Capacity modulated scroll machine - Patent Review 5611674

We claim:

1. A scroll-type machine comprising:

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

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

a fixed support structure for supporting said first and second scroll members for relative orbital movement therebetween whereby said first and second spiral wraps define sealed moving fluid pockets which progressively decrease in size as they move from a radially outer position to a radially inner position;

a power source;

a drive shaft for transmitting power from said power source to said first scroll member;

a coupling for connecting said drive shaft to said first scroll member whereby said power source may operate to effect said relative orbital movement between said first and second scroll members,

a device selectively actuable to effect relative radial movement between said first and second scrolls to thereby form a leakage path between said moving fluid pockets while said power source continues to operate whereby the capacity of said compressor may be modulated, said device being remote from and independent of said coupling connecting said power source to said first scroll.

2. A scroll-type machine as set forth in claim 1 wherein said leakage path is sufficient to reduce the capacity of said scroll machine to substantially zero.

3. A scroll-type machine as set forth in claim 1 wherein said device operates to reduce the radius of said relative orbital movement.

4. A scroll-type machine as set forth in claim 1 wherein said device is actuated by fluid pressure.

5. A scroll-type machine as set forth in claim 1 wherein said device is actuated in a time pulsed manner between a first position in which said leakage path is formed for a first predetermined time period and a second position in which said moving fluid pockets are sealed from each other for a second predetermined time period.

6. A scroll-type machine as set forth in claim 5 further comprising sensor connected to a control module and operative to provide a signal thereto indicative of operating conditions, said control module being connected to said device and operative to control the duration of said first and second predetermined time periods to thereby modulate the capacity of said machine while maximizing the efficiency thereof for said operating conditions.

7. A scroll-type machine as set forth in claim 1 wherein said device includes a chamber, a piston movably disposed within said chamber, said piston being movable into engagement with said first scroll member to reduce the orbital radius thereof.

8. A scroll-type machine as set forth in claim 7 wherein said device further includes a passage for supplying pressurized fluid to said chamber to effect movement of said piston.

9. A scroll-type machine as set forth in claim 8 wherein said device further includes a valve operative to selectively supply pressurized fluid to said chamber through said passage.

10. A scroll-type machine as set forth in claim 9 wherein said valve is actuated in a time pulsed manner whereby said leakage path is formed for a first predetermined time period and said moving fluid pockets are sealed from each other for a second predetermined time period.

11. A scroll-type machine as set forth in claim 10 further comprising a sensor connected to a control module and operative to provide a signal thereto indicative of operating conditions, said control module being connected to said valve and operative to control the duration of said first and second predetermined time periods to thereby modulate the capacity of said machine while maximizing the efficiency thereof for said operating conditions.

12. A scroll-type machine as set forth in claim 7 wherein said valve is also operative to connect said chamber to an area at substantially suction pressure to thereby vent said chamber and allow movement of said piston out of engagement with said first scroll member.

13. A scroll-type machine as set forth in claim 12 further comprising a spring operative to exert a force on said piston to move said piston out of engagement with said first scroll member.

14. A scroll-type machine as set forth in claim 12 further comprising a second chamber and a passage for placing said second chamber in communication with a supply of pressurized fluid, said pressurized fluid acting on said piston to urge said piston out of engagement with said first scroll member.

15. A scroll-type machine as set forth in claim 1 wherein said machine is a compressor and further comprising a passage opening into at least one of said moving fluid pockets and operative to vent said pocket to a lower pressure area of said machine, a valve for selectively opening and closing said passage whereby the compression ratio of said compressor is reduced when said valve opens said passage.

16. A scroll-type machine as set forth in claim 1 further comprising a motor drivingly connected to said first scroll member and a motor controller operative to vary an operating parameter of said motor in response to a signal from said device indicative of actuation thereof to thereby improve the efficiency of said motor while the capacity of said machine is reduced.

17. A scroll-type machine comprising:

a first scroll member having a first end plate and a first spiral wrap provided thereon;

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

a drive shaft drivenly connected to said first scroll member and operative to drive said first scroll member so as to effect relative orbital movement between said first and second scroll members;

a bearing housing rotatably supporting said drive shaft and supporting said first and second scroll members for relative orbital movement therebetween, said bearing housing at least in part defining a chamber;

a piston disposed within said chamber and movable between a first position in which the radius of said relative orbital movement has a first magnitude and a second position in which said piston operates to restrict the radius of said relative orbital movement to a magnitude less than said first magnitude to thereby form a leakage path between said moving fluid pockets whereby the capacity of said compressor is reduced.

18. A scroll-type machine as set forth in claim 17 wherein said piston is cycled between said first and second positions in a time pulsed manner whereby said piston is in said first position for a first predetermined time period and in said second position for a second predetermined time period.

19. A scroll-type machine as set forth in claim 18 further comprising a sensor connected to a control module and operative to provide a signal thereto indicative of operating conditions, said control module being operative to control movement of said piston between said first and second positions and to control the duration of said first and second predetermined time periods.

20. A scroll-type machine as set forth in claim 17 wherein said piston is movable into and out of engagement with a surface of said first scroll member.

21. A scroll-type machine as set forth in claim 20 wherein said surface is conical and is formed on a projection provided on the end plate of said first scroll member.

22. A scroll-type machine as set forth in claim 21 wherein said drive shaft includes an eccentric pin and said projection includes a bore into which said eccentric pin projects to drivingly couple said drive shaft to said first scroll member.

23. A scroll-type machine as set forth in claim 22 wherein said piston is positioned in surrounding relationship to said drive shaft and includes a conical surface engageable with said conical surface on said projection when said piston is in said second position.

24. A scroll-type machine as set forth in claim 23 further comprising springs for urging said piston into said first position.

25. A scroll-type machine as set forth in claim 20 further comprising a passage for supplying pressurized fluid to said chamber to move said piston from said first position to said second position and a valve to control flow of said pressurized fluid to said chamber.

26. A scroll-type machine as set forth in claim 25 wherein said valve includes a passage connected in fluid communication with the discharge from said compressor and a second passage connected in fluid communication with a suction inlet of said compressor.

27. A scroll-type machine as set forth in claim 20 wherein said surface is provided on the periphery of said first end plate.

28. A scroll-type machine as set forth in claim 27 wherein said piston includes a first diameter portion positioned in juxtaposed position to said surface when said piston is in a first position and a second larger diameter portion positioned in juxtaposed relationship to said surface when said pin is in said second position.

29. A scroll-type machine as set forth in claim 28 further comprising a plurality of said chambers positioned in circumferentially spaced relationship and a substantially identical piston movably disposed in each of said chambers, said surface being continuously engageable with at least two of said pistons when said pistons are in said second position.

30. A scroll-type machine as set forth in claim 20 wherein said surface is in the form of an opening in said first end plate.

31. A scroll-type machine as set forth in claim 30 further comprising a second chamber spaced from said first chamber, a second piston movably disposed within said second chamber and engageable with the periphery of a second opening provided in said first end plate.

Description Submit all comments and votes

BACKGROUND AND SUMMARY OF THE INVENTION

The present invention is related to capacity modulation of compressors and more particularly to capacity modulation of scroll-type compressors.

Capacity modulation is often a desirable feature to incorporate in air conditioning and refrigeration compressors in order to better accommodate the wide range of loading to which the systems may be subjected. Many different approaches have been utilized for providing this capacity modulation feature ranging from controlling of the suction inlet to bypassing discharge gas back to the suction inlet. With scroll-type compressors, capacity modulation has often been accomplished via a delayed suction approach which comprises providing ports at various positions which, when opened, allow the compression chambers formed between the intermeshing scroll wraps to communicate with the suction gas supply thereby delaying the point at which compression of the suction gas begins. This method of capacity modulation actually reduces the compression ratio of the compressor. While such systems are effective at reducing the capacity of the compressor, they are only able to provide a predetermined amount of compressor unloading, the amount of unloading being dependent upon the positioning of the unloading ports along the wraps. While it is possible to provide multiple step unloading by incorporating a plurality of such ports at different locations, this approach becomes costly and requires additional space to accommodate the separate controls for opening and closing each set of ports.

The present invention, however, overcomes these deficiencies in that it enables virtually a continuous range of unloading from 100 percent or full capacity down to virtually zero capacity utilizing only a single set of controls. Further, the system of the present invention enables the operating efficiency of the compressor and/or refrigeration system to be maximized for any degree of compressor unloading desired.

In the present invention, compressor unloading is accomplished by cyclically effecting axial or radial separation of the two scroll members for predetermined periods of time during the operating cycle of the compressor. More specifically, the present invention provides an arrangement wherein one scroll member is moved axially or radially toward and away from the other scroll member in a pulsed fashion to cyclically provide a leakage path across the tips or flanks of the wraps from higher pressure compression pockets defined by the intermeshing scroll wraps to lower pressure pockets and ultimately back to suction. By controlling the relative time between sealing and unsealing of the scroll wrap tips or flanks, virtually any degree of compressor unloading can be achieved with a single control system. Further, by sensing various conditions within the refrigeration system, the duration of compressor loading and unloading for each cycle can be selected for a given capacity such that overall system efficiency is maximized. For example, if it is desired to operate the compressor at 50 percent capacity, this can be accomplished by operating the compressor alternately in a loaded condition for five seconds and unloaded for five seconds or loaded for seven seconds and unloaded for seven seconds, one or the other of which may provide greater efficiency for the specific operating conditions being encountered.

The various embodiments of the present invention described below provide a wide variety of arrangements by which one scroll member may be axially or radially reciprocated with respect to the other to accommodate a full range of compressor unloading. The ability to provide a full range of capacity modulation with a single control system as well as the ability to select the duration of loaded and unloaded operation cooperate to provide an extremely efficient system at a relatively low cost.

Additionally, in order to even further improve system efficiency in some applications, it may be desirable to combine a delayed suction type of capacity modulation with the pulsed unloading approach mentioned above. For example, when operating conditions are such that system pressures just downstream of the discharge valve are at a level below the full load design level, the compression ratio of the compressor will result in pressure of the compressed fluid as it is discharged from the compression chamber being too high, a condition known as over-compression. The most efficient way to reduce capacity under these conditions is to reduce the compression ratio of the compressor and hence the pressure of the compressed fluid exiting the compression chamber such that it is equal to or only slightly above the system pressure just downstream of the discharge valve thus eliminating the lost work due to over-compression. However, if a further reduction in capacity is indicated by system condition once the over-compression condition has been eliminated, the use of a pulsed type of capacity modulation will be more efficient as it will avoid creation of a condition known as under-compression, that being a situation where the pressure of the compressed fluid as it leaves the compression chamber being below that of the system just downstream of the discharge valve. Thus, the present invention also includes a system in which both pulsed and delayed suction capacity modulation approaches are combined which result in even greater efficiencies for systems likely to encounter such operating conditions than could be achieved by either of the two capacity modulation approaches alone.

Additionally, the present invention may also incorporate a motor control module which will operate to control various operating parameters thereof to enhance its operating efficiency during periods when the motor load is reduced due to unloading of the compressor.

Additional advantages and features of the present invention will become apparent from the subsequent description and the appended claims taken in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a section view of a scroll-type refrigeration compressor in accordance with the present invention;

FIG. 2 is a fragmentary section view of a scroll-type refrigeration compressor showing another embodiment of the present invention;

FIG. 3 is a view similar to that of FIG. 2 but showing the compressor in an unloaded condition;

FIG. 4 is a fragmentary section view of a scroll-type refrigeration compressor showing a further embodiment of the present invention;

FIG. 5 is an enlarged view of the valve arrangement incorporated in the embodiment shown in FIG. 4;

FIG. 6 is also a fragmentary section view of a scroll-type refrigeration compressor showing another embodiment of the present invention;

FIGS. 7 through 15 are all fragmentary section views of refrigeration compressors in accordance with the present invention in which the orbiting scroll member is axially reciprocated to accomplish compressor unloading;

FIGS. 16 through 22 are all fragmentary section views of refrigeration compressors in accordance with the present invention in which the non-orbiting scroll member is axially reciprocated to accomplish compressor unloading;

FIGS. 23 through 28 are all fragmentary section views of refrigeration compressors in accordance with the present invention in which the scroll members are co-rotating;

FIGS. 29 through 30 are both fragmentary section views of additional embodiments of refrigeration compressors all in accordance with the present invention in which the non-orbiting scroll member is reciprocated; and

FIG. 31 is a section view of yet another embodiment of a scroll-type compressor in accordance with the present invention adapted to be driven by an external power source;

FIGS. 32 through 34 are fragmentary section view of additional embodiments of scroll-type compressors in accordance with the present invention;

FIG. 34A is an enlarged fragmentary view of the valving arrangement shown in FIG. 34 and enclosed within circle 34A;

FIG. 35 is a fragmentary section view of a further embodiment of a scroll-type compressor in accordance with the present invention;

FIG. 36 is also a fragmentary section view of yet a further embodiment of the present invention showing an arrangement for radially unloading of the compressor in accordance with the present invention;

FIG. 37 is a section view of the crank pin and drive bushing employed in the embodiment of FIG. 36, the section being taken along lines 37--37 thereof;

FIG. 38 is a section view of the embodiment shown in FIG. 36, the section being taken along lines 38--38 thereof;

FIG. 39 is a view similar to that of FIG. 36 but showing the compressor in an unloaded condition;

FIG. 40 is a fragmentary section view showing a modified version of the embodiment of FIG. 36, all in accordance with the present invention;

FIG. 41 is a fragmentary section view showing a portion of a scroll-type compressor incorporating another embodiment of the radial unloading arrangement of FIG. 36, all in accordance with the present invention;

FIG. 42 is a section view similar to that of FIG. 38 but showing the embodiment of FIG. 41;

FIG. 43 is a fragmentary section view showing yet another embodiment of the present invention;

FIG. 44 is a view of a portion of the embodiment shown in FIG. 43 in an unloaded condition;

FIG. 45 is a schematic showing a means for reducing motor power consumption during periods when the compressor is operating in an unloaded condition in accordance with the present invention; and

FIG. 46 is a section view of a compressor incorporating both cyclical scroll wrap separation and delayed suction unloading, all in accordance with the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring now to the drawings and in particular to FIG. 1, there is shown a hermetic scroll compressor in accordance with the present invention indicated generally at 10. Scroll compressor 10 is generally of the type described in assignee's U.S. Pat. No. 5,102,316, the disclosure of which is incorporated by reference, and includes an outer shell 12 within which is disposed a driving motor including stator 14 and rotor 16, a crankshaft 18 to which rotor 16 is secured, upper and lower bearing housings 20, 22 for rotatably supporting crankshaft 18 and compressor assembly 24.

Compressor assembly 24 includes an orbiting scroll member 26 supported on upper bearing housing 20 and drivingly connected to crankshaft 18 via crank pin 28 and drive bushing 30. A second non-orbiting scroll member 32 is positioned in meshing engagement with scroll member 26 and axially movably secured to upper bearing housing 20 by means of a plurality of bolts 34 and associated sleeve members 36. An Oldham coupling 38 is provided which cooperates between scroll members 26 and 32 to prevent relative rotation therebetween.

A partition plate 40 is provided adjacent the upper end of shell 12 and serves to define a discharge chamber 42 at the upper end thereof.

In operation, as orbiting scroll member 26 orbits with respect to scroll member 32, suction gas is drawn into shell 12 via suction inlet 44 and thence into compressor 24 through inlet 46 provided in non-orbiting scroll member 32. The intermeshing wraps provided on scroll members 26 and 32 define moving fluid pockets which progressively decrease in size and move radially inwardly as a result of the orbiting motion of scroll member 26 thus compressing the suction gas entering via inlet 46. The compressed gas is then discharged into discharge chamber 42 via discharge port 48 provided in scroll member 32 and passage 50. A suitable pressure responsive discharge valve 51 is preferably provided seated within discharge port 48.

Scroll member 32 is also provided with an annular cylindrical recess 52 formed in the upper surface thereof. One end of a generally irregularly shaped cylindrical member 54 within which passage 50 is provided projects into cylinder 52 and divides same into upper and lower chambers 56 and 58. The other end of cylindrical member 54 is sealingly secured to partition plate 40. An annular ring 60 is secured to the upper end of scroll member 32 and includes an axially extending flange 62 slidingly engageable with cylinder member 54 to thereby seal off the open upper end of chamber 56.

Cylindrical member 54 includes a passage 64 having one end which opens into upper chamber 56. A fluid line 66 is connected to the other end of passage 64 and extends outwardly through shell 12 to a solenoid operated valve 68. A second fluid line 70 extends from valve 68 to suction line 72 connected to suction inlet 44 and a third fluid line 74 extends from valve 68 to a discharge line 76 extending outwardly from discharge chamber 42.

In order to bias scroll member 32 into sealing engagement with scroll member 26 for normal fully loaded operation, a bleed hole 78 is provided in scroll member 32 communicating between chamber 58 and a compression pocket at an intermediate pressure between suction and discharge pressure. Thus, chamber 58 will be at an intermediate pressure which together with the discharge pressure acting on the upper surface of scroll member 32 in the area of discharge port 48 will exert a biasing force on scroll member urging it axially into sealing engagement with orbiting scroll member 26. At the same time, solenoid valve 68 will be in a position so as to place upper chamber 56 in fluid communication with suction line 72 via fluid lines 66 and 70.

In order to unload compressor 24, solenoid valve 68 will be actuated in response to a signal from control module 80 to interrupt fluid communication between lines 66 and 70 and to place fluid line 66 in communication with discharge line 76 thus increasing the pressure within chamber 56 to that of the discharge gas. The biasing force resulting from this discharge pressure will overcome the sealing biasing force thereby causing scroll member 32 to move axially upwardly away from orbiting scroll member 26. This axial movement will result in the creation of a leakage path between the respective wrap tips and end plates of scroll members 26 and 32 thereby substantially eliminating continued compression of the suction gas. When unloading occurs, discharge valve 51 will move to a closed position thereby preventing the back flow of high pressure fluid from discharge chamber 42 or the downstream system. When compression of the suction gas is to be resumed, solenoid valve 68 will be actuated to a position in which fluid communication between upper chamber 56 and discharge line 76 via lines 66 and 74 is interrupted and upper chamber 56 is placed in communication with suction line 72 via fluid lines 66 and 70 thereby relieving the axially directed separating force. This then allows the cooperative action of the intermediate pressure in chamber 58 and discharge pressure acting in passage 50 to again move scroll member 32 into sealing engagement with scroll member 26.

Preferably, control module 80 will have one or more appropriate sensors 82 connected thereto to provide the required information for control module 80 to determine the degree of unloading required for the particular conditions existing at that time. Based upon this information, control module 80 will send appropriately timed sequential signals to solenoid valve 68 to cause it to alternately place fluid line 66 in communication with discharge line 76 and suction line 72. For example, if conditions indicate that it is desirable to operate compressor 24 at 50 percent of full capacity, control module 80 may actuate solenoid valve to a position to place fluid line 66 in communication with suction line 72 for a period of say 10 seconds whereupon it is switched to place fluid line 66 in fluid communication with discharge line 76 for a like period of 10 seconds. Continued switching of solenoid valve 68 in this manner will result in compression occurring during only 50 percent of the operating time thus reducing the output of compressor 24 to 50 percent of its full load capacity. As the sensed conditions change, control module will vary the relative time periods at which compressor 24 is operated in a loaded and unloaded condition such that the capacity of compressor 24 may be varied between fully loaded or 100 percent capacity and completely unloaded or 0 percent capacity in response to varying system demands.

FIGS. 2 and 3 show an axial unloading scroll compressor 34 similar to that of FIG. 1 with the primary exception being the arrangement for placing upper chamber 56 in fluid communication with suction and discharge lines. Accordingly, like portions have been indicated by the same reference numbers. As shown therein, passage 64 has been replaced by a passage 86 provided in annular member 60 which opens at one end into upper chamber 56 and at the other end through a radially outwardly facing sidewall. A flexible fluid line 88 extends from the outer end of passage 86 to a fitting 90 extending through shell 12 with a second line 92 connecting fitting 90 to solenoid valve 68. As with FIG. 1, solenoid valve 68 has fluid lines 70 and 74 connected to suction line 72 and discharge line 76 and is controlled by control module 80 in response to conditions sensed by sensor 82 to effect movement of non-orbiting scroll member 32 between the positions shown in FIGS. 2 and 3 in the same manner as described above with respect to the embodiment of FIG. 1. While this embodiment eliminates the need for an extra fitting extending outwardly from the high pressure discharge chamber 42, it requires that fluid conduit 88 be flexible so as to accommodate axial movement of scroll member 32 and associated annular member 60. It should also be noted that in this embodiment cylindrical member 54 is sealingly secured to partition plate 40 by means of nut 55 which threadedly engages the upper end thereof. Also in this embodiment, discharge valve 51 has been replaced by a discharge check valve 93 secured to the outer shell. It should be noted that the provision of a check valve some place along the discharge flowpath is highly desirable in order to prevent back flow of compressed gas from the system when the compressor is in an unloaded condition.

FIGS. 4 and 5 show another embodiment 94 of the present invention in which axial unloading separating pressure fluid is provided directly from the discharge gas exiting the compressor. In this embodiment, a tubular member 96 is suitably secured to partition member 40 and includes a radially outwardly extending flange 98 which is positioned in and separates cylindrical recess into upper and lower chambers 56 and 58. Tubular member 96 also defines passage 50 for directing compressed discharge gas from port 48 to discharge chamber 42. An axial extending bore 100 is provided in tubular member which opens outwardly through the upper end thereof and is adapted to receive a fluid conduit 102. Fluid conduit 102 extends outwardly through the top of shell 12 and is connected to solenoid valve 68. Solenoid valve also has fluid conduits 70 and 74 connected to respective suction and discharge lines 72, 76 and is controlled by control module 80 in response to signals from appropriate sensors 82 in the same manner as described above.

A valve member 104 is axially movably disposed within bore 100. Valve member 104 includes a reduced diameter portion 106 operative to place radially extending passages 108 and 110 provided in member 96 in fluid communication when in a first position so as to vent upper chamber 56 to suction and to place radial fluid passage 110 in fluid communication with radial fluid passage 112 when in a second position so as to admit discharge gas from discharge flowpath 50 to upper chamber 56. A vent passage 113 is also provided which communicates between the bottom of bore 100 and passage 50 to vent gas from the area below valve 104 during operation thereof. A spring 114 is also provided which serves to aid in biasing valve 104 into its second position whereas pressurized discharge fluid entering bore 100 via passage 112 and passage 113 serves to bias valve member 104 into its first position.

As shown, valve member 104 and solenoid valve 68 are both in a position for fully loaded operation wherein solenoid valve 68 is in position to place fluid conduit 102 in communication with the suction line 72 and valve member 104 is in a position to vent upper chamber 56 to the interior of shell 12 which is at suction pressure. When it is desired to unload the compressor, solenoid valve 68 will be actuated to a position to place fluid line 102 in communication with fluid line 74 thereby enabling pressurized discharge fluid to act on the upper end of valve member 104. This pressurized fluid together with spring 114 will cause valve member 104 to move downwardly thereby closing off communication of radial passage 110 with radial passage 108 and opening communication between radial passage 110 and radial passage 112. Discharge pressure fluid will then flow into upper chamber 56 thus overcoming the intermediate pressure biasing force resulting from the communication of chamber 58 with a compression chamber at intermediate pressure via passage 78 and causing scroll member 32 to move axially upwardly away from orbiting scroll member 26. It should be noted that the relatively short flowpath for supplying discharge pressure fluid to upper chamber 56 ensures rapid unloading of the compressor.

FIG. 6 shows a modified embodiment similar to that of FIGS. 4 and 5 except that solenoid valve 68 is positioned within shell 12. This embodiment eliminates the need for an additional fluid conduit through the high pressure portion of the shell, requiring only an electrical feed for actuating solenoid valve 68. In all other respects, construction and operation of this embodiment is substantially the same as that described above with respect to the embodiment shown in FIGS. 4 and 5 and accordingly corresponding portions are indicated by the same reference numbers.

While the previously described embodiments have been directed to unloading arrangements wherein the non-orbiting scroll has been moved axially away from the orbiting scroll, it is also possible to apply these same principles to the orbiting scroll. FIGS. 7 through 15 described below illustrate such a series of embodiments.

Referring now to FIG. 7, a scroll compressor 140 is shown which is similar to the scroll compressors described above except that non-orbiting scroll member 142 is non-movably secured to bearing housing 144 and orbiting scroll member 146 is axially movable. It is also noted that compressor 140 is a high side machine, that is, the suction inlet 149 is directly connected to the non-orbiting scroll member 142 and the interior of the shell 12 is at discharge pressure. In this embodiment, orbiting scroll member 146 is axially movable and is biased into engagement with non-orbiting scroll 142 by means of a pressure chamber 148 defined between orbiting scroll member 146 and main bearing housing 144. An annular recess 150 is provided in main bearing housing 144 in which is disposed a suitable annular resilient seal member 152 which sealingly engages the lower surface of orbiting scroll member 146 so as to prevent fluid communication between chamber 148 and the interior of shell 12 which is at discharge pressure. A second annular seal 154 is provided on main bearing housing 144 surrounding shaft 18 to prevent fluid leakage therealong. A small passage 156 is provided through the end plate of orbiting scroll member 146 to place chamber 148 in fluid communication with a compression chamber at a pressure intermediate suction and discharge pressure. Additionally, a passage 158 in main bearing housing extends outwardly from chamber 148 and has one end of fluid line 160 connected thereto. The other end of fluid line 160 extends outwardly through shell 12 and is connected to solenoid valve 162. A second fluid line 164 extends between solenoid valve 162 and suction line 148.

In operation, chamber 148 will be supplied with fluid at intermediate pressure to thereby bias orbiting scroll 146 into sealing engagement with non-orbiting scroll 142. At this time, solenoid valve 162 will be in a position to prevent fluid communication between lines 160 and 164. In order to unload compressor 140, solenoid valve 162 is actuated to a position to place line 160 in fluid communication with fluid line 164 thereby venting the intermediate pressure in chamber 148 to suction. The pressure within the compression pockets will then cause orbiting scroll member 146 to move axially downwardly as shown compressing resilient seals 152 and thereby forming a leakage path across the respective wrap tips and associated end plates of the orbiting and non-orbiting scroll members 146, 142. While passage 156 may continue to provide fluid at a pressure somewhat higher than suction pressure to chamber 148, the relative sizing of passage 158, fluid lines 160 and 164 and passage 158 will be such that there will be insufficient pressure in chamber 148 to bias orbiting scroll member 146 into sealing engagement with non-orbiting scroll member 142 so long as solenoid valve 162 is in a position to maintain fluid communication between suction line 149 and chamber 148. Solenoid valve 162 will be cycled between open and closed positions so as to cyclically load and unload compressor 140 in substantially the same manner as described above.

FIG. 8 shows a modified version 140a of the embodiment of FIG. 7 wherein a plurality of springs 166 are provided. Springs 166 are seated in recesses 168 provided in bearing housing 144a and bear against the end plate of orbiting scroll 146 so as to assist in urging orbiting scroll into sealing engagement with non-orbiting scroll 142. Springs 166 serve primarily to provide an initial biasing force for orbiting scroll member 146 on initial start up of compressor 140a but will also assist in providing more rapid loading of compressor 140a upon closing of solenoid valve 162 during operation.

FIG. 9 shows a further modification 140b of the embodiments of FIGS. 7 and 8. In this embodiment shell 12 is provided with a partition member 170 to separate the interior thereof into a high pressure discharge chamber 172 to which discharge port 174 is connected via conduit 176 and a low suction pressure chamber therebelow within which the compressor is disposed. Additionally, in this embodiment shaft seal 154 has been replaced with a second annular seal 178 positioned radially inwardly and concentric with seal 150b. Thus the area in which crank pin 28 and drive bushing 30 are located will be at suction pressure to thereby avoid any problems associated with providing lubrication thereto from the oil sump which is also at suction pressure. It should be noted that the oil sump in the embodiments of FIGS. 7 and 8 was at discharge pressure and hence do not present any problems with respect to supplying of lubricant to these drive components.

The embodiment 140c of FIG. 10 is substantially identical to that of FIG. 9 with the exception that in addition to the biasing force resulting from intermediate fluid pressure in chamber 148b, a plurality of springs 180 are also provided being positioned between orbiting scroll member 156 and main bearing housing 144 and functioning primarily to assist during start up but also to assist in reloading of compressor 140c similar to that described above with reference to FIG. 8.

In the embodiment of FIG. 11, non-orbiting scroll member 182 is provided with an annular recess 184 within which an annular ring-shaped piston member 186 is movably disposed. The lower surface of annular piston member 186 bears against a radially outwardly extending portion 187 of end plate 189 of orbiting scroll member 146 and radially inner and outer annular seals 188, 190 are provided thereon which sealingly engage radially inner and outer walls of recess 184. A radially extending passage 192 provided in non-orbiting scroll member 182 communicates with the upper portion of recess 184 and has fluid conduit 194 connected to the outer end thereof. Fluid conduit 194 extends outwardly through shell 12 to solenoid valve 196. A second fluid conduit 198 connects solenoid valve 196 to suction line 200 whereas a third fluid conduit 202 connects solenoid valve 196 to discharge line 204.

Under normal fully loaded operating conditions, orbiting scroll member 146 will be axially biased into sealing engagement with non-orbiting scroll member 182 by intermediate fluid pressure in chamber 206 admitted thereto via bleed passage 208. At this time, the area of recess 184 disposed above annular piston member 186 will be vented to suction via solenoid valve 196 and conduits 194 and 198. When conditions indicate partial unloading of the compressor is desirable, solenoid valve 196 will be actuated to place fluid conduit 194 in fluid communication with discharge line 204 via conduit 202. The area above annular piston 186 will then be pressurized by fluid at discharge pressure thereby causing orbiting scroll member 146 to be biased axially downwardly as shown. As noted above, cyclical switching of solenoid valve 196 will result in repetitive loading and unloading of the compressor with the degree of unloading being determined by associated sensors and control module (not shown). It should be noted that in this embodiment, the compressor is shown as a high side machine and thus suction inlet 200 is directly connected to the suction inlet of non-orbiting scroll 182.

The embodiment 208 of FIG. 12 represents a combination of the axial unloading arrangement of FIG. 11 and the orbiting scroll biasing arrangement of FIG. 9 both described above. Accordingly, elements corresponding to like elements shown in and described with reference to FIGS. 9 and 11 are indicated by the same reference numbers. In this embodiment, the intermediate pressure axial biasing chamber 148b for the orbiting scroll is completely separate from the unloading discharge pressure biasing chamber defined by recess 184 and annular piston 186.

In like manner, the embodiment 210 of FIG. 13 represents a combination of the intermediate pressure biasing arrangement of FIG. 8 described above and the axial unloading pressure biasing arrangement of FIG. 11. Accordingly, corresponding elements have been indicated by the same reference numbers used in these respective figures.

FIG. 14 shows an embodiment 212 wherein shell 12 includes an upper chamber 214 at discharge pressure and a lower portion 216 at a pressure intermediate suction and discharge. Accordingly, suction line 234 is directly connected to non-orbiting scroll member 224. Additiona