USRE41955E1 - Capacity modulation for plural compressors - Google Patents

Abstract

A compressor system includes a pair of compressors located in a common shell. A common drive shaft drives both compressors and the drive shaft is powered by a single motor. One or both of the compressors can be equipped with a pulse width modulated capacity control system and a vapor injection system. When one compressor is equipped with these systems, the capacity can be varied between 50% and 110%. When both compressors are equipped with these systems, the capacity can be varied between 0% and 120%.

Description

FIELD OF THE INVENTION

The present invention relates to plural compressors disposed within a single shell. More particularly, the present invention relates to plural compressors disposed within a single shell which are driven by the same motor.

BACKGROUND OF THE INVENTION

Due to energy cost and conservation, there is a demand for refrigerant motor-compressor units which have an output which can be varied in accordance with demand. To satisfy this demand, many different systems have been proposed. One such system involves the unloading of one or more cylinders in a multi-cylinder compressor or the varying of re-expansion volume for the purpose of varying the output of the compressor system. These systems tend to be relatively complex and the efficiency of the compressor system in the unloaded state is not optimum. Variable speed compressors have also been used, but they require expensive controls and also the speed control and motor-compressor efficiency present some efficiency issues at least when operating in a reduced output condition.

Compressor systems have also been developed which, in place of a single compressor large enough to carry the maximum load, include a plurality of smaller motor-compressors having a combined output equal to the required maximum. These multi-compressor systems include means for controlling the total system in such a manner as to selectively activate and deactivate less than all of the compressors when it is desired to vary the output. These multi-compressor units have good efficiency but they require complex hook-up plumbing, including means for dealing with lubricating oil management in order to ensure that all the oil remains equally distributed between each of the compressors.

Further development of the multi-compressor systems has included the incorporation of a plurality of standard motor compressor units in a common shell. The common shell maximizes the compactness of the system and provides a common oil sump for equal oil distribution, a common suction gas inlet and a common discharge gas outlet. These single shell multi-compressor units have proved to be acceptable in the marketplace but they tend to be relatively large and the means for controlling the total system is still somewhat complex.

The continued development of multi-compressor systems has been directed towards reducing the overall costs and the overall size as well as simplifying the control systems which dictate the output quantity of these systems.

The present invention provides the art with a dual compressor system with one compressor being located at opposite ends of a common drive shaft. A motor rotor is press fit to the center portion of the drive shaft and the motor rotor is disposed within a motor stator. Thus, both compressors are powered by the same motor. The control of the output of the dual compressor system is accomplished by a variable speed motor or by a pulsed width modulation (PWM) capacity control system incorporated into one or both of the two compressors. When incorporating a variable speed motor for capacity control, the capacity can be varied from 0% to 100%. When incorporating the PWM capacity control system into one of the compressors, the capacity can be varied from 50% to 100%. When incorporating the PWM capacity control system into both compressors, the capacity can be varied from 0% to 100%. The capacity of one or both of the compressors can be increased to approximately 120% of capacity using vapor injection to increase the range of the dual compressor system if desired.

Further areas of applicability of the present invention will become apparent from the detailed description provided hereinafter. It should be understood that the detailed description and specific examples, while indicating the preferred embodiment of the invention, are intended for purposes of illustration only and are not intended to limit the scope of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will become more fully understood from the detailed description and the accompanying drawings, wherein:

FIG. 1 is a vertical cross sectional view through a motor-compressor system in accordance with the present invention;

FIG. 2 is a vertical cross sectional view of the motor compressor system shown inFIG. 1 with one of the two compressors incorporating pulse width modulation capacity control in accordance with the present invention;

FIG. 3 is an enlarged section view of the piston assembly shown inFIG. 2;

FIG. 4 is a top view of the discharge fitting shown inFIG. 3;

FIG. 5 is an end section view of the compressor shown inFIG. 2;

FIG. 6 is a side view of one of the non-orbiting scroll members shown inFIG. 2;

FIG. 7 is a cross sectional top view of the non-orbiting scroll member shown inFIG. 6;

FIG. 8 is an enlarged sectional view of the injection fitting shown inFIG. 2;

FIG. 9 is an end view of the fitting showing inFIG. 8;

FIG. 10 is a schematic diagram of a refrigerant system utilizing the capacity control system in accordance with the present invention;

FIG. 11 is a graph showing the capacity of the compressor using the capacity control system in accordance with the present invention; and

FIG. 12 is a vertical cross sectional view of the motor-compressor system shown inFIG. 1 with both of the two compressors incorporating pulse width modulation capacity control in accordance with the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The following description of the preferred embodiment(s) is merely exemplary in nature and is in no way intended to limit the invention, its application, or uses.

Referring now to the drawings in which like reference numerals designate like or corresponding parts throughout the several views, there is shown inFIG. 1 a multi-compressor compression system in accordance with the present invention which is designated generally by thereference numeral10.Compression system10 comprises a generally cylindricalhermetic shell12 having welded at each end thereof anend cap14 and at the central portion thereof abase16.Shell12 is provided with a suction inlet fitting18 and eachcap14 is provided with arefrigerant discharge fitting20 which may have the usual discharge valve therein. A transversely extendingpartition22 is affixed to each end ofshell12 by being welded about their periphery at the same point that eachend cap14 is welded toshell12. Acompressor mounting frame24 is press fit withinshell12.

Major elements ofcompression system10 that are affixed toframe24 include a pair of two piecemain bearing assemblies26 and amotor stator28. A drive shaft orcrankshaft30 having a pair ofeccentric crank pins32 at opposite ends thereof is rotatably journaled in a pair of bearings34 each secured within anoil pump36 secured to a respectivemain bearing assembly26.Crankshaft30 has at each end thereof an axially extendingbore38 which communicates with a respective radial extendingbore40 to provide lubricating oil to the moving components ofcompressor system10. The lower portion ofshell12 defines anoil sump42 which is filled with lubricating oil to a level slightly above the lower end of arotor44. Eachoil pump36 draws oil fromoil sump42 and pumps the oil into achamber46 defined byoil pump36 andmain bearing assembly26. Aseal48 seals eachchamber46 and a drain port (not shown) maintains the oil level withinchamber46. Oil fromchamber46 flows throughradial bore40 into axial extendingbore38 and to the moving components ofcompressor system10 which require lubrication.

Crankshaft30 is rotatably driven by an electric motor which includesstator28,windings50 passing therethrough androtor44 press fitted oncrankshaft30. A pair ofcounterweights52 are secured to opposite ends ofcrankshaft30 adjacent arespective crank pin32.

The upper surface of each two-piecemain bearing assembly26 is provided with a flatthrust bearing surface54 on which is disposed a respective orbitingscroll member56 having the usual spiral vane orwrap58 extending outwardly from anend plate60. Projecting outwardly from the lower surface of eachend plate60 of each orbitingscroll member56 is a cylindrical hub62 having a journal bearing therein and in which is rotatively disposed a drive bushing66 having an inner bore in which arespective crank pin32 is drivingly disposed. Eachcrank pin32 has a flat on one surface which drivingly engages a flat surface formed in a portion of the inner bore of each drive bushing66 to provide a radially compliant driving arrangement, such as shown in Assignee's U.S. Pat. No. 4,877,382, the disclosure of which is hereby incorporated herein by reference. A pair of Oldhamcouplings68 is also provided positioned between each orbitingscroll member56 and each two-piece bearinghousing assembly26. Each Oldhamcoupling68 is keyed to a respective orbitingscroll member56 and to a respectivenon-orbiting scroll member70 to prevent rotation of a respective orbitingscroll member56.

Eachnon-orbiting scroll member70 is also provided with awrap72 extending outwardly from anend plate74 which is positioned in meshing engagement with arespective wrap58 of a respective orbitingscroll member56. Eachnon-orbiting scroll member70 has a centrally disposed discharge5passage76 which communicates with a centrallyopen recess78 which is in turn in fluid communication with a respectivedischarge pressure chamber80 defined by eachend cap14 and eachpartition22. Anannular recess82 is also formed in eachnon-orbiting scroll member70 within which is disposed a respectivefloating seal assembly84.

Recesses78 and82 and floatingseal assemblies84 cooperate to define axial pressure biasing chambers which receive pressurized fluid being compressed byrespective wraps58 and72 so as to exert an axial biasing force on a respectivenon-orbiting scroll member70 to thereby urge the tips ofrespective wraps58 and72 into sealing engagement with the opposed end plate surfaces ofend plates74 and60, respectively. Floatingseal assemblies84 are preferably of the type described in greater detail in Assignee's U.S. Pat. No. 5,156,539, the disclosure of which is hereby incorporated herein by reference. Non-orbiting scroll members are designed to be mounted for limited axial movement to a respective two-piece mainbearing housing assembly26 in a suitable manner such as disclosed in the aforementioned U.S. Pat. No. 4,877,382 or Assignee's U.S. Pat. No. 5,102,316, the disclosure of which is hereby incorporated herein by reference.

Shell12 defines asuction pressure chamber90 which receives a gas for compression from suction gas inlet fitting18. The gas withinsuction pressure chamber90 is taken in at the radially outer portion of both sets ofintermeshed scrolls56 and70, it is compressed by both sets ofwraps58 and72 and it is discharged into a respectivedischarge pressure zone80 throughdischarge passage76 and recesses78. The compressed gas exits eachdischarge pressure zone80 throughrespective discharge fittings20. Tubing (not shown) secured to each discharge fitting combine gas from both dischargefittings20 to a common tube (not shown) which is then piped to the apparatus utilizing the compressed gas.

When it is desired to incorporate a capacity control system intocompression system10, the electric motor can be designed as a variable speed motor. The design for the variable speed motor which includesstator28,windings50 androtor44 are well known in the art and will not be discussed in detail. By providing variable speed capacity to the electric motor, the capacity ofcompressor10 can be varied between 0% and 100%.

Referring now toFIG. 2, there is shown a compressor system which includes a unique capacity control system in accordance with another embodiment of the present invention and which is designated generally by thereference numeral110.Compressor system110 is the same ascompressor system10, except that one pair ofscrolls56 and70 incorporate acapacity control system112.

Control system112 includes a discharge fitting114, apiston116, a shell fitting118, a solenoid valve120, acontrol module122 and asensor array124 having one or more appropriate sensors. Discharge fitting114 is threadingly received or otherwise secured withinopen recess78. Discharge fitting114 defines aninternal cavity126 and a plurality ofdischarge passages128. Adischarge valve130 is disposed below fitting114 and belowcavity126. Thus, pressurized gas overcomes the biasing load ofdischarge valve130 to opendischarge valve130 and allowing the pressurized gas to flow intocavity126, throughpassages128 and intodischarge pressure chamber80.

Referring now toFIGS. 2,3 and4, the assembly of discharge fitting114 andpiston116 is shown in greater detail. Discharge fitting114 defines anannular flange134. Seated againstflange134 is alip seal136 and a floatingretainer138.Piston116 is press fit or otherwise secured to discharge fitting114 andpiston116 defines anannular flange140 which sandwichesseal136 andretainer138 betweenflange140 andflange134. Discharge fitting114 defines apassageway142 and anorifice144 which extends through discharge fitting114 to fluidically connectdischarge pressure chamber80 with a pressure chamber146 defined by discharge fitting114,piston116,seal136,retainer138 andend cap14. Shell fitting118 is secured within a bore defined byend cap14 and slidingly receives the assembly of discharge fitting114,piston116,seal136 andretainer138. Pressure chamber146 is fluidically connected to solenoid valve120 by tube ISO and with suction fitting18 and thussuction pressure chamber90 through atube152. The combination ofpiston116,seal136 and floatingretainer138 provides a self-centering sealing system to provide accurate alignment with the internal bore of shell fitting118.Seal136 and floatingretainer138 include sufficient radial compliance such that any misalignment between the internal bore of shell fitting118 and the internal bore ofopen recess78 within which discharge fitting114 is secured is accommodated byseal136 and floatingretainer138.

In order to biasnon-orbiting scroll member70 into sealing engagement with orbitingscroll member56 for normal full load operation, solenoid valve120 is deactivated (or it is activated) bycontrol module122 in response tosensor array124 to block fluid flow betweentubes150 andtube152. In this position, chamber146 is in communication withdischarge pressure chamber80 throughpassageway142 andorifice144. The pressurized fluid at discharge pressure withinchambers80 and146 will act against opposite sides ofpiston16 thus allowing for the normal biasing ofnon-orbiting scroll member70 towards orbitingscroll member56 to sealingly engage the axial ends of each scroll member with the respective end plate of the opposite scroll member. The axial sealing of the twoscroll members56 and70causes compressor system110 to operate at 100% capacity.

In order to unloadcompressor system110, solenoid valve120 will be actuated (or it will be deactuated) bycontrol module122 in response tosensor array124. When solenoid valve120 is actuated (or unactuated),suction pressure chamber90 is in direct communication with chamber146 through suction fitting18,tube152, solenoid valve120 andrube150. With the discharge pressure pressurized fluid released to suction from chamber146, the pressure difference on opposite sides ofpiston116 will movenon-orbiting scroll member70 to the right as shown inFIG. 2 to separate the axial end of the tips of each scroll member with its respective end plate and the higher pressurized pockets will bleed to the lower pressurized pockets and eventually to suctionpressure chamber90.Orifice144 is incorporated to control the flow of discharge gas betweendischarge pressure chamber80 and chamber146. Thus, when chamber146 is connected to the suction side of the compressor, the pressure difference on opposite sides ofpiston116 will be created. Awave spring160 is incorporated to maintain the sealing relationship between floatingseal assembly84 andpartition22 during modulation ofnon-orbiting scroll member70. When a gap is created between the twoscroll members56 and70, the continued compression of the suction gas will be eliminated. When this unloading occurs,discharge valve130 will move to its closed position thereby preventing the backflow of high pressurized fluid fromdischarge pressure chamber80 or the downstream refrigeration system. When compression of the suction gas is to be resumed, solenoid valve120 will be deactuated (or it will be actuated) to again block fluid flow betweentubes150 and152 allowing chamber146 to be pressurized bydischarge pressure chamber80 throughpassageway142 andorifice144.

Control module122 is in communication withsensor array124 to provide the required information forcontrol module122 to determine the degree of unloading required for the particular conditions of the refrigeration system includingcompressor system110 existing at that time. Based upon this information,control module122 will operate solenoid valve120 in a pulsed width modulation mode to alternately place chamber146 in communication withdischarge pressure chamber80 andsuction pressure chamber90. The frequency with which solenoid valve120 is operated in the pulsed width modulated mode will determine the percent capacity of operation of one set ofscrolls56 and70 ofcompressor system110. As the sensed conditions change,control module122 will vary the frequency of operation for solenoid valve120 and thus the relative time periods at which one set ofscrolls56 and70 ofcompressor system110 is operated in a loaded and unloaded condition. The varying of the frequency of operation of solenoid valve120 can cause the operation of one set ofscrolls56 and70 between fully loaded or 100% capacity and completely unloaded or 0% capacity or at any of an infinite number of settings in between in response to system demands. This has the effect of varying the capacity ofcompressor system110 between 50% and 100%.

Referring now toFIGS. 5,6 and7, afluid injection system168 forcompressor system110 is shown in greater detail.Compressor system110 includes the capability of having fluid injected into the intermediate pressurized moving chambers at a point intermediatesuction pressure chamber90 anddischarge pressure chamber80. A fluid injection fitting170 extends throughshell12 and is fluidically connected to aninjection tube172 which is in turn fluidically connected to an injection fitting174 secured tonon-orbiting scroll member70.Non-orbiting scroll member70 defines a pair ofradial passages176 each of which extend between injection fitting174 and a pair ofaxial passages178.Axial passages178 are open to the moving chambers on opposite sides of onenon-orbiting scroll member70 ofcompressor system110 to inject the fluid into these moving chambers as required by a control system as is well known in the art.

Referring now toFIGS. 8 and 9, fitting170 is shown in greater detail. Fitting170 comprises aninternal portion180, and anexternal portion182.Internal portion180 includes an L-shapedpassage184 which sealingly receivesinjection tube172 at one end.External portion182 extends from the outside ofshell12 to the inside ofshell12 where it is unitary or integral withinternal portion180. A welding orbrazing attachment186 secures and seals fitting170 to shell12.External portion182 defines abore190 which is an extension of L-shapedpassage184.External portion182 also defines a cylindrical bore192 to which the tubing of the refrigeration system is secured.

FIG. 10 illustratesvapor injection system168 which provides the fluid for (he fluid injection system ofcompressor system110.Compressor system110 is shown in a refrigeration system which includes acondenser194, a first expansion valve orthrottle196, a flash tank or aneconomizer198, a second expansion valve orthrottle200, anevaporator202 and a series of piping204 interconnecting the components as shown in FIG.10.Compressor system110 is operated by the motor to compress the refrigerant gas. The compressed gas is then liquified bycondenser194. The liquified refrigerant passes throughexpansion valve196 and expands inflash tank198 where it is separated into gas and liquid. The gaseous refrigerant further passes through piping206 to be introduced intocompressor system110 throughfitting170. On the other band, the remaining liquid refrigerant further expands inexpansion valve200, is then vaporized inevaporator202 and is again taken intocompressor system110.

The incorporation offlash tank198 and the remainder ofvapor injection system168, allows the capacity of one set ofscrolls56 and70 ofcompressor system110 to increase above the fixed capacity of one set ofscrolls56 and70 ofcompressor system110. Typically, at standard air conditioning conditions, the capacity of one of the scrolls can be increased by approximately 20% to provide one set of the scrolls with 120% of its capacity which is 110% of the capacity ofcompressor system110 as shown in the graph in FIG.11. In order to be able to control the capacity of one set ofscrolls56 and70 ofcompressor system110, asolenoid valve208 is positioned withinpiping206. The amount of percent increase in the capacity of one set ofscrolls58 and70 ofcompressor system110 can be controlled by operatingsolenoid valve208 in a pulse width modulation mode.Solenoid valve208 when operated in a pulse width modulation mode in combination withcapacity control system112 ofcompressor system110 allows the capacity ofcompressor system110 to be positioned anywhere along the line shown in FIG.11.

Referring now toFIG. 12, there is shown a compressor system which includes a unique capacity control system in accordance with another embodiment of the present invention and which is designated generally by thereference numeral210.Compressor system210 is the same ascompressor system110, except that both pairs ofscrolls56 and70 incorporate bothcapacity control system112 andfluid injection system168. By incorporatingcapacity control system112 andfluid injection system168 into both pairs ofscrolls56 and70, the capacity ofcompressor system210 can be varied from 0% to 120%.

The description of the invention is merely exemplary in nature and, thus, variations that do not depart from the gist of the invention are intended to be within the scope of the invention. Such variations are not to be regarded as a departure from the spirit and scope of the invention.

Claims (83)

1. A scroll machine comprising:

an outer shell defining a suction pressure zone;

a first scroll compressor disposed within said suction pressure zone of said shell;

a second scroll compressor disposed within said suction pressure zone of said shell;

a drive shaft extending between and coupled to each of said first and second scroll compressors said drive shaft operable to drive said first and second scroll compressors for compressing fluid disposed within said suction pressure zone;

a mounting frame disposed within said suction pressure zone of said shell, said first and second scroll compressors being attached to said mounting frame;

a motor disposed within said suction pressure zone of said shell between said first and second scroll compressors, said motor being attached to said mounting frame and drivingly coupled to said drive shaft; and

an oil sump disposed between said outer shell and said mounting frame, said oil sump being in communication with said first scroll compressor through a first bore in said drive shaft and said second scroll compressor through a second bore in said drive shaft.

2. The scroll machine in accordance withclaim 1, wherein said motor comprises:

a stator attached to said mounting frame; and

a rotor attached to said drive shaft.

3. The scroll machine in accordance withclaim 1, wherein said first scroll compressor comprises:

a first scroll member having a first spiral wrap projecting outwardly from a first end plate;

a second scroll member having a second spiral wrap projecting outwardly from a second end plate, said second spiral wrap being interleaved with said first spiral wrap to define a first plurality of moving chambers therebetween when said second scroll member orbits with respect to said first scroll member; and

a first main bearing housing attached to said mounting-frame, said first main bearing housing rotatably supporting said drive shaft.

4. The scroll machine in accordance withclaim 3, wherein said mounting frame is disposed between said first main bearing housing and said shell.

5. The scroll machine in accordance withclaim 3, wherein said second scroll compressor comprises:

a third scroll member having a third spiral wrap projecting outwardly from a third end plate;

a fourth scroll member having a fourth spiral wrap projecting outwardly from a fourth end plate, said fourth spiral wrap being interleaved with said third spiral wrap to define a second plurality of moving chambers therebetween when said fourth scroll member orbits with respect to said third scroll member; and

a second main bearing housing attached to said mounting frame, said second main bearing housing rotatably supporting said drive shaft.

6. The scroll machine in accordance withclaim 5, wherein said mounting frame is disposed between said first main bearing housing and said shell and between said second main bearing housing and said shell.

7. The scroll machine in accordance withclaim 1, wherein said shell defines a first discharge pressure chamber in communication with said first scroll compressor and a second discharge chamber in communication with said second scroll compressor.

8. The scroll machine in accordance withclaim 7, wherein said first and second scroll compressors are disposed within said suction pressure chamber.

9. The scroll machine in accordance withclaim 1, further comprising a first capacity modulation system for varying the capacity of said first scroll compressor.

10. The scroll machine in accordance withclaim 9, wherein said first capacity modulation system includes a pulse width modulation system.

11. The scroll machine in accordance withclaim 9, further comprising a second capacity modulation system for varying the capacity of said second scroll compressor.

12. The scroll machine in accordance withclaim 11, wherein said first capacity modulation system includes a first pulse width modulation system and said second capacity modulation system includes a second pulse width modulation system.

13. The scroll machine in accordance withclaim 1, wherein said motor is a variable speed motor.

14. The scroll machine in accordance withclaim 1 wherein:

said first scroll compressor comprises a first non-orbiting scroll member interleaved with a first orbiting scroll member, said first non-orbiting, scroll member being mounted for axial movement within said outer shell; and

said second scroll compressor comprises a second non-orbiting scroll member interleaved with a second orbiting scroll member, said second non-orbiting scroll member being mounted for axial movement within said outer shell.

15. The scroll machine in accordance withclaim 1 further comprising a first fluid injection fitting extending through said outer shell for implementing a first vapor injection system for said first scroll compressor.

16. The scroll machine in accordance, withclaim 15 further comprising a second fluid injection fitting extending through said outer shell for implementing a second vapor injection system for said second scroll compressor.

17. The scroll machine in accordance withclaim 16, further comprising a first capacity modulation system for varying the capacity of said first scroll compressor.

18. The scroll machine in accordance withclaim 17, wherein said first capacity modulation system includes a pulse width modulation system.

19. The scroll machine in accordance withclaim 17, further comprising a second capacity modulation system for varying the capacity of said second scroll compressor.

20. The scroll machine in accordance withclaim 19, wherein said first capacity modulation system includes a first pulse width modulation system and said second capacity modulation system includes a second pulse width modulation system.

21. The scroll machine in accordance withclaim 15, further comprising a first capacity modulation system for varying the capacity of said first scroll compressor.

22. The scroll machine in accordance withclaim 21, wherein said first capacity modulation system includes a pulse width modulation system.

23. The scroll machine in accordance withclaim 21, further comprising a second capacity modulation system for varying the capacity of said second scroll compressor.

24. The scroll machine in accordance withclaim 23, wherein said first capacity modulation system includes a first pulse width modulation system and said second capacity modulation system includes a second pulse width modulation system.

25. The scroll machine in accordance withclaim 1 wherein said drive shaft includes a first eccentric crank pin and a second eccentric crank pin, said first and second crank pin defining a crank pin axis disposed eccentric from an axis of said drive shaft.

26. The scroll machine in accordance withclaim 1 wherein a single suction inlet extends through said outer shell, said single suction inlet being in communication with said suction pressure zone.

27. The scroll machine in accordance withclaim 1 further comprising a first oil pump in communication with said oil sump and said first scroll compressor.

28. The scroll machine in accordance withclaim 27 further comprising a second oil pump in communication with said oil sump and said second scroll compressor.

29. The scroll machine in accordance withclaim 1 wherein said outer shell comprises a generally cylindrical shell, a first end cap welded to one end of said generally cylindrical shell and a second end cap welded to an opposite end of said generally cylindrical shell.

30. A scroll machine comprising:

an outer shell defining a suction pressure zone;

a first scroll compressor disposed within said suction pressure zone of said shell, said first scroll compressor including a first non-orbiting scroll member interleaved with a first orbiting scroll member, said first orbiting scroll member being mounted for radial movement within said outer shell;

a second scroll compressor disposed within said suction pressure zone of said shell, said second scroll compressor including a second non-orbiting scroll member interleaved with a second orbiting scroll member, said second orbiting scroll member being mounted for radial movement within said outer shell;

a drive shaft extending between and coupled to each of said first and second orbiting scroll members, said drive shaft operable to drive said first and second scroll compressors for compressing fluid disposed within said suction pressure zone; and

a motor disposed within said suction pressure zone shell between said first and second scroll compressors, said motor being drivingly coupled to said drive shaft.

31. A scroll machine comprising:

an outer shell defining a suction pressure zone;

a first scroll compressor disposed within said suction pressure zone of said shell, said first scroll compressor comprising:

a first scroll member having a first end plate and a first spiral wrap extending therefrom;

a second scroll member having a second end plate and a second spiral wrap extending therefrom, said first and second scroll members being positioned with said first and second spiral wraps interleaved with each other;

a second scroll compressor disposed within said suction pressure zone of said shell, said second scroll compressor comprising;

a third scroll member having a third end plate and a third spiral wrap extending therefrom;

a fourth scroll member having a fourth end plate and a fourth spiral wrap extending therefrom, said third and fourth scroll members being positioned with said third and fourth spiral wraps interleaved with each other,

a drive shaft extending between and coupled to each of said first and third scroll members said drive shaft operable to drive said first and second scroll compressors for compressing fluid disposed within said suction pressure zone;

said second scroll member being movable between a first relationship in which sealing surfaces of said first and second scroll members are in sealing relationship to close off first fluid pockets and a second relationship wherein at least one of said sealing surfaces of said first and second scroll members are spaced apart to define a first leakage path between said first fluid pockets; and

a first fluid operated piston secured to said second scroll member, said first fluid operated piston being actuatable to apply a force to said second scroll member to move said second scroll member between said first relationship where said first scroll compressor operates at substantially full capacity and said second relationship where said first scroll compressor operates at substantially zero capacity.

32. The scroll machine according toclaim 31, wherein said first fluid operated piston is operated in a time pulsed manner to modulate the capacity of said first scroll compressor.

33. The scroll machine according toclaim 31, further comprising a fluid pressure chamber operative to apply said force to said first fluid operated piston.

34. The scroll machine according toclaim 33, wherein said force acts in an axial direction.

35. The scroll machine according toclaim 34, further comprising a first passage for supplying a pressurized fluid from said first scroll compressor to said pressure chamber.

36. The scroll machine according toclaim 35, further comprising a valve for controlling flow through said first passage, said valve being operative to vent said pressurized fluid from said pressure chamber to thereby enable said second scrolls to move between said first and second relationships.

37. The scroll machine according toclaim 36, wherein said valve is a solenoid operated valve.

38. The scroll-type machine according toclaim 37, wherein said solenoid operated valve is operated in a pulse width modulated mode.

39. The scroll machine according toclaim 35, further comprising a second passage for venting said pressurized fluid from said pressure chamber.

40. The scroll machine according toclaim 31 wherein said fourth scroll member is movable between a first relationship in which sealing surfaces of said third and fourth scroll members are in sealing relationship to close off second fluid pockets and a second relationship wherein at least one of said sealing surfaces of said third and fourth scroll members are spaced apart to define a second leakage path between said second fluid pockets, and said scroll machine further comprises:

a second fluid operated piston secured to said fourth scroll member, said second fluid operated piston being actuatable to apply a force to said fourth scroll member to move said fourth scroll member between said first relationship where said second scroll compressor operates at substantially full capacity and said second relationship where said second scroll compressor operates at substantially zero capacity.

41. The scroll machine according toclaim 40 further comprising:

a first fluid injection fitting extending through said outer shell for implementing a first vapor injection system for said first scroll compressor; and

a second fluid injection fitting extending through said outer shell for implementing a second vapor injection system for said second scroll compressor.

42. The scroll machine in accordance withclaim 1, wherein said outer shell includes a generally cylindrical shell and said oil sump is disposed along a cylindrical sidewall of said outer shell.

43. A scroll machine comprising:

an outer shell defining a first discharge pressure zone, a second discharge pressure zone, and a suction pressure zone;

a first scroll compressor including a first non-orbiting scroll member interleaved with a first orbiting scroll member, said first orbiting scroll member being mounted for radial movement within said outer shell;

a first capacity modulation system for selectively varying the capacity of said first scroll compressor;

a second scroll compressor including a second non-orbiting scroll member interleaved with a second orbiting scroll member, said second orbiting scroll member being mounted for radial movement within said outer shell;

a second capacity modulation system for selectively varying the capacity of said second scroll compressor;

a drive shaft extending between, and coupled to, each of said first and second orbiting scroll members, said drive shaft operable to drive said first and second scroll compressors for compressing fluid;

a mounting frame disposed within said outer shell;

a motor disposed between said first and second scroll compressors and attached to said mounting frame, said motor being drivingly coupled to said drive shaft;

an oil sump disposed between said outer shell and said mounting frame.

44. The scroll machine in accordance withclaim 43, wherein said mounting frame is disposed within said suction pressure zone of said shell.

45. The scroll machine in accordance withclaim 43, wherein said motor comprises:

a stator attached to said mounting frame; and

a rotor attached to said drive shaft.

46. The scroll machine in accordance withclaim 43, further comprising a first main bearing housing attached to said mounting frame, said first main bearing housing rotatably supporting said drive shaft.

47. The scroll machine in accordance withclaim 46, wherein said mounting frame is disposed between said first main bearing housing and said shell.

48. The scroll machine in accordance withclaim 46, further comprising a second main bearing housing attached to said mounting frame, said second main bearing housing rotatably supporting said drive shaft.

49. The scroll machine in accordance withclaim 48, wherein said mounting frame is disposed between said first main bearing housing and said shell and between said second main bearing housing and said shell.

50. The scroll machine in accordance withclaim 43, wherein said first discharge pressure zone is in communication with said first scroll compressor and said second discharge pressure zone is in communication with said second scroll compressor.

51. The scroll machine in accordance withclaim 50, wherein said first and second scroll compressors are disposed within said suction pressure zone of said shell.

52. The scroll machine in accordance withclaim 43, wherein said first capacity modulation system includes a pulse width modulation system.

53. The scroll machine in accordance withclaim 43, wherein said first capacity modulation system includes a first pulse width modulation system and said second capacity modulation system includes a second pulse width modulation system.

54. The scroll machine in accordance withclaim 43, wherein said motor is a variable speed motor.

55. The scroll machine in accordance withclaim 43, further comprising a first fluid injection fitting extending through said outer shell for implementing a first vapor injection system for said first scroll compressor.

56. The scroll machine in accordance withclaim 55, further comprising a second fluid injection fitting extending through said outer shell for implementing a second vapor injection system for said second scroll compressor.

57. The scroll machine in accordance withclaim 56, wherein said first capacity modulation system includes a pulse width modulation system.

58. The scroll machine in accordance withclaim 57, wherein said second capacity modulation system includes a pulse width modulation system.

59. The scroll machine in accordance withclaim 55, wherein said first capacity modulation system includes a pulse width modulation system.

60. The scroll machine in accordance withclaim 59, wherein said second capacity modulation system includes a pulse width modulation system.

61. The scroll machine in accordance withclaim 43 wherein said drive shaft includes a first eccentric crank pin and a second eccentric crank pin, said first and second crank pins defining a crank pin axis disposed eccentric from an axis of said drive shaft.

62. The scroll machine in accordance withclaim 43, further comprising a single suction inlet extending through said outer shell, said single suction inlet being in communication with said suction pressure zone.

63. The scroll machine in accordance withclaim 43, further comprising a first oil pump in communication with said oil sump and said first scroll compressor.

64. The scroll machine in accordance withclaim 63, further comprising a second oil pump in communication with said oil sump and said second scroll compressor.

65. The scroll machine in accordance withclaim 43, wherein said outer shell comprises a generally cylindrical shell, a first end cap welded to one end of said generally cylindrical shell and a second end cap welded to an opposite end of said generally cylindrical shell.

66. The scroll machine in accordance withclaim 43, wherein said outer shell includes a generally cylindrical shell and said oil sump is disposed along a cylindrical sidewall of said outer shell.

67. The scroll machine in accordance withclaim 43, wherein at least one of said first capacity modulation system and said second capacity modulation system includes a fluid-operated piston.

68. A scroll machine comprising:

an outer shell defining a suction pressure zone;

a first scroll compressor disposed within said suction pressure zone of said shell, said first scroll compressor comprising:

a first scroll member having a first end plate and a first spiral wrap extending therefrom;

a second scroll member having a second end plate and a second spiral wrap extending therefrom, said first and second scroll members being positioned with said first and second spiral wraps interleaved with each other;

a second scroll compressor disposed within said shell, said second scroll compressor comprising;

a third scroll member having a third end plate and a third spiral wrap extending therefrom;

a fourth scroll member having a fourth end plate and a fourth spiral wrap extending therefrom, said third and fourth scroll members being positioned with said third and fourth spiral wraps interleaved with each other;

a drive shaft extending between and coupled to each of said first and third scroll members said drive shaft operable to drive said first and second scroll compressors for compressing fluid disposed within said suction pressure zone;

a mounting frame disposed within said outer shell;

said second scroll member being movable between a first position in which sealing surfaces of said first and second scroll members are in sealing relationship to close off first fluid pockets and a second position wherein at least one of said sealing surfaces of said first and second scroll members are spaced apart to define a first leakage path between said first fluid pockets;

a first capacity modulation system for applying a force to said second scroll member to move said second scroll member between said first position where said first scroll compressor operates at substantially full capacity and said second position where said first scroll compressor operates at substantially zero capacity; and

an oil sump disposed between said outer shell and said mounting frame.

69. The scroll machine in accordance withclaim 68, wherein said first capacity modulation system is operated in a time pulsed manner to modulate the capacity of said first scroll compressor.

70. The scroll machine in accordance withclaim 68, further comprising a fluid pressure chamber operative to apply said force to said second scroll member.

71. The scroll machine in accordance withclaim 70, wherein said force acts in an axial direction.

72. The scroll machine in accordance withclaim 71, further comprising a first passage for supplying a pressurized fluid from said first scroll compressor to said pressure chamber.

73. The scroll machine in accordance withclaim 72, further comprising a valve for controlling flow through said first passage, said valve being operative to vent said pressurized fluid from said pressure chamber to thereby enable said second scroll to move between said first and second positions.

74. The scroll machine in accordance withclaim 73, wherein said valve is a solenoid-operated valve.

75. The scroll-type machine in accordance withclaim 74, wherein said solenoid-operated valve is operated in a pulse width modulated mode.

76. The scroll machine in accordance withclaim 72, further comprising a second passage for venting said pressurized fluid from said pressure chamber.

77. The scroll machine in accordance withclaim 68 wherein said fourth scroll member is movable between a first position in which sealing surfaces of said third and fourth scroll members are in sealing relationship to close off second fluid pockets and a second position wherein at least one of said sealing surfaces of said third and fourth scroll members are spaced apart to define a second leakage path between said second fluid pockets, and said scroll machine further comprises:

a second capacity modulation system for applying a force to said fourth scroll member to move said fourth scroll member between said first position where said second scroll compressor operates at substantially full capacity and said second position where said second scroll compressor operates at substantially zero capacity.

78. The scroll machine in accordance withclaim 77, wherein at least one of said first capacity modulation system and said second capacity modulation system includes a fluid-operated piston.

79. The scroll machine in accordance withclaim 77 further comprising:

a first fluid injection fitting extending through said outer shell for implementing a first vapor injection system for said first scroll compressor; and

a second fluid injection fitting extending through said outer shell for implementing a second vapor injection system for said second scroll compressor.

80. The scroll machine in accordance withclaim 68, wherein said outer shell includes a generally cylindrical shell and said oil sump is disposed along a cylindrical sidewall of said outer shell.

81. The scroll machine in accordance withclaim 68, further comprising a first discharge pressure chamber in fluid communication with said first scroll compressor.

82. The scroll machine in accordance withclaim 81, further comprising a second discharge pressure chamber in fluid communication with said second scroll compressor.

83. The scroll machine in accordance withclaim 68, wherein said first capacity modulation system includes a fluid-operated piston.

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