COMPRESSOR HAVING CAPACITY MODULATION SYSTEM

CROSS-REFERENCE TO RELATED APPLICATIONS [0001] This application claims the benefit of U.S. Provisional Application No. 61/057,470, filed on May 30, 2008. The entire disclosure of the above application is incorporated herein by reference.

FIELD

[0002] The present disclosure relates to compressors, and more specifically to compressors having capacity modulation systems.

BACKGROUND

[0003] This section provides background information related to the present disclosure which is not necessarily prior art. [0004] Scroll compressors include a variety of capacity modulation mechanisms to vary operating capacity of a compressor. The capacity modulation mechanisms may include fluid passages extending through a scroll member to selectively provide fluid communication between compression pockets and another pressure region of the compressor.

SUMMARY

[0005] This section provides a general summary of the disclosure, and is not a comprehensive disclosure of its full scope or all of its features.

[0006] A compressor may include a housing defining a suction pressure region and a discharge pressure region. A first scroll member may be supported within the housing and include a first end plate. A first spiral wrap may extend from a first side of the first end plate. A first chamber may be located on a second side of the first end plate and be in communication with first and second passages. A first aperture may extend through the first end plate to communicate with the first chamber. The second scroll member may be supported within the housing and including a second end plate having a second spiral wrap extending therefrom and meshingly engaged with the first spiral wrap

to form a series of compression pockets. The first aperture may be in communication with one of the compression pockets to provide communication between the compression pocket and the first chamber. The piston may be located within the first chamber and axially displaceable between first and second positions. The piston may isolate the first passage from communication with the second passage when in the first and second positions, communication between the first aperture and the first passage when in the first position, and provide communication between the first aperture and the first passage when in the second position. [0007] The compressor's first passage may be in communication with the suction pressure region.

[0008] The compressor of the first passage may be in communication with the discharge pressure region.

[0009] The compressor may include a valve mechanism in communication with the second passage that selectively provide a pressurized fluid to the second passage to bias the piston toward the first end plate.

[0010] The compressor valve mechanism may selectively provide communication between the second passage and the suction pressure region.

[0011] The compressor may include a floating seal assembly engaged with the housing and the first scroll member to isolate the discharge pressure region from the suction pressure region.

[0012] The compressor piston may be located axially between the floating seal assembly and the first end plate.

[0013] The compressor floating seal assembly and the first scroll member may define a second chamber that is in communication with one of the compression pockets.

[0014] The compressor's first aperture may be in communication with the second chamber and the second chamber maybe in communication with the first chamber. [0015] The compressor piston may be axially displaceable relative to the floating seal assembly.

[0016] The compressor may include a biasing member that biases the piston toward the second position.

[0017] The compressor first chamber may be an annular chamber and the piston is an annular piston. [0018] The compressor's first passage may extend radially through the first scroll member and into the first chamber.

[0019] The compressor's second passage may extend radially through the first scroll member and into the first chamber.

[0020] The compressor first scroll member may be supported within the housing for axial displacement relative to the second scroll member.

[0021] The compressor's piston may abut the first end plate when in the first position.

[0022] 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

[0023] The drawings described herein are for illustration purposes only and are not intended to limit the scope of the present disclosure in any way.

[0024] Figure 1 is a section view of a compressor according to the present disclosure;

[0025] Figure 2 is a plan view of a non-orbiting scroll member of the compressor of Figure 1 ; [0026] Figure 3 is a section view of a non-orbiting scroll, seal assembly, and modulation system of the compressor of Figure 1 ;

[0027] Figure 4 is an additional section view of the non-orbiting scroll, seal assembly, and modulation system of Figure 3;

[0028] Figure 5 is a section view of an alternate non-orbiting scroll, seal assembly, and modulation system according to the present disclosure;

[0029] Figure 6 is an additional section view of the non-orbiting scroll, seal assembly, and modulation system of Figure 5;

[0030] Figure 7 is a section view of an alternate non-orbiting scroll, seal assembly, and modulation system according to the present disclosure;

[0031] Figure 8 is an additional section view of the non-orbiting scroll, seal assembly, and modulation system of Figure 7; [0032] Figure 9 is a section view of an alternate non-orbiting scroll, seal assembly, and modulation system according to the present disclosure;

[0033] Figure 10 is an additional section view of the non-orbiting scroll, seal assembly, and modulation system of Figure 9;

[0034] Figure 1 1 is a fragmentary section view of an alternate compressor according to the present disclosure;

[0035] Figure 12 is an additional fragmentary section view of the compressor of Figure 1 1 ;

[0036] Figure 13 is a fragmentary section view of an alternate compressor according to the present disclosure; [0037] Figure 14 is an additional fragmentary section view of the compressor of Figure 13; and

[0038] Figure 15 is a plan view of the main bearing housing of the compressor of Figure 13.

DETAILED DESCRIPTION

[0039] The following description is merely exemplary in nature and is not intended to limit the present disclosure, application, or uses. It should be understood that throughout the drawings, corresponding reference numerals indicate like or corresponding parts and features. [0040] The present teachings are suitable for incorporation in many different types of scroll and rotary compressors, including hermetic machines, open drive machines and non-hermetic machines. For exemplary purposes, a compressor 10 is shown as a hermetic scroll refrigerant-compressor of the low- side type, i.e., where the motor and compressor are cooled by suction gas in the hermetic shell, as illustrated in the vertical section shown in Figure 1.

[0041] With reference to Figure 1 , compressor 10 may include a hermetic shell assembly 12, a main bearing housing assembly 14, a motor

assembly 16, a compression mechanism 18, a seal assembly 20, a refrigerant discharge fitting 22, a discharge valve assembly 24, a suction gas inlet fitting 26, and a modulation assembly 27. Shell assembly 12 may house main bearing housing assembly 14, motor assembly 16, and compression mechanism 18. [0042] Shell assembly 12 may generally form a compressor housing and may include a cylindrical shell 28, an end cap 30 at the upper end thereof, a transversely extending partition 32, and a base 34 at a lower end thereof. End cap 30 and partition 32 may generally define a discharge chamber 36. Discharge chamber 36 may generally form a discharge muffler for compressor 10. Refrigerant discharge fitting 22 may be attached to shell assembly 12 at opening 38 in end cap 30. Discharge valve assembly 24 may be located within discharge fitting 22 and may generally prevent a reverse flow condition. Suction gas inlet fitting 26 may be attached to shell assembly 12 at opening 40. Partition 32 may include a discharge passage 46 therethrough providing communication between compression mechanism 18 and discharge chamber 36.

[0043] Main bearing housing assembly 14 may be affixed to shell 28 at a plurality of points in any desirable manner, such as staking. Main bearing housing assembly 14 may include a main bearing housing 52, a first bearing 54 disposed therein, bushings 55, and fasteners 57. Main bearing housing 52 may include a central body portion 56 having a series of arms 58 extending radially outwardly therefrom. Central body portion 56 may include first and second portions 60, 62 having an opening 64 extending therethrough. Second portion 62 may house first bearing 54 therein. First portion 60 may define an annular flat thrust bearing surface 66 on an axial end surface thereof. Arm 58 may include apertures 70 extending therethrough and receiving fasteners 57.

[0044] Motor assembly 16 may generally include a motor stator 76, a rotor 78, and a drive shaft 80. Windings 82 may pass through stator 76. Motor stator 76 may be press fit into shell 28. Drive shaft 80 may be rotatably driven by rotor 78. Rotor 78 may be press fit on drive shaft 80. Drive shaft 80 may include an eccentric crank pin 84 having a flat 86 thereon.

[0045] Compression mechanism 18 may generally include an orbiting scroll 104 and a non-orbiting scroll 106. Orbiting scroll 104 may include an end

plate 108 having a spiral vane or wrap 1 10 on the upper surface thereof and an annular flat thrust surface 1 12 on the lower surface. Thrust surface 112 may interface with annular flat thrust bearing surface 66 on main bearing housing 52. A cylindrical hub 1 14 may project downwardly from thrust surface 1 12 and may have a drive bushing 1 16 rotatively disposed therein. Drive bushing 1 16 may include an inner bore in which crank pin 84 is drivingly disposed. Crank pin flat 86 may drivingly engage a flat surface in a portion of the inner bore of drive bushing 1 16 to provide a radially compliant driving arrangement. An Oldham coupling 1 17 may be engaged with the orbiting and non-orbiting scrolls 104, 106 to prevent relative rotation therebetween.

[0046] With additional reference to Figures 2-4, non-orbiting scroll 106 may include an end plate 1 18 having a spiral wrap 120 on a lower surface thereof, a series of radially outwardly extending flanged portions 121 , and an annular ring 123. Spiral wrap 120 may form a meshing engagement with wrap 1 10 of orbiting scroll 104, thereby creating an inlet pocket 122, intermediate pockets 124, 126, 128, 130, and an outlet pocket 132. Non-orbiting scroll 106 may be axially displaceable relative to main bearing housing assembly 14, shell assembly 12, and orbiting scroll 104. Non-orbiting scroll 106 may include a discharge passage 134 in communication with outlet pocket 132 and upwardly open recess 136 which may be in fluid communication with discharge chamber 36 via discharge passage 46 in partition 32.

[0047] Flanged portions 121 may include openings 137 therethrough. Opening 137 may receive bushings 55 therein and bushings 55 may receive fasteners 57. Fasteners 57 may be engaged with main bearing housing 52 and bushings 55 may generally form a guide for axial displacement of non-orbiting scroll 106. Fasteners 57 may additionally prevent rotation of non-orbiting scroll 106 relative to main bearing housing assembly 14.

[0048] Non-orbiting scroll 106 may include an annular recess 138 in the upper surface thereof defined by parallel coaxial inner and outer side walls 140, 142. Annular ring 123 may be disposed within annular recess 138 and may separate annular recess 138 into first and second annular recesses 144, 145. First and second annular recesses 144, 145 may be isolated from one another.

First annular recess 144 may provide for axial biasing of non-orbiting scroll 106 relative to orbiting scroll 104, as discussed below. More specifically, a passage 146 may extend through end plate 1 18 of non-orbiting scroll 106, placing first annular recess 144 in fluid communication with one of intermediate pockets 124, 126, 128, 130. While passage 146 is shown extending into intermediate pocket 126, it is understood that passage 146 may alternatively be placed in communication with any of the other intermediate pockets 124, 128, 130.

[0049] Additional passages 148, 150 may extend through end plate 1 18, placing second annular recess 145 in communication with two of intermediate fluid pockets 124, 128, 130. Second annular recess 145 may be in communication with different ones of intermediate fluid pockets 124, 126, 128, 130 than first annular recess 144. More specifically, second annular recess 145 may be in communication with intermediate fluid pockets 124, 126, 128, 130 located radially outwardly relative to the intermediate fluid pocket 124, 126, 128, 130 in communication with the first annular recess 144. Therefore, first annular recess 144 may operate at a pressure greater than an operating pressure of second annular recess 145. First and second radial passages 152, 154 may extend into second annular recess 145 and may cooperate with modulation assembly 27 as discussed below. [0050] Seal assembly 20 may include a floating seal located within first annular recess 144. Seal assembly 20 may be axially displaceable relative to shell assembly 12 and non-orbiting scroll 106 to provide for axial displacement of non-orbiting scroll 106 while maintaining a sealed engagement with partition 32 to isolate discharge and suction pressure regions of compressor 10 from one another. More specifically, pressure within first annular recess 144 may urge seal assembly 20 into engagement with partition 32 during normal compressor operation.

[0051] Modulation assembly 27 may include a piston assembly 156, a valve assembly 158, and a biasing member 160. The piston assembly 156 may include an annular piston 162 and first and second annular seals 164, 166. Annular piston 162 may be located in second annular recess 145 and first and second annular seals 164, 166 may be engaged with inner and outer side walls

140, 142 to separate second annular recess 145 into first and second portions 168, 170 that are isolated from one another. First portion 168 may be in communication with first radial passage 152 and second portion 170 may be in communication with second radial passage 154. Valve assembly 158 may include a valve member 172 in communication with a pressure source 174 and with first radial passage 152, and therefore first portion 168. Biasing member 160 may include a spring and may be located in second portion 170 and engaged with annular piston 162.

[0052] Annular piston 162 may be displaceable between first and second positions. In the first position (Figure 3), annular piston 162 may seal passages 148, 150 from communication with second portion 170 of second annular recess 145. In the second position (Figure 4), annular piston 162 may be displaced from passages 148, 150, providing communication between passages 148, 150 and second portion 170 of second annular recess 145. Therefore, when annular piston 162 is in the second position, passages 148, 150 may be in communication with a suction pressure region of compressor 10 via second radial passage 154 providing a reduced capacity operating mode for compressor 10.

[0053] Pressure source 174 may include a pressure that is greater than an operating pressure of intermediate pockets 124, 126, 128, 130. Valve member 172 may provide communication between pressure source 174 and first portion 168 of second annular recess 145 to displace annular piston 162 to the first position. Valve member 172 may prevent communication between pressure source 174 and first portion 168 of second annular recess 145 to displace annular piston 162 to the second position. Valve member 172 may additionally vent first portion 168 to the suction pressure region of compressor 10 to displace annular piston 162 to the second position. Biasing member 160 may generally bias annular piston 162 toward the second position.

[0054] With reference to Figures 5 and 6, an alternate non-orbiting scroll 306 and modulation assembly 227 are shown. Non-orbiting scroll 306 may be generally similar to non-orbiting scroll 106. Therefore, it is understood that the description of non-orbiting scroll 106 applies equally to non-orbiting scroll

306 with the exceptions indicated below. Further, it is understood that non- orbiting scroll 306 and modulation assembly 227 may be incorporated into a compressor such as compressor 10 in place of non-orbiting scroll 106 and modulation assembly 27. [0055] Non-orbiting scroll 306 may include a passage 376 extending between and providing communication between first annular recess 344 and first portion 368 of second annular recess 345. Modulation assembly 227 may include a valve assembly 358 having a valve member 372 located in radial passage 352. Valve member 372 may be displaceable between first and second positions to displace annular piston 362 between first and second positions. The first and second positions of annular piston 362 and corresponding capacity reduction may be generally similar to that discussed above for modulation assembly 27. Therefore, for simplicity, the description will not be repeated with the understanding that the above description applies equally to the modulation assembly 227.

[0056] Valve member 372 may provide communication between the first and second annular recesses 344, 345 when valve member 372 is in the first position (Figure 5). Since first annular recess 344 operates at a higher pressure than second annular recess 345, annular piston 362 may be displaced (or held) in the first position. Valve member 372 may be displaced to the second position and vent first portion 368 of second annular recess 345 to suction pressure in order to displace annual piston 362 to the second position (Figure 6). In the second position, valve member 372 may seal passage 376 to isolate first and second annular recesses 344, 345 from one another. When first and second annular recesses 344, 345 are isolated from one another, biasing member 360 may urge annular piston 362 to the second position where passages 348, 350 are in communication with a suction pressure region.

[0057] With reference to Figures 7 and 8, an alternate non-orbiting scroll 506 and modulation assembly 427 are shown. Non-orbiting scroll 506 may be generally similar to non-orbiting scroll 106. Therefore, it is understood that the description of non-orbiting scroll 106 applies equally to non-orbiting scroll 506 with the exceptions indicated below. Further, it is understood that non-

orbiting scroll 506 and modulation assembly 427 may be incorporated into a compressor such as compressor 10 in place of non-orbiting scroll 106 and modulation assembly 27.

[0058] Non-orbiting scroll 506 may include passages 576 extending through annular ring 523 and providing communication between first annular recess 544 and first portion 568 of second annular recess 545. Second portion 570 of second annular recess 545 may be isolated from intermediate pockets. Radial passage 552 may be in communication with a suction pressure region and radial passage 554 may be in communication with modulation assembly 427. Modulation assembly 427 may be generally similar to modulation assembly 27. Therefore, it is understood that the description of modulation assembly 27 applies to modulation assembly 427 with the exceptions noted below.

[0059] Modulation assembly 427 may include a valve assembly 558 including a valve member 572 in communication with radial passage 554, a pressure source 574 and the suction pressure region. Pressure source 574 may include a pressure that is greater than an operating pressure within first annular recess 544. Valve member 572 may provide communication between pressure source 574 and second portion 570 of second annular recess 545 to bias annular piston 562 into a first position (Figure 7). Annular piston 562 may seal passage 576 when in the first position to prevent fluid communication between first annular recess 544 and the first portion 568 of second annular recess 545 when in the first position.

[0060] Valve member 572 may vent second portion 570 of second annular recess 545 to a suction pressure region and biasing member 560 may act on annular piston 562 to displace annular piston 562 to a second position (Figure 8). Annular piston 562 may be displaced from passage 576 when in the second position. Passage 576 may therefore provide communication between first annular recess 544 and a suction pressure region when annular piston 562 is in the second position. Providing communication between the first annular recess 544 and the suction pressure region may remove the axial biasing force that normally urges non-orbiting scroll 506 toward an orbiting scroll (not shown) providing a reduced compressor operating capacity by providing clearance

between the non-orbiting scroll end plate and the orbiting scroll wrap, as well as the non-orbiting scroll wrap and the orbiting scroll end plate. The capacity is reduced to zero when the axial biasing force is removed and the axial clearance exists between the orbiting and non-orbiting scrolls. In order to modulate the compressor to a desired capacity between about 0% to 100%, the piston may be actuated in a pulse width modulation manner to achieve a desired capacity. The scrolls will switch between a generally sealed state and an un-sealed state to provide a desired output capacity.

[0061] With reference to Figures 9 and 10, an alternate non-orbiting scroll 706 and modulation assembly 627 are shown. Non-orbiting scroll 706 may be generally similar to non-orbiting scroll 106. Therefore, it is understood that the description of non-orbiting scroll 106 applies equally to non-orbiting scroll 706 with the exceptions indicated below. Further, it is understood that non- orbiting scroll 706 and modulation assembly 627 may be incorporated into a compressor such as compressor 10 in place of non-orbiting scroll 106 and modulation assembly 27.

[0062] Non-orbiting scroll 706 may include a radial passage 754 extending between and in communication with second portion 770 of second annular recess 745 and a discharge pressure region (rather than a suction pressure region shown in Figures 3 and 4 for second radial passage 154). Pressure source 774 may include a pressure that is greater than an operating pressure of second portion 770 of second annular recess 745. Valve member 772 may provide communication between pressure source 774 and first portion 768 of second annular recess 745 to displace annular piston 762 to the first position (Figure 9).

[0063] Valve member 772 may prevent communication between pressure source 774 and first portion 768 of second annular recess 745 to displace annular piston 762 to the second position (Figure 10). Valve member 772 may additionally vent first portion 768 to a suction pressure region to displace annular piston 762 to the second position. Biasing member 760 may generally bias annular piston 762 toward the second position. The second position of annular piston 762 may provide communication between second

portion 770 of second annular recess 745, and therefore passages 748, 750, and a discharge pressure region to provide a change in a compression volume ratio for the compressor.

[0064] With reference to Figures 1 1 and 12, an alternate main bearing housing assembly 814, compression mechanism 818, and a capacity adjustment assembly 827 are illustrated. Capacity adjustment assembly 827 may include a modulation assembly. Main bearing housing assembly 814 and compression mechanism 818 may be generally similar to main bearing housing assembly 14 and compression mechanism 18. Therefore, for simplicity, it is understood that the description of main bearing housing assembly 14 and compression mechanism 18 above applies equally to main bearing housing assembly 814 and compression mechanism 818 with the exceptions indicated below. Further, it is understood that main bearing housing assembly 814, compression mechanism 818, and capacity adjustment assembly 827 may be incorporated into a compressor similar to compressor 10 in place of main bearing housing assembly 14, compression mechanism 18, and modulation assembly 27.

[0065] Main bearing housing assembly 814 may include main bearing housing 852. Main bearing housing 852 may include an annular passage 853 that forms an annular recess extending into thrust bearing surface 866. First radial passages 952 may extend radially through first portion 860 and into annular passage 853, providing communication between annular passage 853 and a suction pressure region. A second radial passage 954 may extend radially through first portion 860 and into annular passage 853 and may be in communication with capacity adjustment assembly 827, as discussed below. [0066] Compression mechanism 818 may include orbiting scroll 904 and non-orbiting scroll 906. Orbiting scroll 904 may include first and second passages 948, 950 extending through end plate 908 and providing communication between two of intermediate fluid pockets 924, 926, 928, 930 and annular passage 853. Non-orbiting scroll 906 may include a single annular recess 944 having seal assembly 920 disposed therein. Passage 946 may provide communication between annular recess 944 and one of intermediate fluid pockets 924, 926, 928, 930. The intermediate fluid pocket 924, 926, 928,

930 in communication annular recess 944 may be different than the two of intermediate fluid pockets 924, 926, 928, 930 in communication with annular passage 853. More specifically, the intermediate fluid pocket 924, 926, 928, 930 in communication annular recess 944 may be located radially inwardly relative to and operate at a pressure greater than the two of intermediate fluid pockets 924, 926, 928, 930 in communication with annular passage 853.

[0067] Capacity adjustment assembly 827 may include a piston assembly 956, a valve assembly 958, and a biasing member 960. The piston assembly 956 may include an annular piston 962 located in annular passage 853. Annular piston 962 may be displaceable between first and second positions. In the first position (Figure 1 1 ), annular piston 962 may isolate first and second passages 948, 950 from first radial passage 952. In the second position, (Figure 12), annular piston 962 may be displaced to provide communication between first and second passages 948, 950 and first radial passage 952. In the second position, first and second passages 948, 950 may be in communication with a suction pressure region via first radial passage 952 providing a reduced capacity operating mode. In both the first and second positions, annular piston 962 may isolate first and second radial passages 952, 954 from one another and may additionally isolate first and second passages 948, 950 from second radial passage 954.

[0068] Valve assembly 958 may include a valve member 972 in communication with a pressure source 974 and with second radial passage 954. Biasing member 960 may include a spring and may be located in annular passage 853 and engaged with annular piston 962. Valve assembly 958 may displace annular piston 962 between the first and second positions. Valve member 972 may provide communication between pressure source 974 and second radial passage 954 to bias annular piston to the first position. The pressure source may include a pressure that is greater than an operating pressure of intermediate pockets 924, 926, 928, 930. Valve member 972 may prevent communication between pressure source 974 and second radial passage 954 and may vent second radial passage to a suction pressure region to allow annular piston 962 to be displaced to the second position. Biasing

member 960 may generally bias annular piston 962 to the second position when second radial passage 954 is vented to suction pressure.

[0069] With reference to Figures 13-15, an alternate main bearing housing assembly 1014, compression mechanism 1018 and a capacity adjustment assembly 1027 are illustrated. Capacity adjustment assembly 1027 may include a vapor injection assembly. Main bearing housing assembly 1014 and compression mechanism 1018 may be generally similar to main bearing housing assembly 14 and compression mechanism 18. Therefore, for simplicity, it is understood that the description of main bearing housing assembly 14 and compression mechanism 18 above applies equally to main bearing housing assembly 1014 and compression mechanism 1018 with the exceptions indicated below. Further, it is understood that main bearing housing assembly 1014, compression mechanism 1018, and capacity adjustment assembly 1027 may be incorporated into a compressor similar to compressor 10 in place of main bearing housing assembly 14, compression mechanism 18, and modulation assembly 27.

[0070] Main bearing housing assembly 1014 may include main bearing housing 1052. Main bearing housing 1052 may include first and second recesses 1053, 1054 extending axially into thrust bearing surface 1066. A first passage 1152 may extend through main bearing housing 1052 radially inward from an actuation control port 1 154 to first recess 1053 and a second passage 1 153 may extend through main bearing housing 1052 radially inward from actuation control port 1 154 to second recess 1054. A third passage 1 155 may extend through main bearing housing 1052 radially inward from an injection port 1 158 to first recess 1053 and a fourth passage 1 157 may extend through main bearing housing 1052 radially inward from injection port 1 158 to second recess 1054.

[0071] Compression mechanism 1018 may include orbiting scroll 1 104 and non-orbiting scroll 1 106. Orbiting scroll 1 104 may include first and second passages 1 148, 1 150 extending through end plate 1 108. First passage 1148 may provide communication between one of intermediate fluid pockets 1 124, 1 126, 1 128, 1 130, 1 132 and first recess 1053. Second passage 1150 may

provide communication between another one of intermediate fluid pockets 1 124, 1 126, 1 128, 1 130, 1 132 and second recess 1054. Non-orbiting scroll 1 106 may include a single annular recess 1 144 having seal assembly 1 120 disposed therein. Passage 1 146 may provide communication between annular recess 1 144 and one of intermediate fluid pockets 1124, 1 126, 1 128, 1 130, 1 132.

[0072] The intermediate fluid pocket 1 124, 1 126, 1 128, 1 130, 1 132 in communication annular recess 1 144 may be different than the two of intermediate fluid pockets 1 124, 1 126, 1 128, 1 130, 1 132 in communication with first and second recesses 1053, 1054. More specifically, the intermediate fluid pocket 1 124, 1 126, 1128, 1 130, 1 132 in communication annular recess 1 144 may be located radially inwardly relative to and operate at a pressure greater than the two of intermediate fluid pockets 1 124, 1 126, 1 128, 1130, 1 132 in communication with first and second recesses 1053, 1054.

[0073] Capacity adjustment assembly 1027 may include a piston assembly 1 156, a vapor source 1 159, and an actuation mechanism 1 160. The piston assembly 1 156 may include first and second pistons 1162, 1 163. First piston 1162 may be located in first recess 1053 and second piston 1 163 may be located in second recess 1054. Actuation mechanism 1 160 may include a valve in communication with first and second pressure sources and actuation control port 1154. The first pressure source may include a fluid operating at a pressure greater than the operating pressure provided by first and second passages 1 148, 1 150, such as discharge pressure. The second pressure source may include a fluid operating at a pressure less than the operating pressure provided by first and second passages 1 148, 1 150, such as suction pressure. Actuation mechanism 1 160 may selectively displace first and second pistons 1 162, 1 163 from a first position (Figure 13) to a second position (Figure 14).

[0074] First piston 1 162 may isolate first passage 1 148 from communication with actuation control port 1154 and second piston 1 163 may isolate second passage 1 150 from communication with actuation control port 1 154 when in the first and second positions. Additionally, first and second pistons 1 162, 1 163 may isolate actuation control port 1 154 from communication with injection port 1 158 when in the first and second positions.

[0075] During operation, the first and second pistons 1 162, 1 163 may be in the first position during normal compressor operation. Normal compressor operation may include a full operating capacity for the compressor. First and second pistons 1 162, 1 163 may be in the first position (Figure 13) when actuation mechanism 1 160 provides the first pressure source to first and second recesses 1053, 1054 to isolate first and second passages 1 148, 1 150 from communication with vapor source 1 159. When increased capacity is desired, first and second pistons 1 162, 1163 may be displaced to the second position (Figure 14) by placing first and second recesses 1053, 1054 in communication with the second pressure source. In the second position, vapor source 1 159 injects vapor into the compression mechanism 1018 via first and second passages 1148, 1150.

[0076] The terms "first", "second", etc. are used throughout the description for clarity only and are not intended to limit similar terms in the claims.