Abstract:
A compressor includes a shell assembly, first and second scroll members and a capacity modulation assembly. The first and second scroll members form a series of pockets. A first modulation port defined in the first scroll member is in communication with a first pocket. The capacity modulation assembly is in communication with the first modulation port and is operable in full, partial and first and second pulse width modulation (PWM) capacity modes. The full capacity mode includes the first modulation port isolated from a suction pressure region of the compressor, the partial capacity mode includes the first modulation port in communication with the suction pressure region, the first PWM capacity mode includes a capacity between full and partial capacity via PWM between the full and partial capacity modes and the second PWM capacity mode includes a capacity between full and zero capacity by providing PWM of the capacity modulation assembly.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
       [0001]    This application is a continuation of U.S. patent application Ser. No. 12/754,920 filed on Apr. 6, 2010 which claims the benefit of U.S. Provisional Application No. 61/167,309, filed on Apr. 7, 2009. The entire disclosures of each of the above applications are incorporated herein by reference. 
     
    
     FIELD 
       [0002]    The present disclosure relates to compressor capacity modulation assemblies. 
       BACKGROUND 
       [0003]    This section provides background information related to the present disclosure and which is not necessarily prior art. 
         [0004]    Compressors may be designed for a variety of operating conditions. The operating conditions may require different output from the compressor. In order to provide for more efficient compressor operation, a capacity modulation assembly may be included in a compressor to vary compressor output depending on the operating condition. 
       SUMMARY 
       [0005]    This section provides a general summary of the disclosure, and is not comprehensive of its full scope or all of its features. 
         [0006]    A compressor may include a shell assembly, a first scroll member, a second scroll member and a capacity modulation assembly. The shell assembly may define a suction pressure region and a discharge pressure region. The first scroll member may be supported within the shell assembly and may include a first end plate having a discharge passage, a first spiral wrap extending from the first end plate and a first modulation port extending through the first end plate. The second scroll member may be supported within the shell assembly and may include a second end plate having a second spiral wrap extending therefrom. The first and second spiral wraps may be meshingly engaged and may form a series of pockets during orbital displacement of the second scroll member relative to the first scroll member. The first modulation port may be in communication with a first of the pockets. The capacity modulation assembly may be located within the shell assembly and may be in communication with the first modulation port. The capacity modulation assembly may be operable in a full capacity mode, a partial capacity mode and first and second pulse width modulation capacity modes. The full capacity mode may include the first modulation port isolated from a suction pressure region of the compressor to operate the compressor at a full capacity. The partial capacity mode may include the first modulation port in communication with the suction pressure region to operate the compressor at partial capacity between the full capacity and zero capacity. The first pulse width modulation capacity mode may include a capacity between the full capacity and the partial capacity by providing pulse width modulation of the capacity modulation assembly between the full capacity mode and the partial capacity mode. The second pulse width modulation capacity mode may include compressor operation at a capacity between the full capacity and zero capacity by providing pulse width modulated control of said capacity modulation assembly. 
         [0007]    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 
         [0008]    The drawings described herein are for illustrative purposes only of selected embodiments and not all possible implementations, and are not intended to limit the scope of the present disclosure. 
           [0009]      FIG. 1  is a section view of a compressor according to the present disclosure; 
           [0010]      FIG. 2  is a section view of the non-orbiting scroll member and capacity modulation assembly of  FIG. 1  in a first operating mode; 
           [0011]      FIG. 3  is a section view of the non-orbiting scroll member and capacity modulation assembly of  FIG. 1  in a second operating mode; 
           [0012]      FIG. 4  is a perspective exploded view of the non-orbiting scroll member and capacity modulation assembly of  FIG. 1 ; 
           [0013]      FIG. 5  is a section view of an alternate non-orbiting scroll member and capacity modulation assembly according to the present disclosure in a first operating mode; 
           [0014]      FIG. 6  is a section view of the non-orbiting scroll member and capacity modulation assembly of  FIG. 5  in a second operating mode; 
           [0015]      FIG. 7  is a section view of an alternate non-orbiting scroll member and capacity modulation assembly according to the present disclosure in a first operating mode; 
           [0016]      FIG. 8  is a section view of the non-orbiting scroll member and capacity modulation assembly of  FIG. 7  in a second operating mode; 
           [0017]      FIG. 9  is a section view of an alternate non-orbiting scroll member and capacity modulation assembly according to the present disclosure in a first operating mode; 
           [0018]      FIG. 10  is a section view of the non-orbiting scroll member and capacity modulation assembly of  FIG. 9  in a second operating mode; 
           [0019]      FIG. 11  is a section view of an alternate non-orbiting scroll member according to the present disclosure; 
           [0020]      FIG. 12  is a schematic illustration of the capacity modulation assembly of  FIG. 2  in the first operating mode; 
           [0021]      FIG. 13  is a schematic illustration of the capacity modulation assembly of  FIG. 3  in the second operating mode; 
           [0022]      FIG. 14  is a schematic illustration of an alternate capacity modulation assembly in the first operating mode; 
           [0023]      FIG. 15  is a schematic illustration of the alternate capacity modulation assembly of  FIG. 14  in the second operating mode; 
           [0024]      FIG. 16  is a schematic illustration of an alternate capacity modulation assembly in the first operating mode; 
           [0025]      FIG. 17  is a schematic illustration of the alternate capacity modulation assembly of  FIG. 16  in the second operating mode; 
           [0026]      FIG. 18  is a schematic illustration of an alternate capacity modulation assembly in the first operating mode; 
           [0027]      FIG. 19  is a schematic illustration of the alternate capacity modulation assembly of  FIG. 18  in the second operating mode; 
           [0028]      FIG. 20  is a schematic illustration of the capacity modulation assembly of  FIG. 7  in the first operating mode; 
           [0029]      FIG. 21  is a schematic illustration of the capacity modulation assembly of  FIG. 8  in the second operating mode; 
           [0030]      FIG. 22  is a schematic illustration of an alternate capacity modulation assembly in the first operating mode; 
           [0031]      FIG. 23  is a schematic illustration of the alternate capacity modulation assembly of  FIG. 22  in the second operating mode; 
           [0032]      FIG. 24  is a schematic illustration of an alternate capacity modulation assembly in the first operating mode; 
           [0033]      FIG. 25  is a schematic illustration of the alternate capacity modulation assembly of  FIG. 24  in the second operating mode; 
           [0034]      FIG. 26  is a schematic illustration of an alternate capacity modulation assembly in the first operating mode; 
           [0035]      FIG. 27  is a schematic illustration of the alternate capacity modulation assembly of  FIG. 26  in the second operating mode; 
           [0036]      FIG. 28  is a section view of an alternate non-orbiting scroll member and capacity modulation assembly according to the present disclosure in a first operating mode; 
           [0037]      FIG. 29  is a section view of the non-orbiting scroll member and capacity modulation assembly of  FIG. 28  in a second operating mode; and 
           [0038]      FIG. 30  is a schematic illustration of the capacity modulation assembly of  FIGS. 14 and 15  in a third operating mode. 
       
    
    
       [0039]    Corresponding reference numerals indicate corresponding parts throughout the several views of the drawings. 
       DETAILED DESCRIPTION 
       [0040]    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. 
         [0041]    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  FIG. 1 . 
         [0042]    With reference to  FIG. 1 , compressor  10  may include a hermetic shell assembly  12 , a 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 capacity modulation assembly  28 . Shell assembly  12  may house bearing housing assembly  14 , motor assembly  16 , compression mechanism  18 , and capacity modulation assembly  28 . 
         [0043]    Shell assembly  12  may generally form a compressor housing and may include a cylindrical shell  29 , an end cap  32  at the upper end thereof, a transversely extending partition  34 , and a base  36  at a lower end thereof. End cap  32  and partition  34  may generally define a discharge chamber  38 . Discharge chamber  38  may generally form a discharge muffler for compressor  10 . While illustrated as including discharge chamber  38 , it is understood that the present disclosure applies equally to direct discharge configurations. Refrigerant discharge fitting  22  may be attached to shell assembly  12  at opening  40  in end cap  32 . 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  42 . Partition  34  may include a discharge passage  44  therethrough providing communication between compression mechanism  18  and discharge chamber  38 . 
         [0044]    Bearing housing assembly  14  may be affixed to shell  29  at a plurality of points in any desirable manner, such as staking. Bearing housing assembly  14  may include a main bearing housing  46 , a bearing  48  disposed therein, bushings  50 , and fasteners  52 . Main bearing housing  46  may house bearing  48  therein and may define an annular flat thrust bearing surface  54  on an axial end surface thereof. Main bearing housing  46  may include apertures  56  extending therethrough and receiving fasteners  52 . 
         [0045]    Motor assembly  16  may generally include a motor stator  58 , a rotor  60 , and a drive shaft  62 . Motor stator  58  may be press fit into shell  29 . Drive shaft  62  may be rotatably driven by rotor  60  and may be rotatably supported within first bearing  48 . Rotor  60  may be press fit on drive shaft  62 . Drive shaft  62  may include an eccentric crank pin  64  having a flat  66  thereon. 
         [0046]    Compression mechanism  18  may generally include an orbiting scroll  68  and a non-orbiting scroll  70 . Orbiting scroll  68  may include an end plate  72  having a spiral vane or wrap  74  on the upper surface thereof and an annular flat thrust surface  76  on the lower surface. Thrust surface  76  may interface with annular flat thrust bearing surface  54  on main bearing housing  46 . A cylindrical hub  78  may project downwardly from thrust surface  76  and may have a drive bushing  80  rotatably disposed therein. Drive bushing  80  may include an inner bore in which crank pin  64  is drivingly disposed. Crank pin flat  66  may drivingly engage a flat surface in a portion of the inner bore of drive bushing  80  to provide a radially compliant driving arrangement. An Oldham coupling  82  may be engaged with the orbiting and non-orbiting scrolls  68 ,  70  to prevent relative rotation therebetween. 
         [0047]    With additional reference to  FIGS. 2-4 , non-orbiting scroll  70  may include an end plate  84  defining a discharge passage  92  and having a spiral wrap  86  extending from a first side  87  thereof, an annular hub  88  extending from a second side  89  thereof opposite the first side, and a series of radially outwardly extending flanged portions  90  ( FIG. 1 ) engaged with fasteners  52 . Fasteners  52  may rotationally fix non-orbiting scroll  70  relative to main bearing housing  46  while allowing axial displacement of non-orbiting scroll  70  relative to main bearing housing  46 . Spiral wraps  74 ,  86  may be meshingly engaged with one another defining pockets  94 ,  96 ,  98 ,  100 ,  102 ,  104  ( FIG. 1 ). It is understood that pockets  94 ,  96 ,  98 ,  100 ,  102 ,  104  change throughout compressor operation. 
         [0048]    A first pocket, pocket  94  in  FIG. 1 , may define a suction pocket in communication with a suction pressure region  106  of compressor  10  operating at a suction pressure (P s ) and a second pocket, pocket  104  in  FIG. 1 , may define a discharge pocket in communication with a discharge pressure region  108  of compressor  10  operating at a discharge pressure (P d ) via discharge passage  92 . Pockets intermediate the first and second pockets, pockets  96 ,  98 ,  100 ,  102  in  FIG. 1 , may form intermediate compression pockets operating at intermediate pressures between the suction pressure (P s ) and the discharge pressure (P d ). 
         [0049]    Referring again to  FIGS. 2-4 , end plate  84  may additionally include a biasing passage  110  and first and second modulation ports  112 ,  114 . Biasing passage  110  and first and second modulation ports  112 ,  114  may each be in fluid communication with one of the intermediate compression pockets. Biasing passage  110  may be in fluid communication with one of the intermediate compression pockets operating at a higher pressure than ones of intermediate compression pockets in fluid communication with first and second modulation ports  112 ,  114 . 
         [0050]    Annular hub  88  may include first and second portions  116 ,  118  axially spaced from one another forming a stepped region  120  therebetween. First portion  116  may be located axially between second portion  118  and end plate  84  and may have an outer radial surface  122  defining a first diameter (D 1 ) greater than or equal to a second diameter (D 2 ) defined by an outer radial surface  124  of second portion  118 . 
         [0051]    Capacity modulation assembly  28  may include a modulation valve ring  126 , a modulation lift ring  128 , a retaining ring  130 , and a modulation control valve assembly  132 . Modulation valve ring  126  may include an inner radial surface  134 , an outer radial surface  136 , a first axial end surface  138  defining an annular recess  140  and a valve portion  142 , and first and second passages  144 ,  146 . Inner radial surface  134  may include first and second portions  148 ,  150  defining a second axial end surface  152  therebetween. First portion  148  may define a third diameter (D 3 ) less than a fourth diameter (D 4 ) defined by the second portion  150 . The first and third diameters (D 1 , D 3 ) may be approximately equal to one another and the first portions  116 ,  148  may be sealingly engaged with one another via a seal  154  located radially therebetween. More specifically, seal  154  may include an o-ring seal and may be located within an annular recess  156  in first portion  148  of modulation valve ring  126 . Alternatively, the o-ring seal could be located in an annular recess in annular hub  88 . 
         [0052]    Modulation lift ring  128  may be located within annular recess  140  and may include an annular body defining inner and outer radial surfaces  158 ,  160 , and first and second axial end surfaces  159 ,  161 . Inner and outer radial surfaces  158 ,  160  may be sealingly engaged with sidewalls  162 ,  164  of annular recess  140  via first and second seals  166 ,  168 . More specifically, first and second seals  166 ,  168  may include o-ring seals and may be located within annular recesses  170 ,  172  in inner and outer radial surfaces  158 ,  160  of modulation lift ring  128 . Modulation valve ring  126  and modulation lift ring  128  may cooperate to define a modulation control chamber  174  between annular recess  140  and first axial end surface  159 . First passage  144  may be in fluid communication with modulation control chamber  174 . Second axial end surface  161  may face end plate  84  and may include a series of protrusions  177  defining radial flow passages  178  therebetween. 
         [0053]    Seal assembly  20  may form a floating seal assembly and may be sealingly engaged with non-orbiting scroll  70  and modulation valve ring  126  to define an axial biasing chamber  180 . More specifically, seal assembly  20  may be sealingly engaged with outer radial surface  124  of annular hub  88  and second portion  150  of modulation valve ring  126 . Axial biasing chamber  180  may be defined axially between an axial end surface  182  of seal assembly  20  and second axial end surface  152  of modulation valve ring  126  and stepped region  120  of annular hub  88 . Second passage  146  may be in fluid communication with axial biasing chamber  180 . 
         [0054]    Retaining ring  130  may be axially fixed relative to non-orbiting scroll  70  and may be located within axial biasing chamber  180 . More specifically, retaining ring  130  may be located within a recess in first portion  116  of annular hub  88  axially between seal assembly  20  and modulation valve ring  126 . Retaining ring  130  may form an axial stop for modulation valve ring  126 . Modulation control valve assembly  132  may include a solenoid operated valve and may be in fluid communication with first and second passages  144 ,  146  in modulation valve ring  126  and suction pressure region  106 . 
         [0055]    With additional reference to  FIGS. 12 and 13 , during compressor operation, modulation control valve assembly  132  may be operated in first and second modes.  FIGS. 12 and 13  schematically illustrate operation of modulation control valve assembly  132 . In the first mode, seen in  FIGS. 2 and 12 , modulation control valve assembly  132  may provide fluid communication between modulation control chamber  174  and suction pressure region  106 . More specifically, modulation control valve assembly  132  may provide fluid communication between first passage  144  and suction pressure region  106  during operation in the first mode. In the second mode, seen in  FIGS. 3 and 13 , modulation control valve assembly  132  may provide fluid communication between modulation control chamber  174  and axial biasing chamber  180 . More specifically, modulation control valve assembly  132  may provide fluid communication between first and second passages  144 ,  146  during operation in the second mode. 
         [0056]    In an alternate capacity modulation assembly  928 , seen in  FIGS. 14 and 15 , a modulation control valve assembly  1032  may include first and second modulation control valves  1031 ,  1033 . Capacity modulation assembly  928  may be incorporated into compressor  10  as discussed below. First modulation control valve  1031  may be in communication with modulation control chamber  1074 , biasing chamber  1080 , and second modulation control valve  1033 . Second modulation control valve  1033  may be in communication with suction pressure region  1006 , first modulation control valve  1031 , and modulation control chamber  1074 . Modulation control valve assembly  1032  may be operated in first and second modes. 
         [0057]    In the first mode, seen in  FIG. 14 , first modulation control valve  1031  may be closed, isolating modulation control chamber  1074  from biasing chamber  1080 , and second modulation control valve  1033  may be open, providing communication between modulation control chamber  1074  and suction pressure region  1006 . In the second mode, seen in  FIG. 15 , first modulation control valve  1031  may be open, providing communication between modulation control chamber  1074  and biasing chamber  1080 , and second modulation control valve  1033  may be closed, isolating modulation control chamber  1074  from suction pressure region  1006 . 
         [0058]    Modulation control valve assembly  1032  may be modulated between the first and second modes to create a compressor operating capacity that is between a fully loaded capacity (first mode) and a part loaded capacity (second mode). Pulse-width-modulation of the opening and closing of first and second modulation control valves  1031 ,  1033  may be utilized to create this intermediate capacity. Second modulation control valve  1033  may be open during the first mode as seen in  FIG. 14 . Alternatively, second modulation control valve  1033  may be opened, for example, between 0.2 and 1.0 seconds when transitioning from the second mode to the first mode and then closed to be ready for transitioning to the second mode. This allows the modulation control chamber  1074  to reach suction pressure (P s ) to allow compressor operation in the first mode. 
         [0059]    Alternatively, modulation control valve assembly  1032  may be modulated between the second mode and a third mode. The third mode is schematically illustrated in  FIG. 30  and provides an unloaded (zero capacity) condition. In the third mode, first and second modulation control valves  1031 ,  1033  may be open. Therefore, modulation control chamber  1074  and biasing chamber  1080  are both in communication with suction pressure region  1006 . Modulation control valve assembly  1032  may be modulated between the second and third modes to create a compressor operating capacity that is between the part loaded capacity (second mode) and the unloaded capacity (third mode). Pulse-width-modulation of the opening and closing of first and second modulation control valves  1031 ,  1033  may be utilized to create this intermediate capacity. 
         [0060]    Alternatively, modulation control valve assembly  1032  may be modulated between the first and third modes to create a compressor operating capacity that is between the fully loaded capacity (first mode) and the unloaded capacity (third mode). Pulse-width-modulation of the opening and closing of first and second modulation control valves  1031 ,  1033  may be utilized to create this intermediate capacity. When transitioning from the third mode to the first mode, second modulation control valve  1033  may remain open and first modulation control valve  1031  may be modulated between opened and closed positions. Alternatively, second modulation control valve  1033  may be closed when transitioning from the third mode to the first mode. In such arrangements, second modulation control valve  1033  may be closed after first modulation control valve  1031  by a delay (e.g., less than one second) to ensure that modulation control chamber  1074  is maintained at suction pressure (P s ) and does not experience additional biasing pressure (P i1 ). 
         [0061]    An alternate capacity modulation assembly  1028  is shown in  FIGS. 16 and 17 . Capacity modulation assembly  1028  may be incorporated into compressor  10  as discussed below. In the arrangement of  FIGS. 16 and 17 , modulation control chamber  1174  may be in communication with biasing chamber  1180  via a first passage  1131 . Modulation control valve assembly  1132  may be in communication with modulation control chamber  1174  and suction pressure region  1106 . Modulation control valve assembly  1132  may be operated in first and second modes. 
         [0062]    In the first mode, seen in  FIG. 16 , modulation control valve assembly  1132  may be open, providing communication between modulation control chamber  1174  via a second passage  1133 . First passage  1131  may define a greater flow restriction than second passage  1133 . The greater flow restriction of first passage  1131  relative to second passage  1133  may generally prevent a total loss of biasing pressure within biasing chamber  1180  during the first mode. In the second mode, seen in  FIG. 17 , modulation control valve assembly  1132  may be closed, isolating modulation control chamber  1174  from suction pressure region  1106 . 
         [0063]    Another alternate capacity modulation assembly  1128  is shown in  FIGS. 18 and 19 . Capacity modulation assembly  1128  may be incorporated into compressor  10  as discussed below. In the arrangement of  FIGS. 18 and 19 , modulation control chamber  1274  may be in communication with suction pressure region  1206  via a first passage  1231 . Modulation control valve assembly  1232  may be in communication with modulation control chamber  1274  and biasing chamber  1280 . Modulation control valve assembly  1232  may be operated in first and second modes. 
         [0064]    In the first mode, seen in  FIG. 18 , modulation control valve assembly  1232  may be closed, isolating modulation control chamber  1274  from biasing chamber  1280 . In the second mode, seen in  FIG. 19 , modulation control valve assembly  1232  may be open, providing communication between modulation control chamber  1274  and biasing chamber  1280  via a second passage  1233 . First passage  1231  may define a greater flow restriction than second passage  1233 . The greater flow restriction of first passage  1231  relative to second passage  1233  may generally prevent a total loss of biasing pressure within biasing chamber  1280  during the second mode. 
         [0065]    Modulation valve ring  126  may define a first radial surface area (A 1 ) facing away from non-orbiting scroll  70  radially between first and second portions  148 ,  150  of inner radial surface  134  of modulation valve ring  126  (A 1 =(π)(D 4   2 −D 3   2 )/4). Inner sidewall  162  may define a diameter (D 5 ) less than a diameter (D 6 ) defined by outer sidewall  164 . Modulation valve ring  126  may define a second radial surface area (A 2 ) opposite first radial surface area (A 1 ) and facing non-orbiting scroll  70  radially between sidewalls  162 ,  164  of inner radial surface  134  of modulation valve ring  126  (A 2 =(π)(D 6   2 −D 5   2 )/4). First radial surface area (A 1 ) may be less than second radial surface area (A 2 ). Modulation valve ring  126  may be displaced between first and second positions based on the pressure provided to modulation control chamber  174  by modulation control valve assembly  132 . Modulation valve ring  126  may be displaced by fluid pressure acting directly thereon, as discussed below. 
         [0066]    A first intermediate pressure (P i1 ) within axial biasing chamber  180  applied to first radial surface area (A 1 ) may provide a first axial force (F 1 ) urging modulation valve ring  126  axially toward non-orbiting scroll  70  during both the first and second modes. When modulation control valve assembly  132  is operated in the first mode, modulation valve ring  126  may be in the first position ( FIG. 2 ). In the first mode, suction pressure (P S ) within modulation control chamber  174  may provide a second axial force (F 2 ) opposite first axial force (F 1 ) urging modulation valve ring  126  axially away from non-orbiting scroll  70 . First axial force (F 1 ) may be greater than second axial force (F 2 ). Therefore, modulation valve ring  126  may be in the first position during operation of modulation control valve assembly  132  in the first mode. The first position may include valve portion  142  of modulation valve ring  126  abutting end plate  84  and closing first and second modulation ports  112 ,  114 . 
         [0067]    When modulation control valve assembly  132  is operated in the second mode, modulation valve ring  126  may be in the second position ( FIG. 3 ). In the second mode, first intermediate pressure (P i1 ) within modulation control chamber  174  may provide a third axial force (F 3 ) acting on modulation valve ring  126  and opposite first axial force (F 1 ) urging modulation valve ring  126  axially away from non-orbiting scroll  70 . Since modulation control chamber  174  and axial biasing chamber  180  are in fluid communication with one another during operation of the modulation control valve assembly  132  in the second mode, both may operate at approximately the same first intermediate pressure (P i1 ). Third axial force (F 3 ) may be greater than first axial force (F 1 ) since second radial surface area (A 2 ) is greater than first radial surface area (A 1 ). Therefore, modulation valve ring  126  may be in the second position during operation of modulation control valve assembly  132  in the second mode. The second position may include valve portion  142  of modulation valve ring  126  being displaced from end plate  84  and opening first and second modulation ports  112 ,  114 . Modulation valve ring  126  may abut retaining ring  130  when in the second position. 
         [0068]    Modulation valve ring  126  and modulation lift ring  128  may be forced in axial directions opposite one another during operation of modulation control valve assembly  132  in the second mode. More specifically, modulation valve ring  126  may be displaced axially away from end plate  84  and modulation lift ring  128  may be urged axially toward end plate  84 . Protrusions  177  of modulation lift ring  128  may abut end plate  84  and first and second modulation ports  112 ,  114  may be in fluid communication with suction pressure region  106  via radial flow passages  178  when modulation valve ring  126  is in the second position. 
         [0069]    An alternate capacity modulation assembly  228  is illustrated in  FIGS. 5 and 6 . Capacity modulation assembly  228  may be generally similar to capacity modulation assembly  28  and may be incorporated into compressor  10  as discussed below. Therefore, it is understood that the description of capacity modulation assembly  28  applies equally to capacity modulation assembly  228  with the exceptions noted below. Modulation valve ring  326  may include axially extending protrusions  330  in place of retaining ring  130  of capacity modulation assembly  28 . Protrusions  330  may be circumferentially spaced from one another, forming flow paths  331  therebetween. When modulation valve ring  326  is displaced from the first position ( FIG. 5 ) to the second position ( FIG. 6 ), protrusions  330  may abut seal assembly  220  to provide an axial stop for modulation valve ring  326 . 
         [0070]    An alternate capacity modulation assembly  1528  is illustrated in  FIGS. 28 and 29 . Capacity modulation assembly  1528  may be generally similar to capacity modulation assembly  28  and may be incorporated into compressor  10  as discussed below. Therefore, it is understood that the description of capacity modulation assembly  28  applies equally to capacity modulation assembly  1528  with the exceptions noted below. Modulation valve ring  1626  may include axially extending protrusions  1630  and modulation lift ring  1628  may include axially extending protrusions  1632 . Protrusions  1630  may extend axially beyond and radially inward relative to protrusions  1632 . When modulation valve ring  1626  is displaced from the first position ( FIG. 28 ) to the second position ( FIG. 29 ), protrusions  1630  may abut protrusions  1632  to provide an axial stop for modulation valve ring  1626 . 
         [0071]    An alternate non-orbiting scroll  470  and capacity modulation assembly  428  are illustrated in  FIGS. 7 and 8 . End plate  484  of non-orbiting scroll  470  may include a biasing passage  510 , first and second modulation ports  512 ,  514 , an annular recess  540 , and first and second passages  544 ,  546 . Biasing passage  510 , first and second modulation ports  512 ,  514 , and second passage  546  may each be in fluid communication with one of the intermediate compression pockets. Biasing passage  510  may be in fluid communication with one of the intermediate compression pockets operating at a higher pressure than ones of intermediate compression pockets in fluid communication with first and second modulation ports  512 ,  514 . In the arrangement shown in  FIGS. 7 and 8 , second passage  546  may be in communication with one of the intermediate compression pockets operating at a higher pressure than or equal to the intermediate compression pocket in communication with biasing passage  510 . 
         [0072]    Annular hub  488  may include first and second portions  516 ,  518  axially spaced from one another forming a stepped region  520  therebetween. First portion  516  may be located axially between second portion  518  and end plate  484  and may have an outer radial surface  522  defining a diameter (D 7 ) greater than or equal to a diameter (D 8 ) defined by an outer radial surface  524  of second portion  518 . 
         [0073]    Capacity modulation assembly  428  may include a modulation valve ring  526 , a modulation lift ring  528 , a retaining ring  530 , and a modulation control valve assembly  532 . Modulation valve ring  526  may include an axial leg  534  and a radial leg  536 . Radial leg  536  may include a first axial end surface  538  facing end plate  484  and defining a valve portion  542  and a second axial end surface  552  facing seal assembly  420 . An inner radial surface  548  of axial leg  534  may define a diameter (D 9 ) greater than a diameter (D 10 ) defined by an inner radial surface  550  of radial leg  536 . The diameters (D 7 , D 10 ) may be approximately equal to one another and first portion  516  of annular hub  488  may be sealingly engaged with radial leg  536  of modulation valve ring  526  via a seal  554  located radially therebetween. More specifically, seal  554  may include an o-ring seal and may be located within an annular recess  556  in inner radial surface  550  of modulation valve ring  526 . 
         [0074]    Modulation lift ring  528  may be located within annular recess  540  and may include an annular body defining inner and outer radial surfaces  558 ,  560 , and first and second axial end surfaces  559 ,  561 . Annular recess  540  may extend axially into second side  489  of end plate  484 . Inner and outer radial surfaces  558 ,  560  may be sealingly engaged with sidewalls  562 ,  564  of annular recess  540  via first and second seals  566 ,  568 . More specifically, first and second seals  566 ,  568  may include o-ring seals and may be located within annular recesses  570 ,  572  in inner and outer radial surfaces  558 ,  560  of modulation lift ring  528 . End plate  484  and modulation lift ring  528  may cooperate to define a modulation control chamber  574  between annular recess  540  and second axial end surface  561 . First passage  544  may be in fluid communication with modulation control chamber  574 . First axial end surface  559  may face modulation valve ring  526  and may include a series of protrusions  577  defining radial flow passages  578  therebetween. 
         [0075]    Seal assembly  420  may form a floating seal assembly and may be sealingly engaged with non-orbiting scroll  470  and modulation valve ring  526  to define an axial biasing chamber  580 . More specifically, seal assembly  420  may be sealingly engaged with outer radial surface  524  of annular hub  488  and inner radial surface  548  of modulation valve ring  526 . Axial biasing chamber  580  may be defined axially between an axial end surface  582  of seal assembly  420  and second axial end surface  552  of modulation valve ring  526  and by stepped region  520  of annular hub  488 . 
         [0076]    Retaining ring  530  may be axially fixed relative to non-orbiting scroll  470  and may be located within axial biasing chamber  580 . More specifically, retaining ring  530  may be located within a recess in first portion  516  of annular hub  488  axially between seal assembly  420  and modulation valve ring  526 . Retaining ring  530  may form an axial stop for modulation valve ring  526 . Modulation control valve assembly  532  may include a solenoid operated valve and may be in fluid communication with first and second passages  544 ,  546  in end plate  484  and suction pressure region  506 . 
         [0077]    With additional reference to  FIGS. 20 and 21 , during compressor operation, modulation control valve assembly  532  may be operated in first and second modes.  FIGS. 20 and 21  schematically illustrate operation of modulation control valve assembly  532 . In the first mode, seen in  FIGS. 7 and 20 , modulation control valve assembly  532  may provide fluid communication between modulation control chamber  574  and suction pressure region  506 . More specifically, modulation control valve assembly  532  may provide fluid communication between first passage  544  and suction pressure region  506  during operation in the first mode. In the second mode, seen in  FIGS. 8 and 21 , modulation control valve assembly  532  may provide fluid communication between modulation control chamber  574  and second passage  546 . 
         [0078]    In an alternate capacity modulation assembly  1228 , seen in  FIGS. 22 and 23 , a modulation control valve assembly  1332  may include first and second modulation control valves  1331 ,  1333 . Capacity modulation assembly  1228  may be incorporated into compressor  10  as discussed below. First modulation control valve  1331  may be in communication with suction pressure region  1306 , modulation control chamber  1374  and second modulation control valve  1333 . Second modulation control valve  1333  may be in communication with second passage  1346  (similar to second passage  546 ), modulation control chamber  1374  and first modulation control valve  1331 . Modulation control valve assembly  1332  may be operated in first and second modes. Similar to the capacity modulation assembly  428 , biasing chamber  1380  and first passage  1310  (similar to biasing passage  510 ) may be isolated from communication with modulation control valve assembly  1332  and modulation control chamber  1374  during both the first and second modes. 
         [0079]    In the first mode, seen in  FIG. 22 , first modulation control valve  1331  may be open, providing communication between modulation control chamber  1374  and suction pressure region  1306 , and second modulation control valve  1333  may be closed, isolating modulation control chamber  1374  from second passage  1346 . In the second mode, seen in  FIG. 23 , first modulation control valve  1331  may be closed, isolating modulation control chamber  1374  from suction pressure region  1306 , and second modulation control valve  1333  may be open, providing communication between modulation control chamber  1374  and second passage  1346 . 
         [0080]    An alternate capacity modulation assembly  1328  is shown in  FIGS. 24 and 25 . Capacity modulation assembly  1328  may be incorporated into compressor  10  as discussed below. In the arrangement of  FIGS. 24 and 25 , modulation control chamber  1474  may be in communication with second passage  1446  (similar to second passage  546 ) and modulation control valve assembly  1432 . Modulation control valve assembly  1432  may be in communication with modulation control chamber  1474  and suction pressure region  1406 . Modulation control valve assembly  1432  may be operated in first and second modes. Similar to capacity modulation assembly  428 , biasing chamber  1480  and first passage  1410  (similar to biasing passage  510 ) may be isolated from communication with modulation control valve assembly  1432  and modulation control chamber  1474  during both the first and second modes. 
         [0081]    In the first mode, seen in  FIG. 24 , modulation control valve assembly  1432  may be open, providing communication between modulation control chamber  1474  and suction pressure region  1406  via a third passage  1433 . Second passage  1446  may define a greater flow restriction than third passage  1433 . In the second mode, seen in  FIG. 25 , modulation control valve assembly  1432  may be closed, isolating modulation control chamber  1474  from communication with suction pressure region  1406 . 
         [0082]    Another capacity modulation assembly  1428  is shown in  FIGS. 26 and 27 . Capacity modulation assembly  1428  may be incorporated into compressor  10  as discussed below. In the arrangement of  FIGS. 26 and 27 , modulation control chamber  1574  may be in communication with suction pressure region  1506  via a third passage  1533 . Modulation control valve assembly  1532  may be in communication with modulation control chamber  1574  and second passage  1546  (similar to second passage  546 ). Modulation control valve assembly  1532  may be operated in first and second modes. Similar to capacity modulation assembly  428 , biasing chamber  1580  and first passage  1510  (similar to biasing passage  510 ) may be isolated form communication with modulation control valve assembly  1532  and modulation control chamber  1574  during both the first and second modes. 
         [0083]    In the first mode, seen in  FIG. 26 , modulation control valve assembly  1532  may be closed, isolating modulation control chamber  1574  from communication with a biasing pressure. In the second mode, seen in  FIG. 27 , modulation control valve assembly  1532  may be open, providing communication between modulation control chamber  1574  and a biasing pressure via second passage  1546 . Third passage  1533  may provide a greater flow restriction than second passage  1546 . 
         [0084]    Modulation valve ring  526  may define a first radial surface area (A 11 ) facing away from non-orbiting scroll  470  radially between inner radial surfaces  548 ,  550  of modulation valve ring  526  (A 11 =(π)(D 9   2 −D 10   2 )/4). Sidewalls  562 ,  564  may define inner and outer diameters (D 11 , D 12 ). Modulation lift ring  528  may define a second radial surface area (A 22 ) opposite first radial surface area (A 11 ) and facing non-orbiting scroll  70  radially between sidewalls  562 ,  564  of end plate  484  (A 22 =(π)(D 12   2 −D 11   2 )/4). First radial surface area (A 11 ) may be greater than second radial surface area (A 22 ). Modulation valve ring  526  may be displaced between first and second positions based on the pressure provided to modulation control chamber  574  by modulation control valve assembly  532 . Modulation lift ring  528  may displace modulation valve ring  526 , as discussed below. The arrangement shown in  FIGS. 7 and 8  generally provides for a narrower non-orbiting scroll  470  and capacity modulation assembly  428  arrangements. However, it is understood that alternate arrangements may exist where the second radial surface area (A 22 ) is greater than the first radial surface area (A 11 ), as in  FIGS. 2 and 3 . 
         [0085]    A second intermediate pressure (P i2 ) within axial biasing chamber  580  applied to first radial surface area (A 11 ) may provide a first axial force (F 11 ) urging modulation valve ring  526  axially toward non-orbiting scroll  470  during both the first and second modes. When modulation control valve assembly  532  is operated in the first mode, modulation valve ring  526  may be in the first position ( FIG. 7 ). In the first mode, suction pressure (P s ) within modulation control chamber  574  may provide a second axial force (F 22 ) opposite first axial force (F 11 ). Modulation lift ring  528  may apply second axial force (F 22 ) to modulation valve ring  526  to bias modulation valve ring  526  axially away from non-orbiting scroll  470 . First axial force (F 11 ) may be greater than second axial force (F 22 ). Therefore, modulation valve ring  526  may be in the first position during operation of modulation control valve assembly  532  in the first mode. The first position may include valve portion  542  of modulation valve ring  526  abutting end plate  484  and closing first and second modulation ports  512 ,  514 . 
         [0086]    When modulation control valve assembly  532  is operated in the second mode, modulation valve ring  526  may be in the second position ( FIG. 8 ). In the second mode, a third intermediate pressure (P i3 ) from the intermediate compression pocket in fluid communication with second passage  546  may provide a third axial force (F 33 ) opposite first axial force (F 11 ) urging modulation lift ring  528  axially toward modulation valve ring  526 . Modulation lift ring  528  may apply third axial force (F 33 ) to modulation valve ring  526  to bias modulation valve ring  526  axially away from non-orbiting scroll  470 . Third axial force (F 33 ) may be greater than first axial force (F 11 ) even when second radial surface area (A 22 ) is less than first radial surface area (A 11 ) since modulation control chamber  574  operates at a higher pressure than axial biasing chamber  580  during the second mode (P i3 &gt;P i2 ). Modulation control chamber  574  may operate at the same pressure as axial biasing chamber  580  and therefore A 22  may be greater than A 11 . Therefore, modulation valve ring  526  may be in the second position during operation of modulation control valve assembly  532  in the second mode. The second position may include valve portion  542  of modulation valve ring  526  being displaced from end plate  484  and opening first and second modulation ports  512 ,  514 . Modulation valve ring  526  may abut retaining ring  530  when in the second position. 
         [0087]    Modulation valve ring  526  and modulation lift ring  528  may be forced in the same axial direction during operation of modulation control valve assembly  532  in the second mode. More specifically, modulation valve ring  526  and modulation lift ring  528  may both be displaced axially away from end plate  484 . Protrusions  577  of modulation lift ring  528  may abut modulation valve ring  526  and first and second modulation ports  512 ,  514  may be in fluid communication with suction pressure region  506  via radial flow passages  578  when modulation valve ring  526  is in the second position. 
         [0088]    An alternate capacity modulation assembly  828  is illustrated in  FIGS. 9 and 10 . Capacity modulation assembly  828  may be generally similar to capacity modulation assembly  428 . Therefore, it is understood that the description of capacity modulation assembly  428  applies equally to capacity modulation assembly  828  with the exceptions noted below. Modulation valve ring  926  may include axially extending protrusions  930  in place of retaining ring  530  of capacity modulation assembly  428 . Protrusions  930  may be circumferentially spaced from one another, forming flow paths  931  therebetween. When modulation valve ring  926  is displaced from the first position ( FIG. 9 ) to the second position ( FIG. 10 ), protrusions  930  may abut seal assembly  820  to provide an axial stop for modulation valve ring  926 . 
         [0089]    In an alternate arrangement, seen in  FIG. 11 , non-orbiting scroll  670  may be used in compressor  10  in place of non-orbiting scroll  70  and capacity modulation assembly  28 . Non-orbiting scroll  670  may be similar to non-orbiting scroll  70 , with the exception of first and second modulation ports  112 ,  114 . Instead of capacity modulation assembly  28 , non-orbiting scroll  670  may have an outer hub  726  engaged therewith. More specifically, outer hub  726  may include an axial leg  734  and a radial leg  736 . 
         [0090]    Radial leg  736  may include a first axial end surface  738  facing end plate  784  and a second axial end surface  752  facing seal assembly  620 . First portion  716  of annular hub  688  may be sealingly engaged with radial leg  736  of outer hub  726  via a seal  754  located radially therebetween. More specifically, seal  754  may include an o-ring seal and may be located within an annular recess  756  in inner radial surface  750  of outer hub  726 . 
         [0091]    Seal assembly  620  may form a floating seal assembly and may be sealingly engaged with non-orbiting scroll  670  and outer hub  726  to define an axial biasing chamber  780 . More specifically, seal assembly  620  may be sealingly engaged with outer radial surface  724  of annular hub  688  and inner radial surface  748  of axial leg  734 . Axial biasing chamber  780  may be defined axially between an axial end surface  782  of seal assembly  620  and second axial end surface  752  of outer hub  726  and stepped portion  720  of annular hub  688 . Biasing passage  710  may extend through stepped region  720  of annular hub  688  to provide fluid communication between axial biasing chamber  780  and an intermediate compression pocket. 
         [0092]    Outer hub  726  may be press fit on non-orbiting scroll  670  and fixed thereto without the use of fasteners by the press-fit engagement, as well as by pressure within axial biasing chamber  780  acting on second axial end surface  752  during compressor operation. Therefore, a generally common non-orbiting scroll  70 ,  270 ,  470 ,  670  may be used for a variety of applications including compressors with and without capacity modulation assemblies or first and second modulation ports  112 ,  512 ,  114 ,  514  of non-orbiting scrolls  70 ,  270 ,  470 .