e.g., an economizer circuit), a pulse-width-modulated scroll compressor configured for scroll separation (e.g., a digital scroll compressor), and a compressor having capacity-modulation valves configured to leak intermediate-pressure working fluid. It will be appreciated that one or both of the compressors 12, 14 could include any other additional or alternative structure for varying its capacity and/or the operating capacity of the climate-control system 10. Example variable-capacity compressors are disclosed in Assignee's commonly owned U.S. Pat. Nos. 8,616,014, 6,679,072, 8,585,382, 6,213,731, 8,485,789, and 8,459,053, the disclosures of which are hereby incorporated by reference. A control module 52 (FIG. 3) may control operation of the compressors 12, 14, including starting up the compressors 12, 14, shutting down the compressors 12, 14, and adjusting or modulating the capacities of the compressors 12, 14.

The pressure-control flow path 21 may include an expansion device (e.g., a capillary tube 45 or an expansion valve). The pressure-control flow path 21 may also include a valve 43. In the configuration shown in the figures, the pressure-control flow path 21 includes the valve 43 and the capillary tube 45. In some configurations, the pressure-control flow path 21 may include the valve 43 without the expansion device.

The valve 43 can be a solenoid valve, for example, or any suitable type of valve (e.g., an electromechanical, pneumatic, or hydraulic valve). The valve 43 is fluidly coupled with and controls fluid flow through the pressure-control flow path 21. That is, the valve 43 may be movable between: (i) a first position in which the valve 43 prevents fluid flow through the pressure-control flow path 21, and (ii) a second position in which the valve 43 allows fluid flow through the pressure-control flow path 21. In some configurations, the valve 43 is movable to more than two positions to adjust the amount of fluid flow through the pressure-control flow path 21.

The pressure-control flow path 21 may be fluidly coupled with a high-side or discharge-pressure region of the climate-control system 10 (e.g., a portion of the climate-control system 10 at which the working fluid is at or near a discharge pressure such as the discharge chamber 32, discharge outlet 34, discharge tube 35, discharge conduit 54, or a location downstream of the first heat exchanger 16 and upstream of the expansion device 18, for example) and a suction-pressure region (e.g., the suction chamber 30 and/or the second arm 42 of the suction manifold 39) of the second compressor 14 to selectively raise the pressure of working fluid in the suction-pressure region of the second compressor 14 to force oil to flow (via the lubricant equalization conduit 48) from the lubricant sump 46 of the second compressor 14 to the lubricant sump 46 of the first compressor 12. For example, as shown in FIGS. 1, 2, and 4, the pressure-control flow path 21 may extend from the discharge chamber 32 of the second compressor 14 to the second arm 42 of the suction manifold 39. In the configuration shown in FIGS. 1, 2, and 4, the pressure-control flow path 21 may include a conduit 47 that is connected to the valve 43 and to the shell 22 (e.g., an end cap 23 that defines the discharge chamber 32) of the second compressor 14 and is in fluid communication with the valve 43 and the discharge chamber 32 of the second compressor 14. The capillary tube 45 is fluidly connected to the valve 43 and to the second arm 42 of the suction manifold 39. The valve 43 is movable between the first and second positions to control fluid flow through the pressure-control flow path 21 (i.e., to control the flow of working fluid from the discharge chamber 32 of the second compressor 14 to the second arm 42 of the suction manifold 39.

Referring now to FIGS. 1 and 2, during operation of the climate-control system 10, the compression mechanism 26 of one or both of the compressors 12, 14 may draw suction-pressure working fluid (e.g., refrigerant, carbon dioxide, etc.) from their respective suction chambers 30, may compress the working fluid to a higher pressure, and may discharge the compressed working fluid into their respective discharge chambers 32. The compressed working fluid in the discharge chambers 32 of the compressors 12, 14 may flow through the discharge outlets 34 and into a discharge conduit 54 via respective discharge outlet tubes 35 of the first and second compressors 12, 14. The discharge outlet 34 of the first compressor 12 is connected to the discharge conduit 54 via a discharge outlet tube 35, and the discharge outlet 34 of the second compressor 14 is connected to the discharge conduit 54 via another discharge outlet tube 35.

Working fluid in the discharge conduit 54 may flow through the first heat exchanger 16 where heat is absorbed from the working fluid. From the first heat exchanger 16, the working fluid may flow through the expansion device 18. The pressure and temperature of the working fluid drop as the working fluid flows through the expansion device 18. From the expansion device 18, the working fluid may flow through the second heat exchanger 20, where the working fluid absorbs heat from a space to be cooled. From the second heat exchanger 20, the working fluid flows to the inlet 40 of the suction manifold 39 via the suction conduit 56. From the inlet 40 of the suction manifold 39, working fluid may flow into the suction inlet 36 of one or both of the compressors 12, 14 (via respective arms 41, 42 of the suction manifold 39).

When the valve 43 is positioned to allow fluid flow through the pressure-control flow path 21 (e.g., when the valve 43 is in the second position described above), a portion of the working fluid in the discharge chamber 32 of the second compressor 14 may exit the second compressor 14 through the conduit 47 (thereby allowing this portion of the working fluid to bypass the heat exchangers 16, 20 and expansion device 18). Another portion of the working fluid in the discharge chamber 32 of the second compressor 14 may exit the second compressor 14 through the discharge outlet 34 and may flow to the first heat exchanger 16, as described above. The portion of the working fluid in the discharge chamber 32 of the second compressor 14 exiting the second compressor 14 through the conduit 47 may flow through the valve 43, through the capillary tube 45, into the second arm 42 of the suction manifold 39, and into the suction chamber 30 of the second compressor 14. As described above, the valve 43 controls the flow of working fluid through the pressure-control flow path 21 from the discharge chamber 32 of the second compressor 14 to the suction chamber 30 of the second compressor 14.

The control module 52 (FIG. 3) may be in communication with the valve 43 and may control operation of the valve 43 to equalize (or reduce differences between) the pressures of fluid within the suction chambers 30 of the first and second compressors 12, 14. Equalizing the pressures of fluid within the suction chambers 30 of the first and second compressors 12, 14 maintains a balance of lubricant (i.e., equalizes lubricant levels) in the sumps 46 of the first and second compressors 12, 14. This prevents the lubricant level within either of the compressors 12, 14 from getting too low so that both compressors 12, 14 remain adequately lubricated. For example, the control module 52 may control the valve 43 to maintain lubricant levels 58 in the lubricant sumps 46 of both of the first and second compressors 12, 14 vertically above the lubricant equalization conduit 48, as shown in FIG. 2.

As noted above, the valve 43 can be any suitable type of valve that can be movable among the first position (preventing fluid flow through the pressure-control flow path 21) and the second position (allowing fluid flow through the pressure-control flow path 21). In some configurations, the valve 43 may be movable to one or more intermediate positions between the first and second positions to allow a desired amount of fluid flow through the pressure-control flow path 21. The valve 43 could be a ball valve, a butterfly valve, or any other type of valve driven by a solenoid, stepper motor, or any other suitable actuator.

In some configurations, the control module 52 may control the valve 43 based on operating parameters of the climate-control system 10. For example, the control module 52 may control the valve 43 based on information received from a first sensor 60 and/or a second sensor 62 (FIG. 1). In some configurations, the first sensor 60 may be a high-side sensor (e.g., a temperature or pressure sensor disposed along the discharge conduit 54) and the second sensor 62 may be a low-side sensor (e.g., a temperature or pressure sensor disposed along the suction conduit 56).

The control module 52 can perform the steps shown in FIG. 5 to intermittently or continuously adjust the position of the valve 43 based on operating conditions of the compressors 12, 14 and/or the climate-control system 10 to equalize the pressures of fluid within the suction chambers 30 of the first and second compressors 12, 14 and/or to force oil to flow from the sump 46 of one of the compressors 12, 14 to the sump 46 of the other one of the compressors 12, 14 via the lubricant equalization conduit 48.

As shown in FIG. 5, the control module 52 may, at step 110, receive a high-side temperature value (or high-side pressure value) from the high-side sensor 60 (FIGS. 1 and 3) and a low-side temperature value (or low-side pressure value) from the low-side sensor 62 (FIGS. 1 and 3). The high-side sensor 60 may be a temperature sensor (or pressure sensor) disposed along the discharge conduit 54 or on the first heat exchanger 16, for example. Therefore, the high-side temperature value may be a discharge temperature or a condensing temperature. The low-side sensor 62 may be a temperature sensor (or pressure sensor) disposed along the suction conduit 56 or on the second heat exchanger 20, for example. Therefore, the low-side temperature value may be a suction temperature or an evaporating temperature.

At step 120, the control module 52 may identify which one or ones of the compressors 12, 14 are currently operating (i.e., which compressors 12, 14 are not in a shutdown state). This can be done in a variety of ways, including, for example, reading electrical current values from sensors measuring electrical current draw of the motors 24 of the compressors 12, 14, reading pressure and/or temperature values from sensors at or near the discharge and/or suction inlets 34, 36 of the compressors 12, 14, and/or referencing the status of other algorithms that the control module 52 performs for controlling, diagnosing and/or protecting the compressors 12, 14. In some configurations, additional or alternative means or steps may be employed by the control module 52 to identify which one or ones of the compressors 12, 14 are currently operating.

At step 130, the control module 52 may identify a modulation state or capacity level of the one or more compressors 12, 14 that were identified at step 120 as currently operating. That is, at step 130, the control module 52 may identify, for each compressor 12, 14 currently operating, whether the compressor(s) 12, 14 are operating at zero capacity, full capacity, or an intermediate capacity level between zero and full. The control module 52 may also identify the value of the intermediate capacity level at which one or more of the compressors 12, 14 may be currently operating. Identifying the capacity levels of the compressors 12, 14 that are operating may be done in a variety of ways, including, for example, reading electrical current values from sensors measuring electrical current draw of the motors 24 of the compressors 12, 14, reading pressure and/or temperature values from sensors at or near the discharge and/or suction inlets 34, 36 of the compressors 12, 14, and/or referencing the status of other algorithms that the control module 52 performs for controlling, diagnosing and/or protecting the compressors 12, 14. In some configurations, additional or alternative means or steps may be employed by the control module 52 to identify the capacity levels of the compressors 12, 14 that are operating.

One or more predefined operating-envelope maps may be stored within a memory of the control module 52 or the memory of a module in communication with the control module 52. FIG. 6 depicts an example of an operating-envelope map 135 that could be included in the plurality of predefined operating-envelope maps. The operating-envelope maps stored in the memory may include additional or different operating-envelope maps that correspond to the different combinations of information that could be identified by the control module 52 at steps 120 and 130.

At step 140, the control module 52 may identify one of the operating-envelope maps corresponding to: (a) the identified number of operating compressors 12, 14 (identified in step 120), and (b) the identified modulation state (capacity level) of the operating compressor(s) 12, 14. For example, if the control module 52 determines at steps 120 and 130 that both of the compressors 12, 14 are currently operating and are both operating at an intermediate capacity level, then the control module 52 may identify, at step 140, the one of the operating-envelope maps (such as the operating-envelope map 135 shown in FIG. 6) that corresponds to such conditions. As another example, if the control module 52 determines at steps 120 and 130 that both of the compressors 12, 14 are currently operating and the first compressor 12 is operating at an intermediate capacity level and the second compressor 14 is operating at a full capacity level, then the control module 52 may identify, at step 140, the one of the operating-envelope maps (such as an operating-envelope map different from the operating-envelope map 135 shown in FIG. 6) that corresponds to such conditions. Stored in the memory may be a variety of operating-envelope maps that correspond to different combinations of conditions identified at steps 120, 130.

Once the operating-envelope map that corresponds to the current conditions (i.e., the conditions identified at steps 120, 130) has been identified (at step 140), then the control module 52 may, at step 150, read the valve position on the identified operating-envelope map based on the low-side temperature (e.g., suction or evaporating temperature) value and the high-side temperature (e.g., discharge or condensing temperature) value received at step 110. The operating-envelope maps each include a plurality of regions, and each of the regions corresponds to different valve positions.

For example, the operating-envelope map 135 shown in FIG. 6 includes a first region labeled “Zone A” corresponding to the first position of the valve 43 (in which fluid flow through the pressure-control flow path 21 is prevented), and a second region labeled “Zone B” corresponding to the second position of the valve 43 (in which fluid flow through the pressure-control flow path 21 is allowed). Therefore, if the temperature values received at step 110 fall within the first region (Zone A), then the control module 52 will, at step 150, determine that the valve 43 should be moved to (or remain in) the first position. If the temperature values received at step 110 fall within the second region (Zone B), then the control module 52 will, at step 150, determine that the valve 43 should be moved to (or remain in) the second position. Valve positions can be determined in the same manner from other operating-envelope maps stored in the memory.

At step 160, the control module 52 may move the valve 43 to the valve position read at step 150. Moving the valve 43 to the position read at step 150 will equalize the pressures of fluid within the suction chambers 30 of the first and second compressors 12, 14 so that the lubricant levels in the first and second compressors 12, 14 can be maintained at approximately equal levels or at least at acceptable levels. The operating-envelope maps and the valve position values for each of the regions may be determined and plotted based on testing for a given climate-control system. That is, during testing of a given climate-control system, the valve position values may be set so that pressures of fluid within the suction chambers 30 of the first and second compressors 12, 14 are kept approximately equal.

After performing step 160, the control module 52 may loop back and perform steps 110-160 either continuously or intermittently. It will be appreciated that step 110 need not be performed before steps 120, 130, 140. Step 110 could be performed concurrently with any of steps 120, 130, 140 or after any of steps 120, 130, 140.

In some configurations, the control module 52 may trigger a fault alert and/or a compressor protection algorithm if adequate lubricant levels are not being maintained in the compressors 12, 14.

Referring now to FIG. 7, another pressure-control flow path 221 is provided that may replace the pressure-control flow path 21 described above in the climate-control system 10. The structure and function of the pressure-control flow path 221 may be similar or identical to that of the pressure-control flow path 21 described above, apart from differences described below and shown in the figures.

Like the pressure-control flow path 21, the pressure-control flow path 221 may include an expansion device (e.g., capillary tube 245 similar or identical to capillary tube 45), a valve 243 (similar or identical to valve 43), and a conduit 247 (similar or identical to conduit 47). The pressure-control flow path 221 may extend from the discharge chamber 32 of the second compressor 14 to the suction chamber 30 of the second compressor 14 (e.g., allowing a portion of the working fluid discharged from the compression mechanism 26 of the second compressor 14 to bypass the heat exchangers 16, 20 and expansion device 18 and be returned to the suction chamber 30 of the second compressor 14). As shown in FIG. 7, the capillary tube 245 is fluidly connected to the shell 22 of the second compressor 14 (e.g., the end cap 23 of the shell 22) and is in fluid communication with the valve 243 and the discharge chamber 32 of the second compressor 14. The conduit 247 is connected to the valve 243 and the shell 22 of the second compressor 14 and is in fluid communication with the valve 243 and the suction chamber 30 of the second compressor 14. The valve 243 may be controlled by the control module 52 in the same or similar manner as described above (e.g., by executing the steps 110-160 shown in FIG. 5). In the configuration shown in FIG. 7, when the valve 243 is in the second position (i.e., to allow fluid flow through the pressure-control flow path 221), fluid flows from the discharge chamber 32 of the second compressor 14 through the capillary tube 245, through the valve 243, through the conduit 247, and into the suction chamber 30 of the second compressor 14.

Referring now to FIG. 8, another pressure-control flow path 321 is provided that may replace the pressure-control flow path 21, 221 described above in the climate-control system 10. The structure and function of the pressure-control flow path 321 may be similar or identical to that of the pressure-control flow path 21, 221 described above, apart from differences described below and shown in the figures.

Like the pressure-control flow path 221, the pressure-control flow path 321 may include an expansion device (e.g., capillary tube 345 similar or identical to capillary tube 45), a valve 343 (similar or identical to valve 43), and a conduit 347 (similar or identical to conduit 47). The pressure-control flow path 321 may extend from the discharge chamber 32 of the second compressor 14 to the suction chamber 30 of the second compressor 14 (e.g., allowing a portion of the working fluid discharged from the compression mechanism 26 of the second compressor 14 to bypass the heat exchangers 16, 20 and expansion device 18 and be returned to the suction chamber 30 of the second compressor 14). As shown in FIG. 8, the capillary tube 345 is fluidly connected to the shell 22 of the second compressor 14 and is in fluid communication with the valve 343 and the suction chamber 30 of the second compressor 14. The conduit 347 is connected to the valve 343 and end cap 23 of the shell 22 of the second compressor 14 and is in fluid communication with the valve 343 and the discharge chamber 32 of the second compressor 14. The valve 343 may be controlled by the control module 52 in the same or similar manner as described above (e.g., by executing the steps 110-160 shown in FIG. 5). In the configuration shown in FIG. 8, when the valve 343 is in the second position (i.e., to allow fluid flow through the pressure-control flow path 321), fluid flows from the discharge chamber 32 of the second compressor 14 through the conduit 347, through the valve 343, through the capillary tube 345, and into the suction chamber 30 of the second compressor 14.

In some configurations, an outlet of the pressure-control flow path 321 (e.g., an outlet of the capillary tube 345) may be connected to the shell 22 at a location that is at the same or similar vertical height as the lubricant equalization conduit 48 (e.g., so that working fluid enters the second compressor 14 from the pressure-control flow path 321 beneath the surface of the oil in the sump 46 (beneath lubricant level 58)) of the second compressor 14.

Referring now to FIG. 9, another pressure-control flow path 421 is provided that may replace the pressure-control flow path 21, 221, 321 described above in the climate-control system 10. The structure and function of the pressure-control flow path 421 may be similar or identical to that of the pressure-control flow path 21, 221, 321 described above, apart from differences described below and shown in the figures.

Like the pressure-control flow path 21, the pressure-control flow path 421 may include an expansion device (e.g., capillary tube 445 similar or identical to capillary tube 45), a valve 443 (similar or identical to valve 43), and a conduit 447 (similar or identical to conduit 47). The pressure-control flow path 421 may extend from the discharge outlet tube 35 of the second compressor 14 to the second arm 42 of the suction manifold 39 (e.g., allowing a portion of the working fluid discharged from the compression mechanism 26 of the second compressor 14 to bypass the heat exchangers 16, 20 and expansion device 18 and be returned to the suction chamber 30 of the second compressor 14). As shown in FIG. 9, the conduit 447 is fluidly connected to discharge outlet tube 35 of the second compressor 14 and is in fluid communication with the valve 443 and the discharge chamber 32 of the second compressor 14. The capillary tube 445 is connected to the valve 443 and the second arm 42 of the suction manifold 39 and is in fluid communication with the valve 443 and the suction chamber 30 of the second compressor 14. The valve 443 may be controlled by the control module 52 in the same or similar manner as described above (e.g., by executing the steps 110-160 shown in FIG. 5). In the configuration shown in FIG. 9, when the valve 443 is in the second position (i.e., to allow fluid flow through the pressure-control flow path 421), fluid flows from the discharge chamber 32 of the second compressor 14 through the discharge outlet 34 of the second compressor 14, through the discharge outlet tube 35 of the second compressor 14, through the conduit 447, through the valve 443, through the capillary tube 445, into the second arm 42 of the suction manifold 39, and into the suction chamber 30 of the second compressor 14.

Referring now to FIG. 10, another pressure-control flow path 521 is provided that may replace the pressure-control flow path 21, 221, 321, 421 described above in the climate-control system 10. The structure and function of the pressure-control flow path 521 may be similar or identical to that of the pressure-control flow path 21, 221, 321, 421 described above, apart from differences described below and shown in the figures.

Like the pressure-control flow path 21, the pressure-control flow path 521 may include an expansion device (e.g., capillary tube 545 similar or identical to capillary tube 45), a valve 543 (similar or identical to valve 43), and a conduit 547 (similar or identical to conduit 47). The pressure-control flow path 521 may extend from the discharge chamber 32 of the second compressor 14 to the suction chamber 30 of the second compressor 14 (e.g., allowing a portion of the working fluid discharged from the compression mechanism 26 of the second compressor 14 to bypass the heat exchangers 16, 20 and expansion device 18 and be returned to the suction chamber 30 of the second compressor 14). As shown in FIG. 10, the capillary tube 545 is fluidly connected to the shell 22 of the second compressor 14 (e.g., at inlet fitting 560) and is in fluid communication with the valve 543 and the suction chamber 30 of the second compressor 14. The conduit 547 is connected to the valve 543 and end cap 23 of the shell 22 of the second compressor 14 and is in fluid communication with the valve 543 and the discharge chamber 32 of the second compressor 14. The valve 543 may be controlled by the control module 52 in the same or similar manner as described above (e.g., by executing the steps 110-160 shown in FIG. 5). In the configuration shown in FIG. 10, when the valve 543 is in the second position (i.e., to allow fluid flow through the pressure-control flow path 521), fluid flows from the discharge chamber 32 of the second compressor 14 through the conduit 547, through the valve 543, through the capillary tube 545, and into the suction chamber 30 of the second compressor 14. In some configurations, an outlet of the pressure-control flow path 521 (e.g., an outlet of the capillary tube 545) may be connected to the shell 22 at a location that is at the same or similar vertical height as the suction inlet 36 of the second compressor 14.

Referring now to FIG. 11, another pressure-control flow path 621 is provided that may replace the pressure-control flow path 21, 221, 321, 421, 521 described above in the climate-control system 10. The structure and function of the pressure-control flow path 621 may be similar or identical to that of the pressure-control flow path 21, 221, 321, 421, 521 described above, apart from differences described below and shown in the figures.

Like the pressure-control flow path 21, the pressure-control flow path 621 may include an expansion device (e.g., capillary tube 645 similar or identical to capillary tube 45), a valve 643 (similar or identical to valve 43), and a conduit 647 (similar or identical to conduit 47). The pressure-control flow path 621 may extend from the discharge outlet tube 35 of the second compressor 14 to the suction chamber 30 of the second compressor 14 (e.g., allowing a portion of the working fluid discharged from the compression mechanism 26 of the second compressor 14 to bypass the heat exchangers 16, 20 and expansion device 18 and be returned to the suction chamber 30 of the second compressor 14). As shown in FIG. 11, the capillary tube 645 is fluidly connected to the shell 22 of the second compressor 14 (e.g., at inlet fitting 660) and is in fluid communication with the valve 643 and the suction chamber 30 of the second compressor 14. The conduit 647 is connected to the valve 643 and the discharge outlet tube 35 of the second compressor 14 and is in fluid communication with the valve 643 and the discharge chamber 32 of the second compressor 14. The valve 643 may be controlled by the control module 52 in the same or similar manner as described above (e.g., by executing the steps 110-160 shown in FIG. 5). In the configuration shown in FIG. 11, when the valve 643 is in the second position (i.e., to allow fluid flow through the pressure-control flow path 621), fluid flows from the discharge chamber 32 of the second compressor 14 through the discharge outlet 34, into the discharge outlet tube 35, into the conduit 647, through the valve 643, through the capillary tube 645, and into the suction chamber 30 of the second compressor 14.

Referring now to FIG. 12, another pressure-control flow path 721 is provided that may replace the pressure-control flow path 21, 221, 321, 421, 521, 621 described above in the climate-control system 10. The structure and function of the pressure-control flow path 721 may be similar or identical to that of the pressure-control flow path 21, 221, 321, 421, 521, 621 described above, apart from differences described below and shown in the figures.

Like the pressure-control flow path 21, the pressure-control flow path 721 may include an expansion device (e.g., capillary tube 745 similar or identical to capillary tube 45), a valve 743 (similar or identical to valve 43), and a conduit 747 (similar or identical to conduit 47). The pressure-control flow path 721 may extend from the discharge conduit 54 to the suction chamber 30 of the second compressor 14 (e.g., allowing a portion of the working fluid discharged from the compression mechanism 26 of the second compressor 14 to bypass the heat exchangers 16, 20 and expansion device 18 and be returned to the suction chamber 30 of the second compressor 14). As shown in FIG. 12, the capillary tube 745 is fluidly connected to the discharge conduit 54 and the valve 743. The capillary tube 745 receives fluid from the discharge chamber 32 of the first and second compressors 12, 14. The conduit 747 is connected to the valve 743 and shell 22 of the second compressor 14 and is in fluid communication with the valve 743 and the suction chamber 30 of the second compressor 14. The valve 743 may be controlled by the control module 52 in the same or similar manner as described above (e.g., by executing the steps 110-160 shown in FIG. 5). In the configuration shown in FIG. 12, when the valve 743 is in the second position (i.e., to allow fluid flow through the pressure-control flow path 721), fluid flows from the discharge chamber 32 of the second compressor 14 through the discharge outlet 34, through the discharge outlet tube 35, into the discharge conduit 54, into the capillary tube 745, through the valve 743, through the conduit 747, and into the suction chamber 30 of the second compressor 14.

Referring now to FIGS. 13 and 14, another climate-control system 810 is provided. The structure and function of the climate-control system 810 may be similar or identical to that of the climate-control system 10 described above, apart from differences described below and shown in the drawings. Like the climate-control system 10, the system 810 may include the first compressor 12, the second compressor 14, the first heat exchanger (e.g., a condenser or gas cooler) 16, the expansion device (e.g., an expansion valve or capillary tube) 18, the second heat exchanger (e.g., an evaporator) 20, a pressure-control flow path 821 (the structure and function of which may be similar or identical to that of the pressure-control flow path 21, 221, 321, 421, 521, 621, 721, apart from differences described below), the suction manifold 39, the lubricant equalization conduit 48, and the gas equalization conduit 49.

The pressure-control flow path 821 may include an expansion device (e.g., a capillary tube 845 similar or identical to capillary tube 45), a valve 843 (similar or identical to valve 43), and a conduit 847 (similar or identical to conduit 47). As shown in FIG. 13, the pressure-control flow path 821 may extend from a first location 849 (e.g., an outlet of the first heat exchanger 16 or a location between the outlet of the first heat exchanger 16 and an inlet of the expansion device 18) to the suction chamber 30 of the second compressor 14 (e.g., allowing a portion of the working fluid discharged from the compression mechanisms 26 of the first and second compressors 12, 14 to bypass the expansion device 18 and second heat exchanger 20 and be returned to the suction chamber 30 of the second compressor 14). As shown in FIGS. 13 and 14, the capillary tube 845 is fluidly connected to the shell 22 of the second compressor 14 and is in fluid communication with the valve 843 and the suction chamber 30 of the second compressor 14. The conduit 847 is connected to the valve 843 and the location 849 and is in fluid communication with the valve 843 and the outlet of the first heat exchanger 16 (i.e., such that a portion of the fluid exiting the first heat exchanger 16 flows into the conduit 847). The valve 843 may be controlled by the control module 52 in the same or similar manner as described above (e.g., by executing the steps 110-160 shown in FIG. 5).

In the configuration shown in FIG. 13, fluid flows from the discharge chamber 32 of the second compressor 14 through the discharge outlet 34, through the discharge outlet tube 35, into the discharge conduit 54, through the first heat exchanger 16. When the valve 843 is in the second position (i.e., to allow fluid flow through the pressure-control flow path 821), a portion of the working fluid exiting the first heat exchanger flows to the expansion device 18 and second heat exchanger 20 and another portion of the working fluid exiting the first heat exchanger flows into the conduit 847, through the valve 843, through the capillary tube 845, and into the suction chamber 30 of the second compressor 14.

FIG. 15 shows an alternative pressure-control flow path 921 that could be incorporated into the climate-control system 810 instead of the pressure-control flow path 821. The structure and function of the pressure-control flow path 921 may be similar or identical to that of the pressure-control flow path 821 described above (e.g., including capillary tube 945, valve 943, and conduit 947), except the capillary tube 945 is connected to the second arm 42 of the suction manifold 39 (instead of being connected directly to the shell 22 of the second compressor 14).

Referring now to FIG. 16, another climate-control system 1010 is provided. The structure and function of the climate-control system 1010 may be similar or identical to that of the climate-control system 10, 810 described above, apart from differences described below and shown in the drawings. Like the climate-control system 10, 810 the system 1010 may include the first compressor 12, the second compressor 14, the first heat exchanger (e.g., a condenser or gas cooler) 16, the expansion device (e.g., an expansion valve or capillary tube) 18, the second heat exchanger (e.g., an evaporator) 20, a pressure-control flow path 1021 (the structure and function of which may be similar or identical to that of the pressure-control flow path 21, 221, 321, 421, 521, 621, 721, 821, 921 apart from differences described below), the suction manifold 39, the lubricant equalization conduit 48, and the gas equalization conduit 49. The climate-control system 1010 may also include another expansion device 1019 (e.g., a capillary tube or expansion valve) and a third heat exchanger 1022.

The third heat exchanger 1022 may include a first conduit 1024 and a second conduit 1026. The first and second conduits 1024, 1026 are in a heat transfer relationship with each other such that working fluid in the first conduit 1024 can be transferred to the working fluid in the second conduit 1026. The first conduit 1024 is fluidly connected to and disposed fluidly between the location 1049 and the expansion device 18. The second conduit 1026 is fluidly connected to and disposed fluidly between the location 1049 and the pressure-control flow path 1021. In this manner, a portion of the fluid exiting the first heat exchanger 16 may flow through the first conduit 1024 and another portion of the fluid exiting the first heat exchanger may flow through the second conduit 1026 (when valve 1043 of the pressure-control flow path 1021 is open (in the second position)).

The pressure-control flow path 1021 may include an expansion device (e.g., a capillary tube 1045 similar or identical to capillary tube 45), the valve 1043 (similar or identical to valve 43), and a conduit 1047 (similar or identical to conduit 47). As shown in FIG. 16, the pressure-control flow path 1021 may extend from the outlet of the second conduit 1026 of heat exchanger 1022 to the suction chamber 30 of the second compressor 14 (e.g., allowing a portion of the working fluid discharged from the compression mechanisms 26 of the first and second compressors 12, 14 to bypass the expansion device 18 and second heat exchanger 20 and be returned to the suction chamber 30 of the second compressor 14). As shown in FIG. 16, the capillary tube 1045 is fluidly connected to the shell 22 of the second compressor 14 and is in fluid communication with the valve 1043 and the suction chamber 30 of the second compressor 14. The conduit 1047 is connected to the valve 1043 and the outlet of the second conduit 1026 of heat exchanger 1022 and is in fluid communication with the valve 1043 and the second conduit 1026 (i.e., such that a portion of the fluid exiting the first heat exchanger 16 flows into the conduit 1047). The valve 1043 may be controlled by the control module 52 in the same or similar manner as described above (e.g., by executing the steps 110-160 shown in FIG. 5).

In this application, including the definitions below, the term “module” or the term “control module” may be replaced with the term “circuit.” The term “module” may refer to, be part of, or include: an Application Specific Integrated Circuit (ASIC); a digital, analog, or mixed analog/digital discrete circuit; a digital, analog, or mixed analog/digital integrated circuit; a combinational logic circuit; a field programmable gate array (FPGA); a processor circuit (shared, dedicated, or group) that executes code; a memory circuit (shared, dedicated, or group) that stores code executed by the processor circuit; other suitable hardware components that provide the described functionality; or a combination of some or all of the above, such as in a system-on-chip.

The module may include one or more interface circuits. In some examples, the interface circuits may include wired or wireless interfaces that are connected to a local area network (LAN), the Internet, a wide area network (WAN), or combinations thereof. The functionality of any given module of the present disclosure may be distributed among multiple modules that are connected via interface circuits. For example, multiple modules may allow load balancing. In a further example, a server (also known as remote, or cloud) module may accomplish some functionality on behalf of a client module.

The term code, as used above, may include software, firmware, and/or microcode, and may refer to programs, routines, functions, classes, data structures, and/or objects. The term shared processor circuit encompasses a single processor circuit that executes some or all code from multiple modules. The term group processor circuit encompasses a processor circuit that, in combination with additional processor circuits, executes some or all code from one or more modules. References to multiple processor circuits encompass multiple processor circuits on discrete dies, multiple processor circuits on a single die, multiple cores of a single processor circuit, multiple threads of a single processor circuit, or a combination of the above. The term shared memory circuit encompasses a single memory circuit that stores some or all code from multiple modules. The term group memory circuit encompasses a memory circuit that, in combination with additional memories, stores some or all code from one or more modules.

The term memory circuit is a subset of the term computer-readable medium. The term computer-readable medium, as used herein, does not encompass transitory electrical or electromagnetic signals propagating through a medium (such as on a carrier wave); the term computer-readable medium may therefore be considered tangible and non-transitory. Non-limiting examples of a non-transitory, tangible computer-readable medium are nonvolatile memory circuits (such as a flash memory circuit, an erasable programmable read-only memory circuit, or a mask read-only memory circuit), volatile memory circuits (such as a static random access memory circuit or a dynamic random access memory circuit), magnetic storage media (such as an analog or digital magnetic tape or a hard disk drive), and optical storage media (such as a CD, a DVD, or a Blu-ray Disc).

In this application, apparatus elements described as having particular attributes or performing particular operations are specifically configured to have those particular attributes and perform those particular operations. Specifically, a description of an element to perform an action means that the element is configured to perform the action. The configuration of an element may include programming of the element, such as by encoding instructions on a non-transitory, tangible computer-readable medium associated with the element.

The apparatuses and methods described in this application may be partially or fully implemented by a special-purpose computer created by configuring a general-purpose computer to execute one or more particular functions embodied in computer programs. The figures and descriptions above serve as software specifications, which can be translated into the computer programs by the routine work of a skilled technician or programmer.

The computer programs include processor-executable instructions that are stored on at least one non-transitory, tangible computer-readable medium. The computer programs may also include or rely on stored data. The computer programs may encompass a basic input/output system (BIOS) that interacts with hardware of the special purpose computer, device drivers that interact with particular devices of the special purpose computer, one or more operating systems, user applications, background services, background applications, etc.

The computer programs may include: (i) descriptive text to be parsed, such as HTML (hypertext markup language), XML (extensible markup language), or JSON (JavaScript Object Notation) (ii) assembly code, (iii) object code generated from source code by a compiler, (iv) source code for execution by an interpreter, (v) source code for compilation and execution by a just-in-time compiler, etc. As examples only, source code may be written using syntax from languages including C, C++, C#, Objective-C, Swift, Haskell, Go, SQL, R, Lisp, Java®, Fortran, Perl, Pascal, Curl, OCaml, Javascript®, HTML5 (Hypertext Markup Language 5th revision), Ada, ASP (Active Server Pages), PHP (PHP: Hypertext Preprocessor), Scala, Eiffel, Smalltalk, Erlang, Ruby, Flash®, Visual Basic®, Lua, MATLAB, SIMULINK, and Python®.

None of the elements recited in the claims are intended to be a means-plus-function element within the meaning of 35 U.S.C. § 112 (f) unless an element is expressly recited using the phrase “means for,” or in the case of a method claim using the phrases “operation for” or “step for.”

The foregoing description of the embodiments has been provided for purposes of illustration and description. It is not intended to be exhaustive or to limit the disclosure. Individual elements or features of a particular embodiment are generally not limited to that particular embodiment, but, where applicable, are interchangeable and can be used in a selected embodiment, even if not specifically shown or described. The same may also be varied in many ways. Such variations are not to be regarded as a departure from the disclosure, and all such modifications are intended to be included within the scope of the disclosure.

MULTIPLE-COMPRESSOR SYSTEM

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